Abstract:

In order to investigate the relationship between drug-resistant phenotypes and genes and explore the mechanism
of drug resistance at the gene level, a total of 215 Salmonella strains isolated from 1 093 retail meat samples were assayed
for antimicrobial susceptibility. Totally 16 pairs of primers were designed to amplify the drug-resistant genes and sequence
homology was detected after T-A cloning. Results indicated that the Salmonella isolates showed the highest resistance
to sulfisoxazole (SIZ) (71.7%), followed by tetracycline (TET) (69.8%), trimethoprim (TMP) (67.9%) and compound
sulfamethoxazole (TSU) (52.8%), and all these isolates were sensitive to ciprofloxacin (CIP), nitrofurantoin (NIT) and
cephalosporin. Approximately 60.5% of these isolates showed resistance to at least 3 kinds of antibiotics, and 4 of them were
even resistant to 13 drugs. Ten drug-resistant genes were detected and they were found to share a homology higher than 99%
with reference sequences. The consistency rates between drug-resistant phenotype and drug-resistant gene for β-lactams and
tetracycline were both higher than 90%, followed by sulfonamides (81.6%). This study demonstrated that the drug resistance
rate of foodborne Salmonella was high and their multi-drug resistance was serious. And the results of detection of drugresistant
phenotypes and drug-resistant genes were consistent.

Key words: food safety, Salmonella, antibiotics, antimicrobial resistance phenotype/resistance genes