Brown and Brenn staining specifically highlights which group?

• A. Gram+ bacteria
• B. Gram- bacteria
• C. Fungi
• D. Viruses

Answer: (A)

Brown and Brenn staining is a histochemical method used to visualize bacteria in tissue, with a particular affinity for Gram-positive organisms. This specificity comes from the thick peptidoglycan layer in Gram-positive bacteria, which readily takes up the stain and appears prominently, making them stand out from other elements. Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane, so they don’t stain as strongly with this method. Fungi and viruses don’t show this Gram-positive–specific pattern, so they’re not the group highlighted by Brown and Brenn.