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MD1 SF3 - EXAM 2 > Escherichia coli > Flashcards

Escherichia coli Flashcards

1
Q

General information about E. coli?

A

Gram-negative

In the Enterobacteria family:

  • reduce nitrates —> nitrites, ferment glucose

In soil, water, on plants, in digestive flora of humans and animals (mostly intestines)

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2
Q

Tableaux clinique:

A

Infections intestinales in developing countries

Infections extra-intestinales in industrialized

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3
Q

What is the morphology of E. coli?

A

gram negative, taille moyenne, bouts arrondis, mobile, non sporulé

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4
Q

How is E. coli cultured?

A

32C-40C

Milieux peu complexes

Milieux sélectifs et différentiels:

  • Gélose MacConkey —> sels biliaires et le crystal violet inhibe les Gram +, lactose
  • Aérobie, anaérobie facultatif
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5
Q

How is the paroi of E. coli structured?

A
  1. Structure rigide
  2. LPS (endotoxine) dans le feuillet externe
  3. Paroi de peptidoglycans
  4. Membrane cellulaire
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6
Q

What is the structure of the LPS on E. coli?

A

Lipid A —> core —> chaînes polysaccharidiques (antigène O)

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7
Q

What is lipid A?

A

Part rich in glucosamine and other part that is toxic and responsible for “choc endotoxine”

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8
Q

What is the core?

A

repeated sequence of polysaccharides, mostly similar in most gram - bacteria

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9
Q

What are the chaînes polysaccharidiques?

A

Ag de surface O, used for identification of strain

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10
Q

What are the biological effects of endotoxins?

A

Toxic for mammals:

  • action directe: hémolysine
  • action indirecte: recognized by the immune system

small quantities —> fever

large quantities —> hypotension, marginalization of PMNs and platelets (disseminated vascular coagulation)

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11
Q

What are entérotoxines?

A

Diarrhea acquired in the tropics

Plasmid is tranferable

Toxines ST et LT

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12
Q

What is toxine ST?

A

Heat-stable toxin:

  • Survives at 100C for up to 30 minutes
  • Only works on enterocytes
  • Leads to secretion of liquid
  • Anti-absorbing action
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13
Q

What is toxine LT?

A

Heat-labile toxine

  • Destroyed by 30 mins at 65C
  • Similar to cholera toxin
  • Causes Cl secretion (water and Na… follow passively)
  • Create important liquid and electrolytic loss
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14
Q

What is vérotoxine (shiga-toxine)?

A

Intefere with protein synthesis

Lyse renal and intestinal endothelial cells (#1 cause of insuffisance rénale aiguë in children and can cause ischemia by thrombosis of small vessels)

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15
Q

Other toxins: (3 main types)

A

Hémolysines, hémagglutinines, leucocidines

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16
Q

E. coli antigenic profil and nomenclature:

A

Antigen H: flagella

Antigen O: antigène polysaccharidique

  • ex: E. coli O:157 H:7
17
Q

How to UTIs work?

A

Urine is normally sterile

Principal pathogens: E. coli, K. pneumoniae, Proteus/Entérococcus

18
Q

What is considered a bactériurie significative?

A

>10^8 bacteria/litre

19
Q

What is considered a bactériurie asymptomatique?

A

>10^8 bacteria/litre but asymptomatic

20
Q

What is the two different forms of pathogenesis of UTIs?

A
  1. Voie ascendante
  2. Voie hématogène
21
Q

How are UTIs treated?

A

Antibiotics and prophylaxis

22
Q

What is cystitis?

A

inflammation of the bladder, usually caused by a bladder infection

Signs and symptoms:

  • Dysuria, pollakiuria (benign idiopathic urinary frequency), nycturia, mictional urgency, macroscopic hematuria, no systemic sx
23
Q

What is pyelonephritis?

A

inflammation of the kidney, typically due to a bacterial infection

Signs and symptoms:

  • Fever, chills, dysuria, pollakiuria, increase in frequency of urination, urgency, pain in kidney area (flank)
24
Q

What is septicemia?

A

Serious bloodstream infection:

25
Q

Where can septicemia originate?

A
  1. skin, genitourinary system, respiratory system, digestive system (bile ducts, intestines, etc.)
  2. can be acquired in the community
  3. maladie nosocomiale (particularly in resistant strains to antibiotics)
26
Q

What is the pathogenicity of septicemia?

A

Colonization and infection of foreign bodies

Bris de peau et des muqueuses

Obstruction

Abcès

27
Q

How is septicemia dx and tx?

A

How is it diagnosed?

Clinic, hemoculture, culture du site d’origine suspecté

How is it treated?

Antibiotics, removal of foreign bodies, draining abscess, treatment of shock to maintain BP

28
Q

What is E. coli meningitis?

A

Neonatal meningitis after infection to group B strep

  • Meningitis during cranial trauma or secondary to septicaemia
29
Q

What is an infection entérique causée par E. coli? ( 5 kinds)

A
  1. ETEC (enterotoxinogen)
  2. EPEC (enteropathogen)
  3. EIEC (enteroinvasive)
  4. EHEC (enterohemorragic)
  5. EAEC (enteroadherent)

Production of toxins —> non-inflammatory

  • Invasion and destruction of the muqueuse
    • Shigella
    • E. coli entéroinvasif
    • Salmonella typhi
30
Q

What is travellers diarrhea?

A

50% of cases due to E. coli

2 toxins: LT and ST

Secretion of water into the luminal surface of the small intestine

31
Q

Signs and sx of traveller’s diarrhea:

A

Incubation:

  • ETEC: a couple hours - 2 days
  • Other etiologies: 4-14 days (shigella, Campylobacter, Salmonella)
  • 1-5 days

Abdominal cramping

Diarrhea (no bleeding)

Absence of systemic signs

32
Q

How is traveller’s diarrhea dx and tx?

A

Dx:

Clinic, no routine lab testing

Treatment:

Oral rehydration, Lomotil/Imodium, Bismuth Subsalicylate, NO ANTIBIOTICS

33
Q

What are the signs and sx of E. coli entéroinvasif?

A

Fever and abdominal cramping

Ténesme (tension douloureuse, dans la région de l’anus ou de la vessie, avec sensation de brûlure et envie constante d’aller à la selle ou d’uriner)

Bloody stool

5-7 days

34
Q

How is E. coli entéroinvasif dx?

A

Dx in clinic

Lab: No routine, serogrouping

35
Q

How is E. coli entéroinvasif tx?

A

Rehydration and antibiotics

36
Q

What is E. coli entérohémorragique?

A

Children and old people, due to minced meat, raw milk, contaminated water

What is it?

  • Toxin that inhibits protein synthesis
    • Bacteriophage
    • Production of toxins that increase with stress —> lysis of E. coli cells
  • Death of cells in muqueuses and endothelial cells
    • SHU (syndrome hémolytique urémique) —> most frequent cause of ARI in children
    • PTT (purpura thrombocytopénique thrombolytique) —> ischemia by thrombosis of small vessels
37
Q

What are some signs and sx of E. coli entérohémorragique?

A

Abdominal pain, aqueous diarrhea —> hemorragique, no fever, 7-8 days

7-10 days later: anuria, oligurie, lethargie, convulsions, coma, death 5%

38
Q

How is E. coli entérohémorragique dx and tx?

A

Dx:

  • Recherche de E. coli O157:H7 (less than 50% of cases)
  • Recherche de la vérotoxine (détection d’ADN)
  • Culture doit distinguer de la shigelle qui possède la même toxine

Treatment:

Rehydration, complications (renal and cerebral), NO ANTIBIOTICS

MD1 SF3 - EXAM 2 (12 decks)

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