Evaluation of Expression Levels of Virulence Associated luxS, and ctxM Genes in Escherichia coli Isolated from Dairy Products Co-cultured with Bacillus coagulans

Abstract

The purpose of this study was the evaluation of expression levels of virulence associated luxS, and ctxM genes in Escherichia coli co-cultured with domestic probiotics. E. coli was isolated from 20 samples of dairy products (raw milk and cheeses). Then probiotic characteristics of Bacillus spp. isolated from intestinal tracts of poultry were assessed for ability to survive at acidic pH, bile salts, simulated gastric juice, production of bioactive compound and proteolytic activity. The isolate exhibited favorable characters, was identified by molecular method using 16SrDNA gene sequencing. Then expression levels of luxS, and ctxM genes in E. coli isolates in co-cultured with the probiotic isolates was evaluated by Real time-PCR method. The results obtained indicated that out of 16 E. coli isolates, two strains carried the genes. In addition, out of 12 Bacillus spp. isolates, one strain showed probiotic characters. The results on molecular identification verified the isolation of two strains of E. coli (carried luxS, and ctxM genes) and one strain of Bacillus coagulans. The results on expression levels of luxS, and ctxM genes in E. coli in co-cultured with Bacillus coagulans isolates indicated that expression levels of the genes diminished significantly (P-value<0.05). Hence, it can be interpreted that native spore-forming probiotic can greatly decrease virulence association gene expression in E. coli. Therefore, based on our finding it can be interpreted that the consumption of native probiotics as food supplement can greatly eliminate gastrointestinal diseases caused by E. coli. Hence, consumption of native probiotics potentially improves gut health. However, it needs more evaluation.

Keywords

• bacillus coagulans
• ctxm and luxs genes
• gene expression
• virulence genes