SAN DIEGO – The concomitant use of probiotics and antibiotics associated with a high risk of acquiring Clostridium difficile infections increased the risk of developing C. difficile by nearly threefold, a single-center retrospective study showed.
"We were very surprised by this finding," Justine E. Dickson, Pharm. D., said in an interview at IDWeek, the combined annual meetings of the Infectious Diseases Society of America, the Society for Healthcare Epidemiology of America, the HIV Medicine Association, and the Pediatric Infectious Diseases Society.
Justine E. Dickson, Pharm. D.
Dr. Dickson and her colleagues at Yale–New Haven Hospital evaluated 389 adult inpatients who received high-risk antibiotics for 5 days or more between July 1 and Dec. 31, 2010. High-risk antibiotics investigated included ceftriaxone, ciprofloxacin, clindamycin, imipenem-cilastatin, levofloxacin, and meropenem. Formulary probiotics investigated were Lactobacillus GG and Saccharomyces boulardii.
Of the 389 patients, 246 (63%) received antibiotics alone while 143 (37%) received antibiotics and a probiotic. A total of 20 patients (5%) developed a C. difficile infection (CDI) within 90 days of antibiotic use. The average duration of high-risk antibiotic use was 7.3 days among those who received probiotics and 7.7 days among those in the antibiotics-only group.
Dr. Dickson, who is now a PGY-2 ambulatory care pharmacy resident at the University Hospital in Cincinnati, reported that the incidence of CDI was 8.4% among patients who received probiotics compared with 3.3% in the antibiotics-only group. Levofloxacin was the most common high-risk antibiotic used by patients who developed a CDI, representing 65% of cases.
The risk of developing CDI among patients who received probiotics was 2.7 times higher than in patients in the antibiotics-only group, a difference that reached statistical significance. After controlling for the use of levofloxacin (the researchers initially speculated that this antibiotic might be a key culprit), they found that the relative risk remained similar, at 2.6 times higher among patients who received probiotics.
When the researchers factored in the concomitant use of proton pump inhibitors, the incidence of CDI did not differ among patients in the antibiotics-only group, but the concomitant use of probiotics further increased the risk of CDI, "which may suggest a potential interaction between these two drug classes," the researchers wrote in their abstract, which was presented during a poster session.
The investigators stated that they had no relevant financial conflicts to disclose.