Shigella

Question 1

Shigella Genus info

Answer 1

• Enterobacteriacae, Pathogens of Bacterial Dysentery (shigellosis)
• Feco-Oral transmission, usually dirty hands
• Very low infectious dose (acid-stable)

Question 2

Shigella Species

Answer 2

• S. Dysenteriae
• S. Sonnei (US, EU)
• S. Flexneri
• S. Boydii

Question 3

Morphology

Answer 3

• Gram Negative
• Rods
• Facultative Anaerobes
• Non-motile
• Non-encapsulated

Question 4

Virulence Factors

Answer 4

• Shiga-Toxin by S. Dysenteriae
• Inhibition of protein synthesis by 60S inh.
• Neurotoxin, Cytotoxin, Enterotoxin

Question 5

Pathomechanism

Answer 5

• Shigella penetrate mucosa & epithelial cells of rectum & ampulla
• No penetration before terminal ileum
• Infection kills cells, necrosis, but does not spread beyond lamina propria so no bloodstream

Question 6

Diseases

Answer 6

• Dysentery: Fever, Bloody Diarrhea, Tenesmus
• Hemolytic Uremic Syndrome (HUS) complication, reactive arthritis (due to S. Dysenteriae)

Question 7

Shigella diagnosis

Answer 7

• Cultivation of stool
• EMB agar: lactose negative
• Salmonella-shigella (deoxycholate-citrate) selective agar: colorless colonies
• Hektoin agar grows green (salmonella black)

Question 8

Treatment

Answer 8

• Fluoroquinolones
• TMP-SMX
• 3rd gen cephalosporins
• Water & Electrolyte replacement
• No vaccine