Prediction of antibiotic resistance using Neisseria gonorrhoeae multi-antigen sequence typing.

OBJECTIVES: To establish whether antibiotic resistance in Neisseria gonorrhoeae is uniform within a given sequence type as determined by N gonorrhoeae multi-antigen sequence typing (NG-MAST).

METHODS: Antibiotic susceptibility testing and typing was performed on all N gonorrhoeae isolated in Scotland over a 2-year period. Antibiotic susceptibility to seven antibiotics was determined using the agar dilution method and NG-MAST was performed.

RESULTS: Isolates from 1762 episodes of infection were tested, of which 8.0% were penicillinase-producing N gonorrhoeae, 8.4% were tetracycline-resistant N gonorrhoeae, 2.7% had chromosomal penicillin resistance, 30.5% had chromosomal tetracycline resistance, 2.0% had decreased susceptibility to azithromycin and 25.3% were ciprofloxacin resistant (including 1.7% with intermediate resistance). Resistance to spectinomycin or decreased susceptibility to ceftriaxone or cefixime was not observed. Of 405 sequence types, 169 contained two to 85 isolates accounting for 1526 isolates. The overall concordance between sequence type and antibiotic susceptibility category was 98.1% (95% CI 97.8 to 98.3). The concordance for penicillin (chromosomal and plasmid-mediated resistance) was 97.1% (95% CI 96.1 to 97.8), for ciprofloxacin it was 99.5% (95% CI 99.1 to 99.8), for azithromycin it was 97.8% (95% CI 96.9 to 98.5) and for tetracycline (chromosomal and plasmid-mediated resistance) it was 92.0% (95% CI 90.5 to 93.3).

CONCLUSIONS: Antibiotic resistance in N gonorrhoeae was usually uniform within a given sequence type. Therefore the sequence type of an isolate allows the presence of antibiotic resistance to be predicted with a high degree of accuracy. Further studies on the geographical variation and temporal stability of antibiotic susceptibility patterns within sequence types are required.