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

Thibault Allain,Isabelle Valle,Marie-Agnès Travers,Myriam Thomas,Isabelle Florent,Luis G Bermúdez-Humarán,Philippe Langella,Bruno Polack,Soraya Chaouch,Philippe Grellier

doi:10.3389/fmicb.2018.00089

Abstract

Giardia duodenalis 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 in vitro and in vivo and we recently documented the implication of bile-salt hydrolase (BSH)-like activities from strain La1 of Lactobacillus johnsonii as mediators of these effects in vitro. 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 in vitro, La1 and Lactobacillus gasseri CNCM I-4884, were then tested for their capacity to influence G. duodenalis infection in a suckling mice model. Strikingly, only L. gasseri 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 Giardia 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 G. duodenalis infection in both humans and animals.

Highlights

Giardia duodenalis is the etiologic agent of the zoonotic disease giardiasis, one of the most common waterborne parasitic infections globally
Our results showed that L. gasseri CNCM I-4884 displayed a higher anti-giardial effect in vivo than La1, with an almost complete clearance of Giardia infection in suckling mice
The 29 strains tested in this study were able to grow in MRS-agar supplemented with 0.5% Tauro-deoxycholic acid (TDCA) whereas only 25 grew in MRSagar supplemented with 0.5% Glyco-deoxycholic acid (GDCA), supporting that GDCA has a higher bactericidal activity than TDCA in vivo (Begley et al, 2006)

Summary

Introduction

Giardia duodenalis ( known as G. lamblia or G. intestinalis) is the etiologic agent of the zoonotic disease giardiasis, one of the most common waterborne parasitic infections globally. G. duodenalis is a flagellate protozoan (Excavata, Diplomonad) that infects a broad diversity of animals such as humans, mammals, reptiles and birds (Thompson and Monis, 2004, 2012). Role of BSH in the Anti-giardial Effect of Lactobacilli exposure to gastric acid and proteases in the stomach leads to excystation and liberation of replicative trophozoite stages that adhere transiently to the proximal small intestine and persist for several days (for up to several months in some cases) (Reiner et al, 2003) After this replicative and pathogenic stage, trophozoites are carried into the colon and progressively encyst. Cysts, released through host feces, may survive in the environment for several months and remain infectious at low doses (Thompson et al, 1993)

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