A compilation of virulence-associated genes that are frequently reported in avian pathogenic Escherichia coli (APEC) compared to other E. coli

Authors: OVI, FOZOL - Mississippi State University; ZHANG, LI - Mississippi State University; NABORS, HALEY - Mississippi State University; JIA, LINAN - Mississippi State University; ADHIKARI, PRATIMA - Mississippi State University

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2022
Publication Date: 2/8/2023
Citation: Ovi, F., Zhang, L., Nabors, H., Jia, L., Adhikari, P. 2023. A compilation of virulence-associated genes that are frequently reported in avian pathogenic Escherichia coli (APEC) compared to other E. coli. Journal of Applied Microbiology. 134(3). Article lxad014. https://doi.org/10.1093/jambio/lxad014.
DOI: https://doi.org/10.1093/jambio/lxad014

Interpretive Summary: The bacterium Escherichia coli (E.coli) can be associated with a wide variety of environments and within a variety of hosts. The bacterium can be pathogenic or non-pathogenic. The genome of E. coli isolates can vary widely and is responsible for the variations among E.coli isolates. Strains of E.coli associated with infections in chickens have been shown contain specific genes or combinations of genes within their genome. To identify all E.coli genes associated with disease or infections in chickens, previous literature was reviewed. From this review, 10 key virulence genes were identified.

Technical Abstract: Escherichia coli survive in various hosts and environments due to their highly diversified genome. These bacteria have coevolved with humans, colonized a broad range of hosts, and survive as a commensal organism or pathogen. Escherichia coli that adopted a pathogenic lifecycle in avian hosts typically belong to phylogroups B2 and D. Phylogenic investigations discovered these E. coli are noticeably overlapped with the phylogroup of E. coli infecting humans. This overlapping is possibly due to a parallel evolution in both hosts from a common ancestor, which indicates a high zoonotic potential of avian pathogenic E. coli (APEC). However, some contrasting evidence of other phylogroups infecting the avian host has also been reported in recent studies indicating phylogroups of E. coli are not definitive, only suggestive to their virulence in chickens. Furthermore, virulence-associated genes that contribute to bacterial features necessary to establish APEC infection, are predominantly located in plasmids. Therefore, phylogenetic classification based on chromosomal markers is often inadequate to identify APEC. Moreover, E. coli can obtain virulent plasmids from other bacteria, which further complicates the link between phylogenetic classification and pathotype. Previous research has reported an array of virulence-associated genes highly prevalent only in APEC isolates. Function of these genes are possibly a prerequisite to establishing APEC infections in chickens. Consequently, these genes can be used to distinguish APEC from environmental, commensal, intestinal, and other extraintestinal E. coli. Therefore, we have extensively reviewed previous literature to compile the virulence-associated genes that are highly prevalent in APEC compared to other E. coli. From this review, we have identified 10 key virulence-associated genes (iss, tsh, iroN, episomal/chromosomal ompT, iutA, cvaC, hlyF, iucD, papG allel (II/III), and papC) that are frequently reported in APEC isolates than nonpathogenic E. coli. A compilation of these research findings can be crucial to the molecular identification of APEC. Furthermore, it can serve as a guideline for future investigation and aid in formulation of intervention strategies.