Salmonella serotyping and molecular subtyping analysis on diarrhea cases in Hongkou District of Shanghai, in 2010-2012 ZHANG Jing1,SHEN Jing1,TANG Yi-ling1,CHEN Zhen1,YAO Hong1,WANG / 上海预防医学

ABSTRACT

Objective ] To study the molecular characteristics and antibiotic resistance of Salmonella diarrhea cases in sentinel hospitals through active surveillance system conducted by public health laboratory. [ Methods] Two sentinel hospitals were chosen for collection of stool specimens from food-borne infectious diarrhea cases and for Salmonella separation and detection immediately following serotyping and antimicrobial susceptible test ( AST ) on those isolates .Moreover , pulsed field gel electrophoresis ( PFGE) was used for the genetic homology analysis . [ Results] A total of 2 579 diarrhea specimens were collected and analyzed from 2010 to 2012, with 185 Salmonella isolates, covering 23 different serotypes (annual positive rates were 9.1%, 6.8%, 5.1%, with an average 7.2%).Salmonella enterica serovar Enteritidis(S.Enteritidis) and Typhimurium(S.Typhimurium) were the most common serotypes, of which 68.9% cases were seen in those aged 21 to 60 and 21.4% cases in those over 60 years old. 27.7%-96.9%S.Enteritidis and 2.6%-63.2% S.Typhimurium(P all <0.05) proved resistant to Nalidixic acid, Sultisoxazole, Streptomycin, Sulfamethoxydiazine, Gentamicinand Tetracycline. PFGE analysis on 22 S.Enteritidis strains showed 11 different clusters , while 20 S.Typhimurium strians showed 6. [Conclusion] S.Enteritidis and S.Typhimurium are the most common Salmonella serotypes, and molecular typing indicates the existence of clustering and sporadic outbreaks caused by dominance clones . We should be alert to early warnings on potential outbreaks of multiple-drug-resistant ( MDR ) S.Enteritidis.Active surveillance system based on public health laboratory should play an important role in the control of food-borne infectious diseases .