Lancette G A, Harmon S M
J Assoc Off Anal Chem. 1980 May;63(3):581-6.
A collaborative study was conducted in 15 laboratories to evaluate 2 different techniques for enumerating Bacillus cereus in foods. A direct plating technique using mannitol-egg yolk-poly-myxin agar and a most probable number (MPN) technique using trypticase-soy-polymyxin broth were compared for the enumeration of high and low populations of B. cereus in mashed potatoes. The collaborative results showed that the overall mean recovery obtained with the low population level was essentially the same by both techniques. However, the overall mean recovery was significantly higher by the direct plating technique at the high population level. A statistical evaluation of the data also showed that the direct plating technique had better repeatability and reproducibility than did the MPN technique at both the high and low population levels. These results suggest that the MPN technique is suitable for examining foods containing low populations of B. cereus, but that the direct plating technique is preferable for foods that contain a high population of this organism. The confirmatory technique used in the proposed method is reliable for presumptive identification of isolates as B. cereus. The method has been adopted as official first action.
在15个实验室开展了一项合作研究，以评估两种不同的食品中蜡样芽孢杆菌计数技术。比较了使用甘露醇-蛋黄-多粘菌素琼脂的直接平板计数技术和使用胰蛋白胨大豆多粘菌素肉汤的最大可能数（MPN）技术对土豆泥中高浓度和低浓度蜡样芽孢杆菌的计数情况。合作研究结果表明，两种技术对低浓度菌液的总体平均回收率基本相同。然而，对于高浓度菌液，直接平板计数技术的总体平均回收率显著更高。对数据的统计评估还表明，在高浓度和低浓度菌液水平下，直接平板计数技术比MPN技术具有更好的重复性和再现性。这些结果表明，MPN技术适用于检测蜡样芽孢杆菌含量低的食品，但对于含有高浓度该菌的食品，直接平板计数技术更可取。所提出方法中使用的确证技术对于将分离株推定为蜡样芽孢杆菌是可靠的。该方法已被采用为首次官方方法。
