Agriculture Reference
In-Depth Information
such as
Salmonella, Campylobacter, Listeria monocytogenes,
and
Escherichia coli
O157:H7 are natural inhabitants of the gastrointestinal tract of livestock and may be
excreted in feces and remain viable in manure. The almost obligatory use of manure
in organic agriculture has led people to believe that organic produce would be more
susceptible to contamination with those pathogenic organisms than their conventional
counterparts. However, manure may also be used by conventional farmers who are
not restricted on how and when it can be spread onto fi elds.
The limitations in manure usage by the Organic Rule offer some level of protec-
tion but it has become apparent that they would not be able to control the transmis-
sion of foodborne pathogens from animal manure to fresh produce. If composting is
done following the organic guidelines, almost none of those pathogenic bacteria
would be able to survive, but it has been reported that composting in windrows is
often diffi cult to control (Forshell and Ekesbo 1993; Lung and others 2001). Some of
the problems associated with improper composting are due to the lack of uniform
heating, the cross-contamination of treated and raw manure, and the diversity of
composting systems (Brinton and Storms 2004). Although proper composting would
control pathogenic organisms, the guidelines for raw manure use may not offer
suffi cient protection.
When the Organic Rule was issued in the late 1990s there was very limited scien-
tifi c information about the survival of foodborne pathogens in manure and soil, but
the NOSB members had to formulate time recommendations (Sideman 2006). With
the few publications available they determined that 90 and 120 days would be suffi -
cient to minimize risks, but recent studies have suggested that pathogenic bacteria are
capable of surviving in the environment more than 120 days (Gagliardi and Karns
2002; Islam and others 2004).
Given these potential problems of current organic practices it seems apparent that
the safety of fresh produce can be compromised. As a result of these concerns,
a signifi cant number of studies have been devoted to investigate whether organic
fruits and vegetables pose a greater risk for transmission of foodborne pathogens.
Researchers have used a variety of approaches to assess the risk of organic fresh
produce and to address the question of whether they are more susceptible to pathogen
contamination. The three major strategies that scientists have taken include 1) patho-
gen survival studies as affected by organic practices, 2) product testing surveys in
which the prevalence of pathogenic and indicator bacteria of organic produce is com-
pared to their conventional counterparts, and 3) identifi cation of organic practices
with increased risk of contamination. The following three sections discuss these
approaches.
Pathogen Survival in Manure, Compost, and Soil
Survival of
Salmonella
and
E. coli
O157:H7 in Manure and Compost
Application of untreated or improperly treated animal waste as fertilizers in agricul-
tural soil used for food production is a major concern for the production of any type
of fresh fruits and vegetables that will be eaten raw. A number of researchers have
studied survival of pathogens like
E. coli
O157:H7 and
Salmonella
in animal manure,
and various survival rates have been reported (Table 4.2). The range of survival
