Diminished vancomycin and daptomycin susceptibility during prolonged bacteremia with methicillin-resistant Staphylococcus aureus

An elderly patient with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia was treated sequentially with vancomycin plus rifampin then daptomycin plus gentamicin. The MRSA strain developed diminished susceptibility to vancomycin (MIC increase and tolerance), daptomycin, and gentamicin, and resistance to rifampin during therapy.