Multiple Antibiotic Resistance due to a Single Mutation in Neisseria gonorrhoeae

Abstract

A positive correlation (r > +.47, P 1 .01) was found between sensitivities of 147 random clinical isolates of Neisseria gonorrhoeae to all possible pairs of the drugs penicillin, tetracycline, erythromycin, chloramphenicol, acridine orange, and ethidium bromide. High-level resistance to streptomycin was also positively correlated with increased resistance to some of these drugs. This suggested that multiply-resistant strains are not exclusively the result of selection of independent mutants for resistance to each drug and that there may be a common mechanism for resistance to some or all of these drugs. This hypothesis was supported by the demonstration that low-level resistance to a large group of drugs (penicillin, tetracycline, erythromycin, chloramphenicol, rifampin, ethidium bromide, and acridine orange) could be lost as well as restored by a single mutational event in vitro. Resistance of Neisseria gonorrhoeae to antibiotics has gradually become an important practical problem during the last decade [1-6], but there has been almost no scientific inquiry into the genetic and biochemical mechanisms of resistance. Several features of the clinical epidemiology of resistance of the gonococcus to antibiotics aroused our curiosity and prompted these studies. Numerous authors have noted strong positive correlations between sensitivities of individual