Evaluation of Escherichia coli drug resistance of relict gull (Larus relictus) in Hongjian Nur, Shaanxi, China

Antibiotic resistance (AMR) is one of today’s most pressing global public health crises, which effective containment of its potential negative effects requires regular monitoring of bacterial resistance. Wild birds are recognized as reservoirs and potential transmitters of antibiotic resistance, thus playing a critical role in the dissemination of resistant bacteria. Therefore, we evaluated the resistance phenotypes and resistance genes of E. coli in the intestinal tract of relict gulls in the Hongjian Nur area of Shaanxi Province. In this study, fecal samples from relict gulls were collected for E. coli isolation and identification, drug susceptibility testing, drug resistance gene detection, phylogenetic clustering, and multi-locus sequence typing. A total of 172 E. coli strains were isolated. The results of the drug susceptibility tests indicated phenotypic resistance rates of 37.21% for azithromycin, 12.21% for ampicillin, and 9.88% for tetracycline, with 19.95% of the strains exhibiting multiple drug resistance. PCR amplification results showed that the carrying rates of the first five resistance genes were all above 90%, with resistance rates for tem and strA both at 99.42%. The phylogenetic clustering of multi-drug resistant E. coli predominantly belonged to the B2 group. Sequence typing revealed that several E. coli alleles were primarily ST4162, ST1299, ST1196, ST297, and ST2570. Our findings indicate a serious level of drug resistance among E. coli from relict gulls, characterized by a high proportion of multiple drug resistance and a relatively high detection rate of various antibiotic resistance genes. By further investigating the distribution of drug-resistant bacteria in relict gulls, this study provides foundational data for understanding the resistance phenotypes and distribution of drug-resistant genes in migratory birds, thereby contributing to efforts aimed at alleviating the increasingly severe global antibiotic resistance issue.