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
What characteristic feature is seen in diphtheria patients?
Bull neck and pseudomembraner
How is diphtheria treated?
Antitoxin
Penicillin or erythromycin for 14 days
Prophylaxis in family members
(still causes death in 2 - 3% despite the treatment)
What are the clinical features of pharyngitis with vesicles/ulcers?
Fever + skin rash
Shallow mucosal ulcers
Both of these are often seen over soft palate buccal surfaces
What commonly causes pharyngitis with vesicles/ulcers?
Viruses such as herpangina (enteroviruses such as coxsachie A)
Primary herpes simplex virus
What is vincent’s angina?
Known as “trench mouth” it is a pharyngitis that causes halitosis, ulceration, and exudate in tonsils.
How is vincent’s angina treated?
Antibiotics
Which bacteria cause Vincent’s angina?
Borrelia vincenti, anaerobic fusiform bacilli
Who most commonly gets Vincent’s angina?
Teens and young adults
What causes lemierres disease?
Fusobacterium necrophorum which is a bacteria found in people’s mouths normally. It spreads and invades jugular vein and causes clotting of blood in brain and other places.
What is croup? How does it present?
A clinical syndrome caused by several respiratory pathogens (most commonly parainfluenza viruses) which usually presents as a fever, hoarseness (laryngitis), and a barking cough.
What are the clinical features of croup?
Usually mild but can be severe and can cause obstruction and cyanosis.
Inflammatory obstruction of subglottic area.
Laryngitis, laryngotrachietis, laryngotracheobronchitis
What is cyanosis?
A bluish discoloration of the skin due to poor circulation or inadequate oxygenation of the blood.
How is croup treated?
Airway dilators, steroids, moisture (hot showers or steam)
In severe cases intubation may be necessary.
What is sinusitis?
Infection of air filled sinuses of the skull.
Which bacteria can be involved in sinusitis?
Strep pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Anaerobes
What are the clinical features of sinusitis?
Fever and coryzal symptoms
Unilateral facial swelling
Pain
Headache
Blocked nose
Purulent post nasal drip or nasal discharge
How is sinusitis managed?
Antibiotics can be beneficial but not always (unclear that they do anything useful)
Topical intranasal corticosteroids are useful for inflammation.
Surgical drainage can be done in severe and prolonged cases
What are potential complications of sinusitis?
Mastoiditis
Cranial osteomyelitis
Meningitis
Brain Abscess
Orbital cellulitis and cavernous sinus thrombosis
Who often gets chronic sinusitis?
People with allergic disorders
Diabetics
Immunocompromised people
What pathogens can cause chronic sinusitis?
Gram negative bacteria
Fungi
What is otitis media?
An infection of the air-filled space behind the eardrum
How often do people get otitis media?
Most children have one episode and up to 50% have more than 3
Which ethnic groups have a high prevalence of otitis media?
Indigenous Australians
Which bacteria commonly cause otitis media?
Most commonly S.pneumoniae
Gram -ve anaerobes
H.Influenzae
Moraxella catarrhalis
S.pyo
S.aureus
Which bacteria that cause otitis media are 100% resistant to otitis media?
Moraxella catarrhalis
Gram -ve anaerobes
What conditions does otitis media follow?
Viral URTIs
What are the clinical features of otitis media?
Ear pain + fever
Hearing impairment
Discharge through external canal due to perforation of ear drum
What happens during otitis media?
Congestion of the nasopharyngeal mucosa
Inflammatory obstruction of the Eustachian tube at the narrowest point
Followed by fluid trapping and effusion formation in middle ear
Ear drum becomes inflamed and bulging
Overgrowth of nasopharyngeal bacteria in the Eustachian tube/middle ear
Middle ear effusion persists 1-3 months (“glue ear”)
How is otitis media diagnosed?
Clinical history and examination of ear drum
Sample is taken from middle ear fluid and then bacteriological studies (this procedure is rarely done)
What is the treatment for otitis media?
Most cases are self limiting and end within 24 hours.
No point in using nasal decongestants, antibiotics or antihistamines
What communities have highest rate of complications?
Indigenous Australians
What antibiotics are used for otitis media?
Amoxycillin
What are potential complications of otitis media?
Mastoiditis
Labrynthitis
Meningitis and brain abscess
Chronic Otitis Media with effusion
Persistent effusion or perforation of ear drum.
Mild to moderate conductive hearing loss.
Adverse effects on speech and language.
How is chronic OM managed?
Preventing deafness by maintaining aerated middle ear
Antibiotics and decongestants
Surgical management (myringotomy with or without tympanostomy tube or adenoidectomy)
What is otitis externa?
Infection of the external ear canal
What are the symptoms of otitis externa?
Severe pain and/or discharge
Swelling, erythema
Infection is exacerbated by moisture
How is otitis externa treated?
Topical broad spectrum antibiotics/antifungals, usually IV initially
What pathogens cause otitis externa?
Staphylococcus aureus
Streptococcus pyogenes
Candida albicans
Pseudomonas aeruginosa
Proteus species,
Water-borne organisms e.g Aeromonas
