LECTURE - Shigella and EIEC

Question 1

T or F. Shigella are flagella

Answer 1

F! non-motile; have the genes (filDC) for them but are cryptic - not expressed

Question 2

Characteristics of Shigella/EIEC

Answer 2

• non-motile
• low infective dose (one of the most infectious of the bacterial intestinal pathogens; about 200 organisms)
• resistant to low pH esp. anaerobically
• bacillary dysentery (invasive disease of the colon)

Question 3

This is genetically indistinguishable from E. coli

Answer 3

Shigella

Question 4

T or F. Humans appear to be the only hosts for Shigella

Answer 4

T! therefore if we eliminate person-person transmission we can eradicate disease

Question 5

These age populations are the most susceptible to outbreaks of Shigella

Answer 5

children <10 y/o and elderly and there also seems to be a seasonal peak in summer in NA (picnics where food left out at warmer than normal temps s organisms can grow, etc.)

Question 6

This bacteria is more lethal than war

Answer 6

Shigella

Question 7

Because Shigella is invasive, antibiotics are helpful and several types are effective:

Answer 7

ciprofloxacin in adults and ceftriaxone and azithromycin in kids

Question 8

Shiga toxin

Answer 8

• S. dysenteriae type 1
• cytotoxin, neurotoxic, and enterotoxic
• HUS as a complication

Question 9

ShET-1 and ShET2

Answer 9

• all S. flexneri 2a strains produce ShET-1
• 3.3% of other Shigella serotypes and no enteroinvasive E. coli serotypes posses gene for ShET-1
• ShET-2 produced by all Shigella spp.; effector protein, injected to target cells by T3SS

Question 10

Sen

Answer 10

• shigella enterotoxin
• 75% of enteroinvasive E. coli serotypes and 83% of Shigella strains
• may contribute to high vol, watery diarrhea seen in initial stages of disease

Question 11

Most severe Shigella serogroup and Least common

Answer 11

S. dysenteriae

Question 12

Least severe Shigella serogroup and most common

Answer 12

S. sonnei

Question 13

Shigella infection spread by 4 F’s

Answer 13

feces, fingers, food (water), and flies

- exacerbated by crowding and poor hygiene

Question 14

This causes a descending infection over several days

Answer 14

Shigella

• small intestine (fever, ab cramping, voluminous diarrhea followed by…
• large intestine (decrease in fever, and smaller vol stools with blood, mucus, and pus (PMNs)

Question 15

T or F. Highest # of Shigella in stools occur early in infection

Answer 15

T! easier to isolate them

- can be shed for 1-4 weeks after symptoms subside

Question 16

S. flexneri pathogenesis

Answer 16

1. invade colonic epithelial layer
   - can manipulate tight junction proteins expressed = paracellular movement of bacteria into sub-mucosa
   - PMN cells recruited by IL-8 &IL-1B create gaps = transmigrate
   - endocytic M cells transcytose bacteria, releasing them into an intraepithelial pocket filled with B and T lymphocytes and macrophages
   …..

Question 17

Shiga toxin

Answer 17

• produced primarily by S. dysenteriae type 1
• cytotoxic, neurotoxic, and enterotoxic
• responsible for the development of HUS as a complication

Question 18

Shigella spp. also produce two enterotoxins

Answer 18

ShET-1 and ShET-2

• all S, flexneri produce ShET-1; only 3.3% of other Shigella serotypes and NO enteroinvasice E. coli serotypes possess the gene
• ShET-2 producd by all Shigella spp.; an effector protein injected into target cells by T3SS