A clinical update for general practitioners and specialists from the Medical Microbiology department
ADC, your national laboratory, has introduced PCR-based screening of stool samples for the bacteria most commonly behind gastro-enteritis on Curaçao: Salmonella, Shigella, Yersinia and Campylobacter species (SSYC), alongside Clostridium difficile.
The international literature is clear that PCR is more sensitive than traditional bacterial culture for detecting these pathogens. Our own data confirms what the literature shows: on Curaçao, Salmonella and Campylobacter are the bacteria responsible for most cases of bacterial diarrhoea presenting in primary care.
Research from one of our medical microbiologists, alongside published studies, shows two further points worth knowing. A negative PCR result does not benefit from repeat testing. And PCR delivers an answer in 1 to 3 days, where culture takes longer. The trade-off is that PCR looks for a specific, defined panel of pathogens.
Four years of culture data from our laboratory supports this approach for Curaçao. Other diarrhoea-associated bacteria, including Plesiomonas, enterohaemorrhagic E. coli and V. cholera, have not turned up in stool samples from the island during this period. Clostridium difficile, the cause of antibiotic-associated diarrhoea, is also rare locally.
How the workflow runs
Samples received before 11:00 are reported the same day if the PCR is negative. Samples received after 11:00 are reported the following day.
If the PCR is positive, we proceed to culture to determine antibiotic susceptibility for the pathogen identified.
When to request more than the standard panel
The clinical picture sometimes points beyond the SSYC panel. On the request form, alongside the SSYC request, you can specifically request analysis for E. coli O157 (enterohaemorrhagic E. coli), V. cholera or Plesiomonas where the clinical context suggests it. These requests are processed separately from the standard PCR screening. Travellers and patients with recent surface water contact are common cases where this matters.
For protozoan parasites that cause diarrhoea, Giardia lamblia, Cryptosporidium and Entamoeba histolytica, we also use PCR. The same applies to viral causes: norovirus type I and II, sapovirus, rotavirus, adenovirus and astrovirus. As with the bacterial PCR, repeat testing for parasites and viruses is not clinically useful.
A note on worms. Worms do not cause diarrhoea, and detection requires a different approach. Look for worms or worm eggs in fresh stool. For suspected enterobiasis (pinworm), use the adhesive tape method, as outlined in the vademecum. Fresh stool is the only sample type suitable for molecular diagnostics, culture and parasitology.
A note on coverage
The PCR panel does not cover every possible cause. Plesiomonas, Vibrio species and enterohaemorrhagic E. coli O157 sit outside the screen. Keep these in mind for travellers and patients with surface water exposure, and request them specifically when the clinic supports it.
This change is designed to give you and your patients a faster, more reliable answer. If you have questions about the new workflow, please get in touch with the Medical Microbiology