For nonspecific staining of Rickettsia, the recommended stain is Gimenez stain. What is the correct stain for this purpose?

• A. Kinyoun stain
• B. Gomori silver stain
• C. Gram stain
• D. Gimenez stain

Answer: (D)

Rickettsia are tiny intracellular bacteria, so the staining method chosen must reliably highlight the organisms inside host cells and provide clear contrast. The Gimenez stain is a rapid differential stain specifically used to visualize Rickettsia (and Chlamydia) in fixed smears and tissue sections. It typically colors the organisms distinctly against a contrasting background, making them easier to spot inside cells without the need for more complex techniques. Other stains listed have different primary uses and don’t provide that reliable visualization for Rickettsia: the acid-fast stain is mainly for Mycobacteria, the Gomori silver stain targets fungi and some other structures, and Gram staining is often not dependable for intracellular organisms. Therefore, for detecting Rickettsia in nonspecific staining, Gimenez stain is the appropriate choice.