E-Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2021

Azithromycin resistant Neisseria gonorrhoeae – has the time come to re-consider use of azithromycin for NG treatment in Australia? (#301)

Bushra Alharbi 1 2 , Amy AJ Jennison 3 , David DW Whiley 1 4 , Ella ET Trembizki 1
  1. The University of Queensland Centre for Clinical Research, Faculty of Medicine, The University of Queensland , Brisbane, Queensland, Australia
  2. Taibah University, Faculty of Pharmacy, Madinah, Saudi Arabia
  3. Queensland Health Forensic and Scientific Services, Brisbane, Queensland, Australia
  4. Pathology Queensland Central Laboratory, Queensland, Australia

Neisseria gonorrhoeae (NG) antimicrobial resistance (AMR) is a global concern. In Queensland, Australia, approximately 25% of infections are diagnosed via bacterial culture (the remainder by nucleic acid amplification tests [NAATs]), leaving a potential gap in AMR surveillance data. Current NG treatment guidelines locally are ceftriaxone 500 mg IM and azithromycin 1 g orally. Azithromycin AMR has been on the rise, and according to the Australian Gonococcal Surveillance Programme (AGSP; 2019) which is based on isolate data, the current Qld azithromycin resistance rate is 1.9%. Azithromycin resistant NG are typically associated with 23S rRNA mutations, however a major azithromycin-resistant clone carrying a meningococcal-type mtrR sequence (henceforth called men-mtrR) - with azithromycin MICs often on the threshold of resistance (MIC 1.0 mg/L) - has recently become widespread in Australia and globally.

Here, we screened for azithromycin resistant NG in NG-NAAT-positive clinical samples from Qld, 2019 (n= 905) using PCR assays specific for the 23S rRNA and men-mtrR mutations. The results were compared to the 2019 culture-based data (n = 1,677 isolates) from the AGSP.

Our assays detected 0.66% (6/905) samples with the 23S rRNA mutations and 4.31% (39/905) of samples with the men-mtrR mutation, providing a combined rate of 4.97% (45/905) across Queensland in 2019. This was significantly higher (p < 0.0001) than the 1.9% detected in cultured isolates (32/1,677 isolates; AGSP).

The fact that these men-mtrR strains now account for nearly 5% of infections in our population is a concern for ongoing use of azithromycin. These men-mtrR strains are also residing on the MIC breakpoint which may explain why they were not all flagged by culture. Nevertheless, these rates raise further questions over the need to consider abandoning azithromycin for first line NG treatment, as has now occurred in the USA and UK. The data further emphasises the potential utility of complementing culture-based surveillance with molecular AMR methods.