Resistance gene profiles and expression patterns in Escherichia coli isolates from swine with colibacillosis

Swine colibacillosis, caused by colonization of the piglet small intestine with enterotoxigenic strains of Escherichia coli, imposes a significant economic burden on the swine industry. Due to high mortality rates and the emergence of antimicrobial resistance, it is considered one of the major welfare concerns in the livestock industry. This study elucidated the genetic basis and expression patterns of key antibiotic resistance genes in porcine E. coli isolates with colibacillosis. Intestinal contents from five affected piglets were subjected to high-throughput sequencing, revealing ۲۶ resistance genes across seven antibiotic classes. Four strains (۴۲۸, ۴۳۰, ۴۳۲, ۴۳۳) were further analyzed for mRNA expression levels of six resistance genes (blaTEM, tetA, tetB, tetM, qnrB, and qnrS) under exposure to ampicillin, tetracycline and ciprofloxacin at three concentrations (۰.۰۱, ۰.۰۰۱, ۰.۰۰۰۱% w/v). Our findings revealed five distinct expression patterns: (۱) dose dependent upregulation/downregulation, (۲) inverse response to concentration changes, (۳) maximal downregulation at intermediate dose, (۴) minimal down-regulation at intermediate dose, and (۵) sustained upregulation. Strain ۴۲۸ uniformly followed pattern one for all resistance genes, in strain ۴۳۰, tetB followed pattern three while blaTEM matched pattern one, strain ۴۳۲ exhibited patterns two for all tetracycline- and β-lactam-resistance genes, and pattern four for qnrB; strain ۴۳۳ showed patterns three for both fluoroquinolone-resistance genes, pattern four for tetB, and pattern five for blaTEM. These findings highlighted strain-specific and dose-dependent gene expression responses in swine colibacillosis. This work underscored the need for tailored antibiotic strategies, targeted interventions and well-validated monitoring frameworks for antibiotic resistance in veterinary.

کلیدواژه ها:

Antibiotic resistance ، beta-Lactams ، Fluoroquinolones ، Pig ، Tetracyclines