Salmonella Flashcards
(39 cards)
Salmonella shares all characteristics that were described in Enterobacteriaceae. What are 5 unique characteristics?
- lactose non-fermenter
- urease negative
- produces hydrogen sulfide (rotten egg smell providing black colonies
- motile by pertrichous flagella
- no hemolysis (gamma)
What 2 species of Salmonella are non-motile?
- S. gallinarum
- S. pullorum
(devastating in poultry)
What are the 2 media widely used for culturing Salmonella? What 2 selective media are used?
- MacConkey agar (yellow, no color change)
- eosin methylene blue agar
- brilliant green agar
- Salmonella and Shigella agar
What 2 enrichment media are used for injured Salmonella isolation? What bacterial growth does it inhibit?
- tetrathionate broth
- selenite cysteine broth
coliforms (CEEK)
Where is Salmonella a commensal part of the environment? What is one exception?
digestive tract of mammals, birds, reptiles, amphibians, fish, and invertebrates
S. typhimurium is part of the normal flora of reptile and amphibian skin
How is Salmonella transmitted? How does it enter and exit hosts?
oral-fecal transmission
ENTRY: ingestion of bacteria with water, feed, or food (eggs, milk, meat, fish)
EXIT: feces
What species of Salmonella is not excreted fecally?
S. pullorum undergoes trans-ovarian transmission to next generation of poultry
What antigen do S. gallinarum and S. pullorum lack?
H antigen —> non-motile = no flagella
What antigens contribute to the diversity of Salmonella serotypes?
LPS = O antigen
flagella = H antigen
What 2 species of Salmonella are the 2500 serotypes classified into? What subspecies is responsible for 99% of disease?
- S. enterica
- S. Bongori (cold-blooded animals)
S enterica —> enterica I
What are the 3 categories of S. enterica (subspecies enterica I)?
- HOST SPECIFIC: specialists affecting only 1 host
- HOST ADAPTED: prefer 1 host, but can affect others
- GENERALISTS: no selection of preference - can affect multiple species*** (Salmonella serovars)
What 2 Salmonella enterica do not have zoonotic potential?
S. gallinarum and S. pullorum —> do not affect mammals, specialized to attack birds
(all the rest are zoonotic)
What are the top 3 serotypes of Salmonella that affect humans>
- S. typhinurium*
- S. newport
- S. enteritidis*
What 3 Salmonella cause the top 7 priority diseases of the National Poultry Improvement Plan (NPIP)? What is done if a flock is infected with these species?
- S. pullorum
- S. gallinarum
- S. enterica var enteritidis
ban any shipment from a poultry farm or hatchery if infected —> all must be inspected and tested to be free from Salmonella
What caused a major Salmonella outbreak relating to wild songbirds?
songbirds can carry Salmonella while looking healthy and clean and spread/transmit it to other animals and humans
In what 2 places can Salmonella pathogenicity islands (SPI-1 and SPI-2) be found?
- virulence plasmids
- Salmonella genome
What 4 body structures for adhesion and binding contribute to the virulence of Salmonella?
- fimbriae (pili) - adhesion and invasion of gut and conjugation for horizontal transfer
- 5-10 flagella - motility, adhesion, H antigenic variation
- capsule - adhesion, antibody/ complement/phagocyte protection
- LPS endotoxin (lipid A) - adherence, intestinal colonization, inflammation, fever, blood vessel damage that leads to ischemic necrosis in S. dubin
What 2 enzymes are used as invasins to contribute to Salmonella virulence?
- catalase - protects against host ROS
- superoxide dismutase - protects against host ROS
What codes for toxins produced by Salmonella? What 6 toxins will be produced?
Salmonella pathogenicity island (SPI-1, SPI-2, and other SPIs)
- type 3 secretion systems
- adhesins
- invasins
- hemagglutinins
- exotoxins - enterotoxins, cytotoxins (salmonolysin/hemolysin)
- siderophores - rob iron from host cell and transport it into bacteria
(overall drug resistance)
What are plasmids necessary for?
production of virulence factors for systemic diseases and drug resistance (β-lactamase)
What are the 4 major steps of Salmonella infection and pathogenesis?
- ATTACHMENT & ADHESION: LPS, fimbriae, adhesins and flagella allow for the attachment of Salmonella onto host cells and biofilm formation on the surface
- INTRACELLULAR INVASION: T3SS injects bacterial proteins and invasins into host cells
- MULTIPLY WITHIN SALMONELLA CONTAINING VESICLES: SCV forms in the cytosol, Salmonella releases proteins to lyse the vacuole, T3SS induces multiplication, and host actin filaments are deposited around Salmonella
- Salmonella lyse the cell and spread to others
(INTRACELLULAR PATHOGEN - can avoid immune system)
What 2 types of proteins are responsible for intracellular invasion of Salmonella? Intracellular multiplication and spread?
- T3SS-1: syringe-like apparatus on bacterial surface used to inject virulence/effector proteins into host cell
- EFFECTOR PROTEINS (SopE1/E2, SopB, SipA/B: allow for invasion and penetration into host cell cytoplasm via membrane ruffling and micropinocytosis, disruption of fluid, and electrolyte metabolism
- T3SS-2: transfer effector proteins required for intracellular survival and multiplication
- EFFECTOR PROTEINS (EigD, SpiC): preventions of phagolysosome formation with the vacuole containing Salmonella
What is required for Salmonella pathogenesis? Where does Salmonella primarily infect and what does it cause?
uptake of intracellular pathogen into the epithelial cells of the GI tract
cecum and proximal colon in adults, leading to enterocolitis with limited systemic translocation
Where can Salmonella hide while waiting for infection? When will it cause disease?
- mesenteric lymph nodes
- gallbladder
- tonsils
- macrophages
- fibroblasts
weakened immune system activated during stressful conditions
