Gram Neg Bacilli Flashcards
does klebsiella ferment lactose?
yes
is klebsiella motile
no
what antigens does klebsiella have?
O and K
what infections are caused by klebsiella?
pneumonia, UTI, sepsis, meningitis, diarrhoea
what are the majority of klebsiella infections caused by?
pneumonia, oxytoca
what are two main species of salmonella?
enterica and bongori
are salmonella; lactose fermenting, motile, spore forming?
non lactose fermenting
motile
non spore forming
what antigens do salmonella have?
O and H antigens
what is caused by salmonella enterica ?
typhoid fever
what can typhoid fever lead to?
small intestine perforation
what is salmonella incubated in for enrichment?
selenite broth
what agar is used for salmonella identification?
MacConkey
what tests are performed on salmonella
API20e and serovar testing
what is one of the leading bacterial causes of diarrhea?
shigella
is shigella lactose fermenting, motile, sporing?
non lactose fermenting,
non sporing
non motile
what family is shigella from?
enterobacteriaceae
how many shigella cells cause infection?
100
what agar is used for shigella?
macconkey
what test does not work for shigella
API20E
what is XLD agar?
xylose - lysine - desoxycholate agar
does shigella ferment xylose?
no
what is the inhibitor in XLD agar?
sodium desoxycholate - inhibits coliforms
what does salmonella do to lysine?
decarboxylates it making alkaline pH
what does salmonella and shigella look like on XLD
shigella colourless
salmonella black - H2S
what do red colonies on XLD indicate?
lactose fermenters that do not produce H2S
is salmonella shigella agar differential or selective?
both
what is SS agar a modification of?
DCA agar
what ibhibits gpos and colifrosm in ss agar?
brilliant green. bile salts, thiosulphate and citrate
what is an indicator of sulphide production?
thiosulfate turns black
what carb is in SS agar?
lactose
does proteus ferment lactose?
no
what is a virulence factor of proteus?
urease, flagella - swarming
what are the 4 pathotypes of e coli??
enteropathogenic
enterotoxigenic
enteroinvasive
enterohemorrhagic
what is EPEC associated with?
infant diarrhoea
what is ETEC associated with?
travellers diarrhoea
what plasmid encoded toxins are produced in ETEC?
a) heat labile adenyl cyclase activated
b) heat stable guanylate cyclase activated
what does adenyl cyclase do
produce cAMP and increase water and ion secretion
what does guanylate cyclase do
inhibits ionic uptake from gut
what is EIEC associated with
dysentery
what is EHEC associated with?
vertotoxins 1 and or 2
haemorragic collitis and HUS
what toxin does O157H7 produce?
shiga toxin
how many e coli O157H7 cells cause infection
50
how is O157H7 enriched and isolated?
dynabeads
- enrichment broth and stomacher
- immunomagnetic separation
- magenti beads coated with o157 antibody
- bound ecoli at bottom
what issue does the dynabead system have
not completely specific - false positives
what selective media is used for e coli o175h7 ?
macconkey agar with sorbitol, cefiximes and tellurite
what is a key characteristic of e coli o157h7 from other e coli?
cannot ferment sorbitol
what inhibitors are used in macconkey for ecoli ID?
cefixime (antibiotic) and tellurite inhibits other e coli strains
how does e coli o157h7 appear on macconkey with sorbitol?
pale colonies
example of chromogenic agar?
rainbow agar
what chromogenic agar is used to ID e coli 157h7
rainbow agar
what chromogenic substrates does rainbow agar have?
b galactosidase -blue black
b glucuronidase - red
what colour colonies does o157h7 on rainbow agar
glucoronidase negative
black or grey
what colour colonies non pathogenic e coli on rainbow agar
glucoronidase positive - pink purple blue
what are the antigens
O - somatic - LPS
H - flagellar
K - capsular
do ecoli ferment lactose, spores, motile?
lactose fermenters
non spore forming
motile
e coli oxidase and catalase?
oxidase neg
catalase pos
is macconkey agar selective or differential?
both
what are the inhibitors in macconkey agar?
crystal violet and bile salts
inhibit gram pos
what colour does lactose fermenters grow on macconkey agar
dark pink
what are the agars used for differentiation of gram neg?
macconkey
eosin methylene blue
what is an inhibitor in EMB agar
methylene blue gram pos
how does e coli appear on EMB agar?
green metallic
