Abiotrophia spp

Gram Stain

• Gram positive cocci in pairs and chains-often very pleomorphic (aerobic)

Clinical Significance

These organisms are part of commensal oropharyngeal flora.  They can cause native and prosthetic valve endocarditis, bacteremia, ophthalmic infections and have rarely been implicated in post-partum infections, febrile neutropenia, central nervous system infections (brain abscess and meningitis), wound infections and otitis media.

Usual Susceptibility Pattern

Penicillin susceptibility is variable but most isolates remain susceptible to ampicillin. Susceptibility to cephalosporins is variable (including 3rd and 4th generation).

Cefepime is less active than ceftriaxone. These organisms are considered resistant to cefazolin.

Imipenem has better activity than meropenem. Tolerance to beta-lactam antibiotics has been documented.

These organisms are typically susceptible to clindamycin, vancomycin, linezolid and rifampin (rifampin may be useful as combination therapy for central nervous system infections).

Susceptibility to quinolones and tetracyclines is variable. Resistance to macrolides and daptomycin is common.

These organisms should be considered resistant to TMP-SMX

Combination therapy with rifampin may be useful for central nervous or prosthetic joint infections. For endovascular infections combination therapy with gentamicin may be useful.