Sequence Analysis, Antibiogram Profile, Virulence and Antibiotic Resistance Genes of XDR and MDR Isolated from Layer Chickens in Egypt.

Background: is incriminated frequently in severe economic losses and mortalities in the poultry industry. This study aimed to detect the prevalence of in layer chickens, sequence analysis, the antibiogram profiles, and PCR screening of virulence determinants and antibiotic resistance genes.

Methods: Accordingly, 300 samples (tracheal swabs, ovary and oviduct, and lung) were randomly collected from 100 diseased layer chickens from private commercial layer farms at Elsharkia Governorate, Egypt. The bacteriological examination was carried out. The retrieved isolates were tested for gene sequencing, antibiogram profiling, PCR screening of virulence (A, A, and B), and antibiotic resistance genes ( , A1, B, and H).

Results: The prevalence of was 25% in the examined diseased layer chickens. The sequence analyses emphasized that the tested strains derived from a common ancestor and exhibited a notable genetic similarity with other strains from USA, China, and Denmark. The isolated strains were highly resistant to sulfamethoxazole-trimethoprim, oxytetracycline, penicillin, ampicillin, kanamycin, neomycin, and erythromycin. The PCR revealed that the retrieved strains carried A, B, and A virulence genes with a prevalence of 100%, 100%, and 38.3%, respectively. Approximately 30.1% of the retrieved isolates were XDR to six antimicrobial classes and harbored , A1, and B resistance genes. Moreover, 20.5% of the isolated strains were MDR to three different classes and carried and H resistance genes.

Conclusion: Briefly, this study emphasized the existence of XDR and MDR strains in poultry. Florfenicol and norfloxacin displayed a promising antimicrobial effect against the emerging XDR and MDR in poultry. The emergence of XDR and MDR is considered a public health alarm.