Antimicrobial susceptibility of Neisseria gonorrhoeae in Zaire: High level plasmid-mediated tetracycline resistance in Central Africa

Abstract

Objective: To determine the in vitro antimicrobial susceptibility of gonococcal strains isolated in 1988 among female prostitutes in Kinshasa, Zaire and to characterise strains with high level tetracycline resistance. Methods: Minimal inhibitory concentrations of 8 antimicrobials were measured by agar dilution technique. Plasmid profiles and serovars were determined. Results: Two hundred and thirteen strains of Neisseria gonorrhoeae were tested of which 59% were β-lactamase producers and an additional 21% showed intermediate or chromosomal resistance to penicillin (MIC = 0.5-8 mg/l). Eleven percent of the strains were resistant to the combination sulfamethoxazoletrimethoprim (MIC > 8 mg/l) and 57% of the isolates showed decreased susceptibility to thiamphenicol (MIC = 1-4 mg/l). All strains were sensitive to spectinomycin, norfloxacin and ceftriaxone and moderately sensitive to kanamycin. Chromosomal resistance to tetracycline was observed in 45% of strains (MIC = 2-8 mg/l). Ten percent were highly resistant to tetracycline (TRNG, MIC = 16-128 mg/l) and were shown to carry a plasmid borne Tet M determinant; such strains were not found in Kinshasa in 1985. TRNG belonged to 4 different serovars, which were also the dominant serovars in non-TRNG. Conclusion: These findings illustrate the high frequency of multiresistant gonococci in Zaire and suggest that high level tetracycline resistant strains of N. gonorrhoeae have become endemic in Central Africa.