A new technique for Gram staining paraffin-embedded tissue.

Five techniques for Gram staining bacteria in paraffin sections were compared on serial sections of pulmonary tissues from eight bacteriological necropsies. Brown and Hopp's method was the most satisfactory for distinguishing Gram-positive and Gram-negative bacteria. However, this method cannot be recommended as the preparations were frequently overstained, and the Gram-negative bacteria were stained indistinctly. A modification of Brown and Hopps' method was developed which stains larger numbers of Gram-negative bacteria and differentiates well between different cell types and connective tissue, and there is no risk of overstaining.