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0:00
Welcome to another lecture in
the series on bacterial
pathogenesis.
I'm Patrick Cleary.
I'm a Professor of
Microbiology at
the University of
Minnesota Medical School.
The focus of my lecture is
Streptococcus pyogenes,
a review of the diseases and
the molecular pathogenesis
associated with this organism.
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I'd like to start
out by giving you
a brief overview of the
genus Streptococcus.
In the 1940s and 50s,
Rebecca Lancefield sub-classified
streptococci using
polysaccharide antigens produced
by different strains of
streptococci as the antigenic
marker of different species.
She grouped streptococci
into groups.
Group A through N.
Since her work, however,
microbiologists have given
these streptococci genus
and species names.
For example,
streptococcus pyogenes
is also called group
A streptococcus.
Many of these streptococci
have two names.
They have a genus
and species name,
but they also are referred
to by their group name.
Streptococcus agalactiae or
group B streptococcus is
the cause of neonatal infections
and I'll talk about
them in a little
more detail in the next slide.
Streptococcus dysgalactiae
is a complicated collection
of different strains
of streptococci.
Human isolates have been
termed group C and
G streptococcus
and resemble
Streptococcus pyogenes
both as far as the kinds
of infections they cause
and the virulence factors
that they produce.
Their classification
is a little bit murky,
so I prefer to continue to use
the Lancefield designation of
group C and G streptococci.
The dysgalactiae species
or group also contain
animal pathogens, Streptococcus
equi is an example.
It causes sore throats
or strangles in horses.
The oral streptococci are also
a complicated collection
of species and subspecies.
One which has been studied in
some detail is
Streptococcus mutans.
It's the cause of dental caries.
Other species in the oral cavity
which seldom cause
infections, however,
can cause serious infections
if they get into
the bloodstream.
The streptococcus most
often associated with
invasive and serious infections
is Streptococcus pneumoniae.
Once again, this is a
member of the normal flora
and many of us carry this
organism in our mouth.
I'll say a little more about
this organism in
an upcoming slide.
