Part I - Streptococcus pyogenes Flashcards
List the viruses and bacteria that can cause pharyngitis and tonsillitis
streptococcus pyogens
adenovirus
what are Tonsils?
= lymphoid tissue at entrance of oral cavity part of defence mechanisms. Size
of a marshmallow
Infection of pharynx vs infection of tonsils
Though often occur together
* Caused by same micro-organisms
the virus that account for majority of infection?
adenovirus
Streptococcus pyogenes
Gram-positive (i.e. dark blue or purple)
Cocci (i.e. round)
In chains (short or long).
Characteristic Gram stain appearance of
streptococci.
what does pyogenes mean?
means pus forming
beta-haemolysis.
Growth on blood agar showing small colonies of bacteria (round white bumps)
surrounded by zone of haemolysis, where toxin from bacteria has caused lysis
(bursting) of red blood cells in agar, so agar becomes translucent/transparent
Important structures attached to cell wall of S. pyogenes?
- have Lancefield group A antigen: differentiates group A strepto.. from other .
- M-protein
- capsule made of hyaluronic acid.
SMASHED”
Streptolysins
M protein
Anti-C5a peptidase
Streptokinase
Hyaluronidase and Hyaluronic acid capsule
Exotoxin
DNAses
What are 2 main sites of streptococcal infection?
skin and pharynx( tonsils)
What are the typical symptoms and signs of streptococcal tonsillitis?
pain in the throat
Hay fever
swollen tender draining regional lymph node
they look red, and swollen with yellow spots of pus visible.
Absence of other viral-like upper respiratory symptoms.
What is ‘follicular’ tonsillitis?
What is ‘follicular’ tonsillitis?
Streptococcal tonsillitis is sometimes called ‘follicular tonsillitis’.
The yellow-white patches on the surface of the tonsil are actually small collections of
pus in tiny follicles on surface of tonsil (a tiny little sac or depression)
Bit confusing since follicle also used in many other anatomical contexts.
Hair follicle
Ovarian follicle
Suggest don’t use term follicular- old fashioned and unnecessary.
what is a follicle?
small secretory cavity or sac
Streptococcal skin infections
- Typically through breaks in skin
- Cuts, bites, wounds, burns
- Can be minor/hardly visible
- Mild to severe and life-threatening
- Impetigo
- Cellulitis
- Necrotising fasciitis
a condition of superficial with clear yellow crusts. it very contagious.
impetigo
cellulitis
common bacterial skin infection that causes redness, swelling and pain in the infected area of the skin.
Necrotizing fasciitis
infection of the facia causes necrosis
it spreads very quickly in the body and can cause death.
also called flesh-eating infection/ bacteria
Suppurative Complications of S.pyogenes infections
- Suppurative = Pus forming
- Abscesses (collection of pus)
- Swelling of local draining lymph nodes (adenitis)
- E.g. quinsy or peritonsillar abscess forms between tonsil and
the throat wall - Can also get spread from throat
- Locally to respiratory tract – middle ear, sinuses, lungs
- Via bloodstream to other parts of the body
condition that affects heart and heart valves sometimes causing permanent damage.
Rheumatic fever.
somehow reaction to streptococcus pyrogens cross-react with what tissue.
heart tissue
for long term use……….. to prevent streptococcus skin infection.
penicillin prophylaxis
S. pyogenes tox
S. pyogenes produces various toxins
Including pyrogenic exotoxins.
is actually encoded by a bacteriophage.
Acute glomerulonephritis
Acute inflammation of glomeruli in kidney causing (usually) temporary decrease in renal function
* Due to different ‘nephritogenic’ M type strains
* After throat or skin infections
Disease at least partly due to pyrogenic
exotoxins.
scarlet fever- group A strept.
streptococcal toxic shock syndrome
Streptococcal Toxic Shock Syndrome
Produces a toxin that acts as a ‘super-antigen’ stimulating a massive inflammatory reaction
Leads to shock and multi-organ failure
Partly due to characteristics of infection and maybe partly due to host immune response
Very rare
Sometimes associated with necrotising fasciitis
