L9 - Upper Respiratory Tract Infections Flashcards
are there resident microbiota in URT?
YES - complex
are there resident microbiota in the LRT?
Normally sterile
How are the URT and RT divided?
Vocal chords
Name for infection of the alveoli?
pneumonia
What are host defences of the upper airway?
air filtration epiglottic reflex cough mucociliary clearance secretory IgA
What can host defences in URT by impaired by?
Tracheotomy Alcohol foreign body tumour abnormal secretions endotracheal intubation
What % of sore throat infections are viral?
40-80%
What % of sore throat infections are caused by group A streptococci?
15-30%
What are other bacteria that cause sore throat?
M. pneumoniae
C. pneumoniae
C. diptheriae
N. gonorrhoeae
What is the name for the peritonsillar absces?
Quinsy - cavitation filled with bacteria and pus
What drugs treat strep throat?
B-lactam
macrolides
What are the complications of streptococcal infection
NON-INFECTIOUS SEQUELAE
- post-streptococcal glomerulonephritis
- Rheumatic fever
What happens during post-streptococcal glomerulonephritis
acute inflam of glomeruli
trapped immune complexes - hypersensitivity
What happens during rheumatic fever?
Type II hypersensitivity
antibodies raised against M-protein - confuses immune system
molecular mimicry
react with cardiac tissue
chorea
Erythema marginatum
How is streptococcal pharyngitis diagnosed
in the clinic?
scoring
e.g. FeverPAIN, Centor
How is streptococcal pharyngitis diagnosed in the lab?
antigen test throat swab
serology (delays)
What is Diptheria caused by?
Corynebacterium diptheriae
production of EXOTOXIN
What is a key sign of diptheria?
pseudomembrane adhered to throat
can block throat
What does diptheria exotoxin do?
inhibits eukaryotic protein synthesis - EF-2
damages: myocardium, nerve ending, adrenal glands
What are features of the diptheria toxin?
phage-encoded
AB toxin
inhibits elongation factor 2
low extracellular iron required
How is diptheria diagnosed?
culture on blood tellurite agar
toxin detection by: elek test (precipitation lines), enzyme immunoassay, PCR
What is the role of the epiglottis?
prevent food from entering trachea
What is Epiglottitis caused by?
Haemophilus influenzae
What is a consequence of Epiglottitis?
swelling = block airway
