Effects of Lactobacillus acidophilus and Lactobacillus reuteri cell-free supernatants on Cryptosporidium viability and infectivity in vitro Original Research Article

Protozoan parasites of the genus Cryptosporidium are a leading cause of diarrhea in domestic livestock and humans worldwide with bovine C. parvum and C. hominis being responsible for the vast majority of infections. To date there is no universal treatment for cryptosporidiosis, the disease caused by Cryptosporidium infection, but recent studies in mice suggest probiotic bacteria can reduce the duration and intensity of bovine C. parvum oocyst shedding. The mode of action utilized by these probiotics to exert their effects on bovine C. parvum infection was undetermined and their effect on C. hominis has never been evaluated. The purpose of this study was to determine if the probiotic bacteria, Lactobacillus acidophilus and Lactobacillus reuteri, produce compounds that are detrimental to bovine C. parvum and C. hominis. Cell-free supernatants of L. acidophilus (LA) and L. reuteri (LR) cultures reduced the infectivity of bovine C. parvum and C. hominis in a cell-culture immunofluorescence (CCIF) assay by 21–42% and 30–35%, respectively. A 24-h incubation of bovine C. parvum oocysts in the bacterial cell-free supernatants reduced oocyst viability 40–80% as determined by a flow cytometric assay and oocyst infectivity up to 95% as determined by the CCIF assay. These studies lend support to the hypothesis that production of anti-microbial compounds may be a mechanism by which LA and LR detrimentally affect bovine C. parvum and C. hominis.