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Updated: Jan 27, 2026

Identification of Fatty Acids in Bacillus cereus
Published on: December 5, 2016
Detectability and Precision of the AOAC Bacillus stearothermophilus Disc Assay Demonstrated in the 1981 FDA Split
J T Peeler1, J E Leslie1, J E Barnett1
1Division of Microbiology, Food and Drug Administration, 1090 Tusculum Avenue, Cincinnati, Ohio 45226.
Abstract:
Four blind duplicate milk samples containing β-lactam residues were analyzed by 149 analysts at 47 laboratories. Four official variations were used: (a) antibiotic 4 (A4) agar and 55°C incubation, (b) A4 agar and 64°C incubation, (c) PM indicator (PMI) agar and 55°C incubation, and (d) PMI agar and 64°C incubation. A β-lactam concentration of 0.008 IU/ml was detectable 100% of the time by variations a, b, and c and 98% of the time by variation d, with average zone diameters of 18.7, 17.7, 16.4 and 17.6 mm, respectively. The 0.005 IU/ml concentration was detected 92% of the time by variation a, 99% by b, 57% by c and 89% by d, with average zone diameters of positive units of 16.3, 15.5, 14.9 and 15.2 mm, respectively.
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