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Veterinary Bacteriology & Mycology > Escherichia > Flashcards

Escherichia Flashcards

1
Q

What is the structure of Escherichia coli? In what oxygen conditions does it live in? What is it able to ferment?

A

Gram-negative rodes with peritrichous flagella

facultative anaerobes

glucose and lactose —> pink on MacConkey

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2
Q

How does E. coli respond to oxidase and catalase tests?

A

oxidase negative
catalase positive

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3
Q

What is E. coli’s most common habitat? Is it antimicrobial resistant?

A

normally live harmlessly in the intestinal tract of all mammals

yes - β-lactams and fluoroquinolones

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4
Q

What surface antigens are used to serotype E. coli? What 2 serotypes of E. coli are known to be extremely dangerous?

A
  • fimbrial antigens (F)
  • capsular antigens (K)
  • flagellar antigens (H)
  • somatic/LPS antigen (O)
  1. E. coli O157:H7
  2. E. coli O18:K1:H7
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5
Q

What are the main 4 intestinal (diarrheagenic) E. coli and where are they found?

A

SMALL BOWEL
1. enterotoxigenic E. coli (ETEC)
2. enteropathogenic E. coli (EPEC)

LARGE BOWEL
3. enterohemorrhagic E. coli (EHEC)
4. enteroinvasive E. coli (EIEC) - human pathogen

(enteritis + diarrhea)

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6
Q

What fimbrial adhesins are present in Enterotoxigenic E. coli? What is their function?

A

F4*, F5, F6, F41

attachment to the small intestine

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7
Q

What 2 enterotoxins do enterotoxigenic E. coli secrete? What do they do?

A
  1. heat-labile enterotoxin (LT)
  2. heat-stable enterotoxin (ST)

increase cGMP and cAMP levels within small intestine epithelial cells, causing water and electrolytes to secrete from the cell —> watery diarrhea

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8
Q

What pathogen causes neonatal diarrhea? What is the most common host? What are 3 symptoms?

A

enterotoxigenic E. coli

newborn calves, lambs, and piglets within the first week of life (receptors aren’t resistant to ETEC yet)

  1. diarrhea
  2. severe dehydration
  3. death
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9
Q

How is enteric colibacillosis treated? Controlled?

A

enterotoxigenic E. coli —> neonatal diarrhea

  • milk with fluids containing electrolytes
  • feeding ample amounts of colostrum shortly after birth for resistance (antibiotics not recommended)
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10
Q

What pathogen(s) cause post-weaning diarrhea? What is the most common host? What are 3 symptoms?

A

enterotoxigenic E. coli or enteropathogenic E. coli

pigs within 1-2 weeks after weaning

  1. watery diarrhea
  2. loss of appetite
  3. purplish discoloration of the skin
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11
Q

In what 3 ways is post-weaning diarrhea controlled/treated?

A
  1. vaccination
  2. breeding for disease resistance
  3. antibiotics following a susceptibility test
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12
Q

What adhesin is present in enteropathogenic E. coli? How is it able to translocate internal toxins and proteins into host cells?

A

intimin

type 3 secretion system

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13
Q

How does enteropathogenic E. coli cause watery diarrhea?

A

pedestal formation on small intestine epithelium leads to the loss of microvilli and causes attaching and effacing lesions

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14
Q

What surface structures contribute to enterohemorrhagic E. coli virulence? Where does it colonize?

A
  • intimin (ahesion)
  • T3SS
  • attaching and effacing lesions
    (like EPEC)

large bowel (colon)

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15
Q

What toxin is unique to enterohemorrhagic E. coli? What does it do?

A

Shiga toxin - causes hemorrhagic diarrhea and kidney failure

  • EHEC = Shiga toxin-producing E. coli (STEC) = verocytotoxin-producing E. coli (VTEC)
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16
Q

Cattle are the primary reservoir of EHEC E. coli O157:H7, but they remain healthy. Why?

A

Shiga toxins bind to globotriaosylceramides (Gb3) found in the kidneys and intestine of humans, but are absent in cattle

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17
Q

What kind of disease does enterohemorrhagic E. coli cause? How is it able to do this?

A

edema disease in pigs within 1-2 weeks after weaning

Shiga toxin-producing (O138, O139, O141, O147) that binds to Gb4

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18
Q

What are 5 symptoms of enterohemorrhagic E. coli-caused edema disease in pigs?

A
  1. swelling (edema) of eyelids
  2. muscle tremors
  3. unusual squeal or snoring sounds
  4. neurological dysfunction
  5. flaccid paralysis and death within 36 hrs onset of clinical symptoms
19
Q

What is enteroinvasive E. coli? What allows it to colonize the large bowel?

A

flagella lacking intracellular pathogen in the colon

ipaH (invasive) gene and T3SS

20
Q

What are the 2 most common signs of enteroinvasive E. coli infection? What is the most common host?

A
  1. inflammation, necrosis, and ulceration of the bowel
  2. watery to bloody diarrhea (dysentery) with fever

humans —> dogs and cats resistant

21
Q

What are the 4 most common extraintestinal pathogenic E. coli (ExPEC)?

A
  1. septicemic E. coli (SEPEC)
  2. avian pathogenic E. coli (APEC)
  3. uropathogenic E. coli (UPEC)
  4. mammary pathogenic E. coli (MPEC)
22
Q

What type of E. coli causes colisepticemia? What are the most common hosts? How does it cause disease?

A

septicemic E. coli

newborn calves, lambs, and poultry, or immunocompromised animals

invades the bloodstream to cause systemic infection

23
Q

What are 5 virulence factors of septicemic E. coli?

A
  1. serum resistance (necessary to avoid complement and leukocytes in the blood)
  2. fimbrial adhesins
  3. aerobactin iron uptake system
  4. LPS
  5. cytotoxic necrotizing factors (CNF)
24
Q

What are the most common signs of colisepticemia in calves, lambs, and horses/dogs/cats?

A

CALVES: pyrexia, depression, weakness, hypothermia, prostration, meningitis, pneumonia, arthritis

LAMBS: watery mouth disease, death

HORSES/DOGS/CATS: pneumonia

25
Q

What is septicemic E. coli the most common cause of?

A
  • meningitis
  • pneumonia
  • arthritis

able to invade bloodstream and spread

26
Q

What pathogen causes avian colisepticemia?

A

(systemic disease of birds and poultry)
avian pathogenic E. coli
- serotype O1, 2, 18, 35, 36, 78, 111

27
Q

What are the 4 major virulence factors of avian pathogenic E. coli?

A
  1. type 1 (F1) and P fimbriae
  2. LPS
  3. serum resistance
  4. aerobactin iron uptake system
28
Q

What are 4 common signs of avian colisepticemia?

A
  1. septicemia
  2. salpingitis
  3. pneumonia and airsacculitis
  4. egg yolk peritonitis
29
Q

What are 2 common signs of uropathogenic E. coli infection?

A
  1. cystitis
  2. pyelonephritis
30
Q

What 6 virulence factors are present in uropathogenic E. coli?

A
  1. type 1 pili - attachment to uroepithelium
  2. hemolysin A
  3. LPS
  4. CNF1
  5. aerobactin - kidney infection
  6. capsule - kidney infection
31
Q

How is uropathogenic E. coli able to evade host defense and antimicrobials?

A

undergo the formation of intracellular bacterial communities or quiescent intracellular reservoirs

32
Q

What are 4 common conditions in dogs caused by uropathogenic E. coli? Why are females more likely to become infected?

A
  1. cystitis - inflammation of the bladder
  2. pyelonephritis - inflammation of the kidney
  3. pyometra - inflammation of the uterus
  4. prostatitis - inflammation of the prostate

females have shorter urethras, making it easier for the bacteria to reach the bladder

33
Q

Does uropathogenic E. coli have zoonotic potential?

A

YES

34
Q

What does mammary pathogenic E. coli commonly cause? What are the 2 most common sources of infection?

A

infection of the mammary glands of cows and sows —> mastitis

  1. fecal contamination of the skin of the mammary gland
  2. relaxation of the teat sphincter following milking
35
Q

What are the 3 most common pathogens causing mastitis in cattle? What are 3 clinical signs?

A

E. coli, Steptococcus uberis, Staphylococcus aureus

  1. swelling of the udder, pain, redness
  2. fever
  3. reduced milk production and quality
36
Q

What are 2 ways to treat mastitis in cattle?

A
  1. broad spectrum intramammary antibiotic tubes
  2. nonsteroidal anti-inflammatories (NSAIDs)
37
Q

What specimen can be collected for E. coli isolation?

A
  • cervical swabs, vaginal discharge (pyometra)
  • milk (mastitis)
  • urine (cystitis)
  • blood (septicemia)
  • feces (enteritis with diarrhea)
38
Q

How does E. coli grow in blood agar, MacConkey agar, EMB agar, and chromogenic agar?

A

BLOOD: hemolytic
MACCONKEY: pink (lactose and glucose fermentation)
EMB: metallic sheen
CHROMOGENIC: dark blue

39
Q

How does E. coli respond to the IMViC test?

A

indole +
methyl red +
Voges-Proskauer -
citrate -

40
Q

How are ETEC and EPEC strains of E. coli specifically identified?

A

ETEC
- enterotoxin: ELISA
- virulence genes LT, ST, EAST, F4: PCR
- fimbrial antigens: latex agglutination test

EPEC
- urease +
- virulence gene eae: PCR
- histopathological examination: effacement of mucosal surface

41
Q

How are STEC (edema disease), SEPEC, and UPEC strains of E. coli specifically identified?

A

STEC
- clinical and PM findings: bloody/watery diarrhea
- hemolytic on blood agar
- serotype O139 and 141
- virulence genes eae, stx2e

SEPEC
- isolation from blood
- colicin V plasmids for serum resistance

UPEC
- isolation from urine
- type 1 pili (fimH)

42
Q

What is the recommended treatment for E. coli infection? How is infection controlled?

A
  • rehydration + electrolytes
  • antibiotic therapy if infection is severe or systemic

~ feeding colostrum after birth
~ reduce stress during weaning
~ hygiene
~ vaccines for enteric disease in piglets and mastitis in dairy cows

43
Q

E. coli summary:

A

Veterinary Bacteriology & Mycology (47 decks)

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