Agriculture Reference
In-Depth Information
18
Applications of Immunomagnetic Beads
and Biosensors for Pathogen Detection
in Produce
Shu-I Tu, Joseph Uknalis, Andrew Gehring, and
Peter Irwin
Introduction
Recent outbreaks of pathogenic bacteria on produce have been widespread with severe
consequences. Consuming hepatitis A-contaminated green onions sickened 555
persons and killed 3 from a restaurant in western Pennsylvania (CDC 2003). In
October 2006, spinach contaminated with
E. coli
O157:H7 infected 199 people in 28
states, resulting in 141 hospitalizations, 31 cases of kidney failure, and 3 deaths (Surak
2007). Shortly thereafter, lettuce contaminated with
E. coli
O157:H7 associated
with Taco Bell had 71 reported cases, with 53 reported hospitalizations and 8 cases
of kidney failure (CDC 2006). Particularly susceptible to foodborne illness are the
very young, the elderly, individuals with existing diseases, or immunocompromised
individuals. In addition to the human toll, these outbreaks of foodborne illness have
caused severe economic losses to food companies, consumers, and employers in
general.
Escherichia coli
0157:H7 has been implicated with increasing frequency from
outbreaks associated with fresh produce, including bean sprouts, cantaloupes, apples,
lettuce, spinach, tomatoes, etc. (Ackers and others 1998; Hillborn and others 1999).
The mechanisms by which the pathogen is introduced are not fully understood;
however, one hypothesis states that the plants may have been contaminated in fi elds
by exposure to contaminated animal feces and/or improperly treated manure (Beuchat
1999). Current epidemiological data indicate that
E. coli
0157:H7 may be present in
up to 8.3% of dairy and beef cattle (Faith and others 1996) and that it is shed asymp-
tomatically in the feces. Although current manure-handling guidelines recommend a
composting period to reduce microbial pathogens in manure before its application as
a fi eld fertilizer (FDA 1998), research has demonstrated that manure can support the
long-term survival of
E. coli
0157:H7 in a variety of conditions (Kudva and others
1998; Wang and others 1996). A second vehicle by which
E. coli
0157:H7 may be
introduced is fl ood irrigation with water contaminated with cattle feces or contact with
contaminated surface runoff (Ackers and others 1998; Hillborn and others 1999). A
number of recent
E. coli
0157:H7 outbreaks have been linked to contaminated water
(CDC 1999); furthermore, studies have demonstrated the ability of the pathogen to
survive for extended periods in water (Chalmers and others 2000; Wang and Doyle
1998 ).
The dose for
E. coli
0157:H7 to cause human illness is very low and may be as
few as 10 organisms (FDA 1998). Some victims, particularly the very young, have
developed the hemolytic uremic syndrome (HUS), which is characterized by renal
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