Lecture 4 - salmonella

What are two most common species of salmonella? What species do they infect?

1. Salmonella bongori - primarily reptiles

2. Salmonella enterica - multiple species

What is the morphology of salmonella?

-Non spore forming

-Facultative anaerobe

-Rod-shaped

-Gram negative

What tests can you use to detect salmonella?

-Triple sugar iron test and XLD agar (Hydrogen sulfide production)

-Non lactose fermenting

-Oxidase negative

-Indole negative

Which is the most common form of salmonella infection? What antigens do they produce?

-S. enterica subsp. enterica

-Produce O (LPS) and H (flagellar) antigens

What is a serogroup?

Determined by slide agglutination and may suggest a virulence type, host specificity, or host adapation

What is a serovar?

Determined by combination of serogroup and flagella type (multiple serovars in 1 serogroup)

How is S. enterica subsp. enterica transmitted?

-Usually fecal/oral

-Some inhaled resulting in a respiratory tract infection

What areas does Salmonella Enteritidis invade? What species does it commonly affect?

-GIT and ovaries

-Hens

What is difference between typhoidal and nontyphoidal salmonellosis?

-Typhoidal - humans and higher primates only

-Nontyphoidal - many animals

What are the clinical signs of salmonellosis? What can happen if its untreated?

-Enteritis, diarrhea, fever, weakness, and myalgia

-Septicemia if left untreated

-Septic and aseptic arthritis

What are the histological signs of salmonellosis?

-Villus blunting and hemorrhage

-Immune infiltrate

What is the pathogenesis of Salmonella enterica?

-LT-like enterotoxin causing watery diarrhea

-Immune cell and epithelial cell invasion

-Motile - contains flagella and fimbria

What is flagellar phase variation?

Switching between motility types to escape hosts humoral immune response

How does salmonella enterica attach to the host cell?

-Fimbria attach causing pore formation

-Bacteria enter cell then turn off the genes for fimbria

-Able to survive within phagocytic cells

What is T3SS?

-Type 3 secretion system

-Allows for transmission of effector proteins to each specific cell (SipB, SipC, SopA, SopB)

What does SipC effector protein do?

Facilitate invasion of epithelial cells

What does SipB effector protein do?

Mediates invasion of macrophage (may also induce apoptosis)

What are SopA and B effector proteins responsible for?

Inflammation and diarrhea

How do you control/prevent salmonella?

-Good biosecurity

-Vaccines (variable efficacy)

-Supportive care