AN EXTENSIVE OUTBREAK OF STAPHYLOCOCCAL FOOD POISONING DUE TO LOW FAT MILK IN JAPAN: ESTIMATION OF ENTEROTOXIN A IN THE INCRIMINATED

MILK AND POWDERED SKIM MILKPresented by Group 9

(Konstantinos Giannoutsos, Fitri Anisa and Hang Xing)

Introduction Extensive outbreak of staphylococcal food poisoning in Japan (Kansai district), June-July 2000

13,420 estimated cases Dairy products factory in Hokkaido responsible

Outbreak occurred mostly in households

The amounts of SEA in leftover low-fat milk were estimated and then the total intake per capita to develop illness was calculated

Foods under Investigation Powdered skim milk was the main ingredient

Foods included: low-fat milk, calcium-enriched low-fat milk, yogurt drink, and other dairy products

Causative Agent Food poisoning due to Staphylococcal enterotoxin A (SEA)

However, viable Staphylococcus aureus was never isolated from tested samples

MethodsEpidemiological data General data report of investigation by a joint committee of the Ministry of Health, Labour and Welfare and the Osaka Municipal Government

Individual data obtained from the Osaka Prefectural Government Epidemiological data and samplesHealth centre collect leftover of low-fat milk laboratory test for staphylococci, SEs and Bacillus cereus seized low-fat milk and powdered skim milk for SEs testLaboratory report SET-RPLA kit (Denka Seiken Co. Ltd., Tokyo, Japan) for detection and semi-quantification of SEA-SED

Kit for SEE and purified SEs donated by Junich Sugiyama (Denka Seiken) U-type microtitre plates (Iwaki Glass Co. Ltd., Osaka, Japan) Mini-VIDAS automated system for the VIDAS Staph Enterotoxin Test (bioMérieux, Marcyl-l’Etoile, France)

VIDAS system for estimation of SEA concentrations

InvestigationEpidemiological investigation Total estimated number of cases = 13420 Symptoms

1.Onset of symptoms: 83.4% of those with reported incubation periods, within 6 hours (peak time 3-4h)

2.96% of the remaining within 12 hours3.Symptoms: diarrhoea (75.9%); vomiting/nausea (73.3%); abdominal cramps (49.0%); and mild fever (11.9%)

Laboratory investigation Detection and estimation of SEA Measurement of SEA intake from leftover low-fat milk and powdered skim milk

Results 4795 (37.5%) of the total estimated cases (13,420) were

reported 4115 of those (85.8%) had ingested low-fat milk Number of cases among 0-10 years old was approx. 2.7

times higher than the rest Minimum SEA intake was 17ng and maximum 295ng (mean

55.6ng) 1 April 2000 operations at Hokkaido Factory were stopped

for approx. 3 h. The processing delay lasted over 9 h many products showed high c.f.u./g of viable bacterial counts and failed to meet the standards (<9900 c.f.u./g)

However, Asao et al. concluded that there was no information how food was contaminated and how SEA was produced

Conclusion The present extensive milk-product borne outbreak was the largest incident in past decades in Japan

SEA as the causative agent Children 0-10 years old were more susceptible Thermal stability of SEs in food is one of the most important in preventing staphylococcal food poisoning. Susceptible foods are produced with low numbers of staphylococci, they will remain free of enterotoxins and other food-poisoning hazards if kept either at or below 4.4˚C or above 60˚C until consumed

References Asao et al. (2003). An extensive outbreak of staphylococcal food poisoning due to low-fat milk in Japan: estimation of enterotoxin A in the incriminated milk and powdered skim milk. Epidemiol. Infect, 130: 33-40.

Jay, J. M., Loessner, M. J., and Golden, D. A. (2005). Modern Food Microbiology. 7th ed. New York: Springer-Verlag.