In vitro activity of ciprofloxacin against aminoglycoside-sensitive and -resistant gram-negative rods

Ciprofloxacin's activity against 233 clinically isolated strains of both fermentative and non-fermentative bacilli was tested. In particular the authors studied the sensitivity of aminoglycoside-resistant gram-negative bacilli to ciprofloxacin. The results showed that all fermentative gram-negative bacteria were sensitive to ciprofloxacin (MICs range less than or equal to 0.02 - 1.56 mg/l). Among the non-fermentative bacilli, Pseudomonas were generally susceptible to ciprofloxacin (MIC90 less than or equal to 1.56 mg/l) except for P. cepacia and P. fluorescens (MIC90 less than or equal to 3.12 mg/l). The best antibiotic activity was shown against Moraxella, A. xylosoxidans and A. hydrophila (MICs less than or equal to 0.09 mg/l). MICs for Acinetobacter and A. faecalis were less than or equal to 1.56 mg/l while Flavobacterium were more resistant (range 1.56-3.12 mg/l). Furthermore, ciprofloxacin showed good activity against 44 aminoglycoside-resistant isolates, showing a very low (13%) incidence of resistance.