Influence of quinolones on throat- and faecal flora of healthy volunteers.

Oral and faecal flora were monitored in ten healthy volunteers who received three different oral dosages of either norfloxacin or ciprofloxacin during five consecutive days. Oral flora was not influenced by either quinolone. At the end of the five day-treatment period aerobic Gram-negative bacilli could no longer be cultured from the faecal samples of any of the volunteers. Enterococci were suppressed in some volunteers or remained present in concentrations as high as before treatment. All ciprofloxacin-treated volunteers became colonized with yeasts in their faecal samples, even during treatment with the lowest dose. As measured by total microscopic bacterial clump counts and the appearance of beta-aspartylglycine in faecal samples neither of the two quinolones appeared to decrease the colonization resistance of the digestive tract.