11. Yersinia Flashcards
What disease does Yersinia spp. cause?
Food poisoning, plague
How does Yersinia spp. cause disease?
Invasion, vector borne, T3SS
Features of Yersinia?
- Vector borne
- Gram neg
- Rod-shaped
- Psychrotrophic (like low temperatures)
- Enterobacteriaceae (Shigella, E.coli, Salmonella)
Examples of psychrotrophic pathogens?
Listeria monocytogenes, Yersinia spp.
Which family is Yersinia part of?
Enterobacteriaceae
Which strains of Yersinia cause food poisoning (yersiniosis)?
Yersinia entercolitica &
Yersinia pseudotuberculosis
- food or waterborne
Which strain of Yersinia causes plague/Black Death?
Yersinia pestis
Tick borne , reservoirs in rodents
Animals (swine, rats, ticks [plague])
Yersiniosis symptoms?
Diarrhoea, abdominal pain, fever, appendicitis-like
Pathogenesis of Yersinia enterocolitica & pseudotuberculosis
- Both invasive
- Both species are transmitted through M cells
- Cause a localised inflammatory response - cause symptoms
- Eventually eliminated by PMNs (white blood cells)
Sequelae of yersiniosis?
Can have a complication of Reiter’s Syndrome (an autoimmune response due to cross-reaction between Abs & host Ags
Many of the Yersinia virulence traits are encoded by a large virulence plasmid (pCD1 or pYV). The plasmid encodes 4 main gene categories:
- Adhesin/invasion: YadA - adhesin which can force uptake (by M cells)
- Iron uptake: high pathogenicity island (HPI)(Yersiniobactin - siderophore)
- Antiphagocytic proteins: Yops (>11), delay phagocytosis, Ysc (encodes the T3SS) exports Yops via the T3SS
- Regulatory proteins: Lcr - regulates all the genes
What is the YadA adhesive protein important in?
Binds to collagen
Serum resistance - inhibits the classical pathway of complement activation
Discuss the T3SS in Yersinia
- T3SS found in all pathogenic strains of Yersinia
- Classic needle-like structure - made of polymer YscF, with a tip YopB
- Effector proteins (Yop proteins) excreted into cell
- Immunosuppression - dampens immune response of some cells to help colonise & start infection
- Interacts with key signalling pathways
- Antiphagocytic - by interfering with actin rearrangement necessary for phagocytosis
Toxin produced by Yersinia?
Yst: Yersinia stable toxin
similar to E. coli ST (small peptide)
3 variants: ystA, ystB, ystC
*role in virulence of Y.entercolitica not yet established
Treatment for yersiniosis?
Usually self-limiting for gastroenteritis
- wait it out
What causes the Bubonic Plague/Black Death?
Yersinia pestis
How is the Black Death acquired?
Via insect bites or person to person contact
Bacteria enter bloodstream and travel to the lymph nodes where they cause swelling
3 types of plague?
- Bubonic plague: most common, infection of the lymph system, swollen LNs
- Pneumonic plague: most serious, infection of lung macrophages that leads to pneumonia, primary and secondary, high transmissibility & fatality
- Septicaemic plague: bacteria reproduce in blood, characterised by LPS shock, contracted like bubonic plague but is most often seen as a complication of untreated bubonic or pneumonic plague
Large outbreaks of plague would be associated with large numbers of which type of plague?
Pneumonic plague
Difference between primary and secondary pneumonic plague?
Primary - contracted when infected droplets are directly inhaled (can be passed from person to person)
Secondary - develops when bubonic or septicaemic goes untreated (moves to lungs and then can be spread to someone else)
How is plague usually treated?
By Streptomycin
3 strains of Yersinia?
Y. enterocolitica
Y. pseudotuberculosis
Y. pestis
What is Yersinia commonly mistaken for?
Appendicitis
- abdominal pain
- fever
True of false: Yersinia is part of the normal human flora.
False
Is YadA an important virulence factor in all strains?
- Important virulence factor in Y. enterocolitica
- Dispensable in Y. pseudoTB
- Pseudogene in Y. pestis
How is Y.pestis spread
Rodent population have it, are fed on by fleas, fleas pick it up, rodents all die
because of it, fleas have no food, feed on humans → plague
How many plague pandemics have there been? How many deaths were caused?
- Justinian Plague
- Black Death (most severe)
- Chinese province of Yunnnan
200 million deaths
How do we know Y. pestis was responsible for Justinian Plague?
Plague graves fin Bavaria, radiocarbon dating, DNA extracted from teeth, DNA was enriched with Y. pestis and sequenced, confirmed presence
Death toll of Justinian Plague?
Killed 50-60% of European population
Death toll of black plague?
50% of European population - 25 million
50% of China population - 60 million, 70% in Muslim world
Plague in Ireland
What is the most recent outbreak of Plague?
Madagascar November 2017
2348 cases, 202 deaths
What plasmids is Y. pestis host to?
Plasmid pCD1 (pYV) and two others, plasmid pPCP1 (pPla/pPst) and pMT1 (pFra) which are not carried by Yersinia species
What did Y. pestis emerge from?
Y. pseudotuberculosis (20,000 years ago)
True or False: Y. pestis contains many of the same genes as Y. pseudotuberculosis
TRUE
- Pseudogenes- Y. pestis has same genes as YP but they aren’t expressed
- Over 150 of these, including YadA
- One way via which these bacteria can rapidly evolve
Symptoms of Bubonic plague
Fever, headache, chills, weakness, swollen and tender lymph glands
Symptoms of Pneumonic plague
Fever, headache, weakness, rapid onset of pneumonia (usually accompanied by: shortness of breath, chest pain, cough, bloody or watery sputum)
Symptoms of Septicemic plague
Fever, chills, weakness, abdominal pain, shock, bleeding underneath skin
or other organs
