Antimicrobial susceptibility testing of Neisseria gonorrhoeae: a trial organised as part of the United Kingdom national external quality assessment scheme for microbiology.

Six strains of Neisseria gonorrhoeae were distributed to 411 United Kingdom laboratories who were asked to test the susceptibility of the strains to penicillin, cefuroxime, tetracycline and spectinomycin and to test for production of beta-lactamase. Details of methods used were requested by means of a questionnaire. The number of reports recording sensitive strains as resistant was 5% for penicillin, 0.7% for cefuroxime, 3% for tetracycline and 4% for spectinomycin. The number of reports recording resistant strains as sensitive was 7% for penicillin (0.2% with beta-lactamase producing strains, 20% with non-beta-lactamase producing strains), 96% for cefuroxime, 76% for tetracycline and 8% for spectinomycin. There was an association between greater error rates and the use of high content discs for testing tetracycline, the use of low content discs for testing spectinomycin, failure to dilute the inoculum, and use of acidimetric methods rather than methods that use a chromogenic cephalosporin for detecting beta-lactamase.