Answer:
Hydrogen peroxide production
Step-by-step explanation:
To answer this question, I'll base my response on the paper ''The Biology of Streptococcus mutans'' by Lemos et al. See in bold my comments, please.
The paper states the following virulence mechanisms of S. mutans:
(i) ''the ability to synthesize large quantities of extracellular polymers of glucan from sucrose that aid in the permanent colonization of hard surfaces and in the development of the extracellular polymeric matrix in situ'' --> This refers to the capacity of forming biofilm. A biofilm is basically an extracellular gel-like substance made of mainly sugars and proteins. It protects the bacterial community from antibiotics and further colonization of other microorganisms.
In the case of S. mutans, this ability is absolutelly useful to attach to the itself to the dental plaque
(ii) the ability to transport and metabolize a wide range of carbohydrates into organic acids (acidogenicity) --> These ''wide range of carbohydrates'' can come from the debris of food that remains on our teeth. S. mutans uses these compounds in its favour, as it can utilise this acidity to gnaw the dental plaque surface
(iii) the ability to thrive under environmental stress conditions, particularly low pH (aciduricity) --> S. mutans has enzymes that let it thrive the acid condition of the oral cavity. These enzyme can convert the H+ derived of the acid into less harmful molecules such as H2O. Therefore, S mutans adapts itself to set the colonization step and ''dodge the obstacles''
According to the paper, the production of Hydrogen peroxide is not a capacity from S. mutans, it turns out that the commensal bacteria (i.e the bacteria community that lives within our mouth) produce it in order to prevent the colonization of S. mutans. The paper states the following: ''At pHs close to neutrality, production of H2O2 by peroxigenic bacteria and other antimicrobial products produced by oral commensals prevent the overgrowth of specific pathogens (e.g. S. mutans) on dental biofilms'' --> Therefore, S. mutans is not able of producing Hydrogen peroxide. It could eventually have enzymes to neutralise it, and those could be considered as virulence factors then.
All in all, I strongly consider reading this paper. If you're interested, I suggest you to read what's written on Figure 2 of the paper.