MI: Respiratory Tract Infections Flashcards
List some ways in which the body can be compromised, thereby increasing the risk of respiratory tract infection.
- Poor swallow - stroke, muscle weakness, alcohol
- Abnormal ciliary function - smoking, kartagener’s
- Abnormal mucus - CF
- Dilated airways - bronchiectasis
- Defect in host immunity - HIV, immunosuppression
URTIs
sinusitis
tonsilitis
LRTIs
bronchitis
pneumonia
empyema
bronchiectasis
lung abscess
What type of bacterium is Streptococcus pneumoniae?
- Gram-positive cocci in chains
- Alpha-haemolytic and optochin-sensitive
penicillin sensitive
Why is no microbiological identification of the pathogen made in the most cases of CAP?
Difficult to obtain a good sputum sample and early treatment is usually initiated with empirical antibiotics
List the main organisms that cause CAP.
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
- Staphylococcus aureus
- Klebsiella pneumoniae
List the most prevalent pathogens causing CAP in the following age groups:
- 0-1 months
- 1-6 months
- 6 months - 5 years
- 16 - 30 years
0 - 1 months:
- Escherichia coli
- Group B Streptococcus
- Listeria monocytogenes
1-6 months:
- Chlamydia trachomatis
- Staphylococcus auerus
- RSV
6 months - 5 years:
- Mycoplasma pnaeumoniae
- Influenza
16-30 years:
- Mycoplasma pneumoniae
- Streptococcus pneumoniae
List the causes of CAP that fall into the following two categories:
- Typical
- Atypical
Typical:
- Streptococcus pnaeumoniae
- Haemophilus influenzae
Atypical:
- Legionella
- Mycoplasma
- Coxiella burnetii - Q fever, farm animals
- Chlamydia psittaci - birds exposure: haemolytic anaemia, splenomegaly
Viral - influenza A, B
What is the CURB-65 score? How is it interpreted?
- Confusion
- Urea > 7 mmol/L
- Respiratory rate > 30/min
- BP < 90 systolic, < 60 diastolic
- Score of 2 = consider hospital admission
- Score of more than 2 = severe pneumonia that may need ITU admission
Outline the presentation of bronchitis.
- Cough
- Fever
- Increased sputum production
- Increased SOB
mainly in smokers
inflammation of medium size airways
Which organisms cause bronchitis?
- Viruses
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
Mx - bronchodilation, chest physio, often don’t rewuire Abx
List some bacterial causes of cavitating lung lesions.
- Staphylococcus aureus
- Klebsiella pneumoniae
- TB
What type of bacterium is H. influenzae?
Gram-negative cocci-bacilli
produces beta lactamase
How is Legionella spread?
Inhalation of infected water droplets
What medium is Legionella grown on?
Buffered charcoal yeast extract
Whatis a common feature of bacteria that cause atypical pneumonia?
They have NO cell wall
therefore beta lactams won’t work
List four atypical organisms.
- Mycoplasma
- Legionella
- Chlamydia
- Coxiella
extrapulmonary features
Which type of antibiotics do not work on atypical bacteria?
beta lactams
NOTE: this is because they act on cell walls
Which type of antibiotics do work on atypical bacteria?
Antibiotics that interfere with protein synthesis (macrolides, tetracyclines)
List some clinical features of Legionella pnaeumophila infection.
- Confusion
- Abdominal pain
- Diarrhoea
- Lymphopaenia
* Hyponatraemia
+ve urinary/serum antigen
Urinary antigens are associated with which causes of pnaeumonia?
- Streptococcus pneumoniae
- Legionella pneumophila
Which investigation is used for Coxiella and Chlamydia psittaci?
Serology
NOTE: serology looks at the development of antibodies after an infection (requires paired samples). It is useful for investigating bacteria that are difficult to culture.
coxiella - farm animals, chalmydia - birds
What is an empyema?
Collection of pus within the pleural cavity
List some reasons for failure to respond to treatment.
- Empyema/abscess
- Proximal obstruction (e.g. tumour)
- Resistant organisms e.g. TB
- Not absorbing antibiotics
- Immunosuppression
- Alternative diagnosis (e.g. lung cancer)
