From the Guidelines
Fecal samples are required for the diagnosis of foodborne illness in certain circumstances, such as severe symptoms, prolonged duration, or potential outbreaks, as recommended by the 2017 Infectious Diseases Society of America clinical practice guidelines 1. When diagnosing foodborne illness, the decision to collect a fecal sample depends on various factors, including the severity of symptoms, duration of illness, and potential for outbreak.
- Mild symptoms that resolve within a day or two typically do not require testing.
- Severe symptoms, such as high fever, bloody diarrhea, or dehydration, warrant stool testing to identify the causative pathogen.
- Symptoms lasting more than three days or potential outbreaks also necessitate stool sampling. The 2017 guidelines emphasize the importance of stool testing in vulnerable populations, including young children, elderly individuals, pregnant women, and those with compromised immune systems 1. Stool testing helps guide appropriate treatment, determines the need for antibiotics, and informs public health officials to track outbreaks and prevent further spread of foodborne illness 1. In general, a diarrheal stool sample is the optimal specimen for laboratory diagnosis of infectious diarrhea, although a rectal swab may be used if a timely stool sample cannot be collected 1. The results of stool culture or examination for ova and parasites may have significant public health importance, even if they do not directly impact clinical management decisions 1.
From the Research
Fecal Samples in Diagnosing Foodborne Illness
- Fecal samples can be useful in diagnosing foodborne illness, as they can help identify the causative organism 2.
- A study found that stool culture positivity was predictive of certain clinical features, such as a higher temperature and a history of fever 2.
- However, another study noted that assays for diagnosing infectious gastroenteritis based on the host response to infection lack sensitivity and specificity as stand-alone tests, and that fecal biomarkers may be more useful as adjunct diagnostics 3.
Requirements for Fecal Samples
- Not all cases of suspected foodborne illness require fecal samples for diagnosis 4.
- In some cases, such as severe sepsis or in subjects at risk, empirical treatments without bacterial identification may be indicated, but this is not typically the case for foodborne illness 4.
- A study found that GPs in England often send stool specimens for microbiological investigation based on individual symptoms, rather than public health implications, and may not always follow national guidance 5.
Alternative Diagnostic Methods
- Systemic biomarkers, such as C-reactive protein and serum cytokines, may be used to diagnose infectious gastroenteritis, but they lack sensitivity and specificity as stand-alone tests 3.
- Stool-based multiplex Polymerase Chain Reaction (PCR) can detect bacteria, viruses, or parasites that may be responsible for gastroenteritis, but the presence of potential pathogens does not always justify anti-infectious treatment 4.
- Empirical treatment with antibiotics may be effective in reducing the duration of diarrhea and other symptoms, but it is not always necessary and may contribute to antibiotic resistance 6.