Case-control comparison of bacterial and protozoan microorganisms associated with gastroenteritis: application of molecular detection.

The introduction of molecular detection of infectious organisms has led to increased numbers of positive findings, as observed for pathogens causing gastroenteritis (GE). However, because little is known about the prevalence of these pathogens in the healthy asymptomatic population, the clinical value of these additional findings is unclear. A case-control study was carried out in a population of patients served by general practitioners in the Netherlands. A total of 2710 fecal samples from case and matched control subjects were subjected to multiplex real-time PCR for the 11 most common bacterial and four protozoal causes of GE. Of 1515 case samples, 818 (54%) were positive for one or more target organisms. A total of 49% of the controls were positive. Higher positivity rates in cases compared to controls were observed for Campylobacter spp., Salmonella spp., Clostridium difficile, enteroinvasive Escherichia coli/Shigella spp., enterotoxigenic E. coli, enteroaggregative E. coli, atypical enteropathogenic E. coli (EPEC), Cryptosporidium parvum/hominis, and Giardia lamblia. However, Dientamoeba fragilis and Shiga-like toxigenic E. coli were detected significantly less frequent in cases than in controls, while no difference in prevalence was found for typical EPEC and enterohemorrhagic E. coli. The association between the presence of microorganisms and GE was the weakest in children aged 0 to 5 years. Higher relative loads in cases further support causality. This was seen for Campylobacter spp., Salmonella spp., enterotoxigenic E. coli, and C. parvum/hominis, and for certain age categories of those infected with C. difficile, enteroaggregative E. coli, and atypical EPEC. For D. fragilis and Shiga-like toxigenic E. coli/enterohemorrhagic E. coli, pathogen loads were lower in cases. Application of molecular diagnostics in GE is rapid, sensitive and specific, but results should be interpreted with care, using clinical and additional background information.

Detection of Chlamydia trachomatis and Neisseria gonorrhoeae in an STI population: performances of the Presto CT-NG assay, the Lightmix Kit 480 HT CT/NG and the COBAS Amplicor with urine specimens and urethral/cervicovaginal samples.

OBJECTIVES: This study assessed the performances of the Presto CT-NG assay, the Lightmix Kit 480 HT CT/NG and the COBAS Amplicor for Chlamydia trachomatis and Neisseria gonorrhoeae detection. DESIGN: A cross-sectional study design. SETTING: Izore, Centre for Diagnosing Infectious Diseases in Friesland, the Netherlands, tested samples sent from regional sexually transmitted infection (STI) outpatient clinics and regional hospitals from the province Friesland, the Netherlands. PARTICIPANTS: Samples were collected from 292 men and 835 women. These samples included 560 urine samples and 567 urethral/cervicovaginal samples. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcome measure is C trachomatis infection. No secondary outcome measures are available. RESULTS: The sensitivity, specificity, positive predicative value (PPV) and negative predictive value (NPV) for C trachomatis detection in urine samples using the Presto CT-NG assay were 100%, 99.8%, 98.1% and 100%, respectively; for the Lightmix Kit 480 HT CT/NG: 94.2%, 99.8%, 96.1% and 99.4%, respectively; for the COBAS Amplicor: 92.3%, 99.6%, 96% and 99.2%, respectively. The sensitivity, specificity, PPV and NPV for C trachomatis detection in urethral/cervicovaginal swabs using the Presto CT-NG assay and the COBAS Amplicor were 100%, 99.8%, 97.7% and 100%, respectively; for the Lightmix Kit 480 HT CT/NG: 100%, 99.6%, 97.7% and 100%, respectively. Calculations for N gonorrhoeae could not be made due to a low prevalence. CONCLUSIONS: All three assays had a high sensitivity, specificity, PPV and NPV for C trachomatis, with best performance for the Presto CT-NG assay.