Culture is considered the gold standard for the identification of B. pertussis infection due to its specificity. Unfortunately, B. pertussis is a fastidious organism; it requires select growth factors and special culture media, making it difficult to culture. Preanalytical factors such as specimen collection method, adequacy of specimen, and specimen transport can adversely affect culture yield. Isolation techniques can also affect organism growth.
The highest success for isolation is during the first two weeks of illness when the patient is in the catarrhal and early paroxysmal stages. B. pertussis is strictly aerobic with an optimal growth temperature of 35 - 37°C. Regan-Lowe transport media and plates currently provide the best recovery and growth for culture. The morphology seen on the Gram stain would be described as gram-negative bacilli or coccobacilli as the bacterial organisms are very short rods. B. pertussis reduces nitrates, utilizes citrate, splits urea, and is catalase/oxidase/indole positive.
Susceptibility testing is rarely performed since there are very few recorded examples of resistant strains.
