Upper respiratory tract infections Flashcards
Where does the upper and lower respiratory tract split?
At the vocal chords
Lower respiratory tract? Sterility?
Is sterile
Host defences in the upper respiratory tract
- Epiglottic reflex - aspiration
- Coughing
- Mucocilliary escalator
- Secretory IgA (can be broken down by gonorrhoea)
How are defences of the upper respiratory tract impaired?
- Tracheotomy
- Alcohol
- Foreign bodies
- Tumour
- Abnormal secretion (CF)
- Endotracheal intubation/ventilation
Pharyngitis
- Inflammation of the pharynx
- Beefy red appearance
- Enlargement of the tonsils
- Can be pusy
- 40% caused by viral infection
- 15-30% caused by group A Streptococci
- Can be caused by: mycobacterium pneumoniae, clamydophilla pneumoniae, corynebacterium diptheriae and neisseria gonorrhoeae
Quinsy
- Lots of pus
- Leads to peritonsillar abscesses
- Treated by removing the tonsils
Streptococcal sore throat
- Must be treated with penicillin or erythromycin or macrolides
- Cause non infectious sequelae
- Causes post- streptococcal glomeronephritis - inflammation of the glomeruli and circulating immune complexes get trapped leading to kidney damage. Develops 10-14 days after throat infection and characterised by blood in the urine and swollen ankles and puffy eyes and feeling tired due to low iron levels
Post-streptococcal glomerulonephritis
- inflammation of the glomeruli and circulating immune complexes get trapped leading to kidney damage. Develops 10-14 days after throat infection and characterised by blood in the urine and swollen ankles and puffy eyes and feeling tired due to low iron levels
- Children are most commonly infected
- Type III hypersensitivity reaction in which IgG antibodies bind to soluble mediators leading to complement fixation
Rheumatic fever
- Type II hypersensitivity - IgG antibodies bind to cell mediated receptors or tissues - indirect complication
- Abs are formed against antigens in the streptococcal cell wall which cross-react with the sarcolemma of the tissues in the heart
- Aschoff’s nodules form in the heart 2-4 weeks after a sore throat
- Leads to carditis, poly arthritis and chorea
Streptococcal sore throat diagnosis
Points for:
- The absense of the sore throat
- Swollen and tender anterior cervical nodes
- Temperature above 38 degrees
- Tonsillar exudates
- 3-4 years old
0=1-2.5% 1=5-10% 2=11 to 17% 3=28 to 35% 4=51-53%
1-3 needs a throat culture and 4 needs antibiotics
Diphtheria
- Corynebacterium diphtheriae (pleomorphic, gram positive bacillus
- Non toxic strains are present in the pharynx
- Toxin destroys epithelial cells and polymorphs
- Ulcer formation which is covered by necrotic exudate forming a false membrane
- Becomes dark and bleeding occurs
- Bull neck
- Nasopharyngeal is the most severe
Diphtheria toxin
Toxin is phage encoded. Gene is known as the TOX gene and is an AB toxin that requires low extracellular iron.
Toxin inhibits protein synthesis as elongation factor 2 is ribosylated
Diagnosis of diphtheria
Isolating it on Hoyle’s medium containing potassium tellurite
Black colonies
An elek plate is often used.
Tracheotomy is often needed
Acute epiglottis
Encapsulated strains of Haemophillus influenzae (Pittman B type)
Infection of the epiglottis by this causes swelling that leads of airway blockage
Life threatening = emergency tracheotomy
Cefotaxine and chloramphenicol used to treat
Hib vaccine has largely decreased the incidence
Acute ottis media
Middle ear infection Highest in 6-24 month old Declines after child reaches 6 Increased risk in children with autoimmune or anatomical defects Earache and pus in the ear Ear drum can rupture Bacterial infection severe - strep pneumoniae, haemophilus influenzae and strep pyogenes Mymgotomy performed
