What does detection of Clostridioides difficile (C. difficile) toxin A/B in stool signify?

From the Guidelines

Detection of Clostridioides difficile toxin A/B in stool signifies a potentially serious bacterial infection of the colon, indicating the presence of toxins that cause inflammation and damage to the intestinal lining. This finding is based on the most recent and highest quality study available, which emphasizes the importance of clinical context and laboratory tests in diagnosing C. difficile infection (CDI) 1. The study highlights that the diagnosis of CDI should be suspected in patients with acute diarrhea (≥ 3 loose stools in 24 h) with no obvious alternative explanation, particularly in the setting of relevant risk factors such as recent antibiotic use, hospitalization, and advanced age.

Key Points to Consider

• The detection of toxin A/B in stool is a key indicator of CDI, but it should be interpreted in the context of clinical symptoms and risk factors 1.
• The diagnosis of CDI requires both clinical symptoms and a positive laboratory test, and stool testing should only be performed on diarrheal stools from at-risk patients with clinically significant diarrhea 1.
• Nucleic acid amplification tests (NAATs) for C. difficile toxin genes appear to be sensitive and specific, and may be used as a standard diagnostic test for CDI, but they may not distinguish between colonization and active disease 1.
• Treatment typically involves a 10-14 day course of antibiotics such as oral vancomycin, fidaxomicin, or metronidazole for mild cases, and patients should stay well-hydrated, avoid anti-diarrheal medications, and practice strict hand hygiene to prevent spreading the infection to others.

Importance of Clinical Context

The clinical context is crucial in selecting patients for testing, and signs such as fever, abdominal pain, leukocytosis, and laboratory tests (e.g., creatinine and serum lactate) are useful for defining the severity of infection 1. The study also highlights the importance of only testing patients with symptoms, as asymptomatic patients may be colonized with toxigenic C. difficile, leading to false positive results and unnecessary antibiotic therapy.

Limitations of Diagnostic Tests

The study notes that there is no single stool test that can be relied upon as the reference standard for the diagnosis of CDI, and several methods are suggested for the diagnosis of CDI, including toxinogenic culture, cell cytotoxicity neutralization assay, enzyme immunoassays, and NAATs 1. The limitations of these tests, including their sensitivity and specificity, should be considered when interpreting results.

From the Research

Detection of C. difficile Toxin A/B

• The detection of Clostridioides difficile (C. difficile) toxin A/B in stool signifies a serious diarrheal illness associated with substantial morbidity and mortality 2.
• C. difficile infection is generally associated with changes in the normal intestinal microbiota caused by administration of antibiotics 3.
• The presence of toxin A/B in stool is a key indicator of C. difficile infection, and patients with positive stool toxin tests are eligible for treatment 2.

Treatment and Significance

• The detection of C. difficile toxin A/B in stool is crucial for guiding treatment, as patients with positive results are typically treated with antibiotics such as vancomycin or fidaxomicin 2, 3.
• The treatment options for C. difficile infection have undergone significant changes, with fidaxomicin and bezlotoxumab emerging as new therapies, and microbial replacement therapies such as fecal microbiota transplantation (FMT) showing promise 3, 4, 5.
• The detection of toxin A/B in stool can also indicate a high risk of recurrence, and treatment strategies such as FMT may be considered for patients with recurrent C. difficile infections 6.

Clinical Implications

• The detection of C. difficile toxin A/B in stool has significant clinical implications, as it can guide treatment decisions and predict the risk of recurrence 2, 3.
• Patients with positive stool toxin tests require prompt treatment to prevent complications and reduce the risk of transmission to others 2, 3.
• The detection of toxin A/B in stool can also inform the use of alternative treatment strategies, such as FMT, which may be effective in restoring intestinal eubiosis and preventing recurrence 6.