Protective effect of L. casei CRL 431 against Salmonella in a mouse model: Mechanisms involved

Abstract

Salmonella species are Gram-negative bacilli that constitute the causing agents of several animal and human illnesses. They cause acute or chronic infections that can be local (e.g gastroenteritis produced by non-typhoidal serovars) or systemic (e.g. enteric fever produced by typhoidal serovars). Non-typhoidal serovars produce 93.8 million cases of gastroenteritis worldwide, leading to 155,000 deaths each year. According to a foodborne disease surveillance network data supported by the World Health Organization (2001-2005), S. Enteritidis was the most common serotype worldwide (65% of the isolates), followed by S. Typhimurium (12%) and S. Newport (4%). Numerous studies have proposed the use of probiotics to improve gut health, especially in the protection against this pathogen. Here, we report the case of the probiotic strain L. casei CRL 431 which showed protective skills against S. Typhimurium in BALB/c mice, and unveil the main biological and immune mechanisms involved in the protective effect observed. Part of this study was also performed with other two lactobacilli strains: L. delbruekii subsp. bulgaricus CRL 423 and L. acidophilus CRL 730, which displayed immunostimulating ability, but showed no protective capacity against Salmonella. This comparative study was conducted to define what effects on the mucosal immune system would be desired in a probiotic strain to achieve protection against this particular pathogen.