Streptococcus sanguinis

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Streptococcus sanguinis (formerly known as Streptococcus sanguis) is a Gram-positive facultative anaerobe that is part of the Streptococcus genus. It is commonly found in the human mouth and is a significant component of the oral microbiome. Streptococcus sanguinis plays a crucial role in the formation of dental plaque and is associated with endocarditis, an infection of the inner lining of the heart.

Characteristics

Streptococcus sanguinis is a cocci-shaped bacterium that typically forms chains. It is non-motile and does not form spores. As a facultative anaerobe, it can grow in both the presence and absence of oxygen. The bacterium is catalase-negative and exhibits alpha-hemolysis on blood agar, producing a greenish discoloration around the colonies.

Role in Oral Health

Streptococcus sanguinis is one of the early colonizers of the dental plaque biofilm. It competes with other bacteria, such as Streptococcus mutans, for adhesion sites on the tooth surface. By doing so, it can inhibit the growth of more harmful bacteria that are associated with dental caries (tooth decay). The presence of Streptococcus sanguinis is generally considered beneficial for maintaining oral health.

Pathogenicity

While Streptococcus sanguinis is typically a commensal organism in the mouth, it can become pathogenic under certain conditions. If it enters the bloodstream, it can adhere to damaged heart valves or other areas of the endocardium, leading to infective endocarditis. This condition is serious and requires prompt medical treatment, often involving antibiotics and sometimes surgery.

Diagnosis and Treatment

Diagnosis of infections caused by Streptococcus sanguinis typically involves blood cultures and molecular techniques such as polymerase chain reaction (PCR). Treatment usually includes a course of antibiotics, with the choice of antibiotic depending on the susceptibility profile of the bacterial strain.

Prevention

Good oral hygiene practices, such as regular brushing and flossing, can help prevent the overgrowth of Streptococcus sanguinis and other bacteria in the mouth. For individuals at high risk of endocarditis, such as those with pre-existing heart conditions, prophylactic antibiotics may be recommended before certain dental procedures.

See also

• Streptococcus
• Oral microbiome
• Dental plaque
• Endocarditis
• Dental caries