Bordet–Gengou agar

Bordet–Gengou Agar

Bordet–Gengou agar is a specialized growth medium used primarily for the isolation and cultivation of the bacterium *Bordetella pertussis*, the causative agent of whooping cough. This medium is named after the Belgian immunologist Jules Bordet and the French physician Octave Gengou, who developed it in the early 20th century.

Composition

Bordet–Gengou agar is an enriched medium that contains several key components:

• Potato extract: Provides a rich source of nutrients that support the growth of *Bordetella pertussis*.
• Glycerol: Serves as an additional carbon source.
• Sheep blood: Supplies essential growth factors and allows for the detection of hemolytic activity.
• Agar: A solidifying agent that provides a stable surface for bacterial growth.
• Antibiotics (e.g., cephalexin): May be added to suppress the growth of contaminating flora, allowing for the selective isolation of *Bordetella pertussis*.

Usage

Bordet–Gengou agar is primarily used in clinical laboratories for the isolation of *Bordetella pertussis* from nasopharyngeal swabs of patients suspected of having whooping cough. The medium supports the growth of this fastidious organism by providing a nutrient-rich environment.

Procedure

1. Sample Collection: A nasopharyngeal swab is obtained from the patient. 2. Inoculation: The swab is streaked onto the surface of the Bordet–Gengou agar plate. 3. Incubation: The plate is incubated at 35-37°C in a humidified atmosphere for 3-7 days. 4. Observation: Colonies of *Bordetella pertussis* appear as small, glistening, and pearly white colonies.

Limitations

While Bordet–Gengou agar is effective for isolating *Bordetella pertussis*, it has some limitations:

• Slow Growth: *Bordetella pertussis* grows slowly, requiring several days for visible colonies to appear.
• Contamination: Despite the use of selective agents, contamination by other bacteria can occur.
• Sensitivity: The sensitivity of culture can be lower compared to molecular methods such as PCR.

Also see

• Bordetella pertussis
• Whooping cough
• Culture media
• Microbiological culture