A new confirmatory Neisseria gonorrhoeae real-time PCR assay targeting the porA pseudogene.
ABSTRACT The Roche Cobas Amplicor system is widely used for the detection of Neisseria gonorrhoeae but is known to cross react with some commensal Neisseria spp. Therefore, a confirmatory test is required. The most common target for confirmatory tests is the cppB gene of N. gonorrhoeae. However, the cppB gene is also present in other Neisseria spp. and is absent in some N. gonorrhoeae isolates. As a result, laboratories targeting this gene run the risk of obtaining both false-positive and false-negative results. In the study presented here, a newly developed N. gonorrhoeae LightCycler assay (NGpapLC) targeting the N. gonorrhoeae porA pseudogene was tested. The NGpapLC assay was used to test 282 clinical samples, and the results were compared to those obtained using a testing algorithm combining the Cobas Amplicor System (Roche Diagnostics, Sydney, Australia) and an in-house LightCycler assay targeting the cppB gene (cppB-LC). In addition, the specificity of the NGpapLC assay was investigated by testing a broad panel of bacteria including isolates of several Neisseria spp. The NGpapLC assay proved to have comparable clinical sensitivity to the cppB-LC assay. In addition, testing of the bacterial panel showed the NGpapLC assay to be highly specific for N. gonorrhoeae DNA. The results of this study show the NGpapLC assay is a suitable alternative to the cppB-LC assay for confirmation of N. gonorrhoeae-positive results obtained with Cobas Amplicor.
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ABSTRACT: We evaluated LGV prevalence and predictors in a high risk population attending a STI Outpatients Clinic in the North of Italy. A total of 108 patients (99 MSM and 9 women), with a history of unsafe anal sexual intercourses, were enrolled. Anorectal swabs and urine samples were tested for Chlamydia trachomatis (CT) DNA detection by Versant CT/GC DNA 1.0 Assay (Siemens Healthcare Diagnostics Terrytown, USA). RFLP analysis was used for CT molecular typing. L2 CT genotype was identified in 13/108 (12%) rectal swabs. All LGV cases were from MSM, declaring high-risk sexual behaviour and complaining anorectal symptoms. Patients first attending the STI Outpatient Clinic received a significant earlier LGV diagnosis than those first seeking care from general practitioners or gastroenterologists (P = 0.0046).LGV prevalence and characteristics found in our population are in agreement with international reports. Statistical analysis showed that LGV positive patients were older (P = 0.0008) and presented more STIs (P = 0.0023) than LGV negative ones, in particular due to syphilis (P < 0.001), HIV (P < 0.001) and HBV (P = 0.001).Multivariate logistic regression analysis revealed that HIV and syphilis infections are strong risk factors for LGV presence (respectively, P = 0.001 and P = 0.010). Even if our results do not provide sufficient evidence to recommend routine screening of anorectal swabs in high-risk population, they strongly suggest to perform CT NAAT tests and genotyping on rectal specimens in presence of ulcerative proctitis in HIV and/or syphilis-positive MSM. In this context, CT DNA detection by Versant CT/GC DNA 1.0 Assay, followed by RFLP analysis for molecular typing demonstrated to be an excellent diagnostic algorithm for LGV identification.BMC Research Notes 04/2014; 7(1):225.
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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.Sexual Health 09/2012; 9(4):384-8. · 1.58 Impact Factor
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ABSTRACT: Nucleic acid detection tests (NADT) have considerable benefits for the detection of Neisseria gonorrhoeae (GC), including high sensitivity across a range of specimen types and use under widely differing settings and conditions. However, sexual health practitioners and others who use data generated by NADT for GC should be aware of some important limitations of these tests. False-positive results caused by cross reaction with commensal Neisseria species have been observed in many assays, and have lead to unacceptably low positive-predictive values in some patient populations. Further, false-negative results can be caused by GC sequence variation, with some gonococci lacking certain NADT target sequences. This review examines the issues associated with gonococcal NADT and considers best practice for use of these assays based on current knowledge. We emphasise the need for supplementary testing and extensive assay validation, and suggest appropriate strategies for these requirements irrespective of the setting in which they are used. Further, we highlight the need to maintain culture-based testing for certain specimen sites as well as for antimicrobial resistance surveillance.Sexual Health 04/2008; 5(1):17-23. · 1.58 Impact Factor