So, turning now to how
do you actually diagnose
group A streptococcal pharyngitis.
Well, since the 1960s, physicians in
primary care have been employing
the Centor criteria and they
have been modified as follows:
It’s actually a scoring system to
help a physician determine whether
to get a throat culture and
whether to use antibiotics.
So if the patient is from
3 to 14 years of age,
then as you can remember, group A strep is
likely, so they get one point for that.
If they’re 15 to 44,
it’s sort of comme ci, comme ça,
they don’t really get a point.
If they’re over 45 years of age,
then of course group A strep
becomes less and less common
and you take away a point,
they get a minus one.
If on exam you find the
exudate or swollen tonsils,
you give them a point.
If they have tender or swollen
anterior cervical nodes,
they get another point.
If they have fever more than
38, they get another point.
And remember this, if
they do not have a cough,
they get a point,
but if they have a cough
present they get nothing.
So how do you use
this scoring system?
If their added up score
is minus one or one,
their risk of group A
strep is less than 10%
so they should get no antibiotic
and no throat culture.
We could save a lot of money
and save a lot of allergic
reactions if we would follow that.
If they have a score of two or three,
their risk of strep is between 15% and
32%, still pretty low, but possible,
so you get a throat culture,
but you wouldn’t give antibiotics
until you found the results
of the throat culture.
And if it’s group A strep,
you then treat them.
You still have some time, you
really have up to ten days
to prevent the sequelae
of group A strep,
so you can wait for the culture.
If they have a score of
four or five, their risk
of group A strep is not
100% by any means,
it’s only 56%.
You would certainly then go ahead
and either do one of the rapid
strep screens or culture
and give antibiotics
And I want to emphasize the
of the Infectious Disease
Society of America.
Empiric treatment is no longer recommended
just on the basis
of symptoms alone.
And the other thing about antibiotics,
let’s say a patient has had
three days of a sore throat
and it’s caused by group A strep.
If you give antibiotics
after three or four days,
the antibiotics don’t do
anything for the symptoms,
so you’re not going to hasten
the resolution of the symptoms.
Yes, you will eradicate
strep from the throat,
but you have to really --
To get any resolution of symptoms,
you’ve got to start antibiotics
within the first 24 hours ideally.
So there’s no rush if the patients
had several days of symptoms,
you can wait to get the culture,
and you can wait up to ten
days to prevent the sequelae.
A throat culture is very sensitive
and very specific for group A strep.
The microbiologists deal with
this organism all the time
and they can recognize it quickly.
There are rapid antigen detecting systems.
They have a decent
sensitivity from 70% to 90%,
not as good as culture, but their specificity
is about the same as the culture.
And here you’re showing group
A strep growing on blood agar
and there’s a zone of inhibition around
a bacitracin disk in most cultures,
not particularly shown in this one,
but you can see the beta-hemolysis.
So the goals of treatment then for
group A streptococcal infection,
and really that’s the main
one we’re focusing on,
is resolution of symptoms and you
need to start early as I mentioned.
This also is a contagious disease,
so the earlier you start, the less
contagious the patient will be.
And if you can start within ten days you
can reduce the risk of complications.
So what is the treatment?
Well, it’s my favorite
and in the form of oral penicillin it
would be penicillin V or amoxicillin.
And we generally use a ten-day course
because that’s generally required to
get rid of strep from the pharynx.
Remember, amoxicillin given to somebody
with infectious mono could cause a rash.
If a patient has a
then we prescribe erythromycin or
a first generation cephalosporin.
And there are intramuscular
regimens in patients
that really can’t take oral
medication for some reason,
you can give them a dose of
long-acting benzathine penicillin G
dosing according to their kilogram weight.
If they do have that dreaded anaerobic
infection Fusobacterium necrophorum,
we’ve got to use something that
is very good for anaerobes
and we will probably hospitalize these
patients because many of them are sick.
And it’s recommended that they
Now, the sulbactam is a
it’s what you call a suicide
It will remove all of the beta-lactamase
produced by this organism
out of the system so that ampicillin,
which it’s attached to, can
go do its thing on the bug.
Many people recommend that you add
metronidazole for extra anaerobic coverage
because it tends to penetrate clots.
I’m not certain whether you
absolutely need to use metronidazole,
but that’s what’s recommended.
For Corynebacterium diphtheriae,
you can remove the organism in somebody
with active diphtheria with penicillin.
But to actually get rid of
somebody who’s simply colonized,
penicillin won’t work,
a macrolide is needed.
So we talked about the complications that
we’re trying to prevent and these are they.
A peritonsillar abscess doesn’t have
to be caused only by Fusobacterium,
but can be caused
by group A strep.
You can have these dreaded
parapharyngeal space infections,
which can involve the dangerous
areas of the head and neck.
Lymphadenitis, sinusitis, and
otitis media can result,
and mastoiditis in very
serious complicated otitis.
Necrotizing fasciitis is pretty
rare, and so in this case,
we would be talking about necrotizing
fasciitis of the soft tissues of the neck.
group A strep can produce
the toxic shock syndrome
which is characterized by diffuse
erythema of the skin with desquamation,
hypotension, and it can result
in multi-organ failure,
and this is caused by a cytokine storm,
which the organism can result in
liberating from phagocytic cells.
There are some non-suppurative
complications, as well.
The most dreaded of course is acute rheumatic
fever and rheumatic heart disease.
And back in the days before
antibiotics were available,
this was a very common problem.
Because group A strep was
common, we couldn’t treat that.
There were no antibiotics, so we
looked at a lot of the complications.
which is fortunately not
so common, is that of
And here I’m showing, on
the left hand picture,
what a normal glomerulus looks like,
a tuft of glomerular
And I think you can see how busy
the glomerulus is in acute
glomerulonephritis and how cellular it is.
What you’re really looking
at is neutrophils
that have responded to antibodies
that are located in the glomerulus,
and they’re causing essentially
destruction of that glomerulus.
And this brings me to the end of
my discussion about pharyngitis.
I hope that it’s
been helpful to you.