Invited Speaker Australian Society for Microbiology Annual Scientific Meeting 2018

Rapid Laboratory responses to ceftriaxone-resistant Neisseria gonorrhoeae; on behalf of the National Neisseria Network, Australia. (#69)

Ella Trembizki 1 , Amy Jennison 2 , Graeme Nimmo 3 , Monica Lahra 4 5 , David Whiley 1 3
  1. The university of Queensland Centre for Clinical Research (UQCCR), Brisbane, QLD, Australia
  2. Public Health Microbiology, Queensland Health Forensic and Scientific Services, Brisbane, Queensland, Australia
  3. Pathology Queensland , Brisbane, Queensland
  4. New South Wales Health Pathology Microbiology, WHO Collaborating Centre for STD, Randwick, New South Wales, Australia
  5. School of Medical Sciences, The University of New South Wales, Sydney, New South Wales, Australia

Background: Ceftriaxone and azithromycin dual therapy is the recommended treatment for gonorrhoea in most settings. In the recent months, there have been four clinical isolates of N. gonorrhoeae detected resistant to ceftriaxone, two of which had high level resistance to azithromycin. We characterised the isolates via whole genome sequencing (WGS) and developed a rapid PCR method for direct screening of clinical samples to detect the ceftriaxone resistance mechanism .

Methods: WGS and bioinformatics analysis for in silico genotyping, resistance genes and core genome MLST was conducted at the Queensland Health Forensic and Scientific Services to assess strain relatedness and to identify mechanisms of resistance. We used these sequencing data to develop a real-time PCR assay to detect the characteristic alterations associated with ceftriaxone resistance in these four strains. Following validation, the assay was applied to N. gonorrhoeae-positive PCR clinical samples from Queensland, and NSW collected in 2018 (n=approx. 800 and ongoing, provided by Pathology Queensland and the WHO CC for STD, NSW).

Results: WGS determined that the four isolates harboured the same ceftriaxone resistance mechanism, involving specific alteration of a 'type 60' penA allele. The four isolates comprised two different MLST types, ST1903 and ST12039, with the latter ST12039 isolates also harbouring the 23S gene A2059G alteration conferring high-level resistance to azithromycin. All clinical samples screened with the real-time PCR assay for the year 2018 have so far provided negative results suggesting no further spread in Queensland at this stage.

Discussion: These rapid responses to new incursions of antibiotic resistant organisms of public health concern to provide enhanced and timely information for surveillance and enable enhanced detection and to determine spread. The NNN continues to perform enhanced testing across jurisdictions as part of the outbreak investigation.