YERSENIA
PROPERTIES
Gram negative rods Zoonotic organisms Motile (except Y. pestis) Bipolar staining- Wayson’s stain or
Giemsa stain (resembling to safety pin)
Peripheral blood smear of septicemic plague patient
showing large numbers of bipolar-staining bacilli
HUMAN PATHOGENS
10 species of yersinia are discovered but 3 are mostly known as human pathogens
Yersinia pestis (plague) Yersinia enterocolitica & Yersinia pseudotuberculosis
(enteritis)
YERSINIA PESTIS
HABITAT
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
DISEASE : plague
Plague is a classic rodent zoonosis. One of the most devastating
diseases of human history.
PATHOGENSIS AND PATHOLOGY
TWO STEPS: Transmission via flea The host response
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
PATHOGENSIS
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
Plague can be
Bubonic - fever painful lymphadenopathy – (bubo)
Septicaemic – fever, hypotension w/wo bubo
Pneumonic – cough, haemoptysis, w/wo bubo
Bubonic
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.”
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.
Contributing factors to VIRULENCE
Capsule Endotoxin Exotoxin-v and w protien (mechanism unknown) Yops (Yersinia outer protien)
DIAGNOSISThe pathogen must be identified in bubo punctate, sputum,orblood 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
Mac Conkey agar –› Colourless › The colony disappear after 2-3
days – autolysis Y.pestis
TRANSMISSION
Flea bite infected from wild rodents Human to human transmission by
respiratory droplets Direct contact with infected animals
TREATMENT
Streptomycin with tetracyclin Strict quarantine for 72 hours after
starting antibiotics Incision of buboes is contraindicated
PREVENTION
Animal control: avoid sick and dead animals Killed vaccines are available for high
risk occupation controlling the spread of rats in urban areas,
Y.Enterocolitica &Y.pseudotuberculosis
PROPERTIES
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
PATHOGENSIS
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
TRANMISSION
Unpasteurized milk Contaminated food and water Pork
RESERVIOR: mainly pigs
Clinical presentation
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
LAB DIAGNOSIS
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
Laboratory is usually not involved in the diagnosis of Y.pseudotuberculosis
Serological test are not available
TREATMENT
Enterocolitis and the mesenteric adenitis does not require treatment
Bacterimia or the abcess reqiure the treatment with a trimethoprim-sulfamethoxazole or ciprofaloxin
PREVENTION
No preventive measures except guard against the contamination of the food by the excreta of domestic animals.
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