Abstract
Background and Aim:Escherichia coli is the cause of avian colibacillosis, a significant threat to the poultry industry and public health. Thus, this study investigated the prevalence of E. coli in diseased chicken broilers, pathological effects of these bacteria, and interleukin (IL) gene expression of different serotypes of E. coli (O78, O26, O44, and O55) on experimentally infected chickens.Materials and Methods:A total of 295 organ samples (liver, lungs, heart, and spleen) from 59 diseased broiler chickens were used for conventional identification of E. coli. Chickens were orally infected with one of the following E. coli serotypes (O78, O26, O44, or O55) and examined for clinical signs, mortality, macroscopic and microscopic lesions, and IL gene expression using real-time quantitative polymerase chain reaction.Results:E. coli was isolated from 53.2% of broiler chicken organs with a high prevalence in lungs (26.1%). The most prevalent serotypes were O78, O26, O44, O55, O157, and O127 prevalence of 27.8, 22.2, 16.7, 16.7, 5.6, and 5.6%, respectively. In the experimental design, five groups (G1-G5) of birds were established. G1 served as the negative control group, while G2-G5 were challenged orally with E. coli O78, O26, O55, or O44, respectively. Chickens infected with E. coli O78 or O26 showed significant clinical signs in comparison to the other infected birds. Mortality (13.3%) was only observed in birds infected with E. coli O78. Necropsy of dead birds after E. coli O78 infection showed pericarditis, enteritis, airsacculitis, and liver and lung congestion. More severe histopathological changes were observed in intestines, spleen, liver, and lung from chickens infected with either E. coli O78 or O26 than for birds infected with other serotypes. On the 2nd day post-infection, E. coli challenge, particularly with E. coli O78, displayed significantly upregulated levels of ileal IL-6 and IL-8, but ileal IL-10 level tended to be downregulated in comparison to the control group.Conclusion:This study assessed the application of cytokines as therapeutic agents against infectious diseases, particularly colibacillosis.
Highlights
Escherichia coli (E. coli) is a typical microorganism in chicken intestinal tracts and trachea to a lesser degree [1]
More severe histopathological changes were observed in intestines, spleen, liver, and lung from chickens infected with either E. coli O78 or O26 than for birds infected with other serotypes
Gene expression in this study showed a relationship between pro-inflammatory cytokine levels (IL-6, IL-8, and IL10) and the challenge induced by various E. coli serotypes in broiler chickens
Summary
Escherichia coli (E. coli) is a typical microorganism in chicken intestinal tracts and trachea to a lesser degree [1]. Even common “non-pathogenic” strains of E. coli cause infection in animals, humans, birds, and weakened or immunocompromised hosts or when gastrointestinal barriers are breached. Some strains of E. coli invade the body and cause avian colibacillosis, a fatal systemic disease [2]. Signs of colibacillosis in poultry include infection of yolk sacs, omphalitis, hepatitis, pericarditis, septicemia, polyserositis, enteritis, cellulitis, respiratory tract infection, and salpingitis [3]. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Escherichia coli is the cause of avian colibacillosis, a significant threat to the poultry industry and public health. This study investigated the prevalence of E. coli in diseased chicken broilers, pathological effects of these bacteria, and interleukin (IL) gene expression of different serotypes of E. coli (O78, O26, O44, and O55) on experimentally infected chickens
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