MICRO: URTIs Flashcards
4 medical emergencies re: URTIs
- diphtheria
- acute epiglottitis
- quinsy (massive abscess around the tonsils which can block airway)
- croup
‘professional’ vs secondary invaders of the resp system
- professional - infect healthy resp system
- secondary - infect when host defences are impaired
top 5 URTIs
- common cold
- pharyngitis
- diphtheria
- glandular fever
- acute laryngitis
common cold
- aetiology
- incubation period
- Sx
- aetiology: many pathogens e.g. rhinovirus, coronavirus, influenza
- short incubation: 12 hrs-2 days
- manifestation: rhinorrhea, sneezing, sore throat, headache, malaise
common cold
- transmission
- pathogenesis
- Dx
- Tx
- transmission: direct contact, droplet inhalation
- pathogenesis: pathogen infects nasal epithelium > inflammatory response
- Dx: clinical Dx - only PCR to rule out COVID or if infects LRT
- Tx: no effective antiviral, AVOID ANTIBIOTICS, just treat Sx e.g. antihistamines, paracetamol, hydration
pharyngitis and tonsillitis
aetiology
- most commonly viruses e.g. rhinovirus, coronavirus, adenovirus, parainfluenza virus, influenza
- less commonly bacteria e.g. group A, C and G streptococcus
group A beta haemolytic streptococcal pharyngitis (GABHS):
- Sx
- complications
- most common BACTERIAL cause of acute pharyngitis
- Sx: high fever, chills, cervical lymphadenopathy, no cough, ENLARGED PAINFUL TONSILS WITH PUS AND SUDDEN ONSET (unlike viral which is slower)
- suppurative (pus) complications: massive abscess around the tonsils (quinsy), otitis media, sinusitis, mastoiditis
- non-suppurative (no pus) complications: scarlet fever, acute glomerulonephritis, rheumatic fever, rheumatic heart disease
scarlet fever
- what is it a complication of?
- pathogenesis
- Sx
- complication of GABHS pharyngitis
- S. pyogenes toxin lyses cells
- Sx: punctate (dotted) erythematous rash + strawberry tongue
acute glomerulonephritis
- what is it a complication of?
- when does it occur
- pathophys
- complication of GABHS pharyngitis
- 1-2 weeks after sore throat
- circulating immune complexes get deposited in glomeruli > inflammatory response
rheumatic fever
- what is it a complication of?
- when does it occur
- pathogenesis
- complication of GABHS pharyngitis
- 2-4 weeks after sore throat
- host antibodies against S. pyogenes cross-react with heart or other tissue
rheumatic heart disease
- what is it a complication of?
- pathogenesis
- complication of GABHS pharyngitis
- repeated attacks of S. pyogenes damage heart valves
Dx of GABHS pharyngitis
- usually don’t need lab diagnosis, but if you do:
- throat swab on horse blood agar (B- haemolytic)
- rapid diagnostic tests
- direct gram stain (but often inconclusive due to normal flora)
Tx for pharyngitis
- viral: symptomatic Tx
- bacterial: antibiotics
diphtheria
- aetiology
- pathogenesis
- Sx
- C. diphtheriae
- destroys epithelial cells but not deeper tissue, h/w exotoxin can damage heart and liver
- Sx: airway blockage due to necrotic epithelial exudate (leaked fluid), extensive inflammation and swelling, enlarged cervical L/N = ‘bull neck’
management and prevention of diphtheria
- anti-toxin and antibiotics (usually penicillin)
- isolation + contact tracing b/c highly infectious
- monitor for respiratory obstruction
- prevention: DTaP vaccination (+ booster for high risk ppl)
glandular fever (mono) aetiology, transmission + pathogenesis
- aetiology: epstein-barr virus
- transmission: kissing (mostly affects young children or teenagers)
- remains latent in B cells > reactivates during immunodeficiency
Sx and Tx of glandular fever
- fever
- lethargy
- sore throat
- headache
- lymphadenopathy
- hepatomegaly + splenomegaly
- hepatitis
- rash + jaundice
- Tx: usually self-limiting (2-3 weeks)
acute laryngitis aetiology + Sx
- aetiology: parainfluenza virus, coronavirus, rhinovirus, influenza
- Sx: common cold, hoarseness, barking cough
acute laryngitis Dx + Tx
- Dx: clinical (no lab)
- Tx: symptomatic, rest voice, humidification
laryngotracheobronchitis (croup)
- aetiology
- Sx
- age group
- aetiology: most commonly parainfluenza
- Sx: history of URTI, fever, barking cough, restlessness, stridor, respiratory distress
- age: 3 months to 3 years
croup Dx and Tx
- lab Dx: nasopharyngeal swab
- Tx: symptomatic (for mild), maintain airway, minimal handling, antibiotics if secondary infection occurs
acute epiglottitis
- aetiology
- pathophys
- Sx
- aetiology: H. influenzae type B
- cellulitis of epiglottis + surrounding structures = airway blockage
- Sx: acute onset, fever, sore throat, dysphagia, drooling, hoarseness, cough, respiratory distress, stridor
acute epiglottitis:
- Dx
- Mx
- prevention
- Dx: DO NOT THROAT SWAB but can do blood culture
- Mx: maintain airway, antibiotics
- prevention: H. influenzae vaccine
sinusitis:
- types and aetiology
- Sx
- community acquired (viral): rhinovirus, parainfluenza, influenza
- community acquired (bacterial): S. pneumoniae, H. influenzae, M. catarrhalis
- hospital acquired: S. aureus, P. aeruginosa
- Sx: facial tenderness
3 types of otitis externa
- localised
- diffuse (swimmer’s ear)
- invasive (‘malignant’)
acute localised otitis externa
- aetiology
- Sx
- S. aureus skin infection
- pustules associated with hair follicles
acute diffuse otitis externa (swimmer’s ear)
- aetiology
- Sx
- P. aeruginosa
- swollen, red ear canal + discharge
invasive (‘malignant’) otitis externa
- aetiology
- Tx
- severe necrotising infection that spreads to surrounding tissues
- usually in elderly/immunocompromised
- P. aeruginosa
- Tx: oral antibiotics + ear drops with antibiotics and steroids
acute otitis media
- aetiology
- age group
- usually consequence of URTI
- can become chronic due to discharge from perforated eardrum if acute attacks aren’t treated
- aetiology: most commonly viruses e.g. RSV but also bacteria e.g. S. pneumoniae, H. influenzae
- most commonly in children b/c horizontal eustachian tube = harder to drain nasal secretions
otitis media Sx
- fever, lethargy, irritability
- earache, discharge, hearing loss, bulging eardrum
- ‘glue ear’ = persistent discharge for weeks/months
