Effects on intestinal microbiota of probiotic fermented milk used for prevention of antibiotic-associated diarrhoea

Probiotic administration could prevent antibiotic-associated diarrhoea due to the restoration of an intestinal microbiota imbalance caused by antibiotics. The effect of the probiotics Lactobacillus acidophilus LA-5, Lactobacillus casei subsp. casei LC-01 and Bifidobacterium animalis subsp. lactis BB-12 on the composition and metabolic activities of the intestinal microbiota in human subjects during antibiotic treatment has been analyzed. Subjects that were placed on antibiotic therapy (amoxiciline/clavulanic or levofloxacin) were randomly assigned to receive a multispecies probiotic fermented milk (n = 122) or a placebo fermented milk (n = 125). Stool samples were collected at different intervals during the intervention study and analysed for faecal microbiota enumeration, probiotic species detection, enzyme activities and short chain fatty acid (SCFA) concentrations. The most predominant microbiota groups were total anaerobes, bacteroides and total aerobes. Probiotic species in fecal samples were analyzed by real-time PCR and results indicated that prevalence of the probiotic species within the probiotic group was below 50 % during the intervention study. Enzyme activities and SCFA concentrations showed a large inter-individual variability over the time in the placebo and probiotic groups, except to beta-galactosidase activity, which was the most abundant in both groups over the time. In conclusion, the combination of L. acidophilus LA-5, L. casei subsp. casei LC-01 and B. animalis subsp. lactis Bb-12 taken in daily doses of 10(9)-10(10) colony-forming units (CFU) does not significantly influence (P > 0.05) either the fecal microbiota or its metabolic activity in elderly hospitalized patients taking amoxicillin/clavulanate or levofloxacin. In addition, this combination of probiotic strains did not reduce the rate of occurrence of diarrohea in these patients.