Investigating the association between organic acids and phenotypic alterations of avian pathogenic Escherichia coli

Abstract

The excessive use of antibiotics in agriculture is routinely described as a major contributor to bacterial resistance. Globally, antibiotics are widely used as growth supplements in livestock. This has led to concerns regarding human-use antibiotics in food and food-producing animals. Lately, organic acids (OAs) such as propionic acid (PA) and formic acid (FA) have been increasingly used as alternative antimicrobials or preservatives instead of antibiotics. These are particularly efficient at removing salmonella. Recently, we have shown that exposure of a Crohn’s Disease associated bacterial pathotype, Adherent-invasive Escherichia coli (AIEC), to PA significantly alters its phenotype resulting in increased adhesion and invasion of epithelial cells and increased persistence through biofilm formation. AIEC are both evolutionarily and phylogenetically related to avian pathogenic Escherichia coli (APEC), however the virulence mechanisms of APEC in poultry remain unclear. The widespread use of OAs as growth supplements and antimicrobials in the poultry industry is a rising concern due to the ability of OAs to alter the bacterial pathotype. In this study, we examined the effect of FA on the phenotype of APEC. We observed that following FA-exposure, APEC showed an increased ability to adhere to and invade human intestinal epithelial cells and form better biofilms both aerobically and anaerobically. Worryingly, these isolates also showed an increased resistance to several antibiotics. These results suggest that the increasing use of alternative antimicrobial such as FA in the poultry industry may lead to APEC strains that are increasingly virulent towards human cells with a potential for increased horizontal transmission