Impact of gemifloxacin on the normal human intestinal microflora

Gemifloxacin is a new fluoroquinolone that has been shown to possess a broad spectrum of antimicrobial activity against gram-positive and gram-negative microorganisms including methicillin-susceptible and methicillin-resistant staphylococci, Streptococcus pneumoniae, Haemophilus influenzae and most members of the family Enterobacteriaceae. The aim of the present study was to investigate the effect of gemifloxacin on the human intestinal microflora. Gemifloxacin was given in oral doses of 320 mg for 7 days to 10 healthy subjects and 5 subjects received a once-daily dose of matched placebo for 7 days. Faecal samples were collected prior to administration (days -8 and -6), during the administration period (days 2 and 4) and after withdrawal of administration (days 8, 11, 21, 28 and 56). In the aerobic intestinal microflora the numbers of enterobacteria were suppressed during the gemifloxacin administration and the numbers of enterococci and streptococci were also decreased. No other aerobic microorganisms were affected. In the anaerobic microflora the numbers of anaerobic cocci and lactobacilli were suppressed during the gemifloxacin administration while no other changes occurred. The microflora was normalized 49 days after the administration of gemifloxacin had stopped. No selection or overgrowth of resistant bacterial strains or yeasts occurred. The ecological impact of gemifloxacin was shown to be selective and similar to that of ciprofloxacin, levofloxacin and ofloxacin.