Isolation of Capnocytophaga species with a new selective medium

A selective medium (CAP) composed of a GC agar base supplemented with 1% hemoglobin, 1% Polyvitex, and an antibiotic mixture of polymyxin B (15 U/ml), vancomycin (5 micrograms/ml), trimethoprim (2.5 micrograms/ml), and amphotericin B (2.5 micrograms/ml) was compared with another selective medium (TBBP) and two nonselective media--a blood agar and a chocolate agar--to isolate Capnocytophaga species from 725 clinical specimens. These included sputa (467 specimens), throat swabs (116 specimens), oral ulcerations (35 specimens), and periodontal pockets (107 specimens). The recovery rate of Capnocytophaga species was significantly higher with the CAP medium (96%) than with the selective TBBP medium (52.2%), the nonselective blood agar (6.2%), and the chocolate agar (4.6%). Growth of the normal flora was best inhibited on CAP medium. Colony size and yellow-brown pigment formation were maximally expressed on chocolate agar and CAP medium, but gliding motility was mostly absent. We conclude that the CAP medium is an excellent medium for the recovery of Capnocytophaga species from contaminated clinical specimens.