Molecular epidemiology of Neisseria gonorrhoeae using multi-antigen sequence typing and pulse-field gel electrophoresis in highly endemic Western Australian populations.

BACKGROUND: The remote and indigenous populations of Western Australia (WA) have one of the highest notification rates of gonorrhoea in the world. Despite this, the low rate of antimicrobial resistance in Neisseria gonorrhoeae from these regions permits the use of amoxycillin as empirical therapy. We describe the first molecular epidemiological study of gonococci isolated from this population using two different typing platforms. METHODS: Pulse-field gel electrophoresis (PFGE), Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST) and antimicrobial susceptibility tests were performed on 128 consecutive N. gonorrhoeae isolates cultured between January 2011 and December 2013. To highlight clusters isolates were evaluated based on their tbpB sequence types. RESULTS: No predominant NG-MAST or PFGE types were found. A total of 67 distinct PFGE pulsotypes were identified amongst the 128 isolates in this study with 20 PFGE pulsotypes representing 78 isolates. A total of 59 NG-MAST sequence types were found, represented by 45 porB alleles and 28 tbpB alleles with 13 tbpB genomogroups from 45 NG-MAST sequence types. TbpB genomogroup 29, represented by 45 isolates, was by far the most common genomogroup overall. CONCLUSIONS: Results from this study suggest that gonococcal epidemiology in WA is quite different between remote regions and major population centres and, in some cases, geographically restricted. It is likely that isolates originating from endemic regions of WA mostly represent independent, small sexual networks with an infrequent interchange between other communities and regions. Given the high rate of antimicrobial resistance elsewhere in Australia, ongoing surveillance is essential to ensure the enduring efficacy of amoxycillin empiric use in the remote regions of WA.

Non-culture Neisseria gonorrhoeae molecular penicillinase production surveillance demonstrates the long-term success of empirical dual therapy and informs gonorrhoea management guidelines in a highly endemic setting.

OBJECTIVES: Unlike most of the world, penicillin resistance in Neisseria gonorrhoeae from remote regions of Western Australia (WA) with high gonorrhoea notification rates has not increased despite many years of empirical oral therapy. With the advent of non-culture molecular diagnosis of gonorrhoea and the consequent decline in culture-based susceptibility, it is imperative to ensure the ongoing reliability of combination oral azithromycin, amoxicillin and probenecid for uncomplicated gonorrhoea in this setting. PCR-based non-culture N. gonorrhoeae antimicrobial resistance surveillance for penicillinase production was therefore employed. METHODS: Genital and non-genital specimens that were PCR-positive for N. gonorrhoeae were assessed for penicillinase production by detection of the N. gonorrhoeae TEM-1 plasmid using specific real-time PCR. RESULTS: In remote regions of WA where gonorrhoea is highly endemic, <5% of N. gonorrhoeae isolates were penicillinase-producing. This contrasts with rates of up to 20% observed in the more densely populated metropolitan and rural regions. CONCLUSIONS: In the era of molecular diagnosis of gonorrhoea, non-culture-based antimicrobial resistance surveillance proved useful when developing evidence-based guidelines for the clinical management of locally acquired gonorrhoea in highly endemic regions in WA. The continued efficacy of combination oral amoxicillin, probenecid and azithromycin therapy despite many years of use in a setting highly endemic for gonorrhoea may explain the low rate of penicillin resistance in these remote regions and supports the concept of adding azithromycin to ß-lactam antibiotics to help delay the emergence of multiresistant N. gonorrhoeae.