BordetGengou

Bordet-Gengou medium, also known as Bordet-Gengou potato-glycerol-blood agar, is a selective enrichment culture medium used for isolation of Bordetella pertussis, the bacterium that causes pertussis (whooping cough). It was developed by Jules Bordet and Octave Gengou in the early 20th century as a means to cultivate this fastidious pathogen.

Composition and preparation: The medium is based on potato infusion agar enriched with glycerol and defibrinated blood. In clinical practice, antibiotics such as cephalexin are often added to suppress competing flora, enhancing the isolation of Bordetella pertussis. The precise formulation can vary by laboratory, but the combination of plant-based nutrient support with blood provides essential growth factors for the organism.

Usage and interpretation: Nasopharyngeal specimens or aspirates are inoculated onto Bordet-Gengou plates and incubated at approximately 35–37°C in a humid atmosphere. Colonies of Bordetella pertussis typically appear after several days (often 3–7 days, but sometimes later) and are usually small, grayish, and convex. Because the organism grows slowly and is highly fastidious, interpretation requires experienced microbiologists and often supplementary tests or observations.

Limitations and context: While Bordet-Gengou medium historically served as a standard for pertussis culture, growth can be variable due to sample quality and prior antibiotic exposure. Modern laboratories increasingly use molecular methods (such as PCR) for pertussis diagnosis, and other enriched media (such as Regan-Lowe) are used as alternatives or complements. Bordet-Gengou remains a notable example of early selective media for Bordetella pertussis.