Viridans Streptococci Flashcards
S.mutans
Contributes to dental caries.
Synthesize large sticky polysaccharides (dextrans and levans) from sucrose
S mutans and S sanguis
Odontopathogens responsible for the formation of dental plaque
S mitis
Mostly found around the cheek region
S salivarius
Found on the dorsal side of the tongue
S intermedius
Cause abscesses in the brain or abdominal organs
2) microbiological diagnosis
> culture
Blood agar plate:
- typically alpha-hemolytic
- S.anginosus can be beta-hemolytic
- produce green color on blood agar (Latin for green = viridis)
> specific tests
- catalase: negative
- optochin: resistant (R)
Optochin is a bile salt
Distinguished from S.pneumoniae using optochin test
3) treatment and prevention
> antimicrobial susceptibility tests
- disk diffusion susceptibility testing should be done routinely on isolated from significant infections
1) classification
Family: streptococcaceae
Genus: streptococcus
Species: viridans
Alpha hemolytic streptococcal- group D
Generally low pathogenicity
- non pyogenic streptococci
- biochemically and antigenically diverse groups
- part of normal mouth flora
- lack either the polysaccharide capsule typical for S.pneumonia or the Lancefield antigens of the pyogenic group members
- group D is distinguished from other viridans streptococci by bile solubility and optochin sensitivity
Other species
Contain species:
S.Bovis S.anginosus S.sanguis S.salivarius S.mutans S.intermedius S.mitis
B-A-S-S-M-I-M
S.viridans
Cause endocarditis and dental abscesses
4) disease
Viridans streptococci cause:
Sub-acute bacteremia endocarditis (SBE): in individuals with congenitally deformed or rheumatically affected heart valves.
Account for 30 - 40% of endocarditis.
Infection is endogenous: organisms reach blood stream through teeth extraction or tonsillectomy
They settle on deformed valves and lead to inflammation
Mortality: 50%
