Antibiotic-associated hemorrhagic colitis is a distinct form of antibiotic-associated colitis in which Clostridium difficile is absent.
Although the cause is not known, previous reports have suggested a role of Klebsiella oxytoca.
Dr Christoph Högenauer and colleagues studied 22 consecutive patients who had suspected antibiotic-associated colitis but negative for C difficile.
Patients underwent diagnostic colonoscopy.
Among those who received a diagnosis of antibiotic-associated hemorrhagic colitis, stool samples were cultured for K oxytoca.
The research team isolated K oxytoca strains and tested them for cytotoxin production using a tissue-culture assay.
|K oxytoca was found in about 2% of the healthy subjects|
|New England Journal of Medicine|
In addition, the researchers cultured stool samples obtained from 385 healthy subjects for K oxytoca.
An in vivo animal model for antibiotic-associated hemorrhagic colitis was established with the use of Sprague-Dawley rats.
Of the 22 patients, the team identified 6 with findings on colonoscopy that were consistent with the diagnosis of antibiotic-associated hemorrhagic colitis.
The researchers noted that 5 of these 6 patients had positive cultures for K oxytoca.
The research team found no other common enteric pathogens in the 5 patients.
Before the onset of colitis, all 5 were receiving penicillins, and 2 were also taking nonsteroidal antiinflammatory drugs (NSAIDs).
The researchers observed that all isolated K oxytoca strains produced cytotoxin.
The team found K oxytoca in about 2% of the healthy subjects.
In the animal model, K oxytoca was found only in the colon of rats receiving amoxicillin-clavulanate in addition to K oxytoca inocculation.
In these rats, infection with K oxytoca induced a right-sided hemorrhagic colitis.
The researchers did not observe this in uninfected animals that received amoxicillin-clavulanate, indomethacin, or both.
Dr Högenauer's team concludes, “Our fulfillment of Koch's postulates for cytotoxin-producing K oxytoca suggests that it is the causative organism in at least some cases of antibiotic-associated hemorrhagic colitis.”
“Infection with K oxytoca should be considered in patients with antibiotic-associated colitis who are negative for C difficile.”