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Bacterial Food Intoxications |
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Bacterial
Food
Intoxications
A
bacterial
food intoxication refers
to
illness
caused
by
the
consumption
of
a
bacterial
toxin
formed
in
the
food,
while
a
bacterial
food infection
refers
to
illness
caused
by
the
entrance
of
the
bacteria
into
the
body
through
ingestion
of
contaminated
food
and
the
reaction
of
the
body
to
their
presence
or
to
their
metabolites.
Infections
in
which
food
serves
only
as
a
carrier
of
the
disease
but
does
not
allow
the
growth
and
multiplication
of
the
pathogens,
such
as
tuberculosis,
typhoid
fever,
cholera
etc.,
are
different
from
those
in
which
food
serves
as
a
culture
medium
for
growth
of
the
pathogens
such
as
Salmonella,
enteropathogenic
E.
coli,
Bacillus,
Clostridium
etc.
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There
are
two
major
food
intoxications
caused
by
the
bacteria.
These
are:
(i)
botulism
caused
by
the
presence
in
food
of
toxin
produced
by
Clostridium
botulinum,
and
(ii)
staphylococcal
intoxication
caused
by
the
toxin
produced
by
S.
aureus.Botulism
is
an
intoxication
caused
by
the
ingestion
of
food
containing
the
neurotoxin
(toxin
that
affects
the
nervous
system)
produced
by
anaerobic,
spore
forming
Clostridium
botulinum.
There
are
seven
types
of
toxins
recognized
on
the
basis
of
serological
specificity
.
Toxin
production
by
C.
botulinum
depends
on
the
ability
of
the
bacterial
cells
to
grow
in
food
and
to
autolyse.
Therefore
factors
influencing
spore
germination,
growth
and
toxin
production
such
as
the
composition
of
the
food,
temperature
of
storage
and
pH
are
important.
The
main
sources
of
botulism
are
canned
meat,
fish,
string
beans,
sweet
corn,
beets
and
other
low
medium
acid
foods.
Spores
of
C.
botulinum
survive
long
storage
periods
in
raw
and
precooked
frozen
foods
and
can
grow
when
conditions
are
ideal.
The
toxin
of
C.
botulinum
is
a
protein.
It
is
absorbed
mostly
in
the
small
intestine
and
paralyses
the
involuntary
muscles.
The
heat
treatment
necessary
to
destroy
this
toxin
depends
on
the
type
of
toxin.
For
example,
heat
treatment
at" 80°C
for
5.6
minutes
will
inactivate
type
'A'
toxin while
type
'B'
toxin
can
be
inactivated
only
by
heating
at
90°C
for
45
minutes.
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Typical
symptoms
of
botulism
usually
occur
within
12-36
hours
after
consumption
of
the
spoilt
food.
Early
symptoms
are
digestive
disturbances
followed
by
nausea,
vomitting,
diarrhoea,
together
with
dizziness
and
headache.
Double
vision
may
occur
early
and
there
may
be
difficulty
in
speaking.
Mouth
may
become
dry,
throat
constricted,
tongue
may
get
swollen
and
coated.
Involuntary
muscles
become
paralysed
and
paralysis
spreads
to
the
respiratory
system
and
to
the
heart.
Death
normally
results
from
respiratory
failure.
In
fatal
cases,
death
occurs
within
3-6
days
after
the
poisonous
food
has
been
ingested
but
the
period
may
vary.
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The
methods
of
botulism
prevention
include:
(i)
the
use
of
approved
heat
processes
for
canned
foods,
(ii)
rejection
of
all
spoilt
canned
foods,
(iii)
by
avoiding
food
that
has
been
cooked
and
not
well
heated,
and
(iv)
boiling
of
suspected
food
for
at
least
15
minutes.
The
only
known
method
of
successful
treatment
of
botulism
is
by
the
administration
of
antitoxin.
This
treatment
may
not
be
successful
once
the
symptoms
appear
but
may
prove
useful
if
administered
in
the
very
early
stages.
A
second
and
most
common
type
of
food
intoxication
is
the
staphylococcal
food
intoxication
resulting
from
the
ingestion
of
food
contaminated
with
the
enterotoxin
produced
by
certain
strains
of
S.
aureus.
The
illness
starts
usually
2-6
hours
after
ingestion
of
the
contaminated
food
and
is
manifested
by
the
onset
of
nausea,
vomitting,
abdominal
pain
and
diarrhoea.
In
severe
cases,
dehydration
and
collapse
may
occur.
The
symptoms
can
last
upto
24
hours
but
recovery
is
rapid
even
from
a
state
of
collapse.
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The
stapylococcal
enterotoxins
are
proteins
with
a
molecular
weight
of
30-35,000
daItons
and
are
composed
of
single
polypeptide
chains
The
toxins
are
resistant
to
proteolytic
enzymes
such
as
trypsin
and
renin.
Moreover,
the
toxins
are
relatively
beat
stable
and
subsequent
cooking
may
kill
the
staphylococci
but
the
toxin
may
still
remain.
Although
purified
toxins
may
be
inactivated
by
heat,
they
are
much
more
heat
resistant
when
they
are
in
foods.
Several
distinct
types
of
enterotoxins
are
produced
by
different
strains
of
S.
aureus
which
tan
be
identified
with
the
help
of
specific
antisera.
At
least
five
enterotoxins,
A,
B,
C,
D
and
E
have
been
identified
and
implicated
in
food
poisoning
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Staphylococci
are
commonly
found
on
the
skin,
nose
and
other
parts
of
healthy
people.
They
are
usually
transferred
to
the
food
through
the
hands
of
the
handlers.
If
the
contaminated
food
is
stored
at
temperatures
that
encourage
the
growth
of
these
organisms,
production
of
enterotoxins
may
occur.
It
is
important
that
all
susceptible
foods
such
as
cold
meat,
poultry,
cream
cakes,
cooked
sea
foods
etc.,
are
stored
at
low
temperatures
to
prevent
the
growth
of
these
bacteria.
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