Lec 2. Yesinia pestis and Plague (1).pdf

Microbiology 2: Yersinia pestis and Plague Prof. Hazem Aqel Blood and Lymphatic System Basic Medical Sciences Objectives Describe the general microbiological properties and differences from other yersinia. Understand cultural techniques, epidemiology and pathophysiology. Describe the clin...

Microbiology 2: Yersinia pestis and Plague Prof. Hazem Aqel Blood and Lymphatic System Basic Medical Sciences Objectives Describe the general microbiological properties and differences from other yersinia. Understand cultural techniques, epidemiology and pathophysiology. Describe the clinical presentation, specimen collection for culture, treatment and prevention. Plague Yersinia pestis enterobacteriaceae  Morphology and the Structure Yersinia pestis is a non-motile, non–spore-forming, gram-negative bacillus with a tendency toward pleomorphism and bipolar staining. It is a member of the Enterobacteriaceae family and shares features of the other Yersinia pathogenic for humans (Y. pseudotuberculosis, Y. enterocolitica), such as virulence plasmids and multiple Yersinia outer membrane proteins (Yops). In addition, Y. pestis has two virulence plasmids, which code for a glycoprotein gel- like capsule called the F1 antigen and enzymes with phospholipase, protease, fibrinolytic, and plasminogen-activating activity. Yersinia pestis also has its own adhesin similar to the invasins of the other Yersinia. pseudomonas Yersinia pestis Pathogenesis and Clinical Disease Organisms are carried by the lymphatic system from the site of inoculation to regional lymph nodes, where they are ingested by phagocytes. Y. pestis multiplies in these cells. Hematogenous spread of bacteria to other organs and tissues may occur, resulting in hemorrhagic lesions at these sites. Disease Cycles Sylvatic (wild) Urban (domestic) Reservoirs Rock squirrels Ground squirrels Prairie dogs Mice, voles Others Sylvatic Plague affects animals ↑ Enzootic Steady level of disease Low rodent mortality Mice and voles are probably significant enzootic reservoirs. Epizootic Increased rodent mortality Fleas seek out new hosts Expansion into human occupied areas Greatest threat to humans Urban Plague Infected fleas or rodents move into urban areas Domestic rodents infected High rodent mortality Fleas seek new host Domestic cats or humans Associated with poverty in humans Mode of Transmissions Flea bite Direct animal contact Tissues, body fluids, scratches, bites Enters through break in skin Aerosol Human cases April through November Increased activity of fleas and hosts Flea Vectors Can live off host for months Many species can serve as vector Oropsylla montana Rock squirrels, California ground squirrels, prairie dogs Most important flea vector in U.S. Xenopsylla cheopis Epidemics in Asia, Africa, South America Flea Transmission 27°C (80°F) Blood clots in gut of flea Y. pestis trapped E Clotted blood regurgitated - Enters wound from flea bite 27°C Blood clot in gut of flea dissolves Y. pestis passes through