Following centrifugation, the resulting CSF sediment may be Visually examined for the presence of cells and organisms.
Stained Smear of Sediment. Gram stain must be performed on all CSF sediments. False-positive smears have resulted from inadvertent use of contaminated slides. Therefore, use of alcohol-dipped and flamed, or autodaved slides is recommended. After thoroughly mixing the sediment, a heaped drop is placed on the surface of a sterile or alcohol-deaned slide. The sediment should never be spread out on the slide surface, because this increases the difficulty of finding small numbers of microorganisms. The drop of sediment is allowed to air dry, is heat- or methanol-fixed, and is stained by either Gram (Figure 5 5-3) or acridine orange stains. The acridine orange fluorochrome stain may
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