Natamycin as a selective antifungal agent in media for growth of Legionella spp.

The growth of 18 different Legionella sp. strains and 76 different yeast isolates was tested on buffered charcoal yeast extract medium supplemented with alpha-ketoglutarate (BCYE alpha medium) and with natamycin, an antifungal agent. Bacterial growth was no different on BCYE alpha medium made with or without natamycin, whereas complete inhibition of yeasts occurred in BCYE alpha medium containing 200 to 500 micrograms of natamycin per ml. Selective BCYE alpha media made with natamycin rather than anisomycin had no (formulation with vancomycin, polymyxin B, and agar) or little (formulation with cefamandole, polymyxin B, and agar) inhibitory effect on the growth of 14 different Legionella sp. bacteria. Natamycin is an inexpensive alternative to anisomycin in the formulation of selective BCYE alpha media.