Shigella

Question 1

➢General characteristics of Shigella

Answer 1

● Gram -ve bacilli, member of family Enterobacteriaceae.

● Non motile

● Non-capsulated.

● Non-fastidious.

● Facultative anaerobes

● Oxidase (-ve)

● Catalase (+ve)

● Non-lactose fermenters

● Does not produce H2S (anaerogenic)

● Urease (-ve)

Question 2

Shigella Classified according to O-Antigen to

Answer 2

1. Shigella dysenteriae. (Most virulent -> “Shigella Shiga” because it contains the Shiga toxin.).
2. Shigella flexneri.
3. Shigella boydii.
4. Shigella sonnei. (Least virulent)

Question 3

الناس في الكیس تركز الزول جاي من وین!! في الshigella
اها بتكون كيف

Answer 3

● Most common cause of dysentery in developing countries (Sudan) -> Shigella Flexneri.

● Most common cause of dysentery in developed countries (Europe) -> Shigella Sonnei.

Question 4

➢Virulence factors of shigella and causes diseases

Answer 4

1. Invasion. (the main virulence factor) dysentery
2. Shiga toxin (only produced by Shigella Shiga) causing :hemolytic uremic syndrome.

Toxins:
● Exotoxin: causes bloody diarrhoea.
● Enterotoxin: causes watery diarrhoea.

Question 5

➢Case presentation of Shigella

Answer 5

severe abdominal pain, starts with watery diarrhoea changes to bloody diarrhoea with mucus and no white spots.why 😉

طبعاً لانه الenterotoxin ببدا اول

Question 6

➢Lab diagnosis of shigella

Answer 6

1. Specimen collection:

Stool We put it in buffered glycerol saline, which is a transport medium.

2. Microscopy:

● RBCs and pus cells

● The organism can’t be identified because of the normal flora

3. Culture:

● MacConkey agar: Pale colonies.

● XLD: Pink colonies without black centres (No H2S production).

● Salmonella-Shigella agar: colourless colonies.

4. Biochemical tests:

● Motility test: (-ve) (differentiate it from Salmonella)

● Sugar fermentation: (+ve), without H2S production.

All types of Shigella can ferment Mannitol EXCEPT Shigella Dysenteriae

Question 7

➢Treatment of shigella

Answer 7

● Dysentery:

• Rehydration.
• In severe infection: Ciprofloxacin

● Hemolytic uremic syndrome:

• No antibiotic treatment
• Renal dialysis due to renal failure

Question 8

➢Complications of shigella

Answer 8

● Local complications: peritonitis, hemorrhagic colitis.

● Systemic complications Riter’s syndrome and hemolytic uremic syndrome.في غيرهم بس دا الاهم

Question 9

Hemolytic uremic syndrome Case presentation يلا هنا قولي التعليلات لاي حاجة

Answer 9

● Hemolytic anemia. (Low Hb / pale peripheral blood picture)

● Uremia.

● Thrombocytopenia (Bleeding).

● Acute renal failure (high creatinine / renal dialysis).

● Schistocytes (segmented RBCs)

ممكن تشوفي الشيت للمراجعة

Question 10

Riter’s syndrome Case presentation

Answer 10

● Reactive (=aseptic) arthritis .(Can’t climb a tree).

● Conjunctivitis.(Can’t see).

● Urethritis.(Can’t pee). يادوبك هوي الباقي شوفيه من الشيت 😾😾😾 سريييييع ولا كلمة

Question 11

How shiga toxin work

Answer 11

Inactivate 60S ribosome