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Infectious Agents > E. Coli Enteric Diseases > Flashcards

E. Coli Enteric Diseases Flashcards

1
Q

ETEC is primarily a disease of ______ and ______

A

Calves; pigs

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2
Q

ETEC has _____ fimbrial types

A

5

- F4, F5, F6, F18, F41

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3
Q

F4

A

Genes on a plasmid

  • expressed on swine ETEC
  • associated with O groups
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4
Q

F5

A

Found on cattle, sheep, swine

  • plasmid-encoded “O” groups
  • often have capsules
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5
Q

F6

A

Associated with swine ETEC, sometimes cattle

  • “O” groups
  • plasmid-encoded
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6
Q

F18

A

Common fimbrial adhesion associated with swine ETEC

  • 2 closely related antigenic variants F18ab (edema disease) and F18ac (ETEC)
  • plasmid encoded
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7
Q

F41

A

Cattle ETEC, sometimes swine

  • some F5 strains also have F41
  • chromosome encoded
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8
Q

Intestinal epithelial receptors for fimbriae are responsible for ________

A

Age susceptibility

  • calves: receptors are transiently expressed in the 1st week of life
  • swine: F4 and F5 receptors decrease with age, F4 receptors are abundant in newborns and remain thru postweaning
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9
Q

You need to have both _____ and _____ to cause disease

A

Fimbriae; enterotoxin

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10
Q

Diarrhea results from action of _________

A

Enterotoxins

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11
Q

LT

A

Heat-labile produced by human and porcine strains

  • large protein made up of A and B subunits
  • similar to cholera toxin in chemical structure and function
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12
Q

LT/B vs LT/A

A
  • LT/B: binds to specific ganglioside receptors on enterocytes
  • LT/A: penetrates the cell membrane
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13
Q

Action of LT

A

Causes dysregulation of adenylate cyclase, leading to overproduction of cAMP
- induces loss of water and electrolytes into small intestinal lumen
= diarrhea, hypovolemia, metabolic acidosis, hyperkalemia

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14
Q

What are the 2 types of LT?

A
  • LT1: plasmid encoded, neutralized by anti-cholera toxin antibodies
  • LT2: chromosomally encoded and NOT neutralized by anti-cholera toxin antibodies
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15
Q

ST

A

Heat stable

- low MW proteins with a lipoprotein binding portion

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16
Q

STa

A

Activates guanylate cyclase and causes overproduction of cGMP

  • results in enhanced chloride and water secretion and inhibition of Na absorption in the SI
  • encoded on a transposon
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17
Q

STb

A

Stimulates GTP-binding regulatory protein

  • results in influx of Ca in enterocytes, activating protein kinase C
  • protein kinase C phosphorylates Cl channel proteins, = loss of Cl and water
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18
Q

What is the difference between porcine and bovine ETEC ST production?

A
  • porcine: STa and/or STb is produced

- cattle: STa is the only type produced

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19
Q

EAST1

A

Enteroaggregative E. coli heat-stable enterotoxin 1

- similar to STa

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20
Q

Pathogenesis of ETEC

A

Adheres to enterocytes in SI, multiply, and secrete enterotoxin

  • fluid and electrolytes accumulate in lumen
  • watery diarrhea, with no blood
  • SI has minimal inflammatory changes, but bacteria can be histologically observed
  • multiply to 10^8-10^9 per ml of luminal content
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21
Q

Host factors affecting disease

A
  • age (presence of fimbrial receptors)
  • gastric pH
  • specific antibodies against fimbriae and toxins
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22
Q

Susceptiblity of calves

A

Most commonly less than 1 week of age, but up to 2-3 weeks

  • 1 day old most susceptible
  • most strains are F5 isolates
  • older calves have mixed infections
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23
Q

Susceptiblity of pigs

A

Birth to 12 weeks of age

  • suckling pigs it may or may not be complicated by rotavirus
  • disease is complex in post-weaning diarrhea, but ETEC is majorly responsible
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24
Q

ETEC also causes diarrhea in young ____, _____, ____, and ______

A

Dogs, cats, horses, rabbits

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25
Q

Diagnosis

A

Culture and serotype, or demonstrate fimbriae by ELISA or agglutination

  • culture/demonstrate ST and/or LT by ELISA
  • DNA probes or PCR for fimbriae or enterotoxins (directly from feces)
  • quantitative culturing from SI
  • fluorescent labeled antibodie demonstrates E. coli adhered to intestinal epithelium
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26
Q

High number of E. coli in the ______ is suggestive of ETEC

A

Jejunum

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27
Q

Treatment of ETEC

A

Fluid therapy, oral antibiotics

- cannot use vaccines due to young age of infection!!

28
Q

Prevention of ETEC

A

Depend on transfer of colostral immunity, does not protect against post weaning diarrhea

  • good husbandry
  • vaccines administered parenterally to sows/cows
  • bacterins: one or more serogroups of ETEC prevalent in area containing O, K, and fimbrial antigens
  • fimbrial subunit vaccines
  • monoclonal anti-fimbrial antibodies administered orally to piglets
29
Q

Pathogenesis of EAEC

A

Adhere to intestine in an aggregative, stacked-brick pattern

  • aggregative adherence is mediated by aggregative adherence fimbriae
  • some express EAST1 toxin
  • contain large set of virulence genes regulated by AggR transcription activator
30
Q

Diagnosis of EAEC

A

Gold standard: aggregative adherence to tissue culture cells

  • histopath: presence of bacterial sheets on intestinal eptihelium
  • demonstration of EAST1 and/or AAF genes in isolated E. coli
31
Q

Disease of EAEC

A
  • humans: persistent diarrhea in children and adults

- E. coli with EAST1 or AAF can be isolated from weaned pigs and calves with diarrhea (may or may not have)

32
Q

Do pigs and calves with EAEC have the same virulence factors as human isolates?

A

No

- role of EAEC in pigs/calves is not clear, causation is not established

33
Q

Pathogenesis of EPEC

A

Human EPEC expresses fimbriae called bundle forming pili (Bfp) –> important for initial binding to intestinal cells and bacteria-bacteria interactions = formation of microcolonies of attached bacteria

34
Q

EPEC in animals

A

Only a small fraction of EPEC causing infection in pigs, calves, dogs, and cats produce Bfp

35
Q

Intimin

A

Outer membrane protein that mediates intimate adherence to pedestals

36
Q

EPEC uses a ________ to inject effector proteins into intestinal cells

A

Type 3 secretion system

  • Tir: inserts in the membrane of enterocytes and binds intimin
  • reorganize actin cytoskeleton in enterocytes to form attaching and effacing lesions
  • microvilli are lost (effacing)
  • pedestal structures are formed that bacteria are attached to
  • some proteins dysregulate Cl transport and Na transport = reduced water absorption
37
Q

EPEC disease

A

Watery diarrhea due to loss of absorptive surface (AE lesions) and disruption of electrolyte balance

  • causes diarrhea in all animal species and humans
  • major cause of diarrhea in young rabbits
38
Q

EPEC diagnosis

A

Biopsy and detection of AE lesions

- detection of genes for intimin (eae) from isolated E. coli

39
Q

_____ is similar to EPEC in what aspect?

A

EHEC

  • both produce attaching and effacing lesions in the intestine by the same mechanism
  • target large intestine cells
40
Q

How is EHEC different from EPEC?

A

EHEC produces Shiga toxin

  • AB toxin
  • B: binding
  • A: cleaves adenine residue from 28S rRNA of 60S subunit of ribosomes = shuts down protein translation!!!!
41
Q

Stx1

A

Identical to Stx of Sigella dysenteriae

- Stx1 and Stx1c

42
Q

Stx2

A

More distantly related to Stx of Shigella

- Stx2, Stx2c, Stx2d, Stx2e, Stx2f

43
Q

Stx1 and Stx2 are carried by ________

A

Lysogenic bacteriophage

44
Q

How does Stx have both local and systemic effects?

A
  • local: damages endothelial cells directly underneath enterocytes = hemorrhage
  • systemic: endothelial cells in kidney and brain
  • -> humans: HUS, hemolytic-uremic syndrome
45
Q

EHEC virulence plasmid

A

Encodes an enterohemolysin and other virulence genes

46
Q

EHEC diarreha

A

Caused by same mechanism as EPEC, and damage to endothelial cells
= causes additional fluid and tissue leakage

47
Q

EHEC disease in cattle

A

Intestinal disease in newborn to 12 wk calves

  • 1-8 wk olds, peaks at 4-5 wks
  • low mortality rate, but reinfection is possible
  • dehydration and weakness cause decreased growth rate
  • localized and diffuse hemorrhages in LI
  • no systemic effects
48
Q

Adulterants in beef

A 
O157:57
O26
O45
O103
O111
O121
O145
49
Q

AIEC

A

Associated with Crohn’s disease in humans

  • etiologic role in dogs with histiocytic ulcerative colitis
  • -> young boxers, with chronic bloody diarrhea, mucoid diarrhea, tenesmus, weight loss
50
Q

AIEC target cells

A

Adhere to and invade enterocytes

  • invade macrophages under epithelial layer and multiply in vacoules
  • infected macrophages release TNF-alpha = inflammation and tissue damage
51
Q

Edema disease

A

Weaned pigs caused by STEC

  • subq and subserosal edema caused by damage to endothelial cells
  • caused by Stx2e
  • express F18ab fimbriae
52
Q

Edema disease characteristics

A

Damage to endothelium causes vascular leakage, thromboses = edema and infarcts

  • neurologic signs, edema of subcutis of forehead and eyelids, subserosal edema of stomach
  • sudden death
53
Q

Diagnosis of STEC

A

Detection of Stx genes

- demonstration of toxic activity on cell culture

54
Q

ExPEC

A

Extraintestinal pathogenic E. coli

  • cattle, swine, horses (primarily neonates due to inadequate colostrum)
  • invasion thru ingestion, improperly treated umbilicus, conjunctivae
55
Q

ExPEC pathogenesis

A

Intestinal adherence mediated by fimbrial adhesin (CS31A) and by F17c

  • after intestinal invasion, multiplication occurs in lymphatics and blood
  • endotoxemia, and death
56
Q

ExPEC virulence factors

A
  • Vir plasmid: carries genes for F17c and siderophore aerobactin
  • capsule: K1 with sialic acid, outer membrane proteins to mediate serum resistance and escape from phagocytosis
  • alpha hemolysin
57
Q

ExPEC clinical signs

A
  • fever
  • depression
  • sometimes polyarthritis
  • meningitis
  • bronchopneumonia
58
Q

UPEC

A

Uropathogenic E. coli

  • urethritis, cystitis, ureteritis, prostatitis, pyelonephritis
  • transient members of normal intestinal flora
  • ascending infection from urethra to the bladder
  • P fimbriae bind receptors in bladder epithelium
59
Q

_____ is the most frequent cause of UTI in dogs, cats, people

A

E. coli

60
Q

APEC

A

Avian pathogenic E. coli

  • aerosacculitis, polyserositis, septicemia in chickens, turkeys, etc
  • found in intestinal microflora of healthy birds, most diseases are secondary to other factors
  • eggs can be infected thru shell invasion = embryonic death
61
Q

Is APEC similar to human ExPEC?

A

Yes

- poultry serve as reservoir for zoonotic infections

62
Q

Virulence factors that are similar between APEC and ExPEC

A
  • F1 (respiratory) and P (organs of chicks) fimbriae
  • aerobactin or enterobactin iron sequestering system
  • K1 capsule
  • hemin uptake system
  • resistance to bactericidal effects of serum and phagocytosis
63
Q

APEC disease

A

Air-exchange regions of lung and airsacs are important sites of entry into bloodstream during initial infection

  • causes septicemia = multiple organ lesions and sudden death
  • chronic disease with debilitation, diarrhea, respiratory distress
64
Q

Pyometra

A

Adherence to endometrium associated with F1 fimbriae

  • similarity to ExPEC and APEC
  • E. coli most common cause
65
Q

What 3 bacteria cause coliform mastitis?

A
  • enterobacter
  • klebsiella
  • E. coli
66
Q

Coliform mastitis

A

Fatal, peracute form of mastitis

  • occurs due to effects of endotoxin absorbed from udder of infected cows/sows
  • gangrenous mastitis in cows and agalactica in sows
67
Q

Laboratory diagnosis

A
  • culture/identification for septicemia, mastitis, pyometra, UTI
  • quantitative culture for UTI if urine collected by voiding or catheter
  • pathogenic and nonpathogenic strains must be distinguished

Infectious Agents (44 decks)

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