Flashcards in RESP - Respiratory infections Deck (28):
Cx of bacterial pneumonia (4)
Define primary & post-primary tuberculosis
Primary: no previous infection/exposure
Post-primary: fresh infection in previously sensitised individual or reactivation of previously dormant primary lesion
How is tuberculosis infection established?
TB enters by airway -> tends to lodge peripherally: focus of primary infection (Gohn focus) at the apex of lower lobe or apex of upper lobe. Area of fibrosis underneath pleura. With reactive organisms, hilar lymph node is enlarged. Gohn complex = Gohn focus + hilar lymph node
Describe Necrotising granulomatous inflammatory process (TB histological pattern in the lung)
- multinuclear cells
- small lymphocytes
- caseous necrosis in the centre
Describe miliary tuberculosis
Primary invasion in venous system. TB all throughout the body
What are the pathological features of acute necrotising viral pneumonia?
- necrosis of bronchial epithelium
- acute inflammatory exudate in bronchial lumen
- haemorrhage into alveoli
- inflammatory infiltration into surrounding alveoli
When do you see viral inclusion bodies?
Describe 3 types of aspergillosis
1. allergic bronchopulmonary aspergillosis
- proximal airways
- mucoid impaction
-structure of airways maintained
2. Bronchopulmonary aspergillosis
- distal airways
- granulomatous inflammatory destruction of airways
3. Angio-invasive aspergillosis
- invasion of pulmonary arteries/veins
- haemorrhagic infarction
What are the common fungal causes of pneumonia?
- Cryptococcus neoformans (can spread systemically -> can form a mass lesion in the brain)
All more common in immunocompromised
What are the host risk factors in resp infection?
1. immune status
- type of compromise
- normal flora change with age & other factors
- social changes (day care, college)- infants & elderly
3. structural/physiological abnormalities
-e.g. bronchiectasis, tumour, CF
What are examples of URTI & their causative agents?
- pharyngitis: group A strep, viruses
-sinusitis: viruses, strep pneumoniae, H. influenzae, fungi
- otitis media: Strep pneumoniae
- epigolttitis: H. influenzae type B
Specimen collection for culture for
- pharyngitis: throat swab
- sinusitis: sinuses swab (surgical)
- otitis media: diagnosed clinically. rarely obtain tympanocentesis
- epiglottitis: direct swab of epiglottis. blood cultures
Describe Bordetella pertussis
- Gram negative rod
- very difficult to culture (fastidious)
- Ix: PCR & serology
- Rx: macrolide Abx within 3 weeks
- notifiable disease
- vaccine available
What are the common respiratory tract viruses & their usual clinical associations?
- Influenza A, B: seasonal & pandemic influenza, pneumonia
- Parainfluenza types 1, 2, 3: Group, bronchiolitis, pneumonia
- Rhinovirus: mild URTI
- Respiratory syncitial virus: Croup, bronchitis, pneumonia
- Adenovirus: mild infection.
- Coronavirus: mild URTI, SARS & MERS
- Human metapneumovirus: usually mild URTI
- Human bocavirus: usually mild URTI
What are the 3 most common organisms of typical pneumonia?
1. Streptococcus pneumoniae
2. Haemophhilus influenzae
3. Staphylococcus aureus
What are the 3 most common organisms of atypical pneumonia?
1. Legionella pneumophila
2. Mycoplasma pneumoniae
3. Chlamydophia pneumoniae
What are the 3 types of pneumonia (venue & aetiology related)?
1. community acquired pnuemonia
2. Nosocomial pneumonia
3. Aspiration pneumonia: mixed anaerobes & aerobes
How do you diagnose CAP?
M/C/S of sputum from the lungs rather than from the oral cavity
Describe Streptococcus pneumoniae
- Gram positive diplococci
- polysaccharide capsule
- typical alpha haemolytic "draughtsmans" colonies on blood agar
- catalase negative
- optochin susceptible Clinically: causes classical lobar pneumonia, sinusitis, otitis media, bacteraemia & meningitis
RF: older age, alcoholism, indigenous Australians
Dx: "rust" coloured sputum, urinary Ag, PCR.
Describe Haemophilus influenzae
- Gram negative short rods (coccobacilli)
- polysaccharide capsule
- Fastidious; does not grow on blood agar, requires X & V factors for growth
Clinically cause lobar pneumonia, meningitis, etcRF: infants
Dx: Culture on chocolate agar
Describe Staphylococcus aureus
- Gram positive cocci in clusters- catalase positive, coagulase positive- grows well on routine lab agarClinically: more associated with underlying abnormalities. Secondary to viral/other infection, healthcare (nosocomial) settings, ventilator-associated pneumonia. DX: culture of sputum. Antibody susceptibility (e.g. MRSA)
Describe Legionella pneumophila
- Gram negative rod- fastidious (special agar required)Clinically: atypical pneumonia, systemic features common. RF: exposure, weakened immune system, older age, alcoholism, smokingDx: culture, urinary Ag (only covers one type), serology, PCR
Describe Chlamydophila pneumoniae & Chlamydophila psittaci
- intracellular - not readily detected by microscopy/cultureClinically: atypical pneumoniae. RF: young adults/ adolescents. Associated with birds as pets. (Psittaci)Dx: PCR
Describe mycoplasma pneumoniae
- intracellular- no true cell wallClinically: similar to C. pneumoniae (common, atypical, mild)RF: all ages. children. young adultsDx: PCR.
Describe Mycobacterium tuberculosis
- acid fast baccili. Ziehl-Nielson staining used- Mycolic acids in cell wall- slow growing (2-6 weeks)- PCR- can also look for it in the urine
Describe Pneumocystic jirovecii
- considered as a fungus- not culturable but can see with Silver stain- PCR- cause of pneumonia in immunocompromised (e.g. HIV)- insidious onset of SOB
- Gram positive branching bacilli - Mycolic acids in the wall but not quite acid fast - can cause abscess in the brain- cavitating lesions