Simple and efficient method for clinical isolation of Bordetella pertussis

Commercially available Amies transport medium with charcoal and three isolation media were tested to assess their efficiency in the clinical isolation of B. pertussis. First, the isolation rates of B. pertussis were compared between direct inoculation of nasopharyngeal specimens and inoculation after being stored in Amies transport medium for eight hours or less. The organism was detected in 43 specimens from 29 patients with at least one of the two inoculation methods. The comparative isolation rates were 81% (35 of 43) for both direct inoculation and transport medium. Second, nasopharyngeal specimens were incubated for five days at 35 degrees C on the three media; Bordet Gengou Medium (BG) with 5 micrograms of CEX per ml, Cyclodextrin Solid Medium (CSM) with 5 micrograms of CEX per ml, and Charcoal Agar with 40 micrograms of CEX per ml. The organism was detected from 44 nasopharyngeal specimens of 20 patients on at least one of the three tested media. The comparative isolation rates were 91% (40 of 44) on BG with 5 micrograms of CEX per ml, 93% (41 of 44) on CSM with 5 micrograms of CEX per ml, and 91% (40 of 44) on CA with 40 micrograms of CEX per ml. Although no differences in the isolation rates were observed among the three media, the appearance of the colonies was earlier by one day on BG than the other two media. The detection of B. pertussis was occasionally easier on CA than on the other two because of its higher suppression of nasopharyngeal flora.(ABSTRACT TRUNCATED AT 250 WORDS)