Neisseria gonorrhoeae Cepheid Diagnostic Escape Mutant Strains: Now available from NCTC

In June 2025 UKHSA identified a Neisseria gonorrhoeae strain that produced a false‑negative result on the Cepheid Xpert® CT/NG test. The patient was successfully treated, and no onward transmission was identified. However, whole genome sequencing revealed the strain was missing both genetic targets required for detection by the assay, due to a recombination event with Neisseria meningitidis. Further screening of large UK and global genome collections revealed three additional strains of UK origin which would also evade detection on the Cepheid platform: one from 2016 and genetically indistinguishable from the 2025 strain, and two from 2020, each lacking one of the two necessary diagnostic targets. Indicating that such diagnostic escape events have occurred on at least three occasions independently. Although these mutants are not currently thought to be widespread in England, laboratories and clinics are advised to remain alert to unusual or conflicting test results.

These N. gonorrhoeae strains of diagnostic importance have recently been deposited into the NCTC catalogue to ensure they are available to the scientific community. It is hoped that by making them accessible, both public health surveillance and international collaboration will be strengthened. Open access to these strains is vital for maintaining diagnostic accuracy and ensuring preparedness against future assay‑escape variants.

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Reference

• Jansen van Rensburg M, Pitt-Kendall R, Hincke M, et al. Detection and characterisation of Xpert CT/NG assay Neisseria gonorrhoeae diagnostic escape mutants, England, June 2025. Euro Surveill. 2025;30(36):2500673. doi:10.2807/1560-7917.ES.2025.30.36.2500673

by Dr Sarah Alexander

STI Reference Lab Unit Head