Kang D H, Fung D Y
Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-1600, USA.
J Food Prot. 1999 Apr;62(4):313-7. doi: 10.4315/0362-028x-62.4.313.
A new medium (Escherichia coli O157:H7 medium: EOH) was developed for differentiation between E. coli and E. coli O157:H7. The EOH medium was compared with sorbitol MacConkey agar (SMAC), which is the most popular medium to enumerate E. coli O157:H7. Several combinations of 35 dyes were evaluated to develop the new medium. Indigo carmine (0.03) g/liter) and phenol red (0.036 g/liter) were found as the best combination for differentiation between E. coli O157:H7 and E. coli and added to the basal agar medium (SMAC medium excluding neutral red and crystal violet) for EOH medium. On the dark blue EOH medium, E. coli produced a yellow color with clear zone, whereas E. coli O157:H7 produced a red color without clear zone. For differentiation between E. coli and E. coli O157:H7, EOH has much better potential than SMAC. Furthermore. the red color produced by normal E. coli in SMAC may mask the light gray color produced by E. coli O157: H7, whereas the yellow color with clear zone did not mask the red color without clear zone in the EOH medium. The recovery numbers of E. coli O157:H7 from inoculated ground beef, pork, and turkey were not significantly different between SMAC and EOH media (P > 0.05). The recovery rates of heat- and cold-injured E. coli O157:H7 also were not significantly different (P > 0.05).
开发了一种新的培养基（大肠杆菌O157:H7培养基：EOH）用于区分大肠杆菌和大肠杆菌O157:H7。将EOH培养基与山梨醇麦康凯琼脂（SMAC）进行了比较，SMAC是用于计数大肠杆菌O157:H7的最常用培养基。评估了35种染料的几种组合以开发新培养基。发现靛蓝胭脂红（0.03克/升）和酚红（0.036克/升）是区分大肠杆菌O157:H7和大肠杆菌的最佳组合，并添加到用于EOH培养基的基础琼脂培养基（不含中性红和结晶紫的SMAC培养基）中。在深蓝色的EOH培养基上，大肠杆菌产生带清晰区域的黄色，而大肠杆菌O157:H7产生不带清晰区域的红色。对于区分大肠杆菌和大肠杆菌O157:H7，EOH比SMAC具有更好的潜力。此外，正常大肠杆菌在SMAC中产生的红色可能会掩盖大肠杆菌O157:H7产生的浅灰色，而在EOH培养基中带清晰区域的黄色不会掩盖不带清晰区域的红色。在接种的碎牛肉、猪肉和火鸡肉中，SMAC和EOH培养基上大肠杆菌O157:H7的回收数量没有显著差异（P>0.05）。热损伤和冷损伤的大肠杆菌O157:H7的回收率也没有显著差异（P>0.05）。
