Enhancement of antimicrobial effects of various antibiotics against methicillin-resistant Staphylococcus aureus (MRSA) by combination with fosfomycin.

The present study was designed to evaluate the efficacy of fosfomycin used in combination with drugs that were found to be less effective against methicillin-resistant Staphylococcus aureus (MRSA). Twelve different antibiotics were tested against 32 strains of MRSA isolated from the wounds of burn patients admitted to the Burn Unit at Tokyo Women's Medical University Hospital. These antibiotics - fosfomycin (FOM), flomoxef sodium (FMOX), imipenem (IPM), cefotiam (CTM), cefmetazole (CMZ), ampicillin (ABPC), sulbactam/cefoperazone (SBT/CPZ), minocycline (MINO), ofloxacin (OFLX), and panipenem (PAPM) - were used either alone or in combination. Arbekacin (ABK) and vancomycin (VCM) were used for comparing efficacy in controlling bacterial growth. While both ABK and VCM were, as expected, found to be effective in suppressing in vitro bacterial growth, all ten other agents when used alone were found to be ineffective. In contrast, these agents, when used in combination with FOM, showed remarkable efficacy against all strains of MRSA tested. Based upon the in vitro findings, it is suggested that FOM, in combination with other antimicrobial agents, such as IPM, PAPM, CMZ, and SBT/CPZ may be used instead of ABK and/or VCM to curtail the emergence of Staphylococcus aureus strains that are resistant to these latter two drugs.