Chocolate agar

Definition

Chocolate agar is an enriched growth medium used for culturing fastidious bacteria, particularly those found in the respiratory tract. It contains lysed red blood cells, which provide necessary nutrients.

5 Must Know Facts For Your Next Test

1. Chocolate agar is used to culture Neisseria meningitidis and Haemophilus influenzae, both of which can cause respiratory infections.
2. The medium appears brown due to the presence of lysed red blood cells.
3. It supports the growth of organisms that require additional factors like NAD (V factor) and hemin (X factor).
4. Chocolate agar is incubated at 37°C in a CO2-enriched atmosphere to optimize bacterial growth.
5. It's particularly useful for isolating pathogens from clinical specimens such as sputum or throat swabs.

Review Questions

• What types of bacteria are commonly cultured on chocolate agar?
• Why does chocolate agar appear brown?
• What additional factors do bacteria require that chocolate agar provides?

Related terms

Blood Agar: A growth medium that contains intact red blood cells and is used to differentiate bacterial species based on hemolytic properties.

Neisseria meningitidis: A Gram-negative bacterium that can cause meningitis and other serious infections; often cultured on chocolate agar.

Haemophilus influenzae: A Gram-negative bacterium associated with respiratory infections, especially in children; requires X and V factors for growth.