Serum bactericidal activity of ciprofloxacin and ofloxacin in volunteers.

The serum bactericidal activity of two newer quinolones, ciprofloxacin and ofloxacin, against 206 clinical bacterial isolates was determined in six male volunteers after oral administration of either 500 mg of ciprofloxacin or 200 mg of ofloxacin respectively. The highest bactericidal titers were achieved against Enterobacteriaceae 1 h after ciprofloxacin administration, ranging from 1:121 for indole-positive Proteus species to 1:30 for Serratia spp. Ofloxacin generated lower titers, ranging from 1:14 for indole-positive Proteus spp. to 1:2.5 for Enterobacter spp. Only low serum bactericidal titers were found for Pseudomonas aeruginosa, Acinetobacter spp. and gram-positive cocci. It is concluded that the activity of orally administered ciprofloxacin is superior to that of orally administered ofloxacin in the serum bactericidal test.