E. Coli & Related Organisms

Question 1

What are major serotypes of E. Coli and what are the antigens for?

Answer 1

O serotype - side chain of LPS

H serotype - flagellin

Question 2

What is ETEC?

Answer 2

Enterotoxigenic E. coli

Question 3

What is EPEC?

Answer 3

Enteropathogenic E. coli

Question 4

What is EHEC?

Answer 4

Enterohemorrhagic E. coli

Question 5

What is EAEC?

Answer 5

Enteroaggregative E. coli

Question 6

What is ExPEC?

Answer 6

Extraintestinal E. coli

Question 7

What are the clinical symptoms of ETEC?

Answer 7

Watery diarrhea (travelers!)

Question 8

What are the virulence factors of ETEC?

Answer 8

Pili (aka Colonization Factor Antigens)
Heat-labile enterotoxin
Heat-stable enterotoxin

Question 9

What other toxin is the heat-labile enterotoxin of ETEC similar to?

Answer 9

Cholera toxin
Works in same way (ADP ribosylated of G protein -> adenylate cyclase -> increased cAMP -> PKA -> phosphorylates CFTR -> chloride pumped out and water follows)

Question 10

What is treatment for ETEC?

Answer 10

Oral rehydration

Shorten duration with fluoroquinolone

Question 11

What is clinical presentation of EPEC?

Answer 11

Watery diarrhea and vomiting in infants in developing countries

Question 12

What are virulence factors for EPEC?

Answer 12

Bundle-forming pillus
Attaching and effacing Type III secretion system on LEE pathogenicity island
- Tir and intimin

Question 13

What is treatment for EPEC?

Answer 13

Breast feeding is protective
Oral rehydration
Antibiotics not effective

Question 14

What is clinical presentation of EHEC?

Answer 14

Watery, bloody diarrhea
Hemorrhagic colitis
Hemolytic-uremic syndrome

Question 15

How is EHEC transmitted?

Answer 15

All comes back to cattle!

Question 16

What are the virulence factors of EHEC?

Answer 16

Shiga toxins

Attaching and effacing Type III secretion system on LEE pathogenicity island

Question 17

What is the mechanism of Shiga toxin?

Answer 17

Depurinates 28S rRNA, stopping protein synthesis

Cell death occurs and forms clots on cell

Question 18

Why can’t you give antibiotics to treat EHEC?

Answer 18

INCREASES SHIGA TOXIN PRODUCTION

Induces an SOS response that causes phage production and therefore toxin production

Question 19

What category of E. Coli does O157:H7 fall into?

Answer 19

EHEC

Question 20

What is the difference between typical v. atypical EPEC?

Answer 20

Atypical does not have bundle forming pilus

Question 21

What is the treatment for EHEC?

Answer 21

Avoid uncooked cattle things

DO NOT GIVE ANTIBIOTICS

Question 22

How can O157:H7 be diagnosed?

Answer 22

MacConkey sorbitol agar plate, O157:H7 will not ferment on the plate but other strains will

Question 23

What is clinical presentation of EAEC?

Answer 23

Diarrhea with mucous (also travelers)

Associated with growth retardation

Question 24

What are virulence factors of EAEC?

Answer 24

Pili (aggregative adherence)

Cytotoxins

Question 25

What is clinical presentation of ExPEC?

Answer 25

Most common cause of UTI in sexually active women | Can cause Neonatal meningitis

Question 26

What are virulence factors of ExPEC that causes neonatal meningitis?

Answer 26

K1 capsule S fimbriae Cellular invasion

Question 27

What is the treatment for ExPEC neonatal meningitis?

Answer 27

3rd generation cephalosporins (Ceftriaxone, Ceftazidime)

Question 28

What is clinical presentation of Klebsiella?

Answer 28

Pneumonia | UTI

Question 29

What is treatment for Klebsiella?

Answer 29

Treat based on resistance, usually sensitive to cephalosporins But always resistance to penicillins!

Question 30

How do Klebsiella, Enterobacter and Serratia appear when plated?

Answer 30

Encapsulated and mucoid

Question 31

What is treatment for Enterobacter and Serratia?

Answer 31

Has inducible resistance to cephalosporins!! Don't use them even if it says sensitive!! Use penicillin, carbapenem, fluoroquinolone

Question 32

What is clinical presentation of Proteus?

Answer 32

UTIs, espec with catheters

Question 33

What are virulence factors of Proteus?

Answer 33

Urease (causes stone formation and protease stays in stone) | Swarming motilty

Question 34

What is treatment for Proteus?

Answer 34

Usually sensitive to penicillins | But unusual among GNB since resistant to tigecycline and polymixin!