PT  - JOURNAL ARTICLE
AU  - Catherine A Ison
AU  - Daniel Golparian
AU  - Pamela Saunders
AU  - Stephanie Chisholm
AU  - Magnus Unemo
TI  - Evolution of <em>Neisseria gonorrhoeae</em> is a continuing challenge for molecular detection of gonorrhoea: false negative gonococcal <em>porA</em> mutants are spreading internationally
AID  - 10.1136/sextrans-2012-050829
DP  - 2013 May 01
TA  - Sexually Transmitted Infections
PG  - 197--201
VI  - 89
IP  - 3
4099  - http://sti.bmj.com/content/89/3/197.short
4100  - http://sti.bmj.com/content/89/3/197.full
SO  - Sex Transm Infect2013 May 01; 89
AB  - Objectives Identification of genetic targets specific to Neisseria gonorrhoeae for use in molecular detection methods has been a challenge. The porA pseudogene in N gonorrhoeae has been commonly used but recently gonococcal isolates giving a negative result in these PCRs have been reported. Here we describe the characterisation of two such gonococcal isolates received by the reference service at the Health Protection Agency, London, England. Methods Phenotypic characterisation was achieved using conventional biochemical and immunological tests, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS), antimicrobial susceptibility testing, serovar determination and detection of meningococcal PorA using monoclonal antibody 4BG4-E7. Genetic species confirmation was determined using commercial and in house PCRs and 16S rRNA gene sequencing. Molecular typing using the N gonorrhoeae multi-antigen sequence typing (NG-MAST) and multilocus sequence typing (MLST) was performed. The DNA sequence of the full-length gonococcal porA pseudogene was determined and compared with published sequences. Results Both isolates were confirmed, biochemically and immunologically as N gonorrhoeae, but repeatedly gave negative results with two in house real-time PCR assays for the porA pseudogene. Further characterisation of these isolates identified the presence of a meningococcal porA sequence and showed these isolates belong to serovar Bropyst, and to NG-MAST sequence type (ST) 5967 and MLST ST1901. Conclusions Gonococcal isolates that give false negative results with porA pseudogene PCR assays have now been identified in four countries, three of which are in Europe, and do not appear clonal. This report highlights the genetic diversity of N gonorrhoeae, which remains a challenge for the molecular detection methods.