STAINING

STAINING

1. Simple Stain

   • dye is attracted to the bacterial cell because there is an electrical charge difference between the dye and cell wall of bacterium
   • dyes typically used: eosin, safranin, methylene blue, and malachite green

2. differential staining using 2 colors of dyes

   • Acid-fast Stain - used for Mycobacterium and Nocardia genera
     • for suspected tuberculosis patients
       • primary stain is a red stain - carbolfuschin
         • counter stain is methylene blue
           • acid-fast microorganisms appear red; others appear blue
   • Gram Stain
     • first is the primary stain -- crystal violet, resulting in certin cells with bluish-purple color ((GRAM +))
       • then, decolorize wtih acetone-alcohol 5-10 secs
         • follow with a counterstain of safranin, resulting in some cells appearing reddish-pink ((GRAM -))
       • next with iodine followed by water rinse