Probiotics to Prevent Antibiotic-Associated Diarrhea?

Summary and Comment |
July 11, 2007

Probiotics to Prevent Antibiotic-Associated Diarrhea?

  1. Stephen G. Baum, MD

A probiotic yogurt drink significantly reduced the incidence of antibiotic-associated diarrhea and C. difficile–associated diarrhea in hospitalized patients.

  1. Stephen G. Baum, MD

Antibiotic-associated diarrhea, particularly diarrhea caused by Clostridium difficile, is a major and growing problem worldwide. For patients taking antibiotics, the use of probiotics (in this case, dietary supplements containing live bacteria) is intended to populate the gut with “nonpathogenic” organisms that will compete with pathogenic ones such as C. difficile, thereby preventing diarrhea. Previous studies attempting to show benefit from probiotic prophylaxis or co-treatment have yielded conflicting results.

Now, in a partially manufacturer-funded, double-blind study conducted in London, researchers have studied the effects of probiotic use in 135 hospitalized patients >50 years old who were on antibiotics. Participants were randomized to receive either a yogurt drink containing Lactobacillus casei, Lactobacillus bulgaricus, and Streptococcus thermophilus or a bacteria-free commercial milkshake preparation. Treatment began within 48 hours of antibiotic initiation and continued for 1 week after antibiotics were stopped. If diarrhea occurred, stools were tested for C. difficile. Compliance (assessed by percentage of the prescribed drink that was consumed) was 75% in the probiotic group and 79% in the control group.

In intention-to-treat analysis, the yogurt drink significantly reduced incidence of both antibiotic-associated diarrhea (absolute risk reduction, 22%; 95% confidence interval, 7% to 37%) and C. difficile–associated diarrhea (absolute risk reduction, 17%; 95% CI, 7% to 27%). The numbers needed to treat to prevent one case were five and six, respectively. Low serum sodium and albumin concentrations were independent risk factors for diarrhea. After adjustment for these variables, probiotic use reduced diarrhea risk by 75%.


The morbidity and mortality of antibiotic-associated diarrhea, and the magnitude of the problem worldwide, justify any attempt at prevention. Despite this study’s limitations (inclusion of minimally ill patients who were presumably receiving short courses of antibiotics [e.g., as prophylaxis before or after orthopedic surgery], exclusion for use of “high-risk antibiotics,” and high loss to follow-up), the findings are sufficiently promising in both clinical and economic terms to warrant a larger, more- inclusive study of probiotics for prevention of antibiotic-associated diarrhea.


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