Studies on avian pathogenic Escherichia coli in commercial broiler chicken in South East Queensland

Abstract

Avian pathogenic Escherichia coli (APEC) is the causative agent of avian colibacillosis, a localised or systemic infection resulting in clinical diseases such as colisepticemia, chronic respiratory disease and swollen-head syndrome. Globally, avian colibacillosis is the leading cause of morbidity and mortality in poultry, and it has been associated with massive economic losses and welfare problems.This organism is of public health significance as APEC is communicable to humans. The diagnosis of avian colibacillosis relies on clinical signs, typical pathological lesions and culture of E. coli from affected tissue(s). Antimicrobial therapy is often used both for treatment and control. Previous overseas studies have characterised APEC and identified virulence genes (VGs) that can be used as molecular markers for the identification of APEC. Little is known about APEC in broiler chickens in Australia.The aim of this thesis was to gain a better understanding of the epidemiology of APEC in Australian broiler flocks and how factors including presence of VGs and phylogenetic group can improve the identification of this pathotype in Australia. Firstly, three faecal DNA extraction methods were evaluated. Faeces were collected from healthy chickens and chickens with colibacillosis from commercial broiler farms in South East Queensland (SEQ). The extracted DNA was screened by a pentaplex-PCR for five APEC-associated VGs (iroN, iutA, iss, hlyF and ompT). DNA extracted from E. coli isolates cultured from the cloaca and organs of the birds were screened using the same PCR.Repeated bead beating plus column elution was the preferred DNA extraction method, as it yielded good PCR quality and adequate quantity DNA. However, identifying APEC by direct detection of the five VGs from the faecal material was not feasible as all of these genes were also detected in all of the birds. However, the VGs were more commonly detected in E. coli isolates cultured from birds with colibacillosis.A cross-sectional study was performed to estimate APEC farm-level prevalence in healthy broiler chickens in SEQ and to identify potential risk factors associated with the carriage of APEC. At the farm-level, all of the 40 farms sampled were positive for APEC, that is at least one bird per farm carried APEC, while the within-farm prevalence was 63% (95% Confidence Interval: 55.8, 70.2).Higher APEC within-farm bird-level prevalence was significantly associated with the usage of well water as a source of drinking water, failure to disinfect the water line after each flock, farm visitors not showering before entering the shed, distances greater than 20 metres between the car park and the poultry shed and the presence of wild birds within 50 metres of the shed. Chlorinating the drinking water combined with automatic water filtration reduced within-farm bird-level APEC prevalence. Page | 3Therefore, based on the results concluded from the multivariable model, improving biosecurity and water treatments might reduce APEC prevalence, decrease the risk of co...

Whole genome sequence analysis of Australian avian pathogenic Escherichia coli that carry the class 1 integrase gene

“…This sample is of an ST which was reported in a study on FQR E. coli from canine faeces and cases of human ExPEC infection as a dominant lineage between both such sources [ 74 ], and therefore these gyrA / parC mutations are probably clonal. Additionally, analysis of APEC and Avian faecal E. coli (AFEC) in Australia identified strains of ST354 with FQR [ 75 ]. Otherwise, the APEC in our collection did not carry genes conferring resistance to antimicrobials important in the treatment of human disease, including cephalosporins, fluoroquinolones, carbapenems and colistin, an observation in stark contrast to those made on APEC isolated in many other countries.…”

“…Almost all 95 APEC carried the increased serum survival gene iss (91/95, 96 %), ompT (91/95, 96 %) and traT (90/95, 95 %), genes that have been epidemiologically associated with or determined experimentally to confer serum resistance in ExPEC [ 94–97 ]. A recent study on 50 Australian APEC reported identical carriage rates of iss and ompT [ 75 ]. The importance of the iss gene as a marker of APEC is reinforced by its inclusion in a diagnostic pentaplex PCR [ 37 ].…”

Growth Performance, Serum Biochemical Indices, Duodenal Histomorphology, and Cecal Microbiota of Broiler Chickens Fed on Diets Supplemented with Cinnamon Bark Powder at Prestarter and Starter Phases

“…In addition, [ 75 ] reported that there were fewer changes in microbial populations in the large intestine of animals than those in the small intestine due to their competition with the host for nutrients [ 76 ]. Moreover, E. coli is considered to be a part of the cecal microbiome and may become a pathogenic agent due to stress, poor welfare, host factors, or as a secondary infection [ 77 ]. Furthermore, E. coli may function as a reservoir for T3 by binding it to bacterial thyroid-binding hormone [ 78 ].…”

Characterization and antimicrobial sensitivity of biofilm producing Avian Pathogenic Escherichia coli from broiler chickens and their environment in India.

“…PCR primers targeting virulence genes for APEC characterization were used as per the literature (Johnson et al 2008;Awawdeh 2018) for detection of ve virulence genes (Table 2). The PCR was rst performed separately for each virulence gene as described by Johnson et al (2008) using APEC O2 as a positive control available in the department.…”

“…Previous studies have suggested that virulence factors are responsible for the pathogenicity of APEC (Dou et al 2015). Although there are several virulence factors related to the extraintestinal pathogenicity of APEC, hlyF, ompT, iroN, iss, and iutA carried on colV plasmid are considered as the most signi cantly associated with APEC strains and are widely used for characterization (Johnson et al 2008;Dou et al 2015;Awawdeh, 2018).…”