In vitro assessment of antibacterial activity from Lactobacillus spp. strains against virulent Salmonella species isolated from slaughter animals in Benin

Background and aim: Salmonella spp. are among the world's leading foodborne pathogens, found naturally in the intestines of many animals. Lactic acid bacteria, mainly Lactobacillus, are a promising alternative to antibiotics for animal and human health. This study aimed to assess the in vitro antibacterial activity of Lactobacillus spp. strains against virulent Salmonella spp. isolated from slaughter animals in Benin.

Materials and methods: Eleven samples of raw cow's milk, five samples of breast milk, and six infant stool samples were taken. From these samples, strains of Lactobacillus were isolated and identified. The probiotic potential of each of the identified strains was characterized, and finally in vitro antibacterial activity of these strains was evaluated against three virulent strains of Salmonella spp. and a reference strain of Salmonella Typhimurium ATCC 14028.

Results: Out of the 22 samples collected, 20 strains of Lactobacillus spp. were isolated and identified. These strains included Lactobacillus plantarum (30%), Lactobacillus delbrueckii (25%), Lactobacillus casei (25%), Lactobacillus salivarius (15%), and Lactobacillus acidophilus (05%). Characterization of the probiotic potential of these strains showed that only 16 strains were resistant to pH=1.5. Fourteen of them were able to withstand the simulated gastric juice (pH 1.5+pepsin). The 14 probiotic strains showed very good antibacterial activity against virulent strains of Salmonella spp. with inhibition zone diameters ranging from 12.36±0.03 mm to 35.33±0.05 mm (R values>6 mm).

Conclusion: From this study, Lactobacillus strains isolated from raw cow milk, breast milk, and infantile stool might be used as some valid candidates for probiotics. It also represents good alternatives for antibiotics in the fight against animal and human salmonellosis.