Prevalence of ciprofloxacin resistance in multiresistant gram-negative intensive care unit isolates

Of 107 gram-negative isolates obtained from intensive care units examined for patterns of multiresistance to 16 antimicrobial agents, 54.2% were multiresistant, defined as resistant to three or more test antimicrobials. Ciprofloxacin had excellent activity against all isolates with 93.4% susceptibility. Ciprofloxacin also performed well on multiresistant isolates with 89.7% susceptibility, which included 42.2% inducible Enterobacteriaceae. All six multiresistant ciprofloxacin-resistant isolates were resistant to five or more of the tested antimicrobials (mean 9.0), including a highly resistant Proteus mirabilis urine isolate resistant to 14 of 16 agents. The only antimicrobial to which all of the ciprofloxacin-multi-resistant isolates were resistant, was ampicillin, indicating an absence of cross resistance. In addition, ciprofloxacin had excellent activity (100% susceptibility) against Enterobacter spp. and Klebsiella pneumoniae, two organisms frequently associated with nosocomial infections.