MIID - MICRO - VIDEO LECT Gram Negative Bacilli: Salmonella, Shigella (Nash)

What are the two major categories of Salmonella?

Typhoidal Salmonella and non-typhoidal Salmonella.

What is a key characteristic of Shigella dysenteriae?

It produces Shiga toxin.

How can you differentiate E. coli from Salmonella on MacConkey agar?

E. coli is a lactose fermenter (pink colonies), while Salmonella is a non-lactose fermenter (white colonies).

What does the presence of blood in diarrhea often indicate?

It suggests an invasive bacterial infection.

What type of diarrhea is associated with Salmonella?

Inflammatory diarrhea.

What laboratory test can distinguish between Salmonella and Shigella?

The H2S production test on SS agar.

What does non-motile mean in reference to Shigella?

It does not have flagella and cannot swim.

What key feature allows Salmonella to be motile?

Salmonella has flagella.

What is a major pathogenic mechanism used by Salmonella?

Type three secretion system to inject effectors into host cells.

What should be considered as a high-risk population for severe Salmonella infections?

Immunocompromised individuals.

What can internalization of Salmonella inside macrophages lead to?

Systemic infections and potential sepsis.

Where is the typical reservoir for non-typhoidal Salmonella?

Animal-associated strains (e.g., poultry, reptiles).

What differentiates Salmonella Typhi from non-typhoidal Salmonella?

Typhi is human-only and has a specific capsule antigen (VI antigen).

Which type of Salmonella is crucial for typhoid fever epidemiology?

Salmonella Typhi.

What are common symptoms associated with Salmonella infection?

Fever, abdominal pain, and diarrhea.

What virulence factor is responsible for Shigella's ability to cause severe colitis?

Shiga toxin.

How does Shigella dysenteriae affect the host's cells?

It cleaves the host ribosome, halting protein synthesis.

What type of immunity is essential in fighting a Salmonella infection?

Cell-mediated immunity.

What is crucial for distinguishing between colitis caused by Shigella and gastroenteritis caused by Salmonella?

The presence of severe pain and blood in stools in Shigella infections.

What kind of toxin does Shigella produce?

AB type toxin (Shiga toxin).

How does Shigella spread within the body following infection?

Actin polymerization propels it from cell to cell.

What organ is commonly involved in typhoid fever?

The liver, leading to hepatitis.

What is a typical feature of Shigella infections in daycares?

High fecal-oral transmission due to close contact.

What is a common cause of outbreaks related to Shigella in the U.S.?

Food handling by an infected carrier.

What is the impact of proton pump inhibitors on Salmonella infection susceptibility?

They can increase susceptibility by raising stomach pH.

What clinical presentation often accompanies Shigella infection?

Dysentery with bloody diarrhea and fever.

What does the absence of flagella indicate about Shigella?

It is non-motile.

What laboratory test indicates the presence of Salmonella in a culture?

Black precipitate on H2S production agar.

How do non-typhoidal Salmonella and Shigella appear microscopically?

Both are gram-negative rods.

What role do neutrophils play in Salmonella infection?

They contribute to inflammation and the symptoms experienced.

What recommendation is critical for preventing Salmonella infection in high-risk populations?

Proper cooking and handling of poultry.

What are reactive arthritis symptoms post- Salmonella infection?

Joint pain occurring weeks after infection without bacteria present.

What is the significance of anti-LPS antibodies in infections?

They can indicate an immune reaction against Gram-negative bacteria.

What conditions can arise from Shigella dysenteriae infections?

Hemolytic uremic syndrome and potential kidney damage.

How does Salmonella gain internalization within intestinal epithelial cells?

Through actin polymerization facilitated by its type three secretion system.

What is a common symptom of typhoid fever?

Cyclic fever with involvement of multiple organs.