The Plague

1
The Plague

• Two Med Students in Search of Answers
• Tam-Linh Nguyen
• Elizabeth Leddy

2
Intro

• Patient Info
• large swelling of lymph nodes at arm pit, neck
  and groin (buboes)
• high fever
• delerium
• black splotches on skin
• as the disease progressed, the buboes burst

3
Culture/Isolation of Organism

• Organism taken from blood or buboes
• Media used blood agar or other enteric media
• After 24 hours the colonies were pinpoint
• After 48 hours the colonies were 1-1.5 mm in
  diameter, and grey to greyish white, and slightly
  mucloid
• In broth culture (bile or bile salts), clumps
  adhere to side of tube

4
Tests performed
5
Yersinia Species

• Three species of Yersinia cause disease in humans
• Y. pseudotuberculosis and Y. enterocolitica are
  enteric food and water borne pathogens
• acquired by ingestion of contaminated food
• can cross the gastrointestinal mucosa
• infection is localized

6
Y. pestis

• Discovered in 1894 by French bacteriologist
  Alexandre Yersin
• Gram negative rod shaped bacilli
• found in low frequency in wild rodent
  populations, such as Rattus rattus (small and
  black) and Rattus norreguis (large grey sewer
  rat)
• Oriental rat flea Xenopsylla cheopis is prime
  transmitter of disease

members.aol.com/landmate/ biological.htm
7
Modes of Transmission
Rattus rattus
Rattus norvegicus
Xenopsylla cheopis
8
Y. pestis morphology

• Part of Enterobacteriaceae family
• Optimal growth at 28 deg. C
• Non-motile, slow in vitro growth
• Closely related to E. coli by DNA-DNA
  hybridization
• Unable to survive outside
  of a host organism

9
(No Transcript)
10
A little bit of history

• 6th Century (Justinians plague 541-767 AD)

11
A little bit of history

• Black Death (1346 to nearly the 19th century)
• this was also known as the Great Dying or the
  Great Pestilence
• Responsible for the death of 30 of the European
  population
• Third Pandemic (1894)

12
Transmission of Y. pestis

• Disease endemic to rat species
• Transmitted by fleas
• The flea bites the rat, and ingests the organism
• The Y. pestis replicates in the digestive tract
  of the flea
• A solid mass forms which obstructs the fleas gut

13
Transmission of Y. pestis
www.cdc.gov/ncidod/dvbid/ plague/cheob6x4.htm
14
Transmission of Y. pestis

• Flea cant ingest blood
• Gets increasingly hungry, therefore increasingly
  voracious
• The flea attacks more rats, which are then
  infected with the microbe
• When the rat population dwindles, the flea moves
  onto other available hosts, such as humans

15
Human to Human Transmission

• Inhalation of infected respiratory droplets
• When an infected human coughs, some microbe is
  released
• Airborne pathogen can be inhaled by another human
  in close proximity
• Accounts for ability of such a large outbreak in
  Europe

16
Stages of Disease

• Bacteria travel through the blood to the nearest
  lymph nodes
• In lymph nodes, Y. pestis is ingested by fixed
  macrophages
• Y. pestis is able to grow in inactivated
  macrophages and replicate
• Elicits an inflammatory response (the bubo)

17
Stages of Disease

• The inflammatory response - bubo

http//www.cdc.gov/ncidod/dvbid/images/bubo.jpg
www.exn.ca/Stories/ 2000/09/12/52.asp
18
Stages of Disease

• Bacteria from the bubo leak into the blood
  stream. (septicemic plague)
• Lysis of the bacteria releases LPS, which causes
  septic shock
• Eventually bacteria reach the lung, where they
  parasitize the lung macrophages (pneumonic plague)

19
Stages of Disease

• At the pneumonic stage, the bacteria can be
  spread to others via aerosols. (respiratory
  droplets)
• Direct inhalation at this point of the disease,
  induces more rapid development (than flea)
• At this stage the bacteria has well developed
  virulence factors needed to colonize the human
  body

20
Stages of Disease
http//gsbs.utmb.edu/microbook/images/fig29_4.jpg
21
Virulence Mechanism of Y. pestis

• Many genes necessary for virulence are found on
  plasmids
• Due to similarity of Y. pestis and Y.
  pseudotuberculosis, it is possible to eliminate
  certain genes located on Y. enterocolitica as
  critical to causing plague

22
Virulence Mechanism of Y. pestis

• The three similar Yersinia species have 70-75 kbp
  plasmids
• These plasmids carry a number of genes related to
  virulence

23
Virulence Mechanism of Yersinia

• These virulence genes produce virulence factors
  that fall into four general categories
• Adhesion and invasion (YadA)
• Execreted antiphagocytic proteins (Yops)
• Proteins involved in processing and excreting
  Yops (Ysc)
• Regulatory proteins (Lcr)

24
Virulence Mechanism of Y. pestis

• Genes represented are
  known to be encoded
  
  on the 75-kbp plasmid
  of Yersinia species

25
Virulence Mechanism of Y. pestis

• What do you think would happen if Y. pestis was
  cured of its virulence plasmids?

26
Virulence Mechanism of Y. pestis

• What do you think would happen if Y. pestis was
  cured of its virulence plasmids?
• A decrease in ability to colonize in the human
  body

27
Virulence Mechanism of Y. pestis

• What do you think would happen if Y. pestis was
  cured of its virulence plasmids?
• A decrease in ability to colonize in the human
  body
• Disease not able to spread as easily

28
Virulence Mechanism of Y. pestis

• Y. pestis has two more plasmids than Y.
  pseudotuberculosis and Y. enterocolitica
• One 110 kbp plasmid
• not much is known about the genes on this plasmid
• one gene encodes a protein component of an
  antiphagocytic protein capsule (F1)
• another encodes a toxin that kills mice, but has
  not been shown to be toxic in humans

29
Virulence Mechanism of Y. pestis

• Fraction 1 (F1) is a capsule like antigen
  expressed at 37 deg. C
• located on the large plasmid found only in Y.
  pestis
• Involved in the ability of Y. pestis to prevent
  uptake by macrophages
• Does not influence the general ability of
  phagocytic cells
• Expression of F1 reduced the number of bacteria
  that interacted with macrophages

30
Virulence Mechanism of Y. pestis

• The second plasmid (pPCP1) is a 9.5 kbp plasmid
  that encodes 3 proteins pesticin, pesticin
  immunity protein, and plaminogen activator

31
Virulence Mechanism of Y. pestis

• Plasminogen Activator (Pla)
• multifunction surface protein
• this aids in the spread of the disease throughout
  the human body
• may also have a role in the insect mediated
  transmission of the bacteria

32
Chromosomally encoded virulence factors

• Three chromosomally encoded virulence genes (yst,
  psa, inv)
• the first encodes a heat stable enterotoxin
• eventually leads to fluid build up in the
  intestine
• the second is the main structural component of
  the Yersinia fimbriae
• the third helps to colonize deep tissues (lymph
  nodes)

33
Yersinia Pestis Genome
magpie.genome.wisc.edu/browser/
Yersinia_pestis_circle.html
34
Special Traits of Y. pestis

• Two extra plasmids account for higher virulence
• Plasminogen
• Hemin storage
• iron reserve
• also protect the bacteria from hosts defenses by
  making it seem more like a host component

35
Treatment and Prevention

• Antibiotic Therapy
• streptomycin, tetracycline, and chloramphenicol
• all inhibit protein synthesis
• essential to help the immune system clear the
  infection
• the earlier the treatment is initiated, the
  better the outcome

36
Treatment and Prevention

• Sanitation
• keep rodent population down by proper disposal of
  garbage
• eliminate crowded living conditions of
  substandard housing

37
Treatment and Prevention

• Vaccines
• effective but protects for less than a year
• vaccine consists of whole killed Y. pestis cells
• requires a series of injections over a 6 month
  period
• live attenuated vaccines
• injection of non-pathogenic mutant, derived from
  a fully virulent strain
• safety questionable

38
(No Transcript)
39
Plague and relation to AIDS
CCR5 gene
http//www.cdc.gov/ncidod/eid/vol3no3/mcnicf4.gif
40
Ring Around The Rosy
http//www.thelewisfamilymusic.com/010829kidsring.
jpg
41
References

• Achtman, Mark, et al. Yesinia pestis, the cause
  of plague. Proceedings of the National Academy
  of Sciences. Nov. 23, 1999
• Balows, Albert. Ed. In chief. 1991. Manual of
  Clinical Microbiology. 5th Edition. American
  Society for Microbiology. Washington D.C.
• Du, Yidong, et al. Role of fraction 1 antigen of
  Yersina pestis in inhibtion of phagocytosis.
  Infection and Immunity. V70, no3. March 2002
• Gerhardt, Philipp, ed in chief. 1994 Methods for
  General and Molecular Bacteriology. American
  Society for Microbiology. Washington D.C.
• Lederberg, Joshua, ed in chief. Encylcopedia of
  Microbiology. 2nd Edition, v3. Assoc. Press, New
  York
• McEvedy, Colin. The Bubonic Plague. Scientific
  American. Feb. 1998 v. 258 n2 p118

42
References

• Revel, Paula A. Yersinia virulence more than a
  plasmid. FEMS Microbiology Letters. V206 no 2.
  Dec. 2001
• Salyers, Abigail A., and Dixie E. Whitt. 1994.
  Bacterial Pathenogeneis, a Molecular Approach.
  American Society for Microbiology. Washington
  D.C.
• Titball, Richard W, and E. Diane Williamson.
  Vaccination against bubonic and pneumonic
  plague. Elsevier. April 2001
• Wieland, Felix. ed. The Pla surface protease
  adhesin of Y. pestis mediates bacterial invasion
  into human endothelial cells. FEBS Letters.
  V504, no.1-2. Aug. 2001
• http//www.rkm.com.au/PLAGUE/
• http//www.cdc.gov/ncidod/dvbid/plague/
• http//www.sanger.ac.uk/Projects/Y_pestis/