M7- infections of the upper respiratory tract Flashcards
what are the evolutionary groupings of streptococcus?
- Oralis /mitis
- anginosus
- pyogenic
- mutans
- salivarius
- bovis
what is a pyrogen?
agent that causes raise in body tissue
What are the main group of streptococcus responsible for infections for the upper respiratory tract?
pyogenic
Where do streptococcus pyogenes live?
oropharynx
what is the upper respiratory tract defense?
– Mechanical washing
– Cough response
– Mucocilliary clearance
– Mircobiota/flora
Name infectious organisms.
– Bacteria
– Viruses
– Fungi
what is a normals sore throat?
viral pharyngitis
What happens when your sore throat is colonised by group A streptococci?
strep throat
what are complications of strep throat?
rheumatic fever
what can pharyngitis progress to?
tonsillitis
what are the symptoms of a viral cause of a sore throat?
– absence of fever
– Conjunctivitis
– Coryza
– Cough (uncommon in GAS)
What are the symptoms of a bacterial cause of sore throat (strep throat)?
– Sudden onset (1-5 days post exposure) – Sore throat/ pain on swallowing – Fever – Patchy discrete Tonsillar exudates – Tiny red spots on soft hard palate – Tender enlarged anterior cervical nodes
what is a severe form of strep throat with an associated rash?
scarlet fever (destruction of peripheral blood vessels)
what toxins does scarlet fever have?
pyrogenic/erythrogenic exotoxins
what is impetigo (GAS skin diseases)?
highly contagious through contact with discharge on the face. Infection immediately below surface
what is a deeper skin infection in the dermis?
cellulitis
How does necrotising fasciitis occur?
Invasive Streptococcus A strains penetrate mucous membrane and develop in lesion
what happens in necrotising fascitis?
rapidly destroys connective tissue
what is acute streptococcal gingivitis?
Infected Gingivae red/swollen/oedematous
-Often follows sore throat
Describe toxic shock like syndrome.
GAS disease which is a complication of invasive infections and it results in hypotension to organ failure
what response does superantigens cause?
Massive release of cytokines & inappropriate immune response
name some GAS (pyogene diseases).
- Impetigo, cellulitis
- Acute streptococcal gingivitis
- Necrotising fasciitis
- Toxic shock like syndrome
Name a superantigen associated with toxic shock.
TSST-1
Describe features of rheumatic fever.
• Young School Age Children (5-15).
• 1-4 weeks after sore throat/scarlet fever
• Delayed reaction due to inadequate recovery
from GAS
what is post streptococcal glomerulonephritis (PSGN)?
inflammation of glomurulus (kidney)
what cause PSGN?
-Deposition of Ag-Ab complexes in the glomeruli
• Type III Hypersensitivity reaction
• Damage to Glomerular basement membrane
Where does M protein bind to?
Fibronectin
& specific binding sites
What is used to classify streptococci?
haemolysis
what does Beta haemolytic look like on blood agar plates?
clear/sharp zone
what does streptococci look like?
Gram +ve spherical or oval cocci in pairs or chains
how is group A further subdivided?
according to M protein antigens
what is M proteins involved in?
adhesion and evading immune system
What is M proteins phagocyte properties?
antiphagocytic
what does the M protein bind?
Complement control protein
– Binds Fibrinogen (HV region)
- Prevents 3b binding and Opsonisation via the alternate complement pathway
what does M protein assist in?
colonisation and microcolony formation
what does protease cleave?
immunoglobulins
what enzymes destroy tissues?
- Haemolysins
- DNase A, B, C, & D
- Hyaluronadase
- Streptokinase
what factors are involved in tissue penetration/spread?
- M protein
- Fibronectin binding protein
what is the function of these factors?
- Stimulates Internalisation
- Hide from Macrophages
- Persist in the presence of Antibiotics
What antibiotics can be used in treatment?
- penicillin (10 day course)
- Amoxicilli (narrow spectrum acceptable to children)
- Erthromycin (patients sensitive to penicillin)
how sensitive is GAS to antibiotics?
GAS still relatively sensitive to antibiotics but erythromycin resistance growing
what are the early and late symptoms of rheumatic fever?
Early - fever, joins pain, nose bleeds, abdominal pain,vomiting
Late- pancarditis
