Auxotypes, serovars, and trends of antimicrobial resistance of Neisseria gonorrhoeae in Kigali, Rwanda (1985-93)

Objective: To investigate the in vitro antimicrobial susceptibility and the auxotype/serovar distribution of Neisseria gonorrhoeae in Kigali, Rwanda, during 1985-93. Methods: As part of a monitoring programme the in vitro susceptibility of 1604 isolates of N gonorrhoeae was determined by agar dilution. Auxo- and serotyping was performed on 1350 and 1313 isolates respectively. Results: The prevalence of penicillinase producing N gonorrhoeae (PPNG) remained stable at a rate of 39% during 1985-91 and increased to 61% in 1992-3. Chromosomal resistance to penicillin was common among non-PPNG and resistance to thiamphenicol and tetracycline was common among both PPNG and non-PPNG. High level, plasmid mediated resistance to tetracycline (TRNG) was observed for the first time at the end of 1989 and increased from 2% of the isolates in 1990 to 50% by 1993. A trend for increasing resistance to norfloxacin and ofloxacin was observed during 1985-90 but disappeared in 1991-93. Five isolates with high level resistance to norfloxacin (MIC 2 mg/l) were observed in 1990. Resistance to trimethoprimsulphamethoxazole (TMP-SMZ) emerged at the end of 1990 and was observed among 10% of the isolates during 1991-3. All strains remained susceptible to ofloxacin, ciprofloxacin, spectinomycin, and ceftriaxone. Overall, 75% of the isolates were prototrophic or required proline for their growth and 62% belonged to serovars IA-6 and IB-1. The prevalence of serovar IB-4 increased strongly during the last 3 years of the study. Conclusion: Resistance to penicillin, thiamphenicol, and tetracycline was common in N gonorrhoeae during 1985-1993. The rapid spread of TRNG after 1989 and the steep increase of PPNG during 1992-3 were the most striking facts of the study period. The auxotype and serovar distribution was comparable with findings from other African countries.