Avian Pathogenic Escherichia coli (APEC): An Overview of Virulence and Pathogenesis Factors, Zoonotic Potential, and Control Strategies

Abstract

Avian pathogenic Escherichia coli (APEC) causes colibacillosis in avian species, and recent reports have suggested APEC as a potential foodborne zoonotic pathogen. Herein, we discuss the virulence and pathogenesis factors of APEC, review the zoonotic potential, provide the current status of antibiotic resistance and progress in vaccine development, and summarize the alternative control measures being investigated. In addition to the known virulence factors, several other factors including quorum sensing system, secretion systems, two-component systems, transcriptional regulators, and genes associated with metabolism also contribute to APEC pathogenesis. The clear understanding of these factors will help in developing new effective treatments. The APEC isolates (particularly belonging to ST95 and ST131 or O1, O2, and O18) have genetic similarities and commonalities in virulence genes with human uropathogenic E. coli (UPEC) and neonatal meningitis E. coli (NMEC) and abilities to cause urinary tract infections and meningitis in humans. Therefore, the zoonotic potential of APEC cannot be undervalued. APEC resistance to almost all classes of antibiotics, including carbapenems, has been already reported. There is a need for an effective APEC vaccine that can provide protection against diverse APEC serotypes. Alternative therapies, especially the virulence inhibitors, can provide a novel solution with less likelihood of developing resistance.

Prevalence and Genetic Relationship of Predominant Escherichia coli Serotypes Isolated from Poultry, Wild Animals, and Environment in the Mekong Delta, Vietnam

“…Avian pathogenic E. coli is the major causative agent of avian colibacillosis that is considered one of the most important bacterial diseases in the global poultry industry due to its substantial economic impacts [ 2 , 30 ]. In addition to causing serious consequences on poultry health and production, several APEC strains have been determined as potential zoonotic pathogens [ 4 – 7 ]. Therefore, comprehensive knowledge of biological and epidemiological characteristics of APEC is critical to reducing the incidence of avian colibacillosis in poultry production and threats to human health.…”

“…In this study, all 975 E. coli strains were subjected to serotyping using conventional PCR. As literature review, APEC serotypes O1, O2, O18, and O78 were targets for the present serotyping since it has been widely reported that E. coli strains in these serotypes are the most common APEC pathotypes causing colibacillosis in animals and human [ 7 , 33 ]. A total of 335 E. coli out of 975 (34.35%) E. coli strains were defined as belonging to the serotypes O1, O2, O18, and O78 ( Figure 2(a) ).…”

“…Thus, APEC is responsible for severe economic and clinical consequences to poultry production worldwide [ 3 ]. Besides the serious impacts on poultry health, many recent studies have indicated that a subset of APEC might cause zoonotic infections, posing a real threat to public health [ 4 – 7 ].…”

Antibiotic Resistance and Virulence Profiles of Escherichia coli Strains Isolated from Wild Birds in Poland

“…APEC strains produce a variety of virulence factors facilitating host tissue colonization, including adhesins (encoded by papC and tsh ), iron uptake systems ( iutA , irp2 , sit and iroN ), serum resistance ( iss , ompT and kpsII ), toxins ( vat ), and others ( cvi/cva and etsB ) [ 5 ]. Many genes coding for these virulence factors are often clustered together on chromosomes and plasmids and can be transmitted by horizontal gene transfer [ 6 ].…”

Novel Small Molecule Growth Inhibitor Affecting Bacterial Outer Membrane Reduces Extraintestinal Pathogenic Escherichia coli (ExPEC) Infection in Avian Model

“…APEC is a very common bacterial pathogen of poultry, including chickens, turkeys, and ducks, and of many other avian species ( 6 , 7 ). It is widely prevalent in all age groups of chickens (9.52 to 36.73%), with specifically high prevalence in adult layer birds (36.73%) ( 8 ).…”