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103 Theme 4 - Lungs > Respiratory infections and COVID-19 > Flashcards

Respiratory infections and COVID-19 Flashcards

1
Q

What bacteria cause respiratory tract infections?

A

Streptococcus pneumoniae

Mycobacterium tuberculosis

Legionella pneumophila

Mycoplasma pneumoniae

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2
Q

What coronaviruses cause respiratory infections?

A

Rhinovirus

Influenza

  • RSV
  • parainfluenza virus

Coronavirus

  • Human coronaviruses
  • SARS coronavirus 2
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3
Q

What fungi cause respiratory tract infections?

A

Aspergillus fumigatus

Pneumocystis jirovecii

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4
Q

Which part of the respiratory tract is exposed to pathogens normally?

A

Lungs constantly exposed to particulate material and microbes from upper airway

Lower airways usually devoid of conventional pathogens

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5
Q

What are the innate immunity features in the respiratory tract?

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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6
Q

What are the acquired immunity features in the respiratory tract?

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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7
Q

What is inflammation?

A

Inflammation = body’s response to insult

Acute or chronic

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8
Q

What are the macro features of inflammation?

A

Macro = redness, swelling, heat, pain and loss of function

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9
Q

What are the micro features of inflammation?

A

Micro = vasodilation, increased vascular permeability and inflammatory cell infiltration

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10
Q

What are the 5 infections of the upper respiratory tract?

A

Rhinitis

Sinusitis

Pharyngitis

Tonsillitis

Laryngitis

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11
Q

What are the 6 infections of the lower respiratory tract?

A

Bronchitis

Bronchiolitis

Pneumonia

Pulmonary tuberculosis

Pulmonary abscesses

Empyema

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12
Q

What is the difference between the 5 respiratory viruses?

A

Rhinovirus: common cold

Influenza: ‘flu’

Coronavirus: human: common cold

zoonotic: severe respiratory illness

RSV: bronchiolitis

Parainfluenza virus: croup (

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13
Q

Are viral UTRIs more common as children or adults?

A

5-7x/year in preschool children; 2-3/year in adulthood.

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14
Q

Colds account for _____% of all time lost from work for sickness

A

40%

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15
Q

Which respiratory illness has >200 viral subtypes associated?

A

Common cold

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16
Q

Which viruses cause the common cold?

A

Rhinovirus = commonest; cause 30-50%

Human coronaviruses cause about 10 to 15 percent of common colds

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17
Q

How are common colds transmissed?

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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18
Q

What is the incubation period and symptomatic period for common colds?

A

IP 2-3 days; symptoms last 3-10ds, and up to 2 weeks in 25% patients.

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19
Q

What causes the symptoms of a cold?

A

Bradykinin: intranasal administration of bradykinin causes a sore throat; it also causes nasal congestion due to vasodilation

Sneezing is mediated by stimulation of the trigeminal sensory nerves - histamine mediated

Nasal discharge (snot) changes colour with increasing numbers of neutrophils (white ->yellow->green) due to myeloperoxidase

Cough is mediated by the vagus nerve – inflammation has to extend to the larynx to trigger this; hyper-reactive response in URTI

Cytokines responsible for systemic symptoms such as fever

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20
Q

How can you tell the difference between a cold and an influenza-like illness (’flu’)?

A
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21
Q

What is influenza caused by?

A

Caused by Influenza A or B virus.

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22
Q

When does influenza spread most?

A

Occurs in outbreaks and epidemics worldwide; usually in winter season, so swaps hemispheres over the course of the year.

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23
Q

What are the features of uncomplicated influenza?

A

Incubation Period 1-4 days

Abrupt onset of fever+ cough, headache, myalgia and malaise, sore throat, nasal discharge

Acutely debilitating.

Fever 38-41; otherwise examination often unremarkable

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24
Q

What are the risk groups for complications in influenza?

A

Immunosuppression or chronic medical conditions

Pregnancy or 2 weeks postpartum

Age <2y or >65y

BMI >40

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25
Q

What are the possible complications of influenza?

A

Primary viral pneumonia

Secondary bacterial pneumonia

CNS disease

Death (estimated mortality rate among people infected with influenza in the US is about 0.13 percent)

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26
Q

What are the 3 problems a virus must solve?

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

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27
Q

How do influenza viruses enter the cell?

A

The influenza virus haemagglutinin surface protein (H) binds sialic acids on cell surface glycoproteins and glycolipids in the respiratory tract. This allows the influenza virus to enter the cell.

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28
Q

How do influenza viruses escape?

A

The neuraminidase (N) on the surface of the virus allows the virus to escape by cleaving sialic acid bonds – otherwise the escaping virions all clump together.

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29
Q

What is the benefit of the influenza virus having a segmented genome?

A

The influenza virus has a segmented genome (8 parts) so can reassort if 2 different viruses infect the same cell.

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30
Q

Complete the diagram on the lifecycle of a virus

A
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31
Q

What is antigenic drift?

A

These are small changes (or mutations) in the genes of influenza viruses that can lead to changes in the surface proteins of the virus: HA (hemagglutinin) and NA (neuraminidase).

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32
Q

What is antigenic shift?

A

Antigenic shift is an abrupt, major change in an influenza A virus, resulting in new HA and/or new HA and NA proteins in influenza viruses that infect humans.

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33
Q

What are the options for treatment and prevention of influenza?

A

Active immunisation – against haemagglutinin and neuraminidase components

Tamiflu = oseltamivir = a neuraminidase inhibitor

Hand hygiene and droplet precautions

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34
Q

What is pneumonia?

A

Pneumonia = infection of the lung parenchyma

35
Q

How does pneumonia work?

A

Alveoli full of inflammation = blocks oxygen transfer

36
Q

What are the symptoms of pneumonia?

A

Fever, breathlessness, cough, sputum production;

Hypoxia, increased respiratory rate;

Pleuritic chest pain

Sepsis

37
Q

What is the role of radiology in pneumonia?

A

Diagnosis of pneumonia requires infiltrates on a plain CXR with supporting clinical features.

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.

38
Q

What does this chest x-ray show?

A

Right upper lobe consolidation

Pneumonia

39
Q

What does this chest x-ray show?

A

Right lower lobe consolidation

Pneumonia

40
Q

What are the clasifications of pneumonia?

A

Typical versus atypical – but not very helpful, as there is no feature in an individual patient that helps distinguish between them.

Lobar versus bronchopneumonia – also not very helpful; descriptive, but doesn’t help management

Community versus hospital-acquired = much more useful, as the pathogens involved differ in their % contribution

41
Q

What are community-acquired pneumonia pathogens?

A

Streptococcus pneumoniae

Haemophilus influenzae

Mycoplasma pneumoniae

Legionella pneumophila

Staphylococcus aureus

Respiratory viruses probably responsible for ~1/3

plus Pneumocystis jirovecii in cell-mediated immunodeficiency

& Aspergillus fumigatus

42
Q

What is the commonest organism causing pneumonia?

A

Streptococcus pneumoniae

43
Q

What are the microscopic features of Streptococcus pneumoniae?

A

Gram positive cocci

44
Q

What are the risk factors for pneumonia due to Streptococcus pneumoniae

A

Alcoholics, respiratory disease, smokers, hyposplenism, chronic heart disease

HIV – 50- to 100-fold increase in invasive pneumococcal disease in HIV+

45
Q

How does Streptococcus pneumoniae cause pneumonia?

A

Acquired in nasopharynx

Asymptomatic carriage in 40-50%

smokers>non-smokers

46
Q

What is the treatment and prevention for Streptococcus pneumoniae?

A

Prevention – vaccine

Treatment – penicillin

47
Q

What is the Commonest cause of ambulatory ‘atypical pneumonia’?

A

Mycoplasma pneumoniae

48
Q

What is the typical presentation of Mycoplasma pneumoniae?

A

Classically young patient, vague constitutional upset, several weeks

Extrapulmonary symptoms very common

49
Q

Which pneumonia pathogen lacks cell walls and what is the impact of this?

A

Mycoplasma pneumoniae

resistant to penicillins

cannot grow on normal lab plates

50
Q

What is the diagnosis and treatment for Mycoplasma pneumoniae?

A

Diagnosis by PCR of throat swab (VTS)

Treatment: macrolides or tetracyclines

51
Q

How does Legionella pneumophila infections occur?

A

Can occur as sporadic infection or in outbreaks associated with a contaminated water source (consider travel and nosocomial acquisition)

52
Q

Which pneumonia pathogen is uncommon?

A

Legionella pneumophila

53
Q

What are the features of pneumonia caused by Legionella pneumophila?

A

Can cause severe, life threatening infection

54
Q

What are the risk factors for pneumonia caused by Legionella pneumophila?

A

Smoking and chronic lung disease

55
Q

What is the diagnosis and treatment for Legionella pneumophila?

A

Diagnosis

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

Treatment: macrolides or quinolones

56
Q

What is healthcare-associated pneumonia?

A

New onset at least >48 hours since admission.

Hospitalised patients become colonised with hospital bacteria

These may either be intrinsically more resistant to antibiotics, or have acquired resistance mechanisms.

57
Q

Name the pathogens which cause hospital-acquired pneumonia

A
  • Escherichia coli
  • Klebsiella pneumoniae
  • Pseudomonas aeruginosa
  • Staphylococcus aureus
  • Streptococcus spp
58
Q

What fraction of the world’s population has latent TB?

A

One quarter of the world’s population has latent TB

59
Q

Where were the majority of UK TB patients born?

A

Outside of UK

60
Q

What are the social risk factors for TB?

A
61
Q

What are the pathological features of TB?

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)

62
Q

What stains are used for TB?

A

Special stains – Ziehl-Neelsen or auramine-rhodamine

63
Q

How is TB transmitted?

A
  1. Infection is initiated by the inhalation of aerosol droplets that contain bacteria.
  2. The initial stages of infection are characterized by innate immune responses that involve the recruitment of inflammatory cells to the lung.
  3. Following bacterial 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.
  4. The recruitment of T cells, B cells, activated macrophages and other leukocytes leads to the establishment of granulomas, which can contain Mycobacterium tuberculosis
64
Q

Complete the diagram on the timeline of a TB infection

A
65
Q

What are the features of latent TB?

A

Dormant bacilli

Contained by host defences

Non-infectious

Asymptomatic

Dx by demonstrating host IR

66
Q

What are the features of dormant TB?

A

Actively replicating bacilli

May be infectious (site-dependent)

Symptomatic (site-dependent)

Dx by isolating AFBs, growing MTB or PCR positive

67
Q

What are the aims and management of TB?

A

Cure active disease

Reduce spread

Prevent reactivation

By… 1. prompt and adequate treatment;

  1. appropriate source isolation;
  2. by contact tracing
68
Q

Complete the diagram of the SARS-CoV-2 virus

A
69
Q

What are the microscopic features of the SARS-Cov-2 virus?

A

Beta coronavirus

Spike protein (S) binds ACE2 receptor on airway epithelial cells (gut, other organs)

70
Q

How is SARS-CoV-2 transmitted?

A

Likely bat in origin, to humans ?via another species

Droplet spread (+aerosol + contact)

71
Q

When was SARS-Cov-2 identified and sequenced?

A

Identified in Dec 2019, sequenced in Jan 2020

72
Q

Complete the chain of infection for COVID

A
73
Q

What are the symptoms of COVID?

A

A new, continuous dry cough;

Fever over 37.8OC;

Change or loss of sense of smell or taste

COVID-19 is an illness with a wide range of symptoms.

The frequency of nausea, vomiting, abdominal pain, headache and sore throat increased with increasing age;

but fever and runny nose became less common with increasing age. Symptoms evolve over the course of the illness.

74
Q

When does hospital admission usually occur with COVID?

A

Hospital admission is usually on days 8-10

75
Q

What is COVID-19?

A

The clinical syndrome associated with SARS-CoV-2 infection

76
Q

The spread of disease severity -

~80% of people will experience…

~15% of people will experience…

~5% of people will experience…

A

~80% have asymptomatic to moderate disease and recover without needing hospital treatment.

~15% may get severe disease including pneumonia.

~ 5% become critically unwell. This may include septic shock and/or multi-organ and respiratory failure.

77
Q

What is the fatality rate for COVID-19?

A

Overall, the infection fatality rate is estimated to be 0.9% but it varies according to age and sex. It is lower in younger people (0.5% for those 45-64 years) and higher in those over 75 years of age (11.6%).

78
Q

Who is most at risk from COVID?

A

The single greatest risk of mortality from COVID-19 is increasing age

The risk increases exponentially with age

80% of deaths have been in those aged 70 years and over,

79
Q

What are the risk factors for COVID-19?

A

Those with underlying medical problems (hypertension, IHD, obesity, diabetes, male gender) have an increased risk of severe disease.

There is clear evidence that certain Black, Asian and minority ethnic (BAME) groups have higher rates of infection, and higher rates of serious disease, morbidity and mortality from SARS-Cov-2 infection.

Societal factors, such as occupation, household size, deprivation, and access to healthcare can also increase susceptibility to COVID-19 and worsen outcomes following infection.

80
Q

What are the indicators for admission with COVID-19?

A
  • Oxygen sats <90%
  • Respiratory rate >30
  • Signs of severe respiratory distress
81
Q

What are the possible treatments for COVID-19?

A
  • High risk of thromboembolism
  • Glycemic issues – hyperglycemia, DKA
  • Acute kidney injury
  • Cardiac toxicity
  • Delirium in elderly
82
Q

What is the treatment for COVID-19?

A

Supportive care

High flow oxygen

Dexamethasone

83
Q

What are the 6 preventative measures for COVID-19?

A
  1. Personal and protective equipment
  2. Ventilation (environment)
  3. Reducing encounters
  4. Reducing contact / proximity
  5. Handwashing
  6. Immunisation

103 Theme 4 - Lungs (21 decks)

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