Direct detection of markers associated with Neisseria gonorrhoeae antimicrobial resistance in New Zealand using residual DNA from the Cobas 4800 CT/NG NAAT assay

Objectives To use nucleic acid amplification techniques (NAAT) for detection of markers associated with gonococcal antimicrobial resistance (AMR) in non-cultured clinical samples to enhance surveillance of Neisseria gonorrhoeae AMR in New Zealand. Methods A total of 198 clinical samples from patients living in two cities, Wellington and Auckland and the more rural region of Gisborne, New Zealand, which were positive for N. gonorrhoeae by the Cobas 4800 were tested for three markers that predict reduced susceptibility or resistance to three antibiotics. Residual DNA extracts from the Cobas 4800 NG/CT test were tested for a single-nucleotide polymorphism in the gyrA gene at codon 91 associated with quinolone resistance; a sequence on the plasmid in penicillinase-producing N. gonorrhoeae (PPNG) which confers resistance to penicillin and the mosaic penA sequence associated with reduced susceptibility to extended-spectrum cephalosporins in N. gonorrhoeae. Results A total of 186/198 (94%) of the samples provided a valid result on gyrA genotyping, confirming the utility of N. gonorrhoeae DNA extracted by the Roche Cobas 4800 CT/NG test for subsequent detection of AMR markers. The NAAT results for Wellington, Auckland and Gisborne, respectively, showed that 77%, 33% and 32% of samples had the marker associated with quinolone resistance, while 4%, 15% and 0% were positive for the PPNG plasmid marker, and 9%, 5% and 0% samples were positive for mosaic penA sequence. Conclusions The use of residual clinical DNA samples from the Cobas 4800 CT/NG test proved an efficient and effective method for performing AMR genotyping. These data also show for the first time the presence of gonococci with a mosaic penA sequence in New Zealand. Overall, the results further highlight the potential of molecular methods to aid N. gonorrhoeae AMR surveillance, particularly for regions where gonococcal culture is no longer performed.