Stool Testing for Potential Kidney Donors with History of Viral Gastroenteritis or Foodborne Illness
In a potential kidney donor with a history of viral gastroenteritis or foodborne illness, stool testing must screen for common enteric bacterial pathogens (Salmonella, Shigella, Campylobacter), Shiga toxin-producing E. coli, C. difficile, enteric viruses (norovirus, rotavirus), and parasites (Giardia, Cryptosporidium) to ensure no active or recent infection that could be transmitted or indicate ongoing gastrointestinal pathology. 1
Core Bacterial Pathogen Testing
The most recent guidelines from the British Society of Gastroenterology and Healthcare Infection Society (2024) provide the definitive framework for donor stool screening, which directly applies to kidney donor evaluation:
- Test for Campylobacter, Salmonella, and Shigella, preferably by PCR 1
- Screen for Shiga toxin-producing E. coli by PCR to detect both O157 and non-O157 serotypes 1
- Include testing for other enteropathogenic E. coli beyond STEC, as these can cause significant disease in immunocompromised recipients 1
- Test for C. difficile toxin B (tcdB) by PCR - note that glutamate dehydrogenase (GDH) screening alone is insufficient 1
Viral Pathogen Screening
Given the donor's history of viral gastroenteritis, comprehensive viral testing is essential:
- Screen for norovirus and rotavirus by PCR 1
- Consider broader viral screening via multiplex panel including sapovirus and potentially poliovirus, depending on local epidemiology 1
- Test for SARS-CoV-2 based on current prevalence, though protocols may evolve with changing epidemiology 1
Norovirus is particularly important given its high prevalence in gastroenteritis outbreaks and potential for transmission through contaminated materials 2.
Parasitic Pathogen Testing
Complete stool ova, cysts, and parasite analysis is mandatory:
- Test for Cryptosporidium and Giardia by antigen detection or PCR 1
- Perform acid-fast staining for Cyclospora, Isospora (Cystoisospora), and Microsporidia 1
- These organisms are particularly relevant in immunocompromised transplant recipients who may develop severe disease 3
Multidrug-Resistant Organism Screening
Screen for antibiotic-resistant bacteria including:
- Carbapenemase-producing Enterobacterales 1
- Extended-spectrum beta-lactamase (ESBL)-producing organisms 1
- Vancomycin-resistant enterococci 1
This screening is critical as transplant recipients will be immunosuppressed and at higher risk for severe infections with resistant organisms 4.
Additional Considerations
Helicobacter pylori stool antigen testing may be considered but is not necessarily exclusionary if positive, particularly in Western populations where gastric cancer risk differs from endemic regions 1. Recent evidence suggests H. pylori is not readily transmitted through fecal material 1.
Critical Timing Issues
The 2019 international consensus and 2024 BSG/HIS guidelines emphasize specific timeframes:
- Exclude donors with acute gastroenteritis within the past 2 weeks to 2 months 1
- Recent enteric pathogen infection within 2 months is a contraindication 1
- This waiting period allows for clearance of pathogens and normalization of gut microbiota 1
Testing Methodology Considerations
Multiplex PCR panels offer significant advantages over traditional culture methods, detecting 3-4 times more pathogens in immunocompromised populations 4, 5. However, a critical caveat exists: molecular tests detect DNA/RNA, not necessarily viable organisms 1, 6. This means positive results require clinical correlation and may necessitate confirmatory culture in certain circumstances 6, 5.
Common Pitfalls to Avoid
- Do not rely on GDH screening alone for C. difficile - toxin gene detection is required 1
- Do not assume negative routine testing excludes all pathogens - standard methods miss 50-70% of infections detected by molecular methods 4, 5
- Do not test donors who have not fully recovered from their gastrointestinal illness or who remain within the 2-month exclusion window 1