Background/introduction In the last four years, isolates of N. gonorrhoeae have been identified in Australia, Sweden, Scotland and England which lack the gonococcal porA pseudogene and consequently result in negative results in the diagnostic porA pseudogene real-time-PCR (RT-PCR) for N. gonorrhoeae.
Aim(s)/objectives This study sought to determine the prevalence of porA pseudogene negative isolates amongst isolates received at Public Health England (PHE) through the national gonococcal resistance to antimicrobials surveillance programme (GRASP).
Methods DNA lysates were prepared from 533 N. gonorrhoeae isolates received from 20 centres via GRASP during 2011. Any isolate with a RT-PCR por A pseudogene negative result was repeated from a fresh culture and the porA gene was additionally DNA sequenced. Isolates were additionally tested using the gonococcal opa gene RT-PCR.
Results Four isolates (4/533, 0.8%) were found to be reproducibly negative with the porA pseudogene RT-PCR, but were positive with opa gene RT-PCR. DNA sequencing determined that two isolates contained the Neisseria meningitidis porA gene. Both isolates were from patients attending a clinic in SouthLondon.
Discussion/conclusion Less than one percent of the GRASP isolates from patients attending clinics across England expressed the meningococcal porA gene and therefore tested negative on the in-house porA assay. The low prevalence indicates that these isolates do not present a major diagnostic or public health problem. However, microbiologists should remain vigilant for any isolates giving anomalous results and when using the porA pseudogene RT-PCR consider multiplexing it with the opa-gene RT-PCR.
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