Concentrated gram stain smears prepared with a cytospin centrifuge.

A Cytospin slide centrifuge was used to concentrate 0.05- to 0.5-ml samples of cerebrospinal and other body fluids for Gram stain. Trials with cerebrospinal fluid containing known numbers of microorganisms indicated that the Cytospin increased the sensitivity of cerebrospinal fluid Gram stains by up to 2 logs compared with unconcentrated and conventional centrifuge smears. Cytospin-concentrated smears were prospectively compared with unconcentrated Gram-stained smears and bacteriological culture results for 80 clinical body fluid specimens. Bacteria were seen in unconcentrated smears of 9 of the 16 (56%) fluids which were infected, whereas Cytospin smears of 12 of the 16 (75%) showed bacteria. Cytospin smears revealed more bacteria and demonstrated better leukocyte morphology than did unconcentrated or conventionally centrifuged samples of small volumes of infected body fluids, allowing early diagnosis of infection.