4. LRTI Flashcards
What are acute LRTI?
- pneumonia
- bronchitis
- bronchiolitis
- legionnaires’ disease
- whooping cough
What are chronic LRTI?
- tuberculosis
- aspergillosis
- cystic fibrosis
What is pneumonia?
- 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
What is the classification of pneumonia?
- Community-acquired diagnosis
- Hospital-acquired diagnosis
- Aspiration pneumonia
- Recurrent pneumonia
What is CAP?
- mainly seasonal: autumn/winter
- CAP is diagnosed in 5-12% of patients presenting to their GP with symptoms of LRTI
What are the signs and symptoms of typical pneumonia?
(predominantly respiratory and common in elderly)
- signs: cough, cyanosis, tachypnoea, tachycardia
- symptoms: fever, muscle aches, shakes/rigors, dyspnoea, sputum production
Microorganisms associated with typical CAP?
Streptococcus Pneumoniae
- less common:
Haemophilus influenzae
Staphylococcus aureus CF
Pseudomonas aeruginosa CF
What are the signs and symptoms of atypical pneumonia?
(predominantly non-respiratory)
- signs: rash, cyanosis, tachypnoea, tachycardia, dry cough
- symptoms: headache, confusion, diarrhoea, incontinence, no sputum
What are the microorganisms associated with atypical CAP?
most common:
- mycoplasma pneumoniae
less common:
- leigionella pneumophila
- chlamydophila psittaci
- chlamydophila pneumoniae
What is the radiological appearance of typical pneumonia?
widespread consolidation
What is the radiological appearance of atypical pneumonia?
patchy consolidation
What are the CAP risk factors?
- elderly/young (A/T)
- smokers/ travel abroad (A)
- alcoholics/vagrants (T)
- contacts with animals/ birds (A)
- underlying illness (T)
What is HAP?
- 3rd most common hospital acquired infection
- patients can be typical or atypical
What are the risk factors for HAP?
- ventilatory support
- immunosuppression: organ transplantation
- immobility and vomiting
What is the treatment of pneumonia?
- uncomplicated CAP: amoxicillin or erythromycin
- severe CAP: cefuroxime and erythromycin
- atypical pneumonia: erythromycin
- HAP: cefotaxime and gentamicin
What is the mechanism of pathogenicity of Streptococcus pneumoniae?
- S.pneumoniae
- antiphagocytic
- 92 different capsular types; serotypes differ
- Quellung reaction (serotype with homologous antibody)
What is the first step of Streptococcus pneumoniae pathogenicity mechanism?
- CbpA ahesin: major pneumococcal adhesin. The adhesin interacts with carbohydrates on the pulmonary epithelial surface.
What is the second step of Streptococcus pneumoniae pathogenicity mechanism?
- PspA protective antigen: inhibits complement-mediated opsonisation of pneumococci
What is the third step of Streptococcus pneumoniae pathogenicity mechanism?
- IgA1 protease: cleaves !gA1 the principal immunoglobulin isotype for the respiratory tract
What is the fourth step of Streptococcus pneumoniae pathogenicity mechanism?
- Autolysins- breaks peptide cross linking in cell wall peptidoglycan releasing cell wall components; massive inflammation and pneumolysin release
What is the fifth step of Streptococcus pneumoniae pathogenicity mechanism?
Pneumolysin: toxin released during autolysis; inhibits neutrophil chemotaxis phagocytosis, lymphocyte proliferation and immunoglobulin synthesis
What are the lab investigations for bacterial pneumonia?
- sample: sputum
- non culture techniques: microscopy, gram stain
- culture: blood/chocolate agar
- safety consideration: cat 2 pathogen, Cat 3 sample
What are the aspects of a class 1 safety cabinet?
- negative pressure, inward flow of air
- 0.74m3/sec air flow rate
- HEPA filter
What is the basic identification of Streptococcus pneumoniae?
- colonial appearance: Strep pneumoniae grow as alpha-haemolytic colonies, 1 mm in diameter
- gram stain of colonies: gram-positive diplococci
