Clostridioides difficile infection: Clinical sciences

Clostridioides difficile infection, or CDI, is an infection caused by the organism Clostridioides difficile, or C. difficile for short. Infection typically occurs through the fecal-oral route, by ingestion of spores found on contaminated surfaces, in soil, in water, or even on unwashed hands. Once the spores reach the intestines, the GI flora, or microbiota, protects the gut and doesn’t allow C. difficile to proliferate. But, if the diversity of GI flora is disrupted, often by recent antibiotic use, as well as proton pump inhibitors, or hospitalization, C. difficile can overgrow and infect the colon.

As a result, it starts producing toxins A and B, which can damage the gastrointestinal mucosa and eventually cause an inflammatory condition called pseudomembranous colitis. The presentation can range from non-severe disease to severe or even fulminant infection.

Now, if you suspect CDI, the first thing you should do is an ABCDE assessment, to determine if your patient is unstable or stable.

If the patient is unstable, stabilize the airway, breathing, and circulation, which typically requires obtaining IV access, resuscitating with IV fluids, and intubating the patient if you need to secure the airway. Once you stabilize the patient, obtain a focused history and physical examination, and order labs, including CBC, CMP, and lactic acid.

History typically reveals watery diarrhea, usually more than 3 loose stools in 24 hours, which might be associated with mucus or blood, while some may present with ileus. Additionally, individuals may report lower abdominal pain, fever, lethargy, and confusion, as well as recent or current antibiotic use. Physical examination might reveal abdominal distention and tenderness, decreased bowel sounds, and hypotension. Some individuals can present with altered mental status or even shock. Finally, lab results may show an elevated WBC count, serum creatinine, and lactic acid.

Now here’s a high-yield fact! If you suspect CDI in any patient, initiate contact precautions to avoid spreading the infection, and discontinue any inciting antibiotics if possible. You should wash your hands with soap and water before and after patient contact. Remember to avoid using alcohol-based sanitizers, as C. difficile spores are extremely resistant to alcohol.

Alright, now, let’s move on to CDI testing. First, you need to obtain a liquid stool sample, but if there’s minimal diarrhea you can also do a rectal swab. Next, send the sample for a glutamate dehydrogenase antigen test, and C. difficile toxins A and B. If both tests come back negative, rule out CDI and consider an alternative diagnosis. On the flip side, if both tests come back positive, it confirms CDI. However, some individuals can have one positive and one negative test, meaning that the results are inconclusive. In this case, order a nucleic acid amplification test, or NAAT for short, to confirm the result. A positive NAAT testing confirms CDI.

Now, severe clinical manifestations in combination with positive CDI testing can confirm the diagnosis of fulminant CDI, so start supportive care with IV fluids and electrolyte replacement. Additionally, put the patient on complete bowel rest and give total parenteral nutrition or TPN as required. If needed, place a nasogastric tube to access the stomach and relieve upper gastrointestinal distention. Finally, start antibiotics, such as oral or nasogastric vancomycin plus IV metronidazole.

Here’s a high-yield fact to remember! Oral metronidazole is mostly absorbed in the small bowel. But in individuals with non-severe disease, enough will make it to the colon to treat the infection. However, individuals with fulminant CDI might have ileus, which means not enough oral metronidazole will make it to the colon, so IV is the preferred route. On the other hand, oral vancomycin will make its way to the colon without being absorbed, so it’s typically a good choice for all severities of CDI.