Bacterial Endocarditis



These digitized slides show a segment of mitral valve with a large vegetation. The vegetation is delineated by the blue dotted line over the Movat pentachrome stain. The areas of the vegetation containing bacteria are delineated with white dotted lines in all four stains. The valve tissue is highlighted by the red dotted lines. The vegetation consists mostly of fibrin with focal ares of red blood cell clusters. The vegration flanks the mid portion of the valve and the upper surface. This area is the “seat” of the vegetation. The fibrinous nature of the vegetation makes it friable and prone to fragmentation during the movement of the valve, which in turn, can be the source of embolization. The Gram stain for bacteria shows that the microorganisms are stained in dark blue color and form clusters (i.e. Gram positive cocci). The same colonies of cocci stain distinctly as black microorganisms in the GMS stain. Once you identify these in the Gram and GMS you will see that they are also visible as slightly blue colonies in both the H&E and the Movat.



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