Lettuce, Leafy Greens And E. Coli

The rise in year-round consumption of fresh leafy greens such as lettuce and baby
spinach is increasing the difficulty of keeping produce free from contamination by
food poisoning bacteria, according to US scientists speaking at the Society for General Microbiology's 161st Meeting at the University of Edinburgh, UK, which runs from 3-6 September 2007.



"The only land suitable for supplying this abundance of year-round, high quality,
fresh leafy vegetables, which are eaten raw by large populations in Europe and the
United States, is in special geographic regions, with ideal soil and climate
conditions", says Robert Mandrell from the US Department of Agriculture's
Research Service in Albany, California.



This move to the year-round supply of leafy vegetables has required new methods
to clean, package and deliver rapidly these fragile food items across large distances
to consumers in many parts of the world. These include harvesting mowers for
some leafy greens, processing in water flumes and triple washing, and modified
atmosphere packaging for extended shelf-life.




Recent food scares and food poisoning outbreaks have led to intensive
investigations of farms and ranches. These have shown that at least some food
poisoning bacteria outbreaks have been due to field contamination before the
greens are even harvested.



"This situation complicates strategies for eliminating illnesses and outbreaks due to
the complex ecosystem of multiple potential sources, such as water, wildlife, and
nearby livestock, all of which could be sources of bacteria causing food poisoning",
says Robert Mandrell.



Following wide media coverage of outbreaks caused by E. coli in leafy vegetables
and Salmonella in tomatoes, the US fresh produce industry and federal and state
agencies are trying to address the microbial food safety of leafy greens and other
vegetables. Major US produce industry associations have worked together to
establish a marketing agreement, a set of food safety guidelines (metrics) for
growers to produce and harvest leafy greens, and have increased funding for
research.



Probably, a convergence of unusual events is required for very large outbreaks to
occur, a factor everyone is hoping will not affect 2007 harvests. Logical theories
about pre-harvest contamination provide points for study, but no definitive
conclusions about the most recent outbreaks can be provided. Fresh, minimally
processed leafy greens are here to stay, if the industry continues to work hard to re-
establish consumer confidence.


Dr Mandrell is presenting the paper 'Fresh leafy greens and Escherichia coli O157:H7:
outbreaks, incidence in the environment, source-tracking' at 0945 on Monday 03 September
2007 in the Microbial Infection Group session of the 161st Meeting of the Society for General
Microbiology at the University of Edinburgh, 03 - 06 September 2007.




Full programme details of this meeting can be found on the Society's website here. Hard copies are available on
request from the SGM.



The Society for General Microbiology is the largest microbiology society in Europe, and has
over 5,500 members worldwide. The Society provides a common meeting ground for
scientists working in research and in fields with applications in microbiology including
medicine, veterinary medicine, pharmaceuticals, industry, agriculture, food, the environment
and education.



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