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836 Part 8: Food Safety and Food Allergensfluoroquinolone resistance in human isolates and those of pro-
duction animals (Endtz et al. 1991, Engberg et al. 2001), while
resistance to other antimicrobials has also been recognized in-
cluding macrolides, tetracycline, aminoglycosides,β-lactams,
and so on (Olah et al. 2006, Zhang and Plummer 2008, Lunag-
tongkum et al. 2009, Logue et al. 2010).
Resistances observed have been linked to the use of antimicro-
bial agents in food production animals, which can result in the
selection or creation of drug-resistant strains (Endtz et al. 1991,
Engberg et al. 2001, Logue et al. 2010). InCampylobacter,an-
timicrobial resistance is associated with a range of mechanisms
including efflux pumps and point mutations (Lin et al. 2002,
Taylor and Tracz 2005, Olah et al. 2006, Zhang and Plummer
2008, Logue et al. 2010, Guo et al. 2010). For detailed reviews
of antimicrobial resistance mechanisms inCampylobacter, see
Taylor and Tracz (2005), Zhang and Plummer (2008), and Lu-
nagtongkum et al. (2009).
Pathogenesis inCampylobacteris associated with the ability
to invade host cells, motility, and the production of cytolethal
distending toxins which causes diarrhea (Nachamkin 2007); the
presence of the pVir plasmid also appears to have a role in
pathogenesis (Larsen and Guerry 2005). WhileCampylobacter
appears to have emerged as a pathogen of human concern, its
recognition as an agent of significant importance in human dis-
ease and its standing as the primary or secondary most common
food-borne pathogen warrants its continued study.Escherichia coliIncluding STECWhileE. coliis a common contaminant of meats, of significance
are strains implicated in human disease including EHEC and
other STEC. EHEC have been recognized as a significant cause
of hemorrhagic colitis and complications associated with infec-
tion including hemolytic uremic syndrome (HUS) and throm-
bocytic purpura TTP (Ray 2004d). The organism was first rec-
ognized in 1982 as the cause of two major outbreaks of hemor-
rhagic colitis (Meng et al. 2007). Since that time, other serotypes
associated with hemorrhagic colitis have been recognized and
the list continues to grow. More than 600 serotypes of STEC
are recognized and about 130 different types of EHEC have
been recovered from patients presenting with hemorrhagic coli-
tis (Meng et al. 2007).
One of the most common agents of EHEC isE. coliO157:H7,
which has caused devastating disease worldwide. O157 strains
are typically associated with beef cattle, beef, and beef products;
however, other sources of the organism are now recognized in-
cluding domestic and wild animals as well as meats, milk, veg-
etables, and so on. (Ray 2004d, Meng et al. 2007, Mor-Mur and
Yuste 2010). Sources typically implicated include beef, beef
products, luncheon meats, salami, and more recently outbreaks
have been linked to unusual foods such as spinach and apple
juice (CDC 1997b, CDC 2002, CDC 2006, Mor-Mur and Yuste
2010).
Of importance with O157 is the low dose (<100 organisms)
required to cause human illness, which has been reported world-
wide (Meng and Doyle 1998, Ray 2004d, Meng et al. 2007).
The pathogenesis ofE. coliO157 and other STEC is related toits ability to adhere to the host cell membrane, colonize the large
intestine, and produce cytotoxic factors and cytolethal toxins
including Shiga toxins. Toxins produced can become absorbed
into the bloodstream where they cause further damage of blood
vessels of the intestine, kidneys, and brain.
Symptoms of infection usually occur within 3–9 days after
consumption of contaminated foods and generally last 4 days.
Colitis symptoms usually include sudden onset of abdominal
cramps, watery diarrhea, which in some cases becomes bloody
(about 35–75% of cases can become bloody), followed by vomit-
ing. The presence of toxins in the bloodstream cause breakdown
of red blood cells and can cause clotting in small blood vessels
of the kidney, which can cause kidney damage and failure, thus
resulting in HUS.E. coliO157 infections can be fatal in young
children. In addition,E. coliO157:H7 can cause brain damage
as a result of TTP where blood clots in the brain lead to seizures
and coma or death.
The largest outbreaks ofE. coliO157 have been associated
with ground meats (e.g., CDC1997a, CDC 2002); other sources
of the organism have included raw milk, apple cider, fermented
meats such as salami and pepperoni, sprouts, spinach, salads
(CDC 1995a, 1995b, CDC 1997b, 1997c, CDC 2005b, CDC
2006, CDC 2008).
E. coliO157:H7 does not grow well at temperatures more than
44.5◦C but does appear to have increased acid tolerance. The pH
range for growth is 4–4.5 (Meng et al. 2007).E. coliO157 strains
also display resistance to antimicrobials including streptomycin,
tetracycline, and sulfisoxazole, which appear to be the most
common resistance profiles observed (Meng et al. 2007) and care
should be take when prescribing antimicrobials for treatment of
disease as it may exacerbate illness. The importance ofE. coli
O157:H7 as an emerging (and continuing to emerge) pathogen
that warrants its continued status as a significant pathogen of
human concern; the observation of novel foods that have been
implicated in human illness is ever changing, warranting careful
monitoring.Listeria monocytogenesL. monocytogenesis a gram-positive organism that is ubiquitous
in nature and found in a range of environments. Of all theListeria
species,L. monocytogenesis of primary importance in human
disease. The organism can be a significant health risk for the
unborn, newborns, infants, the elderly, pregnant women, and
immunocompromised individuals.
Listeriais a psychrotroph, capable of growth at refrigera-
tion temperatures, which poses a significant health risk and has
been linked to food-borne outbreaks (Lianou and Sofos 2007,
Swaminathan and Gerner-Smidt 2007). Therefore, contamina-
tion of postprocessed foods may pose a significant health risk to
susceptible individuals.
While the incidence of listeriosis in the United States is rela-
tively low, the CDC estimates about 2500 cases occur per year
with 500 deaths.Listeriais a significant public health concern
because of the severity of disease in susceptible populations. In-
dividuals exposed toListeriausually through the consumption
of contaminated foods may or may not present with symptoms