Shigella species (S.dysenteriae,S. sonnei)

Question 1

Disease of shigella

Answer 1

Enterocolitis (dysentery).

Question 2

Characteristics of shigella

Answer 2

1_ Facultative gram-negative rods. 2_Nonlactose-fermenting.

3_ Nonmotile, in contrast to Salmonella.

Question 3

Habitat of shigella

Answer 3

Human colon only
⬇️
unlike Salmonella enterica, there are no animal carriers for Shigella.

Question 4

Transmission of shigella

Answer 4

fecal–oral route

Question 5

Pathogenesis of shigella

Answer 5

1_ Invades the mucosa of the (((ileum and colon)))
but does not penetrate farther; therefore, sepsis is rare.
2_ Endotoxin in cell wall.
3Infectious dose is much lower (1–10 organisms) than that of Salmonella.
4The infectious dose of Shigella is low because it is resistant to stomach acid.
5 Children in mental institutions and day care centers experience outbreaks of shigellosis.
6 No chronic carrier state.

Question 6

Toxin of shigella

Answer 6

Endotoxin in cell wall0

Question 7

Infectious dose in shigella

Answer 7

much lower (1–10 organisms) than that of Salmonella.

Question 8

Why the infectious dose of Shigella is low ??

Answer 8

because it is resistant to stomach acid.

Question 9

Children in mental institutions and day care centers experience outbreaks of shigellosis.

((True or false))

Answer 9

True

Question 10

No chronic carrier state of shigella

True or false

Answer 10

True

Question 11

Laboratory Diagnosis of shigella

Answer 11

1_Gram-stained smear and culture. 2_Non–lactose-fermenting colonies on EMB or MacConkey’s agar.
3_TSI agar shows an alkaline slant with an acid butt and no gas or H2S.
4Identified by biochemical reactions or by serology with (anti-O antibody) in agglutination test.
5 Serologic tests for antibodies in the patient’s serum are not done.

Question 12

Shigella on EMB or MacConkey’s

Answer 12

Non–lactose-fermenting colonies

Question 13

Shigella on TSI

Answer 13

alkaline slant with an acid butt and(( no gas or H2S))

Question 14

How to identified species of shigella

Answer 14

Identified by biochemical reactions or by serology with ((anti-O antibody )) in agglutination test.

Question 15

Treatment of shigella

Answer 15

In most cases,(( fluid and electrolyte replacement only)) .

😳In severe cases, ciprofloxacin😎.

Question 16

Prevention of shigella

Answer 16

1_Public health measures (e.g., sewage disposal, chlorination of the water supply, stool cultures for food handlers, and handwashing prior to food handling).
2_Prophylactic drugs not used.
3_No vaccine is available.