Ahmed Nahed M, Conner Donald E
Auburn University, Department of Poultry Science, Food Technology Institute, and Alabama Agricultural Experiment Station, Auburn, Alabama 36849-5416.
J Food Prot. 1995 Apr;58(4):357-360. doi: 10.4315/0362-028X-58.4.357.
Efficacies of plating media for recovering heated Escherichia coli O157:H7 were determined and compared. To compare populations of recovered cells, suspensions of cells (three isolates, four replications/isolate) were heated at 50, 55, or 60°C, and then inoculated onto eight media: PCA-PA (plate count agar with 1% pyruvic acid [PA]), MSA (MacConkey sorbitol agar), MSA-Mg (MSA with 0.025% MgSO), MSA-PA (MSA with 1% PA), MSA-MUG (MSA with 0.005% 4-methylumbelliferyl-β-d-glucuronide (MUG), PRSA-MUG (phenol red sorbitol agar [PSRA] with 0.005% MUG), PRSA-PA (PRSA with 1% PA), and TSA-PA (tryptic soy agar with 1% PA). Recovery was consistently higher ( < 0.05) with PRSA-MUG and PRSA-PA. At 50, 55, and 60°C, mean numbers (log CFU/ml) of recovered cells on PRSA-MUG were 4.42, 4.62, and 3.32, respectively, as compared to 2.78, 2.08, and 1.63, respectively, on MSA. PCA-PA and TSA-PA were less effective than PRSA media, but better than MSA media. Thus, PRSA with MUG or PA was an effective medium for recovering heated cells of E. coli O157:H7; whereas MSA failed to detect sublethally injured cells. Furthermore, addition of Mg, PA, or MUG to MSA further compromised this medium.
测定并比较了用于复苏加热后的大肠杆菌O157:H7的平板培养基的效果。为了比较复苏细胞的数量，将细胞悬液（三种菌株，每种菌株四个重复）在50、55或60°C下加热，然后接种到八种培养基上：PCA-PA（含1%丙酮酸[PA]的平板计数琼脂）、MSA（麦康凯山梨醇琼脂）、MSA-Mg（含0.025%硫酸镁的MSA）、MSA-PA（含1%PA的MSA）、MSA-MUG（含0.005%4-甲基伞形酮基-β-D-葡萄糖醛酸苷[MUG]的MSA）、PRSA-MUG（含0.005%MUG的酚红山梨醇琼脂[PSRA]）、PRSA-PA（含1%PA的PRSA）和TSA-PA（含1%PA的胰蛋白胨大豆琼脂）。PRSA-MUG和PRSA-PA的复苏率始终较高（<0.05）。在50、55和60°C下，PRSA-MUG上复苏细胞的平均数量（log CFU/ml）分别为4.42、4.62和3.32，而MSA上分别为2.78、2.08和1.63。PCA-PA和TSA-PA的效果不如PRSA培养基，但优于MSA培养基。因此，含MUG或PA的PRSA是复苏加热后的大肠杆菌O157:H7细胞的有效培养基；而MSA无法检测到亚致死损伤的细胞。此外，向MSA中添加镁、PA或MUG会进一步损害该培养基。
