Importance of Gram Stain in Anaerobic Bacteriology

Gram stain is an important rapid tool for anaerobic bacteriology. It reveals the types and relative numbers of microorganisms and host cells present. Gram stain also serves as a quality control measure for the adequacy of anaerobic techniques.

Is there any modification of the Gram staining technique for the anaerobes?
Yes. We use the same standard gram stain procedure and reagents but the safranin counterstain is left on for 3 to 5 minutes. Alternatively, 0.5% aqueous basic fuchsin can be used as the counterstain.

What does positive gram stain and negative culture indicates?
Positive grams stain with negative culture report gives information regarding adequacy sample collection, transport and also of culture methods used. This situation may come in the following mentioned conditions:

  1. Poor transport methods
  2. Excessive exposure to air during sample processing
  3. Inadequate types of media or old media, or
  4. Failure of the anaerobic system used (jar, pouch, and chamber) to achieve an anaerobic atmosphere.
  5. That microorganisms have been killed by antimicrobial therapy