Drug resistance characteristics and molecular typing of Salmonella Typhimurium in Xindu District, Chengdu, 2014-2019

Abstract

Objective To understand the drug resistance and molecular typing characteristics of 54 strains of Salmonella Typhimurium in Xindu District from 2014 to 2019. Methods The 54 strains of Salmonella Typhimurium isolated from case monitoring, food poisoning and food surveillance were tested for drug susceptibility using micro-broth dilution method, and pulsed field gel electrophoresis(PFGE) was used for molecular typing. Results The drug resistance rate of 54 strains of Salmonella Typhimurium was 98.15%(53/54), and that of multi-drug resistance(triple and above) was 46.30% (25/54). The multi-drug resistance rates of the case monitoring and food surveillance strains were 56. 00%(14/25) and 91.67%(11/12), respectively, which were much higher than the food poisoning strains 0.00%(0/17). The PFGE results could be divided into 31 pattern, with a similarity of 64.9%-100%. Among them, the dominant pattern was XD005, which contains 7 strains isolated from case monitoring and food surveillance. The results of drug resistance and molecular typing of strains from food poisoning were significantly different from those from case monitoring and food surveillance(P<0.05). Conclusion The drug resistance of Salmonella Typhimurium isolated from case monitoring and food surveillance was serious in Xindu District. PFGE can identify potential outbreak events in sporadic cases, so it is necessary to trace the molecular origin of the isolated strains on time.

Keywords

• salmonella typhimurium
• multi-drug resistance
• pulsed field gel electrophoresis