00:02
In our discussion of upper
respiratory tract infections,
there’s probably none more
important than acute pharyngitis.
00:09
So I will speak to you about that.
00:12
First, let’s define it.
00:15
Acute pharyngitis would be
inflammation of the pharynx
from multiple infections and noninfectious
causes characterized by this triad:
fever, sore throat, and
pharyngeal inflammation.
00:34
In terms of the epidemiology, this
is a very, very common problem
in the course of a year.
00:42
Almost 50% of children will
have an episode of pharyngitis
and almost 20% of adults have
pharyngitis in the course of one year.
00:55
Most of the patients who have it are
between the ages of 5 and 24.
01:01
And in temperate climates, we find
most of the pharyngitis when people
tend to be indoors
winter and early spring.
01:11
And this is a very unfortunate fact
that when patients go to the doctor
with complaints of pharyngitis,
they get antibiotics far too often.
01:25
Antibiotics are not
necessary in many cases.
01:32
So what are the key elements of how these
various pathogens cause sore throat?
The exact mechanisms actually
causing the symptoms and signs
are not fully understood.
01:47
There’s been some evidence that
bradykinin, prostaglandins
act on sensory nerve endings,
but that’s not absolutely clear.
01:58
The organism that’s been
studied most extensively
and we’ll talk most extensively
about is group A streptococcus.
02:07
But actually, most
sore throats are viral
and can be caused by common cold
viruses, like the coronavirus,
but also, influenza virus, coxsackie,
or Epstein-Barr virus notorious for
causing infectious mononucleosis.
02:25
And here I’m showing you a picture of
group A streptococcal pharyngitis,
but more about that later.
02:33
Let’s talk about the pathogenesis
of pharyngitis caused
by group A strep.
02:39
This organism is notorious, it
has multiple virulence factors,
probably the most important
of which is M protein.
02:48
It’s also got a hyaluronic capsule.
02:52
And the group A strep is able to adhere
to epithelial cells of the pharynx
through things that most
people refer to as fimbriae.
03:02
Some scientists call them pili,
and in these fimbriae are fibronectin-binding
proteins and lipoteichoic acid,
and that’s how group A strep adheres
primarily to the epithelium.
03:21
And once it adheres, it’s able to
spread through pharyngeal tissue
through enzymes that can destroy tissue,
like hyaluronidase, streptokinase,
DNAses, and a variety
of exotoxins.
03:37
So this is really quite
a virulent organism.
03:42
But back to what I said earlier,
most causes of pharyngitis are
viral, 25% to 40% as a minimum,
and these include adenovirus,
rhinovirus another common cold virus,
enterovirus, and we can’t
forget influenza A and B.
04:03
But usually, influenza is a much more
serious and troublesome infection.
04:11
So they may have pharyngitis, but
they’re usually sick in many other ways
and other viruses can cause it.
04:20
Of course, group A strep is an important
cause because we have treatment for that
and it occurs in about
10% to 15% of adults,
which means that when an
adult gets a sore throat,
only about 10% to 15% of the
time is it due to group A strep.
04:41
On the other hand, when
kids get a sore throat,
we’re pushing almost a third of them
have group A strep as the cause.
04:51
Anaerobes can also cause pharyngitis,
particularly notorious is
Fusobacterium necrophorum.
04:59
We’ll have more to say about that later.
05:03
And then there are some others that
physicians must at least consider,
such as Corynebacterium diphtheriae,
but most people are immunized in developing
countries against that organism.
05:17
And we certainly need to
take a good sexual history
because occasionally Neisseria
gonorrhoeae can cause pharyngitis.
05:27
Mycoplasma pneumoniae can cause it among
young adults particularly college age
people who live in dormitory settings or
in the military barracks type settings.
05:39
And then among older folks, Chlamydophila
pneumoniae is a cause of pharyngitis.