Abstract: [Objective] To monitor the antibiotic resistance profiles and the epidemiological distribution of virulence genes in Escherichia coli isolates from selected meat duck farms in Shandong Province. [Methods] A total of 240 cloacal swab samples were collected from four large-scale duck farms in Shandong Province. E. coli was isolated and identified using differential culture media and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry （MALDI-TOF MS）. The susceptibility of E. coli isolates to 11 antibacterial agents was determined using the broth dilution method. Polymerase chain reaction （PCR） was employed to detect the presence of resistance genes and virulence genes in the isolates. [Results] A total of 212 E. coli strains were isolated, with an isolation rate of 88.33% （212/240）. All isolates exhibited resistance to doxycycline and were sensitive to meropenem. High resistance rates were observed against ampicillin （99.05%） and amoxicillin/clavulanic acid （97.64%）. The multidrug resistance （MDR） rate among the isolates was 93.40%. Resistance spectrum analysis revealed that 63 strains were resistant to 9 antibacterial agents, 51 strains to 8 agents, and 47 strains to 10 agents. Among the 21 resistance genes tested, the detection rates of aadA2, strA, strB, bla_TEM, qnrS, mcr-1, and tetA ranged from 52.83% to 94.34%, while qnrD, tetG, and aadA were not detected, with strains co-carrying eight resistance genes being the most prevalent （60 strains）. Among the 18 virulence genes analyzed, yijp, ibeB, OmpA, mat, iucD, fimC, and vat showed detection rates ranging from 54.25% to 98.58%, with strains co-carrying seven virulence genes being the most common （71 strains）. The predominant virulence gene pattern was ibeB-yijp-mat-OmpA-fimC-iucD （14.62%）. [Conclusion] E. coli isolates from meat ducks in certain farms in Shandong Province exhibited severe antibiotic resistance, with a prevailing pattern of co-carrying seven virulence genes. These findings suggest that the isolated duck-derived E. coli may possess significant pathogenic potential, highlighting the need for enhanced monitoring of antibiotic resistance in duck-derived E. coli in this region.

Key words: meat duck, Escherichia coli, antibiotic resistance, resistance genes, virulence genes