Bile Salt Hydrolase Activities: A Novel Target to Screen Anti-Giardia Lactobacilli?

Abstract

<i>Giardia duodenalis</i> is a protozoan parasite responsible for giardiasis, a disease characterized by intestinal malabsorption, diarrhea and abdominal pain in a large number of mammal species. Giardiasis is one of the most common intestinal parasitic diseases in the world and thus a high veterinary, and public health concern. It is well-established that some probiotic bacteria may confer protection against this parasite <i>in vitro</i> and <i>in vivo</i> and we recently documented the implication of bile-salt hydrolase (BSH)-like activities from strain La1 of <i>Lactobacillus johnsonii</i> as mediators of these effects <i>in vitro</i>. We showed that these activities were able to generate deconjugated bile salts that were toxic to the parasite. In the present study, a wide collection of lactobacilli strains from different ecological origins was screened to assay their anti-giardial effects. Our results revealed that the anti-parasitic effects of some of the strains tested were well-correlated with the expression of BSH-like activities. The two most active strains <i>in vitro</i>, La1 and <i>Lactobacillus gasseri</i> CNCM I-4884, were then tested for their capacity to influence <i>G. duodenalis</i> infection in a suckling mice model. Strikingly, only <i>L. gasseri</i> CNCM I-4884 strain was able to significantly antagonize parasite growth with a dramatic reduction of the trophozoites load in the small intestine. Moreover, this strain also significantly reduced the fecal excretion of <i>Giardia</i> cysts after 5 days of treatment, which could contribute to blocking the transmission of the parasite, in contrast of La1 where no effect was observed. This study represents a step toward the development of new prophylactic strategies to combat <i>G. duodenalis</i> infection in both humans and animals.