Sensitivity to Natamycin1 (Pimaricin) of Fungi Isolated in Cheese Warehouses.

The sensitivity to natamycin of molds and yeasts isolated in cheese warehouses where natamycin has been used for various periods was determined. After several years of continuous use of natamycin no natamycin-insensitive molds and yeasts were found. In 26 strains of molds isolated in cheese warehouses it was not possible under laboratory conditions to decrease the sensitivity for natamycin. Besides the sensitivity of fungi to natamycin, production of mycotoxins by the isolated molds was investigated. Strains of Penicillium viridicatum , Aspergillus versicolor , and Penicillium cyclopium isolated in the warehouses produced, under experimental conditions, ochratoxin A, sterigmatocystin, and penicillic acid, respectively.