L3: Fever and cough - URTI

Question 1

Common bacterial causes of URTI

Answer 1

• Streptococcus pyogenes (only causes pharyngitis)
• Streptococcus pneumoniae (otitis media, sinusitis, pneumonia, NOT pharyngitis)
• Haemophilus influenzae
• Moraxella catarrhalis
• Bordetella pertussis

Question 2

Common viral causes of URTI

Answer 2

• Rhinovirus
• Coronavirus
• Respiratory syncytial virus (RSV)
• Influenza virus
  + others
  (widespread infection)

Question 3

Pharyngitis

Answer 3

= tonsillitis

• May involve soft palate, uvula, tonsils
• May have cervical lymphadenopathy
• ~50% due to virus (often no therapeutic implications)
• ~50% due to S. pyogenes (often potential therapeutic implications)

Question 4

Pharyngitis clinical features - S. pyogenes

Answer 4

S. pyogenes:

• More severe (fever, pain, dysphagia)
• Focal pharyngeal infection (red pharynx)
• No cough
• Tonsils red, swollen, exudate
• Swollen cervical lymph nodes

Question 5

Pharyngitis clinical features - common viruses

Answer 5

Common viruses:

• Less severe illness
• Diffuse (rhinorrhoea, hoarse voice, conjunctival signs)
• Cough
• Tonsils and cervical lymph nodes normal

Question 6

Criteria for S. pyogenes pharyngitis

Answer 6

Temp >38 = 1
Absence of cough = 1
Swollen, tender ant cervical nodes = 1
Tonsillar swelling or exudate = 1
Age 3-14yrs = 1
Age 15-44 = 0
Age 45 or older = -1

Predicts risk of S. pyogenes e.g. 4 is 50%

Question 7

Bacteria in mouth

Answer 7

• Streptococci
• In some people streptococci comprises 60% of bacteria, in other <10%
• Only streptococcus pyogenes causes illness

Question 8

Haemolysis of blood

Answer 8

Partial haemolysis (alpha, green) = S. pneumoniae + others (viridins strep - S. mutans, S. sanguis)

Complete haemolysis (beta, clear) = S. pyogenes (group B, C and G streptococci)

No haemolysis (gamma) = enterococcus faecalis ( + other non-haemolytic streptococci)

Question 9

Lancefield serotyping

Answer 9

• Streptococci grown on agar plates
• Rabbit injected with dead streptococci to produce antibodies
• ABs isolated and tested with streptococci sample
• Agglutination = positive

Question 10

Treatment of streptococcus pyogenes

Answer 10

= Group A (beta haemolytic) streptococcus - GAS

• Asymptomatic colonisation of pharynx in 16% of population
• Groups predisposed to rheumatic fever: mainly around 10y/o, Maori and Pacific, family history
• Always treat predisposed group even if asymptomatic
• Regardless of whether GAS present in throat should not be treatment if chance of rheumatic fever is very low
• Repeated episodes of infection due to different M types
• 100% susceptible to penicillin (most to erythromycin)

Question 11

Sinusitis aetiology

Answer 11

• 90-98% viral (rhinovirus, influenza, parainfluenza)
• 2-10% bacteria (S. pneumoniae, Haemophilus influenzae)
• Can be confirmed by sinus aspiration (>10^4 bacteria/ml)
• Despite this sinusitis 5th most common reason for antibiotic prescription

Question 12

Rhinosinusitis

Answer 12

• Purulent nasal discharge
• Nasal congestion/obstruction
• Facial congestion/fullness
• Facial pain/pressure
• Reduced or absent smell
• Fever

Question 13

Typical course of viral URTI

Answer 13

• Fever for 2-3 days at onset
• Cough for 7-10 days (usually improving by 5 days)
• Rhinorrhoea that progresses from clear to purulent to clear over 1-2 weeks