Upper Respiratory Tract Infections Flashcards
Why is it important to learn about URTI?
Most common infections in humans and medical consultations. They are also most important reason for inappropriate antibiotics.
What causes pharyngitis?
Rhinoviruses
Coronavirus
Parainfluenza and influenza virus
Adenovirus (Commonly associated with pharyngo-conjunctival fever which causes eyes to become more red and runny nose and sore throat)
RSV
EBV
How are viral infections of the URT different to bacterial infections?
Bacterial infections are associated with pus
Which bacteria are associated with pharyngitis?
Streptococcus pyogenes
Arcanobacterium haemolyticum
Mycoplasma pneumoniae
Vincents angina
Haemophilus influenzae
Corynebacterium diptheriae
What is the most common bacterial cause of pharyngitis?
Streptococcal pharyngitis caused by streptococcus pyogenes (Group A beta haemolytic strep).
Why is it difficult to distinguish strep from other viral infections?
Only 2/3rds of people have typical features.
What are coryzal symptoms?
Unwell feeling associated with the flu/viral infections.
What are symptoms associated with Group A strep (strep pyo)?
Constitutional symptoms
Abrupt onset sore throat and fever >38c
Mucosal erythema, exudate on tonsils.
Tender cervical/tonsillar lymph nodes +/- rash
Examples of alpha haemolytic strep:
Strep. mitins
Strep. mutans
Strep. salivarius
What type of bacteria are strep agalactae?
group B beta haemolytic
What percentage of strep throat are associated with scarlet fever?
<10% strep throats
What investigations can be done for an URTI?
Throat swab (cultured but organism can be missed in 5 - 10% of cases and it may identify carriage only.)
Serology (anti-streptolysin O titre which must be investigated later)
Blood test (atypical lymphocytosis suggests EBV)
What can be done with a throat swab which helps arrive at a diagnosis?
Culture
Rapid antigen tests
How good is a throat swab for diagnosis?
It has a sensitivity of 90 - 95%.
When should blood tests be conducted for URTIs?
They should be deferred for the future and if there is no improvement they can be conducted
What are the complications of Group A Strep (GAS)?
Peritonsillar abscess (Usually unilateral swelling and medial displacement of tonsilllar tissue) and often mixed with anaerobes. If this occurs there may be need for surgical drainage.
Should antibiotics be given for GAS infections?
No unless they experience suppurative complications or if indigenous due to risk of RHD.
What antibiotics should be given if someone must be given antibiotics for GAS infection? What precaution must be taken?
Macrolides (Erythromycin, azithromycin)
Do not give amoxycillin or ampicillin (if it is EBV it can cause a rash and can cause allergy to beta lactam risk)
What causes epiglotitis commonly?
Haemophilius influenzae capsular type B (this is rare due to immunization)
What are the clinical features of epiglotitis?
Common in children (2 - 4)
Common cold like symptoms during prodromal period
Sudden onset high fever and sore throat
Usually bacteraemic at presentation.
Dysphagia prominent and drool
What precaution must be taken when investigating epiglotitis?
Do not try to visualize larynx, it can cause condition to get worse suddenly.
How should epiglotitis be treated?
Antibiotic therapy - Ceftriaxone or amoxycillin
How does diptheria cause damage?
Bacterium adheres to mucosa, releases exotoxin (2 subunits A and B which are very potent. This condition has local and systemic effects:
Local effects induce formation of necrotic tissue membrane (pseudomembrane)
Systemic effects include myocardial toxicity and neurotoxicity.
What are the 3 clinical forms of diphtheria?
Nasal
Pharyngo-tonsillar
Laryngeal