STREPTOCOCCUS MUTANS: CHARACTERISTICS, DISEASES - BIOLOGY - 2025

Streptococcus mutans is a bacterium that participates in the formation of dental plaque or biofilm that forms on the enamel of the teeth. It is a microorganism that belongs to the oral microbiota in humans and represents 39% of the total Streptococcus in that area.

It has been pointed out as the main causal agent for the onset of dental caries, a disease characterized by the destruction of the hard tissues of the tooth. In fact, it was first isolated by J. Kilian Clarke from a carious lesion.

By KDS4444, from Wikimedia Commons

The predisposition of some people to suffer more caries episodes than others has to do with multiple factors, including poor oral hygiene, the presence of cariogenic microorganisms and the abuse of foods rich in sucrose. These factors influence the imbalance of the oral microbiota, where the population of S. mutans is exacerbated.

The prevalence of dental caries in the population is quite frequent. It is estimated that 88.7% of people between 5 and 65 years of age have presented at least one episode of dental caries in their life, with children and adolescents being the most vulnerable population.

characteristics

Streptococcus mutans. Gram stain. By Photo Credit: Content Providers (s): Streptococcus mutansTranswiki approved by: w: en: User: Dmcdevit, via Wikimedia Commons

-They are characterized by being facultative anaerobes, which means that they can live in the presence or absence of oxygen.

-They require 5-10% CO2 to grow in the laboratory, which is why they are called microerophiles.

-According to the hemolysis produced in the blood agar culture medium, it is classified as alpha or gamma hemolytic.

-They are microorganisms very susceptible to environmental changes, so they do not survive long outside the body.

-At the laboratory level they are very demanding from the nutritional point of view.

Taxonomy

However, there is another classification based on the sequence analysis of the 16SrRNA gene. In this sense, it was classified as a "S. mutans" Group, which does not include a single species, but houses other antigenically similar Streptococci such as: S. mutans, S. sobrinus, S. cricetus, S. macacae, S rattus, S. downeii and S. ferus.

Many of these species are typical of some animals and are rarely found in man. Only S. mutans and S. sobrinus are common microbiota of the human oral cavity.

Morphology

Caries are characterized by the appearance of a black dot on the tooth surface that can progress from the enamel to the pulp and can spread to the periodontium. This process is favored by high sugar concentrations and low pH.

Periodontitis

It begins with gingivitis (inflammation of the gums), then progresses to periodontitis (inflammation of the periodontium), where there is a loss of dental support due to resorption of the alveolar bone and periodontal ligaments.

Loss of teeth

It is the consequence of poor oral care and hygiene, where cavities and periodontitis cause the total loss of the tooth.

Bacterial endocarditis

It has been observed that some patients who have developed bacterial endocarditis have Streptococcus of the Viridans Group as the causative agent, among which is S. mutans.

This has coincided with poor oral hygiene and periodontal disease in these patients, suggesting that the door of entry is the oral lesion.

Transmission

It is believed that S. mutans is acquired as a common oral microbiota at an early age, through contact with the mother (vertical transmission), and can be transmitted through saliva from one individual to another (horizontal transmission).

Diagnosis

Streptococcus mutans is catalase and oxidase negative like all Streptococcus. They are isolated in enriched culture media such as blood agar.

They grow at 37 ºC with 10% CO ₂ in 24 hours of incubation in microaerophilic hoods. Colonies are small and alpha or gamma hemolytic.

S. mutans hydrolyzes esculin and produces acid from mannitol and sorbitol. They are identified with the API Rapid STREP system.

Prevention

The prevention and control of dental plaque is vital to avoid the appearance of cavities, periodontitis and the loss of teeth.

Saliva is a natural mechanism that protects against tooth decay, thanks to the content of lysozymes, sialoperoxidase and IgA immunoglobulin.

Other natural defenses are the presence of some bacteria such as Streptococcus gordonii, Streptococcus sanguinis and Veillonella parvula, which antagonize the growth of S. mutans by the production of H ₂ O _2.

However, this is not enough, being necessary to take other prevention measures.

To do this, you must maintain good oral hygiene. This consists of daily brushing with fluoride-containing toothpaste after each meal, flossing and the use of mouthwashes.

In addition to this, it will be necessary to visit the dentist regularly to carry out periodic review and cleaning of dental plaque, in addition to avoiding excess sweets, especially in children.

Treatment

Treatment is often expensive. The teeth can be saved as long as it is attacked at the beginning.

Sometimes root canal treatment may be needed when decay reaches the dental pulp. In the worst case, the extraction of the complete piece and the placement of a prosthesis will be carried out.

References

1. Lemos JA, Quivey RG, Koo H, Abranches J. Streptococcus mutans: a new Gram-positive paradigm? Microbiology. 2013; 159 (3): 436-445.
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3. Ryan KJ, Ray C. Sherris. Medical Microbiology, 6th Edition McGraw-Hill, New York, USA; 2010. p 688-693
4. Ojeda-Garcés Juan Carlos, Oviedo-García Eliana, Luis Andrés Rooms. Streptococcus mutans and dental caries. CES odontol. 2013; 26 (1): 44-56.
5. Wikipedia contributors. Streptococcus mutans. Wikipedia, The Free Encyclopedia. March 23, 2018, 12:08 UTC. Available at: en.wikipedia.org/ Accessed September 3, 2018.
6. Roa N, Gómez S, Rodríguez A. Response of T cells, cytokines and antibodies against the peptide (365-377) of the cell adhesion protein of Streptococcus mutans. Univ Odontol. 2014; 33 (71): 29-40.
7. Graciano M, Correa Y, Martínez C, Burgos A, Ceballos J, Sánchez L. Streptococcus mutans and dental caries in Latin America. Systematic review of the literature. Rev Nac de Odontol. 2012; 8 (14): 32-45.
8. Berkowitz RJ. Acquisition and transmission of mutans streptococci. J Calif Dent Assoc. 2003; 31 (2): 135-8.