Antibiotic use confers up to tenfold risk of C. diff infection

A patient's risk of developing Clostridium difficile infection (CDI) is 7 to 10 times higher during antibiotic therapy and in the month after stopping, and an elevated risk still exists three months after stopping antibiotics, a study found.

Dutch researchers performed a case-control study in nine hospitals between March 1, 2006 and May 1, 2009. They compared 337 hospitalized patients with diarrhea and a positive toxin test to 337 patients without diarrhea. A control group of 227 patients with diarrhea from a cause other than C. diff was also included. Results were reported in the March Journal of Antimicrobial Chemotherapy.

In the month prior to the reference date, 77% of CDI patients used an antibiotic compared with 48.9% of non-diarrheal patients (P<0.01). Of these, 35% of CDI patients and 25% of non-diarrheal patients were using an antibiotic at the time of diagnosis (P=0.01). On multivariate analysis, there was a more than sixfold increased risk for CDI during antibiotic use and in the first month after stopping antibiotics (odds ratio [OR], 6.67 to 10.37). The risk declined in the period between one and three months after the antibiotic was stopped (OR, 2.7 at three months). The control group comparison yielded similar results. All antibiotic classes were associated with CDI except first-generation cephalosporins and macrolides. The antibiotics with the strongest associated risks were second- and third-generation cephalosporins (OR, 3.3 and 5.3, respectively) and carbapenems (OR, 4.7). Compared with non-diarrheal patients, those with CDI used more antibiotic classes (P<0.01) and more defined daily doses.

One study limitation was the use of various enzyme immunoassays to diagnose CDI. Given their reported sensitivities of between 60% and 85%, some patients could have been missed as having CDI, which in turn might have led to overestimation of the duration of increased risk of non-CDI diarrhea after antibiotic use. Even so, clinicians should be made aware that antibiotic use can greatly increase the risk for CDI, even if the use preceded the symptoms by a month, the researchers wrote.