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A High-throughput Platform for the Screening of Salmonella spp./Shigella spp.
Published on: November 7, 2018
Case-control comparison of bacterial and protozoan microorganisms associated with gastroenteritis: application of
L E S Bruijnesteijn van Coppenraet1, M Dullaert-de Boer2, G J H M Ruijs1
1Laboratory for Medical Microbiology and Infectious Diseases, Isala, Zwolle, The Netherlands.
Abstract:
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.
Insights
Molecular detection for gastroenteritis (GE) pathogens is common, but clinical value is unclear due to unknown prevalence in healthy individuals. This study found varied pathogen presence in cases versus controls, highlighting the need for careful interpretation of molecular diagnostics.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Molecular Diagnostics
Background:
- Molecular detection methods have increased identification of infectious organisms, including those causing gastroenteritis (GE).
- The clinical significance of these findings is often uncertain due to limited data on pathogen prevalence in healthy, asymptomatic populations.
Purpose of the Study:
- To investigate the prevalence of common GE pathogens in patients with GE compared to healthy controls.
- To assess the clinical utility of molecular diagnostics for GE by evaluating pathogen detection rates and loads.
Main Methods:
- A case-control study involving 2710 fecal samples from GE patients and matched controls in the Netherlands.
- Multiplex real-time PCR was used to detect 11 bacterial and 4 protozoal GE pathogens.
Main Results:
- 54% of GE cases and 49% of controls tested positive for one or more pathogens.
- Higher detection rates in cases were observed for Campylobacter spp., Salmonella spp., Clostridium difficile, and several E. coli pathotypes, Cryptosporidium, and Giardia.
- Dientamoeba fragilis and Shiga-like toxigenic E. coli were less frequent in cases, while typical EPEC and enterohemorrhagic E. coli showed no difference.
Conclusions:
- Molecular diagnostics for GE are sensitive and rapid but require careful interpretation alongside clinical data.
- Pathogen load in cases versus controls can help infer causality, though this association varies by pathogen and age group.
- Understanding asymptomatic pathogen carriage is crucial for accurately assessing the clinical relevance of molecular findings in infectious gastroenteritis.
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