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T2: Theme 4: Lungs > Lecture 9: Resp tract infections > Flashcards

Lecture 9: Resp tract infections Flashcards

1
Q

What are some features of innate immunity?

A

Cilia – mucociliary escalator removing debris and pathogens

Alveolar macrophages:

  • secrete antimicrobials
  • engulf and kill pathogens
  • recruit other immune cells
  • process and present antigens to T cells
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2
Q

What are some features of acquired immunity?

A

B cell/T cell responses- essential for intracellular pathogens, such as mycobacteria, viruses and fungi

IgA secreted by plasma cells interferes with adherence and viral assembly

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3
Q

What are the macro responses to infection and inflammation?

A 
Redness
Swelling
Heat
Pain 
Loss of function
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4
Q

What are the micro responses to infection and inflammation?

A

Vasodilation

Increased vascular permeability

Inflammatory cell infiltration

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5
Q

How many colds do preschool children get per year?

A

5-7

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6
Q

How many colds do adults get per year?

A

2-3

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7
Q

What % of all time lost from work is accounted for by colds?

A

40%

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8
Q

How many viral subtypes are associated with colds?

A

> 200

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9
Q

What % of colds are caused by rhinovirus?

A

30-50% (most common cause)

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10
Q

What % of colds are caused by human coronaviruses?

A

10-15%

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11
Q

What is the form of transmission for viral URTIs?

A

Hand contact: virus remains viable for up to 2 hours on skin or several hours on surfaces

Droplet transmission from sneezing / coughing / breathing

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12
Q

What is the incubation period of the common cold?

A

2-3 days

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13
Q

How long do symptoms of the common cold last?

A

3-10ds, and up to 2 weeks in 25% patients

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14
Q

What causes intranasal a sore throat and nasal congestion due to vasodilation?

A

Bradykinin

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15
Q

What causes sneezing, mediated by stimulation of the trigeminal sensory nerves?

A

Histamine

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16
Q

What causes nasal discharge (snot) to change colour with increasing numbers of neutrophils?

A

Myeloperoxidase

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17
Q

What causes a cough?

A

The vagus nerve – inflammation has to extend to the larynx to trigger this; hyper-reactive response in URTI

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18
Q

What are the key features of a cold?

A

Appears gradually

Affects mainly your nose and throat (coryza)

Makes you feel unwell but you’re okay to carry on as normal – for example, go to work

Usually no fever

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19
Q

What are the key features of the flu?

A

Appears quickly within a few hours

Affects more than just your nose and throat

Makes you feel exhausted and too unwell to carry on as normal

High fevers

May have lower resp tract features

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20
Q

What is the incubation period of the flu?

A

1-4 days

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21
Q

What are the symptoms of the flu?

A

Abrupt onset of fever+

cough, headache, myalgia and malaise, sore throat, nasal discharge

Acutely debilitating.

Fever 38-41OC; otherwise examination often unremarkable

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22
Q

What are the risk factors for complications of the flu?

A

Immunosuppression or chronic medical conditions

Pregnancy or 2 weeks postpartum

Age <2y or >65y

BMI >40

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23
Q

What are the complications of the flu?

A

Primary viral pneumonia

Secondary bacterial pneumonia

CNS disease

Death (estimated mortality rateamong people infected withinfluenzain the US is about 0.13percent)

24
Q

What are the 3 problems a virus must solve to be successful?

A

It must know how to replicate inside a cell

It must move from one infected cell to a new cell (and a new host) in order to persist in nature

It must develop mechanisms to evade host defences

25
Q

What is haemagglutinin?

A

Influenza surface protein that binds sialic acids on cell surface glycoproteins and glycolipids in the respiratory tract.

26
Q

What is neuraminidase?

A

Influenza surface protein that allows the virus to escape by cleaving sialic acid bonds – otherwise the escaping virions all clump together

27
Q

What is distinctive about the influenza virus genome?

A

Segmented genome (8 parts) so can reassort if 2 different viruses infect the same cell

28
Q

How many segments are there to the influenza virus genome?

A

8

29
Q

What is viral drift?

A

RNA has no proof reading mechanism so accumulates mutations

30
Q

What is viral shift?

A

Undergoing drift but then experience a large mutation (entire section of genome is changing)

31
Q

What are the options for treatment and prevention of influenza?

A

Active immunisation - against H and N components

Tamiflu = a neuaminidase inhibitor

Hand hygiene and droplet precautions

32
Q

What is pneumonia?

A

Infection of the lung parenchyma

33
Q

What are the signs and symptoms of pneumonia?

A

Fever
Breathlessness
Cough
Sputum production

Hypoxia
Increased respiratory rate

Pleuritic chest pain
Sepsis

34
Q

What would be seen on the CXR of someone with pneumonia?

A

Consolidation - alveoli and bronchioles completely filled with inflammatory debris / pus / pathogens

Heart borders or diaphragm obscured due to loss of solid-gas interface

Air bronchograms - air in larger bronchi outlined by surrounding consolidation

35
Q

What are the CAP pathogens?

A

Streptococcus pneumoniae

Haemophilus influenzae

Mycoplasma pneumoniae

Legionella pneumophila

Staphylococcus aureus

36
Q

What are the risk factors for S.pneumoniae infection?

A 
Alcoholics
Respiratory disease
Smokers
Hyposplenism
Chronic heart disease
HIV
37
Q

What pathogen is the most common cause of CAP?

A

S.pneumoniae

38
Q

What are the features of S.pneumoniae?

A

Gram positive cocci

Acquired in nasopharynx

Asymptomatic carriage in 40-50%
smokers>non-smokers

Prevention – vaccine

Treatment – penicillin

39
Q

What are the features of M.pneumoniae?

A

Classically young patient, vague constitutional upset, several weeks

Extrapulmonary symptoms very common

Lacks cell wall

  • resistant to penicillins
  • cannot grow on normal lab plates

Diagnosis by PCR of throat swab (VTS)

Treatment: macrolides or tetracyclines

40
Q

Which organism is the most common cause of ambulatory ‘atypical pneumonia’?

A

M.pneumoniae

41
Q

What are the features of L.pneumonophila?

A

Sporadic infection or in outbreaks associated with a contaminated water source

Uncommon

Can cause severe, life threatening infection

RFs= smoking and chronic lung disease

Diagnosis
Don’t grow on routine culture – need special conditions, and longer
Urinary legionella antigen

Treatment: macrolides or quinolones

42
Q

What are the risk factors for L.pneumonophila?

A

Smoking and chronic lung disease

43
Q

What is HAP?

A

Definitions vary - new onset at least >48 hours since admission

Hospitalised patients become colonised
with hospital bacteria

May either be intrinsically more resistant to antibiotics, or have acquired resistance mechanisms

Broader spectrum antibiotics are used empirically

44
Q

How much of the worlds population has latent TB?

A

One quarter

45
Q

What % of UK TB cases were born outside the UK?

A

71%

rates 13x higher than if born in the UK

46
Q

What % of people with TB have a social risk factor?

A

12%

47
Q

What % of people with TB are co-infected with HIV?

A

2.8%

48
Q

What are the features of TB pathogen?

A

Aerobic bacillus

Divides every 16-20 hours (slow) – lab extends culture to 56 days

Cell wall, but lacks phospholipid outer membrane
Does not stain strongly with Gram stain (weakly positive)
Retains stains after treatment with acids

Referred to as acid fast bacillus (AFB)

49
Q

What are the special strain required in TB?

A

Ziehl-Neelsen or auramine-rhodamine

50
Q

What is the pattern of TB infection?

A

Initiated by the inhalation of aerosol droplets that contain bacteria

The initial stages of infection characterised by innate immune responses - involve the recruitment of inflammatory cells to the lung

Dissemination to the draining lymph node, dendritic cell presentation of bacterial antigens leads to T cell priming and triggers an expansion of antigen-specific T cells, which are recruited to the lung

The recruitment of T cells, B cells, activated macrophages and other leukocytes leads to the establishment of granulomas

51
Q

What % of infections become progressive primary TB?

A

5%

52
Q

What % of infections become latent TB?

A

95%

53
Q

What % of latent infections reactivate?

A

5%

20x higher if HIV or transplant; 2-3x higher if IVDU, diabetes, smoker

54
Q

What are the features of latent TB?

A

Dormant bacilli

Contained by host defences

Non-infectious

Asymptomatic

Dx by demonstrating host IR

55
Q

What are the features of active TB?

A

Actively replicating bacilli

May be infectious (site-dependent)

Symptomatic (site-dependent)

Dx by isolating AFBs, growing MTB or PCR positive

T2: Theme 4: Lungs (16 decks)

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