Lecture 8 Flashcards
what are some reasons to study Y. pestis?
- it is part of reemerging disease
- has potential use as a biowarfare and bioterroism agent
- can be used to stidy therapeutic drug development and combating drug resistance strains
what are the three biovars of Y. pestis?
- antigua
- medievalis
- orientalis
how are the biovars of Y. pestis differentiated?
through their ability to reduce nitrate and to ferment glycerol and arabinose
what are some traits of of Y. pestis?
- it is a facultative anaerobe gram negative bacillus
- uses type 3 secretion
- intracellular`
how is Y. pestis different from Y. enterocolitica and Y. pseudotuberculosis?
Y. pestis is non motile while the other two are non motile at 37 degrees C and motile at 22 degrees C
how is Y. pestis identified?
- non motile
- bipolar staining
- slow growth of small colonies on ordinary culture media
what is meant by Y. pestis bipolar staining?
it uses Wrights stain which is a mixture of eosin (red) and mythelene blue dyes
which virulence plasmid is in all 3 strains of yersinia?
pYV
which plasmids are just in Y. pestis and not the other two?
pFra and pPla
Why are Y. enterocolitica and Y. pseudotuberculosis clinically significant?
- both are acquired by ingestion of contaminated food and water
- both cause a disease involving fever and abdominal pain
- after ingestion, the bacteria invade the intestinal epithelium by invasion of M cells
what type of strains of Y. pestis have been isolated from patients with bubonic plague?
multiple drug resistant strains
what is the reservoir for bubonic plague
infected wild rodents
what is the vector for the bubonic plague?
a rat flea that takes a blood meal from an infected rat or wild rodent
what are the three transmission routes of the plague?
- flea bite
- direct animal contact
- aerosol
what is the mechanism of transmission by flea bite?
- flea ingests organism during blood meal from infected host
- bacteria multiply and block proventriculus (throat parts of flea)
- flea regurgitates infectious material into new host when trying to feed
- flea stays hungry and feeds more aggressively
what are the two cycles of transmission of the plague?
the sylvatic (forest cycle) and the urban cycle
what is the sylvatic cycle?
pestis is maintained in the environment by spread through rodents, low risk of transmission to humans
what is the urban cycle?
rodent is domestic, plague spread rapidly among rodents cause them to die rapidly, flea search for new hosts increasing risk of infection to humans
what are the three forms of plague?
- pneumonic
2, bubonic - septicemic
what are some traits of the pneumonic plague?
inhalation, mortality is 57%, and most likely route for bioterroism
what are some traits of bubonic plague?
flea bite or animal handling, mortality is less than 5%
what are some traits of septicemic plague?
sepsis (whole body inflammatory response) and mortality is 30-50%
what can be used to distinguish between different species of yersinia?
an anti-F1 antibody test of serum
what can be used to identify Y. pestis?
PCR
how exactly can Y pestis be detected and identified?
using plague diagnostic phages A1122 and L-413C by qPCR with primers specific for phage DNA
what are some traits of pFra?
specific for Y. pestis, role in bacterial transmission by fleas
what are some traits of pPla?
specific for Y. pestis, role in transimssion and virulence
what are some traits in pYV
present in pathogenic species Y. pestis, pseudotuberculosis, and enterocolitica and has a role in pathogenicity
what exactly does pYV do in pathogenicity?
affects adhesion, antiphagocytosis, type 3 secretion of Yop proteins, and immune evasion
what are some traits of HPI?
present in all 3 strains of Yersinia, role in high pathogenicity
what is special about pYV?
has pCD1, calcium dependent
what is special about pPla
has pPCP1, pesticin, coagulase, plasminogen activator
what is special about pFra
has pMT1, murine toxin
what are pPCP1 and pMT1 unique to?
Y pestis
what are the virulence factors of Y. pestis?
- endotoxin
- murine toxin
- fraction 1
- V antigen
- pPla
- Psa
- iron acquisition and sequestering system
- Yad A
what symptoms is endotoxin responsible for?
hypotension, DIC, and endotoxic shock
what does murine toxin do?
causes edema and necrosis in mice but not in humans
what is fraction 1?
a protein component of the antiphagocytic protein capsule
what does the V antigen do?
a secretion protein that controls the expression of many of the virulence gene
what does Pla do?
a protease that activates plasminogen activator and degrades C3Bb and C5a
what does degrading C3Bb and C5a from Pla do?
degrading C3Bb prevents formation of complement membrane attack complex and degrading C5a prevents attraction of phagocytes
what does Psa (pPla) do?
a pilus adhesion for attachment
what does Yad A do?
an outer membrane protein that interferes with C3Bb binding to bacteria, preventing formation of the membrane attack complex
Go over the putative sequence of events in infection
look at slide 32
what are some antibiotics that do work on yersinia?
aminoglycosides, doxycycline, tetracycline, chloramphenicol
what antibiotics have no effect on yersinia?
penicillins and cephalosporins
