In vitro activities of arbekacin, alone and in combination, against methicillin-resistant Staphylococcus aureus

We determined the in vitro activities of arbekacin in combination with other antibiotics against 96 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). Efficacies were evaluated by comparing frequencies of susceptible strains at concentrations of antibiotics present in serum 3 hours after intravenous administration of recommended dosages with those obtained with addition of 1 or 2 micrograms/ml of arbekacin. The addition of arbekacin significantly increased the antibacterial activities of cefotiam, cefuzonam, flomoxef and fosfomycin, but had no effect on the activity of either imipenem or minocycline. Arbekacin in combination with fosfomycin was found to have the greatest activity against MRSA among combinations tested. In addition, arbekacin had excellent antimicrobial activity against Pseudomonas aeruginosa, compared to other anti-pseudomonal agents such as piperacillin, ceftazidime and imipenem.