In-vitro growth characteristics of commercial probiotic strains and their potential for inhibition of Clostridium difficile and Clostridium perfringens

Probiotics have gained importance in human and veterinary medicine to prevent enteric disease. Little information is available on commercial probiotic strains regarding their growth characteristics and inhibition of equine enteric pathogens such as Clostridium difficile and Clostridium perfringens. To study growth characteristics of 17 commercial probiotic strains (Lactobacilli n=16, Bifidobacteria n=1) MRS broth was adjusted to pH 2 or 4 or supplemented with 0.15% or 0.3% bile.

Growth was measured at 0 and 24h and compared spectrophotometrically to control growth in standard MRS broth. Growth under aerobic conditions was assessed. To evaluate inhibition of C. difficile and C. perfringens sterile supernatant of the probiotic culture was added to BHI inoculated with a standard C. difficile or C. perfringens suspension.

Growth was measured spectrophotometrically at 0 and 24h and compared to the control (C. difficile or C. perfringens suspension in BHI). At pH 4 12% of strains showed >50% growth and 24% were unable to grow, however did survive. At pH 2 none of the tested strains grew or survived. Eighty eight percent showed >75% growth in 0.15% bile, 60% showed >75% growth in 0.3% bile.

Ninety-four percent grew under aerobic conditions. Ninety-four percent of strains were inhibitory (0-20% growth compared to control) against C. difficile and 76% were inhibitory against C. perfringens. Sixty percent of the tested strains showed favourable in-vitro characteristics for use as potential equine probiotics and could be further studied in placebo controlled clinical trials for prevention or treatment of C. difficile and C. perfringens associated disease.