Salmonella and Shigella are the two important gram-negative bacteria that do not ferment lactose and cause enterocolitis. How are they differentiated?
Answer: Salmonella produces gas from glucose fermentation, produces H2S, and is motile (can disseminate hematogenously)
Mnemonic:
Salmon require energy (glucose) to swim (motile) and smell bad (H2S)
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Bacteriology
- Describe the diseases caused by each and the species included in each:
- Salmonella species are divided into typhoidal or nontyphoidal types?
- What is the treatment of Shigella and what medications should be avoided?
- What populations are most often affected by Shigella?
- How is Shigella transmitted?
- What symptoms are often seen with shigellosis?
- Why is Shigella nonmotile?
- Why does Shigella only cause superficial ulcers and not invade blood vessels?
- What are the reservoirs for Shigella?
- What are the mechanisms of the two subunits of Shiga toxin?
- What other bacteria besides Shigella contain the Shiga toxin?
- Which is more virulent, Salmonella or Shigella?
- Escherichia coli is the most common cause of UTIs, what is the key virulence factor?
- Who does EPEC commonly affect?
- EPEC adheres to but does not invade intestinal cells and results in flattening of the intestinal villi. What is the consequence of this and how does it present?
- How do patients with EIEC present?
- How do these plasmid-encoded proteins act?
- The main virulence factors of EIEC are encoded by a plasmid shared by what other diarrhea causing bacteria?
- How is EHEC treated?
- How are patients typically exposed to EHEC O157:H7?
- What is the mechanism that causes hemolytic uremic syndrome (HUS)? What are the features of HUS?
- How do patients with EHEC present?
- What toxin mediates EHEC diarrhea? What is the mechanism of action?
- Which other bacterial toxin is similar to LT toxin?
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