BIOCHEMICAL, CLINICAL AND MOLECULAR CHARACTERIZATION OF AVIAN PATHOGENIC Escherichia coli (APEC) IN COMMERCIAL BROILER FLOCKS IN THE PHILIPPINES USING THE PLASMID PATHOGENICITYASSOCIATED ISLAND PREDICTORS

Abstract

Avian pathogenic Escherichia coli (APEC) poses a significant dual threat to the economic viability and health of the broiler industry. A thorough analysis of 18 commercial broiler flocks across diverse regions in the Philippines was aimed at confirming the presence of APEC, utilizing the plasmid pathogenicity-associated island predictors. The affected flocks, aged one to five days, exhibited various clinical signs, including lethargy, increased mortality, omphalitis, pericarditis, perihepatitis, enteritis, and delayed growth. All isolated APEC strains distinctly demonstrated typical staining and cultural characteristics as Gram-negative rods with gamma hemolysis. Biochemical profiles yielded positive results for catalase, indole, lactose, methyl-red (MR), nitrate reduction, saccharose, and glucose, as well as gas production; negative results were observed for citrate, hydrogen sulfide (H2S), oxidase, urease, and Vogues-Proskauer (VP). Among the 18 farms analyzed, 50% tested positive for all APEC virulence genes—iroN (83%), iss (94%), ompT (94%), iutA (61%), and hlyF (89%). This virulence gene profile, revealed through PCR analysis using the plasmid pathogenicity-associated island predictors, highlights the role of these genes, encoding protectins, iron acquisition systems, and toxins. The findings have enhanced the understanding of Philippine APEC strains, emphasizing their biochemical and genetic profiles. The current data are crucial for developing diagnostic kits and formulating effective preventive and control protocols against APEC in the country.