Cross-resistance and cross-susceptibility between fluoroquinolone agents.

The results of broth microdilution susceptibility tests with 750 bacterial isolates were used to directly compare six different fluoroquinolone antibiotics (ciprofloxacin, enoxacin, fleroxacin, lomefloxacin, ofloxacin and temafloxacin). Against enteric bacilli, enoxacin and lomefloxacin were similar in their spectra of activity but they differed from the other drugs tested. Against the non-enteric gram-negative bacilli, ciprofloxacin differed from enoxacin and lomefloxacin: fleroxacin, ofloxacin and temafloxacin were nearly identical in their activity. For routine susceptibility tests, ofloxacin and fleroxacin were similar in activity and either drug could be used as a class representative for predicting susceptibility to the other fluoroquinolone agents. Occasionally, strains that are resistant to the class representative may be susceptible to other members of the fluoroquinolone class, but those that are susceptible to the class representative are rarely resistant to the other compounds.