MI: Respiratory Tract Infections Flashcards
List soe ways in which the body can be compromised, thereby increasing the risk of respiratory tract infection.
- Poor swallow
- 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
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
- Chlamydia psittaci
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
Which organisms cause bronchitis?
- Viruses
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
List some bacterial causes of cavitating lung lesions.
- Staphylococcus aureus
- Klebsiella pneumoniae
- TB
What type of bacterium is H. influenzae?
Gram-negative cocci-bacilli
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
List four atypical organisms.
- Mycoplasma
- Legionella
- Chlamydia
- Coxiella
Which type of antibiotics do not work on atypical bacteria?
Penicillins
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
Urinary antigens are associated with which causes of pnaeumonia?
- Streptococcus pneumoniae
- Legionalla 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.
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
- Not absorbing antibiotics
- Immunosuppression
- Alternative diagnosis (e.g. lung cancer)
What is the classical CXR feature of TB?
Upper lobe cavitation
Which types of staining are used when investigating TB?
- Auramine staingin
- Ziehl-Neelsen stain
NOTE: they are red rods
Define hospital-acquired pneumonia.
A pneumonia that is onset > 48 hours after hospital admission
List some organisms that cause HAP.
- Enterobacteriaciae (MOST COMMON - e.g. E. coli, K. pneumoniae)
- Staphylococcus aureus
- Pseudomonas
- Haemophilus influenzae
- Acinetobacter baumanii
- Fungi (e.g. Candida)
What is Pneumocystic jirovecii pneumonia?
Fungus that is ubiquitous in the environment but can cause pneumonia in immunocompromised patients
Describe the typical presentation of Pneumocystic jirovecii pneumonia.
- Dry cough
- Weight loss
- SOB
- Malaise
- Walk test - desaturation on exertion
How is PCP investigated?
Bronchoalveolar lavage
What is the treatment for PCP?
Co-trimoxazole (septrin)
What are the main features of allergic bronchopulmonary aspergillosis?
- Chronic wheeze
- Eosinophilia
- Bronchiectasis
What is an aspergilloma?
- Fungal ball often forming within a pre-existing cavity
- May cause haemoptysis
How is invasive aspergillosis treated?
Amphotericin B
Which organisms cause pneumonia in the following subgroups of patients:
- HIV
- Neutropenia
- Bone marro transplant
- Splenectomy
- HIV: PCP, TB, Atypical mycobacteria
- Neutropaenia: Fungal (e.g. Aspergillus)
- Bone marrow transplant: CMV
- Splenectomy: Encapsulated organisms (e.g. Streptococcus pnaeumoniae, Haemophilus influenzae)
In which organisms is serology useful for reaching a diagnosis?
Organisms that are difficult to culture
Examples: Legionella, Chlamydia
Which organism is investigated using immunofluorescence?
PCP
NOTE: PCP can also be detected using silver stain
What is the treatment for mild-to-moderate CAP?
Amoxicillin
OR erythromycin/clarithryomycin (if penicillin allergic)
What is the treatment for moderate-to-severe CAP?
Co-amoxiclav AND clarithromycin
What are the 1st and 2nd line treatment options for HAP?
- 1st = ciprofloxacin +/- vancomycin
- 2nd = tazocin AND vancomycin
Which antibiotics are used to treat HAP caused by:
- MRSA
- Pseudomonas
- MRSA - Vancomycin
- Pseudomonas - Tazocin OR ciprofloxain +/- gentamicin
