[Two Outbreaks of Yersinia enterocolitica O:8 Infections in Tokyo and the Characterization of Isolates].

Although the number of outbreaks caused by Yersinia enterocolitica has been very small in Japan, 4 outbreaks were occurred during the 2 years between 2012 and 2013. We describe herein 2 outbreaks which were examined in Tokyo in the present study. Outbreak 1: A total of 39 people (37 high school students and 2 staff) stayed at a hotel in mountain area in Japan had experienced abdominal pain, diarrhea and fever in August, 2012. The Y. enterocolitica serogroup O:8 was isolated from 18 (64.3%) out of 28 fecal specimens of 28 patients. The infection roots could not be revealed because Y. enterocolitica was not detected from any meals at the hotel or its environment. Outbreak 2: A total of 52 students at a dormitory had diarrhea and fever in April, 2013. The results of the bacteriological and virological examinations of fecal specimens of patients showed that the Y. enterocolitica serogroup O:8 was isolated from 24 fecal specimens of 21 patients and 3 kitchen staff. We performed bacteriological and virological examination of the stored and preserved foods at the kitchen of the dormitory to reveal the suspect food. For the detection of Y. enterocolitica, food samples. together with phosphate buffered saline (PBS) were incubated at 4 degrees C for 21 days. Then, a screening test for Y. enterocolitica using realtime-PCR targeting the ail gene was performed against the PBS culture. One sample (fresh vegetable salad) tested was positive on realtime-PCR. No Y. enterocolitica was isolated on CIN agar from the PBS culture because many bacteria colonies other than Y. enterocolitica appeared on the CIN agar. After the alkaline-treatments of the culture broth or the immunomagnetic beads concentration method using anti-Y. enterocolitica O:8 antibodies, Y. enterocolitica O:8 which was the same serogroup as the patients' isolates was successfully isolated from the PBS culture. The fresh vegetable salad was confirmed as the incrimination food of this outbreak.