Performance of Salmonella surveillance in Baoshan district, Shanghai

Objective To evaluate the performance of laboratory based foodborne Salmonella surveillance and diarrhea cases in Baoshan district, Shanghai. Methods Two hospitals, selected farm produce markets/supermarkets and natural water were used to carry out continuous active surveillance and environment background surveillance from 2010 to 2014. The annual Salmonella infection epidemiologic curve and type characteristics were analyzed. Results From 2010 to 2014, Salmonella positive rates in foodborne infection cases and foodborne environment samples were 6.9% (269/3898) and 5.3% (99/1885) respectively. The Salmonella positive rate in group 21-60 years (6.2%, 168/2714) was significant lower than in age group 12 years (40.6%, 39/96). The male to female ratio of the confirmed infection cases was 1.3:1. In food samples, 26.2% of pork specimens were Salmonella positive, followed by chicken meat (7.8%, 9/116) and duck meat (14.3%, 4/28). The predominate human sourced serotypes were S. Typhimurium, S. Enteritidis, S. Infantis, S.Thompson and S. Sanftenberg, which were less diverse than those from food products. Antibiotic resistance characteristics of human sourced isolates were stable, which had less resistance to ciprofloxacin and cephalosporin. The foodborne Salmonella isolates were relatively more resistant to common antibiotics than human sourced isolates, but it showed downtrend in recent years. The surveillance data during 2010-2011 reflected the epidemiologic pattern of Salmonella infection more accurately than data from other years. Conclusion Most Salmonella infection cases were young adults in Baoshan. The animal products were highly contaminated with Salmonella. The epidemiologic curves of Salmonella infection were reliable, but bias existed. The quality control and evaluation should be strengthened in surveillance. More investment should be given to local health facilities to conduct active foodborne infection surveillance, and the capability for outbreak response and pathogen molecular subtyping should be strengthened by using national laboratory network platform.