Identification of Gram negative bacteria in histological sections using Sandiford's counterstain

Abstract

Sandiford's counter stain was designed for use with bacteriologic smears but appeared eminently suitable for applying to paraffin sections. A modification is described in brief, which consists of staining bacteria which are not Gram positive with pyronin and using malachite green as a counterstain. The resultant black and red organisms (Gram positive and negative respectively) both contrast well with the blue green background and are easily recognisable. This method was used for 5 yr and it was found to be most helpful in the recognition of Gram negative bacteria. A comparison of Twort's and Sandiford's modifications of the Gram stain shows that the results are virtually indistinguishable, but the Sandiford method is prefered because it is quicker.