Selective medium for Branhamella catarrhalis with acetazolamide as a specific inhibitor of Neisseria spp.

Several semiselective media for Branhamella catarrhalis have been proposed. These media allow growth of all members of the family Neisseriaceae, and further differentiation is necessary. By addition of 10 micrograms of acetazolamide, a carbonic anhydrase inhibitor, per ml and incubation in air, a medium was created which reduced growth of Neisseria spp. When saliva samples from 178 healthy schoolchildren were screened for the presence of B. catarrhalis, the carrier rate for this organism was estimated to be 48.9% with the selective medium compared with 12.4% when a semiselective medium, which contains only 10 micrograms of vancomycin, 5 micrograms of trimethoprim, and 2 micrograms of amphotericin B per ml, was used and 6.2% when a nonselective blood agar plate was used. The number of Neisseria spp. isolated dropped from 297 on the semiselective agar to 55 on the selective agar.