Variability of Alternaria alternata: biochemical and immunological characteristics of culture filtrates from seven isolates.

Biochemical variability of culture filtrates from the common allergenic mold Alternaria alternata was studied. Differences between culture filtrates from 7 different isolates and between 4 batches of culture filtrate from the same isolate were observed, suggesting the unreliability of presently employed biochemical methods in the routine standardization of mold allergens and the possibility of difficulties in developing standard techniques for their purification. Dextranases, cellulases, and agarases, found in one culture filtrate, may be a further source of problems in laboratory techniques employing A. alternata. The proportions of nitrogen:carbohydrate:dialyzed dry weight were different in culture filtrates from each isolate. Polysaccharides in culture filtrates from 3 of the 7 isolated contained glucose, mannose, xylose, galactose, and a fifth, unidentified sugar. Polysaccharides from one isolate lacked xylose, and the fifth sugar was not demonstrable in 4 of the isolates. Despite the biochemical differences, extensive antigenic cross-reactivity between different isolates was found in precipitin studies and inhibition of antibody binding.