Molecular detection of ceftriaxone resistance in Neisseria gonorrhoeae clinical specimens: a tool for public health control

Objectives

This study aimed to validate and implement a rapid screening assay for molecular detection of the penA-60 allele that is associated with ceftriaxone resistance in Neisseria gonorrhoeae for use on both isolate lysates and clinical specimen DNA extracts.

Methods

A N. gonorrhoeae penA real-time (RT)-PCR was adapted to include a species-specific papconfirmation target and a commercially available internal control to monitor for PCR inhibition. The modified assay was validated using N. gonorrhoeae positive (n=24) and N. gonorrhoeae-negative (n=42) clinical specimens and isolate lysates. The panel included seven samples with resistance conferred by penA alleles targeted by the assay and four samples with different penA alleles. The feasibility of using the penA RT-PCR for molecular surveillance was assessed using clinical specimens from 54 individuals attending a London sexual health clinic who also had a N. gonorrhoeae isolate included in the 2020 Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP).

Results

The assay correctly identified N. gonorrhoeae specimens (n=7) with penA-60/64 alleles targeted by the assay. No penA false negatives/positives were detected, giving the penA target of the assay a sensitivity, specificity, positive and negative predicted values (PPV, NPV) of 100% (95% CIs; sensitivity; 56.1–100%, specificity; 93.6–100%, PPV; 56.1–100%, NPV; 93.6–100%).No cross-reactivity with other Neisseria species or other urogenital pathogens was detected. The N. gonorrhoeae target (pap) was detected in 73 out of 78 of the N. gonorrhoeae-positive specimens, resulting in 92.6% sensitivity (95%CI 83.0% to 97.3%), 100% specificity (95%CI 75.9% to 100%) and PPV, and a NPV of 89.4% (95% CI 52.5% to 90.9%). No penA-59/60/64 alleles were detected within the clinical specimens from the GRASP 2020 feasibility molecular surveillance study (n=54 individuals).

Conclusions

The implementation of this PCR assay for patient management, public health and surveillance purposes enables the rapid detection of gonococcal ceftriaxone resistance conferred by the most widely circulating penA alleles