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Respiratory System > Respiratory Tract Infections > Flashcards

Respiratory Tract Infections Flashcards

0
Q

What are the main defences of the upper respiratory tract against infection?

A

Muco-ciliary escalator (ciliated pseudostratified columnar epithelium)

Cough/sneezing reflex

Lymphoid follicles of pharynx & tonsils, alveolar macrophages, IgA & IgG

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1
Q

What are some common organisms present in the upper respiratory tract?

A 
Normal flora: 
viridians Strep.
Neisseria spp.
Anaerobes 
Candida spp.

Transient colonisation:
Strep. pneumoniae
Strep. pyogenes
H. influenzae

Immunocompromised/long-term hospitalisation:
Pseudomonas aeruginosa
E. coli

Less common:

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2
Q

What are the possible sites of infection in the upper respiratory tract and the organisms implicated?

A 
Rhinitis (common cold) 
Pharyngitis 
Epiglottitis 
Laryngitis 
Tracheitis 
Sinusitis 
Otitis media 
Viruses: rhinovirus, coronavirus, (para)influenza, RSV 
Bacterial superinfection (virus + bacteria) common with sinusitis/otitis media -> causes mastoiditis, meningitis, brain abscesses
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3
Q

What are the possible sites of infection in the lower respiratory tract?

A

Bronchitis:
Acute (viruses & bacteria) —> may lead to pneumonia
Chronic (not primarily infective)
Pneumonia (pulmonary parenchyma)

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4
Q

What is the definition of pneumonia? What is the difference between pneumonia and pneumonitis?

A

Infection of pulmonary parenchyma with consolidation (alveoli filled with fluid produced by inflammatory cells -> heavy, stiff lung)

Distal airspaces filled with inflammatory exudate, impairing gas exchange

PNEUMONITIS = non-infective inflammatory disease

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5
Q

What are some of the common bacteria implicated in community-acquired pneumonia?

A

S. pneumoniae (elderly, co-morbidity, acute onset, high fever, pleuritic pain)

Moraxella cattarhalis (COPD)

H. influenzae (COPD)

Kleb. pneumoniae (thrombocytopenia & leucopenia)

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6
Q

What are some of the atypical bacteria implicated in community-acquired pneumonia?

A

Chlamydia spp. (contact with birds) e.g. haemophilia

Mycoplasma pneumoniae (no cell wall; young, prior antibiotics, extra-pulmonary involvement e.g. haemolysis, skin, joints)

Legionella (recent travel & exposure to contaminated aerosols; young, smokers, multi-system involvement)

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7
Q

What are some of the viruses implicated in community-acquired pneumonia?

A

(para)influenzae (give antivirals to pregannt/immunocomprimised - oseltamivir & zanamivir)

Respiratory syncytial virus (RSV)

note: patchy/diffuse ground glass opacity on CXR

Severe viral pneumonia causes necrosis/haemorrhage into lung parenchyma -> similar symptoms to adult respiratory distress syndrome

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8
Q

What are some of the bacteria implicated in hospital-acquired pneumonia? What is the definition of hospital-acquired pneumonia?

A

Pneumonia occurring 48hrs after hospital admission; especially ITU, ventilated patients, post-surgical patients (intubated, poor ventilation, immobile, aspiration, immunocompromised, antibiotics)

Gram-ve enteric bacteria

Pseudomonas

MRSA (post-viral, IV drug use)

M. tuberculosis + atypical mycobacteria

Coxiella (animal contact)

Strep. millei (dental infections; abdominal source)

Aspiration pneumonia: bacteria from GI tract enters lungs
- anaerobes, oral flora, mixed (e.g. viridians strep. + anaerobes)

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9
Q

What are some organisms implicated in pneumonia in immunocompromised patients?

A

Candida

Aspergillus

Pneumocystitis jirovecii -> pneumocystis pneumonia (PCP) -> diffuse hilar shadowing

Opportunistic viruses

Protozoa

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10
Q

What is aspiration pneumonia? What are some risks/causes?

A

Aspiration of exogenous material or endogenous secretions into the respiratory tract (own flora/environmental flora aspirated)

  • neurological dysphagia
  • epilepsy
  • alcoholics
  • drowning
  • drug overdose
  • nursing home residents
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11
Q

Compare the presentation and organisms involved in lobar and bronchopneumonia.

A

LOBAR PNEUMONIA: (S. pneumoniae)

  • confluent consolidation involving a complete lung lobe
  • community-acquired
  • acute onset
  • acute inflammatory response: exudation of fibrin-rich fluid (neutrophil & macrophage infiltration)

note: usually at base of lungs (atypical organisms implicated in upper lobes)

BRONCHOPNEUMONIA: (S. pneumoniae & H. influenzae + aspirates inc. S. aureus, anaerobes, coliforms)

  • starts in airways and spreads to adjacent alveoli and lung tissue, often in the context of pre-existing disease
  • complication of influenza/viral infection/aspiration of gastric contents, cardiac failure, COPD
  • patchy consolidation not confined by lobar architecture
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12
Q

Compare the causative organisms and complications of acute and chronic pneumonia.

A

ACUTE: test for most common bacteria

  • resolution & organisation -> fibrous scarring (if microbe is not cleared can remain latent and lead to chronic/recurrent pneumonia)
  • complications include lung abscesses, bronchiectasis, empyema

CHRONIC: test for mycobacteria, fungi, & atypical bacteria
- susceptible to recurrent pneumonia (e.g. as in cystic fibrosis patients)

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13
Q

What is whooping cough?

A

Bordetella pertussis

Transmission: droplet

Epidemic every 4yrs in older generation

Cold-like symptoms causes severe coughing for 2-3 months, which then causes whoop/vomiting

Treat with erythromycin

Vaccinate in childhood & pregnant women (does not last throughout life)

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14
Q

Define bronchiectasis.

A

Widening of the bronchi

Causes:

  • congenital
  • infection e.g. whooping cough, measles (childhood)
  • obstruction e.g. foreign object, growth
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15
Q

Define empyema.

A

Pus in pleural cavity

16
Q

What are some signs and symptoms of pneumonia?

A
  • febrile symptoms (fever, chills, sweats, rigors)
  • cough: sputum may be clear, purulent, “rust-coloured”, or haemoptysis
  • dyspnoea
  • myalgia
  • pleuritic pain
  • malaise
  • anorexia
  • vomiting
  • headache
  • diarrhoea
  • wheeze
  • bronchial breath sounds
  • crackles
  • dullness to percussion
  • reduced vocal resonance
17
Q

What are the characteristics of pleuritic pain?

A

Chest pain exacerbated by forceful breathing

+ perceived dyspnoea (due to suppressed ventilation)

note: also called pleurisy

18
Q

What are some of the important investigations for pneumonia?

A 
CXR 
O2 sats. & ABG 
FBC, WCC, platelets 
U&E, LFTs, CRP 
Sputum sample appearance (?mucoid, ?purulent, ?blood) 
Culture, Gram stain & acid fast 
PCR (viruses) 
Antigen detection (Legionella, pneumococcus - urine) 
Antibody detection (serology)
19
Q

How can samples be obtained for investigation in pneumonia?

A

Sputum

Nose/throat swabs (viral cause suspected)

Endotracheal aspirates

Broncho-alveolar lavage fluid (if cannot cough up sputum)

Open lung biopsy (if cannot cough up sputum)

20
Q

What is the management of pneumonia?

A

Depends on CURB-65 score
?confusion, high urea, high resp. rate, high BP, >65yrs
(score >2 -> hospitalisation +/- ITU)

Antibiotics:

  • amoxicillin or co-amoxiclav (note: amoxicillin resistance in E. Europe & SE Asia)
  • levofloxacin for Legionella
  • tetracyclines/macrolides for atypical organisms
  • poor response/atypical presentation -> discuss with microbiology

Prevention:

  • flu vaccine annually for high risk patients
  • pneumococcal vaccine
  • oral penicillin/erythromycin for patients at high risk of infection e.g. asplenic, dysfunctional spleen, immunodeficiency
21
Q

When should pneumonia patients be sent to the ITU?

A

Respiratory failure

Hypercapnia

Worsening metabolic acidosis

Hypotension despite fluids

22
Q

What is chronic maxillary sinusitis? How is it diagnosed? How is it treated?

A

Infection causes mucosal inflammation and oedema in the maxillary sinus

Exudate retained in maxillary sinus due to the blockage of the ostium by congested mucosa and inflammation, preventing drainage into nasal cavity

  • pain (high pressure)
  • halitosis can occur due to chronic dental disease (e.g. dental apical abscess), poor dental hygiene, anaerobic organisms in mucus

Diagnosis: plain X-ray/CT of sinuses shows opacity in maxillary sinus due to fluid

Recurrence can occur despite antibiotic treatment due to blocked drainage - may require surgical drainage of maxillary antrum & teeth extraction

23
Q

Why are asplenic patients vulnerable to bacterial pneumonia?

A

Defective alternate complement pathway & deficient in serum opsonin activity & reduced blood filtering

Vulnerable to encapsulated bacteria inc. Strep. pneumoniae

Respiratory System (12 decks)

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