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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