Abstract

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

Methods: Antibiotic susceptibility testing and typing was performed on all N. gonorrhoeae isolated in Scotland over a two 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 (PPNG), 8.4% were tetracycline resistant N. gonorrhoeae (TRNG), 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 (STs), 169 contained 2-85 isolates accounting for 1526 isolates. The overall concordance between ST and antibiotic susceptibility category was 98.1 %, 95% CI (97.8, 98.3). The concordance for penicillin (chromosomal and plasmid mediated resistance) was 97.1%, 95% CI (96.1, 97.8), for ciprofloxacin was 99.5%, 95% CI (99.1, 99.8), for azithromycin was 97.8%, 95% CI (96.9, 98.5) and for tetracycline (chromosomal and plasmid mediated resistance) was 92.0%, 95% CI (90.5, 93.3).

Conclusions: Antibiotic resistance in Neisseria gonorrhoeae was usually uniform within a given sequence type. Therefore the ST 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 STs are required.