URTI Flashcards
What structures make up the upper respiratory tract?
Nasal cavity Sinuses Oral cavity Pharynx Larynx
What infections commonly occur in the nasal cavity?
Common cold:
- rhinoviruses
- coronaviruses
- adenoviruses
- myxoviruses
- echoviruses
- coxsackle A + B
- M pneumoniae and C pneumoniae
What pathogens cause the following oral cavity infections:
- dental caries
- thrush
- trench mouth
- stomatitis
- dental caries: S mutans
- thrush: C albicans
- trench mouth: Treponema vicentii, Fusobacterium fusiforme
- stomatitis: Herpes simplex virus
What pathogens cause pharyngitis?
- adenovirus
- HSV
- coxsackle viruses
- S pyogenes
- C diphtheriae
What pathogens cause croup?
- Parainfluenza viruses
- RSV
What pathogen causes epiglottitis?
- H. influenzae
What are the most common causes of the common cold? What is the incubation period? what are the S+S?
Causes:
- rhinovirus (30-50%)
- coronavirus (10-15%)
Incubation period: 1-3 days
S+S: - headache - sore throat - nasal congestion -
How is the common cold treated? What symptoms resolve fastest/slowest?
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
Describe the viral infection process.
- Bind to extracellular membrane of host cell
- Virus transported inside the cell
- Viral DNA released inside the cell
- DNA replication and protein formation
- Viral material is packaged and released via neuraminidase –> then spread to other cells
Explain the pathophysiology of human rhinovirus (HRV) infection?
- HRV infection of airway epithelial cells
- Pathogen recognised via toll-like and retinoid acid-inducible gene-I-like receptors
- Epithelial cells release pro-inflammatory mediators (TNF-alpha, IFN, CXCL8)
- 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
Explain the pathophysiology of RSV infection.
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.
Explain how the major symptoms of the common cold are caused.
- Neutrophilic inflammation
- this increases vascular permeability and also increases mucus hypersecretion
- leads to rhinorrhea and nasal obstruction
What are the most common viral and bacterial pathogens to cause pharyngitis?
Viral:
- Adenovirus (most common viral)
- Infectious mononucleosis
- HSV
Bacterial:
- Streptococcus A (most common bacterial)
- Strep pneumoniae
- Haemophilus influenza
What is the Centor criteria?
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
What antibiotics should be given to treat pharyngitis caused by Strep?
Penicillin
