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Module 103, Theme 4: Physiology of the lungs and gaseous exchange. Pulmonary disorders and principles of their treatment. > Respiratory tract infection > Flashcards

Respiratory tract infection Flashcards

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1
Q

Compare symptoms of the cold to the flu.

A

Onset: cold has a slower onset than the flu.

Debilitation: Flu is more debilitating. General greater feeling of ‘illness’.

Affected sites: Cold mainly throat and nose. Flu affects everywhere.

Fever: Flu has onset of fever (greater than 38) whereas the cold does not.

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2
Q

Innate immunity in respiratory tract

A

Cilia- accompanied with mucus which removes debris and pathogen.

Alveolar macrophages:

  • Kills pathogens
  • Secrete antibacterial
  • Recruit other immune cells
  • Antigen presentation on T cells.
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3
Q

Acquired immunity in the respiratory tract

A

B + T cells: deal with intracellular pathogens.

IgA interferes with viral adherence and viral assembly.

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4
Q

The common cold

A

Caused commonly by the rhinovirus- 30-50%

More common in preschool children.

Symptoms mainly in throat and nose and have a slow onset.

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5
Q

Main pathogen that causes the common cold

A

Rhinovirus

30-50% of cases

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6
Q

Transmission of the common cold

A

Direct or indirect hand contact- individual coughing/sneezing into their hands and touch other surfaces.

Virus can remain on skin for 2 hours and for longer hours on other surfaces.

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7
Q

Incubation period of the common cold

A

2-3 days

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8
Q

Length of symptoms in individuals with the common cold

A

3-10 days commonly

Up to 2 weeks in 25% of individuals.

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9
Q

Influenza

A

Infection that causes the ‘flu’.

Virus: Influenza A or B.

Usually occurs in outbreak and epidemics- mainly in the winter season.

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10
Q

Incubation period of influenza

A

1-4 days- usually quicker onset than common cold.

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11
Q

Symptoms of influenza

A

Abrupt onset of fever: 38-41

Headache

Myalgia

Malaise

Coughs, sore throat, nasal discharge.

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12
Q

Complications of influenza

A

Can primary cause viral pneumonia.

Can cause secondary bacterial pneumonia.

CNS disease

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13
Q

Risk groups for influenza complications

A

Those with immunosuppressed or chronic conditions.

Women who are pregnant or 2 weeks postpartum.

Age: below 2, above 65

BMI> 40

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14
Q

Influenza virus receptors

A

Contains haemagglutinin surface protein (H) which binds to sialic acid receptors on respiratory tract cells.

Neuraminidase receptor allows the virus to escape the host cell by cleaving sialic acid.

The gene coding for each receptor are on different segments (of the 8) in the virus. This allows wide variation in virions.

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15
Q

Receptor on influenza that allows it to enter host cells .

A

Haemagglutinin (H)

This binds to sialic acid on the host cells in the respiratory tract- allowing it to enter the host cell.

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16
Q

Receptor on influenza that allows it to leave host cells .

A

Neuraminidase (N)

This receptor cleaves sialic acid on host cells, allow it to escape cells- prevents virons from clumping.

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17
Q

Influenza shift

A

Occurs when RNA segments are exchanged between viral strains in their secondary host.

This provides no cross-protective immunity to virus expressing new haemagglutinin.

This causes an epidemic/ outbreak- where most people are not immune.

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18
Q

Influenza drift

A

Occurs as a result of point mutation in virus.

Some neutralising antibodies are still able to bind to the virus- majority will be immune.

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19
Q

Pneumonia

A

Infection of lung parenchyma

This causes alveoli to fill with inflammation contents- pus/ debris/ pathogens

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20
Q

Pneumonia symptoms

A

Fever- above 38

Breathlessness

Cough- producing sputum

Hypoxia

Tachypnea

Pleuritic chest pain

Sepsis

21
Q

3 features in pneumonia CXR

A
  1. Consolidation
    Air bronchograms may be present
    Heart/ diaphragm borders obscured.
  2. Interstitial infiltrates
  3. Cavitation may occur.
22
Q

Community versus acquired pneumonia

A

Hospital- acquired >48+ after hospital administration

Community acquired not from hospital.

Helps to narrow down pathogenic cause.

23
Q

3 main pathogens that cause pneumonia

A

Streptococcus pneumoniae

Mycoplasma pneumoniae

Legionella pneumophila

24
Q

Streptococcus pneumoniae

A

Gram positive bacteria

Primary cause of pneumonia

Usually acquired through nasopharynx region.

Prevention- vaccine

25
Q

Risk factors of developing Step. pneumoniae pneumonia

A

Alcoholics

Respiratory disease

Smokers

Hyposplenism

HIV

26
Q

Diagnosing pneumococcal disease (Strep. pneumoniae)

A

Sputum culture- easy to grow and diagnose.

IF IN BLOOD:
There is a higher chance of mortality and other extrapulmonary disease
Occurs when alcohol intake is high
Only <1% of patients show positive result in blood.

27
Q

Mycoplasma pneumoniae

A

Bacteria that causes pneumonia- most common bacteria that causes atypical pneumonia.

Usually in young patients and lasts for several weeks

28
Q

Symptoms of Mycoplasma pneumonia

A

Non specific:
Malaise
Headache
Arthralgia

Extrapulmonary very common:

  • Skin: rashes
  • CNS: aseptic meningitis, cerebellar ataxia
  • Heart: pericarditis, myocarditis

The infection can spread bilaterally- into both lungs.

29
Q

Diagnosing Mycoplasma pneumonia

A

PCR of throat walls- VTS

Mycoplasma lacks cell wall so cannot grow in normal lab plates.

30
Q

Treating mycoplasma pneumonia

A

Due to lack of cell wall, cannot be treated with penicillin.

Drugs: macrolides or tetracyclines

31
Q

Typical pneumonia

A

Pneumonia causes by the ‘typical’ microorganisms:

  • Strep.pneumoniae
  • Haemophilus influenzae
  • Moraxella catarrhalis
32
Q

Atypical pneumonia

A

Pneumonia caused by microorganisms that are not:

  • Strep.pneumoniae
  • Haemophilus influenzae
  • Moraxella catarrhalis

Mycoplasma pneumoniae is the most common atypical bacteria that causes pneumonia.

33
Q

Legionella pneumophilia

A

A rare cause of pneumonia- accounts for 2-9% of community acquired pneumonia (CAP).

Can occurs from outbreak from contaminated water source.

Can cause severe and life-threatening infections

34
Q

Symptoms of legionella pneumophilia

A

Initially starts with a mild headache

Escalates to:
High fever
Myalgia
Dyspnoea 
Confusion
Dry cough
GI upset

Further extrapulmonary complications

35
Q

Extrapulmonary complications of Legionella pneumophila

A

Lymphopenia

Low Na

36
Q

Diagnosis of L.pneumophila

A

Not grow in culture as it requires very special conditions and takes a long time.

Urinary legionella antigen is used to diagnosis.

37
Q

Treatment of Legionella pneumophila

A

Macrolides

Quinolones

38
Q

Hospital acquired pneumonia

A

Occurs when patients get pneumonia >48 hours after admission.

This is due to patients getting colonised with hospital bacteria.

Therefore: bacteria can acquired resistance mechanism or be intrinsically resistant to antibiotic.

This causes a broader spectrum of antibiotics being used.

39
Q

Local complications of pneumonia

A

Parapneumonic effusion

Empyema- collection of pus in pleural cavity caused by microorganism

Lung abscess

Collapsed lung

Post-infection bronchiectasis

40
Q

Bronchiectasis

A

Permanent enlargement of the lung airway.

This is a complication after pneumonia infection.

41
Q

TB pathology

A

Caused by aerobic bacillus (mycobacterium tuberculosis), which divide very slowly- takes 56 days to culture

Bacillus is acid fast- AFB

Cell wall lack outer membrane- poor stain, so it weakly positive

42
Q

Special stains for TB

A

Ziehl-Neelsen

Auramine-rhodamine

43
Q

Transmission of TB

A

TB is acquired by inhaling aerosol droplets.

44
Q

Pathogenesis of TB

A

After inhaling aerosol droplet containing TB- innate immune system recognises and recruit inflammatory cells to lungs.

Bacteria spread and causes dendritic cells to present their antigens to T cells.

T cells that are antigen-specific to TB expand as a result of dendritic presentation and are recruited to the lungs.

Granulomas form as a result of recruited T, B and macrophages- forms miliary spots in CXR

45
Q

Latent TB

A

Occurs in 95% if TB infections

After TB infections and cause parenchymal + lung node caseation, TB becomes dormant.

Patients will be asymptomatic until activation

Dormant TB is reactivated and proliferate- causes disease again

46
Q

Progressive primary TB

A

Occurs after primary infection of TB the infection progresses:

Haematogenous spread
Miliary TB
Cavitation

47
Q

Healed lesion TB

A
  1. Aerosol droplet containing TB is inhaled and deposited in terminal airspaces.
  2. Macrophages ingest bacilli but bacteria replicate in endosome.
  3. Macrophage with ingested bacilli are transported to lymph node to be killed.

This forms scar/ calcification.

48
Q

Diagnosing Latent TB

A

Identify immune response to TB proteins or TB-specific antigens

Module 103, Theme 4: Physiology of the lungs and gaseous exchange. Pulmonary disorders and principles of their treatment. (16 decks)

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