Microbiological Aspects of Dairy Ingredients 63intra - uterine infection that causes high mor-
tality in the affected fetus or newborn child.
Listeriosis outbreaks have been linked to
consumption of raw milk and raw milk
cheese. Cattle may be infected via poorly
made silage. It can be detected using a real -
time PCR assay using primers to amplify a
149 - bp fragment from the metalloprotease
gene ( mpl ) (Vanegas et al., 2009 ). The organ-
ism has been detected in raw bulk milk at a
frequency of 1% to 12%.
Mycobacterium bovis. Mycobacterium
bovis is acid fast at some stage in its life
cycle; as a result, after initial staining it
resists decolorization with dilute mineral
acid. It has a broad host range covering
domestic and wild animals. Consumption of
raw milk or products made from raw milk is
thought to be the main route of transmission
to humans. Many countries operate control
programs for cattle with varying degrees of
success.
Human infection can result in a range of
clinico - pathological outcomes. In the major-
ity of cases the host inhibits proliferation of
the organism and no clinical signs of disease
are apparent. However, if the host is chal-
lenged, e.g., by some other disease process,
the organism will resume growth, ultimately
resulting in the death of the host. Culture is
the primary method of detection, and it is
usually preceded by a decontamination step.
PCR assays are available, targeting the inser-
tion element IS6110 and antigen genes such
as mpb70 and mpb64. Mycobacterium bovis
is still considered an important cause of non -
pulmonary tuberculosis, with 109 cases
reported between 1977 and 1981 in southeast
England (Collins and Grange, 1983 ) and 1 to
5 cases reported annually in Ireland from
1983 to 1994 (Cotter et al., 1996 ). For more
information, see Rowe and Donaghy (2008).
Salmonella spp. Salmonella spp. are
Gram - negative bacteria that are not usually
psychrotrophic. Cattle shedding the organism
are often asymptomatic and diffi cult to iden-
tify. The organism can be shed fecally andof infectious diarrhea in developed countries
(Garenaux et al., 2005 ). Symptoms resem-
bling fl u develop in approximately one - third
of patients suffi ciently ill to seek medical
attention. This usually occurs 2 to 3 days
before the onset of diarrhea, which is sudden
and can be severe (Ryser, 2001 ). Although
most patients spontaneously recover within 3
to 7 days, in a small number of cases severe
complications can result, namely Guillian -
Barr é syndrome and reactive arthritis
(Nachamkin and Guerry, 2005 ).
Raw milk is one known vehicle of trans-
mission, and there have been many cases of
campylobacteriosis amongst school children
on fi eld trips and farm visits involving con-
sumption of raw milk. Contamination of raw
milk is mainly via the fecal route, though
Camp. jejuni is an infrequent cause of mas-
titis in which case the organism is excreted
directly. Numerous outbreaks of food poison-
ing have been reported in the United States.
For example, between 1978 and 1996 there
were 111 outbreaks affecting 9,913 known
individuals (Friedman et al., 2000 ). The
organism is sensitive to heat (inactivated by
pasteurization), acid (pH less than or equal
to 5.0), oxygen, and dehydration. Campylo-
bacter jejuni can be detected using a PCR
assay based on a 286 - bp fragment of the
mapA gene specifi c to the species (Inglis and
Kalischuk, 2004 ).
Helicobacter pylori. Helicobacter pylori
is a microaerophile that causes gastritis and
peptic ulcers and is a key factor in the devel-
opment of gastric cancer, gastric lymphoma,
and nonulcerative dyspepsia in humans. Its
best known genotypic virulence factors are
cytotoxin - associated gene A ( cagA ) and vac-
uolating cytotoxin gene A ( vacA ). It can be
detected using a nested PCR based on the
phosphoglucosamine mutase gene ( glmM ) or
in humans using the C^13 - urea breath test. For
more information, see Fujimura et al. (2002).
Listeria monocytogenes. Listeria mono-
cytogenes is a psychrotroph that is respon-
sible for meningo - encephalitis and an