Analysis of trends in antimicrobial resistance in Neisseria gonorrhoeae isolated in Australia, 1997-2006

Objectives: To analyse trends in antimicrobial resistance (AMR) in Neisseria gonorrhoeae (GC) isolated in Australia between 1997 and 2006 and to identify factors influencing emergence and spread of AMR in GC. Methods: AMR data were generated in reference laboratories in each state and territory of Australia using the methods of the Australian Gonococcal Surveillance Programme from a comprehensive sample of GC. Trends in the proportion of strains resistant to penicillin, ciprofloxacin, spectinomycin and ceftriaxone or with high-level tetracycline resistance (TRNG) were determined from aggregated national data and were also disaggregated by region. Further analyses of additional AMR, demographic, transmission and antibiotic use data were also performed. Results: More than 36 000 GC were examined. Significant increases in resistance to penicillin and ciprofloxacin and in TRNG occurred in national data and in urban populations. Approximately half of the GC tested in larger urban centres were penicillin and/or ciprofloxacin resistant by 2006. These high rates of resistance arose despite low (penicillin) or absent (ciprofloxacin) exposure. In contrast, in rural and remote areas with very high disease rates and high rates of penicillin use, < 5% of GC tested were penicillin (or quinolone) resistant. No spectinomycin-resistant GC were detected. Low numbers of GC with raised MICs of ceftriaxone were present in urban centres each year from 2001 onwards. Conclusions: Significant increases in AMR in GC occurred in parts of Australia in the 10 years to 2006. The data suggest that the AMR seen in GC in urban populations were the result of their repeated importation into Australia and ultimate introduction into established sexual networks rather than originating de novo or as a result of selection by antibiotic use or misuse.