gram postiive Flashcards
what are the 2 major branches of gram positive cocci ?
Streptococci and Staphylococci
how to differentiate between
Streptococci and Staphylococci
both gram positive cocci
but staphylococcus is in purple clusters
and streptococci is in purple chains
name 2 of the important staphylococci
these are gram positive clusters
S. aureus
S. epidermis
what is streptococci classification based on? (3)
Haemolysis
Lancefield typing
Biochemical properties
what colour does beta haemolytic streptococci make the agar plate go and why?
full Haemolysis - produces strong enzymes which completely break down blood (complete lysis) making the agar become….
transparent
what colour does alpha haemolytic streptococci make the agar plate go and why?
Partial haemolysis - goes green
this is because enzymes produced by bacteria only partially break down the RBCs on the blood agar
what colour does gamma haemolytic streptococci make the agar plate go and why?
lack of haemolysis
no change observed
what is Lancefield grouping based on?
bacterial carbohydrate cell surface antigens
what strep is in lancefild group A?
S.pyogenes
what are the 3 main streptococci to remember?
S.pyogenus
S.pneumoniae
virdans group
S.pyogenes
- what is it?
= beta haemolytic type A lancfield strep (gram postive)
S.pyogenus
- what is its virulence factors?
Enzymes streptokinase which breaks down clots
Erythrogenic toxin → can lead to scarlet fever
S.pyogenes
- what infections does it cause?
Strep throat
Skin and soft tissue infections
Scarlet fever
A few rare Complications of strep disease
S.pneumoniae
- when does it cause problems?
Hangs around in peoples throats normally but if it invades elsewhere can cause problems
invades if u r at risk eg.HIV
S.pneumoniae
- what infections can it cause?
pneumonia, sinusitis,meningitis
S.pneumoniae
- what is it?
alpha haemolytic strep (gram postive)
virdans group
- which are these ?
alpha haemolyitc strep that are resistant to optochin test
virdans group
- whiat infections do they cause?
mouth infections
deep organ abscesses
name a member of the virdans group
S.oralis
how do you identify S. aureus
from the other staphylococcus?
Staph. Aureus – coagulase positive
eg. s.epidermidis - coagulase negative
Staph aureus
- how is it spread
aerosol and touch
name a type of staph aureus that is very antibiotic resistant
MRSA
Staph aureus
-what infections can it cause
pus infections eg. impetigo (pyogenic)
toxin mediated diseases eg. food poisoning
virulence factors of S.aureus
Pore forming toxins
Proteases
Toxic shock syndrome toxin
Protein A
S. epidermis and other coagulase negative staph
- where do they tend to live?
on skin
S. epidermis and other coagulase negative staph
- when/what kind of infections do they tend to cause?
Don’t tend to cause infection, only opportunistic eg. a big hole in the skin, Knee replacements (prostheses)
name S.epidermis main virulence factor
forms biofilm
name the 3 key gram positive aerobic bacilli (rods)
Corynebacterium
Bacillus
Listeria
where is listeria monocytogenes found and who is advised to stay away from it?
opportunist, found in stinky cheese, pregnant women are advised not to eat soft cheese
Bacillus anthracis
- what can it form which makes it very easy to spread (and why is was suggested for biological warfare)
forms spores
Corynebacterium diphtheriae
- what does it cause
diptheria, upper resp infection
name the 3 key gram positive anaerobic bacilli (rods)
clostridium
propionibacterium
name a type of clostridium and what disease it causes
C.tetani - tetanus
C.botulinum - botulism
C.dificile - diarrhoea
