Gram + bacteria Flashcards
what is used as artificial mesia
agar plates
what is the first classification of bacteria
obligate bacteria or
bacteria that may be cultured on artificial media
shapes of bacteria
rods
cocci
spirochaetes
what is ZN stain positive
special stain due to waxy coating found on the bacteria
gram +
purple
thick peptidoglycan layer
(has plasma membrane, pehiplasmicspace, peptidoglycan)
gram -
pink
LPS outer membrane
(plasma membrane, periplasmic space, peptidoglycan, outer membrane)
what is coagluase
enzyme produced by bacteria that clots blood plasma
- fibrin clot formation around bacteria may protect from phagocytois
which species are important in opportunistic infections
coagulase (enzyme which clots blood plasma)
how does staph aureus spread
aerosol and touch
what agar is selective for gram +
mannitol salts agar
what happens with s aureus on mannitol
s aureus ferments mannitol
virulence factors of staph aureus
pore forming toxins
enterotoxin
toxic shock syndrome
protein A
pore forming toxins examples and what they do
a-haemolysin and panton valetine leucodidin
PVL causes haemorrhage pneumonia by inserting into membrane, cell collapse and haemorrhage out
proteases
exfoliatin
breaks down junctions between skin cells
toxin shock syndrome
stimulates cytokine release
host responce
protein A
surface protein which binds IGs in the wrong direction
what is a coagluseae negative staphylococci
staph epidermidis
- opportunistic pathogen
staph epidermis main virulence factor
ability to form persistent biofilms
- difficult to remove sticky ECM
biofilm definition
- mass of bacteria, usually heterogeneous, found adhered to surfaces, encased in extracellular polysaccharide matrix
types of haemolysis
A partial
B complete lysis
no lysis (gamma)
A partial haemolysis
greening
h2O2 reacts with Hb
forms met haemoglobin
what is haemolysis
enzymes breaking open RBC in agar
B complete lysis (haemolysis on the agar plate what happens and what does it look like on the agar)
releases haemolysins O andS
forms circular bands
ways to classifify streptococcci
haemolysis
lancefield typing
what is lancefeild typing (serogrouping)
method of grouping catalase negative bacteria based on bacterial carbohydrate surface antigens
serogrouping and how to test
carbohydrate cell surface antigens 1) A-H 2) K-V antiserum added to each group to a suspension of bacteria clumping indicated recongitin
A and B most important in pathogens A - S pygenes, important pathogen B - S agalactiae - involved in neonatal infections
complications with s pyrogen infections
can lead to
rheumatic fever
glomerulonephritis
rheumatic fever
- inflammatory disease of heart, joints, skin, brain
- often follows strep throat infection
- antibody cross reactivity
glomerulonephritis
- inflammatory disease sometimes following S.pyogenes infection
anti SLO ttire
(allows risk assessment)
Looks for the amount of Anti streptolysin O in the body
- antibody against SLO
SLO
- causes beta haemoloysis
ASLO reacts with SLO to neutralise haemolytic activity
the anti SLO titre is where there is still prevention of haemlysis
- i.e. before it goes red
anti SLO titter rapid test
Clumping reaction
- streptococcal exoenzymes bound to biologically inert latex particles
- if streptococcal antibodies present in the test sample, reaction occurs
- presence of an ASO titre of >200 IU/mL in the serum leads to agglutination of the latex particles
S pyogens virulence factors
erythrogenic toxin
C carbohydrate
M protein (inhibits binding)
Streptolysin O ASO titre
violence factors of S pneumoniae
capsule (antiphagocytic)
IgA protease
cytotoxin (pneumolysin for lysis)
viridian’s streptococci
Collective name for oral streptococci
- alpha or non haemolytic
- some cause caries and abscesses
- optochin resistant
what is used to test of penumoniae
optochin test
how does C diphtheria spread
droplet spread
what can C diphtheria grow in
presence of potassium tellutire
selective method of isolating this bacteria from throats of pts
toxins of C diptheria
- inhibits protein synthesis (inactivates elongation factor 2 in host cells by additn ADP ribosyl group to aa diphthamide)
toxin recognition test
- Toxin recognition (Elek plate) – filter paper soacked in antitoxin which difuses out onto plate, streak samples accorss the middle – if you have toxin in sample it will react with the anti toxin – gives lines when they react
how is c diptheria prevented
vaccine
