Characteristics of Medically Important Streptococci
Name | Group-Specific Substancea | Hemolysisb | Habitat | Important Laboratory Criteria | Common and Important Diseases |
---|---|---|---|---|---|
Pyogenic Streptococci | |||||
Streptococcus pyogenes | A | β | Throat, skin | Large colonies (>0.5 mm), PYRc test positive, inhibited by bacitracin | Pharyngitis, impetigo, deep soft tissue infections; bacteremia; rheumatic fever, glomerulonephritis, toxic shock |
Streptococcus agalactiae | B | β | Urogenital tract, lower GI tract | Hippurate hydrolysis, CAMP-factor positived | Neonatal sepsis and meningitis; bacteremia, UTIs,e meningitis in adults |
Streptococcus dysgalactiae subspecies equisimilis; others | A, C, G | β (human) infections), α, none | Throat | Large (>0.5 mm) colonies | Pharyngitis, pyogenic infections similar to group A streptococci |
Viridans Streptococci | |||||
Streptococcus bovis groupf | D | None | Colon, biliary tree | Growth in presence of bile, hydrolyze esculin, no growth in 6.5% NaCl, degrades starch | Endocarditis, common blood isolate in colon cancer, biliary disease |
Streptococcus anginosus group (S. anginosus, Streptococcus intermedius, Streptococcus constellatus) | F (A, C, G) and untypeable | α, β, none | Throat, colon, urogenital tract | Small (<0.5 mm) colony variants of β-hemolytic species; group A are bacitracin resistant and PYR negative; carbohydrate fermentation patterns; arginine, esculin, VPg positive | Pyogenic infections, including brain, liver, lung abscesses |
Mutans group | Usually not typed | α, none | Oral cavity | Carbohydrate fermentation patterns; esculin, VP positive | Dental caries (Streptococcus mutans), endocarditis; abscesses (with many other bacterial species) |
Mitis-Sanguinis group | |||||
Streptococcus pneumoniae | None° | α | Nasopharynx | Susceptible to optochin; colonies soluble in bile; quellung reaction positive | Pneumonia, meningitis, bacteremia, otitis media, sinusitis |
Streptococcus mitis | None | α, none | Oral cavity | VP negativeg; carbohydrate fermentation patterns | Endocarditis; bacteremia, sepsis in immunocompromised patients; high-level resistance to penicillin |
Salivarius group | None | α, none | Oral cavity | VP positive; carbohydrate fermentation patterns | Bacteremia, endocarditis, meningitis |