Streptococcus mutans
Overview
 
Streptococcus mutans is a facultatively aerobic
Facultative anaerobic organism
A facultative anaerobic organism is an organism, usually a bacterium, that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation...

, Gram-positive
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...

 coccus-shaped 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...

 commonly found in the human
Human
Humans are the only living species in the Homo genus...

 oral cavity and is a significant contributor to tooth decay
Dental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...

.
The microbe was first described by J Kilian Clarke in 1924.
Streptococcus mutans is a gram-positive organism that is the primary causative agent in the formation of dental cavities in humans. Gram-positive bacteria are those that are stained dark-blue or violet by Gram staining.
Encyclopedia
Streptococcus mutans is a facultatively aerobic
Facultative anaerobic organism
A facultative anaerobic organism is an organism, usually a bacterium, that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation...

, Gram-positive
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...

 coccus-shaped 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...

 commonly found in the human
Human
Humans are the only living species in the Homo genus...

 oral cavity and is a significant contributor to tooth decay
Dental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...

.
The microbe was first described by J Kilian Clarke in 1924.

Introduction

Streptococcus mutans is a gram-positive organism that is the primary causative agent in the formation of dental cavities in humans. Gram-positive bacteria are those that are stained dark-blue or violet by Gram staining. This is based on the physical properties of their cell walls, as opposed to gram-negative bacteria, which cannot retain the crystal violet stain. Streptococcus
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...

is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. S. mutans, a member of the human oral flora, is widely recognized as the main etiological agent of dental caries. Conditions in the oral cavity
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

 are diverse and complex, frequently changing from one extreme to another. Thus, to survive in the oral cavity, S. mutans must tolerate rapidly harsh environmental fluctuations and exposure to various toxic chemicals in order to survive. However, the mechanisms under which this cariogenic pathogen can survive and proliferate under such extreme environmental conditions are largely unknown, as little research has been done on this matter.

Ecology

Twenty-five species of oral streptococci live in the oral cavity. Each species has developed specific specialized properties for colonizing different oral sites and constantly changing conditions to fight competing bacteria and to withstand external attacks. Imbalances in the microbial biota can initiate oral diseases. Under special conditions, commensal streptococci can switch to opportunistic pathogens, initiating disease and damaging the host. Oral streptococci has both harmless and harmful bacteria. “Mutans streptococci” are the most important bacteria associated with tooth decay. S. mutans, the microbial species most strongly associated with carious lesions, is naturally present in the human oral microbiota. The taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 of these complex bacteria remains tentative. A 1970’s study found that S. mutans was more prevalent on the pits and fissures, constituting 39% of the total streptococci in the oral cavity. Fewer S. mutans were found on the buccal surface (2-9%).

Role in tooth decay

Early colonizers of the tooth surface are mainly Neisseria
Neisseria
The Neisseria is a large genus of commensal bacteria that colonize the mucosal surfaces of many animals. Of the 11 species that colonize humans, only two are pathogens. N. meningitidis and N. gonorrhoeae often cause asymptomatic infections, a commensal-like behavior...

spp. and streptococci, including S. mutans. The growth and metabolism of these pioneer species changes local environmental conditions (e.g., Eh, pH, coaggregation, and substrate availability), thereby enabling more fastidious organisms to further colonize after them, forming dental plaque
Dental plaque
Dental plaque is a biofilm, usually a pale yellow, that develops naturally on the teeth. Like any biofilm, dental plaque is formed by colonizing bacteria trying to attach themselves to a smooth surface...

. Along with S. sobrinus
Streptococcus sobrinus
Streptococcus sobrinus is a Gram-positive, catalase-negative, non-motile, and anaerobic member of the genus Streptococcus.-Pathology:...

, S. mutans plays a major role in tooth decay, metabolizing sucrose
Sucrose
Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...

 to lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

 using the enyzme Glucansucrase
Glucansucrase
Glucansucrase is an enzyme used by bacteria in human mouths such as Streptococcus mutans and Lactobacillus reuteri to produce long sticky biofilm chains to stick to teeth and cause tooth decay. However, the former is considered a worst offender and the latter an indicator of healthy mouth flora...

. The acidic environment created in the mouth by this process is what causes the highly mineralized
Mineralization (biology)
In biology, mineralization refers to the process where an organic substance is converted to an inorganic substance.This may also be a normal biological process which takes place during the life of an organism such as the formation of bone tissue or egg shells, largely with calcium.This term may...

 tooth enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

 to be vulnerable to decay. S. mutans is one of a few specialized organisms equipped with receptors that improve adhesion to the surface of teeth. Sucrose is used by S. mutans to produce a sticky, extracellular, dextran
Dextran
Dextran is a complex, branched glucan composed of chains of varying lengths...

-based polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

 that allows them to cohere, forming plaque. S. mutans produces dextran via the enzyme dextransucrase (a hexosyltransferase
Hexosyltransferases
Hexosyltransferases are a type of glycosyltransferase that catalyze the transfer of a hexose.Examples include:* glucosyltransferases - transfer glucose* galactosyltransferases - transfer galactose* fucosyltransferases - transfer fucose...

) using sucrose as a substrate
Substrate (biochemistry)
In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...

 in the following reaction:
n sucrose → (glucose)n + n fructose


Sucrose
Sucrose
Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...

 is the only sugar that S. mutans can use to form this sticky polysaccharide.

However, many other sugars—glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

, fructose
Fructose
Fructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...

, lactose
Lactose
Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...

—can be digested by S. mutans, but they produce lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

 as an end-product. It is the combination of plaque and acid that leads to dental decay. Due to the role the S. mutans plays in tooth decay, there have been many attempts to make a vaccine
Caries vaccine
A caries vaccine is a vaccine to prevent and protect against tooth decay.Streptococcus mutans has been identified as the major etiological agent of human dental caries.Several types of vaccines are being developed at research centers....

 for the organism. So far, such vaccines have not been successful in humans. Recently, proteins involved in the colonization of teeth by S. mutans have been shown to produce antibodies that inhibit the cariogenic process.

Life in the oral cavity

Surviving in the oral cavity, S. Mutans is the primary causal agent and the pathogenic species responsible for dental caries (tooth decay or cavities) specifically in the initiation and development stages.

Dental plaque
Dental plaque
Dental plaque is a biofilm, usually a pale yellow, that develops naturally on the teeth. Like any biofilm, dental plaque is formed by colonizing bacteria trying to attach themselves to a smooth surface...

 is typically the precursor to tooth decay and contains more than 600 different microorganisms, contributing to the oral cavity’s overall dynamic environment that frequently undergoes rapid changes in pH, nutrient availability, and oxygen tension. Dental plaque adheres to the teeth and consists of bacterial cells while plaque is the biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...

 on the surfaces of the teeth. Dental plaque and S. mutans is frequently exposed to "toxic compounds" from oral healthcare products, food additives, and tobacco. Degradation by-products of dental composites
Dental composite
Dental composite resins are types of synthetic resins which are used in dentistry as restorative material or adhesives. Synthetic resins evolved as restorative materials since they were insoluble, aesthetic, insensitive to dehydration, easy to manipulate and reasonably inexpensive...

 resins (fillings) can be another source of toxic chemicals that can interfere with the bacterial growth of S. mutans.

While S. mutans grows in the biofilm, cells maintain a balance of metabolism that involves production and detoxification. Biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...

 is an aggregate of microorganisms in which cells adhere to each other or a surface. Bacteria in the biofilm community can actually generate various toxic compounds that interfere with the growth of other competing bacteria. However, there have been very few studies on how S. mutans can tolerate such exposure to various toxic substances during its growth in the oral biofilm and is, thus, poorly understood.

S. mutans has over time developed strategies to successfully colonize and maintain a dominant presence in the oral cavity. The oral biofilm is continuously challenged by changes in the environmental conditions. In response to such changes, the bacterial community evolved with individual members and their specific functions to survive in the oral cavity. S. mutans has been able to evolve from nutrition-limiting conditions to protect itself in extreme conditions. Streptococci represents 20% of the oral bacteria and actually determines the development of the biofilms. Although S. mutans can be antagonized by pioneer colonizers, once they become dominant in oral biofilms, dental caries can develop and thrive.

Cariogenic potential

The etiological agent of dental caries is associated with its ability to metabolize various sugars, form a robust biofilm, produce an abundant amount of lactic acid, and thrive in the acid environment it generates.

Dental caries
Dental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...

 is a dental biofilm-related oral disease associated with increased consumption of dietary sugar. When dental biofilms remain on tooth surfaces, along with frequent consumption of sugar, acidogenic bacteria (members of dental biofilms) will metabolize the sugar to organic acids. Persistence of this acidic condition encourages the proliferation of acidogenic and aciduric bacteria as a result of their ability to survive at a low-pH environment. The low-pH environment in the biofilm matrix erodes the surface of the teeth and begins the “initiation” of the dental caries. If the adherence of S. mutans to the surface of teeth or the physiological ability (acidogenity and aciduricity) of S. mutans in dental biofilms can be reduced or eliminated, the acidification potential of dental biofilms and later cavity formations can be decreased.

Susceptibility to disease varies between individuals and immunological mechanisms have been proposed to confer protection or susceptibility to the disease. These mechanisms have yet to be fully elucidated but it seems that while antigen presenting cells are activated by S. mutans in vitro, they fail to respond in vivo. Immunological tolerance to S. mutans at the mucosal surface may make individuals more prone to colonisation with S. mutans and therefore increase susceptibility to dental caries.

In children

In general, S. mutans is acquired in the oral cavity at the moment of tooth eruption. But S. mutans has been detected in the oral cavity of predentate children. This suggests that the eruption of teeth is not a necessary prerequisite. Thus, this species may not be confined to dental plaque. The adhesion, invasion, and persistence within the oral cells are considered the virulence mechanism of S. mutans to colonize and survive in the oral cavity in the absence of a tooth surface.

Cardiovascular disease

S. mutans is implicated in the pathogenesis of certain cardiovascular diseases. S. mutans is the most prevalent bacterial species detected in extirpated heart valve tissues as well as in atheromatous plaques, with an incidence of 68.6% and 74.1%, respectively.

Prevention and Treatment

Practice of good oral hygiene
Oral hygiene
Teeth cleaning is part of oral hygiene and involves the removal of dental plaque from teeth with the intention of preventing cavities , gingivitis, and periodontal disease. People routinely clean their own teeth by brushing and interdental cleaning, and dental hygienists can remove hardened...

 including daily brushing, flossing and the use of appropriate mouthwash can significantly reduce the number of oral bacteria and inhibit their proliferation. Oral bacteria often live in plaque, a kind of biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...

 and hence mechnical removal of plaque is the most effective way of getting rid of harmful oral bacteria, as bacterial biofilms are notoriously resistant to antibiotics and antimicrobial rinses. However, there are some remedies used in the treatment of oral bacterial infection, in conjunction with mechanical cleaning.

Green tea extract

Green tea
Green tea
Green tea is made solely from the leaves of Camellia sinensis that have undergone minimal oxidation during processing. Green tea originates from China and has become associated with many cultures throughout Asia. It has recently become more widespread in the West, where black tea is traditionally...

 extract is rich in catechin
Catechin
Catechin is a natural phenol antioxidant plant secondary metabolite. The term catechins is also commonly used to refer to the related family of flavonoids and the subgroup flavan-3-ols ....

, a class of antioxidants. Topically applied green tea extract inhibits S. mutans growth, kills oral bacteria, combats oral plaque and inhibits collagenase activity.

Tea tree oil

Tea tree oil
Tea tree oil
Tea tree oil, or melaleuca oil, is a pale yellow colour to nearly clear essential oil with a fresh camphoraceous odor. It is taken from the leaves of the Melaleuca alternifolia, which is native to the northeast coast of New South Wales, Australia...

, when used in the form of a mouthwash
Mouthwash
Mouthwash or mouth rinse is a product used to enhance oral hygiene. Some manufacturers of mouthwash claim that antiseptic and anti-plaque mouth rinse kill the bacterial plaque causing cavities, gingivitis, and bad breath. Anti-cavity mouth rinse uses fluoride to protect against tooth decay...

 has been shown to be effective in killing several bacteria including S. mutans and fighting gingivitis.

Macelignan from nutmeg

Macelignan
Macelignan
Macelignan is a lignan. It can be found in Myristica fragrans, the nutmeg.-Medical research:One study has shown that macelignan may exert antimicrobial and anticariogenic activity against Streptococcus mutans, but this is not a currently used treatment....

, a compound found in nutmeg
Nutmeg
The nutmeg tree is any of several species of trees in genus Myristica. The most important commercial species is Myristica fragrans, an evergreen tree indigenous to the Banda Islands in the Moluccas of Indonesia...

, is shown to decrease the biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...

 level of S. mutans.

Curcuminoids

An article soon to be published in June 2011 explains that curcuminoids are the main component of turmeric and that they have a long range of pharmacological uses. Many studies of turmeric have revealed numerous pharmacological properties, including anti-inflammatory
Anti-inflammatory
Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....

, anti-parasitic
Anti-parasitic
Antiparasitics are a class of medications which are indicated for the treatment of parasitic diseases such as nematodes, cestodes, trematodes, infectious protozoa, and amoebas.-Antinematodes:* Mebendazole...

, anti-mutagenic, anticancer, and antimicrobial activities. More people have recently been turning to natural products to prevent dental caries and to treat oral diseases due to the emergence of undesirable side-effects of other medicines. Researchers discovered that a fraction could be separated from turmeric and showed that it had anti-biofilm activity. Researchers based this on a comparison of curcuminoid content and anti-acidogenic activity against S. mutans. The data showed that the separated turmeric fraction and curcuminoids may be effective in controlling dental biofilms and dental cavity formations, as dental biofilms and dental cavity formations are related.

Barley Tea

In addition, Roasted barley tea, a popular drink in East Asia, has a compound that has been demonstrated to inhibit S. mutans biofilms.

Lollipop

Scientists recently developed safe and effective sugar-free herbal lollipops that kill cavity-causing bacteria. As already established, tooth decay is caused by cariogenic bacteria like S. mutans. S. mutans converts sugars into acids that dissolve minerals in the tooth enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

. A previous study found that novel compound from the extraction of licorice roots, Glycyrrhizol A, has strong antimicrobial activity against cariogenic bacteria. Killing such bacteria would control or prevent tooth decay. Researchers produced specific herbal extracts to develop a sugarfree lollipop
Lollipop
A lollipop, pop, lolly, sucker, or sticky-pop is a type of confectionery consisting mainly of hardened, flavored sucrose with corn syrup mounted on a stick and intended for sucking or licking. They are available in many flavors and shapes.- Types :Lollipops are available in a number of colors and...

 to kill bacteria such as S. mutans. Subsequent studies on humans showed a reduction of cariogenic bacteria in the oral cavity after eating these lollipops.

See also

  • Streptococcus viridans
    Streptococcus viridans
    Viridans Streptococcus is a pseudotaxonomic non-Linnaenan term for a large group of commensal streptococcal bacteria that are either α-hemolytic, producing a green coloration on blood agar plates , or nonhemolytic...

  • Mutacin 1140
    Mutacin 1140
    Mutacin 1140 is an antibiotic produced by Streptococcus mutans. It has activity against a broad spectrum of gram-positive bacteria....

  • Oral microbiology
    Oral microbiology
    Oral microbiology is the study of the microorganisms of the oral cavity and the interactions between the oral microorganisms with each other and with the host. Of particular interest is the role of oral microorganisms in the two major dental diseases: dental caries and periodontal disease.The mouth...

  • Xylitol
    Xylitol
    Xylitol is a sugar alcohol sweetener used as a naturally occurring sugar substitute. It is found in the fibers of many fruits and vegetables, and can be extracted from various berries, oats, and mushrooms, as well as fibrous material such as corn husks and sugar cane bagasse, and birch...

     reduces Streptococcus
    Streptococcus
    Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...

  • Dental caries
    Dental caries
    Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...


External links

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