In vitro susceptibility of nosocomial Pseudomonas aeruginosa, enterobacteriaceae, and staphylococci to ciprofloxacin and ten other broad-spectrum antibiotics.

We determined microdilution minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) for ciprofloxacin and 10 beta-lactam and aminoglycoside antibiotics against 329 unique nosocomial isolates of Pseudomonas aeruginosa, citrobacter, enterobacter, serratia, and staphylococci. All were susceptible to ciprofloxacin, including 109 aminoglycoside-resistant gram-negative bacilli and 59 oxacillin-resistant staphylococci. Ciprofloxacin was generally 2-4 fold less active against aminoglycoside-resistant isolates than against their aminoglycoside-susceptible counterparts.