BLBS102-c44 BLBS102-Simpson March 21, 2012 14:34 Trim: 276mm X 219mm Printer Name: Yet to Come
838 Part 8: Food Safety and Food AllergensMycobacterium aviumSubspparatuberculosisM. aviumsub speciesparatuberculosis(MAP) is a relatively new
emerging disease of human illness. The organism MAP is part
of a complex group of related organisms (Motiwala et al. 2006).
The organisms within the group have high-level identity at the
genetic level but differ in host source, disease phenotypes, and
pathogenicity. Members of the group identified asM. aviumare
associated with disease in both animals and humans. Of interest
is the association betweenM. aviumand immunocompromised
patients (AIDS) and its links to Chron’s disease (Mycobacterium
paratuberculosis) (Harris and Lammerding 2001, Greenstein
2003, Ghadiali et al. 2004, Karakousis et al. 2004).M. paratu-
berculosisis recognized as the causative agent of Johne’s disease
in ruminants and is recognized by chronic gastroenteritis, which
can be debilitating.
In humans, Chron’s causes a similar type of disease to that
observed in animals and may be linked with MAP (Harris and
Lammerding 2001); the association between Chron’s disease
and MAP does, however, remain controversial. Chron’s disease
appears to occur in a range of age groups of the population with
cases observed in adolescents and in patients older than 50 years.
Recognized sources of MAP include the feces of infected an-
imals, the environment, milk, foods, and contaminated drinking
water (Glover et al. 1994, Grant et al. 1998, Yoder et al. 1999,
Argueta et al. 2000, Grant et al. 2000, Raizman et al. 2004,
O’Reilly et al. 2004). Methods using polymerase chain reaction
(PCR) are valuable for the detection of MAP because of the
extended periods of incubation required to detect the pathogen
and the state of the cells that may make the organism difficult to
detect by standard culture methods.
MAP may also be linked to milk. Studies have demonstrated
that the organism survives pasteurization and may be present in
raw and pasteurized milk. Grant et al. (1998, 2000) reported on
the detection of MAP in milk using immunomagnetic separation
(IMS). More recent studies have found the prevalence of MAP
to be 12% in raw milk and 9.8% of pasteurized using IMS PCR.
However, no viable cells were found, only DNA was detected
suggesting that the pasteurization process destroyed cell viabil-
ity. In the same study, only one raw milk sample was positive for
MAP (O’Reilly et al. 2004). Others have assessed the prevalence
of MAP in a range of produce from retail stores and supermar-
kets finding that of 129 foods sampled, 25 were positive for
Mycobacteriawith half of all isolates recovered identified asM.
avium(Argueta et al. 2000). Yoder et al. (1999) demonstrated
the relatedness of strains recovered from human disease with
those found in foods, supporting the role of foods as a source of
Mycobacteriafor human disease.
In human cases of Crohn’s disease, a chronic condition re-
sulting in significant intestinal disease; it is recognized in three
forms including inflammatory, structuring, and stenosing and
fistulizing (Andres and Friedman 1999, Kirsner 1999). The pri-
mary location of disease is the distal ileum and colon. Cur-
rently, there is no known cure for Crohn’s, with up to 74% of
patients requiring surgery (Andres and Friedman 1999). Links
between Chron’s and MAP varies significantly and the epidemi-
ology of the disease is not well understood although the or-ganism has been recovered from the tissues of Crohn’s patients
(Sechi et al. 2004). Treatment of Crohn’s uses combinations
of anti-inflammatories, steroids, and antibiotics until the patient
experiences relief. Some antimycobacterial drugs used include
rifabutin-macrolide-clofazimine (Shafran et al. 2000). Although
the data on MAP are limited, its potential as an emerging food-
borne pathogen at this time cannot be discounted and warrants
further epidemiological studies.Aeromonas hydrophilaThe genusAeromonasis a member of the family Aeromon-
adaceae and consists of 24 different species (Janda and Ab-
bott 2010); this number is, however, continuously expanding
with over 3500 new species proposed (Janda and Abbott 2010).
Aeromonasis a gram-negative facultative anaerobe that appears
to be ubiquitous in water and foods. The role ofAeromonas
in food-borne disease is not well understood but is suspected
and there is evidence of the pathogen in reported outbreaks.
Aeromonasis capable of growth at refrigeration temperatures
with an optimum growth range of 28◦C and in a pH range of
5.5–9.
Most aeromonads are considered opportunistic in aquatic and
terrestrial animals but can also be a pathogen of man and has
been recognized as so since 1984 (Tsai and Chen 1996). Epi-
demiological evidence suggests that aeromonads can cause gas-
troenteritis in humans (Deodhar et al. 1991, Kuhn et al. 1997, von
Grawvenitz 2007) and other complications such as wound in-
fections, septicemia, and endocarditis (Janda et al. 1994, Broqui
and Raoult 2001).Aeromonasappears to act as both an infec-
tious agent and an enterotoxigenic pathogen (Kingombe et al.
1999). Members of the species of interest in food-borne disease
appear to be associated with strains identified asA. hydrophila,
Aeromonas sobria,andAeromonas caviae(Gavriel et al. 1998).
The relationship between motile aeromonads and food-borne
illnesses is tentative; a few reports have linked illness to foods
consumed such as shrimp cocktail (Janda and Abbott 1999) and
oysters (Abeyta et al. 1990).
In humans, food-relatedAeromonasillness is associated with
gastroenteritis, with most cases affecting children, the elderly,
and the immunocompromised (Isonhood and Drake 2002); an-
nually it is estimated thatAeromonasmay be responsible for
up to 13% of all cases of gastroenteritis in the United States
(Kingombe et al. 1999). The infectious dose ofAeromonasto
cause human illness is unknown as is the mechanism of vir-
ulence; however, gastroenteritis, wound infections, and sep-
ticemia appear to be recognized as consequences of infection
(Janda and Abbott 2010).
Aeromonashas been isolated from a range of foods and en-
vironments including retail vegetables, seafood, meats, cheese,
and milk (Okrend et al. 1987, Abeyata et al. 1990, Kirov et al.
1993a, 1993b, Pon et al. 1995, Saad et al. 1995, Tsai and Chen
1996, Kuhn et al. 1997, Gavriel et al. 1998, Yadav and Verma
1998).
As with other emerging pathogens, our recognition of
Aeromonasas an emerging pathogen of significant human