The effect of DU-6859a, a new potent fluoroquinolone, on fecal microflora in human volunteers.

Following the oral administration of DU-6859a to six healthy male volunteers at 100 mg per dose three times a day for seven consecutive days, the degree of disturbances of fecal microflora and fecal drug concentrations were examined. The total viable count decreased transiently during the administration due to changes in the number of members of the family Bacteroidaceae, the most predominant organisms. The other obligate anaerobes and most aerobes including facultative anaerobes were suppressed markedly by DU-6859a, with an exception of yeasts. Members of the family Enterobacteriaceae and most of anaerobic bacteria were reduced to below the detection limit in all subjects from the 3rd day of administration period to one day after the discontinuation of the drug. Clostridium difficile was detected in one of the volunteers at the end of administration. Side effects, such as mild transient soft stool and mild transient diarrhoea, were observed in five and one volunteers, respectively. During the administration, DU-6859a was detected in feces at high concentrations which correlated well with the decrease of susceptible members of fecal flora as well as their detection rate.