Department of Poultry Science, Mississippi State University, 325 Wise center Dr. Mississippi State University Mississippi State, MS 39762.
J Appl Microbiol. 2023 Mar 1;134(3). doi: 10.1093/jambio/lxad014.
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.
大肠杆菌由于其高度多样化的基因组而在各种宿主和环境中生存。这些细菌与人类共同进化，定植于广泛的宿主，并作为共生体或病原体生存。在禽类宿主中采用致病性生命周期的大肠杆菌通常属于 B2 和 D 群。系统发育研究发现，这些大肠杆菌与感染人类的大肠杆菌的菌群明显重叠。这种重叠可能是由于来自共同祖先的两个宿主的平行进化，这表明禽源致病性大肠杆菌（APEC）具有很高的人畜共患病潜力。然而，最近的一些研究也报道了其他菌群感染禽类宿主的相反证据，这表明大肠杆菌的菌群不是其在鸡中致病性的决定性因素，而只是提示性的。此外，有助于建立 APEC 感染的细菌特征的毒力相关基因主要位于质粒上。因此，基于染色体标记的系统发育分类通常不足以识别 APEC。此外，大肠杆菌可以从其他细菌中获得毒力质粒，这进一步增加了系统发育分类与病原体型之间的联系的复杂性。先前的研究报告了 array 高度流行于仅在 APEC 分离株中的毒力相关基因。这些基因的功能可能是在鸡中建立 APEC 感染的先决条件。因此，这些基因可用于区分 APEC 与环境、共生、肠道和其他肠外大肠杆菌。因此，我们广泛回顾了以前的文献，以编译与其他大肠杆菌相比在 APEC 中高度流行的毒力相关基因。通过这项综述，我们确定了 10 个关键的毒力相关基因（iss、tsh、iroN、episomal/chromosomal ompT、iutA、cvaC、hlyF、iucD、papG allel(II/III) 和 papC），这些基因在 APEC 分离株中比非致病性大肠杆菌更为常见。这些研究结果的汇编对于 APEC 的分子鉴定至关重要。此外，它可以作为未来研究的指导，并有助于制定干预策略。
