Analysis on molecular typing of Salmonella thompson isolates and its drug resistance in Salmonella surveillance

ObjectiveTo conduct molecular epidemiological analysis with molecular typing and drug susceptibility test to 50 strains of Salmonella thompson isolated in Chongqing and Shanghai. MethodsThe drug susceptibility test to 14 antibiotics was performed by mini broth dilution method. Molecular typing methods include pulsed field gel electrophoresis (PFGE) and multi-locus variable-number tandem repeat (VNTR) analysis (MLVA). ResultsThe results of drug susceptibility test indicated that 78% of the isolates were multi- drug resistant. The most resistant antibiotics were sulfamethazole and tetracycline, followed by trimethoprim. All isolates were sensitive to cephalosporins (cefotaxime, ceftriaxone, ceftazidime and ceftiofur). 15 PFGE patterns were identified in 50 isolates and 30 isolates from Chongqing were highly homologous. MLVA analysis shows that there were no variations at tested loci except for Sal16 loci. ConclusionThe molecular typing analysis supported ISalmonella thompson/I had caused outbreaks and sporadic cases. MLVA is less effective in subtyping ISalmonella thompson/I than PFGE, which needs to be improved.