Vancomycin is often used for serious infection and endocarditis caused by the following (except for vancomycin - resistant strains): Methicillin-resistant S aureus Methicillin-resistant coagulase-negative staphylococci Certain beta-lactam-resistant and multidrug-resistant Streptococcus pneumoniae Beta-hemolytic streptococci (when beta-lactams cannot be used because of drug allergy or resistance) Corynebacterium species including C jeikeium, and C striatum Viridans streptococci (when beta-lactams cannot be used because of drug allergy or resistance) Enterococci (when beta-lactams cannot be used because of drug allergy or resistance) However, vancomycin is less effective than antistaphylococcal beta-lactams for methicillin-susceptible S aureus infections.