Question

I need to know all this information about Streptococcus mutans (tooth decay) please. PLEASE BE CLEAR AND ABLE TO UNDERSTAND IT I WILL RATE.

-Virulence (Describe ability to cause disease; how are host defense inhibited or evaded; how does microbe gain nutrition from host)

-Epidemiology (Incidence, Prevalence, Person, Place, Time, Relative facts)

Answer 1

Answer :

Streptococcus mutans belongs to Streptococcus viridans' group which are miscellaneous Streptococci and are found as commensals in buccal cavity. Miscellaneous because these can not be grouped in Lancefield classification.

Streptococcus mutans is gram positive coccus which has ability to mutate into rods under acidic conditions; hence the name mutans.

Aerobe to facultative anaerobe, Streptococcus mutans is part of normal microbiota of the mouth but are opportunistic pathogen and in presence of favourable conditions can lead to plaque formation, dental caries with tooth decay and dental cavities. It can ferment lots of sugars and thus can easily survive in the mouth. In extreme cases it can lead to bacteriemia and can lead to endocarditis, connecting tooth decay to dental hygiene.

On breakdown of dietary sucrose, Streptococcus mutans produces lactic acid and a tough adhesive dextran. This extracellular polysaccharide capsular layer adds to virulence of this otherwise commensal organism. The acid damages the dentine and dextran binds together the food debris and other bacteria and leads to formation of dental plaque which leads to dental caries. This is seen in all age groups from infants to adults. The close association between dental caries and Streptococcus mutans was established when in monkeys, injecting vaccine against this bacterium prevented experimental caries.

Epidemiological evidence shows that with change in eating habits of the human beings, shifting from hunters to agricultural species had lead to evolution of this organisms into pathogens. The increase in intake of carbohydrate and introduction of fermented foods helped this bacteria to evolve and get its virulence factors of ability to ferment many sugars, ability to form capsular dextran and make a biofilm layer and its ability to not only survive but thrive in highly acidic conditions. Genetic evidence further confirms the ability of this organism to evolve by acquiring certain genes from other oral species through lateral or horizontal gene transfer.