3. URTI Flashcards
(33 cards)
What are common bacteria associated with URTI? (>50%)
V. streptococci
Anaerobic microorganisms
H. influenzae
C. albicans
What are occassional residents of URTI? (>10%)
Streptococcus pyrogenes
Streptococcus penumoniae
What are organisms associated with colonisation of URT following antibiotic treatment? (<1%)
Coliforms
pseudomonas sp.
C. albicans - fungi
How do microorganisms become professional invaders?
- adhere to normal mucose
- avoid host surface
- damage to local tissue; production of invasins and exotoxins
What do secondary invaders do?
They cause disease when host defences are impaired.
- post viral infection
-compromised immune response
- foreign bodies
What are upper respiratory tract infections?
- common cold
- oral candidiasis
- sinusitis
- pharyngitis/ tonsilitis
- acute epiglottitis
- otitis (media/externa)
What is the clinical manifestation of a common cold (coryza)?
- incubation period 2-4 days
- nasal discharge, sneezing, sore throat
- lead to laryngitis, tracheitis
- seasonal
What are common organism of coryza?
Viruses: Rhinovirus, RSV(infants), coronavirus
What is the treatment of coryza?
Paracetamol, antibiotics not indicated for common cold
What is the clinical manifestation of oral candidiasis?
- changes in flora upsets balance and causes overgrowth of fungi
- causes raw inflamed mucous membranes, white fungal plaques
What are predisposing factors for oral candidiasis?
- broad spectrum antibiotics
- contraceptive pill
- systemic steroids
- chemotherapy
- immunosuppression - HIV
What is the causative microorganism for oral candidiasis?
Candida Albicans - fungi
What is treatment for oral candidiasis?
- Nystatin or clotrimazole pastilles (1 pastille 4 times a day)
- For HIV patients: fluconazole 100mg (14-30 days)
What are the clinical manifestations of sinusitis?
facial pain localised tenderness and swelling
what are the causative organisms of sinusitis?
usually viral but bacterial infection can occur due to secondary invaders; S.pneumoneae and H.influenzae
What is the treatment for sinusitis?
- no treatment if viral
- amoxicillin 125.200mg, tds, 3-7days
- augmentin for beta lactamase producing bacteria 250mg, 3-7 days
- doxycycline 100mg daily, 3-7 days
- erythromycin 250-500mg, qds
What is the clinical manifestation of pharyngitis/ tonsillitis?
common in children, fever, sore throat, cervical lymphadenopathy; purulent discharge
What are the causative microorganisms of pharyngitis/ tonsillitis?
- viruses; main cause 70% eg. adenovirus
- bacteria; Sterptococcus pyogenes or Neisseria gonorrhoea (rare)
What is the treatment for pharyngitis/ tonsillitis?
- viral; no treatment
- penicillin; 500mg qds
- cephalexin; 500mg qds
- erythromycin; 500mg qds
What are post streptococcal tonsillitis complications?
- peritonsillar abscess (PTA, quinsy)
- rheumatic fever (autoimmune)
- glomerulonephritis (autoimmune)
- scarlet fever (toxin-associated)
What is the mechanism of streptococcal pathogenicity?
- ability to colonise the host and invade tissues
- ability to bypass host defences
- ability to damage host through production of toxins
What are the roles of F-protein and M-protein in adhesion?
F-protein is surface expresses and recognises the host cell fibronectin
M-protein is anchored in cytoplasmic membrane and protrudes fimbrae.
it mediates adherence to epithelial cells.
its highly antigenic.
How does a hyaluronic acid capsule aid evasion of host defences?
- it is identical to human substance, avoiding immune detection
-it binds to cellular hyaluron receptor CD44 mediating adherence and invasion
How do immunoglobulin binding proteins aid evasion of host defences?
they bind to Fc region of IgG and IgA preventing opsonisation
