Investigation of Outbreak caused by Shigella flexneri

Ki, Hyun Kyun; Kim, Sun Hee; Kee, Hye Young; Seo, Jin Jong; Kim, Eun Sun; Ha, Dong Ryong; Chung, Jae Keun; Kim, Seong Han; Le, Bok Kwon

Abstract

BACKGROUND: Most of the shigellosis outbreak in Korea was caused by Shigella sonnei since late 1990's. In contrast, outbreak by Shigella flexneri were rare since late 1990's. Currently, we experienced the shigellosis outbreak by S.flexneri and described the results of investigation.
METHODS
We recruited employees from company "A" who had a meal at least once at the company's cafeteria from Dec 23th, 2002 to Dec 26th, 2002. We surveyed the symptoms, food items, and history of travel of eligible persons and their family members. For the microbiological examination, we collected specimen from eligible persons and their family. Collected specimens were cultured for bacteriologic agents and viruses. Epidemiological relationship among the isolates were analyzed by pulsed field gel electrophoresis (PFGE).
RESULTS
Among the eligible persons, one hundred ten were symptomatic (110/258, 42,6%). Eighty- two were confirmed bacteriologically. Day of symptom onset showed a unipolar pattern. Diarrhea was the most common symptom among the symptomatic patients (110/110, 100%). The other symptoms included abdominal pain (81.8%), tenesmus (70.0%), headache (63.6%), nausea (61.8%), febrile sense (59.1%), and vomiting (24.5%). Lunch on 24th Dec was the most significant risk factor of the outbreak (RR=6.46, 3.56< or =95% CI< or =11.75). All isolates of the outbreak has the same pattern on PFGE analysis and the PFGE pattern was not similar compared with other S.flexneri isolates from Korea.
CONCLUSION
This is the largest and unique outbreak by S.flexneri since 2000 in Korea. The outbreak has the same origin according to the PFGE pattern and epidemic characteristics. Considering rarity of S.flexneri among shigellosis in Korea, surveillance for S.flexneri should be enhanced.