Agriculture Reference
In-Depth Information
at packinghouses and regional markets, results in commingling of produce items from
different farms, and makes traceback and recall of contaminated produce items very
diffi cult. With fresh-cut produce items (like leafy greens), this issue is a real concern,
since a batch of contaminated product from one farm can contaminate very large
amounts of product from a variety of other farms during processing. In addition, when
regulatory agency offi cials are investigating the cause of outbreaks, they often cannot
locate the product due to its perishability, since it has either been consumed or spoiled
and discarded (Guzewich 2008). In either case, the suspect produce item is often no
longer available to sample and test for pathogens. When offi cials go to farms to inves-
tigate, they fi nd that in many cases, the suspect crops have already been harvested and
there is no remaining produce from the suspected fi elds. So, produce outbreaks are
very diffi cult to trace back to their sources and in many outbreak investigations, the
route of produce contamination is often suspected, but never scientifi cally proven.
Fresh fruits and vegetables can become contaminated by biological hazards, such
as pathogenic organisms including bacteria, viruses and parasites, chemical hazards,
and physical hazards. These hazards have all caused illness or injury in fresh produce.
Biological hazards, particularly pathogenic bacteria, are the greatest concern because
the risk that they pose may be amplifi ed by growth prior to consumption (National
Research Council 2003) and have been responsible for most of the produce associated
outbreaks in the U.S. This chapter focuses primarily on the reduction of these hazards
through the implementation of good agricultural practices (GAPs).
The Nature of Pathogen Contamination
Produce can become contaminated from a variety of production and harvesting
techniques on the farm, through washing and sorting in the packinghouse, through
distribution in retail food stores and food-service facilities, and in the home.
Contamination can result from contact with the soil; manure; improperly composted
manure; irrigation water; fecal material from wild and domestic animals; farm, pack-
inghouse, and terminal market workers; contaminated equipment in fi elds, packing-
house, and distribution system; wash, rinse, and fl ume water; ice; cooling equipment
and transportation vehicles; cross-contamination from other foods; and improper
storage, packaging, display, and preparation (Bihn and Gravani 2006; FDA, USDA,
and CDC 1998).
Produce-associated outbreaks have been caused by a variety of bacterial pathogens
including
Salmonella
species,
E. coli
O157:H7
, Shigella, Campylobacter, Bacillus
cereus,
the parasites
Crytosporidium
and
Cyclospora,
and viruses hepatitis A and
norovirus. Table 5.1 shows a list of pathogens that have been implicated in produce-
associated outbreaks from 1994 - 2004 (Tauxe 2008 ).
Table 5.2 contains data available from the FDA and provides a list of fresh produce
items that have been contaminated and associated with outbreaks in the U.S. from 1996
to 2008, such as leafy greens, including lettuce, romaine, spinach, mixed lettuce, toma-
toes, cantaloupes and other melons, raspberries and frozen strawberries, green onions
(scallions), and basil and basil-containing products (Guzewich 2008; Vierk 2009).
Figure 5.3 illustrates the types of produce, by percentage, associated with the 82
outbreaks in the U.S. between 1996 and 2008 (Vierk 2008, 2009). It is noteworthy
