JCM Figure table search 04
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Tapsall, J. W.
Right arrow Articles by Chambers, I. W.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Tapsall, J. W.
Right arrow Articles by Chambers, I. W.

 Previous Article  |  Next Article 

Journal of Clinical Microbiology, April 2005, p. 2036-2037, Vol. 43, No. 4
0095-1137/05/$08.00+0     doi:10.1128/JCM.43.4.2036-2037.2005

LETTER TO THE EDITOR

Cryptic-Plasmid-Free Gonococci May Contribute to Failure of cppB Gene-Based Assays To Confirm Results of BD ProbeTEC PCR for Identification of Neisseria gonorrhoeae


   LETTER
Top
 Letter
References
 
We note the recent article by Koenig et al. (3) which describes discordance between results obtained with the BD ProbeTEC ET System (BDPT) and a cppB gene-based PCR assay for the detection of Neisseria gonorrhoeae. Overall, 22.6% of BDPT-positive assays were not confirmed by the cppB gene-based PCR, but agreement was particularly low in those samples producing a reduced method-other-than-acceleration score with the BDPT PCR. The BDPT PCR has been found to cross-react with commensal Neisseria species (5), but such cross-reactions may not adequately explain the high level of nonconfirmed BDPT PCR-positive results obtained in this study. Even with samples with method-other-than-acceleration scores in higher ranges (>20,000), between 6 and 15.5% of positive BDPT PCR results could not be confirmed with the cppB gene-based assay. The authors discussed, among a number of potential reasons for the discrepancy, the possibility that the presence of gonococci lacking the cryptic plasmid where the cppB gene is located may account for this difference. This possibility was disregarded on the basis of studies reporting that 96% of gonococci contained a cryptic plasmid and that even where this plasmid was absent, amplification of a cppB gene sequence replicated in the chromosome may produce the required positive result.

Recent studies suggest this confidence in cppB gene-based assays may be misplaced. We have recently reported that 10% of culture-positive gonococci were cppB gene-based PCR negative but positive in other assays, including the BDPT PCR (4; J. Tapsall, A. Limnios, I. Carter, G. Lum, K. Freeman, and T. Sloots, Abstr. 15th Biennial Congr. Int. Soc. Sex. Transm. Dis. Res., abstr. 0129, 2003). It is known that cryptic-plasmid-free gonococci may vary widely in prevalence in time and place and occur among diverse gonococcal subtypes and specifically that a high incidence of plasmid-free gonococci has been documented in Germany (1, 4). Further, considerable recombination occurs within the DNA of the plasmid and some cppB gene sequences present in the chromosome were incomplete and in low copy numbers (6, 7). It is thus not surprising that some decreased sensitivity with cppB gene-based nucleic acid amplification, arising from absent, altered, or low copy numbers of the chosen sequence, has now been acknowledged with different forms of this test (2, 9).

We thus concluded (4) that other nucleic acid amplification (8, 9) are preferable to the problematic cppB gene-based assays. If the cppB gene-based PCR is employed as either a diagnostic or supplemental assay for diagnosis of gonorrhoeae, its use should be contingent upon ongoing assessment of the proportion of gonococci lacking this target site by means of evaluations which directly assess both culture and PCR performance. It is therefore suggested that Koenig et al. should consider conducting such a study and also that it is possible that an additional explanation for the discrepant results is that some of the supposedly false-positive results in the BDPT PCR may have been true positives but not recognized by a false-negative cppB gene-based PCR.


   FOOTNOTES
 
Ed. Note: The authors of the published article did not feel a response was warranted at this time.


   REFERENCES
Top
 Letter
 References
 

  1. Abeck, D., A. P. Johnson, F. E. Alexander, F. E., H. C. Korting, and D. Taylor-Robinson. 1988. Plasmid content and protein I serovar of non-penicillinase-producing gonococci isolated in Munich. Epidemiol. Infect. 100:345-349.[Medline]
  2. Bruisten, S. M., G. T. Noordhoek, A. J. C. van den Brule, B. Duim, C. H. E. Boel, K. El-Faouzi, R. du Maine, S. Mulder, D. Luijt, and J. Schirm. 2004. Multicentre validation of the cppB gene as a PCR target for detection of Neisseria gonorrhoeae. J. Clin. Microbiol. 42:4332-4334.[Abstract/Free Full Text]
  3. Koenig, M. G., S. L. Kosha, B. L. Doty, and D. G. Heath. 2004. Direct comparison of the BD ProbeTec ET system with in-house LightCycler PCR assays for detection of Chlamydia trachomatis and Neisseria gonorrhoeae from clinical specimens. J. Clin. Microbiol. 42:5751-5756.[Abstract/Free Full Text]
  4. Lum, G., K. Freeman, N. L. Nguyen, E. A. Limnios, S. N. Tabrizi, I. Carter, I. W. Chambers, D. M. Whiley, T. P. Sloots, S. M. Garland, and J. W. Tapsall. A cluster of culture positive gonococcal infections but with false-negative cppB gene based PCR. Sex. Transm. Infect., in press.
  5. Palmer, H. M., H. Mallinson, R. L. Wood, and R. J. Herring. 2003. Evaluation of the specificities of five DNA amplification methods for the detection of Neisseria gonorrhoeae. J. Clin. Microbiol. 41:835-837.[Abstract/Free Full Text]
  6. Rosson, S., E. de Gooyer, A. Moore, J. Morcom, and J. K. Davies. 1985. Site-specific recombination systems in gonococcal plasmids, p. 175-179. In G. K. Schoolnik, G. F. Brooks, S. Falkow, C. E. Frasch, J. S. Knapp, J. A. McCutchan, and S. A. Morse (ed.) The pathogenic neisseriae. American Society for Microbiology, Washington, D.C.
  7. Sarandopoulos, S., and J. K. Davies. 1993. Lack of substantial sequence homology between the cryptic plasmid and chromosome of Neisseria gonorrhoeae. Plasmid 29:41-49.[Medline]
  8. Tabrizi S.N., S. Chen, J. Tapsall, and S. Garland. 2005. Evaluation of opa-based real time PCR for detection of N. gonorrhoeae. Sex. Transm. Dis. 32:199-202.[CrossRef][Medline]
  9. Whiley, D. M., P. J. Buda, J. Bayliss, L. Cover, J. Bates, and T. P. Sloots. 2004. A new confirmatory Neisseria gonorrhoeae real-time PCR assay targeting the porA pseudogene. Eur. J. Clin. Microbiol. Infect. Dis. 23:705-710.[Medline]
J. W. Tapsall*
E. A. Limnios
N. L. Nguyen
I. Carter
Microbiology Department
South Eastern Area Laboratory Services
Prince of Wales Hospital
Randwick, Sydney, Australia 2031

G. Lum
K. Freeman
Microbiology Laboratory
NT Government Pathology Services
Royal Darwin Hospital
Tiwi, Northern Territory, Australia

S. N. Tabrizi
S. M. Garland
Department of Microbiology
Royal Women's Hospital
Melbourne, Victoria, Australia

D. M. Whiley
T. P. Sloots
Clinical Virology Research Unit
Sir Albert Sakzewski Virus Research Centre
Royal Children's Hospital and Health Service District
Brisbane, Queensland, Australia

I. W. Chambers
Douglass Hanly Moir Pathology
Ryde, New South Wales, Australia

* Phone: 61-2-9382-9079, Fax: 61-2-9398-4275 E-mail: j.tapsall{at}unsw.edu.au

Journal of Clinical Microbiology, April 2005, p. 2036-2037, Vol. 43, No. 4
0095-1137/05/$08.00+0     doi:10.1128/JCM.43.4.2036-2037.2005




This article has been cited by other articles:


This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Tapsall, J. W.
Right arrow Articles by Chambers, I. W.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Tapsall, J. W.
Right arrow Articles by Chambers, I. W.

Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
Antimicrob. Agents Chemother. Clin. Microbiol. Rev.
Clin. Vaccine Immunol. ALL ASM JOURNALS