Cell-free culture supernatants of Lactobacillus spp. and Pediococcus spp. inhibit growth of pathogenic Escherichia coli isolated from pigs in Thailand

Abstract

Background Pathogenic Escherichia coli (E. coli) is an important causative agent for infectious diseases in pigs and causes significant economic loss. The global concern of antimicrobial resistance of bacteria raises awareness of the alternative ways of using antimicrobial peptides (AMPs). The study was aimed to identify and test the efficacy of AMPs from Lactobacillus spp. against the growth of pathogenic E. coli isolated from pigs in Thailand. Briefly, cell-free culture supernatants (CFCS) from 3 strains of lactic acid bacteria (LAB) consisting of Lactobacillus acidophilus (strain KMP), Lactobacillus plantarum (strain KMP), and Pediococcus pentosaceus (strain KMP) were tested against pathogenic E. coli via agar well diffusion assay in quadruplicates. The presence of a zone of inhibition (ZOI) around wells was evaluated at different incubation time. Acid and bile tolerance test was performed for bacterial viability in acid and bile salt conditions. In addition, LAB cross-streaking assay was evaluated for antagonist activity. Results The study showed that CFCS from L. acidophilus KMP, L. plantarum KMP, and P. pentosaceus KMP could inhibit the growth of pathogenic E. coli isolated from pigs in a time-dependent manner. To exemplify, the ZOI of L. plantarum KMP against E. coli (ETEC) at 8, 10, 12, 14, and 16 h incubation, were 26.6 ± 1.1, 24.9 ± 1.9, 22.5 ± 2.4, 20.3 ± 2.9, and 17.9 ± 3.3 mm, respectively. The ZOI was significantly different between 8, 10, 12, 14 h incubation, and the ZOI of the CFCS from L. plantarum KMP was larger than others (P-value < 0.05). Furthermore, L. acidophilus KMP, L. plantarum KMP, and P. pentosaceus KMP showed viability in pH 3.0, 0.3, and 0.5% (w/v) bile salt concentration. They exhibited no antagonist activity among each other. Conclusions According to the results, the CFCS from LAB including L. acidophilus KMP, L. plantarum KMP and P. pentosaceus KMP can inhibit the growth of pathogenic E. coli, isolated from pigs in Thailand. The antimicrobial activity observed was incubation time dependent.

Probiotic Potentiality from Versatile Lactiplantibacillus plantarum Strains as Resource to Enhance Freshwater Fish Health

“…The antimicrobial activity of CFSs were tested in accordance with the Kaewchomphunuch et al protocol [44]. As a negative control, 50 µL of MRS, adjusted to pH 3.8 with hydrochloric acid 1N (Sigma-Aldrich), was used.…”

“…As a negative control, 50 µL of MRS, adjusted to pH 3.8 with hydrochloric acid 1N (Sigma-Aldrich), was used. Antibacterial activity has been evaluated after 72 h, at 15 • C and 30 • C, measuring the diameter (mm) of the clear zone of inhibition (ZOI) around the inoculated wells [44]. The tests were conducted in triplicate.…”

“…In order to assess the ability of bacteria to survive acidic environments, 100 µL of bacterial suspension were transferred in test tubes containing 10 mL of MRS adjusted to pH 2.5 with 1 M HCl (Sigma-Aldrich; St. Louis, MO, USA). Similarly, to determine the bile tolerance, 100 µL of bacterial suspension were transferred in test tubes containing 10 mL of MRS enriched with 0.3% (w/v) of bile salts (cholic acid sodium salt, 50%; deoxycholic acid sodium salt, 50% Sigma-Aldrich) [44].…”

Characterization of Lactic Acid Bacteria from the Gut of Penaeus vannamei as Potential Probiotic

“…Organic acids, bacteriocins and hydrogen peroxide are the antimicrobial metabolites produced by probiotics (Ispirli et al, 2015). The cell free culture supernatant (CFCS) of L. acidophilus and P. pentosaceus found to inhibit the growth of E. coli strains, that may be due to the fact that several active constituents function together in CFCS (Kaewchomphunuch et al, 2022). Furthermore, the CFCS in our investigation requires additional research to identify active compounds in order to substantiate the inhibitory activity shown against the Vibrio spp.…”

“…Hydrophobicity of the isolates was performed by growing the isolates in MRS broth at 30C for 24 hours, centrifuged for 15 minutes at 3000 G. The resultant pellet was used for measurement cell-surface hydrophobicity (Liu et al, 2020). Cross streaking assay was done by streaking single colony of the isolates ON495586, ON491817, ON479264, ON478992, ON478991 and ON564885, incubating them anaerobically at 30C for 24 h on the MRS agar plates and examining for inhibition zone near the contact point of the streaking lines (Kaewchomphunuch et al, 2022). The statistical analysis was performed with SPSS Version 17.0 using one way ANOVA and mean comparison employing Duncan's multiple range test.…”