Introduction: Extraintestinal E. coli (ExPEC) are epidemiologically and phylogenetically distinct from intestinal pathogenic E. coli strains and can pose serious risks to human health. The ExPEC causes between 6-8 million cases of infections costing about US$ 2 billion annually. Little is known about the prevalence of ExPEC and their complement of virulence genes isolated from retail poultry.
Purpose: The objective of this study was to investigate the prevalence of ExPEC-related genes in E. coli isolated from retail poultry meats purchased in Alberta.
Methods: Multiplex PCRs were used to detect 51 virulence genes in about 700 E. coli isolated from retail poultry meats. The ExPEC pathotype defined by the detection of two or more of the following virulence genes: papA and papC, sfa, kpsMT II, or iutA were then compared to 12 E. coli isolates recovered from clinical cases of human infection (stool, blood and urinary tract infections). Phylogenetic grouping and genetic relationships between isolates were determined by PCR and pulse field gel electrophoresis (PFGE).
Results: Fifty nine (8.4%) of the 700 E. coli isolates from poultry meat were identified as ExPEC, and were equally distributed among the phylogenetic groups A, B1, B2 and D. Human ExPEC isolates were from phylogenetic group A, B2 and D. Poultry isolates of phylogenetic group A possessed up to 12 virulence genes compared to 24 and 18 genes in phylogenetic groups B2 and D, respectively. Poultry meat E. coli identified as ExPEC harbored as many virulence genes as those from human isolates. In addition to the iutA gene which was found in 98% of chicken isolates, siderophore-related ironEC (61% of chicken isolates) and fyuA (yersinabactin: 100% human isolates) were detected in combination with other virulence genes including those encoding adhesin, protectin and toxin genes. The papG allele I’, papG allele 1, and clpG were not found in any of the E. coli isolates, while fimH, ompT, traT, uidA, and vat, were commonly detected. More than 66% of human ExPEC carried papG allele II, papG allele 2&3, and iha genes and about 15% poultry ExPEC harboured these genes. The hemF, iss, and cvaC genes were not found in human ExPECs but about 40% of poultry ExPECs carried these genes. All human ExPEC harboured concnf and hlyD which were not found in poultry ExPEC. The PFGE showed poultry ExPECs clustered with human ExPEC suggesting a genetic relationship.
Significance: Comparing ExPECs isolated from retail poultry meats with those from humans provided insights into their virulence potential that may pose serious meat safety risks. Further investigations on the ability of our poultry ExPEC to cause diseases are warranted.