Presentation on theme: "Yersinia Non lactose fermenting Gram negative rods"— Presentation transcript:
1Yersinia 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 manDemonstrate bipolar staining in Giemsa stained smears from animal tissuesSerotyping and biotyping used to discriminate between strains10 serotypes of Y. pseudotuberculosis, serotypes I, II and III contain majority of pathogenic isolates5 biotypes and more than 50 serotypes of Y. enterocolitica
2Diagnosis Histological examination of intestinal lesions Giemsa stained smears of pus reveal large numbers of bipolar rodsCulture of Y. enterocolitica and Y. pseudotuberculosis from faeces, pus or tissuePlated on MacConkey agar for growth at 37 or room temperatureDFA tests (direct fluorescentantibody)API 20ECold enrichmentSerotyping
6Yersinia speciesY. pseudotuberculosis and Y. enterocolitica in intestinal tract of wild mammals, birds and domestic animalsAll may be reservoirs of infectionMany avian species may act as amplifier hosts and may transfer the organisms mechanicallyBoth 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
7Pathogenesis 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 macrophagesEnteric Yersinia infection (Y. enterocolitica and Y. pseudotuberculosis) gain access to intestinal mucosa via M cells of Peyers patchesAdhesion 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
8PathogenesisSurvival 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 hostPlasmid encodes the Yop virulonThis 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
10Plague Caused by Yersinia pestis (3 biotypes) Black death in 1300’s killed a quarter of Europe’s populationZoonotic infection in rodents, transferred by fleasOrganism in blood of rodents, blood (+ organism) taken up by fleas and flea bites humans (or cats)Humans infected by flea bitesEndemic in Africa, Asia, USA - southwest and pacific coast plague foci (and others) (prairie dogs, ground squirrels, antelope ground squirrels, chipmunks, wood rats and deer mice)Potential bioterrorist weapon (pneumonic plague – person-person spread by airborne route)
13Clinical infectionY. pestis can infect both dogs and cats in endemic areasCats are particularly susceptible, may be a source of infection for owners and attending vetsUsually acquired by ingesting infected rodentsBubonic, septicaemic, pneumonicCats with pneumonic plague are a source of human infection through aerosol generation and should be euthanizedHuman infection acquired through cat scratches and bites and fleas from infected catsCare required when handling any infected animals!
14Plague syndromes in man Bubonic - fever painful lymphadenopathy – (bubo)Septicaemic – fever, hypotension w/wo buboPneumonic – cough, haemoptysis, w/wo buboMeningitis – fever, nuchal rigidity usually with bubo
16Virulence 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 opsonisationPla is essential for Y. pestis to disseminate from a subcutaneous site of inoculation to lymph nodes or the bloodstream.
17Treatment and control Cats with suspected plague kept in isolation IV tetracycline or chloramphenicol for bubonic plagueEndemic areas dogs, cats routinely treated for fleasRodent controlEffective human and animal based surveillanceIncidence in animal populationAvoid sick/dead animalsAvoid endemic areas or outbreak areasVaccinationInsect repellentsIsolate human cases (and contacts)Treat human cases with antibiotics