Improved determination of Neisseria gonorrhoeae gyrase A genotype results in clinical specimens.

Background: The emergence of drug-resistant Neisseria gonorrhoeae has prompted the development of rapid molecular assays designed to determine antimicrobial susceptibility. One common assay uses high-resolution melt analysis to target codon 91 of the gyrase A gene (gyrA) to predict N. gonorrhoeae susceptibility to ciprofloxacin.

Methods: We extracted DNA from remnant clinical specimens that had previously tested positive for N. gonorrhoeae using the Aptima Combo 2 for CT/NG assay (Hologic, San Diego, CA, USA). We selected DNA extracts from specimens with indeterminate, WT and mutant gyrA genotype results from a previous study using high-resolution melt analysis to detect the gyrA codon 91 mutation. We re-tested those specimens using the recently CE-marked ResistancePlus GC (beta) assay (SpeeDx, Sydney, Australia).

Results: Of 86 specimens with indeterminate gyrA genotypes on high-resolution melt analysis, the ResistancePlus GC (beta) assay (SpeeDx) identified 30 (35%) WT, 22 (26%) mutant and 34 (40%) indeterminate gyrA genotypes.

Conclusions: The ResistancePlus GC (beta) assay showed improved N. gonorrhoeae gyrA genotype determination compared with a prior gyrA genotypic high-resolution melt assay.