Microbewiki:''Streptoccus mutans'' and Dental Caries

PROFILES IN BACTERIOLOGY:

What is Streptococcus mutans?

Contents

[Classification]

[S. mutans and dental caries]

[Biofilm]

[S. mutans and early childhood caries]

[References]

Gram Stain of Streptoccus mutans. CDC/Dr. Richard Facklam. 1975.

Streptococcus mutans is a Gram positive streptococcus bacterium that inhabits human teeth and has been demonstrated to be the primary bacterial cause of dental caries (commonly known as cavities). S. mutans is part of the normal flora or normal microbiota of humans, so the presence of S. mutans in the mouth does not automatically cause dental caries.

Here is a culture of Streptococcus mutans grown in the laboratory:

LA plate streaked with Streptococcus mutans and incubated at 37ºC for 24 hours

Hedetniemi, Kevin and M-K, Liao. 2006.  Luria Broth (LB) and Luria Agar (LA) Media and Their Uses: Streptococcus mutans. Furman University, Greenville, SC. http://www.microbelibrary.org/index2.php?option=com_resource&controller=article&Itemid=73&article=3033. 25 April 2013.

Want to know more about how S. mutans causes cavities? See the [S. mutans and dental caries] page.

References:

• Image 1043, Public Health Image Library. CDC website.

 http://phil.cdc.gov/phil/details.asp?pid=1043

• Tortora, G. J., Funke, B. R., and Case, C. L. Microbiology: An Introduction, Tenth edition. 2010 Pearson Education, Inc.

Classification

h2 Classification of Streptococcus mutans

Streptoccus mutans is a gram positive bacterium.

• Domain: Bacteria
• Phylum: Firmicutes (low G-C, Gram + bacteria)
• Class: Bacilli
• Order: Lactobacillales
• Family:Streptococcaceae
• Genus: Streptococcus
• Species: Streptococcus mutans

Note: Historically, Streptococcus mutans has sometimes been categorized in the group mutans Streptococci, a group of oral bacteria discovered concurrently. More recently, it has been realized that the original researchers had actually cultured multiple species that were not as related as they believed. For more explanation on the various oral bacteria related to Streptococcus mutans, follow this link to a tutorial:

http://www.ncl.ac.uk/dental/oralbiol/oralenv/tutorials/streps.htm

References:

• Allmann, Amber. Streptococcus mutans. Wiki.

http://bioweb.uwlax.edu/bio203/s2007/allmann_ambe/

• Image 1043, Public Health Image Library. CDC website.

 http://phil.cdc.gov/phil/details.asp?pid=1043

h2 The role of Streptococcus mutans in dental caries

h3 What are dental caries?

• dental caries areas of decay brought on by bacterial infections of the teeth
• dental caries are considered to be an infectious disease

{image:worksite:/Wiki figures/Toothdecaystages.jpg|Toothdecaystages.jpg}

Open content from WikiEducator.org

This figure shows the progression of dental caries from affecting only the outer surface of the tooth (enamel caries) to more advanced forms of decay in which inner tooth structures are also affected. Different species of bacteria are involved in these stages of dental caries. Streptoccus mutans is associated with the early stage, enamel caries.

h3 How do caries form?

• Streptococcus mutans exist as part of the normal flora of the mouth

• S. mutans adhere to the teeth as part of a [biofilm]

• other species of bacteria join this mass of S. mutans bacteria on the teeth

    * Actinomyces attaches by extensions called fimbriae to the dextran (a sugar) that S. mutans secretes 

• S. mutans metabolizes sucrose (table sugar) and secretes lactic acid as a byproduct

• lactic acid can demineralize the teeth, leading to indentations in the enamel that are called cavities

• S. mutans is involved in enamel caries, but other bacteria are more abundant in later stages of caries

References:

• Oral Health in America: A Report of the Surgeon General. Ch. 3: Dental and Periodontal Infections.

 http://www.nidcr.nih.gov/datastatistics/surgeongeneral/sgr/chap3.htm

• Tortora, G. J., Funke, B. R., and Case, C. L. Microbiology: An Introduction, Tenth edition. 2010 Pearson Education, Inc. p. 81, 163, 431, 707-708

h3 Biofilms

h2 What is a biofilm?

• a coating (film) of bacteria (bio) that adhere to one another and to a surface
• Biofilms are made up of the bacteria (or other microbes) and also a matrix of sugars and other polymeric substances that connect the cells to one another.

{image:worksite:/Wiki figures/Sauer_Biofilms and Biocomplexity adjusted figure5.png|Sauer_Biofilms and Biocomplexity adjusted figure5.png}

Figure adapted from "Biofilms and Biocomplexity." Karin Sauer, Alex. H. Rickard, and David G. Davies. The biofilm developmental process in stages. (1) reversible attachment, (2) irreversible attachment, (3 & 4) maturation and (5) dispersion.

h2 Some common biofilms:

• dental plaque
• shower scum
• algae on swimming pool walls

Bacteria in biofilms communicate and form pillars so that water and nutrients can flow past each of them.

Here is a biofilm on glass shower door:

{image:worksite:/Wiki figures/shower scum_windowcleaningz dotcom_2.jpg|shower scum_windowcleaningz dotcom_2.jpg}

And here is a swimming pool wall bearing a biofilm of algae:

{image:worksite:/Wiki figures/algae_biofilm_pool.png|algae_biofilm_pool.png}

h2 Why do biofilms matter?

Biofilms are stubborn against techniques like brushing and even antibiotics or disinfectants, so dental plaque will still build up even if a person does brush his teeth. This is why regular cleanings are important: the tools the hygienist uses can help to remove the plaque from teeth.

References:

• Marsh, P.D. "Dental Plaque as a Microbial Biofilm." ~~Caries Research~~. 2004.
• Sauer, K., Rickard, A. H., and Davies, D.G. "Biofilms and Biocomplexity." ~~Microbe~~, 2007, 2:7, p. 350.
• Tortora, G. J., Funke, B. R., and Case, C. L. ~~Microbiology: An Introduction~~, Tenth edition. 2010 Pearson Education, Inc. p. 81, 163, 431, 707-708