Bacteriology - E.coli Flashcards
describe E.coli
facultative anaerobe
non-spore forming
gram - bacilli
specific virulence factors
diarrhea & extra-intestinal pathogenic subtypes
non-fastidious (easy to grow)
what is MacConkey Agar selecive and differential for
selective for gram -
differential for lactose fermentation
Escherichia coli
family
geus
subtypes
Family: Enterobacteriaceae
Genus: Escherichia
Subtypes:
Enterotoxigenic E.coli (ETEC)
Shigatoxigenic E.coli (STEC)
Enteropathogenic E.coli (EPEC)
Enteroinvasive E.coli (EIEC)
Enteroaggregative E.coli (EIAC)
Shigella spp.
Invasive & Adherent E.coli
Extraintestinal Pathogenic E.coli (ExPEC)
diagnostics for E.coli
feces or intestinal contents
culture
PCR
agglutination tests
most common cause of E.coli diarrhea in farm animals?
Enterotoxigenic E.coli
enterotoxigenic E.coli (ETEC)
virulence factors?
fimbriae
enteroxtoxins
when are calves/lambs most suspectible to ETEC
3-5 days
when are pigs most susceptible to ETEC
several weeks after weaning, 3-8 weeks
what fimbriae are associated with swine
F4 (K88)
what fimbriae are associated with calves, swine, and lambs
F5 (K99)
pathogenesis of ETEC
enterotoxins cause secretory diarrhea without inflammation
3 toxins of ETEC and their mechanism
stable toxin a (STa) - active secretion of Cl-
stable toxin b (STb) - indirect, promotes secretion of serotonin & vasoactive intestinal peptide
heat-labile toxin (LT) - active secretion of Cl-
ETEC consequences, prevention, treatment
rapid death due to dehydration –> multiorgan failure and colisepticemia
prevented by colostrum quality/transfer/storage, nutrition, hygiene, calf management, vaccines
enteral/parenteral fluid therapy, bottle feeding, antibiotics
most common shigatoxigenic E.coli in humans
what is its importance in animals
O157:H7
animals are reservoirs
What does STEC cause in swine? in ruminants/dogs?
swine - edema
ruminants/dogs - diarrhea
STEC virulence factors
locus of enterocyte effacement (LEE) + intimin
Stx toxins
hemolysin
acid resistance
importance of Stx2e
causes edema
affects weaner pigs (2-10 weeks)
why are antibiotics are controversial as treatment for STEC
increase stress which will activate the SOS response increasing transcription of stx genes
why are most calves/lambs carriers of STEC and shed it without disease (some cases will have milld diarrhea)
cattle lack Stx receptor on endothelial cells
Enteropathogenic E.coli (EPEC)
affects ____
virulence factors?
results?
affects all animals + humans
LEE (intimin)
cytoskeletal changes occur in enterocytes, diarrhea, mild inflammation
what 3 subtypes cause diarrhea
host defenses?
prevention?
treatment?
ETEC, EPEC, STEC
passive immunity & edema
colostrum management, oral K99Ab and hygiene
fluids, antibiotics sometimes
enteroinvasive E.coli (EIEC) & enteroaggragative E.coli (EIAC) are important in what species
humans
Shigella spp. is important in what species
primates
invasive & adherent E.coli is specific to what breeds?
what does it cause?
how is it diagnosed?
is it contagious?
boxers & french bulldogs
granulomatous colitis
in situ hybridization
not contagious
Extraintestinal Pathogenic E.coli (ExPEC)
species?
infections?
virulence factors?
many. species
urinary tract, mammary gland, colisepticemia
nonspecific VF - LPS, mucoid capsule production, hemolysins, siderophores
what does ExPEC frequently cause? what can this lead to?
Septicemia in neonates
umbilical infections (foals/calves), septic shock or embolization of bacteria to various body sites like joints, bones, eyes (foals)
how can you diagnose ExPEC?
blood culture
antimicrobial susceptibility
IgG measurement
treatment of ExPEC
aggressive IV fluid management for endotoxemia
plasma transfusion if failure of passive transfer
NSAIDs
IV antimicrobial therapy
