Abstract: Objective: In this study, the serotyping, antibiotic susceptibility and some genes associated with quinolone and fluoroquinolones resistance of 432 chicken-borne Salmonella isolates in and around Yangling, Shaanxi province were studied for better understanding the epidemiological characteristics of Salmonella serovars. Methods: Salmonella serovars were determined using slide agglutination method. Antibiotic susceptibility was tested by the agar dilution method recommended by the Clinical and Laboratory Standards Institute (CLSI). The resistant genes of qnrA, qnrB, qnrS and aac(6’) -Ib-cr, commonly carried by plasmid and associated with resistance to quinolone and fluoroquinolones, were identified using PCR and DNA sequencing. Results: Totally 37 serotypes were identified among 396 Salmonella isolates, and the other 36 isolates were unidentified. The most prevalent serotype was Salmonella typhimurium (17.93%), followed by S. thompson (12.88%), S. essen (8.84%) and S. infantis (6.57%). Among 432 Salmonellae isolates, antibiotic resistance was commonly found to sulfafurazole (89.81%), and approximately 50% of the isolates were resistant to sulfamethoxazole, naladixic acid, tetracycline, ampicillin, chloramphenicol, and amoxicillin/clavulanate potassium. aac(6’)-Ib-cr (16.67%) was most frequently detected, and the detection rates of qnrB, qnrS and qnrA were 10.19%, 6.71% and 1.62%, respectively. The distribution of these four genes differed in different serotypes of isolates. More qnr and aac(6’)-Ib-cr genes were detected in the isolates found to be more resistant to both fluoroquinolones and aminoglycosides. Conclusion: The serotype of Salmonella isolates from retail chicken in Yangling and its surrounding areas was diverse, and qnr and aac(6’)-Ib-cr genes were commonly found in these isolates that were resistant to many antibiotics.

Key words: Salmonella, serotype, fluoroquinolones, antibiotic resistant genes