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Exposure to certain antibiotics linked to resistant C. difficile strains
Exposure to fluoroquinolone and macrolide were found to be associated with infection by the epidemic BI/NAP1/027 strain of Clostridium difficile, which is highly resistant to these antibiotics, according to recent study data.
“Antibiotic exposure is arguably the most important risk factor for C. difficile infection (CDI),” Stuart Johnson, MD, from Loyola University Health System, Loyola University Chicago Stritch School of Medicine and the Hines VA Medical Hospital, told Healio Gastroenterology. “The main role of antibiotics in the pathogenesis of CDI is likely alteration of the beneficial flora in the gut, making patients susceptible to a C. diff infection. However, another role of antibiotics highlighted in our study is that overuse of specific antibiotics may facilitate infection due to C. diff strains that are highly resistant to those antibiotics.”
Stuart Johnson*
Dale N. Gerding
To assess the risks tied to specific antibiotics for infection with the epidemic BI strain of C. difficile, Johnson, along with Dale N. Gerding, MD, and colleagues, performed a retrospective case-control study of 143 patients with a first episode of CDI who were identified between 2005 and 2007 in a U.S. hospital during a period when CDI rates and severity were increased nationally.
They used stool culture, strain typing and susceptibility testing of C. difficile isolates to define cases and controls.
Overall, 72% of included patients were infected with the highly fluoroquinolone- and macrolide-resistant BI/NAP1/027 C. difficile strain. Most of the remaining patients were infected with REA group J strains. The majority of patients received multiple antibiotics (median, 3 classes) within 6 weeks of diagnosis.
“Fluoroquinolone and macrolide exposure was more frequent in patients with BI strains, and the C. difficile bacteria recovered from the stool specimens of these BI-infected patients also showed high-level resistance to these antibiotics,” Johnson said.
Multivariate analysis revealed fluoroquinolone exposure was more frequent among BI-infected cases compared with non–BI-infected controls (OR = 3.2; 95% CI, 1.3-7.5) and that macrolide exposure was more frequent among BI-infected cases as well (OR = 5.2; 95% CI, 1.1-24), whereas clindamycin exposure was less frequent (OR = 0.1; 95% CI, 0.03-0.4).
Furthermore, high-level resistance to moxifloxacin was more frequent among BI-strains compared with controls (48% vs. 0%; P = .0001), as was high-level resistance to azithromycin (98% vs. 55%; P = .0001), whereas high-level resistance to clindamycin was more frequent among non-BI strains (55% vs. 7%; P = .0001).
“This study suggests that targeted antimicrobial stewardship interventions may be helpful when high rates of CDI due to specific epidemic strains are present,” Johnson said. – by Adam Leitenberger
Disclosure: Johnson and Gerding report they received funding from VA Research.
Photo Credit: Loyola University Health System