Isolation Techniques and Selective Media, A Photographic Atlas for the Microbiology Laboratory, Chocolate II Agar
Purpose
Chocolate II Agar is used for isolation and cultivation of Neisseria (Figures 2-6 and 2-7) and Haemophilus (Figure 2-8) species.
Principle
Chocolate II Agar is made with a blend of casein, peptones, phosphate buffer, corn starch, and bovine hemoglobin. It also contains an enrichment supplement of amino and nucleic acids to encourage growth of Neisseria species and provide the X and V blood factors required by Haemophilus species (Figure 12-28).
This plated medium is typically streaked for isolation and incubated at 37°C in an aerobic environment enriched with carbon dioxide. Subcultures of colonies can then be grown on slanted media and used for diagnostic purposes.
2-6 NEISSERIA GONORRHOEAE ON CHOCOLATE
II AGAR Compare colony size with Figure 2-7.
N. gonorrhoeae colonies on Chocolate Agar are
typically colorless.
2-7 NEISSERIA MENINGITIDIS ON CHOCOLATE II AGAR
Compare colony size with Figure 2-6. N. meningitidis
colonies on Chocolate II Agar are typically large, bluegray and mucoid
2-8 HAEMOPHILUS INFLUENZAE ON CHOCOLATE II
AGAR Notice the large, smooth, mucoid colonies.
Suggested Reading
- Michael J. Leboffe & Burton E. Pierce. A Photographic Atlas for the Microbiology Laboratory 4th edition 2011
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