URTI

Question 1

What structures make up the upper respiratory tract?

Answer 1

Nasal cavity
Sinuses
Oral cavity 
Pharynx 
Larynx

Question 2

What infections commonly occur in the nasal cavity?

Answer 2

Common cold:

• rhinoviruses
• coronaviruses
• adenoviruses
• myxoviruses
• echoviruses
• coxsackle A + B
• M pneumoniae and C pneumoniae

Question 3

What pathogens cause the following oral cavity infections:

• dental caries
• thrush
• trench mouth
• stomatitis

Answer 3

• dental caries: S mutans
• thrush: C albicans
• trench mouth: Treponema vicentii, Fusobacterium fusiforme
• stomatitis: Herpes simplex virus

Question 4

What pathogens cause pharyngitis?

Answer 4

• adenovirus
• HSV
• coxsackle viruses
• S pyogenes
• C diphtheriae

Question 5

What pathogens cause croup?

Answer 5

• Parainfluenza viruses

- RSV

Question 6

What pathogen causes epiglottitis?

Answer 6

• H. influenzae

Question 7

What are the most common causes of the common cold? What is the incubation period? what are the S+S?

Answer 7

Causes:

• rhinovirus (30-50%)
• coronavirus (10-15%)

Incubation period: 1-3 days

S+S:
- headache
- sore throat
- nasal congestion
-

Question 8

How is the common cold treated? What symptoms resolve fastest/slowest?

Answer 8

Self-limiting condition and usually resolves within a week 
Treat symptoms:
- painkillers/paracetamol
- decongestants
- cough syrup
- bed rest
- increased fluid intake 

Symptoms:

• fever, sneezing, sore throat usually resolve first
• cough and congestion takes longer

Question 9

Describe the viral infection process.

Answer 9

1. Bind to extracellular membrane of host cell
2. Virus transported inside the cell
3. Viral DNA released inside the cell
4. DNA replication and protein formation
5. Viral material is packaged and released via neuraminidase –> then spread to other cells

Question 10

Explain the pathophysiology of human rhinovirus (HRV) infection?

Answer 10

1. HRV infection of airway epithelial cells
2. Pathogen recognised via toll-like and retinoid acid-inducible gene-I-like receptors
3. Epithelial cells release pro-inflammatory mediators (TNF-alpha, IFN, CXCL8)
4. Recruitment and activation of inflammatory and immuno-effector cells

*inflammatory and immune responses facilitate clearance of the virus but also amplify pre-existing inflammation and contribute to disease exacerbation

Question 11

Explain the pathophysiology of RSV infection.

Answer 11

a) Viral RNA, arising during viral replication, is recognised through Toll-like receptor (TLR)-3 and retinoic acid-inducible gene (RIG)-I-like receptors
- Cellular infection triggers the release of early inflammatory mediators (e.g.interferons (IFNs) and tumour necrosis factor (TNF)-α) and chemokines (e.g.CXCL8 and CXCL11)
- Type I IFNs upregulate pro-apoptotic factors in the epithelial cells
- TNF-α and chemokines recruit natural killer (NK) cells and polymorphonuclear leukocytes (PMNs) that have the ability to kill the infected cells
- This limits viral replication and spread to neighbouring cells in the first days of infection

b) RSV can also infect dendritic cells that carry viral antigens to regional lymph nodes
- Presentation of viral antigens to CD4+T-lymphocytes occurs and primed T-cells activate B-lymphocytes and CD8+T-cells.

Question 12

Explain how the major symptoms of the common cold are caused.

Answer 12

• Neutrophilic inflammation
• this increases vascular permeability and also increases mucus hypersecretion
• leads to rhinorrhea and nasal obstruction

Question 13

What are the most common viral and bacterial pathogens to cause pharyngitis?

Answer 13

Viral:

• Adenovirus (most common viral)
• Infectious mononucleosis
• HSV

Bacterial:

• Streptococcus A (most common bacterial)
• Strep pneumoniae
• Haemophilus influenza

Question 14

What is the Centor criteria?

Answer 14

Used to determine the management of people with pharyngitis.

One point for each:

• Absence of a cough
• Swollen and tender cervical lymph nodes
• Temperature more than 38.0 °C (100.4 °F)
• Tonsillar exudate or swelling
• Age less than 15 (a point is subtracted if age is more than 44)

Points:
+1 = <10% prob of Strep –> no abx or culture needed
+2 = 11-17% of Strep –> abx based on culture or rapid antigen detection test
+3 = 28-35% –> abx based on culture or rapid antigen detection test
+4 = 52% prob of Strep –> empiric abx

Question 15

What antibiotics should be given to treat pharyngitis caused by Strep?

Answer 15

Penicillin

Question 16

Given that a person is allergic to penicillin, what antibiotics should be given to treat pharyngitis caused by Strep?

Answer 16

clarithromycin or erythromycin