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Eurosurveillance, Volume 7, Issue 38, 18 September 2003
Articles

Citation style for this article: Unicomb L, Kirk M, Hogg G, Jelfs P, Simmons G, Gregory J, Nicol C, Editorial team. Salmonella Montevideo in sesame seed-based products imported into Australia and New Zealand may have implications for Europe and elsewhere. Euro Surveill. 2003;7(38):pii=2296. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=2296

Salmonella Montevideo in sesame seed-based products imported into Australia and New Zealand may have implications for Europe and elsewhere

Leanne Unicomb1 (lunic@doh.health.nsw.gov.au), Martyn Kirk2, Geoff Hogg3, Peter Jelfs4, Greg Simmons5, Joy Gregory6, Carolyn Nicol7, and the Eurosurveillance editorial team (eurowkly@hpa.org.uk)8.

1OzFoodNet, Hunter Public Health Unit, Newcastle, Australia;2OzFoodNet, Department of Health and Ageing, Canberra, Australia; 3Microbiological Diagnostic Unit Public Health Laboratory, Melbourne, Australia; 4Institute of Clinical Pathology and Medical Research, Sydney, Australia; 5Auckland District Health Board, Auckland, New Zealand;6OzFoodNet, Department of Human Services, Melbourne, Australia; 7Institute of Environmental Science and Research Ltd, Porirua, New Zealand; 8Eurosurveillance editorial office

Since November 2002 Salmonella Montevideo has been detected in three food products imported into Australia and one product imported into New Zealand. This report summarises investigations into these contaminated products on behalf of the Communicable Diseases Network of Australia and New Zealand health agencies and discusses implications for Europe and elsewhere.

In Australia, S. Montevideo was detected in unopened imported tahini (sesame seed pulp, also known as tahineh) from Egypt, following the investigation of increased human infections in November 2002 in New South Wales. A specific laboratory survey of sesame seed-based products isolated the same serotype in helva (also known as halva; a sweet made from tahini) from Lebanon in April 2003. S. Montevideo was again isolated from tahini originating in Lebanon following routine testing in August 2003 by a commercial food producer in a separate Australian state, Victoria.

New Zealand also experienced an increase in cases of S. Montevideo infection in 2002 with 21 cases compared to 5 cases in 2001. Health agencies detected S. Montevideo in commercial hummus dip (made with chickpeas and tahini) in July 2003 following investigation of a customer complaint. The hummus was prepared locally in New Zealand. The Egyptian tahini used to prepare this hummus dip was also found to be positive for S. Montevideo.

The Egyptian tahini imported into Australia and New Zealand were made by the same manufacturer. The Lebanese helva and tahini had the same brand name and came from the same importer/distributor, which were different from the Egyptian products. All of these positive tests resulted in public recalls of contaminated products (http://www.foodstandards.gov.au/recallssurveillance/foodrecalls/currentconsumerlevelrecalls/tahinehmicrobialsalm2190.cfm).

Health agencies in New South Wales identified 55 human cases of S. Montevideo linked to the Egyptian tahini. In Victoria, there have been three cases of S. Montevideo possibly linked to tahini and/or hummus products, but no definitive links to recalled products have been confirmed yet. There were no human infections detected in association with the Lebanese helva. There were also human cases associated with the products in New Zealand where investigations are continuing.

Pulse field gel electrophoresis (PFGE) analysis performed on the human and Egyptian tahini samples in Australia has shown the strains to be indistinguishable. This pattern was also indistinguishable from isolates obtained from the helva and the recently recalled Lebanese tahini. The Australian 'outbreak' pattern is also indistinguishable from human and food isolates from New Zealand.

Montevideo is an uncommon serotype in Australia and New Zealand. These investigations and positive food tests show that there is an ongoing problem with contaminated sesame seed products from the Middle Eastern region of the world. Testing of tahini showed that the concentration of salmonella was low and detection sporadic. Routine testing of imported foods may not isolate salmonellae, but concentrations are still sufficient to cause human illness. This is particularly true when they are used as ingredients in other foods, which may provide an environment more suitable for bacterial growth.

In the spring of 2001 an outbreak of 25 cases of S. Typhimurium definitive phage type (DT) 104 occurred in Sweden that was due to the consumption of contaminated helva (1). The contaminated helva had been manufactured in Turkey. Within the European surveillance system, Enter-net (http://www.hpa.org.uk/hpa/inter/enter-net_menu.htm), there have been no increases reported recently in the incidence of S. Montevideo in any particular collaborating country.

Human infections associated with these products continue to occur. Countries detecting an increase in human infections of S. Montevideo should consider sesame seed based products as a source of infection and include appropriate questions in hypothesis generating interviews.

References:
  1. Andersson Y, de Jong B, Hellström L, Stamer U, Wollin R, Giesecke J. Salmonella Typhimurium outbreak in Sweden from contaminated jars of helva (or halva). Eurosurveillance Weekly 2001; 5(29): 19/07/2001. (http://www.eurosurveillance.org/ew/2001/010719.asp)

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