Gram Positive Bacteria Flashcards
What does coagulase mean? - why is coagulase advantageous
Enzyme produced by bacteria that clots blood plasma – fibrin clot formation around bacteria protect from phagocyotsis
Give an example of coagulase +ve spp
S. aureus
What are coag. negative spp. important in? example?
Opportunistic infections
Staph epidermis/ staph saprohyticus
Give example staph.aurues - what is problem?
MRSA
Important resistant - PETG - penicillins, erythromycin, tetracycline, gentamicin
What are virulence factors of staph. aureus?
Pore forming toxin
Proteases
Cytokine release - cause TSS
Protein A - surface protein bind Ig’s wrong direction
What is a biofilm?
3D community - mass of bacteria usually heterogenous
Found adhered to surface and encase polysaccharide matrix
Explain haemolysis
Uses blood on agar to diagnose STREPTOCOCCI
Alpha haemolysis = partial –> greening (s. intermedius)
Beta = complete haemolysis - clear zone agar around colonies (s.pyogenes)
None = no lysis (s.mutans)
Ways diagnosing streptococci?
Haemolysis, lancefield typing, biochemical properties
Lancefield grouping - what is it?
Based on cell surface antigens - antiserum added to suspension - clumping indicates reaction
A-H and K-V
Infections cause strep. pyogenes?
Wound infection, tonsillitis, impetigo, scarlet fever, rheumatic fever
Virulence factor s.pyogenes
Enzyme
Hyaluronidase for spreading
Streptokinase - break down clot
C5a peptidase
Toxin
Streptolysin O+S
Surface Factor
Capsule
M protein - encourage complement degradation
Virulence strep. pneumoniae?
Capsule - antiphagocytic
Inflammatory wall constituent - teichoic acid bound peptidoglycan
What is a viridian streptococci and what do they cause?
Oral streptococci - role in dental caries and abscesses
Role infective endocarditis
How diagnose gram +ve staphlococcus
Clusters than can be diagnosed coagulase test
How diagnose gram +Ve streptococci
Chain that can be diagnosed w/ haemolysis
