Mutations to increased antibiotic sensitivity in naturally-occurring gonococci

Abstract

CLINICAL isolation of mutations giving increased drug sensitivity has not been previously reported. The experiments presented here indicate that a significant proportion of clinical strains of Neisseria gonorrhoeae contain mutations which result in markedly increased susceptibility to a variety of antibiotics. Previously, Maness and Sparling¹ isolated and characterised mutants (env) of laboratory gonococci which had markedly increased sensitivity (‘hypersensitivity’) to a variety of antibiotics, detergents and dyes. The env mutations were phenotypically dominant over, and totally suppressed, low-level nonspecific drug resistance determined by mutations at a locus formerly designated ery², but now designated mtr³. Both mtr and env affected the permeability of the cell envelope⁴. Most of the clinical hypersensitive strains are also shown to (possess mutations to nonspecific drug resistance, similar to mtr, which are suppressed phenotypically. We have studied strains which included 502 random isolates from patients in North Carolina with uncomplicated gonococcal urethritis and cervicitis, as well as selected erythromycin-hypersensitive strains from London (kindly supplied by 1. Phillips), and five penicillinase-producing gonococci (four from the Far East, one from Rotterdam).