SENSITIVITY OF AEROBIC SPORE-FORMING SPECIES OF THE GENUS BACILLUS TOTHE PTERIDINE COMPOUND O129

Discs containing the pteridine compound O129 at various concentrations may be useful in differentiating the following closely related specie s belonging to the genus Bacillus, viz. B. subtilis, B. licheniformis and B. pumilus; B. polymyxa and B. macerans; together with B. cereus a nd its subspecies B. cereus var. mycoides. At concentrations of 10 mu g O129, the ATCC type strain of B. subtilis was resistant whereas B, l icheniformis and B. pumilus were sensitive. However, B, subtilis was s ensitive to O129 at 150 mu g. Similar reactions differentiated the ATC C type strains of B. polymyxa and B. macerans. The ATCC type strain of B. cereus was resistant to O129 at both 150 mu g and 10 mu g, but its subspecies B. cereus var. mycoides (ATCC 28) was partially sensitive at 150 mu g concentration. When clinical isolates of B. cereus var. my coides were subsequently tested, this partial sensitivity was found to be a variable characteristic.