Salmonella Flashcards
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
Systemic dissemination of invasive Salmonella from gastroenteritis:
What are the 3 forms of Salmonella infection in farm animals, pets, and poultry?
- SILENT: chronic carrier state mainly in adult gallbladder, mesenteric lymph nodes, tonsils, macrophages, and fibroblasts, where the host will shed Salmonella silently in their feces for months or years to infect others or cause relapse (SUBCLINICAL)
- ENTERITIS: gut (enteric) form with enteritis (colic), diarrhea, dehydration, and Salmonella shedding in the feces
- SYSTEMIC: typhoid form that can spread
What can activate clinical disease in Salmonella carriers?
stress of
- surgery
- transport
- crowding
- deprivation of feed/water
- overfeeding
What are 8 common signs of the systemic (typhoid) form of Salmonella infection?
- respiratory disease - pneumonia
- myocarditis
- meningoencephalitis
- septicemia
- dry gangrene (feet, tail, ears)
- mastitis
- reproductive disease - abortion
- joint and wing (poly)arthritis
What causes the dry gangrene as a result of the systemic (typhoid) form of Salmonella infection?
blood supply to tissue is cut off, causing the area to become dry, shrink, and turn black; linked to S. dublin infection
What are the main signs of Salmonella infection in humans, pets, and goats?
HUMANS: gastroenteritis
PETS: diarrhea, vomiting, fever, weakness, shock, vaginal discharge
GOATS: gastrointestinal disease and abortion by S. abortusovis
What are the main signs of Salmonella infection in horses?
abdominal pain, cramp, rolling, overexcitement, kicking, confusion, unease, colic + abortion by S. abortusequi
How are younger and older chickens differently affected by Salmonella infection?
YOUNG: viscous white diarrhea that is usually pasted at the anal region
- S. pullorum
OLDER: watery to mucoid yellow diarrhea with anemia/pale shrunken combs and wattle
- S. gallinarum (fowl typhoid)
What are the 6 major tests/techniques used to diagnose Salmonella infection?
- Gram stain negative/rod
- oxidase negative
- MacConkey agar - lactose negative, yellow/no change
- H2S gas on TSI
- motility positive
- urease negative
What are the main 2 reasons that antimicrobial treatment for Salmonella infection is controversial?
- cure rate of treatment is low as sick animals are often overwhelmed by surge of septicemia, toxemia, and acidosis (calves, foals)
- treatment of Salmonellosis by antimicrobials may have risk of inducing carrier status
When is antimicrobial treatment commonly recommended for Salmonellosis?
early stage of the course of the disease
- calves: ceftiofur, trimethoprim-sulfadoxine
- foals: gentamycin, ampicillin, trimethoprim-sulfonamide
- pig: chlortetracycline, sulfamethazine
What medicine is used to reduce Salmonella shedding or carriage?
sodium chlorate/nitrate
What treatment is agreed on by all veterinarians for Salmonellosis?
supportive fluid and electrolyte therapy
- reverse acidosis and lost electrolytes using 5% acidosis and lost electrolytes
- maintenance therapy mixing isotonic saline, isotonic sodium bicarbonate, and potassium chloride
What are 5 major ways that Salmonella infection is controlled and prevented?
- clean up animals feces to disinfect waste storage, houses, tools, and utensils
- hand washing and sanitization after toilet and animal handling
- improve feed/food hygiene, storage, and cooking
- detect and isolate infected aimals
- cull/treat carriers and sick animals
What vaccines are available for Salmonellosis? Why is vaccine production so difficult?
- LAV against poultry-specific servars (S. gallinarum and S. pullorum)
- killed vaccine of S. enteritidis is licensed in Europe
broad spectrum of different Salmonella serotypes —> 1500 serotypes in S. enterica subspecies enterica I alone
