Tag Archives: Tomatoes

Greenhouse vegetable food safety: Watch those dirty boots

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The April 2008 issue of Journal of Food Protection contains a cool paper on a survey of Salmonella and E. coli at a greenhouse tomato farm in Mexico. During 2003 and 2004 the authors sampled over 1600 product and environmental samples, before, during and after a couple of environmental disturbances: a flood and the entry of wild animals (opossums, mice and sparrows).

The authors isolated Salmonella Montevideo, Salmonella Newport, and strains of the F serogroup  from tomatoes and go on to state that almost all of the Salmonella Newport strains were isolated from samples collected during or immediately after the flood.

Analysis by pulsed-field gel electrophoresis revealed that some Salmonella Montevideo isolates from tomatoes, opossums, and mice displayed identical genetic patterns, suggesting that these wild animals represented a potential source of contamination.

The fun part of paper is that the authors suggest that dirty work shoes were also thought to be an important vehicle for dissemination of Salmonella into (and possibly throughout) the greenhouses (especially after being worn during the flood incident):

Contaminated worker shoes may be vehicles for contamination with enteric pathogens, from either outside the greenhouses or from one facility to another. The levels of E. coli on personal shoes were higher than those of working  shoes were before the flood. However, there was a higher  level of contamination with Salmonella and E. coli on  working shoes compared with personal shoes after the flood.

The authors go on to say that sanitary mats intended to reduce pathogen movement may not be all that effective the real-world application:

Working shoes were provided by management to the workers to wear inside the greenhouse at the suggestion of our research group after finding that personal shoes were positive for E. coli, even after shoes received a disinfection treatment with quaternary salts solution (800 ppm) on a sanitary mat. However, working shoes were not used exclusively inside the greenhouse, but were also worn to go from one facility to another. Shoes have seldom been mentioned as vehicles of contamination in food production areas. This dissemination mechanism of enteric pathogens should be considered as an important control point  during working procedures in greenhouses.

It’s unclear whether this is just a notable finding, or if it represents a real risk in moving pathogens around food production systems, and needs some further investigation.  Probably don’t want to use boots to stomp garlic though.

Salmonella outbreak at Rochester, Minn Quizno’s potentially linked to tomatoes

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This week’s iFSN infosheet focuses on more information on last month’s Salmonella outbreak at a Quizno’s that was reported by the Rochester Post-Bulletin this week. 
Health officials believe that produce, and maybe specifically tomatoes are to blame for the 22 illnesses.  They also suggested that the produce was likely contaminated before arriving at the fast-food outlet as staff and patrons (who likely ate the same ingredients) became ill around the same time. This outbreak highlights the need to ask questions about food safety to suppliers, especially around how they handle produce and select the growers they purchase from.

Tomatoes have been linked to Salmonella outbreaks before, click here for a list of past tomato-related outbreaks. 

Click here to download the infosheet

It’s OK, just say it, tomatoes can be a risk

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Ben Chapman and I wrote in the Windsor Star today that self-proclaimed food safety guru Dan Dempster, president of the Canadian Produce Marketing Association, either knows something about the microbial safety of fresh produce that has escaped, oh, everyone else, or he is spinning when he says that produce "is actually the safest fresh food group."

Yeah, compared to fresh ground beef, produce looks safe; but consumers ain’t lining up for cooked lettuce.

As we wrote,

"It’s easy to write off Dempster’s letter as a marketing puff piece, which it is, especially since he had a real opportunity to acknowledge the risks associated with fresh fruits and vegetables and focus on the proactive efforts the produce industry is taking to actively reduce them."

What’s not puff is the report from the U.S. Centers for Disease Control report on multistate outbreaks of Salmonella infections associated with raw tomatoes eaten in U.S. restaurants in 2005 and 2006.

"During 2005–2006, four large multistate outbreaks of Salmonella infections associated with eating raw tomatoes at restaurants occurred in the United States. The four outbreaks resulted in 459 culture-confirmed cases of salmonellosis in 21 states."

In Virginia in 2005, the outbreak strain of S. Newport was isolated from irrigation pond water near tomato fields. In another outbreak, the tomatoes were grown in Florida near multiple potential animal reservoirs of Salmonella (e.g., cattle, wild pigs, wild birds, amphibians, and reptiles) present in and adjacent to the drainage ditches.

We’ve outlined lots of proactive steps that can be undertaken by fresh fruit and vegetable growers.

Too lame: Attack of the killer tomatoes

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The Washington Post reported today that teams involved with the U.S. Food and Drug Administration’s Tomato Safety Initiative have completed their Virginia visits and went to more than 50 growing fields and three packing facilities.

Jack Guzewich, a specialist in foodborne diseases at the FDA Center for Food Safety and Applied Nutrition, was cited as saying that because water can carry bacteria, investigators look at irrigation water, wells, chemical mixing procedures and the results of drought and flooding, adding,

"Animals can be anything from reptiles to birds and mammals — the whole zoological garden. Feces get into land and water, and, in some cases, an animal comes in contact with the plant."

FDA documents 12 outbreaks with a total of 1,840 cases of food-borne illnesses linked to fresh and fresh-cut tomatoes have occurred since 1998, and most were traced to Virginia’s Eastern Shore and Florida, two major growing areas, and a few to Georgia, South Carolina, Ohio and California. Salmonella was the main culprit.

The program will move to Florida during the fall growing season, with plans to reach other locales.

My team and I have spent a lot of time with greenhouse tomato growers in Ontario. There are numerous on-farm barriers to actually implementing good agricultural practices.

Check out our papers below:

Luedtke, A., Chapman, B. and Powell, D.A. 2003. Implementation and analysis of an on-farm food safety program for the production of greenhouse vegetables. Journal of Food Protection. 66:485-489.

Powell, D.A., Bobadilla-Ruiz, M., Whitfield, A. Griffiths, M.G.. and Luedtke, A. 2002. Development, implementation and analysis of an on-farm food safety program for the production of greenhouse vegetables in Ontario, Canada. Journal of Food Protection. 65: 918- 923.

We also published a book chapter entitled Implementing On-Farm Food Safety Programs in Fruit and Vegetable Cultivation, in the recently published, Improving the Safety of Fresh Fruit and Vegetables.