and/or insulin-dependent diabetes, and a
small number of cases may recur (Siegler
et al., 1993).
Thrombotic thrombocytopenic purpurea
is another illness associated with E. coli
O157:H7. It resembles hemolytic uremic syn-
drome, except that it normally causes renal
damage, has significant neurologic involve-
ment (i.e., seizures, strokes, and central nerv-
ous system deterioration), and is restricted
primarily to adults.
Ground beef has been the food most often
associated with outbreaks in the United
States. Dry-cured salami has been associated
with an outbreak revealing that low levels of
this pathogen can survive in acidic fermented
meats and cause illness. Other foods associ-
ated with this pathogen are unpasteurized
apple juice and cider. The largest reported E.
colioutbreak, which caused thousands of ill-
nesses, occurred in Japan in 1996 and was
associated with radish sprouts. Alfalfa
sprouts have been implicated in an outbreak
in the United States. Drinking water and
recreational waters have been vehicles of sev-
eral E. coliO157:H7 outbreaks (Doyle et al.,
1997).
Zhao et al. (1995b) found that 3.2% of
dairy calves and 1.6% of feedlot cattle tested
were found to be positive for E. coli
O157:H7. Deer have been found to be a
source of this pathogen, and the transmis-
sion of this microorganism may occur
between deer and cattle. Fecal shedding of
this pathogen has been found to be transient
and seasonal (Kudva et al., 1995). The preva-
lence ofE. coliO157:H7 in feces has been
found to peak in the summer and during
spring through fall on the hide (Barkocy-
Gallagher, 2003).
It appears that E. coliO157:H7 can grow
at 8 to 44.5ºC with an optimal temperature
of 30 to 42ºC. Growth rates are similar at pH
values between 5.5 and 7.5 but decline rap-
idly under more acidic conditions even
though this pathogen survives a low pH well.
The minimum pH for E. coliO157:H7 is 4.0
to 4.5. The survival ofE. coliO157:H7 in
acidic foods is important, as several out-
breaks have been associated with low levels
surviving in acidic foods, such as fermented
sausages, apple cider, and apple juice. This
pathogen has been shown experimentally to
survive for several weeks in a variety of
acidic foods, such as mayonnaise, sausages,
and apple cider. Survival in these foods is
extended when stored at a refrigerated tem-
perature (Zhao et al., 1995a).
The destruction ofE. coliO157:H7 can be
accomplished by cooking ground beef to
72ºC or higher, or incorporating a procedure
that kills this pathogen in the manufacture of
fermented sausages or the pasteurization of
apple cider. According to Buchanan and
Doyle (1997), the HACCP system is the most
effective means for systematically developing
food safety protocols that can reduce infec-
tion from this pathogen. The low incidence
of this pathogen limits the utility of direct
microbial testing as a means of verifying the
effectiveness of HACCP.Listeriosis
Listeria monocytogenes is an especially
dangerous pathogen because it can survive at
refrigerated temperatures. Previously, liste-
riosis has been considered rare in humans.
However, foodborne outbreaks since the
1980s have increased public health concern
over this pathogen. Listeriosis causes an esti-
mated 2,500 serious illnesses and 500 deaths
annually (CFSAN, FSIS, 2001). Individuals
in certain high-risk groups are more likely to
acquire listeriosis. Pregnant women are
approximately 20 times more susceptible
than other healthy adults (Duxbury, 2004).
L. monocytogenes is an opportunistic
pathogen, as it is not expected to cause
severe disease in healthy individuals with
strong immune systems (Russell, 1997).