Mouth Bacteria: How Many Types of Bacteria are Found in the Mouth & How are they Related to Health?

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Mouth Bacteria

Of all the types of microbes living in your mouth, bacteria are the most numerous. It has been estimated that there are over 100 million in every millilitre of saliva from more than 600 different species.

Unless there are open wounds or cuts inside your mouth, most mouth bacteria will do you no harm. Some are swallowed and are killed by stomach enzymes; others perish when they are attacked by enzymes in saliva. However, mouth bacteria are responsible for some of the most common bacterial diseases in humans. And they are gum disease and tooth decay (caries).

What are Some Types of Bacteria in the Mouth?

Here are some examples of the sorts of bugs that can be found in the mouth.

Streptococcus mutans (S. mutans) and similar related species cause tooth decay. The bacteria digest the sugars and starches in foods and produce acids which dissolve tooth enamel.

Porphyromonas gingivalis are associated with periodontal (gum) diseases.

Other types of mouth bacteria include Staphylococcus epidermidis, Streptococcus salivarius, and Lactobacillus sp.

In August 2008 scientist at King’s College Hospital in London discovered an entirely new mouth bacteria species. It’s called Prevotella histicola, nestles in the flesh lining the mouth, and is believed to contribute to tooth decay and gum disease. If you want to make a name for yourself and discover a new bacterium then the mouth is a pretty good place to start. Every drop of saliva contains millions of bacteria, and about half of them are unknown to science.

Mouth Bacteria and Health

There are also strong links between the bacteria in your mouth and overall health and well being, and some types have mouth bacteria have been linked to serious diseases.

In 2005 researchers from the Forsyth Institute in Boston discovered high levels of mouth bacteria C. gingivalis, P. melaninogenica and S. mitis, present in oral cancer patients, strongly suggesting a link.

In 2009 University of Buffalo researchers reported a link between the amount of mouth bacteria and an increased risk of a heart attack. That is, the link is not due to the types of bacteria but their numbers.

If mouth bacteria are linked to diseases elsewhere in the body they will provide the basis for simple diagnostic tests that can be used as early predictors of disease. And knowledge of friendly mouth bacteria is spearheading the development of more chewing gums and toothpastes containing the helpful bugs. The idea is that their presence will prevent harmful bacteria from sticking to teeth and causing damage.


  1. Koshy Philip et al. Identification of Major Cultivable Aerobic Bacteria in the Oral Cavity of Malaysian Subjects. American Journal of Biochemistry and Biotechnology 4 (4): 367-370, 2008

  2. S. Nyfors et al. Impact of antimicrobial exposure and β-lactamase-producing bacteria on salivary β-lactamase activity in infancy. International Journal of Antimicrobial Agents: 24 (5) 463-467, 2004