Infections with Avian Pathogenic and Fecal Escherichia coli Strains Display Similar Lung Histopathology and Macrophage Apoptosis

Abstract

The purpose of this study was to compare histopathological changes in the lungs of chickens infected with avian pathogenic (APEC) and avian fecal (Afecal) Escherichia coli strains, and to analyze how the interaction of the bacteria with avian macrophages relates to the outcome of the infection. Chickens were infected intratracheally with three APEC strains, MT78, IMT5155, and UEL17, and one non-pathogenic Afecal strain, IMT5104. The pathogenicity of the strains was assessed by isolating bacteria from lungs, kidneys, and spleens at 24 h post-infection (p.i.). Lungs were examined for histopathological changes at 12, 18, and 24 h p.i. Serial lung sections were stained with hematoxylin and eosin (HE), terminal deoxynucleotidyl dUTP nick end labeling (TUNEL) for detection of apoptotic cells, and an anti-O2 antibody for detection of MT78 and IMT5155. UEL17 and IMT5104 did not cause systemic infections and the extents of lung colonization were two orders of magnitude lower than for the septicemic strains MT78 and IMT5155, yet all four strains caused the same extent of inflammation in the lungs. The inflammation was localized; there were some congested areas next to unaffected areas. Only the inflamed regions became labeled with anti-O2 antibody. TUNEL labeling revealed the presence of apoptotic cells at 12 h p.i in the inflamed regions only, and before any necrotic foci could be seen. The TUNEL-positive cells were very likely dying heterophils, as evidenced by the purulent inflammation. Some of the dying cells observed in avian lungs in situ may also be macrophages, since all four avian E. coli induced caspase 3/7 activation in monolayers of HD11 avian macrophages. In summary, both pathogenic and non-pathogenic fecal strains of avian E. coli produce focal infections in the avian lung, and these are accompanied by inflammation and cell death in the infected areas.

Genomic and Functional Portrait of a Highly Virulent, CTX-M-15-Producing H 30-Rx Subclone of Escherichia coli Sequence Type 131

“…A previous study by Vimont et al (16) confirmed that the inflammatory responses of kidney cells after infection with ST131 versus non-ST131 were comparable. Also, Horn et al (51) observed similar histopathological outcomes in lung tissues after infection with pathogenic versus fecal avian E. coli. These observations, together with our results, suggest that the fitness and epidemiological success of ST131 strains are more relevant in the upstream steps involved at the onset of infection.…”

Effect of yeast cell product supplementation on broiler cecal microflora species and immune responses during an experimental coccidial infection

“…These pathogens can causes septicemia resulting in death and pericarditis, airsacculitis, and perihepatitis (Horn et al, 2012) of chickens. These pathogens can cause foodborne pathogen contamination for humans (Cruchaga et al, 2001).…”

Comparison of the prevalence of antibiotic-resistant Escherichia coli isolates from commercial-layer and free-range chickens in Arusha district, Tanzania

“…Although (Nakazato et al, 2009;Jakobsen et al, 2010). Avian pathogenic E. coli causes yolk-sac infections, respiratory-tract infections, bloodstream infections and colibacillosis (Yang et al, 2004;Horn et al, 2012). Transmission of these diseases accounts for significant losses for poultry producers (Ewers et al, 2009).…”