Mycobacterium tuberculosis
Overview
Mycobacterium tuberculosis (MTB) is a pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

ic bacteria
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...

l species in the genus Mycobacterium
Mycobacterium
Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. The genus includes pathogens known to cause serious diseases in mammals, including tuberculosis and leprosy...

and the causative agent of most cases of tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...

 (TB). First discovered in 1882 by Robert Koch
Robert Koch
Heinrich Hermann Robert Koch was a German physician. He became famous for isolating Bacillus anthracis , the Tuberculosis bacillus and the Vibrio cholerae and for his development of Koch's postulates....

, M. tuberculosis has an unusual, waxy coating on its cell surface (primarily mycolic acid
Mycolic acid
Mycolic acids are long fatty acids found in the cell walls of the mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis. They form the major component of the cell wall of mycolata species...

), which makes the cells impervious to Gram staining, so acid-fast
Acid-fast
Acid-fastness is a physical property of certain bacteria, specifically their resistance to decolorization by acids during staining procedures.Acid-fast organisms are difficult to characterize using standard microbiological techniques Acid-fastness is a physical property of certain bacteria,...

 detection techniques are used, instead. The physiology of M. tuberculosis is highly aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...

 and requires high levels of oxygen.
Encyclopedia
Mycobacterium tuberculosis (MTB) is a pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

ic bacteria
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...

l species in the genus Mycobacterium
Mycobacterium
Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. The genus includes pathogens known to cause serious diseases in mammals, including tuberculosis and leprosy...

and the causative agent of most cases of tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...

 (TB). First discovered in 1882 by Robert Koch
Robert Koch
Heinrich Hermann Robert Koch was a German physician. He became famous for isolating Bacillus anthracis , the Tuberculosis bacillus and the Vibrio cholerae and for his development of Koch's postulates....

, M. tuberculosis has an unusual, waxy coating on its cell surface (primarily mycolic acid
Mycolic acid
Mycolic acids are long fatty acids found in the cell walls of the mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis. They form the major component of the cell wall of mycolata species...

), which makes the cells impervious to Gram staining, so acid-fast
Acid-fast
Acid-fastness is a physical property of certain bacteria, specifically their resistance to decolorization by acids during staining procedures.Acid-fast organisms are difficult to characterize using standard microbiological techniques Acid-fastness is a physical property of certain bacteria,...

 detection techniques are used, instead. The physiology of M. tuberculosis is highly aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...

 and requires high levels of oxygen. Primarily a pathogen of the mammalian respiratory system
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...

, MTB infects the lungs. The most frequently used diagnostic methods for TB are the tuberculin skin test, acid-fast stain, and chest radiographs.

The M. tuberculosis genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....

 was sequenced in 1998.

Pathophysiology

M. tuberculosis requires oxygen to grow
Obligate aerobe
An obligate aerobe is an aerobic organism that requires oxygen to grow. Through cellular respiration, these organisms use oxygen to oxidize substances, like sugars or fats, in order to obtain energy. During respiration, they use oxygen as the terminal electron acceptor...

. It does not retain any bacteriological stain due to high lipid content in its wall, and thus is neither Gram-positive nor Gram-negative; hence Ziehl-Neelsen staining, or acid-fast staining, is used. While mycobacteria do not seem to fit the Gram-positive category from an empirical standpoint (i.e., they do not retain the crystal violet
Crystal violet
Crystal violet or Gentian violet is a triarylmethane dye. The dye is used as a histological stain and in Gram’s method of classifying bacteria. Crystal violet has antibacterial, antifungal, and anthelmintic properties and was formerly important as a topical antiseptic...

 stain), they are classified as acid-fast
Acid-fast
Acid-fastness is a physical property of certain bacteria, specifically their resistance to decolorization by acids during staining procedures.Acid-fast organisms are difficult to characterize using standard microbiological techniques Acid-fastness is a physical property of certain bacteria,...

 Gram-positive bacteria due to their lack of an outer cell membrane
Outer membrane
The bacterial outer membrane is found in Gram-negative bacteria. Its composition is distinct from that of the cytoplasmic membrane - among other things, the outer leaflet of the membrane includes a complex lipopolysaccharide whose lipid portion acts as an endotoxin - and it is linked to the cell's...

.

M. tuberculosis divides every 15–20 hours, which is extremely slow compared to other bacteria, which tend to have division times measured in minutes (Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

can divide roughly every 20 minutes). It is a small bacillus
Bacillus (shape)
The word bacillus may be used to describe any rod-shaped bacterium, and such bacilli are found in many different taxonomic groups of bacteria. However, the name Bacillus, capitalized and italicized, refers to a specific genus of bacteria...

 that can withstand weak disinfectants and can survive in a dry state for weeks. Its unusual cell wall, rich in lipids (e.g., mycolic acid
Mycolic acid
Mycolic acids are long fatty acids found in the cell walls of the mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis. They form the major component of the cell wall of mycolata species...

), is likely responsible for this resistance and is a key virulence factor.

When in the lungs, M. tuberculosis is taken up by alveolar macrophages, but they are unable to digest the bacterium. Its cell wall prevents the fusion of the phagosome
Phagosome
In cell biology, a phagosome is a vacuole formed around a particle absorbed by phagocytosis. The vacuole is formed by the fusion of the cell membrane around the particle. A phagosome is a cellular compartment in which pathogenic microorganisms can be killed and digested...

 with a lysosome
Lysosome
thumb|350px|Schematic of typical animal cell, showing subcellular components. [[Organelle]]s: [[nucleoli]] [[cell nucleus|nucleus]] [[ribosomes]] [[vesicle |vesicle]] rough [[endoplasmic reticulum]]...

. Specifically, M. tuberculosis blocks the bridging molecule, early endosomal autoantigen 1 (EEA1); however, this blockade does not prevent fusion of vesicles filled with nutrients. Consequently, the bacteria multiply unchecked within the macrophage. The bacteria also carried the UreC gene, which prevents acidification of the phagosome. The bacteria also evade macrophage-killing by neutralizing reactive nitrogen intermediates.

The ability to construct M. tuberculosis mutants and test individual gene products for specific functions has significantly advanced our understanding of the pathogenesis
Pathogenesis
The pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...

 and virulence factors of M. tuberculosis. Many secreted and exported proteins are known to be important in pathogenesis.

Strain variation

M. tuberculosis comes from the genus Mycobacterium, which is composed of approximately 100 recognized and proposed species. The most familiar of the species are M. tuberculosis and M. leprae (leprosy). M. tuberculosis appears to be genetically diverse, which results in significant phenotypic differences between clinical isolates. M. tuberculosis exhibits a biogeographic population structure, and different strain lineages are associated with different geographic regions. Phenotypic studies suggest this strain variation never has implications for the development of new diagnostics and vaccines. Microevolutionary variation affects the relative fitness and transmission dynamics of antibiotic-resistant strains.

Hypervirulent strains

Mycobacterium outbreaks are often caused by hypervirulent strains of M. tuberculosis. In laboratory experiments, these clinical isolates elicit unusual immunopathology, and may be either hyperinflammatory or hypoinflammatory. Studies have shown the majority of hypervirulent mutants have deletions in their cell wall-modifying enzymes or regulators that respond to environmental stimuli. Studies of these mutants have indicated the mechanisms that enable M. tuberculosis to mask its full pathogenic potential, inducing a granuloma that provides a protective niche, and enable the bacilli to sustain a long-term, persistent infection.

Microscopy

M. tuberculosis is characterized by caseating granulomas containing Langhans giant cell
Langhans giant cell
Langhans giant cells are large cells found in granulomatous conditions.They are formed by the fusion of epithelioid cells , and contain nuclei arranged in a horseshoe-shaped pattern in the cell periphery....

s, which have a "horseshoe" pattern of nuclei. Organisms are identified by their red color on acid-fast staining.

Genome

The genome of the H37Rv strain was published in 1998. Its size is 4 million base pairs, with 3959 genes; 40% of these genes have had their function characterised, with possible function postulated for another 44%. Within the genome are also six pseudogenes.

The genome contains 250 genes involved in fatty acid metabolism, with 39 of these involved in the polyketide metabolism generating the waxy coat. Such large numbers of conserved genes show the evolutionary importance of the waxy coat to pathogen survival.

About 10% of the coding capacity is taken up by two clustered gene families that encode acidic, glycine-rich proteins. These proteins have a conserved N-terminal motif, deletion of which impairs growth in macrophages and granulomas.

Nine noncoding sRNAs
Mycobacterium tuberculosis sRNA
Mycobactierum tuberculosis contains at least nine small RNA families in its genome. The small RNA families were identified through RNomics - the direct analysis of RNA molecules isolated from cultures of Mycobacterium tuberculosis. The sRNAs were characterised through RACE mapping and Northern...

 have been characterised in M. tuberculosis, with a further 56 predicted in a bioinformatics
Bioinformatics
Bioinformatics is the application of computer science and information technology to the field of biology and medicine. Bioinformatics deals with algorithms, databases and information systems, web technologies, artificial intelligence and soft computing, information and computation theory, software...

 screen.

Symptoms

Only an estimated 10% of people infected with M. tuberculosis ever develop the disease, and many of those have the disease only for the first few years following infection, even though the bacillus may lie dormant in the body for decades.

The symptoms that patients infected with M. tuberculosis may experience are usually absent until the disease has become more complicated. It may take many months from the time the infection initially gets into the lungs until symptoms develop. A cough
Cough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...

 is, however, the first symptom of the 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...

 with M. tuberculosis. The initial symptoms, including loss of appetite, fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...

, productive cough and loss of energy or loss of weight or night sweats, are not specific and might be easily attributed to another condition.

Primary pulmonary tuberculosis is the first stage of the condition, and it may cause fever, dry cough and some abnormalities that may be noticed on a chest
Chest
The chest is a part of the anatomy of humans and various other animals. It is sometimes referred to as the thorax or the bosom.-Chest anatomy - Humans and other hominids:...

 X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

. In most cases, though, primary infections tend to cause no symptoms that people do not overcome. This condition resolves itself, although it returns in more than half of the cases.

Tuberculosis-causing lung disease may result in tuberculous pleuritis, a condition that may cause symptoms such as chest pain, nonproductive cough and fever. Moreover, infection with M. tuberculosis can spread to other parts of the body, especially in patients with a 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...

. This condition is referred to as miliary tuberculosis, and people contacting it may experience fever, weight loss, weakness and a anorexia
Anorexia (symptom)
Anorexia is the decreased sensation of appetite...

. In more rare cases, miliary tuberculosis can cause coughing and difficulty breathing.

Dormant (inactive) tuberculosis may return after a certain period of time, and it usually occurs in the upper lungs, causing severe symptoms, such as common cough with a progressive increase in production of mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

 and coughing up blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

. Most patients also develop fever, loss of appetite, unexplained weight loss and night sweats.

In cases in which the infection spreads to other parts of the body, additional symptoms may occur, depending on the exact site of the spread. If the infection spreads to the abdominal cavity
Abdominal cavity
The abdominal cavity is the body cavity of the human body that holds the bulk of the viscera. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is the thoracic diaphragm , and its oblique floor is the pelvic inlet...

, symptoms such as fatigue, swelling, slight tenderness and appendicitis-like pain are likely to occur. Also, painful urination
Urination
Urination, also known as micturition, voiding, peeing, weeing, pissing, and more rarely, emiction, is the ejection of urine from the urinary bladder through the urethra to the outside of the body. In healthy humans the process of urination is under voluntary control...

 might be a sign the infection has reached the bladder
Bladder
Bladder usually refers to an anatomical hollow organBladder may also refer to:-Biology:* Urinary bladder in humans** Urinary bladder ** Bladder control; see Urinary incontinence** Artificial urinary bladder, in humans...

. In children, M. tuberculosis infections may affect the bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

s, causing mild swelling and minimal pain. Fever, headache, nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

, drowsiness, and, if untreated, coma and brain damage
Brain damage
"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...

 may occur if the brain has been affected. If the infection affects the pericardium
Pericardium
The pericardium is a double-walled sac that contains the heart and the roots of the great vessels.-Layers:...

, symptoms and signs such as fever, enlarged neck veins, and shortness of breath may develop. Kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

 damage and the symptoms emerging with it, as well as sterility
Infertility
Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...

, may occur if the kidney and the reproductive system
Reproductive system
The reproductive system or genital system is a system of organs within an organism which work together for the purpose of reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes...

 are affected, respectively.

Diagnosis

Sputum
Sputum
Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....

 is taken on three successive mornings as the number of organisms could be low, and the specimen is treated with 3% KOH
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

 or NaOH for liquefaction
Liquefaction
Liquefaction may refer to:* Liquefaction, the general process of becoming liquid* Soil liquefaction, the process by which sediments become suspended* Liquefaction of gases in physics, chemistry, and thermal engineering* Liquefactive necrosis in pathology...

 and decontamination
Decontamination
Decontamination is the process of cleansing the human body to remove contamination by hazardous materials including chemicals, radioactive substances, and infectious material...

. Gram stain should never be performed, as the organism is an "acid-fast
Acid-fast
Acid-fastness is a physical property of certain bacteria, specifically their resistance to decolorization by acids during staining procedures.Acid-fast organisms are difficult to characterize using standard microbiological techniques Acid-fastness is a physical property of certain bacteria,...

 bacillus" (AFB), meaning it retains certain stains after being treated with acidic solution. In the most common staining technique, the Ziehl-Neelsen stain
Ziehl-Neelsen stain
The Ziehl–Neelsen stain, also known as the acid-fast stain, was first described by two German doctors; Franz Ziehl , a bacteriologist and Friedrich Neelsen , a pathologist. It is a special bacteriological stain used to identify acid-fast organisms, mainly Mycobacteria...

, AFBs are stained a bright red, which stands out clearly against a blue background; therefore, the bacteria are sometimes called "red snappers". The reason for the acid-fast staining is because of its thick waxy cell wall. The waxy quality of the 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...

 is mainly due to the presence of mycolic acid
Mycolic acid
Mycolic acids are long fatty acids found in the cell walls of the mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis. They form the major component of the cell wall of mycolata species...

s. This waxy cell wall also is responsible for the typical caseous
Caseous necrosis
Caseous necrosis is a form of cell death in which the tissue maintains a cheese-like appearance. The dead tissue appears as a soft and white proteinaceous dead cell mass.-Causes:...

 granuloma
Granuloma
Granuloma is a medical term for a tiny collection of immune cells known as macrophages. Granulomas form when the immune system attempts to wall off substances that it perceives as foreign but is unable to eliminate. Such substances include infectious organisms such as bacteria and fungi as well as...

 formation in tuberculosis. The component responsible, trehalose dimycolate
Trehalose dimycolate
Trehalose dimycolate is a molecule produced by Mycobacterium tuberculosis and other mycobacteria....

, is called the cord factor
Cord factor
Cord factor refers to lipoarabinomannan, a molecule generated from trehalose dimycolate by virulent strains of Mycobacterium tuberculosis and closely related species. It is a surface glycolipid which blocks macrophage activation by IFN-γ, induces secretion of TNFα and causes Mycobacterium...

. A grading system exists for interpretation of the microscopic findings based on the number of organisms observed in each field. Patients of pulmonary tuberculosis show AFBs in their sputum in only 50% of cases, which means, even if no organisms are observed, further investigation is still required. AFBs can also be visualized by fluorescent microscopy using auramine-rhodamine stain
Auramine-rhodamine stain
The auramine-rhodamine stain , also known as the Truant auramine-rhodamine stain, is a histological technique used to visualize acid-fast bacilli using fluorescence microscopy, notably species in the Mycobacterium genus. Acid-fast organisms display a reddish-yellow fluorescence. Although the...

 for screening, which makes them appear somewhat golden in color. Also, M. tuberculosis traditionally is grown on a selective medium, Lowenstein-Jensen medium
Lowenstein-Jensen medium
The Lowenstein–Jensen medium, more commonly known as LJ medium, is a growth medium specially used for culture of Mycobacterium, notably Mycobacterium tuberculosis....

. However, this method is quite slow, as this organism requires six to eight weeks to grow, which delays reporting of results. A faster result can now be obtained using Middlebrook medium or BACTEC.

Using BACTEC, the growth may be detected in about a week using C-14 labelled substrates. Culture media contains C-14 labelled palmitic acid. Mycobacteria metabolise these substrates and release radioactively labelled Carbon dioxide. The instrument measures labelled carbon dioxide and reports in terms of a 'growth index'. A growth index of 10 or more is considered as positive. This method can also differentiate between M. tuberculosis and M. bovis. As M. bovis is susceptible to TCH, incorporation of TCH in the medium inhibits the growth of M. bovis (i.e. the growth index decreases) but not that of M. tuberculosis.

Another rapid method for the detection of M. tuberculosis is Mycobacterial growth indicator tube (MGIT). It is a non-radiometric, automated method. It consists of tubes containing liquid culture media, and a fluorescent compound is embedded on the bottom of the tube. The fluorescent compound is sensitive to the dissolved oxygen in the liquid medium. When mycobacteria grow, they deplete the dissolved oxygen in the liquid medium and allows the compound to fluoresce brightly which can be detected by observing the tube under UV light. The results are obtained in 8 to 14 days.

During an advanced stage of tuberculosis, the organism may infect almost any part of the body, which means the specimen chosen should be appropriate for the symptoms or tissues (e.g. intestinal tuberculosis-stool
Human feces
Human feces , also known as a stool, is the waste product of the human digestive system including bacteria. It varies significantly in appearance, according to the state of the digestive system, diet and general health....

).

An immunochromatographic serological assay for the diagnosis of M. tuberculosis has also been developed.

Treatment

Treatment is usually administered on an outpatient basis, and consists mainly of medication
Medication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...

s. Usually, the treatment is given for six to nine months according to a therapy regimen consisting of two months of isoniazid
Isoniazid
Isoniazid , also known as isonicotinylhydrazine , is an organic compound that is the first-line antituberculosis medication in prevention and treatment. It was first discovered in 1912, and later in 1951 it was found to be effective against tuberculosis by inhibiting its mycolic acid...

, rifampin, and pyrazinamide
Pyrazinamide
Pyrazinamide is a drug used to treat tuberculosis. The drug is largely bacteriostatic, but can be bacteriocidal on actively replicating tuberculosis bacteria.-Abbreviations:...

, four months of isoniazid and rifampin, and ethambutol or streptomycin until the drug sensitivity is known. The drug treatment schema may be changed according to the laboratory results.

Antibiotics are usually part of therapy in people who have no symptoms and whose germs
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

 are in inactive state, because they are helpful in preventing the activation of the infection. The antibiotic used is isoniazid (INH), usually taken for six to 12 months, to prevent future activation. This medicine may not, however, be taken during pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

 or in people who suffer from liver disease
Liver disease
Liver disease is a broad term describing any single number of diseases affecting the liver.-Diseases:* Hepatitis, inflammation of the liver, caused mainly by various viruses but also by some poisons , autoimmunity or hereditary conditions...

 or alcoholism
Alcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...

. Moreover, several side effects have been reported; some can be even life-threatening. One of the side effects caused by this drug is peripheral neuropathy, meaning a decreased sensation in the extremities and which is normally prevented or avoided by administering vitamin B6
Vitamin B6
Vitamin B6 is a water-soluble vitamin and is part of the vitamin B complex group. Several forms of the vitamin are known, but pyridoxal phosphate is the active form and is a cofactor in many reactions of amino acid metabolism, including transamination, deamination, and decarboxylation...

 at the same time with isoniazid.

Patients who have active bacteria are usually treated with a combination of medications; the primary antibiotic, isoniazid, is used in conjunction rifampin, ethambutol
Ethambutol
Ethambutol is a bacteriostatic antimycobacterial drug prescribed to treat tuberculosis. It is usually given in combination with other tuberculosis drugs, such as isoniazid, rifampicin and pyrazinamide....

 and pyrazinamide
Pyrazinamide
Pyrazinamide is a drug used to treat tuberculosis. The drug is largely bacteriostatic, but can be bacteriocidal on actively replicating tuberculosis bacteria.-Abbreviations:...

.

Streptomycin
Streptomycin
Streptomycin is an antibiotic drug, the first of a class of drugs called aminoglycosides to be discovered, and was the first antibiotic remedy for tuberculosis. It is derived from the actinobacterium Streptomyces griseus. Streptomycin is a bactericidal antibiotic. Streptomycin cannot be given...

, a drug given by injection
Injection (medicine)
An injection is an infusion method of putting fluid into the body, usually with a hollow needle and a syringe which is pierced through the skin to a sufficient depth for the material to be forced into the body...

, may be used, as well, particularly when the disease is extensive and/or the patients do not take their oral medications reliably (termed "poor compliance").

Usually, treatment lasts for few months, but it can even be administered for years in some cases. Mainly, the success rate of the treatment is closely related to the patient's compliance and ability to take the drugs as prescribed.

History

M. tuberculosis, then known as the "tubercle bacillus
Bacillus
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...

", was first described on 24 March 1882 by Robert Koch
Robert Koch
Heinrich Hermann Robert Koch was a German physician. He became famous for isolating Bacillus anthracis , the Tuberculosis bacillus and the Vibrio cholerae and for his development of Koch's postulates....

, who subsequently received the Nobel Prize in physiology or medicine
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine administered by the Nobel Foundation, is awarded once a year for outstanding discoveries in the field of life science and medicine. It is one of five Nobel Prizes established in 1895 by Swedish chemist Alfred Nobel, the inventor of dynamite, in his will...

for this discovery in 1905; the bacterium is also known as "Koch's bacillus".

Tuberculosis has existed throughout history, but the name has changed frequently over time. In 1720, though, the history of tuberculosis started to take shape into what is known of it today; as the physician Benjamin Marten described in his A Theory of Consumption, tuberculosis may be caused by small living creatures that are transmitted through the air to other patients.

External links

  • Database of Mycobacterium tuberculosis genome sequences and related information.
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