Yersinia Flashcards
What 3 species of Yersinia are of veterinary importance?
- Y. pestis (Black Plague!)
- Y. enterocolitica
- Y. pseudotuberculosis
What is the overall structure of Yersinia? How do they characteristically stain? How is the presence of flagella different for each species?
Gram-negative rod
bipolar staining
ABSENT (non-motile, lack H antigen) = Y. pestis
PRESENT (motile) = Y. enterocolitica, Y. pseudotuberculosis
What 2 structures characteristic of Gram-negative bacteria does Yersinia contain?
- T3SS
- siderophores
What fermentation does Yersinia undergo? How does it test on a urease test? Coagulase test?
lactose non-fermenter
urease positive
coagulase positive
How does Yersinia grow in TSI media?
does not produce H2S or other gases (no broken media) - color changes to yellow
How must Yersinia pestis be handled?
needs permission for laboratory handling by US government - bioterrorism agent
In what 4 ways is Yersinia pestis spread?
- flea bites
- meat ingestions of infected rodents (cats and dogs + rats)
- contact with infected secretions or tissue
- aerosol transmission to humans from pneumonic plague-infected humans or cats
What disease does Yersinia pestis cause? How does it present?
bubonic plague (Black Plague)
black death - gangrene that turns affected digits black, coughing up dark sputum
How does serotype diversity compare in the species of Yersinia?
Y. pestis —> homogenous (1 serotype)
Y. enterocolitica —> 70 O serotypes (LPS)
Y. pseudotuberculosis —> 15 O serotypes (LPS)
How has Yersinia adapted to its environment?
Y. enterocolitica is able to proliferate at refrigeration temperatures, making it a common cause of enterocolitis in colder areas of Europe and North America
What is the most common habitat of Yersinia?
GI tract of animals and fleas (Y. pestis)
- primarily animal pathogens, but can be passed to humans through direct or indirect contact
What are the 2 cycles of transmission that Yersinia pestis undergoes?
WILD/SYLVANTIC: flea, rodents, wildlife; fleas rely on infected rodents, like mice and prarie dogs, to pass infection off to others - humans are rarely in contact with these rodents, but flea bites can still transmit plague
DOMESTIC/URBAN: flea, rodents, domestic animals; rats are in closer contact with humans and bites from fleas transmit infection
What 5 outer surface structures act as virulence factors in Yersinia?
- capsule - prevents and promotes serum resistance and elicits a hemorrhagic inflammatory lesion
- lipopolysaccharide - endotoxin, pyrogen, blood vessel destruction
- low calcium response virulence (LcrV) - inhibits excretion of pro-inflammatory cytokines, neutrophil chemotaxis, and cytokine production
- attachment invasion (Ail) and Yersinia adhesion (Yad) - attachment and adhesion to microfold (M) cells of the gut, Peyer’s patches, and lymph nodes
- invasion protein A - host cell invasin, bacterial translocation
What are the 2 routes that Yersinia can take to reach mesenteric lymph nodes?
- Yersinia cells traverse the intestinal epithelium to the submucosa…..
1. submucosal macrophages phagocytose the pathogen and enter into the lymphatic system, reaching mesenteric lymph nodes
2. bacteria is engulfed by M cells, enter Peyer’s patches, forms microcolonies and replicates, and eventually are taken to the mesenteric lymph nodes
What 5 enzymes act as virulence factors in Yersinia?
- plasminogen activator (Pla/protease) - adhesion, initiates disseminated intravascular coagulation, endotoxemia, spread to lymph nodes and lung
- global stress requirement (Gsr/protease) - intracytoplasmic survival within macrophages
- coagulase - adhesion, initiates disseminated intravascular coagulation
- Yersinia murine toxin (Ymt/phospholipase D) - protection within fleas from attack by forming a capsule, disseminator
- urease - survival in the acidic stomach, intestinal colonization
What virulence factors are responsible for the clinical presentation of Yersinia?
plaminogen activator (protease) and coagulase initiate disseminated intravascular coagulation, which inhibits blood supply to necessary organs
- thrombosis
- infarction
- gangrene
What 2 toxins act as virulence factors in Yersinia? How are they injected into host cells?
- Yersinia outer protein (Yoops) - actin cytoskeleton, prevents phagocytosis
- Yersinia stable toxin (Yst) - enterotoxin that induce fluid and electrolyte accumulation in the gut lumen, causing diarrhea and dehydration
type 3 secretion system
What are the 3 major parts of Yersinia’s iron robbing/acquisition system?
- siderophores
- yersiniabactin
- hemin storage proteins
Yersinia pestis transmission:
transmission involves
- flea-borne
- air-borne
- amoeba
- vertebrates (rodents)
What is the route of transmission of Yersinia entrocolitica and Yersinia psuedotuberculosis?
ingestion —> fecal-oral
- swine = reservoir
How do the transmission routes compare in Yersinia species?
Y. pestis —> flea bites, airborne from infected mammals, ingestion orally by predation, cannibalism, and scavenging mainly in cats
Y. enterocolitics and pseudotuberculosis —> fecal-oral ingestion
What are 3 signs of Yersinia enterocolitica and Yersinia pseudotuberculosis infection?
- necroulcerative colitis
- mesocolonic edema
- congestion of serosal vessels
What does the initial transmission of Yersinia pestis result in? What results when humans pass it to other humans?
bubonic plague —> bacteremia may infect lungs
pneumonic plague spread by the respiratory route without the involvement of fleas
What are the reservoir animal species in each species of Yersinia?
Y. pestis —> fleas, prairie dogs, squirrels, rats, humans, deer, mice, gerbils, voles, rabbits, goats, camels, amoeba (ruminants, equines, pigs are not susceptible)
Y. enterocolitica and pseudotuberculosis —> all vertebrates
What are the 4 steps of Y. pestis transmission from fleas to another host?
1.Y. pestis grows in the midgut of fleas
2. once feeding on host, flea draws viable bacteria into its esophagus
3. bacteria multiply and block the proventriculus just in front of the stomach
4. bacteria force the flea to regurgitate infected blood onto the host when it tried to swallow
What are the clinical signs of the 3 forms of Y. pestis infection?
- Bubonic form = swelling of lymph nodes (buboes), fever, headache
- Pneumonic plague form = coughing up bloody sputum (spreads to other humans via aerosol from coughing)
- Septicemic form = death
What are common clinical signs of Y. eneterocolitica and Y. pseudotuberculosis infections?
Y. eneterocolitica —> mesenteric lymphadenitis, terminal ileitis, acute gastroenteritis, sepitcemia
Y. pseudotuberculosis —> mesenteric lymphadenitis, diarrhea, dehydration, septicemia
What is the clinical appearance of black death?
(caused by Y. pestis)
- acral gangrene of foot with septicemic plague due to thrombosis and infarction of the terminal segments of digits
- petechial rash
What samples can be taken for Yersinia isolation?
- blood culture (plague)
- bubo aspirate culture (bubonic plague)
- sputum culture (pneumonic plague)
- CSF culture (septicemic plague)
- fecal culture
- food/water culture
What major biological tests are used for Yersinia identification?
- Gram negative rod
- oxidase +
- MacConkey agar lactose -
- H2S gas on TSI -
- motility +/- based on species
- urease +
How is yersiniosis typically treated?
antibiotics are not typically recommended unless illness is severe/systemic
- most people and animals recover on their own
- individuals with diarrhea are recommended to drink plenty of fluids to prevent dehydration
How should Y. pestis and Y. eneterocolitica infections be treated when illness becomes severe?
Y. pestis —> dispense oxygen, IV fluids, and respiratory support; antibiotics: streptomycin, tetracycline, chloramphenicol
Y. enterocolitica —> trimethoprim-sulfamethoxazole, aminoglycosides, 3rd gen. cephalosporins, fluoroquinolones, tetracycline
How is Yersinia pestis infection controlled and prevented?
- monitor rodent populations, inspection, supervision of vector surveillance (decrease in rat population can risk fleas feeding on other animals = human epidemic)
- control fleas with insecticides
- quarantine to stop spread
- stop movement of people, baggage, cargo, containers, conveyances, and goods
- vaccination —> current ones not safe (LAV, killed whole cell)
How does the route of transmission affect Yersinia infection?
Y. pestis —> bioterrorism agent, flea-borne
Y. enetocolitica and pseudotuberculosis —> fecal-oral, food-borne
