Survey of Avian Pathogenic Escherichia coli (APEC) in the Asia-Pacific Region

Avian pathogenic Escherichia coli (APEC) is one of the leading pathogens economically affecting the poultry industry. It is commonly associated with the syndromic disease colibacillosis which can manifest itself in many different forms such as airsacculitis, cellulitis, pericarditis, perihepatitis and respiratory distress. Over the years, many virulence-associated genes (VAGs) have been discovered which contribute to this avian disease such as hlyF, iroN, iss, iutA, and ompT. Many of these VAGs are plasmid encoded and as a result, E. coli strains can acquire varying numbers and combinations. To gauge the prevalence of this poultry pathogen, we conducted a survey across the Asia-Pacific region over the span of two years to observe the APEC levels and profiles of selected VAGs. A total of 1,621 broiler gastrointestinal tracts were collected from 11 different countries: Australia, Bangladesh, Brazil, India, Japan, Malaysia, Myanmar, Philippines, Taiwan, Thailand, and Vietnam. Total E. coli was enumerated from the small intestine, and up to five colonies from each sample were isolated and cultured for down-stream characterization. A panel of 5 APEC VAGs (listed above) were used to distinguish APEC from non-APEC isolates, with any isolate possessing 2 or more of these VAGs considered to be APEC. Isolates were grouped by the number of VAGs possessed. In total, 9,625 E. coli isolates were isolated from all the samples, of which 4,012 (42%) were found to be APEC. APEC levels ranged from <1.0E+02 CFU/g to 1.8E+08 CFU/g. There was a wide range of counts in all countries, but Australia and Malaysia tended to have the lowest APEC level, while India and Taiwan had the highest. India and Taiwan also had the highest ratios of APEC to commensal E. coli, while Bangladesh and Australia had the lowest. In conclusion, we observed varying levels and distributions of APEC and the VAGs they carry across regions. Continued monitoring of the prevalence and severity of APEC worldwide, especially as producers continue to reduce antibiotic usage, will help assess the need for alternatives to antibiotics to combat this poultry pathogen.
 
Keywords: Avian Pathogenic Escherichia coli, colibacillosis, virulence-associated genes.

Abstract presented at the 3rd International Symposium on Alternatives to Antibiotics 2019.