2.  Gram negative rods
 Zoonotic organisms
 Motile (except Y. pestis)
 Bipolar staining- Wayson’s stain or
Giemsa stain
(resembling to safety pin)

3. Peripheral blood smear of septicemic plague patient
showing large numbers of bipolar-staining bacilli

4. 10 species of yersinia are discovered but
3 are mostly known as human
pathogens
 Yersinia pestis (plague)
 Yersinia enterocolitica &
 Yersinia pseudotuberculosis (enteritis)

6.  Y. pestis survives in the stomach and
proventriculus of the flea and in the soil
of animal burrows
 RESERVIOR:
rodents mainly,prairie dogs,field
mice,chipmunks,rabbits,cats etc.
 VECTOR:
flea
 Human are accidental host

7.  Plague is a classic rodent zoonosis.
 One of the most devastating diseases
of human history.

9.  TWO STEPS:
Transmission via flea
The host response

10.  Fleas become infected by feeding on a
bacteremic host.
 Transmission factors are expressed that
allow the bacillus to colonize the flea
midgut, replicate, and create a
blockage of the flea intestine.
 “blocked” fleas feed aggressively,
regurgitating bacteria into the bite
wound

12.  Inoculation of organism through flea bite
swelling and tenderness of
regional lymph nodes(buboes-so named
bubonic plague) bacterimia
endotoxin related sympyoms
(DIC,cutaneous hemorrhages)
black death

14.  Bubonic - fever painful
lymphadenopathy – (bubo)
 Septicaemic – fever, hypotension
w/wo bubo
 Pneumonic – cough, haemoptysis,
w/wo bubo

15.  Bubonic

16.  Purpuric skin lesions are the most
obvious manifestations of a bleeding
diathesis
 These startling cutaneous signs may
be the origin of the term “Black
Death.”

17. The sylvatic (forest) cycles
 Y. pestis is maintained in the environment by
enzootic spread of the organism among
rodents and low risk for transmission to
humans
The urban cycles
 The rodent is domestic
 Epizootic plague spreads rapidly among
susceptible rodents, which die off rapidly
 An avid search by their fleas for new hosts,
and an increased risk of spread of infection
to humans.

19.  Capsule
 Endotoxin
 Exotoxin-v and w protien
(mechanism unknown)
 Yops (Yersinia outer protien)

20. The pathogen must be identified
in bubo punctate, sputum,or
blood by means of microscopy and culturing
 Fluorescent-antibody staining -identify the
organism in tissues
 ON BLOOD AGAR:
non-hemolytic
› opaque with a gray to yellow color in the
center; they remain transparent and gray
to white in color on the periphery

22.  Mac Conkey agar –
› Colourless
› The colony disappear after 2-3 days
– autolysis Y.pestis

23.  Flea bite infected from wild rodents
 Human to human transmission by
respiratory droplets
 Direct contact with infected animals

24.  Streptomycin with tetracyclin
 Strict quarantine for 72 hours after
starting antibiotics
 Incision of buboes is contraindicated

25.  Animal control:
avoid sick and dead animals
 Killed vaccines are available for high risk
occupation
 controlling the spread of rats
in urban areas,

27.  Zoonotic
 Enterotoxin
 can Multiplies in cold
 Enterocolitis in northern climates
 Y. pseudotuberculosis and Y.
Enterocolitica found in intestinal tract
of wild mammals, birds and domestic
animals

28.  Pathogenic enteric Yersinia invade some
cells (M cells) and prevent uptake by other
cells (phagocytes)
 Enteric Yersinia infection (Y. enterocolitica
and Y. pseudotuberculosis) gain access to
intestinal mucosa via M cells of Peyers
patches
 Adhesion too and invasion of these cells
facilitated by adhesion and invasion
proteins which bind to receptors on host
cells (invasin binds host integrins)
 In GI mucosa, bacteria prevent
phagocytosis, replicate in mesenteric lymph
nodes with the development of necrotic
lesions and neutrophil infiltration

30.  Unpasteurized milk
 Contaminated food and water
 Pork
RESERVIOR:
mainly pigs

31.  Fever,abdominal pain, diarrhea
May vary with age
 Very young:ferible diarrhea (blood and
pus)
 Older kids/young adults: pseudo
apendicitis
 Adults: enterocolitis with post-infective
seqeulae like reactive arthritis

32.  Y.enterocolitica usually isolated from the
stool specimen.
 Forms lactose negative colony on the
MacConkey’s test.
 Biochemical test are positive at 25
degree celcius and negative at
37degree celcius

33.  Laboratory is usually not involved in the
diagnosis of Y.pseudotuberculosis
 Serological test are not available

34.  Enterocolitis and the mesenteric adenitis
does not require treatment
 Bacterimia or the abcess reqiure the
treatment with a trimethoprim-sulfamethoxazole
or ciprofaloxin

35.  No preventive measures except guard
against the contamination of the food
by the excreta of domestic animals.