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respiratory > Lower respiratory tract infections > Flashcards

Lower respiratory tract infections Flashcards

1
Q

What are the common microorganisms of the respiratory tract?

A
  • Viridans streptococci
  • Neisseria spp
  • Anaerobes candida spp
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2
Q

What are the less common microorganisms of the respiratory tract?

A
  • Streptococcus pneumoniae
  • Streptococcus pyogenes
  • Haemophilus influenzae
  • Others include pseudomonas, Escherichia coli
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3
Q

Why are the lungs not sterile?

A
  • Normal alveolar microbiota
  • Aspiration
  • Blood stream spread
  • Direct spread
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4
Q

What are the defences of the respiratory tract?

A
  • Muco-ciliary clearance mechanisms
  • Nasal hairs
  • Ciliated columnar epithelium of respiratory tract
  • Cough and sneezing reflex
  • Respiratory mucosal immune system: lymphoid follicles of pharynx and tonsils, alveolar macrophages, secretory IgA and IgG
  • Alveolar microbiota
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5
Q

What is the course of a typical respiratory infection inside the lungs?

A
  1. Alveolar macrophage fails to stop pathogen
  2. Cytokines to recruit more macrophages
  3. inflammation = increased permeability
  4. More WBCs/proteins (neutrophils/lymphocytes/antibodies to aid macrophages)
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6
Q

What is the course of a typical respiratory infection outside the lungs?

A
  1. Inflammatory mediators (cytokines/chemokines) into systemic circulation
  2. This itself is physiological - activates bone marrow/more cardiac output/raised body temp
  3. Dysregulation - signs of tissue injury/organ injury
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7
Q

What causes dysregulation?

A
  • Pathogen
  • Host factors
  • Drugs
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8
Q

What is the virulence of chlamydia pneumoniae?

A
  • Ciliostatic factor (cilia don’t function properly)
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9
Q

What is the virulence of mycoplasma pneumoniae?

A
  • Shear off cilia
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10
Q

What is the virulence of influenza virus?

A
  • Reduces mucus velocity (up to 12 weeks post infection)
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11
Q

What is the virulence of strep pneumoniae/Neisseria meningitides?

A
  • Split immunoglobin (IgA)
  • Immunoglobins can’t destroy pathogens
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12
Q

What is the virulence of pneumococcus?

A
  • Pneumococcus - capsule inhibits phagocytosis (pneumolysin)
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13
Q

What is the virulence factor of mycobacterium/nocardia/legionella?

A
  • Resistant to phagocytosis (intracellular survival)
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14
Q

Which host factors make people more vulnerable to lower respiratory tract infections?

A
  • Age >65
  • Lifestyle (smoking, alcohol, drugs)
  • Chronic lung diseases (bronchiectasis, cystic fibrosis)
  • Aspiration
  • Immunocompromised
  • Metabolic (malnutrition, hypoxaemia, acidosis)
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15
Q

Which drugs make a person more susceptible to lower respiratory tract infections?

A
  • Antacids (PPI/H2 antagonists)
  • PPI increases risk for pneumonia
  • H2 antagonist causes myelosuppression
  • Antipsychotics
  • ACE-inhibitors
  • Glucocorticoids
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16
Q

What are some common upper respiratory tract infections?

A
  • Rhinitis
  • Pharyngitis
  • Epiglottitis
  • Laryngitis
  • Tracheitis
  • Sinusitis
  • Otitis media
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17
Q

Which organisms are most commonly responsible for upper respiratory tract infections?

A
  • Viruses
  • Rhinovirus, coronavirus, influenza/parainfluenza, RSV
  • Bacterial super-infection common with sinusitis and otitis media - can lead to mastoiditis, meningitis, brain abscess
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18
Q

What is acute bronchitis?

A
  • Inflammation of medium sized airways
  • Mainly in smokers
  • Cough, fever, increased sputum production, increased shortness of breath
  • Normal CXR
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19
Q

What organisms cause acute bronchitis?

A
  • Viruses
  • S. pneumoniae
  • H. influenzae
  • M. catarrhalis
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20
Q

How is acute bronchitis treated?

A
  • Bronchodilation
  • Physiotherapy
  • Antibiotics
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21
Q

What is chronic bronchitis?

A
  • Not primarily infective
  • Exacerbations have been associated with many organisms
  • Role of infection remains controversial
22
Q

What are the definitions of LRTI?

A
  • Community acquired pneumonia (CAP) - outside healthcare setting
  • Hospital acquired pneumonia (HAP) - 48 hours post admission
  • Ventilated acquired pneumonia (VAP) - 48 hours post intubation
23
Q

What is the pathology of LRTI?

A
  • Acute inflammatory response
  • Exudation of fibrin-rich fluid
  • Neutrophil infiltration
  • Macrophage infiltration
24
Q

Outline the microbiology of community acquired pneumonia?

A
  • No microbiological ID made in most cases
  • True prevalence difficult to establish due to use of indirect methods/mixed infections
  • Typical and atypical organisms
25
Q

What are the typical organisms that cause community acquired pneumonia?

A
  • Strep. pneumoniae
  • Haemophilus influenzae
  • Moraxella catarrhalis
  • RSV
  • Rhinovirus
  • Influenza
26
Q

What are the atypical organisms that cause community acquired pneumonia?

A
  • Mycoplasma (commonest)
  • Legionella - contaminated water sources
  • Chlamydophila pneumoniae
27
Q

How is CAP diagnosed?

A
  • Cough +/- sputum/ dyspnoea/ pleurisy/ fever/ tachycardia/ crackles/ bronchial breathing
  • Imaging - consolidations/ infiltrates/ cavitations
28
Q

When do you admit a patient with CAP?

A
  • CURB-65
  • Confusion
  • Urea >7 mmol/l
  • Resp rate >30
  • BP <90 systolic <60 diastolic
  • > 65 years
29
Q

What investigations should be carried out if a patient has CAP?

A
  • FBC
  • Urea and electrolytes
  • CRP
  • ABG
  • CXR
30
Q

Which microbiological investigations should be done in a patient with CAP?

A
  • Sputum/induced sputum
  • Blood culture
  • Broncho Alveolar Lavage fluid
  • Nose and throat swabs
  • Urine antigen test (legionella/pneumococcus)
  • Serum antibody test
31
Q

How is a patient with mild CAP managed?

A
  • Treat empirically
32
Q

How is a patient with moderate CAP managed?

A
  • Blood cultures/sputum culture
  • Urinary streptococcal antigen
  • Legionella
  • PCR/viral screen
33
Q

How is a patient with severe CAP managed?

A
  • Moderate + bronchoscopic specimens
34
Q

What are some differential diagnoses for CAP?

A

Heart failure + pulmonary oedema
- Pulmonary embolism
- Atelectasis
- Aspiration/chemical pneumonitis
- Drug reactions
- Lung cancer

35
Q

How is CAP treated?

A
  • Principles of antibiotic treatment
  • Empirical regimes can differ depending on hospital/allergy status/comorbidities
  • General approach 5-7 days for mild CAP
  • 7-10 days for severe CAP
36
Q

How is mild-moderate CAP treated in UHL?

A
  • Amoxicillin
  • Or doxycycline or erythromycin/clarithromycin
37
Q

How is moderate-severe CAP treated in UHL?

A
  • Needing hospital admission
  • Co-amoxiclav and clarithromycin/doxycycline
38
Q

What are the complications of CAP?

A
  • Initial infection progression - empyema/ lung abscess/ bacteraemia
39
Q

What might lead to non-resolving CAP?

A
  • Delayed clinical response
  • Closed space infections
  • Bronchial obstruction e.g. tumour
  • Subacute, chronic CAP (TB/fungal)
  • Incorrect initial diagnosis
  • All these factors delay progression of treatment
40
Q

What is the aetiology of hospital acquired pneumonia?

A
  • Staphylococcus aureus
  • MRSA
  • Enterobacteriaceae (E.coli and Klebsiella spp)
  • Pseudomonas SPP
  • Fungi (Candida)
41
Q

How is hospital acquired pneumonia managed?

A
  • Cover Staph aureus and gram negative enteric bacilli (e.g. Klebsiella) + typical/atypical pathogens - give co-amoxiclav
  • If pseudomonas risk give antipseudomonal beta lactam (meropenem) or anti-pseudomonal fluoroquinolone (ciprofloxacin)
  • If MRSA risk give Vancomycin/Linezolid
42
Q

What is the first line treatment for hospital-acquired pneumonia?

A
  • Co-amoxiclav
43
Q

What is the second-line treatment for hospital-acquired pneumonia?

A
  • Piperacillin/tazobactam
  • Meropenem
44
Q

What causes aspiration pneumonia?

A
  • Aspiration of exogenous material or endogenous secretions into respiratory tract
45
Q

Which patients are susceptible to aspiration pneumonia?

A
  • Patients with neurological dysphagia (strokes)
  • Epilepsy
  • Alcoholics
  • Drowning
  • Nursing home residents
  • Drug overdose
46
Q

How is aspiration pneumonia treated?

A
  • Moderate to severe is treated with co-amoxiclav
47
Q

Which organisms can cause LRTI in patients with HIV?

A
  • Pneumocystis jirovecci
  • TB
  • Atypical mycobacteria
48
Q

Which organisms can cause LRTI in patients with neutropenia?

A
  • Aspergillus spp
49
Q

Which organisms can cause LRTI in patients with bone marrow transplant?

A
  • Cytomegalovirus
50
Q

Which organisms can cause LRTI in patients with splenectomy?

A
  • Encapsulated organisms e.g. S. pneumoniae, H. influenzae
51
Q

How do we prevent LRTI?

A
  • Immunisation - flu vaccine annually, pneumococcal vaccine every 5 years
  • Chemoprophylaxis - oral abx, smoking advice

respiratory (21 decks)

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