streptococcus pyrogens Flashcards
what gram stain is streptococci?
shape?
what does alpha haemolysis mean?
beta?
gamm?
positive (purple)
cocci chains
partial breakdown of blood - green looking - viridans strep e.g. strep pneumoniae
complete breakdown of blood - microbe uses it to gain iron - goes yellow e.g. strep pyrogens
non haemolytic - no breakdown e.g. entercoccus faecalis
what is the lancefield classification?
what is the sherman classification?
classsifys beta haemoltic strep by serology (cell wall)
e.g. strep. pyrogens is group A
classifies if it is puss forming or not (pyrogenic or not)
example of streptococcus pyrogen virulence factors?
- hyaluronic capsule - inhibits phagocytosis but is similar to connective tissue hylauronate so isnt that good
- M protein - resists phagocytosis by inhibiting activation of compliment pathway - many differnt serotypes of M proteins
- adhesins - helps adherence in colonistion
- hyaluronidase - degrades human hyaluronic acid allowing it to invade
- streptococcall pyrogenic exotoxins - cleaves IgG bound to group A strep - its a superantigen and can lead to scarlett fever
what is streptococcal pharyngitis ?
age?
spread?
clinical features?
what the issue?
strep throat
a sore throat caused by strep pyrogenes
common in 5-15 year olds
spreads via droplets in a crowded space
abrupt onset of sore throat, fever, headache, malaise, tonsilopharngeal exudate
a throat swab will find group A strep
untreated can get M protein antibody which can cause ARF
what is scarlet fever?
Sx?
a complication of streptococcal pharyngitis
the stroptococcal pyrogenic exotoxin (superantigen) allows local or haemotogenous spread
fever, rash, sepsis, jaundice
what are suppurative complications?
examples?
a complication of streptococcal pharyngitis where the infection spreads via puss???? - complication causes abcess??
cellulitis, retropharyngeal abcess, sinusitis, meningitis
what is acute rheumatic fever?
what is acute post streptococcal glomerulonephritis
a complication of streptococcal pharyngitis
often occurs a months after initial infection and is due to M antibodies attacking body parts - autoimmune
it causes inflammtion of heart, CNS and joints
acute inflammation of renal glomerulus secondary to streptococcal pharyngitis
antigen antibody comlexes for in the glormeulus that are attacked by M antibodies - differen to ARF?
what is impetigo?
who is it common in?
what can it lead to?
what is erysipelas?
where is it seen?
what causes it?
a skin infection caused by streptococus pyreogenes-common in 2-5 years
the bacteria colonises then innoculates into the dermis - it commonly causes glomeruonephritis
skin infection from stretococcus pyrogenes that involves the dermis and lymphatics
often is seen on the face and lower limbs
often pharyngitis comes before facial infection
and trauma, skin disease or fungal infction comes beofre lower limb infection
what other skin infectiosn can streptococcus pyrogenes cause?
cellulitis - common in drug users - skin and subcutaneous infection
necrotising fasciitis (flesh eating bacteria) - deeper infection of subcutaneous tissue and fascia
very painful, high fever, fulminant course, high mortality
diagnose with sweep test - fibger will easily move arounf under skin
what is stretococcal toxic shock?
deep tissue infection with strep pyrogenes, bacteraemia, vascular collapse and organ failure
very fast from health to death
group A strep into deep tissue and blood, super exotoxin stimulates T cells inducing cytokines
M protein fibrinogen complex formation ?
