(P56) Evaluation of the Allplex NG&DR Assay for molecular detection and prediction of ciprofloxacin and azithromycin resistance in Neisseria gonorrhoeae

Background

We investigated the molecular detection of Neisseria gonorrhoeae (Ng) and prediction of ciprofloxacin (CIP) and azithromycin (AZI) resistance directly from clinical specimens, using the molecular, CE-IVD marked Allplex NG&DR Assay (NG&DR Assay, Seegene). The NG&DR Assay simultaneously detects Ng and the molecular resistance determinants, S91F for CIP resistance, and C2611T, A2059G for AZI resistance. Due to the fastidious nature of Ng, phenotypic antimicrobial susceptibility testing (AST) is often neglected in clinical practice as results are rarely available in time to inform therapeutic decisions.

Methods

Overall, 201 specimens (106 urogenital-, 3 extra-urogenital-, and 45 pooled swabs and 47 urines) were routinely tested for sexually transmitted infections, including Ng, from June 2021 to December 2022. The specimens were further analyzed with the NG&DR Assay, using the in-house SYBR-Green Assay as the reference method. Clinical isolates were cultured from 34 specimens, for which AST was performed by E-testes (BioMérieux), including CIP and AZI.

Results

Out of 201 specimens, 121 were Ng positive, 77 Ng negative and three were invalid with the NG&DR Assay. The sensitivity and specificity for Ng detection were 94.5% (95%CI: 89.1-97.8%) and 100% (95%CI: 94.9-100.0%), respectively. For 18 targets (13 S91F, 2 A2059G and 5 C2611T) no sequencing results were available. Positive- and negative percent agreement between the assays were 98.6% (95%CI: 92.2-100.0%) and 100.0% (95%CI 91.0-100.0%) for S91F and 75.0% (95%CI: 34.9-96.8%) and 100.0% (95%CI: 96.6-100.0%) for C2611T, respectively. For A2059G, no mutation was detected. The negative percent agreement was 100% (96.7-100.0%). Compared to the CIP phenotype, the sensitivity and specificity of the NG&DR Assay were both 100.0% (95%CI: 88.8-100.0%, 95%CI: 29.2-100.0%). In contrast, the sensitivity and specificity of predicting the AZI phenotype were 75.0% (95%CI: 19.4-99.3%) and 100.0% (95%CI: 88.4-100.0%), respectively.

Conclusion

The NG&DR Assay allows rapid molecular detection of Ng and three molecular resistance determinants. While the concordance with the CIP phenotype was high, it was less pronounced for the AZI phenotype. Since AZI resistance involves several independent resistance mechanisms, inclusion of more than two molecular resistance determinants may be required to accurately predict AZI resistance phenotype, depending on the epidemiology of Ng strains circulating in the population studied.