The laboratory diagnosis of bacterial pneumonia relies on both direct microscopy and quantitative culture techniques. Direct microscopy of stained cytocentrifuged cell preparations provides information on the specimen quality and presence of potentially significant organisms. The Dif-Quik (American Scientific Products, McGaw Park, IL), a modified Ciemsa stain, is a rapid method, taking less than 1 min to perform. It is useful to assess cellular content, particularly for the presence of >1 percent SEC (a maker of oropharyngeal contamination) and to demonstrate intracellular bacteria in the phagocytic cells (a good index of bacterial infection). A Cram stain, performed on additional slides, identifies the morphologic features of the infecting organism(s). antibiotics levaquin
Because of the inevitable oropharyngeal contamination that occurs in the collection of BAL samples, quantitative cultures have been advocated to differentiate contaminants from bacteria causing infection. The procedures described in the literature have included quantitative techniques at a single dilution (semiquantitative), obtained by direct plating a 0.01-ml volume,* and quantitative cultures using three serial 100-fold dilutions of the specimen.
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