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Unit 6: Micro > Enteric Bacterial Infections 1: Major Foodborne Enterobacteriaceae > Flashcards

Enteric Bacterial Infections 1: Major Foodborne Enterobacteriaceae Flashcards

(45 cards)

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1
Q

Describe the cellular characteristics of Shigella

A
  • Gram (-) rods
  • Non-lactose fermenter
  • Non-H2S producing
  • Non-motile
  • Facultative
  • Intracellular
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2
Q

What are two other names for Shigella enterocolitis?

A

Bacillary Dysentery and Shigellosis

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3
Q

What is the difference in infectious dose between Shigella and Salmonella

A
  • Shigella - low dose
  • Salmonella - high dose
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4
Q

What human phenotype is associated with reactive arthritis from shigella (and other bugs)?

A

HLA-B27 phenotype

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5
Q

Describe the pathogenesis for shigella infection

A
  • Shigella engulfed by M cells
  • Bacteria survive macros and invade epithelium
  • Bacteria can transfer betwixt adjacent cells
  • Use T3SS to inject exotoxin
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6
Q

What is Shigella virulence dependent on?

A

Plasmid

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7
Q

What virulent genes are encoded on the Shigella plasmid?

A
  • Shiga toxin - Protein synthesis inhibition
  • Shu and Aerobactin - Ironchelating molecules
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8
Q

What are the major virulence factors for Shigella?

A
  • T3SS
  • IcsA - use of host actin to cross into neighboring cells
  • IpaB - induces macrophage apoptosis
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9
Q

What is a major risk of Shigella infection?

A

Hemolytic Uremic Syndrome

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10
Q

What age group(s) is/are affected most severely by Shigella?

A

Very young and old

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11
Q

What are the lab procedures for Shigella Dx?

A
  • Agglutination
  • Methylene BLue stain - fecal sample (determination of presence of neutrophils)
  • Blood smear - detect schistocytes for HUS
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12
Q

In the Tx of Shigella and E. coli, what is a very important consideration?

A

Shigella treat with ABs decrease HUS risk while Tx for E.coli with ABs is controversial

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13
Q

Tx procedure for mild and severe shigella?

A
  • Mild - fluid/electrolytes
  • Severe - Ceftriaxone, fluoroquinolone, azythromycin, cefiximine (NO fluroquins for children)
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14
Q

Describe the antimicrobial assay for Shigella

A
  • Shmear bacteria onto agar
  • Place AB-drenched filterpaper onto agar.
  • Incubate
  • Check zone of clearing with reference table
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15
Q

Describe the bacterial characteristics of E. coli

A
  • Straight Gram(-) rods
  • Facultative
  • Lactose fermentation
  • H2S negative
  • Urease negative
  • Mobile/Nonmobile (depending on strian)
  • Normal GI flora
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16
Q

Describe the use of MacConkey agar in IDing E. coli

A

The agar will turn bright pink because it ferments lactose (pink = lactose fermenter)

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17
Q

What strain of E. coli causes traveler’s diarrhea?

A

Enterotoxigenic E. coli (ETEC)

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18
Q

What type of E. coli causes hemorrhagic colitis/HUS?

A

Enterohemorrhagic E. coli (EHEC)

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19
Q

Describe the pathogenesis of Enterotoxigenic diarrhea

Study These Flashcards
A
  • Pili attach to jejunum/ileum
  • Enterotoxin synthed
  • Enterotoxin causes efflux of ions
  • Host loses fluid - watery diarrhea
20
Q

Describe pathogenesis of Enterohemorrhagic diarrhea

Study These Flashcards
A
  • Bac invade/destroy epi of large intestine
  • Inflamm
  • Bloody diarrhea
21
Q

What gene does O157:H7 E. coli carry?

Study These Flashcards
A

Shigella gene for Shiga toxin

22
Q

Briefly describe the different modes of infection of ETEC, EPEC, EIEC, and EHEC

Study These Flashcards
A
  • ETEC - Fimbriae adhere to cell and deliver enterotoxin
  • EPEC - Attach to cell using actin bundle (pedestal) and inject molecules using injection system
  • EIEC - Endocytosed by M Cell (similar mechanism to Shigella
  • EHEC - Actin bundle + Shiga toxin delivery via injection system
23
Q

What is ETEC? EPEC? EIEC? EHEC?

Study These Flashcards
A

ET - Enterotoxigenic

EP - Enteropathogenic

EH - Enterohemorrhagic

EI - Enteroinvasive

E. coli

24
Q

What two subtypes of E. coli use injection systems?

Study These Flashcards
A

Enteropathogenic and Enterohemorrhagic

25
What strain of E. coli typically causes UTIs?
Uropathogenic
26
What is the virulence factor for uropathogenic E. coli?
P. fimbriae
27
What is a red flag for E. coli Enterocolitis?
Water diarrhea, bloody diarrhea (progression from the former to the latter)
28
What is the culture procedure for E. coli?
Stool sample on **blood agar** and **MacConkey** agar (Pink for E. coli [**lactose fermenter!**])
29
What is AB use associated with in Tx of EHEC?
Increased HUS risk
30
Tx for Uropathogenic E. coli?
* Simple - **Trimethoprim sulfamethoxazole/ampicillin** * Extended - **third generation cephalosporin** (cefotaxime)
31
Cellular characteristics of Salmonella
* Gram (-) rods * **Motile** * Oxidase and urease negative * H2S * **Thousands** of serovars * Acquired from contaminated food
32
Typical size of infectious dose for Salmonella?
Large dose (compared to small dose in Shigella)
33
Describe pathogenesis of Salmonella
* **M cell** endocytoses Salmonella * **a)** Can destroy macrophages and infect epithelium on basal side * Spread thru adjacent cells * **b)** use macros as trojan horses and disseminate causing **typhoid fever**
34
What are the virulence factors of Salmonella?
* **Ipf** - enhances adhesion to M cell * **T3SS** * **SipB** - macro apoptosis
35
What are additional virulence factors for S. typhi?
* **Spi Type 3** - remodels phagosomes for systemic spread * **Vi antigen** - capsule for immune evasion
36
What is the risk of HUS for Salmonella infection?
There is no riskk
37
What is the general mechanism for typhoid fever?
* Salmonella (typhi or paratyphi) invade M cells * Disseminat thru macros * Once **critical density** reached, macros apoptose and escape into bloodstream
38
In what organ does salmonella sequester?
Gallbladder
39
What allele is protective against penetration of the gut?
CFTR cystic fibrosis allele (possibly why the gene has not disappeared from the gene pool)
40
What is a sign on physical exam of typhoid fever?
Rose spots
41
RFs for typhoid fever?
* Corticosteroids * Immunosuppresion * Malignancy * Diabetes
42
PE signs of Salmonella Enterocolitis?
* Nonbloody diarrhea, fever, dehydration
43
In addition to Tx, what should one do once salmonella has been Dx?
**Inform local health authorities!**
44
What are tipoffs of typhoid fever?
Traveling abroad; **Rose spots**
45
Tx for salmonella enteric fevers/septicemia?
Ceftriaxone/ciprofloxacin

Unit 6: Micro (13 decks)

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