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Hello, everyone. My name
is Dr. Sarah Fouch.
Welcome to this short
recording where we
will be considering
group B streptococci.
We will think about the
clinical conditions that
this organism is associated
with, and we will
also think about the
virulence factors that help
this organism to be
associated with the
clinical conditions.
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Let's think about
group B streptococci,
and these are gram
positive cocci.
We will isolate
them on blood agar
because they require a
nutritionally rich media,
and when they grow,
they will appear as
buttery-like colonies.
When we compare the
haemolysis patterns
between group A and
group B streptococci,
both of these organisms produce
beta-haemolysis so we will
have complete haemolysis
of the red blood cells.
But group A
streptococci will have
quite a large zone
of haemolysis.
In comparison, group B has
quite a small zone
of beta-haemolysis.
We are able to type group B
streptococci and we will use
the group-specific antigens
that are expressed
on the cell wall.
Again, we can do this
through grouping
agglutination investigations.
There are 10 serotypes of
group B streptococci based
on their capsular
polysaccharides.
But the interesting thing about
group B streptococci is
although it has a range
of virulence factors,
it doesn't tend to cause
as many infections in comparison
to group A streptococci.
When we think about the enzymes
that this organism can produce,
we can use various enzymes
for identification.
But again, the group
B streptococci
does not tend to
use the enzymes for
pathogenesis because
we do not see
many of these in quite
nasty infections.
When we think about
group B streptococci,
as with other organisms,
there are areas of
the body where we
will find this as normal flora.
We tend to find group B
streptococci colonising
our lower
gastrointestinal system
and also our genital
urinary system.
