Protective effect of potential probiotic strains from fermented Ethiopian 3 food against Salmonella enterica serovar Typhimurium DT104 in mice. Bacteria

Salmonella is one of the most harmful pathogens responsible for foodborne illnesses and deaths. The aim of this study was to evaluate the effect of potentially probiotic lactic acid bacteria (LAB) strains against Salmonella Typhimurium DT104 in mice. The compatibility between the selected potential probiotic LAB strains (Lactobacillus plantarum K132, Lactobacillus paracasei K114 and Lactococcus lactis E124) was determined using the cross-streak method and there was no antagonism found between them. The anti-Salmonella activities of co-culture of the isolated probiotics in the form of mixed strains or single culture was carried out and showed a remarkable anti-Salmonella activity with 96.50 to 100% growth inhibition. The combination of strains that showed the highest growth inhibition rates against Salmonella enterica serovar Typhimurium DT104, were used to test their effect on the colonization of mice by Salmonella Typhimurium DT104. White albino male mice were pretreated with the mixed probiotics for 7 days, infected with Salmonella Typhimurium DT104 for 1 day. A total of 3 treatments were applied, during which the negative control group was treated with phosphate-buffered saline (PBS, group 1); positive control group (group 2, typ) was challenged with Salmonella Typhimurium DT104 alone. Group 3 (pro-typ) was pretreated with mixed probiotic culture and then infected with Salmonella Typhimurium DT104. Survival rate of mice and counts of Salmonella in feces were recorded. The survival rate of mice on day 21 after the oral challenge with Salmonella Typhimurium DT104 was significantly higher (p<0.05) in the experimental pro-typ group (100% survival) when compared with the positive control group (group 2) (20% survival). Viable cell counts of Salmonella in feces were significantly lower (p < 0.05) for the pro-typ group compared to the typ group. In conclusion, the combination of potential probiotic strains was able to protect mice against Salmonella Typhimurium DT104 infection, thus demonstrates their potential to be used as probiotic cultures.