Thermal Adaptation Alters Response to Thermal Stress and Expression of Virulent Genes (eae, stx1, stx2, and hlyA) in Pathogenic Escherichia coli Isolated from Pork.

Escherichia coli encounter variety of environmental and processing stresses during their growth, survival, and infection. Herein, the thermotolerance behavior and transcription of virulent genes responsible for the pathogenicity in isolated strains of pathogenic E. coli were evaluated. Among 176 E. coli isolates, 4 isolates (2.27%) were confirmed to be pathogenic E. coli, out of which 2 isolates were positive for EHEC and 2 were positive for EPEC based on their virulence factors. Thermotolerance was induced under thermal adaptation at higher temperature, regardless of the pathotypes. Cells grown and adapted at 42 °C, exhibited highest transcription of genes associated with adhesion (eae), hemolysis (hlyA), and shiga toxin production (stx1). However, expression of these genes was downregulated in cells adapted at lower temperature of 4 °C and 25 °C compared to control. Further, transcription of stx2 was upregulated by 70% and 17% at 4 °C and 25 °C, respectively, while the transcription level was reduced by 44% relative to control at 42 °C. The findings indicate that expression of virulent genes in pathogenic E. coli at elevated temperature do not be depend on thermotolerance of the strain harboring these genes.

Presence of potent inhibitors of bacterial biofilm associated proteins is the key to Citrus limon's antibiofilm activity against pathogenic Escherichia coli.

In an era of antibiotic resistance where natural antibiotic substitutes are considered essential, the antimicrobial and antibiofilm activities of Citrus limon extract on strains of pathogenic Escherichia coli isolated from pork were evaluated. The strains which form biofilms were more resistant (MIC50 = 2.5 mgml-1) compared to non-biofilm forming strains (MIC50 = 1.25 mgml-1). Use of C. limon extract at 20 mgml-1 concentration has resulted in inhibition of biofilm formation by 53.96%. Cyclobarbital, 5, 8-dimethoxycumarin, orotic acid and 3-methylsalicylhydrazide were the major phytochemicals in C. limon extract with highest docking affinities against the biofilm associated proteins in E. coli. The results of simulation studies have clearly illustrated the energy stability of the protein-ligand complexes. Absorption, distribution, metabolism, excretion and toxicity (ADMET) profiles revealed that the phytochemicals in C. limon could be used in the drug design studies to preferentially target the specific receptors to combat biofilms associated with E. coli.