Large-scale evaluation of a rapid diagnostic test for diarrhea caused by enterotoxigenic Escherichia coli targeting the heat-labile toxin

Evaluation of non-invasive diagnostic tools for diarrhea: a systematic review of point-of-care tests and biomarkers

Background

Diarrhea is a prevalent condition affecting millions worldwide. However, current standard diagnostic methods have many drawbacks. This review examines various non-invasive point-of-care (POC) tests and biomarkers aiding rapid diagnosis of diarrhea from different causes.

Methods

PubMed, PubMed Central, ScienceDirect, Cochrane Library, and Google Scholar were searched from 2013 to present for relevant literature. Two reviewers independently assessed included studies' quality using the Critical Appraisal Skills Programme (CASP) checklist.

Results

The search yielded 1453 studies, of which 39 were included after screening and applying eligibility criteria. Polymerase chain reaction (PCR) was the POC test in 25 studies, providing consistent sensitivity and specificity. For biomarkers, C-reactive protein (CRP), fecal calprotectin, and procalcitonin offered high sensitivity and specificity for conditions like acute pediatric diarrhea, microscopic colitis, and inflammatory diarrhea, respectively.

Conclusion

PCR proved the ideal POC test for rapid diarrhea diagnosis, while the procalcitonin biomarker helps differentiate inflammatory from non-inflammatory diarrhea. Other reviewed tools also demonstrated promising diagnostic performance, though improvements in sensitivity, specificity, and usability are still needed.

Selection of G-rich ssDNA aptamers for the detection of enterotoxins of the cholera toxin family

Cholera and milder diarrheal disease are caused by Vibrio cholerae and enterotoxigenic Escherichia coli and are still a prominent public health concern. Evaluation of suspicious isolates is essential for the rapid containment of acute diarrhea outbreaks or prevention of epidemic cholera. Existing detection techniques require expensive equipment, trained personnel and are time-consuming. Antibody-based methods are also available, but cost and stability issues can limit their applications for point-of-care testing. This study focused on the selection of single stranded DNA aptamers as simpler, more stable and more cost-effective alternatives to antibodies for the co-detection of AB₅ toxins secreted by enterobacteria causing acute diarrheal infections. Cholera toxin and Escherichia coli heat-labile enterotoxin, the key toxigenicity biomarkers of these bacteria, were immobilized on magnetic beads and were used in a SELEX-based selection strategy. This led to the enrichment of sequences with a high % GC content and a dominant G-rich motif as revealed by Next Generation Sequencing. Enriched sequences were confirmed to fold into G-quadruplex structures and the binding of one of the most abundant candidates to the two enterotoxins was confirmed. Ongoing work is focused on the development of monitoring tools for potential environmental surveillance of epidemic choleraand milder diarrheal disease.