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 (aspiration)
- Abnormal ciliary function (e.g. smoking)
- Abnormal mucus (e.g. CF)
- Dilated airways (e.g. bronchiectasis)
- Defect in host immunity
What type of bacterium is Streptococcus pneumoniae?
- Gram-positive cocci in chains
- Alpha-haemolytic and optochin-sensitive
Way to differentiate S. pneumoniae from other alpha-haemolytic streptocci
Optochin
Epidemiology of S. Pneumoniae infection in CAP
20-50% of CAP
Almost always penicillin sensitive
What is pneumonia and what are its presenting symptoms
Inflammation of alveoli due to infection
Presentation:
- Fever
- Cough
- SoB
- Pleuritic chest pain
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.
- VIRUSES
- Streptococcus pneumoniae
- Haemophilus influenzae
- Mycoplasma pneumoniae
- Moraxella catarrhalis
- Staph aureus
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 (85%):
- Streptococcus pnaeumoniae - lobar
- Haemophilus influenzae - bronchopneumonia
Atypical:
- Legionella - Summer/ Water exposure
- Mycoplasma - barking cough, normal CXR
- Coxiella burnetii (Q fever) - farm animals, hepatitis
- Chlamydia psittaci - Exposure to birds, splenomegaly, rash, haemolytic anaemia
What investigations would you consider in pneumonia
FBC, U&E, CRP
Blood culture, sputum culture
ABG
CXR
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
What is bronchitis and in which group of people does it most likely occur
Inflammation of bronchi and medium-sized airways
Mainly affects smokers
Outline the presentation of bronchitis.
- Cough
- Fever
- Increased sputum production
- Increased SOB
- CXR often normal
Which organisms cause bronchitis?
- Viruses
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
How is bronchitis managed
- Smoking cessation
- Bronchodilators
- Physiotherapy
- +/- Antibiotics
List some bacterial causes of cavitating lung lesions.
- Staphylococcus aureus
- Klebsiella pneumoniae
- TB
What type of bacteria is H. influenzae and what kind of agar is it cultured on
- Gram negative coccobacillus
- Cultured on chocolate agar
More common with preexisting lung disease
15-35% CAP
May produce beta-lactamase
How is Legionella spread and what abnormal symptoms can it present with?
Inhalation of infected water droplets
Can present with confusion, abdominal pain and diarrhoea
What electrolyte derangement commonly occurs with Legionella pneumonia
Hyponatraemia (can cause neurological symptoms like confusion or drowsiness)
What would you see on FBC in Legionella infection?
Lymphopaenia
How does Legionella pneumonia appear on CXR
Bilateral interstitial shadowing
What medium is Legionella grown on?
Buffered charcoal yeast extract
How is Legionella pneumoniae diagnosed and treated
Diagnosed by urine antigen detection
Treated with macrolides
(Azithromycin)
What is a feature of bacteria that cause atypical pneumonia and how does it affect treatment?
They have NO cell wall
Therefore not susceptable to cell wall targetting antibiotics e.g. penicillins
