. In vitro evaluation of the presence and inhibitory activity of bacteriocins from Lactobacillus supernatant.

M INDART; MJ RUIZ; MG DE YANIZ; G ARROYO; AI ECHEVERRÍA

Tucumán

Simposio; V International symposium on lactic acid bacteria benefitting from lactic acid bacteria progress in health and food.; 2016

CERELA, Tucumán

Lactic acid bacteria (LAB) such as Lactobacillus (L.) are used as probiotics. Probiotics are live microorganisms that, ingested in sufficient quantities, can have beneficial effects on the host, contributing to its intestinal balance and strengthening its immune system. They may have a significant effect in the treatment of gastrointestinal diseases in calves reared separately from cows. Bacteriocins production is considered as an action mechanism, as bacteriocins constitute a heterogeneous group of peptides or proteins of ribosomal synthesis with bactericide or bacteriostatic action. The objective of this study was to evaluate in vitro the presence of bacteriocins and their inhibitory capacity from L. buchneri (LB) and L. helveticus (LH) supernatant, against pathogenic microorganisms that produce neonatal diarrhea in calves. The Lactobacillus were isolated from a microbial community and biochemically and molecularly characterized. In order to evaluate the production of bacteriocins, the technique of diffusion in wells was used, using MRS broth plates with 1.2% agar of approximately 3 mm height, swabbed with a standardized suspension (1.5 x 108 CFU / ml) of a 18 h culture of incubation of the pathogenic strain, Salmonella spp. and Escherichia coli O157 EDL933 H7 (SETC). Wells 7mm diameter were made in the agar and inoculated with 50 µl of culture supernatant of the studied strain. Plates were incubated for 24 hours at 37 ° C. After that time, the diameter of the inhibition halos was measured (halos greater than 1 mm = inhibition). These tests were repeated with the concentrated supernatant by lyophilization, by this method it is possible to concentrate the protein with inhibitory activity, in order to evaluate differences in the antibacterial activity. Inhibition halos obtained with the supernatant against Salmonella spp. were of 6mm for LH and of 4mm for LB and, when concentrated for LH of 18mm and for LB of 10mm. As for SETC, for LH of 9mm and for LB of 5mm, when concentrated, the results were for LH 15mm and for LB 9mm.The results demonstrate that L.H. and L.B. supernatant showed substances compatible with bacteriocins, both Lactobacillus inhibited Salmonella spp. and SETC, pathogens that cause large production losses in dairy farms facilities. Significant inhibition differences were observed when the supernatant was concentrated. Detection of bacteriocins producing strains is important because it will allow further studies that may establish their potential use in the management and control of infectious processes in animal species of productive interest. However, further studies are required in order to purify and characterize such bacteriocins.