The plague: The plague: Yersinia pestisYersinia pestis

Laura Brennan, Hayley Gibbins, Kirsty Heath, and Sabrina Ul-Hasan

htt

p:/

/ww

w.s

cien

cep

hoto

.com

/med

ia/1

13

56

/en

larg

e

“Ring Around The RosyA Pocket Full Of Posies

Ashes, AshesAll Fall Down”

It is thought that this nursery rhyme has origins from plague. “Ring” refers to an early clinical sign that appears on the skin (perhaps the ulcer that commonly appears around a flea bite wound infected with Y. pestis); “a pocket full of posies” refers to the use of flower petals as a means of warding off the stench and infection of a plague victim; “ashes, ashes” refers to dust to dust; and “all fall down” refers to victims who were falling down dead.

Yersinia pestis- The Yersinia pestis- The AnatomyAnatomyYersinia originally classified in

Pasteurellaceae family- Based on DNA similarities with E.coli,

Y.pestis is now part of Enterobacteriaceae family

o 11 named species in genus: 3 are human pathogen;

- Y.Pestis, Y.pseudotuberculosis, Y.enterocolitica

- Y.pestis and Y.pseudotuberculosis rarely infect humans

- -Y.enterocolitica is the cause of 1-3% of diarrhea cases caused by bacteria

Yersinia pestis-The Yersinia pestis-The AnatomyAnatomy Gram-negative Pleomorphic coccobacillus Aerobic, facultatively anaerobic,

facultatively intracellular3 biovars: Antiqua, Medievalis, and

OrientalisYersinia pestis has multiple plasmids

(110 and 9.5 kbp plasmids) and virulence factors (F1, Murine exotoxin, LPS endotoxin, coagulase, pesticin, plasminogen activator).

TransmissonTransmissonIn addition to the common Yersinia

virulence plasmid pCD~70-kb ,Y.pestis harbours 2 unique plasmids regulting its transmission:the murine toxin (pMT1 ~100-kb) and plasminogen activator/ ‘pesticin’ (pPCP ~9.6kb) plamids

Plasmids carry ‘molecular fingerprints’ left behind during evolution and account for emergence of Y.Pestis

The DNA relationship between Y. pestis and Y.

pseudotuberculosis chromosomes is greater than eighty percent as measured by DNA::DNA hybridization analysis

PlasmidsPlasmids

History-The ArrivalHistory-The ArrivalArrived in October 1347 Started in Asia then travelled to

Europe by rat infested Italian ships trading goods across the Mediterranean sea

Geographical spread Geographical spread

Types of plagueTypes of plague Bubonic plague- Most common- Infection of lymph system (attacks immune system)- Bacterium kills by cutting off cells ability to

communicate with immune cells that are vital to fight bacterial invasion

- YopJ the protein Yersinia uses to block this signalling process is one of 6 proteins injected into macrophages

Pneumonic plague-Most serious type-Infection of lungs leading to pneumonia Septicemic plague-Bacteria reproduces in the blood-Can be contracted like bubonic plague but is most

often seen as a complication of untreated bubonic or pneumonic plague

Epidemiology-Epidemiology-EnvironmentEnvironment

Epidemiology-vector Epidemiology-vector dynamicsdynamics

Epidemiology-Host Epidemiology-Host suseptibilitysuseptibility