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Bacterial
Food
Infections |
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Bacterial
Food
Infections -
Bacterial
food
infections
include
salmonellosis,
Clostridium
perfringens
gastroenteritis,
Vibrio
parahaemolyticus
infection
etc.
Salmonellosis
is
an
infection
resulting
from
ingestion
of
the
vegetative
cells
of
Salmonella
and
is
the
most
frequently
occurring
bacterial
food
infection.
Salmonella
infection
can
be
caused
by
a
large
number
of
species
and
serotypes
of
Salmonella.
These
bacteria
grow
well
in
the
food
at
room
temperatures
and
have
a
pH
range
optimum
for
growth
between
4.1
to
9.0.
Thus,
they
can
also
grow
in
low
acid
foods.
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The
lowest
aw
for
growth
varies
with
the
food
but
varies
from
0.93
to
0.95.
These
organisms
can
attain
considerable
numbers
causing
detectable
changes
in
appearance,
odour
or
taste
of
foods
in
which
they
grow.
Infection
follows
consumption
of
the food.
Both
animals
and
human
beings
are
directly
or
indirectly
the
sources
of
contamination
of
food
with
Salmonella.
The
organisms
may
come
from
either
actual
cases
of
disease
or
from
the
carriers.
The
organisms
may
also
come
from
cats,
dogs,
chickens,
cattle
and
other
animals.
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Individuals
differ
in
their
sensitivity
to
Salmonella
infection
but
in
general,
morbidity
is
high
in
any
outbreak.
Susceptibility
varies
with
the
species,
strains
and
the
total
number
of
bacteria
ingested.
The
incubation
period
usually
is
between
4-36
hours
compared
to
2-6
hours
in
the
case
of
staphylococcal
poisoning.
Typical
symptoms
of
Salmonella
gastrointestinal
infections
are
nausea,
vomitting,
abdominal
pain
and
diarrhoea
that
usually
appear
suddenly
and
which
may
be
preceded
by
headache
and
chills.
Mortality
is
low
and
the
severity
and
the
duration
varies
with
the
number
of
bacteria
ingested.
Usually
symptoms
persist
for
2-3
days.
Salmonella
out
breaks
can
be
prevented
by
avoiding
consumption
of
contaminated
food,
destruction
of
Salmonella
by
heat
or
by
the
prevention
of
Salmonella
growth
by
refrigeration
or
by
other
means.
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E.
coli
is
generally
regarded
as
a
part
of
the
natural
flora
of
the
human
and
animal
intestinal
tract.
However,
in
recent
years,
several
serotypes
of
E.
coli
have
been
implicated
in
human
and
animal
diarrhoeal
diseases.
The
organisms
responsible
for
such
food
poisoning
outbreaks
have
been
designated
as
enteropathogenic
E.
coli
(EEC)
.
Some
of
these
EEC
produce
an
enterotoxin
which
causes
cholera
like
or
enterotoxigenic
illness
in
humans.
This
can
be
serious
specially
in
children.
Following
ingestin
of
these
organisms,
the
bacteria
colonize
the
upper
intestine
and
produce
an
enterotoxin
which
apparently
mediates
the
movement
of
water
in
the
intestinal
lumen.
Such
fluid
accumulation
occurs
in
the
absence
of
invasive
bacteria.
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Other
groups
of
E.
coli
that
cause
colitis
(dysentry
like
syndrome)
are
nonenterotoxigenio
but
penetrate
the
epithelial
cells
of
the
colonic
mucosa.
For
either
the
enterotoxigenic
or
the
invasive
illness
to
occur
a
large
dose
of
the
EEC
is
required.
Therefore,
foods
which
are
highly
contaminated
or
inadequately
preserved
allow
the
growth
of
these
organisms.
These
organisms
al
e
relatively
heat
sensitive
and
can
be
readily
destroyed
by
pasteurization
or
by
proper
cooking
methods.
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Vibrio
parahaemolyticus
gastroenteritis
is
also
a
commonly
occurring
food
intoxication.
This
organism
which
is
a
Gram-negative,
curved
rod
shaped
and
motile
will
grow
at
seven
per
cent
salt
concentration
with
an
optimum
temperature
of
35-37°C.
This
has
been
isolated
from
many
sea
foods
but
can
be
killed
by
proper
cooking.
Other
organisms
implicated
in
food
borne
disease
outbreaks
are
species
of
Yersinia,
Arizona,
Streptococcus
pyogenes
and
S.
faecalis.
The
food
infections
caused
by
these
result
from
the
growth
and
increase
in
the
dosage
of
the
pathogen.
Some
of
these
organisms
can
tolerate
a
salt
concentration
of
5-6
per
cent.
However,
no
enterotoxin
production
by
these
organisms
has
been
so
far
demonstrated.
Among
the
spore
forming
bacteria
that
cause
food
infections
are
the
Clostridium
perfringens
and
Bacillus
cereus.
Clostridium
perfringens
gastroenteritis
is
caused
by
C.
perfringens
(welchii)
which
is
a
Gram
positive,
anaerobic,
nonmotile
spore
former
with
an
are
optimal
growth
temperature
of
37-43°C.
Spores
of
this
organism
are
heat
resistant
and
are'
found
in
raw
food,
soil,
sewage
and
animal
faeces.
Most
commonly,
meat
that
has
been
cooked
and
allowed
to
cool
slowly
before
consumption
permits
the
growth
of
these
organisms.
Cooking
destroys
only
the
vegetative
cells
and
during
cooling,
germination
and
growth
of
spores
occurs,
if
the
food
is
not
adequately
refrigerated.
Symptoms
of
the
disease
which
appear
following
ingestion
of
the
food
in
8-24
hours
are
acute
abdominal
pain
and
diarrhoea.
Fever
and
nausea
are
rare.
Ingestion
of
millions
of
viable
cells
ore
required
for
symptoms
to
appear.
The
enterotoxin
is
released
in
the
gut
during
sporulation
and
results
in
excessive
fluid
accumulation
in
the
intestinal
lumen.
The
enterotoxin
is
relatively
heat
sensitive
and
is
inactivated
at
60°C
for
10
minutes.
Prevention
of
outbreaks
includes
rapid
cooling
of
cooked
meats
and
other
foods
and
reheating
of
left
overs
before
consumption.
Bacillus
cereus
which
is
a
Gram
positive,
aerobic
spore
forming
rod-shaped
organism
has
been
reported
as
an
etiologic
agent
in
numerous
food
poisoning
outbreaks.
The
spores
are
heat
resistant
and
survive
considerable
degree
of
cooking.
For
symptoms
to
develop,
large
number
of
cells
have
to
be
ingested.
The
mechanism
of
pathogenicity
is
believed
to
involve
lysis
of
the
bacterial
cells
in
the
intestinal
tract
and
the
release
of
enterotoxin
which
appears
to
be
a
protein.
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