Norfloxacin (MK-0366, AM-715): in vitro activity and cross-resistance with other organic acids including quality control limits for disk diffusion testing.

Norfloxacin is a new organic acid antimicrobic with an expanded spectrum that includes Staphylococcus spp, most Pseudomonas spp, Acinetobacter calcoaceticus ssp anitratus, some streptococci, as well as nearly all enteric bacilli. The drug appears to be bactericidal. Its expanded spectrum suggests that it should be tested separately by disk diffusion or other susceptibility testing methods. Tentative norfloxacin disk test quality control limits were derived from the results of a multi-laboratory study: Escherichia coli, 28-36 mm; S. aureus, 17-28 mm, and Pseudomonas aeruginosa, 22-29 mm.