Phenotypic and genotypic characterization of avian pathogenic E. coli in airsacculitis of broiler chickens

Abstract

Respiratory tract affections in poultry have significant economic importance worldwide. The current work focused on airsacculitis syndrome and phenotypic and genotypic characterization of E. coli associated with airsacculitis in broiler chickens. A total of 105 airsacculitis samples were collected aseptically from both diseased and freshly dead broiler chickens at different farms in El-Fayoum, Beni-Suef and El-Menia Governorates. The prevalence of airsacculitis in the examined broiler chickens was 43.9%. Bacteriological examination of the samples collected showed that a total of 94 E. coli isolates were recovered with a prevalence of 89.5%. All E. coli isolates were serogrouped into 10 O-serogroups ordered as follows, O₉₁ (19.1%), O2 (16%), O127 (13.8%), both O18 & O26 (9.6%, for each), both O8& O153 (7.4% for each), O78 (6.4%), and finally both O1& O44 (5.3% for each). The results of in-vitro antimicrobial susceptibility tests revealed that E. coli isolates mostly showed high resistances against β-lactams, gentamicin and sulfa antimicrobials meanwhile showed high sensitivities against fluoroquinolones, phenicols and tetracyclins. All isolates have been subjected to both combined disc diffusion (CDD) and cefinase tests for phenotypic detection of ESβLs production, which was confirmed in 50% and 61.7% of isolates, respectively. Haemolytic activity and biofilm formation were phenotypically detected in all E. coli isolates. PCR was conducted on 11 MDR isolates for determination of 5 resistance genes, ampC, bla_CTX and bla_TEM, aadB and sul1. The results revealed that all the tested E. coli isolates had ampC, bla_CTX and bla_TEM, while 90.1% and 27.3% of tested isolates had sul1 and aadB genes, respectively. Also, PCR was conducted to detect 5 virulence genes, iss, iutA, papC, fimH and hlyA. The results revealed that iutA and fimH genes were found in all the tested isolates, while iss, papC and hlyA genes were represented as follows, 90.1, 63.6 and 54.5%, respectively. It was concluded that E. coli is the most common bacterial isolates of airsacculitis that phenotypically has high antimicrobial resistance patterns, ESβLs production, haemolytic activity and biofilm production. All these phenotypic characters are supported by detection of their encoding genes. Such highly virulent and antimicrobial resistant strains are major health concerns as they could be transmitted to human.