4. LRTI

Question 1

What are acute LRTI?

Answer 1

• pneumonia
• bronchitis
• bronchiolitis
• legionnaires’ disease
• whooping cough

Question 2

What are chronic LRTI?

Answer 2

• tuberculosis
• aspergillosis
• cystic fibrosis

Question 3

What is pneumonia?

Answer 3

• An acute LRTI associated with recently developed radiological signs.
• Infection of lungs due to bacteria, viruses and fungi.
• Can be present with typical or atypical symptoms

Question 4

What is the classification of pneumonia?

Answer 4

• Community-acquired diagnosis
• Hospital-acquired diagnosis
• Aspiration pneumonia
• Recurrent pneumonia

Question 5

What is CAP?

Answer 5

• mainly seasonal: autumn/winter
• CAP is diagnosed in 5-12% of patients presenting to their GP with symptoms of LRTI

Question 6

What are the signs and symptoms of typical pneumonia?

Answer 6

(predominantly respiratory and common in elderly)
- signs: cough, cyanosis, tachypnoea, tachycardia
- symptoms: fever, muscle aches, shakes/rigors, dyspnoea, sputum production

Question 7

Microorganisms associated with typical CAP?

Answer 7

Streptococcus Pneumoniae
- less common:
Haemophilus influenzae
Staphylococcus aureus CF
Pseudomonas aeruginosa CF

Question 8

What are the signs and symptoms of atypical pneumonia?

Answer 8

(predominantly non-respiratory)
- signs: rash, cyanosis, tachypnoea, tachycardia, dry cough
- symptoms: headache, confusion, diarrhoea, incontinence, no sputum

Question 9

What are the microorganisms associated with atypical CAP?

Answer 9

most common:
- mycoplasma pneumoniae
less common:
- leigionella pneumophila
- chlamydophila psittaci
- chlamydophila pneumoniae

Question 10

What is the radiological appearance of typical pneumonia?

Answer 10

widespread consolidation

Question 11

What is the radiological appearance of atypical pneumonia?

Answer 11

patchy consolidation

Question 12

What are the CAP risk factors?

Answer 12

• elderly/young (A/T)
• smokers/ travel abroad (A)
• alcoholics/vagrants (T)
• contacts with animals/ birds (A)
• underlying illness (T)

Question 13

What is HAP?

Answer 13

• 3rd most common hospital acquired infection
• patients can be typical or atypical

Question 14

What are the risk factors for HAP?

Answer 14

• ventilatory support
• immunosuppression: organ transplantation
• immobility and vomiting

Question 15

What is the treatment of pneumonia?

Answer 15

• uncomplicated CAP: amoxicillin or erythromycin
• severe CAP: cefuroxime and erythromycin
• atypical pneumonia: erythromycin
• HAP: cefotaxime and gentamicin

Question 16

What is the mechanism of pathogenicity of Streptococcus pneumoniae?

Answer 16

• S.pneumoniae
• antiphagocytic
• 92 different capsular types; serotypes differ
• Quellung reaction (serotype with homologous antibody)

Question 17

What is the first step of Streptococcus pneumoniae pathogenicity mechanism?

Answer 17

• CbpA ahesin: major pneumococcal adhesin. The adhesin interacts with carbohydrates on the pulmonary epithelial surface.

Question 18

What is the second step of Streptococcus pneumoniae pathogenicity mechanism?

Answer 18

• PspA protective antigen: inhibits complement-mediated opsonisation of pneumococci

Question 19

What is the third step of Streptococcus pneumoniae pathogenicity mechanism?

Answer 19

• IgA1 protease: cleaves !gA1 the principal immunoglobulin isotype for the respiratory tract

Question 20

What is the fourth step of Streptococcus pneumoniae pathogenicity mechanism?

Answer 20

• Autolysins- breaks peptide cross linking in cell wall peptidoglycan releasing cell wall components; massive inflammation and pneumolysin release

Question 21

What is the fifth step of Streptococcus pneumoniae pathogenicity mechanism?

Answer 21

Pneumolysin: toxin released during autolysis; inhibits neutrophil chemotaxis phagocytosis, lymphocyte proliferation and immunoglobulin synthesis

Question 22

What are the lab investigations for bacterial pneumonia?

Answer 22

• sample: sputum
• non culture techniques: microscopy, gram stain
• culture: blood/chocolate agar
• safety consideration: cat 2 pathogen, Cat 3 sample

Question 23

What are the aspects of a class 1 safety cabinet?

Answer 23

• negative pressure, inward flow of air
• 0.74m3/sec air flow rate
• HEPA filter

Question 24

What is the basic identification of Streptococcus pneumoniae?

Answer 24

• colonial appearance: Strep pneumoniae grow as alpha-haemolytic colonies, 1 mm in diameter
• gram stain of colonies: gram-positive diplococci

Question 25

What is the full identification of Streptococcus pneumoniae?

Answer 25

• optochin sensitivity: larg zone of inhibition around optochin disc: differentiates pneumococci from ‘normal’ oral streptococci

Question 26

How do you use a urine sample to detect antigens of S. pneumoniae?

Answer 26

• Non-culture technique: immunochromatographic assay/ lateral flow assay
• sample: urine
  1. S. pneumoniae bound to nitrocellulose membrane
  2. urine added to test well; read results in 15mins
  3. 86% sensitivity; 94% specificity
  4. Positive or negative (but does not rule out infection)