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Y2 - BRS - CVR > Respiratory Infections > Flashcards

Respiratory Infections Flashcards

1
Q

How can a cold develop into pneumonia?

A

Starts off as an upper resppiratory tract infection

Develops into a lower respiratory tract infection e.g. bronchitis, bronchiolitis

Untreated, progresses to pneumonia

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2
Q

What are the signs and symptoms for:

Upper respiratory tract infection
Lower respiratory tract infection
Pneumonia

A

Upper = coughing, sneexing, stuffy nose, sore throat, headache

Lower = phlegm, more ‘productive’ cough, wheezing, muscle aches, breathlessness, fever, fatigue

Pneumonia = chest pain, reduced oxygenation of blood, cyanosis, severe fatigue, high fever

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3
Q

What is DALY?

A

Disability-adjusted Life Year = sum of years of life lost and years lost to disability

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4
Q

Why do acute lung infections only rank 4th in global deaths but 1st in global DALYs?

A

Acute respiratory infections are seen in the elderly all over the world

But they are also seen in infants under the age of 5 in certain parts of the world i.e. Africa, South Asia = greater infant mortality from acute resp infections

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5
Q

What risk factors affect the development of pneumonia?

A

Age (<2 or >65yrs) v. important
Cigarette smoking
Excess Alcohol consumption

Contact with children <15yrs
Poverty
Overcrowding

Medications e.g. inhaled corticosteroids, immunosuppresants, proton pump inhibitors

Medical History e.g. COPD, asthma, heart disease, liver disease, DM, HIV, malignancy, complement / Ig deficiencies, risk factors for aspiration, previous pneumonia

Geographical variations, animal contact, healthcare contacts

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6
Q

What causes respiratory illnesses?

A

Mix of bacterial and viral respiratory illnesses

Leads to a mix of bronchiolitis and pneumonia

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7
Q

What are common bacterial and viral causative agents for respiratory tract infections?

A 
Bacterial:
Streptococcus pneumoniae
Myxoplasma pneumoniae
Haemophilus Influenzae
Mycobacterium tuberculosis
Viral: 
Influenza A or B virus
Respiratory Syncytial Virus
Human metapneumovirus
Human rhinovirus
Coronavirus
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8
Q

Do we always know what pathogen is causing the respiratory tract infection?

A

No

It is often a mix of bacterial and viral infections, with no singular dominant pathogen

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9
Q

Which respiratory infection causes the highest annual mortality?

A

Mycobacterium tuberculosis

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10
Q

What is the most commonly identified pathogen in individuals with respiratory illness?

A

Rhinovirus

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11
Q

How does the cause of pneumonia differ?

A

Pathogen causing the pneumonia depends usually on where the pneumonia was picked up from: i.e. community, hospital or ventilator

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12
Q

What pathogens cause community acquired pneumonia?

A

Community acquired = most common cause of pneumonia

Pathogens (bacterial):

Streptococcus pneumoniae (40-50%)
Myxoplasma pneumoniae
Staphylococcus aureus
Chlamydia pneumoniae
Haemophilus Influenzae
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13
Q

What are the features of streptococcus pneumoniae?

A

Gram-positive
Extracellular
Opportunistic pathogen

Adhesion molecules on the streptococcus pneumoniae bind to the epithelium lining of the respiratory tract = allows them to absorb nutrients from the extracellular environment

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14
Q

What pathogens cause hospital acquired pneumonia?

A 
Staphylococcus aureus
Psuedomonas aeruginosa
Klebsiella species
E. Coli
Acinetobacter spp.
Enterobacter spp.
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15
Q

What pathogens cause ventilator acquired pneumonia?

A 
Psuedomonas aeruginosa (25%)
Staphylococcus aureus(20%)
Enterobacter
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16
Q

How is ventilator acquired pneumonia reduced?

A

Give patients on ventilator antibiotics to prevent infection and pneumonia

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17
Q

What are typical bacterial pneumonias?

What are some examples of typical pneumonia causative agents?

A

More sudden onset, more serious illness

Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis

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18
Q

What are atypical bacterial pneumonias?

What are some examples of typical pneumonia causative agents?

A

Milder, often slower-growing, can be and more persistent; may be intracellular = not culturable

Mycoplasma pneumoniae, Chlamydia pneumoniae,
Legionella pneumophilia

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19
Q

Does it matter if the pneumonia is caused by typical or atypical bacteria?

A

Yes - results in different treatment regimes

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20
Q

What are the consequences of acute bacterial pneumonia?

A

Inflammation and fluid buildup in the aveolar spaces where gas exchange occurs - reduces gas exchange

Pneumonia can lead to:

  1. Lung injury –> acute respiratory distress syndrome
  2. Bacteremia —> organ infection –> organ injury / dysfunction
  3. Systemic inflammation –> pronounced inflammation and damage to the lungs
  4. Treatment itself can lead to side effects e.g. ventilators causing lung injury

These can all lead to SEPSIS and deterioration

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21
Q

What treatment options are available for bacterial pneumonia?

A
  1. Supportive Therapy:
    - Oxygen delivery (for hypoxia)
    - Fluid (for dehydration)
    - Analgesia (for pain)
  2. Antibiotics:
    - Penicillins e.g. amoxicillin - beta lactams that bind proteins in the bacterial cell wall to prevent transpeptidation and so inhibit cell wall synthesis (only effective against gram positive bacteria)
    - Macrolides e.g. clarithromycin - bind to the bacterial ribosome to prevent protein synthesis
22
Q

How does antibiotic dosage and duration differ between community and hisptial acquired, and between typical or atypical?

A

More severe the infection, the stronger the dose and the greater number of antibiotics the patient is on

5-7 days for typical community acquired
7-14 days for atypical community acquired
5-7 days for hospital acquired

23
Q

What is the key to increasing the success of antibiotics?

A

Time of administration - limit bacterial replication = greater chance of survival

Using and effective antibiotic - e.g. atypical community acquired bacteria require macrolides and penicillin is not effective

24
Q

How is pneumonia spread / caught?

A

Many of the bacteria are a part of our microbiome e.g. strep. pneumoniae, haemophilus spp, staph aureus

Some are caught from the external environment

25
Q

Define the terms:
Opportunistic pathogen
Pathobiont

A

Opportunistic Pathogen = a microbe that takes advantage of a change in conditions (e.g. immuno-suppression)

Pathobiont = a microbe that is normally commensal, but if found in the wrong environment (e.g. anatomical site) can cause pathology as that microenvironment is not adapted to that pathogen e.g. if a gastric bacteria makes its way to the respiratory tract - the bacteria is tolerated in the gut but not in the lungs

26
Q

What is latent tuberculosis (TB)?

A

Mycobacterium tuberculosis - inactive version living in the lungs that is capable of replicating but is not

1 in 4 have latent TB
Most do not develop active TB

27
Q

What are the risk factors for TB?

A 
HIV = 18-fold
Alcohol = 3.3-fold
Smoking = 1.6-fold
28
Q

What is an active mycobacterium tuberculosis (Mtb)?

A

Latent bacteria starts to reactivate

Causing proliferation of the bacteria and inflammation surrounding the bacteria

Inflammation spreads through the lungs and through the blood causing systemic inflammation / damage

29
Q

Why is TB challenging to treat?

A

Latent Mtb has very distinct microbiology (v. thick cell wall highly resistant to uptake of molecules and degradation by external environment) and so is highly resistant to the immune system

Also difficult to treat due to extremely slow replication cycle esp. in latent TB

30
Q

What is the treatment of mycobacterium tuberculosis (Mtb)?

A

Standard treatment = combination of 4 antibiotics over 6 month period

31
Q

What are the different types of virus that cause the ‘common cold’?

And how many different serotypes (distinguishable strains) are there of each?

A 
Rhinovirus - 100+
Coronaviruses - 2
Influenza viruses - 3
Parainfluenza viruses - 4
Respiratory synctial virus - 2
Adenovirus - 47
Enterovirus - 40+
32
Q

Why do respiratory viruses cause disease?

A
  1. Viruses replication, lysis and damage to epithelium leads to: loss of cilia, bacterial growth, poor barrier integrity promoting oxygen transfer, and loss of chemoreceptors
  2. Immune responses can results in cellular inflammation
  3. Local immune memory
  4. Mediator release - alter function of the respiratory tract
33
Q

What regulates which virus is most likely to cause severe disease?

Use H1N1 influenze A and H5N1 avian flu as examples:

A

H1N1 influenza A has haemogluttinin on its surface that binds to alpha2,6 sialic acids, which are found mainly in the upper but not really in the lower respiratory tract

Whereas, H5N1 avian flu has haemogglutinin on its surface that binds to alpha2,3 sialic acids, which are mainly found in the lower but not really the upper respiratory tract

The cells the virus can bind to and use as host cells for replication affect the severity of the disease the virus can cause

34
Q

How does the SARS-Cov-2 cause disease?

A

The spike (S) protein on the SARs-Cov-2 virus binds to ACE2 (angiotensin converting enzyme 2), which is mainly found in the nasal epithlium and in the type 2 pneumocytes (in the lungs)

35
Q

What increases the expression of the ACE2 receptors?

A

Upregulated in smokers - explains why smoking is a risk factor to developing disease from SARS-Cov-2

36
Q

What receptor do the human rhinoviruses bind to?

A

Majorly bind to ICAM-1
Minorly bind to low density lipoprotein family of receptors

Both primarily in the upper respiratory tract - nasopharynx

37
Q

What receptor do respiratory syncytial viruses (RSV) bind to?

A

F and G proteins on the RSV bind to glycosaminoglycans in receptors such as IGFR1 and nucleolin

Found in all parts of the respiratory tract

38
Q

How does the influenza A virus and respiratory syncytial virus (RSV) differ?

A

Influenza A =
No re-infection by same strain
Imperfect vaccines - annual vaccination required, vaccine-induced immunity, homotypic immunity

RSV =
Recurrent re-infection with similar / same strain
No vaccine - poor immunogenicity, vaccine-enhanced disease, very active research field

39
Q

Why do same viral strains cause different outcomes in patients?

A

Highly pathogenic strains are usually zoonotic due to absence of immunity

Immune deficiencies

Predisposing illnesses / conditions

40
Q

What are interferons?

A

Directly produced by infected cells or by immune cells that can sense viral proteins

They are a family of cytokines that ‘interfere’ with viral infection in vitro

3 groups: type I (IFNalphas / IFNbetas), type II (IFNgamma), type III (IFNlamda)

41
Q

How does RSV affect infants?

A

RSV = leading cause of bronchiolitis in infants and so leading cause of infant hospitalisation in developed worlds

42
Q

What are the risk factors for infants getting ill from RSV?

A

Premature birth

Congital heart and lung disease

43
Q

How does RSV present in infants clinically?

A 
Chest wall retractions 
Nasal flaring
Prolonged expiration
Wheezing
Coughing
Hypoxemia
Cyanosis 
Bronchiole obstructions - typical of bronchiolitis
44
Q

How does age change the likeliness and type of viral respiratory infections a person gets?

A

Young and older individuals are at significant risk to RSV

Adults and older children tend to only get upper respiratory tract infections - milder

Young - bronchiolitis

Older children are the spreaders - infectious

Caring adults - repeated colds, rarely severe, transmitters

Old and infirm = major cause of progressive lung disease and winter deaths

45
Q

What are the treatment options for respiratory viral infections?

A

Supportive:
Oxygen therapy

Preventative:
Vaccines

Anti-virals

Monoclonal antibodies (mainly prophylactic)

46
Q

What are the similarities in RSV and influenza symptoms?

A

Primarily upper respiratory tract infections with some lower respiratory tract infections

47
Q

What are the differences between RSV and influenza symptoms and viral load?

A

Emergence and peak of influenza symptoms faster than RSV

Faster viral replication of the influenza than RSV - therefore peak viral load earlier than RSV

Influenza = pre-selected for seronegativity (i.e. this person must not have encountered ths strain before)

RSV = not pre-selected for seronegativity (same strain can reinfect)

48
Q

Why does RSV not require pre-selected seronegativity?

A

RSV antibodies produced from infection wane quickly

Unlike for influenza, which stays around for longer

This allows for re-infection

49
Q

What other viruses display no need for pre-selected seronegativity?

A

Coronaviruses

Metapneumoviruses

50
Q

What is the interplay between viral and bacterial infections?

A

Common for co-infections: i.e. both, viral and bacterial infections, within an individual

After viral infections, bacterial burdens also increase - espeiclally in smokers and COPD patients

Y2 - BRS - CVR (21 decks)

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