Interpretive criteria for CI-960, fleroxacin and temafloxacin susceptibility tests with Haemophilus influenzae.

Haemophilus influenzae strains with varied ampicillin resistance and beta-lactamase production patterns were tested against three investigational fluorinated quinolones (CI-960, fleroxacin, temafloxacin) using Haemophilus Test Medium (HTM) and National Committee for Clinical Laboratory Standards (NCCLS) methods. The disk diffusion zones and MICs were compared and regression statistics and scattergrams generated. The rank order of the agents according to activity against Haemophilus influenzae was CI-960 (MIC50 0.002 microgram/ml) greater than temafloxacin (MIC50 0.015 microgram/ml) greater than fleroxacin (MIC50 0.03 microgram/ml). The recommended susceptibility interpretive criteria for the 5-micrograms disks of each drug were: for CI-960 greater than or equal to 23 mm (MIC correlate less than or equal to 1 microgram/ml); for fleroxacin greater than or equal to 19 mm (MIC correlate less than or equal to 2 micrograms/ml); and for temafloxacin greater than or equal to 16 mm (MIC correlate less than or equal to 2 micrograms/ml). All recent Haemophilus influenzae isolates tested were susceptible to these potent fluoroquinolones and no interpretive errors were observed.