Effect of Lactobacillus and Bifidobacterium on Cryptosporidium parvum oocyst viability Original Research Article

Cryptosporidium parvum, an opportunistic protozoan parasite of humans and animals worldwide, causes diarrheal disease that is typically self-limiting in immunocompetent hosts but often life-threatening to immunocompromised individuals. Clinical management of cryptosporidiosis has been hampered by the lack of effective anti-cryptosporidial drugs. In vivo studies in mice have demonstrated that administering live bacterial cell supplements (probiotics) prior to challenge with C. parvum reduces the severity and duration of symptoms associated with cryptosporidiosis. It has been suggested that probiotics may inhibit infection through excretion of substances harmful to one of the parasiteʹs developmental stages and possibly offer new therapeutic agents for the treatment of cryptosporidiosis. We evaluated the in vitro effect of four common food fermenting bacteria derived from human intestines (Lactobacillus acidophilus, L. reuteri, Bifidobacterium breve and B. longum) on the oocyst (infective) stage of C. parvum using a novel flow cytometric viability assay. Compared to broth controls, Lactobacillus supernatants significantly reduced oocyst viability up to 81% whereas Bifidobacterium supernatants reduced viability only 10–37%. These results suggest the presence of anti-microbial substance(s) against the oocyst stage of C. parvum in the supernatants of L. reuteri and L. acidophilus broth cultures. Further study is needed to delineate the nature and identity of the factor(s) involved.