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Acute Pharyngitis: Definition and Epidemiology

by John Fisher, MD
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    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.


    About the Lecture

    The lecture Acute Pharyngitis: Definition and Epidemiology by John Fisher, MD is from the course Upper Respiratory Infections. It contains the following chapters:

    • Acute Pharyngitis – Definition and Epidemiology
    • Acute Pharyngitis – Pathology
    • Microbiology

    Included Quiz Questions

    1. Fever, sore throat, and pharyngeal inflammation
    2. Fever, cough, lymphadenitis
    3. Hoarseness, cough, tonsillar exudates
    4. Sore throat, lymphadenitis, cough
    5. Cough, neck stiffness, sore throat
    1. Children ages 5-15
    2. College age students ages 18-24
    3. Adults ages 25-34
    4. Adults ages 35-65
    5. Elderly ages 75-80
    1. Antigen 85 complex bind fibronectin and help wall off the bacteria from the immune system.
    2. M-protein on cell wall allows heat and acid resistance while also offering resistance to phagocytosis.
    3. Hyaluronic acid capsule mimics human connective tissue and goes unrecognized by the immune system allowing avoidance of phagocytosis.
    4. Exotoxins and streptokinase allow spread of the bacteria through pharyngeal tissue.
    5. Fimbrea allow adherence to pharyngeal epithelial cells.
    1. Viruses
    2. Group A streptococci species
    3. Anaerobic bacteria
    4. Sexually transmitted pathogens
    5. Mycobacterium species

    Author of lecture Acute Pharyngitis: Definition and Epidemiology

     John Fisher, MD

    John Fisher, MD


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    By Rodrigo C. on 08. April 2018 for Acute Pharyngitis: Definition and Epidemiology

    I usually dislike older professors, but he explains very objectively and up to date.