Abstract
Avian colibacillosis is one of the most important diseases of chickens resulting in significant economic losses as well as high morbidity and mortality. In the current study, the prevalence of avian colibacillosis was studied in different farms of broiler chickens in Beni-Suef, EL-Minia, ElFayoum, Assiut and Sohag Governorates. A total of 300 pooling samples were collected aseptically from heart blood as well as the affected organs including air sacs, pericardial sac, and liver of slaughtered diseased and freshly dead broiler chickens. Bacteriological examination of the collected samples showed that a total number of 80 E. coli isolates were recovered with an overall prevalence of 26.7. The highest prevalence was recorded in El-Fayoum (33.3%) followed by El-Minia (25%), Beni-Suef and Assiut (22.5% for each) while the lowest prevalence was in Sohag (17.5%). The invitro antimicrobial susceptibility testing revealed that E. coli isolates showed high sensitivity to colistin sulphate only (70%). Meanwhile, high resistances were recorded against other antimicrobials including amoxicillin (97.5%), cefotaxime sodium and florfenicol (95% for each), apramycin, ciprofloxacin and gentamicin (92.5% for each), streptomycin (90%), enrofloxacin (87.5%), trimethoprim-sulphamethoxazol and doxycycline HCl (77.5% for each). All E. coli isolates were MDR (100%). PCR was applied on 10 MDR E. coli isolates to detect the 3 resistance-associated genes (qnrA, tetA and aac(6′)- Ib-cr and 5 virulence-associated genes (iutA, hly, sta, lt and astA). The results showed that all the tested isolates (100%) harbored qnrA, tetA, iutA and astA genes meanwhile aac(6′)-Ib-cr, hly, sta and lt genes were not detected in any isolate.
Highlights
One of the major problems in the poultry farms is the control of infectious diseases causing high economic losses in the poultry industry (McKissick 2006)
E. coli strains were classified by Russo and Johnson (2000) into 3 major groups including intestinal pathogenic strains, commensal strains and, extra-intestinal pathogenic E. coli (ExPEC) strains
Molecular differentiation of E. coli strains and other bacteria may help in differentiation of those are pathogenic for a certain host, these techniques of molecular and genetic differentiation involve polymerase chain reaction (PCR) (Whittam and Wilson 1988)
Summary
One of the major problems in the poultry farms is the control of infectious diseases causing high economic losses in the poultry industry (McKissick 2006). Much lower prevalences were recorded by Amer et al (2018) who tested 20 E. coli isolates and detected the resistance tetA, and tetB genes as 40 and Regarding the obtained results of astA which was detected in all tested isolates (100%), they were supported by those of Kwon et al (2008) who studied by PCR 120 E. coli isolates from chickens and hatchery for detection of many genes to evaluate the epidemiological prevalence of APEC. The obtained results of enterotoxin encoding genes; including heat-stable enterotoxin (sta) and heat-labile enterotoxin (lt) which were not detected in any tested isolate, were the same of those obtained by Jeong et al (2012) who studied 101 APEC isolates from diseased chickens and characterized the virulence genes concerning enterotoxins including st and lt and recorded that all isolates were negative for all enterotoxin encoding genes.
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