Antagonistic activity of Lactobacillus rhamnosus LbRE-LSAS and some Bifidobacterium sp against Shigella sonnei

Abstract

Since their discovery, antibiotics have been one of the most useful tools in the struggle against infectious disease. However, due to their overuse, numerous pathogens developed multiple resistances against antibiotics. Searching and studying antagonistic GRAS (generally recognized as save) bacteria is a promising field to find innovating treatment against infectious diseases. Lactic acid bacteria and Bifidobacterium are GRAS bacteria well known for their antagonistic effect on other microorganisms including pathogens such as Shigella sonnei. The antagonistic activity of Lactobacillus rham-nosus LbRE-LSAS strain and four strains of Bifidobacterium genera: longum (Bl431 and Bl432), bifidum (Bb442) and animalis. sbsp lactis (Bb12), was evaluated using two different techniques: Spot On Agar Test (SPAT) and Agar well diffusion test (AWDT) against Shigella sonnei (Ss CECT 457), Micrococcus luteus (M1-CECT241) and five lactic indicator strains: Carnobacterium maltoaromaticum CECT 5805), Lactobacillus plantarum (LbP CECT 748), Pedio-coccus pentosaceus (Pp CECT 4695), Lactobacillus acidophilus (LbA CECT 4529), Lactobacillus sakei (Lbs 673). We noted a maximum diameter of the inhibition zone by SPAT technique with strain the Bb12 (16.67 mm) followed by the strain LbRE-LSAS (16.42 mm). However, the maximum diameter of the inhibition zone using SPAT technique was obtained with the strain Bb12 (11.89 mm) followed by the strain LbRE-LSAS (11.11 mm). The antagonistic activity against Shigella sonnei was also evaluated using the coculture method. The maximum inhibition observed after 24 h of coculture was 6.54 log recorded with the strain LbRE-LSAS. Through these results we can clearly deduce the antagonistic potential of the two strains Lactobacillus rhamnosus LbRE-LSAS and Bifidobacterium longum Bl431, as to prevent or treat any shigellosis caused by Shigella sonnei.