Streptococcus

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

GI, gastrointestinal.

aLancefield classification.

bHemolysis observed on 5% sheep blood agar after overnight incubation.

cHydrolysis of L-pyrrolidonyl-β-naphthylamide (PYR).

dCAMP, Christie, Atkins, Munch-Peterson.

eUTIs, urinary tract infections.

fIncludes the human species: Streptococcus gallolyticus subspecies gallolyticus; Streptococcus gallolyticus subspecies macedonicus; Streptococcus gallolyticus subspecies pasteurianus; Streptococcus infantarius subspecies infantarius.

gVP, Voges Proskauer; all viridans group streptococci are VP positive except the mitis group.

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