Prevalence, molecular characterization, and antimicrobial resistance among , spp., and strains isolated from Egyptian broiler chicken flocks with omphalitis.

Background: Bacterial Omphalitis has been reported as a significant cause of mortalities in newly hatched broiler chicks.

Aim: This study aimed to assess the occurrence of omphalitis among broiler chickens in Gharbia governorate in Egypt. In addition, the bacteria associated with the occurrence of omphalitis in broiler chickens were also investigated and characterized.

Methods: For this purpose, 43 farms in that area were surveyed. The comparative levels of omphalitis caused by (), spp., and () were screened in 129 chicks. The drug resistance to eight commonly used antimicrobials in Egyptian poultry farms was screened using the disk diffusion method.

Results: The overall incidence rate of omphalitis was 37.21%. In birds with omphalitis, the co-prevalence of , spp., and was 87.5%. When compared to healthy flocks, broiler chicks with omphalitis caused by spp., , and had a greater mortality rate in the first week of life. However, there were no significant differences in the mortality cases caused by these pathogens. Eighty-seven percent of the cases of omphalitis were linked to and 75% to spp. and From the yolk sac of broiler chicks with omphalitis, , spp., and were isolated at rates of 87.5%, 62.5%, and 45.8%, respectively. The isolates of and spp. exhibited great sensitivity to gentamycin and Tetracycline; however, the strongest drug resistance was observed toward cefpodoxime, sulphamethoxazole and trimethoprim, ampicillin, and amoxycillin and clavulanic acid. The recovered isolates of showed susceptibility to chloramphenicol (72.37%), oxytetracycline (81.82%), and erythromycin (81.82%). However, every isolate that was found resistant to amoxycillin and clavulanic acid, penicillin G and oxacillin. of blaTEM, blaSHV, and blaCTX-M genes has been proposed as the genetic cause of β-lactam antibiotic resistance in spp. and MecA and blaZ; however, were found in every strain of .

Conclusion: The frequency of omphalitis and its associated mortalities was comparatively high in Gharbia governorate. More efforts should be made to adopt strict hygienic standards for controlling and preventing such disease and this will consequently lead to minimizing the use of antimicrobials in poultry farms.