CSIM 1.62: Bacterial and Fungal Respiratory Tract Infections Flashcards
Which particles are filtered out by nasal hair?
those larger than 10μm
What is found in upper respiratory tract which defends against microbes?
- IgA
- Bacteriocidal enzymes
- Complement
What defences are found in the lower airways
- Particles 2-10μm are trapped
- Alveolar macrophages + systemic
- Inflammatory response
Recall the components of the innate immunity
- Mast cells and basophils (inflammatory granulocytes)
- Natural killer cells
- Complement
- Phagocytes: monocytes, neutrophils, macrophages
What are the symptoms of a URTI?
What kind of bacteria are found in these?
If non-exudative, what is the causative agent?
- Sore throat
- Cervical lymphadenopathy
- Tonsillitis
- Pharyngitis
Gram positive streptococci in EXUDATIVE URRI
Viral
What are the common bacteria which cause pharyngitis? What symptom does this produce due to its toxin?
Group A Streptococci (GAS infection)
Produces Scarlet fever due to erythrogenic toxin (Rash on face, palms and soles.
What toxin is seen in Corynebacterium diphtheriae? What do these do?
What are the other features of dipheria?
Toxin with subunits A and B:
• Subunit A: causes systemic toxicity by preventing protein synthesis
• Subunit B: carries toxin to the myocardium and PNS and gives the toxin access to the cell (like botox)
Causes myocarditis and circulatory failure
Membrane of bacteria, and polymorphs over the tonsil and pharynx - causes: • change in voice • difficulty breathing • Cyanosis • Sore throat
What are the complications of pharyngitis?
- TSS
- Lamierre’s syndrome
- Sinusitis
- Otitis media
- Peritonsilar abscess
What are the symptoms of laryngitis?
What are the common bacteria which cause this?
- Hoarseness of voice
- Dry cough
- GAS
- Tuberculosis
- Mycoplasma pneumoniae
Describe the pathogenesis of otitis media when caused by URTI
- Viral URTI
- Eustachian tube swells
- Secretions from middle ear cannot be cleared
- These stay in the ear, and cause a breeding ground for S. pneuomoniae and H. influenzae
When are antibiotics used for otitis media?
If there is a history of repeated infection
What can chronic otitis media lead to? how is this treated and why?
Mastoiditis - urgent surgical drainage and antibiotics needed, as this can spread to the bone and to the brain, causing abscesses in each
What bacteria can cause sinusitis?
What other causative agents are seen, and in which patients?
How is sinusitis treated?
- S. aureus
- S. pneumoniae
- H. influenzae
Fungal infections seen in:
• Diabetics
• Immunocompromised patients
Treated with surgical drainage and antibiotics
What is the primary and most immediate risk with epiglottitis?
What bacterium often causes this?
What are the features of epiglottitis?
Airway obstruction
H. influenzae type B (HiB)
- Sore throat
- Cherry red swollen epiglottis
How is epiglottitis treated?
- Airway management
* IV antibiotics
What are the differential diagnoses for epiglottitis? (i.e. shortness of breath, sore throat)
- Croup
* Diphtheria
What are the LRTIs?
- Laryngotracheobronchitis
- Whooping cough
- Acute bronchitis
- Acute pneumonias
- Empyema
- Lung abscess
What is acute bronchitis and what are the causative agents?
Infection and inflammation of large and medium-sized airways
• Dry cough
• Wheezing
• Purulent sputum
Viral
• Rhinovirus
• Coronavirus
Bacterial • S. pneumoniae • Mycoplasma pneumoniae • H. influenzae • Chlamydia pneumoniae
What is pneumonia? What are the types of pneumonia?
Inflammation of lung parenchyma • Lobar pneumonia • Bronchopneumonia • Atypical pneumonia (not caused by traditional pathogens) • Aspiration pneumonia • Ventilator-associated pneumonia
Can be hospital-acquired or community-acquired
How can lab diagnosis of pneumonia causative agent be performed?
- Sputum culture
- Blood culture
- Urine antigens for PNEUMOCOCCI or LEGIONELLA
- Blood antigens for STREPTOCOCCI
What is the most common medium of transmission for:
1) Aspergillus spp.?
2) Cryptococcus neoformans?
Which patients are most likely to get these infections?
1) Dust exposure from building works
2) Pigeon droppings
Immunocompromised (fungal infections)
Failure in which defences increases the incidence of fungal RTIs?
Local cell-mediated immunity
• Phagocytes (macrophages, neutrophils and monocytes) lacking myeloperioxidase so no hydrogen peroxide
What are the clinical features of fungal RTIs?
In which patients do these infection most commonly spread to the sinuses?
- Oral thrush
- Oesophageal candidiasis
- Fungal pneumonia (contiguous from oral thrush due to aspiration to the lungs)
In diabetic patients
How is fungal pneumonia treated when caused by candida?
- Azoles - fluconazole
* Nystatin