Astudy on the epidemiological characteristics and molecular typing of Salmonella enterica serovar Enteritidis in Shanghai

Objective To study the molecular epidemiological characteristics of Salmonella enterica serovar Enteritidis (S.Enteritidis) strains in Shanghai from year 2006 to 2007.Methods A retrospective analysis from year 2002 to 2007 was performed to explore the source of food-borne S.Enteritidis strains and compare its antibiotic resistance with strains isolated from diarrheal patients.Data of S.Enteritidis strains of patient and food of Global Salm-Surv (GSS) from year 2006 to 2007 were tested, including phenotype confirmation, antibiotic resistance and pulsed-field gel electrophoresis (PFGE) analysis.Results S.Enteritidis was the topmost strain in diarrheal patients caused by non-typhi Salmonella in year 2006 to 2007, in Shanghai.80% strains of food-borne S.Enteritidis were obtained from poultry and their products.The antibiotic resistance of food isolates was higher than those from clinical isolates.The drug resistance spectrum of diarrhea patients isolates in year 2006 was different from that in year 2007.76 strains including 13 food-borne strains belonged to 21 PFGE pattern combinations, and their genetic similarity was higher than 80%.The major PFGE subtype was type 3 (34strains), type 1 (12 strains), type 2 (5 strains) and type 5 (5 strains), Every strain from food had been matched with PFGE subtype strains in diarrhea patients except subtype 2.The number of homology case of diarrhea patients and food caused by subtype 1/2 were 4 and 12 in year 2006 and 2007.Conclusion There is close relationship between diarrhea patients of S.Enteritidis and contaminated poultry (chicken) in Shanghai.The PFGE subtype 3 is the predominant epidemic strain.The PFGE subtype 1/2 isolated from goose liver in year 2007 may be a viriety of subtype 3, and may tend to replace the predominant strain.This study suggests that rapid control and forecast the potential outbreak cases of S.Enteritidis and trace the suspected source of contamination by combining the surveillance of clinical patients and food chain, including the real-time molecular typing in laboratory.