CSIM 1.62: Bacterial and Fungal Respiratory Tract Infections

Question 1

Which particles are filtered out by nasal hair?

Answer 1

those larger than 10μm

Question 2

What is found in upper respiratory tract which defends against microbes?

Answer 2

• IgA
  
  • Bacteriocidal enzymes
  • Complement

Question 3

What defences are found in the lower airways

Answer 3

• Particles 2-10μm are trapped
  
  • Alveolar macrophages + systemic
  • Inflammatory response

Question 4

Recall the components of the innate immunity

Answer 4

• Mast cells and basophils (inflammatory granulocytes)
  
  • Natural killer cells
  • Complement
  • Phagocytes: monocytes, neutrophils, macrophages

Question 5

What are the symptoms of a URTI?

What kind of bacteria are found in these?

If non-exudative, what is the causative agent?

Answer 5

• Sore throat
  
  • Cervical lymphadenopathy
  • Tonsillitis
  • Pharyngitis

Gram positive streptococci in EXUDATIVE URRI

Viral

Question 6

What are the common bacteria which cause pharyngitis? What symptom does this produce due to its toxin?

Answer 6

Group A Streptococci (GAS infection)

Produces Scarlet fever due to erythrogenic toxin (Rash on face, palms and soles.

Question 7

What toxin is seen in Corynebacterium diphtheriae? What do these do?

What are the other features of dipheria?

Answer 7

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

Question 8

What are the complications of pharyngitis?

Answer 8

• TSS
  
  • Lamierre’s syndrome
  • Sinusitis
  • Otitis media
  • Peritonsilar abscess

Question 9

What are the symptoms of laryngitis?

What are the common bacteria which cause this?

Answer 9

• Hoarseness of voice
  
  • Dry cough
  • GAS
  • Tuberculosis
  • Mycoplasma pneumoniae

Question 10

Describe the pathogenesis of otitis media when caused by URTI

Answer 10

• 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

Question 11

When are antibiotics used for otitis media?

Answer 11

If there is a history of repeated infection

Question 12

What can chronic otitis media lead to? how is this treated and why?

Answer 12

Mastoiditis - urgent surgical drainage and antibiotics needed, as this can spread to the bone and to the brain, causing abscesses in each

Question 13

What bacteria can cause sinusitis?

What other causative agents are seen, and in which patients?

How is sinusitis treated?

Answer 13

• S. aureus
  
  • S. pneumoniae
  • H. influenzae

Fungal infections seen in:
• Diabetics
• Immunocompromised patients

Treated with surgical drainage and antibiotics

Question 14

What is the primary and most immediate risk with epiglottitis?

What bacterium often causes this?

What are the features of epiglottitis?

Answer 14

Airway obstruction

H. influenzae type B (HiB)

• Sore throat
• Cherry red swollen epiglottis

Question 15

How is epiglottitis treated?

Answer 15

• Airway management

* IV antibiotics

Question 16

What are the differential diagnoses for epiglottitis? (i.e. shortness of breath, sore throat)

Answer 16

• Croup

* Diphtheria

Question 17

What are the LRTIs?

Answer 17

• Laryngotracheobronchitis
  
  • Whooping cough
  • Acute bronchitis
  • Acute pneumonias
  • Empyema
  • Lung abscess

Question 18

What is acute bronchitis and what are the causative agents?

Answer 18

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

Question 19

What is pneumonia? What are the types of pneumonia?

Answer 19

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

Question 20

How can lab diagnosis of pneumonia causative agent be performed?

Answer 20

• Sputum culture
  
  • Blood culture
  • Urine antigens for PNEUMOCOCCI or LEGIONELLA
  • Blood antigens for STREPTOCOCCI

Question 21

What is the most common medium of transmission for:

1) Aspergillus spp.?
2) Cryptococcus neoformans?

Which patients are most likely to get these infections?

Answer 21

1) Dust exposure from building works
2) Pigeon droppings

Immunocompromised (fungal infections)

Question 22

Failure in which defences increases the incidence of fungal RTIs?

Answer 22

Local cell-mediated immunity

• Phagocytes (macrophages, neutrophils and monocytes) lacking myeloperioxidase so no hydrogen peroxide

Question 23

What are the clinical features of fungal RTIs?

In which patients do these infection most commonly spread to the sinuses?

Answer 23

• Oral thrush
  
  • Oesophageal candidiasis
  • Fungal pneumonia (contiguous from oral thrush due to aspiration to the lungs)

In diabetic patients

Question 24

How is fungal pneumonia treated when caused by candida?

Answer 24

• Azoles - fluconazole

* Nystatin

Question 25

What fungi can cause fungal pneumonia?

Answer 25

• Candida
  
  • Aspergillus
  • Mucor