An outbreak of foodborne infection caused by Shigella sonnei in West Bengal, India

Abstract

A foodborne acute gastroenteritis outbreak due to Shigella sonnei infection occurred in a household after eating foods in a housewarming party at Pakapol Village, South 24 Parganas District of West Bengal, an Indian state, in November 2016. Here, we report the epidemiological and microbiological findings of this outbreak. Thirty-four people attended the party on November 23, 2016, and had lunch together. The median incubation period from the time of food consumption to the development of acute gastroenteritis was 18.5 h (interquartile range, 16.5–22 h). The overall attack rate was 73% (25/34), and 76% (19/25) of them required hospitalization. All age groups were affected with 100% recovery rate. One served food item was significantly associated with the illness, i.e., tomato salad (risk ratio, 4.14; 95% confidence interval, 1.21–14.13). Among the 12 stool specimens tested, 8 (67%; 8/12) were positive for S. sonnei. All S. sonnei strains were completely resistant to nalidixic acid, norfloxacin, ciprofloxacin, ofloxacin, and erythromycin, and partially resistant to tetracycline, doxycycline, streptomycin, and trimethoprim/sulfamethoxazole. Pulsed-field gel electrophoresis analysis showed that the recent outbreak strains of S. sonnei were clonally related with the locally circulating strains in Kolkata.