Application of a Rapid Method for Gram Differentiation of Human Pathogenic and Non-Pathogenic Bacteria without Staining (Short Communication) Talib Ruaa A.1, Abiess Abid Ali Abeid1 1Dept. of Pathological Analysis, College of Al-Mustaqbale University, Iraq Online published on 30 April, 2019. Summary The Gram-stain reactions of pathogenic and non-pathogenic bacteria isolated from clinical samples were accurately characterized by mixing a concentrated droplet of cells with 3% potassium hydroxide (KOH). Compared to standard Gram-staining procedures, the KOH test was rapid, simple, and completely accurate. Forty-one isolates representing Bacilus, Corynebacterium, Escherichio, Haemophilus, Klebsiella, Neisseria, proteus, Pseudomonas, Salmonella, Shigellae, Staphylococcus, and Streptococcus species were tested. Bacteria cell were removed from an agar medium with toothpick placed on a glass slide with drop of 3% KOH with rapid circular agitation. With Gram-negative stains the suspension become viscous as revealed by a mucoid thread that formed when the toothpick was lifted. Gram-positive bacteria dispersed in to the drop and did not have this reaction. One isolate of Corynebacterium caused an increase in drop viscosity, but did not produce a mucoid thread. This method substitutes stains uses which are expensive and can be done in seconds. Top Keywords Gram stain, KOH test. Top |