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Neisseria gonorrhoeae multi-antigen sequence typing using non-cultured clinical specimens
  1. David M Whiley1,2,
  2. Namraj Goire1,2,
  3. E Sanghamitra Ray3,
  4. Athena Limnios3,
  5. Stephen B Lambert1,2,
  6. Michael D Nissen1,2,4,
  7. Theo P Sloots1,2,4,
  8. John W Tapsall3
  1. 1Queensland Paediatric Infectious Diseases Laboratory, Sir Albert Sakzewski Virus Research Centre, Queensland Children's Medical Research Institute, Children's Health Service District, Queensland, Australia
  2. 2Clinical Medical Virology Centre, University of Queensland, Queensland, Australia
  3. 3WHO Collaborating Centre for STD and HIV, Microbiology Department, South Eastern Area Laboratory Services, Prince of Wales Hospital, Sydney, New South Wales, Australia
  4. 4Microbiology Division, Pathology Queensland Central, Royal Brisbane and Women's Hospital Campus, Queensland, Australia
  1. Correspondence to Dr David M Whiley, Queensland Paediatric Infectious Diseases Laboratory, Sir Albert Sakzewski Virus Research Centre, Royal Children's Hospital and Health Service District, Herston Road, Herston, Queensland 4029, Australia; d.whiley{at}uq.edu.au

Abstract

Objectives The Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST) system, based on PCR amplification and sequence analysis of the gonococcal porB and tbpB genes, is widely used for molecular typing of gonococcal isolates but is not validated for non-cultured clinical samples. This study sought to examine the performance of the NG-MAST system on a range of non-cultured samples.

Methods Nucleic acid extracts of 73 N gonorrhoeae-positive samples, comprising eight cervical swabs, nine urethral swabs, 35 urine samples, one vaginal swab, 13 rectal swabs and seven throat swabs, were analysed by NG-MAST. For 27 specimens, corresponding gonococcal isolates were also analysed and the results compared. A panel of 44 non-gonococcal Neisseria strains and 100 N gonorrhoeae-negative clinical samples were used to investigate further the specificity of the NG-MAST PCR reactions.

Results PCR amplification and DNA sequencing of gonococcal porB and tbpB genes was successful for all N gonorrhoeae-positive urogenital specimens, 11 of 13 rectal swabs and four of seven throat swabs. For the 27 N gonorrhoeae-positive specimens with corresponding gonococcal isolates, the porB and tbpB sequences obtained from the non-cultured specimen were identical to those obtained from the isolate. Cross-reaction with non-gonococcal Neisseria species was observed for both the porB and tbpB PCR reactions, and proved to be problematical for NG-MAST typing of throat swab specimens.

Conclusions The NG-MAST system can successfully be applied directly to non-cultured urogenital samples, but is less suitable for extragenital specimens, particularly throat swabs, due to cross-reaction with commensal Neisseria species.

  • molecular typing
  • Neisseria gonorrhoeae
  • typing

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Footnotes

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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