Antibiotic Resistance Patterns andmcr-1Detection in Avian PathogenicEscherichia coliIsolates from Commercial Layer and Layer Breeder Flocks Demonstrating Colibacillosis in Greece

Objectives:The aim of this study was to investigate the antimicrobial resistance (AMR) patterns ofEscherichia colistrains isolated from poultry flocks suffering from colibacillosis in Greece and to detect the presence of themcr-1gene in isolates being phenotypically resistant to colistin. Results:A total of 150E. colistrains were isolated from commercial layers and layer breeder flocks in Greece and tested for antimicrobial susceptibility. A high level of susceptibility was revealed for cephalosporins, neomycin, and colistin. Susceptibility varied for other antimicrobials (tetracycline, doxycycline, lincospectin, trimethoprim/sulfamethoxazole, enrofloxacin, amoxicillin), whereas no susceptibility was reported for macrolides, tiamulin, lincomycin, oxacillin. Concerning colistin resistance, 20E. colistrains were found to be phenotypically resistant (13 strains showed intermediate resistance pattern and 7 strains fully resistance trait). Further investigation was performed by PCR, which has revealed the presence of themcr-1gene in one phenotypically colistin-resistant isolate. Conclusion:AMR is prevalent in layer poultry production, including resistance against colistin confirmed by the presence of themcr-1gene.

Automated summary

The study revealed high levels of antimicrobial resistance in Escherichia coli isolated from poultry flocks in Greece, including resistance to colistin. PCR analysis detected the presence of the mcr-1 gene in one colistin-resistant isolate, confirming the resistance pattern observed.