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44 Emerging Bacterial Food-Borne Pathogens and Methods of Detection 835is estimated that nontyphoidalSalmonellawas responsible for
7039 illnesses per 100,000 people in 2008 (CDC 2010). The
organism colonizes a range of hosts of food animals including
poultry, cattle, and pigs and rarer animals such as bison (Li et al.
2004, Li et al. 2006, Mor-Muir and Yuste 2010).Salmonellahas
also been found in a range of other habitats including soil, water,
sewage, and so on.
Salmonellaoutbreaks are relatively common and have been
associated with a range of foods and meats including poultry,
beef, pork, and so on. Of interest are outbreaks of illness asso-
ciated with more unusual foodstuffs such as chocolate, (Werber
et al. 2005), shell eggs (Gantois et al. 2009), produce (Franz
and van Bruggen 2008), tomatoes (CDC 2005a), and peanut
butter (CDC 2009). Currently, there are over 2000 serotypes
ofSalmonellarecognized (Ray 2004b) and annual trends from
the CDC report common serotypes implicated in food-borne ill-
ness. The top two serotypes implicated includeS. typhimurium
andSalmonella enteritidis(CDC 2010) http://www.cdc.gov/
ncidod/dbmd/phlisdata/Salmonella.htm; some novel strains also
emerge on a regular basis.
Symptoms of human salmonellosis are usually observed as un-
complicated enteritis and enteric (typhoid) fever, which can re-
sult in a more complicated disease involving diarrhea, fever, ab-
dominal pain, and headache. Systemic infection may also occur
resulting in a chronic reactive arthritis (Smith 1994).Salmonella
invades the mucosa of the small intestine and can proliferate in
the epithelium, and produce a toxin, which causes inflamma-
tion and fluid accumulation in the intestine. The infectious dose
required to cause illness is relatively high, about 10^5 –10^6 organ-
isms. Most individuals develop symptoms within 24–36 hours
but the incubation time may be longer if the dose ingested is
lower. Symptoms usually last 2–3 days but patients may remain
carriers for periods of months after recovery.
Of greatest concern areS. typhimuriumDT104 strains ex-
hibiting multiple antimicrobial resistance to ampicillin, chlo-
ramphenicol, streptomycin, sulfonamides, and tetracycline (AC-
SSuT), most of the resistance appears to be chromosomally en-
coded (Threlfall 2000). These strain types have been recognized
worldwide and have also caused infection in humans through
consumption of contaminated foods including chicken, beef,
pork sausages, and meat paste and also through occupational
contact with cattle (Wall et al. 1995, Mor-Mur and Yuste 2010).
In recent years, the incidence ofS. typhimuriumDT104 appears
to be declining, while resistance to other antimicrobials includ-
ing extended spectrumβ-lactamases appears to be increasing
(Newell et al. 2010) and have been detected in both humans and
animals (Hasman et al. 2005).CampylobacterNext toSalmonella,Campylobacteris the most common cause
of human food-borne disease annually in developed countries.
In the European Union,Campylobacteris the most common
cause of acute food poisoning; over 20,000 cases were reported
in 2007 compared to 150,000 cases of salmonelosis (Westrell
et al. 2009). In the United States,Campylobacteris the sec-
ond most common cause of disease (gastroenteritis) responsiblefor approximately 845,000 illnesses annually and almost 100
deaths (CDC 2011).Campylobactergastroenteritis is typically
associated withC. jejuniandCampylobacter coli.
Campylobacteris found in a range of animal hosts includ-
ing cattle, lamb, pigs with poultry being implicated as a pri-
mary source (Niesen et al. 2006, Nachamkin 2007, Mor-Mur
and Yuste 2010). Additional sources ofCampylobacterinclude
water, sewage, raw milk, raw meats, and vegetables (Meng and
Doyle 1998, Chan et al. 2001, Inglis et al. 2004, Nachamkin
2007). Prevalence levels ofCampylobacterin food animals vary
significantly, whileCampylobacterlevels on pork products are
relatively low and may be related to postslaughter chill and dry-
ing effects, which significantly reduce the populations (Snijers
and Collins 2004). Raw and undercooked poultry appear to be
primary sources ofCampylobacterassociated with food-borne
illness (Olson et al. 2008, Mor-Mur and Yuste 2010, Newell
et al. 2010).
Campylobacteris a gram-negative organism and is a microaer-
obe with a requirement for low oxygen (microaerophilic) and a
temperature range of 35–42◦C for growth. The organism is gen-
erally a poor competitor, is sensitive to low pH, temperatures less
than 30◦C, pasteurization temperatures, and drying (Doyle and
Jones 1992). It does, however, appear to survive under refrig-
eration temperatures and freezing may cause cell reduction but
low levels of pathogen have been recovered (Blaser et al. 1980,
Jacobs-Reitsma 2000). The organism does not survive well in
foods and is easily destroyed by adequate cooking tempera-
tures (Meng and Doyle 1998, Nachamkin 2007).Campylobac-
teris not capable of growth outside the host, but studies have
demonstrated the survival of this pathogen on kitchen surfaces
(Humphrey 2001).
The two major strains ofCampylobacterimplicated in the ma-
jority of humanCampylobacterenteritis areC. jejuniandC. coli.
Typical cases of human campylobacteriosis include diarrhea, ab-
dominal cramps, profuse diarrhea, nausea, and vomiting; other
symptoms include fever, headache, and chills, in some cases
bloody diarrhea can occur, recurrence of symptoms (relapse) is
often reported. Symptoms of illness are usually observed within
2-5 days of ingestion of contaminated food and can persist for
up to 2 weeks. The infectious dose required to cause illness is
relatively low and is estimated at approximately 500 organisms
(Robinson 1981, Black et al. 1988). Additional complications
recognized include reactive arthritis, pancreatitis, meningitis,
endocarditis, and Guillain–Barr ́e syndrome a postinfection com-
plication of campylobacteriosis that causes peripheral nervous
system paralysis resulting in a flaccid paralysis of the limbs,
which can be life threatening (Blaser and Engberg 2008, Jacobs
et al. 2008).
Outbreaks of campylobacteriosis typically occur in the sum-
mer months with most being sporadic in nature (Olson et al.
2008). Most outbreaks have been linked with improperly pre-
pared or consumption of cross-contaminated, poorly handled
poultry (Alketruse et al. 1997, Friedman et al. 2000).
Of significant importance is the prevalence of antibiotic re-
sistance to agents such as fluoroquinolones and macrolides,
two of the primary agents used to treat human disease (En-
gberg et al. 2001, Lutgen et al. 2009). Studies have reported