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Respiratory Tract Infections: Classification

by Jeremy Brown, PhD
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    00:00 those due to pneumonia. When we are talking about lung infections, we define the infection by the site. So that means that if you have an infection of the pharynx, or the nose, or the larynx that’s what we call an upper respiratory tract infection, and that’s usually the common cold or viral infection that we've all had repeatedly in our lives. There are the occasional rarer diseases caused by bacteria, which we will mention later, diphtheria, epiglottitis for example. Then, in the lower respiratory tract you may get infections, which only affect the trachea or the bronchial tree, now they tend to be that you'll get an infection of the trachea and it will spread to the bronchi, they're not independent of each other, usually you'll get a tracheobronchitis. And again that’s often a viral infection, and again we've probably already all had those several times in our lives. That’s the acute infection of the bronchial tree. Chronic bronchial infection is largely a disease called bronchiectasis, and that’s a subject of one of the talks on airways disease. The main subject of this lecture is pneumonia, and that is an infection that's affecting the alveoli, and it’s an acute infection.

    01:10 There are a range of less acute infections of the alveoli, tuberculosis being the most common, other things will be lung abscess and some very rare infections due to fungi and unusual bacteria, and those are mentioned and discussed in the talk on tuberculosis.

    01:26 So today, we are really going to concentrate on acute pneumonia, alveolar infection, and it could be due to a virus or could be due to bacteria.

    01:37 So, pneumonia is incredibly common, it affects about 1 in 200 people each year. It’s the fourth commonest cause of death in the USA and similar data for other countries in the industrialized world, and it is actually the commonest cause of death in children under the age 5 across the developing world. As I've already mentioned the Streptococcus pneumonia is the commonest cause. Before we discuss pneumonia, I’m just briefly going to cover upper respiratory tract infections. These are incredibly common. As I've mentioned we all have had colds in our life and will get repeated colds as time goes by.

    02:13 These are mainly due to viruses: Rhinovirus, Adenovirus, various Influenza viruses, Metapneuvirus, etc. and occasionally they can be due to bacteria and the commonest will be Streptococcus pyogenes, which causes the disease that everyone calls “Strep throat”, and that’s basically a bacterial infection of the pharynx. Patients with upper respiratory tract infections presents similarly independent of what the pathogen is, sneezing, a sore throat, cough, mild systemic upset, a bit of a fever, feeling unwell, wanting to go to bed. And the treatment actually is not much, we just leave this and on people will get better most the time.

    02:47 If you have Strep. pyogenes pharyngitis then actually antibiotics would be helpful, and penicillin will be beneficial in those circumstances. There are a couple of bacterial infections of the upper respiratory tract, which are very important because they are potentially dangerous. Diphteria is a laryngitis, an infection of the larynx caused by bacterium called Corynebacterium diphtheriae. The important thing about diphtheria is that the infection forms what we call a pseudo-membrane, that's an extra layer of gunky tissue on the surface of the larynx, and that pseudo-membrane causes obstruction of the larynx, and of course the larynx is a relatively small surface area, and is where all the air that goes into your lung has to pass through, and that causes airways obstruction, and therefore, is potentially dangerous, and which is why diphtheria used to be a very common cause of death in infants.

    03:42 Epiglottitis is a rare infection of the epiglottis, as its name suggests, and that’s due to a bacteria called Haemophilus influenza, and again it causes sweating of the epiglottis, and therefore, causes upper airways obstruction and is potentially dangerous as a consequence of that. Fortunately, diphtheria can be vaccinated against is, and has become much less of a problem than it used to be in the past. So if you're talking about lower respiratory tract infections, those that occur below the larynx, affecting the trachea, the bronchi or the alveoli. In fact, most patients with lower respiratory tract infection will have the tracheobronchitis that we mentioned, that’s the bottom part of this pyramid of infection.

    04:18 And only a small portion of patients actually go on to develop the more serious form of lower respiratory tract infection, which is the pneumonia and of those with pneumonia, say about 100 people have pneumonia about 70% can be treated successfully in the community.

    04:32 You don’t need to get into hospital if you have pneumonia cause most cases is relatively mild. However, in some people it's a more severe disease, and in some people it's a very severe disease, and they end up in hospital, potentially in an intensive care, and there is a mortality risk. Probably overall for each 100 people with pneumonia, about 3 will die. So bronchitis is the first form of lower respiratory


    About the Lecture

    The lecture Respiratory Tract Infections: Classification by Jeremy Brown, PhD is from the course Infections of the Respiratory Tract.


    Included Quiz Questions

    1. Herpes simplex virus
    2. Influenza A
    3. Mycobacterium tuberculosis
    4. Streptococcus pneumoniae
    1. Chlamydia
    2. influenza virus
    3. Mycoplasma
    4. Diptheria
    5. Mycobacterium tuberculosis
    1. Pneumonia
    2. Tuberculosis
    3. Lung cancer
    4. Asthma
    5. Lung abscess
    1. Pneumonia
    2. Tuberculosis
    3. Lung cancer
    4. Asthma
    5. Lung abscess
    1. Haemophilus influenzae
    2. Streptococcus pneumoniae
    3. Staphylococcus pyogenes
    4. Moraxella catarrhalis
    5. Cornybacterium diptheriae
    1. Diptheria is best treated by penicillin.
    2. Diptheria causes pseudomembrane formation.
    3. Diptheria can cause obstruction of the laryngeal area.
    4. Diptheria is usually caused in children.
    5. Diptheria can be prevented by vaccination of the child.

    Author of lecture Respiratory Tract Infections: Classification

     Jeremy Brown, PhD

    Jeremy Brown, PhD


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