Molecular typing and drug resistance of Salmonella in diarrhea cases in Qingdao, Shandong, 2014–2018

ObjectiveTo understand the molecular types and drug resistance of Salmonella isolated from diarrhea cases in Qingdao during 2014–2018 and provide scientific basis for early warning, prevention, control and tracing of Salmonella infection and rational application of antibiotics.

MethodsA total of 52 Salmonella strains isolated from diarrhea cases in Qingdao from 2014 to 2018 were detected for drug resistance by microbroth dilution method. The molecular typing was carried out by pulsed-field gel electrophoresis (PFGE). The similarity between strains was analyzed by software BioNumeries 7.6.

ResultsThe 52 Salmonella strains were mainly S. typhimurium and S. enteritidis, which were divided into 31 PFGE types by Xba I enzyme. The results of PFGE analysis showed that there were multiple clustering phenomenon. The highest resistance rate was to ampicillin (73.08%), followed by that to naphthenic acid (57.69%). The multi-drug resistance rate was 44.23%.

ConclusionIn Qingdao, Salmonella showed a trend of causing sporadic infection and multi-drug resistance, and the overall drug resistance rate was high. It suggested that tracing and drug resistance surveillance for Salmonella should be strengthened to prevent large-scale outbreak.