Screening and characterization of lactic acid bacteria with antagonistic activities against Campylobacter jejuni from chicken manure

Abstract:

[Objective] This study is aimed to screen and identify new lactic acid bacteria (LAB) with antagonistic activities against Campylobacter jejuni from chicken manure, to understand their intestinal probiotic properties, and to probe the effects of LAB’s cell-free extracts on the virulence factor, flagella formation of C. jejuni. [Methods] The inhibition activities of 40 strains isolated from chicken manure were analyzed based on an oxford cup method to screen the strains with excellent antagonistic inhibitory effects on the indicator bacteria C. jejuni. The 16S rRNA gene-based technique was used to identify the selected strains. The adherence abilities of LAB strains to human intestinal epithelial cell (HT-29) were evaluated. The tolerance of LAB strains to artificial gastrointestinal juices was tested. Scanning electron microscopy was used to observe the effects of LAB’s cell-free extract on the flagella formation of C. jejuni. [Results] Forty LAB strains were isolated from chicken manure, among which X13, X14 and G20 strain showed the strongest antagonistic activities against C. jejuni. The 16S rRNA gene sequence analysis showed that X13, X14, and G20 strain were respectively identified as Lactobacillus reuteri, Lactobacillus salivarius and Lactobacillus gallinarum. HT-29 cell adhesion tests showed that the adhesion index of X13, X14, and G20 were respectively 11.5, 20.3, and 14.3 cells per HT-29 cell, such results suggests that all these three strains showed strong adhesion abilities to HT-29 cell. Tolerance tests to artificial gastrointestinal juices showed that all these three strains showed good capabilities. SEM observation showed that the cell-free extracts of these three strains were able to inhibit the flagella formation of C. jejuni. [Conclusion] Three selected LAB strains from chicken manure have inhibit the growth and the flagella formation of C. jejuni in vitro effectively, which suggested that such three LAB strains could be used as potential animal protective probiotics for the control of C. jejuni infection in vivo.

Key words:Lactobacillus from chicken, Campylobacter jejuni, Antagonism, Scanning electron microscopy