Methicillin-resistant Staphylococcus aureus
Overview
 
Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 responsible for several difficult-to-treat infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

s in humans. It is also called multidrug-resistant Staphylococcus aureus and oxacillin-resistant Staphylococcus aureus (ORSA). MRSA is any strain of Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...

 that has developed resistance
Antibiotic resistance
Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...

 to beta-lactam antibiotics, which include the penicillin
Penicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....

s (methicillin
Methicillin
Meticillin or methicillin is a narrow-spectrum beta-lactam antibiotic of the penicillin class. It should not be confused with the antibiotic metacycline.-History:Methicillin was developed by Beecham in 1959...

, dicloxacillin
Dicloxacillin
Dicloxacillin is a narrow-spectrum beta-lactam antibiotic of the penicillin class. It is used to treat infections caused by susceptible Gram-positive bacteria. It is active against beta-lactamase-producing organisms such as Staphylococcus aureus, which would otherwise be resistant to most...

, nafcillin, oxacillin
Oxacillin
Oxacillin sodium is a narrow spectrum beta-lactam antibiotic of the penicillin class.It was developed by Beecham.-Uses:...

, etc.) and the cephalosporin
Cephalosporin
The cephalosporins are a class of β-lactam antibiotics originally derived from Acremonium, which was previously known as "Cephalosporium".Together with cephamycins they constitute a subgroup of β-lactam antibiotics called cephems.-Medical use:...

s.
Discussions
Encyclopedia
Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 responsible for several difficult-to-treat infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

s in humans. It is also called multidrug-resistant Staphylococcus aureus and oxacillin-resistant Staphylococcus aureus (ORSA). MRSA is any strain of Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...

 that has developed resistance
Antibiotic resistance
Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...

 to beta-lactam antibiotics, which include the penicillin
Penicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....

s (methicillin
Methicillin
Meticillin or methicillin is a narrow-spectrum beta-lactam antibiotic of the penicillin class. It should not be confused with the antibiotic metacycline.-History:Methicillin was developed by Beecham in 1959...

, dicloxacillin
Dicloxacillin
Dicloxacillin is a narrow-spectrum beta-lactam antibiotic of the penicillin class. It is used to treat infections caused by susceptible Gram-positive bacteria. It is active against beta-lactamase-producing organisms such as Staphylococcus aureus, which would otherwise be resistant to most...

, nafcillin, oxacillin
Oxacillin
Oxacillin sodium is a narrow spectrum beta-lactam antibiotic of the penicillin class.It was developed by Beecham.-Uses:...

, etc.) and the cephalosporin
Cephalosporin
The cephalosporins are a class of β-lactam antibiotics originally derived from Acremonium, which was previously known as "Cephalosporium".Together with cephamycins they constitute a subgroup of β-lactam antibiotics called cephems.-Medical use:...

s. The development of such resistance does not cause the organism to be more intrinsically virulent than strains of Staphylococcus aureus that have no antibiotic resistance, but resistance does make MRSA infection more difficult to treat with standard types of antibiotics and thus more dangerous.

MRSA is especially troublesome in hospitals and nursing homes, where patients with open wounds, invasive devices, and weakened immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

s are at greater risk of infection
Nosocomial infection
A nosocomial infection , also known as a hospital-acquired infection or HAI, is an infection whose development is favoured by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff...

 than the general public.

Signs and symptoms

S. aureus most commonly colonizes the anterior nares
Anterior nares
- Common Infections :Commonly infected by Staphylococcus aureus which may contribute to dermatitic skin lesions in patients with atopic dermatitis . The anterior nares can act as a colonizing point from which the infection can spread to other areas...

 (the nostrils). The rest of the respiratory tract
Respiratory tract
In humans the respiratory tract is the part of the anatomy involved with the process of respiration.The respiratory tract is divided into 3 segments:*Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx...

, open wounds, intravenous catheter
Catheter
In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...

s, and the urinary tract are also potential sites for infection. Healthy individuals may carry MRSA asymptomatically for periods ranging from a few weeks to many years. Patients with compromised
Immunodeficiency
Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...

 immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

s are at a significantly greater risk of symptomatic secondary infection.

In most patients, MRSA can be detected by swabbing the nostrils and isolating the bacteria found inside. Combined with extra sanitary measures for those in contact with infected patients, screening patients admitted to hospitals has been found to be effective in minimizing the spread of MRSA in hospitals in the United States, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

, Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

, and the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

.

MRSA may progress substantially within 24–48 hours of initial topical symptoms. After 72 hours, MRSA can take hold in human tissues and eventually become resistant to treatment. The initial presentation of MRSA is small red bumps that resemble pimples, spider bites, or boils; they may be accompanied by fever and, occasionally, rashes. Within a few days, the bumps become larger and more painful; they eventually open into deep, pus-filled boils. About 75 percent of community-associated (CA-) MRSA infections are localized to skin and soft tissue and usually can be treated effectively. But some CA-MRSA strains display enhanced virulence
Virulence
Virulence is by MeSH definition the degree of pathogenicity within a group or species of parasites as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenicity of an organism - its ability to cause disease - is determined by its...

, spreading more rapidly and causing illness much more severe than traditional healthcare-associated (HA-) MRSA infections, and they can affect vital organs and lead to widespread infection (sepsis
Sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...

), toxic shock syndrome
Toxic shock syndrome
Toxic shock syndrome is a potentially fatal illness caused by a bacterial toxin. Different bacterial toxins may cause toxic shock syndrome, depending on the situation. The causative bacteria include Staphylococcus aureus and Streptococcus pyogenes...

, and necrotizing ("flesh-eating") pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...

. This is thought to be due to toxins carried by CA-MRSA strains, such as PVL
Panton-Valentine leukocidin
Panton-Valentine leukocidin is a cytotoxin—one of the β-pore-forming toxins. The presence of PVL is associated with increased virulence of certain strains of Staphylococcus aureus...

 and PSM
Phenol-soluble modulin
Phenol-soluble modulins are a family of protein toxins that are soluble in phenols, that are produced by CA-MRSA, and which are thought to be a possible cause of severe infections.Non-methicillin resistant bacteria were not found to produce these toxins...

, though PVL was recently found to not be a factor in a study by the National Institute of Allergy and Infectious Diseases
National Institute of Allergy and Infectious Diseases
The National Institute of Allergy and Infectious Diseases is one of the 27 institutes and centers that make up the National Institutes of Health , an agency of the United States Department of Health and Human Services...

 (NIAID) at the NIH. It is not known why some healthy people develop CA-MRSA skin infections that are treatable while others infected with the same strain develop severe infections or die.

The most common manifestations of CA-MRSA are skin infections, such as necrotizing fasciitis
Necrotizing fasciitis
Necrotizing fasciitis , commonly known as flesh-eating disease or Flesh-eating bacteria syndrome, is a rare infection of the deeper layers of skin and subcutaneous tissues, easily spreading across the fascial plane within the subcutaneous tissue.Necrotizing fasciitis is a quickly progressing and...

 and pyomyositis
Pyomyositis
Pyomyositis, also known as tropical pyomyositis or myositis tropicans, is a bacterial infection of the skeletal muscles which results in a pus-filled abscess. Pyomyositis is most common in tropical areas but can also occur in temperate zones....

 (most commonly found in the tropics), necrotizing pneumonia, infective endocarditis
Infective endocarditis
Infective endocarditis is a form of endocarditis, or inflammation, of the inner tissue of the heart, such as its valves, caused by infectious agents. The agents are usually bacterial, but other organisms can also be responsible....

 (which affects the valves of the heart), and bone and joint infections. CA-MRSA often results in abscess formation that requires incision and drainage. Before the spread of MRSA into the community, abscesses were not considered contagious, because it was assumed that infection required violation of skin integrity and the introduction of staphylococci from normal skin colonization. However, newly emerging CA-MRSA is transmissible (similar, but with very important differences) from Hospital-Associated MRSA. CA-MRSA is less likely than other forms of MRSA to cause cellulitis
Cellulitis
Cellulitis is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin. Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken: cracks in the skin, cuts, blisters,...

.

Risk factors

Some of the populations at risk:
  • People with weak immune systems (people living with HIV
    HIV
    Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

    /AIDS
    AIDS
    Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...

    , people living with lupus, cancer
    Cancer
    Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

     patients, transplant recipients, severe asthma
    Asthma
    Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

    tics, etc.)
  • Diabetics
  • Intravenous drug users
  • Users of quinolone
    Quinolone
    The quinolones are a family of synthetic broad-spectrum antibiotics. The term quinolone refers to potent synthetic chemotherapeutic antibacterials....

     antibiotics
  • Young children
  • The elderly
  • College students living in dormitories
  • People staying or working in a health care facility for an extended period of time
  • People who spend time in coastal waters where MRSA is present, such as some beaches in Florida
    Florida
    Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

     and the west coast of the United States
    West Coast of the United States
    West Coast or Pacific Coast are terms for the westernmost coastal states of the United States. The term most often refers to the states of California, Oregon, and Washington. Although not part of the contiguous United States, Alaska and Hawaii do border the Pacific Ocean but can't be included in...

  • People who spend time in confined spaces with other people, including prison
    Prison
    A prison is a place in which people are physically confined and, usually, deprived of a range of personal freedoms. Imprisonment or incarceration is a legal penalty that may be imposed by the state for the commission of a crime...

     inmates, military recruits in basic training
    Recruit training
    Recruit training, more commonly known as Basic Training and colloquially called Boot Camp, is the initial indoctrination and instruction given to new military personnel, enlisted and officer...

    , and individuals who spend considerable time in changeroom
    Changeroom
    A changing room, locker room, dressing room or changeroom is a room or area designated for changing one's clothes...

    s or gym
    Gym
    The word γυμνάσιον was used in Ancient Greece, that mean a locality for both physical and intellectual education of young men...

    s.

Hospital patients

Many MRSA infections occur in hospitals and healthcare facilities, with a higher incidence rate in nursing homes or long-term care facilities. Rates of MRSA infection are also increased in hospitalised patients who are treated with quinolones. Healthcare provider-to-patient transfer is common, especially when healthcare providers move from patient to patient without performing necessary hand-washing techniques between patients.

Prison inmates

In confined environments such as prisons, with continual admission of new members who may typically be in poor health and adopt poor hygiene practices, there have been a number of challenges reported first in the U.S. and then in Canada. The earliest reports were made by the CDC in state prisons. Subsequently reports of a massive rise in skin and soft tissue infections were reported by the CDC in the Los Angeles County Jail system in 2001, and this has continued. Pan et al. reported on the changing epidemiology of MRSA skin infection in the San Francisco County Jail, noting the MRSA accounted for more than 70% of S. aureus infection in the jail by 2002. Lowy and colleagues reported on frequent MRSA skin infections in New York State Prisons. Two reports on inmates in Maryland have demonstrated frequent colonization with MRSA.

In the news media hundreds of reports of MRSA outbreaks in prisons appeared between 2000 and 2008. For example, in February 2008, The Tulsa County Jail in the U.S. State of Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...

 started treating an average of twelve Staphylococcus cases per month. A report on skin and soft tissue infections in the Cook County Jail in Chicago in 2004–05 demonstrated that MRSA was the most common cause of these infections among cultured lesions and furthermore that few risk factors were more strongly associated with MRSA infections than infections caused by methicillin-susceptible S. aureus. In response to these and many other reports on MRSA infections among incarcerated and recently incarcerated persons, the Federal Bureau of Prisons has released guidelines for the management and control of the infections although few studies provide an evidence base for these guidelines.

People in contact with live food-producing animals

Cases of MRSA have increased in livestock animals. CC398 is a new clone of MRSA that has emerged in animals and is found in intensively reared production animals (primarily pigs, but also cattle and poultry), where it can be transmitted to humans. Although being dangerous to humans CC398 is often asymptomatic in food-producing animals.

A 2011 study reported 47% of the meat and poultry sold in surveyed U.S. grocery stores was contaminated with S. aureus and, of those, 52%—or 24.4% of the total—were resistant to at least three classes of antibiotics. "Now we need to determine what this means in terms of risk to the consumer," said Dr. Keim, a co-author of the paper.

Athletes

In the United States, there have been increasing numbers of reports of outbreaks of MRSA colonization and infection through skin contact in locker rooms
Changeroom
A changing room, locker room, dressing room or changeroom is a room or area designated for changing one's clothes...

 and gym
Gym
The word γυμνάσιον was used in Ancient Greece, that mean a locality for both physical and intellectual education of young men...

s, even among healthy populations. A study published in the New England Journal of Medicine linked MRSA to the abrasions caused by artificial turf. Three studies by the Texas State Department of Health found that the infection rate among football players was 16 times the national average. In October 2006, a high school football player was temporarily paralyzed from MRSA-infected turf burns. His infection returned in January 2007 and required three surgeries to remove infected tissue, as well as three weeks of hospital stay. MRSA has also been found in the public school systems throughout the country.

Children

MRSA is also becoming a problem in pediatric settings, including hospital nurseries. A 2007 study found that 4.6% of patients in U.S. health care facilities were infected or colonized with MRSA.

Diagnosis

Diagnostic microbiology laboratories and reference laboratories are key for identifying outbreaks of MRSA. New rapid techniques for the identification and characterization of MRSA have been developed. This notwithstanding, the bacterium generally must be cultured via blood, urine, sputum
Sputum
Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....

, or other body fluid cultures, and grown up in the lab in sufficient numbers to perform these confirmatory tests first, so there is no quick and easy method to diagnose a MRSA infection, therefore initial treatment is often based upon 'strong suspicion' by the treating physician, since any delay in treating this type of infection can have fatal consequences. These techniques include Real-time PCR and Quantitative PCR and are increasingly being employed in clinical laboratories for the rapid detection and identification of MRSA strains.

Another common laboratory test is a rapid latex agglutination
Agglutination (biology)
Agglutination is the clumping of particles. The word agglutination comes from the Latin agglutinare, meaning "to glue."This occurs in biology in three main examples:...

 test that detects the PBP2a protein. PBP2a is a variant penicillin-binding protein that imparts the ability of S. aureus to be resistant to oxacillin.

Genetics

A defining characteristic of MRSA is its ability to thrive in the presence of penicillin
Penicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....

-like antibiotics, which normally prevent bacterial growth by inhibiting synthesis of cell-wall material. MRSA contains a gene, mecA
MecA gene
The mecA gene is a gene found in bacterial cells. The mecA gene allows a bacterium to be resistant to antibiotics such as methicillin, penicillin, erythromycin, tetracycline and other penicillin-like antibiotics....

, which stops β-lactam antibiotics from inactivating the enzymes (transpeptidase
Transpeptidase
A transpeptidase is a bacterial enzyme that cross-links the peptidoglycan chains to form rigid cell walls. This enzyme is also known by several other names including DD-peptidase, DD-transpeptidase, D-alanyl-D-alanine carboxypeptidase and serine-type D-Ala-D-Ala carboxypeptidase...

s) that are critical to cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...

 synthesis.

SCCmec

MRSA acquires mecA on a mobile genetic element called SCCmec
SCCmec
SCCmec, or staphylococcal cassette chromosome mec, is a mobile genetic element of Staphylococcus bacterial species. This genetic sequence includes the mecA gene coding for resistance to the antibiotic methicillin and is the only known way for Staphylococcus strains to spread the gene in the wild...

. SCCmec includes additional genes beyond mecA, including the cytolysin
Cytolysin
Cytolysin refers to the substance or antibody elaborated by microorganisms, plants or animals that is specifically toxic to individual cells, in many cases causing their dissolution through lysis. Cytolysins that have a specific action for certain cells are named accordingly...

 gene psm-mec which may suppress virulence in hospital-acquired MRSA strains.

Strains

In the UK, where MRSA is commonly called "Golden Staph", the most common strains of MRSA are EMRSA15 and EMRSA16. EMRSA16 is the best described epidemiologically: it originated in Kettering
Kettering
Kettering is a market town in the Borough of Kettering, Northamptonshire, England. It is situated about from London. Kettering is mainly situated on the west side of the River Ise, a tributary of the River Nene which meets at Wellingborough...

, England, and the full genomic sequence of this strain has been published. EMRSA16 has been found to be identical to the ST36:USA200 strain, which circulates in the United States, and to carry the SCCmec type II, enterotoxin A
Enterotoxin
An enterotoxin is a protein toxin released by a microorganism in the intestine. Enterotoxins are chromosomally encoded exotoxins that are produced and secreted from several bacterial organisms. They are often heat-stable, and are of low molecular weight and water-soluble...

 and toxic shock syndrome
Toxic shock syndrome
Toxic shock syndrome is a potentially fatal illness caused by a bacterial toxin. Different bacterial toxins may cause toxic shock syndrome, depending on the situation. The causative bacteria include Staphylococcus aureus and Streptococcus pyogenes...

 toxin 1 genes. Under the new international typing system, this strain is now called MRSA252. It is not entirely certain why this strain has become so successful, whereas previous strains have failed to persist. One explanation is the characteristic pattern of antibiotic susceptibility. Both the EMRSA15 and EMRSA16 strains are resistant to erythromycin
Erythromycin
Erythromycin is a macrolide antibiotic that has an antimicrobial spectrum similar to or slightly wider than that of penicillin, and is often used for people who have an allergy to penicillins. For respiratory tract infections, it has better coverage of atypical organisms, including mycoplasma and...

 and ciprofloxacin
Ciprofloxacin
Ciprofloxacin is a synthetic chemotherapeutic antibiotic of the fluoroquinolone drug class.It is a second-generation fluoroquinolone antibacterial. It kills bacteria by interfering with the enzymes that cause DNA to rewind after being copied, which stops synthesis of DNA and of...

. It is known that Staphylococcus aureus can survive intracellularly, for example in the nasal mucosa and in the tonsil tissue ,. Erythromycin and Ciprofloxacin are precisely the antibiotics that best penetrate intracellularly; it may be that these strains of S. aureus are therefore able to exploit an intracellular niche.

Community-acquired MRSA (CA-MRSA) is more easily treated, though more virulent, than hospital-acquired MRSA (HA-MRSA). CA-MRSA apparently did not evolve de novo
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

 in the community but represents a hybrid between MRSA that spread from the hospital environment and strains that were once easily treatable in the community. Most of the hybrid strains also acquired a factor that increases their virulence, resulting in the development of deep-tissue infections from minor scrapes and cuts, as well as many cases of fatal pneumonia.

In the United States, most cases of CA-MRSA are caused by a CC8 strain designated ST8:USA300
ST8:USA300
ST8:USA300 is a strain ofcommunity-associated MRSA that has emerged as a particularly antibiotic resistant epidemic that is responsible for rapidly progressive, fatal diseases including necrotizing pneumonia, severe sepsis and necrotizing fasciitis...

, which carries SCCmec type IV, Panton-Valentine leukocidin
Panton-Valentine leukocidin
Panton-Valentine leukocidin is a cytotoxin—one of the β-pore-forming toxins. The presence of PVL is associated with increased virulence of certain strains of Staphylococcus aureus...

, PSM-alpha
Phenol-soluble modulin
Phenol-soluble modulins are a family of protein toxins that are soluble in phenols, that are produced by CA-MRSA, and which are thought to be a possible cause of severe infections.Non-methicillin resistant bacteria were not found to produce these toxins...

 and enterotoxin
Enterotoxin
An enterotoxin is a protein toxin released by a microorganism in the intestine. Enterotoxins are chromosomally encoded exotoxins that are produced and secreted from several bacterial organisms. They are often heat-stable, and are of low molecular weight and water-soluble...

s Q and K, and ST1:USA400. Other community-acquired strains of MRSA are ST8:USA500 and ST59:USA1000. In many nations of the world, MRSA strains with different predominant genetic background types have come to predominate among CA-MRSA strains; USA300 easily tops the list in the U. S. and is becoming more common in Canada after its first appearance there in 2004. For example, in Australia ST93 strains are common, while in continental Europe ST80 strains predominate (Tristan et al., Emerging Infectious Diseases, 2006). In Taiwan, ST59 strains, some of which are resistant to many non-beta-lactam antibiotics, have arisen as common causes of skin and soft tissue infections in the community. In a remote region of Alaska, unlike most of the continental U. S., USA300 was found rarely in a study of MRSA strains from outbreaks in 1996 and 2000 as well as in surveillance from 2004–06 (David et al., Emerg Infect Dis 2008).

In June 2011, the discovery of a new strain of MRSA was announced by two separate teams of researchers in the UK. Its genetic make-up was reportedly more similar to strains found in animals, and testing kits designed to detect MRSA were unable to identify it.

Screening programs

Patient screening upon hospital admission, with nasal cultures, prevents the cohabitation of MRSA carriers with non-carriers, and exposure to infected surfaces. The test used (whether a rapid molecular method or traditional culture) is not as important as the implementation of active screening.
In the United States and Canada, the Centers for Disease Control and Prevention issued guidelines on October 19, 2006, citing the need for additional research, but declined to recommend such screening.

In some UK hospitals screening for MRSA is performed in every patient and all NHS surgical patients, except for minor surgeries, are previously checked for MRSA. There is no community screening in the UK however screening of individuals is offered by some private companies.

In a US cohort of 1300 healthy children, 2.4% carried MRSA in their nose.

Surface sanitizing

Alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

 has been proven to be an effective surface sanitizer against MRSA. Quaternary ammonium can be used in conjunction with alcohol to extend the longevity of the sanitizing action. The prevention of nosocomial infection
Nosocomial infection
A nosocomial infection , also known as a hospital-acquired infection or HAI, is an infection whose development is favoured by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff...

s involves routine and terminal cleaning
Terminal cleaning
Terminal Cleaning describes a cleaning method used in healthcare environments to control the spread of infections.- Justification :Nosocomial infections claim approximately 90,000 lives in the United States annually...

. Non-flammable Alcohol Vapor in Carbon Dioxide systems
NAV-CO2
Non-flammable Alcohol Vapor in Carbon Dioxide systems were developed in Japan in the 1990s to sanitize hospitals and ambulances. These systems were developed in response to a need for a safe, effective, and environmentally sound way of sanitizing without the use of toxic or corrosive chemicals...

 (NAV-CO2) do not corrode metals or plastics used in medical environments and do not contribute to antibacterial resistance.

In healthcare environments, MRSA can survive on surfaces and fabrics, including privacy curtains or garments worn by care providers. Complete surface sanitation is necessary to eliminate MRSA in areas where patients are recovering from invasive procedures. Testing patients for MRSA upon admission, isolating MRSA-positive patients, decolonization of MRSA-positive patients, and terminal cleaning
Terminal cleaning
Terminal Cleaning describes a cleaning method used in healthcare environments to control the spread of infections.- Justification :Nosocomial infections claim approximately 90,000 lives in the United States annually...

 of patients' rooms and all other clinical areas they occupy is the current best practice protocol for nosocomial MRSA.

Studies published from 2004-2007 reported hydrogen peroxide vapor could be used to decontaminate busy hospital rooms, despite taking significantly longer than traditional cleaning. One study noted rapid recontamination by MRSA following the hydrogen peroxide application

Also tested, in 2006, was a new type of surface cleaner, incorporating accelerated hydrogen peroxide, which was pronounced "a potential candidate" for use against the targeted microorganisms.

Hand washing

In September 2004, after a successful pilot scheme to tackle MRSA, the UK National Health Service
National Health Service
The National Health Service is the shared name of three of the four publicly funded healthcare systems in the United Kingdom. They provide a comprehensive range of health services, the vast majority of which are free at the point of use to residents of the United Kingdom...

 announced its Clean Your Hands campaign. Wards were required to ensure that alcohol-based hand rubs are placed near all beds so that staff can hand wash more regularly. It is thought that even if this cuts infection by no more than 1%, the plan will pay for itself many times over.

As with some other bacteria, MRSA is acquiring more resistance to some disinfectants and antiseptic
Antiseptic
Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction...

s. Although alcohol-based rubs remain somewhat effective, a more effective strategy is to wash hands with running water and an anti-microbial cleanser with persistent killing action, such as Chlorhexidine

A June 2008 report, centered on a survey by the Association for Professionals in Infection Control and Epidemiology, concluded that poor hygiene habits remain the principal barrier to significant reductions in the spread of MRSA.

Use of surgical respirator

The U.S. Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

 (FDA) announced on 8 April 2011 that it had cleared a novel type of N95 Surgical Respirator, the SpectraShield 9500, that kills methicillin-resistant Staphylococcus aureus, Streptococcus pyogenes
Streptococcus pyogenes
Streptococcus pyogenes is a spherical, Gram-positive bacterium that is the cause of group A streptococcal infections. S. pyogenes displays streptococcal group A antigen on its cell wall. S...

 and Haemophilus influenzae
Haemophilus influenzae
Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...

. This mask is manufactured by Nexera Medical Ltd. of Richmond, British Columbia The mask blocks at least 95% of small particles in a standardized test. The FDA clearance also included evaluation by the National Institute of Occupational Safety and Health.

Proper disposal of hospital gowns

Used paper hospital gowns are associated with MRSA hospital infections, which could be avoided by proper disposal.

Isolation

Current US guidance does not require workers in the general workplace
Workplace safety
Workplace safety & health is a category of management responsibility in places of employment.To ensure the safety and health of workers, managers establish a focus on safety that can include elements such as:* management leadership and commitment...

 (excluding medical facilities
Medical facility
A medical facility is, in general, any location at which medicine is practiced regularly. Medical facilities range from small clinics and doctor's offices to urgent care centers and large hospitals with elaborate emergency rooms and trauma centers. The number and quality of medical facilities in a...

) with MRSA infections to be routinely excluded from going to work. Therefore, unless directed by a health care provider, exclusion from work should be reserved for those with wound drainage that cannot be covered and contained with a clean, dry bandage and for those who cannot maintain good hygiene practices. Workers with active infections should be excluded from activities where skin-to-skin contact is likely to occur until their infections are healed. Health care workers should follow the
Centers for Disease Control and Prevention's Guidelines for Infection Control in Health Care Personnel.

To prevent the spread of staph or MRSA in the workplace, employers should ensure the availability of adequate facilities and supplies that encourage workers to practice good hygiene; that surface sanitizing in the workplace is followed; and that contaminated equipment are sanitized with Environmental Protection Agency (EPA)-registered disinfectants.

Restricting antibiotic use

Glycopeptides, cephalosporin
Cephalosporin
The cephalosporins are a class of β-lactam antibiotics originally derived from Acremonium, which was previously known as "Cephalosporium".Together with cephamycins they constitute a subgroup of β-lactam antibiotics called cephems.-Medical use:...

s and in particular quinolones are associated with an increased risk of colonisation of MRSA. Reducing use of antibiotic classes that promote MRSA colonisation, especially fluoroquinolones, is recommended in current guidelines.

Public health considerations

Mathematical models describe one way in which a loss of infection control can occur after measures for screening and isolation seem to be effective for years, as happened in the UK. In the "search and destroy" strategy that was employed by all UK hospitals until the mid-1990s, all patients with MRSA were immediately isolated, and all staff were screened for MRSA and were prevented from working until they had completed a course of eradication therapy that was proven to work. Loss of control occurs because colonised patients are discharged back into the community and then readmitted; when the number of colonised patients in the community reaches a certain threshold, the "search and destroy" strategy is overwhelmed. One of the few countries not to have been overwhelmed by MRSA is the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

: An important part of the success of the Dutch strategy may have been to attempt eradication of carriage upon discharge from hospital.

The Centers for Disease Control and Prevention (CDC) estimated that about 1.7 million nosocomial infections occurred in the United States in 2002, with 99,000 associated deaths. The estimated incidence is 4.5 nosocomial infections per 100 admissions, with direct costs (at 2004 prices) ranging from $10,500 (£5300, €8000 at 2006 rates) per case (for bloodstream, urinary tract, or respiratory infections in immunocompetent patients) to $111,000 (£57,000, €85,000) per case for antibiotic-resistant infections in the bloodstream in patients with transplants. With these numbers, conservative estimates of the total direct costs of nosocomial infections are above $17 billion. The reduction of such infections forms an important component of efforts to improve healthcare safety. (BMJ 2007) MRSA alone was associated with 8% of nosocomial infections reported to the CDC National Healthcare Safety Network from January 2006 to October 2007.

This problem is not unique to one country; the British National Audit Office estimated that the incidence of nosocomial infections in Europe ranges from 4% to 10% of all hospital admissions. As of early 2005, the number of deaths in the United Kingdom attributed to MRSA has been estimated by various sources to lie in the area of 3,000 per year. Staphylococcus bacteria account for almost half of all UK hospital infections. The issue of MRSA infections in hospitals has recently been a major political issue in the UK, playing a significant role in the debates over health policy in the United Kingdom general election held in 2005
United Kingdom general election, 2005
The United Kingdom general election of 2005 was held on Thursday, 5 May 2005 to elect 646 members to the British House of Commons. The Labour Party under Tony Blair won its third consecutive victory, but with a majority of 66, reduced from 160....

.

On January 6, 2008, half of 64 non-Chinese cases of MRSA infections in Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...

 in 2007 were Filipino
Filipino people
The Filipino people or Filipinos are an Austronesian ethnic group native to the islands of the Philippines. There are about 92 million Filipinos in the Philippines, and about 11 million living outside the Philippines ....

 domestic helpers. Ho Pak-leung, professor of microbiology at the University of Hong Kong, traced the cause to high use of antibiotics. In 2007, there were 166 community cases in Hong Kong compared with 8,000 hospital-acquired MRSA case (155 recorded cases—91 involved Chinese locals, 33 Filipinos, 5 each for Americans and Indians, and 2 each from Nepal, Australia, Denmark and England).

Worldwide, an estimated 2 billion people carry some form of S. aureus; of these, up to 53 million (2.7% of carriers) are thought to carry MRSA. In the United States, 95 million carry S. aureus in their noses; of these, 2.5 million (2.6% of carriers) carry MRSA. A population review conducted in three U.S. communities showed the annual incidence of CA-MRSA during 2001–2002 to be 18–25.7/100,000; most CA-MRSA isolates were associated with clinically relevant infections, and 23% of patients required hospitalization.

One possible contribution to the increased spread of MRSA infections comes from the use of antibiotics in intensive pig farming
Intensive pig farming
Intensive piggeries are a type of factory farm ' specialized in the raising of domestic pigs up to slaughter weight...

. A 2008 study in Canada found MRSA in 10% of tested pork chops and ground pork; a U.S. study in the same year found MRSA in the noses of 70% of the tested farm pigs and in 45% of the tested pig farm workers. There have also been anecdotal reports of increased MRSA infection rates in rural communities with pig farms.

Healthcare facilities with high bed occupancy rates, high levels of temporary nursing staff, or low cleanliness scores no longer have significantly higher MRSA rates. Simple tabular evidence helps provide a clear picture of these changes, showing, for instance, that hospitals with occupancy over 90% had, in 2006–2007, MRSA rates little above those in hospitals with occupancy below 85%, in contrast to the period 2001–2004. In one sense, the disappearance of these relationships is puzzling. Reporters now blame IV cannula and catheters for spreading MRSA in hospitals. (Hospital organisation and speciality mix, 2008)

Decolonization

Care should be taken when trying to drain boils, as disruption of surrounding tissue can lead to larger infections, or even infection of the blood stream (often with fatal consequences). Any drainage should be disposed of very carefully. After the drainage of boils or other treatment for MRSA, patients can shower at home using chlorhexidine (Hibiclens) or hexachlorophene
Hexachlorophene
Hexachlorophene, also known as Nabac, is a disinfectant. The compound occurs as a white to light-tan crystalline powder, which either is odorless or produces a slightly phenolic odor. In medicine, hexachlorophene is very useful as a topical anti-infective, anti-bacterial agent, often used in soaps...

 (Phisohex) antiseptic soap (available over-the-counter at many pharmacies) from head to toe. Alternatively, a dilute bleach bath can be taken at a concentration of 1/2 cup bleach per 1/4-full bathtub of water. Care should be taken to use a clean towel, and to ensure that nasal discharge (i.e. snot) doesn't infect the towel (see below).

All infectious lesions should be kept covered with a dressing (band-aids etc.). Mupirocin
Mupirocin
Mupirocin is an antibiotic originally isolated from Pseudomonas fluorescens NCIMB 10586, developed by Beecham....

 (Bactroban) 2% ointment can be effective at reducing the size of lesions. A secondary covering of clothing is preferred.

The nose is a common refuge for MRSA, however a test swab can be taken of the nose to indicate whether MRSA is present. Mupirocin
Mupirocin
Mupirocin is an antibiotic originally isolated from Pseudomonas fluorescens NCIMB 10586, developed by Beecham....

 (Bactroban) 2% ointment can be applied inside each nostril twice daily for 7 days, using a cotton-tipped swab. However, care should be taken so that the swab doesn't penetrate into the sinus. Household members are recommended to follow the same decolonization protocol. After treatment, the nose should be swabbed again to ensure that the treatment was effective. If not, the process should be repeated.

Toilet seats are a common vector for infection, therefore the seat can be wiped clean before and/or after each use. Door handles, faucets, light switches (with care!), etc. can be disinfected daily (or regularly; use of disinfectant wipes is recommended). Spray disinfectants can be used on upholstery. Carpets can be washed with disinfectant, and hardwood floors can be scrubbed with diluted tea tree oil (e.g. Melaleuca). Laundry soap containing tea tree oil may be effective at decontaminating clothing and bedding, especially if hot water and heavy soil cycles are used, however tea tree oil may cause a rash which MRSA can re-colonize. Alcohol-based sanitizers can be placed near bedsides, near sitting areas, in vehicles etc. to encourage their use.

Doctors may also prescribe antibiotics such as clindamycin
Clindamycin
Clindamycin rINN is a lincosamide antibiotic. It is usually used to treat infections with anaerobic bacteria but can also be used to treat some protozoal diseases, such as malaria...

, doxycycline
Doxycycline
Doxycycline INN is a member of the tetracycline antibiotics group, and is commonly used to treat a variety of infections. Doxycycline is a semisynthetic tetracycline invented and clinically developed in the early 1960s by Pfizer Inc. and marketed under the brand name Vibramycin. Vibramycin...

 or trimethoprim/sulfamethoxazole. Although very few studies have shown that using more antibiotics actually has the effect of preventing recurrent MRSA skin infections, anecdotal evidence and common sense demonstrate that antibiotics reduce the size of any infections and therefore reduce the ability of MRSA to spread.

Treatment

Both CA-MRSA and HA-MRSA are resistant to traditional anti-staphylococcal beta-lactam antibiotic
Beta-lactam antibiotic
β-Lactam antibiotics are a broad class of antibiotics, consisting of all antibiotic agents that contains a β-lactam nucleus in its molecular structure. This includes penicillin derivatives , cephalosporins , monobactams, and carbapenems...

s, such as cephalexin. CA-MRSA has a greater spectrum of antimicrobial susceptibility, including to sulfa drugs
Sulfonamide (medicine)
Sulfonamide or sulphonamide is the basis of several groups of drugs. The original antibacterial sulfonamides are synthetic antimicrobial agents that contain the sulfonamide group. Some sulfonamides are also devoid of antibacterial activity, e.g., the anticonvulsant sultiame...

 (like co-trimoxazole
Co-trimoxazole
Trimethoprim/sulfamethoxazole or co-trimoxazole is a sulfonamide antibiotic combination of trimethoprim and sulfamethoxazole, in the ratio of 1 to 5, used in the treatment of a variety of bacterial infections.The name co-trimoxazole is the British Approved Name, and has been marketed worldwide...

/trimethoprim-sulfamethoxazole), tetracyclines
Tetracycline antibiotics
Tetracyclines are a group of broad-spectrum antibiotics whose general usefulness has been reduced with the onset of bacterial resistance. Despite this, they remain the treatment of choice for some specific indications....

 (like doxycycline
Doxycycline
Doxycycline INN is a member of the tetracycline antibiotics group, and is commonly used to treat a variety of infections. Doxycycline is a semisynthetic tetracycline invented and clinically developed in the early 1960s by Pfizer Inc. and marketed under the brand name Vibramycin. Vibramycin...

 and minocycline
Minocycline
Minocycline is a broad-spectrum tetracycline antibiotic, and has a broader spectrum than the other members of the group. It is a bacteriostatic antibiotic, classified as a long-acting type...

) and clindamycin
Clindamycin
Clindamycin rINN is a lincosamide antibiotic. It is usually used to treat infections with anaerobic bacteria but can also be used to treat some protozoal diseases, such as malaria...

, but the drug of choice for treating CA-MRSA has is now believed to be Vancomycin
Vancomycin
Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...

, according to a Henry Ford Hospital Study. The study was presented on October 23, 2010, at the 48th annual meeting of the Infectious Diseases Society of America in Vancouver.
HA-MRSA is resistant even to these antibiotics and often is susceptible only to vancomycin
Vancomycin
Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...

. Newer drugs, such as linezolid
Linezolid
Linezolid is a synthetic antibiotic used for the treatment of serious infections caused by Gram-positive bacteria that are resistant to several other antibiotics...

 (belonging to the newer oxazolidinones class) and daptomycin
Daptomycin
Daptomycin is a novel lipopeptide antibiotic used in the treatment of certain infections caused by Gram-positive organisms. It is a naturally occurring compound found in the soil saprotroph Streptomyces roseosporus. Its distinct mechanism of action means that it may be useful in treating infections...

, are effective against both CA-MRSA and HA-MRSA.

Vancomycin
Vancomycin
Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...

 and teicoplanin
Teicoplanin
Teicoplanin is an antibiotic used in the prophylaxis and treatment of serious infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. It is a glycopeptide antibiotic extracted from Actinoplanes teichomyceticus, with a similar...

 are glycopeptide antibiotics used to treat MRSA infections.
Teicoplanin
Teicoplanin
Teicoplanin is an antibiotic used in the prophylaxis and treatment of serious infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. It is a glycopeptide antibiotic extracted from Actinoplanes teichomyceticus, with a similar...

 is a structural congener of vancomycin
Vancomycin
Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...

 that has a similar activity spectrum but a longer half-life.
Because the oral absorption of vancomycin
Vancomycin
Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...

 and Teicoplanin
Teicoplanin
Teicoplanin is an antibiotic used in the prophylaxis and treatment of serious infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. It is a glycopeptide antibiotic extracted from Actinoplanes teichomyceticus, with a similar...

 is very low, these agents must be administered intravenously to control systemic infections. Drugs are administered via a Peripherally inserted central catheter, or a Picc Line, which is inserted by radiologists, doctors, physician assistants (in the U.S.), radiologist assistants (in the U.S.), or specially trained certified registered nurses. Treatment of MRSA infection with vancomycin
Vancomycin
Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...

 can be complicated, due to its inconvenient route of administration. Moreover, many clinicians believe that the efficacy of vancomycin
Vancomycin
Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...

 against MRSA is inferior to that of anti-staphylococcal beta-lactam antibiotic
Beta-lactam antibiotic
β-Lactam antibiotics are a broad class of antibiotics, consisting of all antibiotic agents that contains a β-lactam nucleus in its molecular structure. This includes penicillin derivatives , cephalosporins , monobactams, and carbapenems...

s against methicillin-susceptible Staphylococcus aureus (MSSA).

Several newly discovered strains of MRSA show antibiotic resistance
Antibiotic resistance
Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...

 even to vancomycin
Vancomycin
Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...

 and teicoplanin
Teicoplanin
Teicoplanin is an antibiotic used in the prophylaxis and treatment of serious infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. It is a glycopeptide antibiotic extracted from Actinoplanes teichomyceticus, with a similar...

. These new evolutions of the MRSA bacterium have been dubbed Vancomycin intermediate-resistant Staphylococcus aureus (VISA)
Vancomycin-resistant Staphylococcus aureus
Vancomycin-resistant Staphylococcus aureus refers to strains of Staphylococcus aureus that have become resistant to the glycopeptide antibiotic vancomycin. With the increase of staphylococcal resistance to methicillin, vancomycin is often a treatment of choice in infections with...

.
Linezolid
Linezolid
Linezolid is a synthetic antibiotic used for the treatment of serious infections caused by Gram-positive bacteria that are resistant to several other antibiotics...

, quinupristin/dalfopristin
Quinupristin/dalfopristin
Quinupristin/dalfopristin is a combination of two antibiotics used to treat infections by staphylococci and by vancomycin-resistant Enterococcus faecium....

(synercid), daptomycin
Daptomycin
Daptomycin is a novel lipopeptide antibiotic used in the treatment of certain infections caused by Gram-positive organisms. It is a naturally occurring compound found in the soil saprotroph Streptomyces roseosporus. Its distinct mechanism of action means that it may be useful in treating infections...

, and tigecycline
Tigecycline
Tigecycline is a glycylcycline antibiotic developed by Francis Tally and marketed by Wyeth under the brand name Tygacil. It was given a U.S. Food and Drug Administration fast-track approval and was approved on June 17, 2005...

 are used to treat more severe infections that do not respond to glycopeptides such as vancomycin
Vancomycin
Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...

.

There have been claims that bacteriophage
Bacteriophage
A bacteriophage is any one of a number of viruses that infect bacteria. They do this by injecting genetic material, which they carry enclosed in an outer protein capsid...

 can be used to cure MRSA.

The psychedelic mushroom Psilocybe semilanceata has been shown to strongly inhibit the growth of Staphylococcus aureus.

Initial studies at the University of East London have demonstrated that allicin (a compound found in garlic) exhibits a strong antimicrobial response to the bacteria, indicating that it may one day lead to more effective treatments.

A report released in 2010 details the efficacy of the active ingredients of a new composite dressing (hydrogen peroxide, tobramycin, chlorhexidine digluconate, chlorhexidine gluconate, levofloxacin, and silver) against MRSA.

A 1990 study tested MRSA isolates obtained from veterans and found they could be killed by several substances, including bacitracin, nitrofurantoin, hydrogen peroxide, novobiocin, netilmicin and vancomycin. The study went on to conclude that netilmicin might be useful as an alternative to intravenous vancomycin, and suggested that topical applications of hydrogen peroxide may be useful to reduce MRSA on skin and some mucous membranes.

US and UK

MRSA was discovered in 1961 in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

. It made its first major appearance in the United States in 1981 among intravenous drug users. MRSA is often referred to in the press as a "superbug
Antibiotic resistance
Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...

".
The number of MRSA infections in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 has been increasing significantly. A 2007 report in Emerging Infectious Diseases
Emerging Infectious Diseases
Emerging Infectious Diseases is a peer-reviewed medical journal published by the Centers for Disease Control and Prevention. It is in the public domain and is published monthly by the CDC's National Center for Emerging and Zoonotic Infectious Diseases...

, a publication of the Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...

 (CDC), estimated the number of MRSA infections in hospitals doubled nationwide, from approximately 127,000 in 1999 to 278,000 in 2005, while at the same time annual deaths increased from 11,000 to more than 17,000. Another study led by the CDC
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...

 and published in the October 17, 2007 issue of the Journal of the American Medical Association
Journal of the American Medical Association
The Journal of the American Medical Association is a weekly, peer-reviewed, medical journal, published by the American Medical Association. Beginning in July 2011, the editor in chief will be Howard C. Bauchner, vice chairman of pediatrics at Boston University’s School of Medicine, replacing ...

 estimated that MRSA was responsible for 94,360 serious infections and associated with 18,650 hospital stay-related deaths in the United States in 2005. These figures suggest that MRSA infections are responsible for more deaths in the U.S. each year than AIDS
AIDS
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...

.

The Office for National Statistics
Office for National Statistics
The Office for National Statistics is the executive office of the UK Statistics Authority, a non-ministerial department which reports directly to the Parliament of the United Kingdom.- Overview :...

 reported 1,629 MRSA-related deaths in England and Wales during 2005, indicating a MRSA-related mortality rate half the rate of that in the United States for 2005, even though the figures from the British source were explained to be high because of "improved levels of reporting, possibly brought about by the continued high public profile of the disease" during the time of the 2005 United Kingdom General Election
United Kingdom general election, 2005
The United Kingdom general election of 2005 was held on Thursday, 5 May 2005 to elect 646 members to the British House of Commons. The Labour Party under Tony Blair won its third consecutive victory, but with a majority of 66, reduced from 160....

. MRSA is thought to have caused 1,652 deaths in 2006 in UK up from 51 in 1993.

It has been argued that the observed increased mortality among MRSA-infected patients may be the result of the increased underlying morbidity of these patients. Several studies, however, including one by Blot and colleagues, that have adjusted for underlying disease still found MRSA bacteremia to have a higher attributable mortality than methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia.

While the statistics suggest a national epidemic growing out of control, it has been difficult to quantify the degree of morbidity and mortality
Mortality rate
Mortality rate is a measure of the number of deaths in a population, scaled to the size of that population, per unit time...

 attributable to MRSA. A population-based study of the incidence of MRSA infections in San Francisco during 2004–05 demonstrated that nearly 1 in 300 residents suffered from such an infection in the course of a year and that greater than 85% of these infections occurred outside of the healthcare setting. A 2004 study showed that patients in the United States with S. aureus infection had, on average, three times the length of hospital stay (14.3 vs. 4.5 days), incurred three times the total cost ($48,824 vs $14,141), and experienced five times the risk of in-hospital death (11.2% vs 2.3%) than patients without this infection. In a meta-analysis of 31 studies, Cosgrove et al., concluded that MRSA bacteremia is associated with increased mortality as compared with MSSA bacteremia (odds ratio = 1.93; 95% CI =
1.93±0.39). In addition, Wyllie et al. report a death rate of 34% within 30 days among patients infected with MRSA, a rate similar to the death rate of 27% seen among MSSA-infected patients.

MRSA is sometimes sub-categorised as community-acquired MRSA (CA-MRSA) or healthcare-associated MRSA (HA-MRSA), although the distinction is complex. Some researchers have defined CA-MRSA by the characteristics of patients whom it infects, while others define it by the gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

tic characteristics of the bacteria themselves.

Worldwide

The first reported cases of CA-MRSA began to appear in the mid-1990s in Australia, New Zealand, the United States, the United Kingdom, France, Finland, Canada and Samoa, and were notable because they involved people who had not been exposed to a healthcare setting.

In 1997, four fatal cases were reported involving children from Minnesota and North Dakota. Over the next several years, it became clear that CA-MRSA infections were caused by strains of MRSA that differed from the older and better studied health care-associated strains.

Clinical

It has been reported that maggot therapy
Maggot therapy
Maggot therapy is a type of biotherapy involving the intentional introduction of live, disinfected maggots into the non-healing skin and soft tissue wound of a human or animal for the purpose of cleaning out the...

 to clean out necrotic tissue of MRSA infection has been successful. Studies in diabetic patients reported significantly shorter treatment times than those achieved with standard treatments.

Many antibiotics against MRSA are in phase II and phase III clinical trials. e.g.:
  • Phase III : ceftobiprole
    Ceftobiprole
    Ceftobiprole is a 4th generation cephalosporin antibiotic with activity against methicillin-resistant Staphylococcus aureus, penicillin-resistant Streptococcus pneumoniae, Pseudomonas aeruginosa, and Enterococci. It was discovered by Basilea Pharmaceutica and was developed by Johnson & Johnson...

    , Ceftaroline
    Ceftaroline
    Ceftaroline fosamil is an advanced-generation cephalosporin antibiotic. It is active against methicillin-resistant Staphylococcus aureus and Gram-positive bacteria. It retains the activity of later-generation cephalosporins having broad-spectrum activity against Gram-negative bacteria...

    , Dalbavancin
    Dalbavancin
    Dalbavancin is a novel second-generation lipoglycopeptide antibiotic. It belongs to the same class as vancomycin, the most widely-used and one of the few treatments available to patients infected with methicillin-resistant Staphylococcus aureus .Dalbavancin is a novel semisynthetic...

    , Telavancin
    Telavancin
    Telavancin is a bactericidal lipoglycopeptide for use in MRSA or other Gram-positive infections. Telavancin is a synthetic derivative of vancomycin....

    , Aurograb, torezolid
    Torezolid
    Torezolid is an oxazolidinone drug in phase-II clinical trials for complicated skin and skin-structure infections , including those caused by Methicillin-resistant Staphylococcus aureus ....

    , iclaprim
    Iclaprim
    Iclaprim , codenamed AR-100 and RO-48-2622, is a diaminopyrimidine dihydrofolate reductase inhibitor being developed for the treatment of complicated skin and soft tissue infections caused by antibiotic-resistant bacteria. It is structurally related to trimethoprim...

    ...
  • Phase II : nemonoxacin.

Pre-clinical

An entirely different and promising approach is phage therapy
Phage therapy
Phage therapy is the therapeutic use of bacteriophages to treat pathogenic bacterial infections. Although extensively used and developed mainly in former Soviet Union countries circa 1920, this method of therapy is still being tested for treatment of a variety of bacterial and poly-microbial...

 (e.g., at the Eliava Institute in Georgia
Georgia (country)
Georgia is a sovereign state in the Caucasus region of Eurasia. Located at the crossroads of Western Asia and Eastern Europe, it is bounded to the west by the Black Sea, to the north by Russia, to the southwest by Turkey, to the south by Armenia, and to the southeast by Azerbaijan. The capital of...

), which in mice had a reported efficacy against up to 95% of tested Staphylococcus isolates.

On May 18, 2006, a report in Nature identified a new antibiotic, called platensimycin
Platensimycin
Platensimycin, a metabolite of Streptomyces platensis, which is an excellent example of a unique structural class of natural antibiotics, has been demonstrated to be a breakthrough in recent antibiotic researches due to its unique functional pattern and significant antibacterial activity...

, that had demonstrated successful use against MRSA.

A 2010 study noted significant antimicrobial action of Ulmo 90 and manuka UMF 25+ honey against several microorganisms, including MRSA. The investigators noted the superior antimicrobial action of Ulmo 90 honey, and suggested it be investigated further. A separate 2010 study examined the use of medical-grade honey against several antibiotic-resistant strains of bacteria, including MRSA. The study concluded that the antimicrobial action of the honey studied was due to the activity of hydrogen peroxide, methylglyoxal, and a novel compound named bee defensin-1.

Ocean-dwelling living sponges produce compounds that may make MRSA more susceptible to antibiotics.

Some semi-toxic fungi/mushrooms excrete broad spectrum antibiotics, not all of which have been fully identified.

Cannabinoids
Cannabinoids
Cannabinoids are a class of chemical compounds that include the phytocannabinoids , and chemical compounds that mimic the actions of phytocannabinoids or have a similar structure...

 (components of Cannabis sativa
Cannabis sativa
Cannabis sativa is an annual herbaceous plant in the Cannabaceae family. Humans have cultivated this herb throughout recorded history as a source of industrial fibre, seed oil, food, recreation, spiritual enlightenment and medicine...

), including cannabidiol
Cannabidiol
Cannabidiol is a cannabinoid found in Cannabis. It is a major constituent of the plant, representing up to 40% in its extracts.It has displayed sedative effects in animal tests...

 (CBD), cannabinol
Cannabinol
Cannabinol is a psychoactive substance cannabinoid found in Cannabis sativa and Cannabis indica/afghanica. It is also a metabolite of tetrahydrocannabinol . CBN acts as a weak agonist of the CB1 and CB2 receptors, with lower affinity in comparison to THC.- External links :* Compounds found in...

 (CBN), cannabichromene
Cannabichromene
Cannabichromene is a cannabinoid found in the cannabis plant. It bears structural similarity to the other natural cannabinoids, including tetrahydrocannabinol, tetrahydrocannabivarin, cannabidiol, and cannabinol, among others...

 (CBC) and cannabigerol
Cannabigerol
Cannabigerol is a non-psychoactive cannabinoid found in the Cannabis genus of plants. Cannabigerol is found in higher concentrations in hemp rather than in varieties of Cannabis with high THC content ....

(CBG), show activity against a variety of MRSA strains.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK