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Although
the
'germ
theory'
of
disease
existed
for
a
long
time,
direct
involvement
of
germs
in
causing
disease
was
not
well
established.
Pasteur
had
discovered
that
spoilage
of
beer
and
wine
was
due
to
microorganisms
and
such
spoilage.
was
called
'disease'.
His
conclusions
on
wine
and
beer
spoilage,
made
him
to
reason
that
the
diseases
of
higher
animals
and
plants
were
also
caused
by
microorganisms.
A
little
earlier
to
this,
John
Bassi
in
1836,
had
shown
that
the
silk
worm
disease
was
caused
by
a
fungus
and
in
1845,
Berkeley
had
shown
that
the
potato
blight
disease
(The
Irish
disaster)
was
also
caused
by
a
fungus.
These
reports
bad
convinced
Pasteur
that
microorganisms
can
cause
disease
in
insects,
plants
and
in
animals.
This
period
in
fact,
marks
the
beginning
of
the
realization
that
microbes
can
cause
disease
of
higher
forms
of
life.
During
the
19th
century,
surgical
treatment
of
human
and
animal
diseases
had
come
into
practice.
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Most
patients
that
underwent
surgery
developed
severe
cases
of
sepsis
The
cause
of
sepsis
was
however,
not
known.
Joseph
Lister
(1827;'1912),
an
English
surgeon
was
following
the
experiments
of
Pasteur
very
closely
and
reasoned
that
sepsis
was
a
process
similar
to
fermentation
described
by
Pasteur
and
was
caused
by
microorganisms.
He
believed
that
the
microbes
entered
the
wound
through
air,
hands,
surgical
instruments
or
band
aids
and
caused
sepsis.
If
this
was
true,
he
argued,
one
should
be
able
to
prevent
sepsis
by
applying
the
principles
of
sterilization,
which
would
destroy
these
microorganisms.
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He
sterilized
the
surgical
instruments
used
for
surgery
by
boiling
in
water
and
conducted
surgery
under
a
spray
of
carbolic
acid
(phenol).
The
results
were
remarkable
and
led
to
a
drastic
reduction
in
the
number
of
septic
cases.
For
this
contribution,
Lister,
is
today
known
as
the
father
of
antiseptic
surgery.
Undisputable
evidence
to
show
that
microbes
cause
disease
in
animals
came
from
Robert
Koch
While
studying
the
anthrax
disease
in
cattle,
Koch
had
found
rod-shaped
organisms
in
the
blood
of
the
diseased
animals.
To
test
if
these
organisms
were
the
causative
agents
of
the
disease,
he
injected
healthy
mice
with
the
blood
from
a
diseased
animal.
To
his
surprise
he
found
that
the
disease
was
transmissible
to
the
mice.
This
he
was
able
to
do
successively
to
as
many
as
20
mice.
Next,
he
removed
a
piece
of
the
spleen
from
the
diseased
mice
and
transferred
it
to
sterile
serum
and
obtained
good
growth
(If
the
rod-shaped
organism.
By
injecting
these
organisms
into
healthy
animals,
he
was
able
to
reproduce
the
disease.
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From
these
studies
he
was
able
to
lay
down
certain
basic
criteria
for
the
identification
of
microorganisms
as
causative
agents
of
disease.
These
criteria
are
known
as
'Koch's
postulates'
and
are:
(i)
that
the
causative
agent
of
the
disease
must
be
present
in
every
diseased
animal,
(ii)
the
agent
must
be
isolated
from
the
diseased
animal
and
grown
in
pure
culture,
(iii)
the
isolated
infectious
organism
must
reproduce
the
disease
when
injected
into
a
healthy
susceptible
animal,
and
(iv)
the
same
infectious
agent
must
be
re
isolated
from
the
experimentally
diseased
animal.
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These
postulates
remain
useful
even
today
with
some
modifications
but
strict
adherence
is
difficult
under
certain
circumstances,
for
example,
in
some
cases
as
in
the
case
of
leprosy
bacterium
the
causative
organism
is
difficult
to
grow
and
test
for
Koch's
postulates.
Yet,
Koch's
postulates
have
contributed
significantly
to
the
development
of
basic
principles
of
microbiology.
Any
organism
before
it
is
implicated
as
the
causative
organism
of
a
disease
must
meet
these
basic
criteria.
The
work
on
anthrax
by
Koch,
established
the
role
of
microbes
in
disease.
Unaware
of
Koch's
work,
Pasteur
had
also
undertaken
the
study
of
anthrax
and
his
conclusions
were
similar.
These
early
studies
by
Koch
and
Pasteur
on
anthrax
firmly
established
the
germ
theory
of
diseases.
These
developments
in
medical
microbiology
led
to
the
creation
of
institutions
both
in
Paris
for
Pasteur
and
in
Berlin
for
Koch.
While
the
German
school
led
by
Koch
concentrated
primarily
on
the
etiology
of
major
infectious
diseases,
the
French
group
under
Pasteur
was
involved
in
experimental
analysis
of
how
infectious
diseases
develop
in
the
animal
body
and
how
recovery
and
immunity
are
brought
about.
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By
around
1880,
it
was
recognized
that
some
animal
diseases
are
restricted
to
certain
species
of
animals.
For
example,
leprosy
and
gonorrhoea
were
found
only
in
humans.
Also,
it
was
found
that
the
diseases
such
as
smallpox,
plague
and
measles
generally
occurred
only
in
person
who
had
not
previously
had
these
diseases
and
survivors
from
such
infections
were
known
to
be
immune
to
these
diseases.
Nothing
was
however,
known
of
the
mechanisms
underlying
infection
or
immunity.
Although
basic
information
regarding
the
mechanism
of
immunity
was
not
known,
the
practice
of
active
immunization
was
first
adopted
by
Edward
Jenner
(1749-18,23).
He
had
noticed
that
milk-maids
who
developed
cow
pox
were
immune
to
small
pox.
Subsequently,
he
developed
the
concept
of
vaccination
and
was
able
to
protect
susceptible
people
against
small
pox
by
vaccinating
them
with
attenuated
cow
pox.
Around
1882,
Pasteur
had
seen
that
highly
virulent
cultures
of
the
bacteria
causing
fowl
cholera
sometimes
lost
their
infectivity
and
became
attenuated
on
long
maintenance
in
the
laboratory.
Having
heard
about
Jenner's
work
with
attenuated
pox,
he
first
inoculated
chickens
with
attenuated
fowl
cholera
bacteria
and
later
challenged
them
with
the
virulent
bacteria.
He
found
that
the
birds
inoculated
with
attenuated
cultures
were
immune
to
the
virulent
cultures.
Besides
this,
Pasteur
also
studied
and
developed
vaccine
for
rabies.
These
early
experiments
of
Jenner,
Pasteur
and
others
mark
the
beginning
of
our
understanding
of
the
basic
principles
of
active
immunization
by
attenuated
infectious
agents.
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