1 Yersinia • Non lactose fermenting Gram negative rods • Motile (except Y. pestis) • 10 species, only Y. pestis (plague), Y. enterocolitica, Y. pseudotuberculosis (enteric disease, septicaemia) pathogenic for animals and man • Demonstrate bipolar staining in Giemsa stained smears from animal tissues • Serotyping and biotyping used to discriminate between strains • 10 serotypes of Y. pseudotuberculosis, serotypes I, II and III contain majority of pathogenic isolates • 5 biotypes and more than 50 serotypes of Y. enterocolitica
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1 Yersinia Non lactose fermenting Gram negative rods Motile (except Y. pestis) 10 species, only Y. pestis (plague), Y. enterocolitica, Y. pseudotuberculosis.
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Yersinia• Non lactose fermenting Gram negative rods• Motile (except Y. pestis)• 10 species, only Y. pestis (plague), Y. enterocolitica, Y.
pseudotuberculosis (enteric disease, septicaemia) pathogenic for animals and man
• Demonstrate bipolar staining in Giemsa stained smears from animal tissues
• Serotyping and biotyping used to discriminate between strains
• 10 serotypes of Y. pseudotuberculosis, serotypes I, II and III contain majority of pathogenic isolates
• 5 biotypes and more than 50 serotypes of Y. enterocolitica
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Diagnosis• Histological examination of intestinal lesions• Giemsa stained smears of pus reveal large numbers
of bipolar rods• Culture of Y. enterocolitica and Y. pseudotuberculosis
from faeces, pus or tissue• Plated on MacConkey agar for growth at 37 or room
temperature• DFA tests (direct fluorescent
antibody)• API 20E• Cold enrichment• Serotyping
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Yersinia species• Y. pseudotuberculosis and Y. enterocolitica in
intestinal tract of wild mammals, birds and domestic animals
• All may be reservoirs of infection• Many avian species may act as amplifier hosts and
may transfer the organisms mechanically• Both organisms grow in a wide temperature range (5-
42 degrees)• In endemic areas wild rodents are important
reservoirs of Y. pestis. Fleas, especially the Oriental rat flea transmit the infection to man and other animals
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Pathogenesis of enteric disease
• Pathogenic enteric Yersinia invade some cells (M cells) and prevent uptake by other cells (phagocytes)
• Virulence factors maintain survival and inhibit phagocytosis by PMN’s and macrophages
• 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
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Pathogenesis• Survival of Y. enterocolitica and Y. pseudotuberculosis is
enhanced by anti-phagocytic proteins secreted by the organism (via a type III secretion system) which interfere with the normal functioning of neutrophils and macrophages in the host
• Plasmid encodes the Yop virulon
• This is a system allowing extracellular bacteria adhering on the surface of eukaryotic cells to secrete and inject bacterial effector proteins called Yops into the cytosol of the target cell in order to disable or alter their function
• Meningitis – fever, nuchal rigidity usually with bubo
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BubonicSepticaemic
Pneumonic
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Virulence factors specific to Y. pestis
• phospholipase D required for survival in flea midgut.
• HPI for iron acquisition (also Ye and Yp)• Fraction 1 (F1) antigen associated with
capsule around the bacteria. F1 prevents opsonisation
• Pla is essential for Y. pestis to disseminate from a subcutaneous site of inoculation to
lymph nodes or the bloodstream.
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Treatment and control
• Cats with suspected plague kept in isolation• IV tetracycline or chloramphenicol for bubonic plague• Endemic areas dogs, cats routinely treated for fleas• Rodent control• Effective human and animal based surveillance• Incidence in animal population• Avoid sick/dead animals• Avoid endemic areas or outbreak areas• Vaccination• Insect repellents• Isolate human cases (and contacts)• Treat human cases with antibiotics