A bile salt hydrolase of Brucella abortus contributes to the establishment of a successful infection through the oral route in mice.

M. VICTORIA DELPINO; M. INÉS MARCHESSINI; SILVIA M ESTEIN; DIEGO J COMERCI; JULIANA CASSATARO; CARLOS A FOSSATI; PABLO C BALDI

INFECTION AND IMMUNITY

AMER SOC MICROBIOLOGY

Año: 2006 p. 299 - 305

0019-9567

                                                                Abstract Choloylglycine hydrolase (CGH), a bile salt hydrolase, has been annotated in all the available genomes of Brucella species. We obtained the Brucella CGH in recombinant form and demonstrated in vitro its capacity to cleave glycocholate into glycine and cholate. B. abortus 2308 (wild-type) and its isogenic _cgh deletion mutant exhibited a similar growth in tryptic soy broth in the absence of bile. In contrast, the growth of the _cgh mutant was notably impaired by both 5% and 10% bile. Bile resistance of the complemented mutant was similar to that of the wild-type strain. In mice infected through the intragastric or the intraperitoneal route, splenic infection was significantly lower at 10 and 20 days p.i. in animals infected with the _cgh mutant than in those infected with the wild-type strain. For both routes, no differences in spleen CFU were found between animals infected with the wild type strain or the complemented mutant. Mice immunized intragastrically with recombinant CGH mixed with cholera toxin (CGH/CT) developed a specific mucosal humoral (IgG and IgA) and cellular (IL-2) immune response. Fifteen days after challenge by the same route with live B. abortus 2308, splenic CFU counts were ten-fold lower in mice immunized with CGH/CT than in mice immunized with CT or PBS. This study shows that CGH confers Brucella the ability to resist the antimicrobial action of bile salts. The results also suggest that CGH may contribute to the ability of Brucella to infect the host through the oral route.