gram positive bacteria Flashcards
what are the 2 major gram positive cocci
streptococci
and
staphylococci
how do gram positive cocci grow
in clusters (staphylococcus)
in chains (streptococcus)
how to treat staphylococcus aureus
flucloxallin 3 months
what is coagulase
enzyme produced by bacteria that clots blood plasma.
Fibrin clot formation around bacteria may protect from phagocytosis.
how many species of staphylococci
at least 40
normal habitat of staphylococcci
nose and skin
how is staphylococcus aureus spread
by aerosol and touch
- carriers and shedders
virulence factors for staphylococcus aureus
- Pore-forming toxins (some
strains)
• a - haemolysin & Panton-Valentine Leucocidin
– Proteases
• Exfoliatin
– Toxic Shock Syndrome toxin (stimulates cytokine release)
– Protein A (surface protein which binds Ig’s in wrong orientation)
what is MRSA resistant to
B lactams
gentamicin, erythromycin,
tetracycline
2 types of coagulase negative staphylococci
S epidermidis
S saprophyticus
describe S epidermis
Infections in debilitated, prostheses (opportunistic)
– Main virulence factor -
ability to form persistent biofilms
describe S saprophyticus
Acute cystitis
haemagglutinin for adhesion
urease
what do you look at after identifying whether bacteria is in chains or clusters
haemolysis on blood agar
what is B haemolysis
complete clearing/lysis of blood agar around the bacteria
what is A alpha
only a bit of clearing on blood agar around the bacteria (partial clearing)
there is a green tint to it
what is sero grouping
only applies to B haemolysis
classifies them
based on the carbohydrate expressed on cell surface antigens
2 types of B haemolytic sero grouping
group A - S pyogenes - important pathogen
group B - S agalactiae- neonatal infections
virulence factors for S pyogenes
exported factors - enzymes and toxins
surface factors - capsule and M protein
infections caused by S pyogenes
wound infections
tonsillitis and pharyngitis
otitis media
impetigo
scarlet fever
complicates - rheumatic fever & glomerulonephritis
what is black on an chest x ray
air
what is white on a chest x ray
gunk that shouldnt be there
signs of streptococcus pneumonia
cough
severe pain in chest
rust coloured sputum
causes of S pneumonieae
pneumonia
otitis media
sinusitis
meningitis
predisposing factors for S pneumonia
impaired mucus trapping
hypogammaglbulinaemia
asplenia
virulence factors for S pneumonia
capsule
inflammatory wall constituent
cytotoxin
describe alpha haemolytic vidridans group streptococci
can cause dental caries and abscesses
important in infective endocarditis
case deep organ abscesses
3 gram positive bacilli
listeria monocytogenes
bacillus anthracite
corynebacterium diptheriae
3 types of clostridia (gram positive bacilli0
c tetani
c botulinum
c. difficile
describe clostridia
spore forming
survive in environment
produce toxins
how do gram positive stain
Gram positive bacteria retain the colour of the crystal violet stain in the gram stain (because they have a cell wall composed of a thick layer of peptidoglycan).
They stain purple.
3 classifications of streptococci
Haemolysis
Lancefield typing
Biochemical properties
what is lancefield grouping
a method of grouping catalyse negative, coagulase negative bacteria based on bacterial carbohydrate cell surface antigens
what arw the important gram positive bacteria
S.aureus, S.epidermis, S.pyogenes, S.pneumoniae, viridans streptococci, C.diphtheriae
how are gram psoitive bacteria spread
aerosols, surface-to-surface contact, colonization of prostheses
how to manage gram psoitive bacteria
antimicrobials and vaccination
