Characterizing avian pathogenic Escherichia coli from diagnostic cases in Georgia, USA – comparison of gene profiles with tissue of isolation

Abstract

Colibacillosis caused by Avian Pathogenic Escherichia coli (APEC) is a significant cause of morbidity, mortality and carcass condemnation to the poultry industry worldwide resulting in significant economic losses. We assessed a multiplex PCR for classifying diagnostic APEC and characterized these isolates using gene profile analysis.48 E. coli isolates collected between August and October 2018 through the Poultry Disease Research Center (PDRC) Diagnostic Laboratory were analyzed. Isolates were screened using multiplex PCR targeting genes associated with APEC chromosomal and plasmid virulence. Isolates were assessed for relationship between gene profile and host tissue of origin. Overall, isolates met the criteria for definition as well-developed pathogens with more than 90 % of isolates positive for the genes iroN, ompTp and hlyF; 78 % were positive for aerJ and 67 % for iss. A significantly lower prevalence was observed for cvaC, etsB, ireA and papC (range 5–36 %). When overall gene prevalence was examined for tissue of isolation, we found that APEC from the ovary, bone marrow, pericardium and lung had higher average numbers of genes compared to isolates recovered from skin and yolk sac. Genes associated with the ColV virulence plasmid (iss, iroN, hlyF and ompTp) were detected in 43 of 48 isolates (89.5%) further confirming the ColV plasmid is the defining trait of the APEC subpathotype. The use of a multiplex panel to screen for APEC has shown good correlation with pathogenesis, and tissue source and correlates well with invasive strains. Path panel diagnostics is available through PDRC, providing significant value to APEC screening.