Streptococcus Viridans Group (VGS)

S. mitis group

• S. australis
• S. cristatus
• S. gordonii
• S. infantis
• S. mitis
• S. oligofermentans
• S. oralis
• S. parasanguinis
• S. peroris
• S. pseudopneumoniae
• S. sanguinis
• S. sinensis
• S. tigurinus

S. mutans group

• S. cricetus
• S. downei
• S. ferus
• S. macarae
• S. mutans
• S. rattus
• S. sobrinus

S. salivarius group

• S. hyointestinalis
• S. salivarius
• S. thermophilus
• S. vestibularis

Gram Stain

• Gram positive cocci in chains (aerobic)

Clinical Significance

These organisms are part of the commensal flora of oropharynx, gastrointestinal, and female genitourinary tracts.

They are associated with endocarditis and sepsis (especially in pediatric oncology patients).

S. mitis group - associated with endocarditis (native/prosthetic) and septicemia in neutropenic patients.

S. mutans group - associated with dental caries as well as endocarditis (native/prosthetic).

S. salivarius group - associated with septicemia in neutropenic patients.

Usual Susceptibility Pattern

Susceptibility to penicillin and cephalosporins (including 3rd generation) varies within the various species.

S. mitis group tend to be the most resistant to beta-lactams.

Resistance to ceftriaxone/cefotaxime is not uncommon (regardless of penicillin susceptibility).

Ceftazidime, cephalexin, cefixime, and cloxacillin have poor activity against these organisms.

There is considerable macrolide and clindamycin resistance.

These organisms are susceptible to vancomycin, linezolid, and daptomycin.