Laboratory evaluation of the Allplex NG & DR assay for detection of Neisseria gonorrhoeae and associated azithromycin and ciprofloxacin resistance markers

Objectives Rapid and accurate detection of antimicrobial resistance in Neisseria gonorrhoeae is key for appropriate treatment of gonorrhoea. Nucleic acid amplification tests are increasingly available for the detection of N. gonorrhoeae and antimicrobial resistance markers from clinical samples. This study evaluated the Allplex NG & DR assay for the detection of N. gonorrhoeae and resistance markers against ciprofloxacin ( gyrA S91F) and azithromycin (23S rRNA A2059C and C2611T). Methods This was a retrospective diagnostic accuracy study performed in two centres. We evaluated assay inclusivity with a panel of laboratory strains, specificity with 35 N . gonorrhoeae negative clinical samples and sensitivity with 82 N . gonorrhoeae positive samples with a matched culture isolate to allow comparison of resistance calls. The Alinity m STI assay was considered gold standard for N. gonorrhoeae detection, and agar incorporation minimum inhibitory concentration testing of N. gonorrhoeae isolates was considered gold standard for resistance calling. Comparisons were also made to the ResistancePlus GC assay which detects N. gonorrhoeae and the S91F ciprofloxacin resistance marker. Results The Allplex NG & DR assay performed well in the inclusivity panel and had high sensitivity and specificity for the detection of N. gonorrhoeae in clinical samples (98.8% and 100%, respectively). For resistance detection, sensitivity and specificity were >97%. The Allplex NG & DR assay generated one ciprofloxacin resistance marker false negative due to the presence of the S91I gyrA mutation. Two azithromycin resistance marker false positive calls were identified due to the presence of the 23S rRNA C2611T mutation in phenotypically sensitive cases. Conclusions Our retrospective study shows the Allplex NG & DR assay performed well in the detection of N. gonorrhoeae and associated azithromycin and ciprofloxacin resistance mutations.