From 1983 to 1986 more than 2000 non-penicillinase producing Neisseria gonorrhoeae from Amsterdam, The Hague and Rotterdam were auxotyped and screened for susceptibility to 10 antibiotics by MIC determination. By far the commonest auxotypes were N.R. (non-requiring; 40%) and Pro- (proline requiring; 30%). During that period there was a substantial shift in the ratio of both auxotypes-roughly from 1:2 to 2:1-in The Hague. Pro- isolates were generally less susceptible than N.R. isolates, and there was a strong positive correlation between the MICs of the different drugs. The prevalence of isolates with a penicillin MIC equal to or above 0.5 IU/ml amounted to 14%, while in only 1% was the MIC above 1 IU/ml. Comparing our results with an earlier study by Stolz, Zwarte & Michel (1975, British Journal of Venereal Diseases 51, 257-64), the level of resistance to penicillin among non-PPNG has not significantly increased in The Netherlands since 1972. The prevalence of isolates showing relative resistance towards tetracycline and thiamphenicol (MIC 2-4 mg/l) decreased from approximately 20% in 1983/84 to approximately 10% in 1985/86, coinciding with a drop in the prevalence of Pro- isolates. All strains were susceptible to cefuroxime and spectinomycin and highly susceptible to cefotaxime and ciprofloxacin.
The relationship between auxotype, plasmid pattern and susceptibility to antibiotics has been studied in 2396 penicillinase-producing Neisseria gonorrhoeae isolated in The Netherlands during 1982 and 1983. The most prevalent auxotypes were proline requiring (Pro-; 44%) and non-requiring with inhibition by phenylalanine (NR Pheni; 39%). The majority (97%) of the Pro- strains carried the 4.5 Mdal resistance plasmid and 99% of the prototrophic strains the 3.2 Mdal plasmid. MICs were determined for cefuroxime, cefotaxime, erythromycin, tetracycline, thiamphenicol and sulphamethoxazole. Pro- isolates were usually less susceptible to antibiotics than prototrophic strains. Evidence was obtained that the level of relative resistance is related to the nutritional requirement as well as the plasmid type.
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