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Bacteria > Enterobacteriaceae (E.Coli-Specific) > Flashcards

Enterobacteriaceae (E.Coli-Specific) Flashcards

1
Q

Describe the general structure of Enterobacteriaceae:

A

Gram negative rods
Many have flagella and a capsule
H and K Antigens
LPS

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2
Q

What are the locations of H and K Antigens in Enterobacteriaceae?

A

H-antigen: located in peritrichous flagella

K-antigen: located in capsule

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3
Q

Function of the capsule in Enterobacteriaceae?

A

Important in causing extraintestinal colonization, UTI, and invasive disease

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4
Q

Describe the composition of LPS in the membrane of Enterobacteriaceae.

A

O-antigen: located on outer most domain
Core oligosaccharide
Lipid A: inner most region of LPS

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5
Q

What is significant about of O-antigen?

A

Targeted antigen for detection in laboratory

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6
Q

What is the pathogenesis of lipid A?

A

Causes toxicity: fever, diarrhea, and possible fatal endotoxic shock

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7
Q

Name the 6 virulence factors of Enterobacteriaceae:

A 
Endotoxin (LPS)
Capsule
Antigenic Phase Variation 
Type III secretion systems 
Sequestration of growth factors
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8
Q

What is the significance of antigenic phase variation in Enterobacteriaceae?

A

Alte expression of H and K antigens to protect organisms from Ab mediated cell death

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9
Q

What is the significance of Type III secretion systems in Enterobacteriaceae?

A

Facilitates secretion of virulence factors into host cells

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10
Q

Morphology of Enterobacteriaceae

A

Gram-negative rods that stain red

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11
Q

Culture Characteristics of Enterobacteriaceae

A

Grow on standard media (i.e. blood agar)

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12
Q

5 Biochemical characteristics of Enterobacteriaceae

A

Facultative (aerobic & anaerobic)

Ferment glucose

Reduce nitrate to nitrite

Oxidase negative

Grow on MacConkey Agar (salt)

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13
Q

What differentiates Enterobacteriaceae from other gram-negative rods?

A

Enterobacteriaceae is Oxidase negative

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14
Q

Non-lactose fermenting Enterobacteriaceae

A 
Salmonella 
Shigella 
Proteus 
Yersinia 
Serratia
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15
Q

Lactose fermenting Enterobacteriaceae

A

E. coli
Klebsiella
Enterobacter
Citrobacter

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16
Q

6 Escherichia Coli Clinical Syndromes:

A

Gram negative bacteremia and sepsis

Most common contributor to community-acquired UTIs

Wound infections

Pneumonia in immunocompromised hospitalized patients

Meningitis in neonates

Gastroenteritis

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17
Q

Pathogenic Phenotype of Enterotoxigenic

E. coli (ETEC)

A

Elaboration of secretory toxins (LT, ST) that do not damage the mucosal epithelium but stimulate hypersecretion of fluids

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18
Q

Signs and Symptoms of Enterotoxigenic

E. coli (ETEC)

A

Profuse, watery, secretory diarrhea is predominant symptom. Often accompanied by mild abdominal cramps. Dehydration and vomiting occur in some cases.

19
Q

Pathogenic Phenotype of Enteropathogenic E. coli (EPEC)

A

Adheres to epithelial cells in localized micro-colonies and causes attaching/ effacing lesions

20
Q

Signs and Symptoms of Enteropathogenic E. coli (EPEC)

A

Usually occurs in infants.
Characterized by low-grade fever, malaise, vomiting, and diarrhea, with a prominent amount of mucus, but with no gross blood

21
Q

Pathogenic Phenotype of Enteroinvasive E. coli (EIEC)

A

Invasion of epithelial cells

22
Q

Signs and Symptoms of Enteroinvasive E. coli (EIEC)

A

Inflammatory diarrhea (Dysentery) similar to Shigella. Hallmarks are fever and colitis. Symptoms are urgency and tenesmus; blood, mucus, and many leukocytes in stool

23
Q

Pathogenic Phenotype of Enterohemorrhagic E. coli (EHEC)

A

Shiga Toxin producing E. coli (STEC) -Carry cytotoxins (Shiga toxins, Stx1 and Stx2). Primarily caused by E.coli O157:H7

24
Q

Signs and Symptoms of Enterohemorrhagic E. coli (EHEC)

A

Bloody diarrhea without WBCs. Often no fever. Abdominal pain is common. May progress to hemolytic uremic syndrome (HUS) or hemorrhagic colitis.

25
Q

Pathogenic Phenotype of Enteroaggregative E. coli (EAggEC)

A

Adhere to epithelial cells in a pattern resembling a pile of stacked bricks

26
Q

Signs and Symptoms of Enteroaggregative E. coli (EAggEC)

A

Infants and travelers. Symptoms include watery diarrhea with blood and mucus, vomiting, dehydration and less commonly, abdominal pain.

27
Q

Two other names for Shiga Toxin Producing E. coli (STEC).

A

EHEC and E.coli O157:H7

28
Q

How is E.coli O157:H7 transmitted?

A

contaminated food or water

direct contact with an infected patient

29
Q

E. coli O157 Reservoir

A

Reservoir in healthy dairy cattle

30
Q

Foodborne outbreaks of E. coli O157 are most commonly associated with ______________.

A

Foodborne outbreaks of E. coli O157 are most commonly associated with undercooked ground beef.

31
Q

Infections caused by E. coli O157:

A

Hemolytic Uremic Syndrome (HUS)

Hemorrhagic Colitis

32
Q

Hemolytic Uremic Syndrome triad of symptoms:

A

acute renal failure

thrombocytopenia - low platelet count

Microangipathic hemolytic anemia - the destruction of RBCs prior to their natural death cycle (shistocytes)

33
Q

Hemolytic Uremic Syndrome is usually preceded by:

A

bloody diarrhea

34
Q

HUS is the leading cause of ________________ in children.

A

HUS is the leading cause of acute renal failure in children.

35
Q

Treatment of HUS:

A

Mainly supportive
Dialysis
No antibiotics
Plasmapharesis/IVIG

36
Q

Mechanism of Hemolytic Uremic Syndrome (HUS) - 3 steps

A
  1. Toxin (STX2) binds to receptors in the intestinal villi and renal endothelial cells
  2. The toxin causes damage to endothelial cells, which leads to platelet activation and thrombin deposition forming a clot at the region of endothelial destruction
  3. Leads to decreased glomerular filtration and acute renal failure
37
Q

Describe the 2 Types of HUS:

A

Diarrheal-related: majority of cases

Non-diarrheal HUS: occurs in association with pneumococcal infection, chemotherapy, or transplant immunosuppression

38
Q

Clinical Presentation of E. coli O157 Hemorrhagic Colitis

A

Abdominal cramps, watery diarrhea, bloody discharge (vomiting in 50%)

Patients progress to bloody diarrhea within 2 days of onset of clinical symptoms of abdominal cramps

No significant fever

Absence of WBC in stool

Symptoms resolve in 4-10 days

39
Q

How would you isolate E. coli O157 from other strains on agar?

A

Sorbitol MacConkey Agar is used because these organisms do not ferment sorbitol

40
Q

How would you detect E. coli O157 from other strains using surface antigens? Describe the process.

A

ProSpecT™ Shiga Toxin E. coli (STEC) Microplate - Remel

  1. Direct fecal specimen detection by placing stool in sample well
  2. If Shiga toxin and/or the O157 antigen are present, the lines will show
  3. LPS antigen is used as a control
  4. Enriched broth culture detection done overnight (more sensitive)
41
Q

How would you isolate E. coli O157 from other strains via toxin/antigen detection method?

A

BioFire FilmArray – Multiplex PCR

Integrated Sample Preparation, Amplification, and Detection for 22 Enteric Pathogens

Detects Shiga-toxin producing E. coli (STEC) stx1/stx2 and/or E. coli O157

42
Q

Treatment of STEC:

A

Oral rehydration (Gatorade, Pedialyte), supportive care, and careful monitoring of kidney function.

HUS and renal failure: managed by dialysis

43
Q

What treatments should be avoided for STEC Diarrhea? Why?

A

Antibiotics and Anti-motility agents NOT given in STEC diarrhea because they will push patients toward HUS

44
Q

Is Treatment of E. coli O157 with Antimicrobial Agents useful?

A

Most strains are very susceptible, but Abx treatment has not been shown to shorten the duration or severity of disease.
Treatment possibly increases the risk of developing HUS

Bacteria (15 decks)

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