Effects of transport temperature and medium on recovery of Bordetella pertussis from nasopharyngeal swabs

Abstract

We compared relative recoveries of Bordetella pertussis from simulated nasopharyngeal (NP) specimens incubated in three separate transport media at different temperatures. Transport media included one-half-strength Regan-Lowe (RL.5), Regan-Lowe with one-half-strength agar (RL.5A), and buffered charcoal-yeast extract agar supplemented with alpha-ketoglutarate, lincomycin, and anisomycin (BCYE alpha LA). For each transport medium, recovery of B. pertussis was least efficient after storage at 25 degrees C. The highest recovery of B. pertussis from a mixed culture was achieved with RL.5 at 4 degrees C. Overall, RL.5 and RL.5A were comparable as transport media whether held at 4 or 25 degrees C, but fewer organisms were recovered from BCYE alpha LA. In addition, Regan-Lowe (RL), Bordet-Gengou, and cyclodextrin media were compared as primary isolation media for recovering B. pertussis from simulated NP swabs held at 4 and 35 degrees C in RL.5 medium. The highest recovery of B. pertussis was obtained on RL primary isolation medium. Bordet-Gengou medium recovered only 80% and cyclodextrin medium recovered less than 60% of the numbers recovered on RL medium. Based on these results, refrigeration (4 degrees C) of NP swabs shipped in RL.5 transport medium and using RL as the primary isolation medium are recommended for recovering B. pertussis from swab specimens.