Protective capacity of bifidobacteria administered as fresh or spray dried cultures against Salmonella Typhimurium

Abstract

Bifidobacterium animalis subsp. lactis INL1 is an autochtonous strain isolated from breast milk.B.lactis Bb12 is one of the commercial strains most used worldwide. The aim of the study was to assess the effect of spray drying on the protective capacity against Salmonella enterica serovar Typhimurium. Male BALB/c mice (6 weeks-old) (7-9 animals/group) received (10 days) 5x108 CFU of the strains as fresh cultures in milk (INL1-F and Bb12-F) or spray dried and reconstituted (INL1-S and Bb12-S), or 20% skim milk (control of infection I and II). At day 11 animals were challenged with 106 CFU of Salmonella typhimurium Malbrán. By day 6 postchallenge, the surviving animals were sacrificed. The translocation assay was carried out in blood, liver, spleen, mesenteric lymph nodes and Peyer?s patches. Intestinal content and feces were obtained to determine total and anti-Salmonella secretory IgA (ELISA test). Small andlarge intestines were also obtained in order to determine the level of IFN-γ, TNF- and IL-10 (ELISA test). No significant differences were observed in the proportion of dead/total animals for each strain compared to their corresponding control (p=0.053 and p=0.071 for Bb12 and INL1, respectively, Barnard´s test). However, when results were considered grouped by the technology applied, a significant reduction in this proportion was observed (p=0.008) foranimals that received spray-dried cultures (0/15) compared to those that received fresh cultures (5/15) or controls (6/18). No significant differences were observed in the levels of translocation to internal organs. Total S-IgA in feces was higher in the group that received Bb12-S (p=0.011) whereas no differences were observed in the anti-Salmonella S-IgA. Levels of IL-10 weresignificantly reduced in the small and large intestine of mice of the Bb12-S group, compared to the control group. No difference was observed for IFN-γ and TNF-. Due to the reduced sample size, these results must be considered preliminary. However, they suggest that spray drying might be a useful tool to develop dehydrated functional cultures. Results observed may be due to the fact that animals received the same amount of viable cells. However, animals thatreceived spray-dried cultures may have received a higher amount of total cells as spray dried cultures generally contain a small proportion of heat-inactivated cells.