Abstract
A total of 54 broiler flocks during the first two weeks of life was used to investigate the incidence of avian pathogenic E. coli in Egypt; 28 isolates (51.85%) were revealed by colony morphology and biochemical identification which then investigated for their serogroups and only 18/28 isolates were serotyped. The most prevalent serotypes were O115, O142, O158, O55, O125, O114, O27, O20, and O15. By application of polymerase chain reaction (PCR), 83.3% (15/18) of the serotyped isolates were confirmed to be E. coli, and 93.3% (14/15), 46.6% (7/15), and 20% (3/15) of isolates harbored the iss, iutA, and fimH genes, respectively. Virulence testing of the selected 13 APEC isolates on the specific-pathogen-free (SPF) chicks revealed them to be highly virulent (15.4%), moderately virulent (23.1%), and avirulent (61.5%); however, all isolates (100%) were extremely virulent towards SPF embryonated chicken eggs. Antibiotic resistance (100% of isolates (n = 13)) was observed for ampicillin, amoxycillin–clavulanic acid, and tetracyclines, colistin (92.31%; 12/13), doxycycline and spiramycin (84.62%; 11/13), florfenicol (69.23%; 9/13), cefotaxime (61.54%; 8/13), and ciprofloxacin (53.85%; 7/13). The highest percentage of sensitivity (53.85% of isolates; 7/13) was recorded for ofloxacin and enrofloxacin followed by gentamycin (46.15%; 6/13). The results suggest that the diagnosis of APEC with PCR is rapid and more accurate than traditional methods for E. coli identification; moreover, the presence or absence of iss, iutA, and/or fimH genes is not an indicator of in vivo pathogenicity of APEC. Thus, further studies, including a wider range of virulence genes and gene sequencing, are required. In addition, serotyping has no effect on the virulence of APEC.
Highlights
Escherichia coli (E. coli) is a Gram-negative bacterium of the family Enterobacteriaceae [1]
This study aims to investigate the prevalence of avian pathogenic E. coli (APEC) in baby chicks using traditional laboratory methods, followed by confirmatory molecular techniques, and assess their virulence in specific pathogen-free (SPF) 1-day-old chicks and embryonated chicken eggs (ECEs) and the correlation of in vivo virulence with studied virulence genes or serotypes
The cultural morphology on MacConkey and Eosin Methylene Blue (EMB) agars and biochemical identification revealed that 51.85% (28/54) of the examined broiler chick flocks were positive to E. coli
Summary
Escherichia coli (E. coli) is a Gram-negative bacterium of the family Enterobacteriaceae [1] It is a commensal microorganism found in the intestine of humans and animals; it may induce illness so they are classified to commensal and pathogenic E. coli with further classification of pathogenic group to two pathotypes, diarrheagenic E. coli (DEC) and extraintestinal pathogenic E. coli (ExPEC), that cause various diseases in both humans and animals [2]. Pathogens 2020, 9, 114 is one of the major bacterial diseases in the poultry industry that has gained immense attention worldwide [3]. It is responsible for various disorders, including colisepticemia, air sacculitis, peritonitis, perihepatitis, pericarditis, omphalitis, coligranuloma, enteritis, synovitis, swollen head syndrome, and osteomyelitis [4], which eventually lead to total or partial condemnation of carcasses and expensive antibiotic treatment [3].
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