From the Guidelines
For colitis, I recommend ordering a stool culture that includes testing for Clostridium difficile toxin, as well as bacterial pathogens such as Campylobacter jejuni, Salmonella and Shigella species, and Escherichia coli O157:H7, especially if the patient has no history of antibiotic use within the previous 30 days or a negative C. difficile evaluation result. This approach is supported by the Infectious Diseases Society of America guidelines, which suggest that in patients with symptoms of colitis, initial evaluation for C. difficile should be performed, especially if the patient has received antibiotics within the previous 30 days 1. If the patient has no history of antibiotic use or a negative C. difficile evaluation result, a stool sample for culture for isolation of the most frequent invasive enteropathogens should be submitted 1. It's also important to consider the patient's clinical presentation, travel history, and exposure to healthcare settings when deciding which tests to order. Additionally, endoscopy with biopsies may be useful in determining the underlying cause of colitis, especially in cases where the diagnosis is unclear or the patient has a severe presentation 1.
Some key points to consider when ordering stool cultures for colitis include:
- Testing for C. difficile toxin is crucial, especially in patients with recent antibiotic use or healthcare exposure
- Bacterial pathogens such as Campylobacter jejuni, Salmonella and Shigella species, and Escherichia coli O157:H7 should be included in the stool culture
- Endoscopy with biopsies may be useful in determining the underlying cause of colitis, especially in severe or unclear cases
- The patient's clinical presentation, travel history, and exposure to healthcare settings should be considered when deciding which tests to order.
It's essential to note that the treatment approach varies significantly depending on the underlying cause of colitis, and early identification of the cause is crucial for appropriate management. For instance, bacterial infections may require specific antibiotics, while C. difficile colitis typically requires oral vancomycin or fidaxomicin, and parasitic infections need targeted antiparasitic medications. If all infectious workup is negative, the colitis may be inflammatory bowel disease requiring immunosuppressive therapy.
From the Research
Stool Culture for Colitis
To diagnose infectious colitis, a standard stool culture should be performed, as recommended by 2. This culture can help identify invasive or inflammatory bacterial enteropathogens such as:
- Shigella
- Salmonella
- Campylobacter
- Shiga toxin-producing Escherichia coli (STEC)
- Clostridium difficile
Specialized Studies
Epidemiologic findings, such as prior international travel or living in parasite-endemic regions, may suggest the need for specialized studies of etiology, as noted by 2 and 3. For example, if STEC is suspected, a competent laboratory should look for E. coli O157:H7 and Shiga toxin directly in stool, as recommended by 2.
Pathogen-Specific Diagnosis
Once a laboratory diagnosis is made, pathogen-specific antimicrobial therapy should be initiated for all forms of infectious colitis, except for STEC, as stated by 2. The diagnosis of infectious colitis can also be supported by the presence of inflammatory markers in the stool, such as leukocytes, lactoferrin, or calprotectin, as mentioned by 2.
Empiric Treatment
For empiric treatment of febrile dysenteric diarrhea, invasive bacterial enteropathogens (Shigella, Salmonella, and Campylobacter) should be suspected, and adults may be treated empirically with 1000mg azithromycin in a single dose, as suggested by 2. However, it is essential to note that the treatment approach may vary depending on the specific pathogen and the patient's condition, as discussed by 3, 4, 5, and 6.