Antibiotic susceptibility patterns and plasmid profiles of penicillinase-producing Neisseria gonorrhoeae strains in durban, South Africa, 1990-1993

Background and Objectives: The appearance of strains of Neisseria gonorrhoeae resistant, both chromosomally and plasmid-mediated, to penicillin and other antibiotics makes this versatile pathogen difficult to treat. There is, therefore, a need for surveillance of N. gonorrhoeae strains to determine the efficacy of current therapeutic measures. Goals: To survey the antibiotic susceptibilities and plasmid profiles of penicillinase-producing N. gonorrhoeae strains isolated over a 4-year period. Study Design: Penicillinase-producing N. gonorrhoeae strains were detected by the chromogenic cephalosporin test. Minimum inhibitory concentrations to penicillin G, tetracycline, ceftriaxone, and ciprofloxacin were determined using the E-test. Plasmid DNA was obtained by the alkaline lysis method and profiles generated. Results: Penicillinase-producing N. gonorrhoeae strains increased from 16.4% to 19.0% in the period from 1990 through 1993. Although all strains were resistant to penicillin, strains were susceptible to varying levels of ciprofloxacin, ceftriaxone, and even tetracycline. All penicillinase-producing N. gonorrhoeae strains possessed the 2.6-megadalton cryptic plasmid, and in addition 87.7% contained the 24.5-megadalton conjugative plasmid. Of the six known gonococcal β-lactamase plasmids, the 4.4-megadalton Asian and 3.2-megadalton African plasmids were predominant. The most prevalent plasmid profile contained the 2.6-megadalton cryptic, 24.5-megadalton conjugative, and 4.4-megadalton Asian plasmids. Conclusions: To ensure effective treatment of gonorrhea, continued surveillance of the antimicrobial susceptibilities and plasmid profiles of penicillinase- producing N. gonorrhoeae strains is necessary.