Response of young calves inoculated with lactic acid bacteria and challenged with Salmonella

FRIZZO, L.S.; SOTO, L.P.; ZBRUN, M.V.; BERTOZZI, E.; MARTI, L.E.; SEQUEIRA, G.; ROSMINI M.R.

San Miguel de Tucumán, Tucumán, Argentina

Simposio; III Simposio Internacional de II Bacterias Lácticas. Segundo Encuentro de la Red Argentina de Bacterias Lácticas (Red-BAL); 2009

CERELA-CONICET

Lactobacilli are common components in the normal intestinal microbiota, both in human beings and domestic animals. Competitive colonization by beneficial microorganisms like Lactobacillus sp. happens at an early age, in order to protect the host when is exposed to pathogens like Salmonella sp. and Escherichia coli. These two pathogens are the most frequent bacterial etiologic agents in calf scours during the first weeks of life. In the case of Salmonella sp., the increment in its isolation frequency shows that the current productive system is favorable for its development, especially when the hygienic practices during artificial rearing are deficient. The aim of study was to determine the capacity of an inoculum of lactic acid bacteria (LAB) of bovine origin to inhibit in vivo effects the Salmonella serotype Dublin DSPV 595T, and reduce the pathologic consequences in a conventional group of young calves. Fifteen calves divided into 3 groups (C-G, control group, LAB-G, LAB group and LAB-L-G, LAB lactose group), with 5, 6 and 4 animals each, respectively were used. LAB´s inoculum, formed by Lactobacillus casei DSPV318T, L. salivarius DSPV315T and Pediococcus acidilactici DSPV006T, resistant to rifampicin to differentiate them from the rest of the lactic intestinal flora, were administered together with the milk substitute. The LAB-G and LAB-L-G received a daily dose of 109 CFU/kg body weight of each strain throughout the experiment. Lactose was provided to the LAB-L-G in doses of 100 g/d. The pathogen administration was performed on all animals at 11th day of trial with 2 1010 CFU. Necropsies were performed on 1 animal/group/d since 11th day. Samples of liver, spleen and complete mesenteric and ileocaecal lymph nodules were analyzed to measure translocation in the internal medium. Homogenized samples were spread in the following medium: LAMVAB supplemented with rifampicine (administered inoculum), LAMVAB (Lactobacilli), VRBL (coliforms), SyB (enterococcus), BBA supplemented with Vit K1 and hemine (total aerobic bacteria) and XLD supplemented with novobiocin and nalidixic acid (Salmonella sp.). The target organs analyzed by histopathology (jejunum, ileum, ileocecal valve, mesenteric and ileocecal lymph node, liver and spleen) were processed using routine histological techniques. For the evaluation of histologic changes were identified specific indicators of injury for each organ, which allowed standardize routine observation, to assess the degree of modification of structures and to establish whether the animals had lesions compatible with salmonellosis. The pathogen translocated to the internal organ of all the animals as opposed to members of BAL inoculum used. The appearance of lesions, at the time of the necropsies, was clearly separated. In control group the lesions become visible in the first hours of infection and were severe, while in the animals inoculated with the probiotic the lesion were more delayed and inconstant. The percentage of lesions present throughout the full range of necropsies has always been lower in the treated groups, especially in the LAB-L-G. The probiotic did not interfere with the mechanism of entry of the pathogen but is demonstrating the capacity to modify the response of individuals to the pathogen attack, despite the high doses of Samonella.