Characterisation of avian pathogenic Escherichia coli (APEC) associated with colisepticaemia compared to faecal isolates from healthy birds.
ABSTRACT A total of 114 avian pathogenic Escherichia coli (APEC) isolates were collected from cases of colisepticaemia occurring in broilers (77) and layers (37) within Ireland. In addition 45 strains isolated from faeces of healthy birds were included for comparison. All isolates were serogrouped, and examined for known virulence factors, mostly by PCR. The O78 serogroup represented 55 and 27% of broiler and layer colisepticaemic isolates respectively. All isolates were positive for curli fimbriae (crl, csg) and negative for afimbrial adhesin (afa). S-fimbrial (sfa) sequences were present in 8.8% of septicaemic isolates and 8.9% of healthy bird isolates. The majority of E. coli from cases of colisepticaemia (97.4%) and healthy bird (95.6%) isolates were positive for aerobactin (aer), and temperature sensitive haemagglutinin (tsh) was similarly detected in high numbers in 93.9 and 93.3%, respectively. In comparison to E. coli isolates from the faeces of healthy birds, a significantly higher percentage of isolates from septicaemic cases possessed Type 1 fimbriae (fimC) and increased serum survival (iss) gene sequences. Forty-seven (41.2%) isolates from septicaemic birds possessed P-fimbriae (pap) gene sequences, compared with only 15.6% from E. coli isolated from healthy birds. Haemolysin (hlyE) sequences were detected in 46.7% of isolates from healthy birds in comparison with 6.1% of septicaemic isolates. Sequences encoding colicin V (cvaC) were detected in 99.1% of septicaemic isolates and 82.2% of isolates from healthy birds. The K1 capsule was only present in two septicaemic isolates, both taken from layers. Motility was detected in 36.8% of E. coli isolated from cases of septicaemia, compared with 93.3% of isolates from healthy birds. These results demonstrate the presence of 11 virulence genes in E. coli isolated from cases of colisepticaemia within Ireland, and indicate the prevalence of iss and fimC.
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ABSTRACT: Escherichia coli (E. coli) infections are very widespread in poultry. However, little is known about the interaction between the intestinal epithelium and E. coli in chickens. Therefore, the effects of avian non-pathogenic and avian pathogenic Escherichia coli (APEC) on the intestinal function of broiler chickens were investigated by measuring the electrogenic ion transport across the isolated jejunal mucosa. In addition, the intestinal epithelial responses to cholera toxin, histamine and carbamoylcholine (carbachol) were evaluated following an E. coli exposure. Jejunal tissues from 5-week-old broilers were exposed to 6×108 CFU/mL of either avian non-pathogenic E. coli IMT11322 (Ont:H16) or avian pathogenic E. coli IMT4529 (O24:H4) in Ussing chambers and electrophysiological variables were monitored for 1 h. After incubation with E. coli for 1 h, either cholera toxin (1 mg/L), histamine (100 μM) or carbachol (100 μM) were added to the incubation medium. Both strains of avian E. coli (non-pathogenic and pathogenic) reduced epithelial ion conductance (Gt) and short-circuit current (Isc). The decrease in ion conductance after exposure to avian pathogenic E. coli was, at least, partly reversed by the histamine or carbachol treatment. Serosal histamine application produced no significant changes in the Isc in any tissues. Only the uninfected control tissues responded significantly to carbachol with an increase of Isc, while the response to carbachol was blunted to non-significant values in infected tissues. Together, these data may explain why chickens rarely respond to intestinal infections with overt secretory diarrhea. Instead, the immediate response to intestinal E. coli infections appears to be a tightening of the epithelial barrier.PLoS ONE 01/2014; 9(3):e92156. · 3.53 Impact Factor
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ABSTRACT: This study was undertaken to observe the prevalence, serogroup, avian pathogenic Escherichia coli (APEC)-associated virulence gene, randomly amplified polymorphic DNA (RAPD) pattern, and antibiotic resistance genes of E. coli in backyard layers and their environment in India. From the 360 samples of healthy layers and their environment, 272 (75.5%) E. coli were isolated. The majority (28.67%) of them were untypeable. Among the studied virulence genes (papC, tsh, iucC, astA), 52 (14.32%) isolates were found to possess astA, including the isolates from the drinking water of the birds (4/272, 1.47%). These strains belonged to 18 different serogroups. Most of the isolates were typeable by RAPD and they produced different patterns. Phenotypic resistance of the isolates was most frequently observed to erythromycin (95.83%), chloramphenicol (87.52%), and cotrimoxazole (78.26%). None of the isolates was found to possess extended-spectrum beta-lactamases (bla(TEM), bla(SHV), bla(CTX-M) or quinolone resistance (qnrA) genes by PCR. The present study was the first attempt in India to assess APEC distribution in backyard poultry production.Avian Diseases 03/2014; 58(1):39-45. · 1.73 Impact Factor
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ABSTRACT: Avian pathogenic Escherichia coli (APEC) is one of the most economically devastating pathogens affecting the poultry industry. This group of extra-intestinal E. coli causes a variety of clinical conditions including airsacculitis and cellulitis. The economic impact of APEC is mainly due to mortality, slower growth rates, and carcass downgrading. In commercial broiler operations, APEC infections are controlled indirectly by vaccination against other respiratory diseases and minimizing stress conditions, and directly by administration of antimicrobial agents to suppress the infection in already infected flocks. The fact that most APEC strains possess some common virulence factors suggests that an effective vaccine against APEC is a viable option. The most important virulence factors that have been investigated over the years include type I and P fimbriae, aerobactin iron-acquisition system, and serum resistance traits. Despite the potential for developing an efficacious vaccine to combat this economically important poultry disease, several obstacles hinder such efforts. Those obstacles include the cost, vaccine delivery method and timing of vaccination as the birds should be immune to APEC by 21 days of age. Herein, we review the various attempts to develop an effective vaccine against the respiratory form of APEC diseases in poultry. We also discuss in-depth the potentials and limitations of such vaccines.Veterinary microbiology. 05/2014;