Killer activity at different pHs against Cryptococcus neoformans var. neoformans serotype A by environmental yeast isolates

Yeast isolates that share the same habitats as Cryptococcus neoformans var, neoformans serotype A in a restricted Mediterranean area were assayed in o rder to verify their killer activity against Cr. neoformans strains isolate d from clinical and environmental sources. Many of the environmental yeast isolates expressed the killer phenomenon against the assayed strains of Cr. neoformans. Two species of Candida: Candida parapsilosis and Candida famat a, and Pichia carsonii, were the most active killers at pH 4.6, 5.0 and 5.6 levels encountered in pigeon and canary guanos. Killer activity by C. para psilosis is reported for the first time. The authors hypothesized that the killer phenomenon exerted by yeast species with heavy killer activity again st Cr. neoformans would lend themselves for use as biological control agent s against sensitive strains of Cr. neoformans when directly inoculated into the habitats of Cr. neoformans.