Jpn.J.Infect.Dis., 52, 1999
Laboratory and Epidemiology Communications
Outbreak of Salmonellosis Caused by Ingestion of Cuttlefish Chips Contaminated by both Salmonella Chester and Salmonella Oranienburg
Division of Microbiology, Hyogo Prefectural Institute of
Public Health,
Arata-Cho 2-1-29, Hyogo-Ku, Kobe 652-0032, Japan
Communicated by Shunsuke Imai
(Accepted July 30, 1999)
A cuttlefish chips-related salmonellosis spread throughout Japan from December 1998 to May 1999 . The epidemiological data are summarized in Fig. 1. We were the first in identifying Salmonella Oranienburg as a causative agent responsible for the outbreak (1,2). During the same period, we isolated S. Chester as well.
From the diarrheal stools of 13 children aged 4-12 years in Himeji City and in two nearby towns, we isolated 16 examples of Salmonellae, 6 of which were S. Oranienburg and 10 S. Chester. The stool specimens of three children contained both organisms. Two children who discharged Salmonella (one S. Chester alone and the other S. Chester and S. Oranienburg) had a history of eating cuttlefish chips. We tried to isolate S. Chester from "Oyatsu-Chinmi", a cuttlefish chip snack, from which S. Oranienburg had already been detected. S. Chester was isolated from five out of six such specimens.
The S. Chester isolates were examined by pulsed-field gel electrophoresis (PFGE) using a Gene Path Typing System (Nippon Bio-Rad, Tokyo). PFGE of BlnI-digested chromosomal DNAs showed an identical pattern for the patient-derived and the "Oyatsu-Chinmi"-derived isolates (Fig. 2). It appeared that the snack was contaminated with the two Salmonella serotypes, both of which were responsible for this outbreak of food poisoning.
Most laboratories failed to isolate S. Chester from the related outbreaks. One of the reasons we were able to successfully isolate the organism was due to our use of a special protocol for isolating S. Chester. S. Chester (04: e,h;e,n,x) can be separated from S. Oranienburg (07:m,t;-) by immobilizing the latter by an antibody which specifically recognizes the G flagellar antigen present in S. Oranienburg but not in S.. Chester. Therefore, after enriching the Salmonella by culturing it in Mannitol Selenite Medium (Oxoid Ltd., Hampshire, England), we inoculated 50 ul aliquots to Craigie tubes containing the semi-solid SIM medium ( Nissui Pharmaceutical Co. Ltd., Tokyo) with anti-H-G antiserum (DENKA SEIKEN Co. Ltd., Tokyo). On one hand, S. Chester swam to the upper part of the culture while replicating. On the other hand, S.. Oranienburg was immobilized where it was inoculated. Thus we could separate S. Chester from S. Oranienburg. It should be noted that all the S. Chester isolates show negative for lysine decarboxylase. As this marker usually shows positive for Salmonella species, there is a chance of diagnosing the S. Chester strains as non-Salmonella .
REFERENCES
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