Antimicrobial use prior to the acquisition of multiresistant bacteria

We assessed whether patients who acquired methicillin-resistant Staphylococcus aureus (MRSA) had less exposure to antimicrobial agents than did those who acquired Enterobacteriaceae that produced extended-spectrum beta-lactamase (ESbetaL). In a 6-month, prospective study, ESbetaL carriers had received antimicrobial therapy more often than had MRSA carriers. Amoxicillin-clavulanic acid, fluoroquinolones, and third-generation cephalosporins, especially ceftazidime, had been prescribed more often for ESbetaL carriers than for MRSA carriers.