[Detection of penicillinase-producing Neisseria gonorrhoeae from male patients with urethritis]

Abstract

Eighty-nine isolates of Neisseria gonorrhoeae from 89 male urethritis patients were studied for beta-lactamases (penicillinase) production, and their susceptibilities to benzylpenicillin, amoxicillin, piperacillin, clavulanic acid/amoxicillin (Augmentin), cephalexin, cefotaxime, spectinomycin and minocycline were determined by an agar plate-dilution method. Penicillinase activity was tested by a chromogenic cephalosporin method with nitrocefin as substrate (CefinaseTM discs, BBL, USA) and by a paper strip acidimetric method with benzylpenicillin as substrate (beta-Lactamase detection papers, Oxoid, UK). In addition, 60 of the 89 patients were examined for Chlamydia trachomatis, using fluorescein-labeled monoclonal antibodies (Direct specimen test; Micro TrakTM, Syva Co., USA). Penicillinase-producing N. gonorrhoeae (PPNG) were found in 12 of the 89 strains (13.5%). Although all these strains of PPNG were highly resistant to benzylpenicillin and amoxicillin, the minimum inhibitory concentrations (MICs) of Augmentin markedly decreased. Piperacillin was highly active against not only non-PPNG but also PPNG strains. More than half the isolates were resistant to cephalexin (MICs greater than or equal to 12.5 micrograms/ml) while all strains including non-PPNG and PPNG were fully sensitive to cefotaxime (MICs less than or equal to 0.20 microgram/ml). Spectinomycin and minocycline had MIC ranges of 6.25 to 25 micrograms/ml and 0.01 to 3.13 micrograms/ml, respectively; the ranges for non-PPNG and PPNG strains were fairly similar. C. trachomatis was detected in 11 (18.3%) out of 60 patients examined. The increasing incidence of PPNG and coexisting chlamydial infection should be taken into account in the treatment of gonococcal urethritis.