Probiotic properties of Lactobacillus casei – MYSRD 108 and Lactobacillus plantarum-MYSRD 71 with potential antimicrobial activity against Salmonella paratyphi

Abstract

A total of 130 isolates were screened, twelve isolates were characterized for probiotic attributes and two isolates with best probiotic features were evaluated in the study. Isolates MYSRD108 and MYSRD71 survived gastric conditions and were susceptible to tested antibiotics. Isolates showed more vital cell surface traits such as autoaggregation of 89.2 and 88.5% and cell surface hydrophobicity of 61 and 64%. PCR amplification followed by 16sRNA sequencing results confirmed that the isolates as Lactobacillus casei (MYSRD 108) and Lactobacillus plantarum (MYSRD 71). During this study, the Cells and their Cell Free Supernatant (CFS) were examined for antimicrobial activity. Both the isolates inhibited different bacterial pathogens in which the growth of S. paratyphi was significantly reduced. Further, their CFS also showed inhibitory effects against S. paratyphi with agar well diffusion and Minimum Inhibitory Concentration using Broth micro dilution method. The antimicrobial compounds in the CFS was characterized to different constraints such as pH neutralization, heat treatment, Hydrogen peroxide test and storage stability at -20> °C and represented that the antagonistic acitivity against Salmonella is due to the presence of organic acids in the supernatants that lowered the pH. These strains were further examined for the inhibition of S. paratyphi biofilm. The results indicated that CFS reduced S. paratyphi biofilm by more than 75% and the number of Salmonella biofilm was effectively reduced using 15% concentration of CFS. These strains may be used to produce antimicrobial compounds which can be a substitute for chemical preservatives in food industry.

Keywords: Biofilm inhibition; Cell-free supernatant (CFS); Lactobacillus casei; Lactobacillus plantarum; Probiotics; Salmonella paratyphi.