Comparative antimicrobial activity of gatifloxacin with ciprofloxacin and beta-lactams against gram-positive bacteria

Gatifloxacin is a new 8-methoxy fluoroquinolone. The in-vitro antibacterial activity of gatifloxacin was compared to that of ciprofloxacin, ceftriaxone, imipenem, piperacillin/tazobactam and amoxicillin/clavulanic acid against 165 streptococcal isolates, 369 staphylococcal isolates, and 50 enterococcal isolates recently recovered from clinical isolates. Gatifloxacin was the most active agent tested against streptococci including penicillin-nonsusceptible Streptococcus pneumoniae (MIC 90 0.5 μg/mL). Imipenem and gatifloxacin (MIC 90 0.5 μg/mL) were the most active agents tested against viridans group streptococci. All the agents demonstrated excellent activity against methicillin-susceptible S. aureus. Imipenem, piperacillin/tazobactam, amoxicillin/clavulanic acid, and gatifloxacin had good activity against methicillin-sensitive S. epidermidis. Among the methicillin-sensitive and methicillin-resistant coagulase-negative staphylococci tested, gatifloxacin was the most active agent. Amoxicillin/clavulanic acid and gatifloxacin were the most active agents against E. faecalis. Thus, gatifloxacin possesses equal or superior activity when compared to ciprofloxacin and beta-lactams making it a promising new fluoroquinolone for clinical use in treating Gram-positive infections.