Prior vancomycin use is a risk factor for reduced vancomycin susceptibility in methicillin-susceptible but not methicillin-resistant Staphylococcus aureus bacteremia.

Objective: Staphylococcus aureus is a cause of community- and healthcare-acquired infections and is associated with substantial morbidity, mortality, and costs. Vancomycin minimum inhibitory concentrations (MICs) among S. aureus have increased, and reduced vancomycin susceptibility (RVS) may be associated with treatment failure.

Prevalence of non-penicillin-susceptible group B streptococcus in Philadelphia and specificity of penicillin resistance screening methods.

A total of 1,991 group B streptococcus (GBS) isolates, collected in 2008 and 2009, were tested for non-penicillin susceptibility by broth microdilution, disk testing, and oxacillin screening agar. No GBS isolates were non-penicillin susceptible. Oxacillin and ceftizoxime disk testing results showed that proposed screening criteria are nonspecific.