[Multi-step increase in resistance of Neisseria gonorrhoeae isolates after repeated in-vitro subinhibitory concentrations of second-generation quinolones].

Five recent gonococcal isolates were exposed to subinhibitory concentrations of several antibiotics in vitro 25 times. In the presence of rifampicin all strains quickly became resistant. In the presence of penicillin, enoxacin and ciprofloxacin, antimicrobial susceptibility also decreased. Here development of resistance, however, corresponded to the multi- and not to the one-step type. It seems remarkable that even at the end of the experiments no strain grew at concentrations of ciprofloxacin exceeding 0.064 mg/l. In conclusion, quick development of resistance need not be expected after the introduction of newer quinolones into the therapy of gonorrhoea on a large scale.