Chocolate Agar Interactive Learning App
🩸 Chocolate Agar Interactive Microbiology Learning System
Theory Preparation Virtual Lab QC Limitations References
Intended Use Chocolate Agar is an enriched, non-selective medium for cultivation of fastidious organisms including Haemophilus and Neisseria .
Principle Heating blood lyses RBCs. Lysis releases X factor (hemin) and V factor (NAD). Supports fastidious organisms. Explain X & V Factors
Composition
Component Role Peptones Nutrients Sodium chloride Osmotic balance Agar Solidifying agent Defibrinated blood Source of X & V factors after heating Enrichment supplement (e.g. IsoVitaleX) Growth factors
Blood Agar vs Chocolate Agar
Blood Agar Chocolate Agar Intact RBCs Lysed RBCs Shows hemolysis No hemolysis visible Limited X/V availability X and V factors available
Preparation
Prepare basal medium. Autoclave at 121°C for 15 min. Cool to 75–80°C. Add sterile defibrinated blood. Mix until chocolate-brown. Cool to 45–50°C and pour plates. Virtual Colony Interpretation
Small Grey Colonies
Large Moist Grey Colonies
Opaque White Colonies
No Growth
Satellite Phenomenon Show
QC Organism Expected Result Haemophilus influenzae ATCC 49247 Good growth Neisseria gonorrhoeae ATCC 43069 Good growth in CO₂ Neisseria meningitidis ATCC 13090 Good growth
Does not demonstrate hemolysis. Not selective unless antibiotics are added. Species identification requires additional tests. Incubate many pathogens in 5–10% CO₂. Bailey & Scott's Diagnostic Microbiology. Koneman's Color Atlas. MacFaddin. CLSI M22.
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