Supplemental testing is still required in Australia for samples positive for Neisseria gonorrhoeae by nucleic acid detection tests [3]

Journal of Clinical Microbiology (Impact Factor: 3.99). 12/2006; 44(11):4292-4; author reply 4293-4. DOI: 10.1128/JCM.01577-06
Source: PubMed
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Available from: Sepehr Tabrizi
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    ABSTRACT: DNA sequencing was used to confirm Chlamydia trachomatis and Neisseria gonorrhoeae nucleic acids in endocervical swab samples. DNA in residues of the samples with positive results by 2 commercial kits was subjected to nested polymerase chain reaction (PCR) amplification. The nested PCR amplicons were used as templates for direct automated DNA sequencing. A 40-base signature sequence was sufficient to achieve unequivocal validation of C trachomatis cryptic plasmid and gonococcal opa gene DNA. DNA with a signature sequence specific for C trachomatis was identified in all 14 samples and for N gonorrhoeae in all 13 samples with positive results by the commercial kits for these 2 microbes. In a low-prevalence population, PCR retesting of 289 samples with initial negative results by a non-nucleic acid amplification assay revealed 3 samples positive for C trachomatis and 2 samples positive for N gonorrhoeae that were missed by the commercial kit. DNA sequencing is a useful tool in validating molecular diagnostics.
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    ABSTRACT: Molecular detection of Neisseria gonorrhoeae in extragenital samples may result in false-positive results due to cross-reaction with commensal Neisseria species or Neisseria meningitidis. This study examined 450 characterized clinical culture isolates, comprising 216 N. gonorrhoeae isolates and 234 isolates of nongonococcal Neisseria species (n = 218) and 16 isolates of other closely related bacteria, with six commercial nucleic acid amplification tests (NAATs). The six NAATs tested were Gen-Probe APTIMA COMBO 2 and APTIMA GC, Roche COBAS Amplicor CT/NG and COBAS 4800 CT/NG tests, BD ProbeTec GC Qx amplified DNA assay, and Abbott RealTime CT/NG test. All assays except COBAS Amplicor CT/NG test where four (1.9%) isolates were not detected showed a positive result with all N. gonorrhoeae isolates (n = 216). Among the 234 nongonococcal isolates examined, initial results from all assays displayed some false-positive results due to cross-reactions. Specifically, the COBAS Amplicor and ProbeTec tests showed the highest number of false-positive results, detecting 33 (14.1%) and 26 (11%) nongonococcal Neisseria isolates, respectively. On the first testing, APTIMA COMBO 2, APTIMA GC, Abbott RealTime, and Roche COBAS 4800 showed lower level of cross-reactions with five (2.1%), four (1.7%), two (1%), and two (1%) of the isolates showing low-level positivity, respectively. Upon retesting of these nine nongonococcal isolates using freshly cultured colonies, none were positive by the APTIMA COMBO 2, Abbott RealTime, or COBAS 4800 test. In conclusion, the COBAS Amplicor and ProbeTec tests displayed high number of false-positive results, while the remaining NAATs showed only sporadic low-level false-positive results. Supplementary testing for confirmation of N. gonorrhoeae NAATs remains recommended with all samples tested, in particular those from extragenital sites.
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    ABSTRACT: The study aimed to examine the trends in notification and testing for genital gonorrhoea (Neisseria gonorrhoeae) in the Darwin Remote District of Northern Territory, Australia, between 2004 and 2008. Using laboratory testing data and notification data, we calculated the annual sex- and age-specific notification rates, testing rates and positivity rates, and examined their trends. A deterministic matching method was used to identify unique individuals tested in order to estimate the number of years out of five in which each individual was tested. The correlation between testing rates and notification rates was calculated. The notification rates for the 15-24 year age group increased sharply from 2004 to 2005, and then trended downwards between 2005 and 2008, with a decrease of 48.2% in females and 59.9% in males. No evident trends were found in testing rates. The positivity rates for this age group decreased by 46.3% in females (from 8.9% to 4.8%), and by 70.4% in males (from 10.8% to 3.2%) between 2004 and 2008. Over 76% of the population in this age-group had been tested at least once during the study period. A moderate correlation was found between notification rates and testing rates in both sexes. There was a significant decreasing trend in the notification rate of gonorrhoea between 2005 and 2008, which was most probably due to a decrease in prevalence. This study demonstrates the importance and utility of population-level testing data in understanding the epidemiology of common bacterial sexually transmissible infections such as gonorrhoea.
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