[Study on an outbreak of food poisoning caused by Salmonella blegdam]

To identify the bacterial pathogen in food and the source of infection that might be responsible for a food poisoning outbreak.

All the probable cases that had attended the banquet in a village of Sichuan province who had developed fever (≥ 37.5°C), diarrhea (≥ 3 times/day) and vomiting since August 1, 2009, were identified. A case-control study was conducted to identify the foods that might be responsible for this food poisoning event. 50 cases were randomly selected from the probable cases and 50 controls were randomly selected from those without the symptoms.

The attack rate of this food poisoning event was 43.4% (132/304). 86.0% (43/50) of the cases and 34.0% (17/50) of the controls had eaten pork-mixed-vermicelli(OR = 12.0, 95%CI: 4.4 - 32). Data from further tests showed that dose-effect relation existing between eating pork mixing vermicelli behavior and the incidence rates(Chi-square trend: χ(2) = 21.06, P = 0.00) of the disease. 94.0% (47/50) of the cases and 68.0% (34/50) of the controls had eaten mushroom braising chicken (OR = 7.4, 95%CI: 2.0 - 27). Data from the crossover analysis showed that there appeared an effect modification between behaviors of eating pork-mixed-vermicelli and eating mushroom braising chicken. Three cases were detected carrying Salmonella blegdam from their anus swabs and the same bacteria type was also detected in the pork-mixed-vermicelli.

This outbreak of salmonellosis was caused by Salmonella blegdam contaminated pork-mixed-vermicelli or mushroom braising chicken during food processing.