Streptococcus mutans

Streptococcus mutans ( Gram stain )

Streptococcus mutans is a bacterium of the genus Streptococcus (Streptococcus ). S. mutans is the Leitorganismus of dental caries and are present in almost every human being in the saliva. The degree of concentration of S. mutans in saliva is closely correlated with the risk of caries.

Description

S. mutans has approximately spherical to ovoid cells ( " cocci " ), which are arranged in pairs or chains and does not move actively. The bacterium is gram- positive, facultative anaerobic, oxidative and fermentative has energy metabolism and does not form spores. On Gelnährmedien with complex nutrients S. mutans forms rounded, convex colonies with granular surface. Most strains acting α - hemolytic ( green coloration of the blood). In three strains but also a β - hemolysis ( complete dissolution of red blood cells and degradation of hemoglobin ) was detected.

Pathophysiology

Streptococcus mutans is the most important cause of tooth decay. The pathogen has a number of special properties ( virulence factors ), which assign a major role in the formation of bacterial plaque:

• Glukanvermittelte adherence: S. mutans forms of sucrose contained in the chyme extracellular glucans, with which the bacteria are able to adhere to the tooth enamel. There is thus formed on the surfaces of the teeth a biofilm. The formation of glucans is mediated by glycosyl transferases (enzymes for the transfer of glucose units). The activity of glucosyltransferases provides a benchmark for the virulence of the pathogen.
• Lactic acid production by S. mutans is building as part of a fermentative energy metabolism of carbohydrates to lactic acid (lactate ) from. The resulting drop in pH leads to demineralization of tooth substance.
• Acid tolerance: Through the active elimination of protons S. mutans to survive in a position, even in strongly acidic medium.