Center for Food Safety, University of Georgia, 1109 Experiment Street, Griffin, Georgia 30223-1797, USA.
J Food Prot. 2009 Oct;72(10):2028-37. doi: 10.4315/0362-028x-72.10.2028.
Survival and internalization characteristics of Escherichia coli O157:H7 in iceberg, romaine, and leaf lettuce after inoculation of leaf surfaces and soil were determined. A five-strain mixture of E. coli O157:H7 in water and cow manure extract was used as an inoculum for abaxial and adaxial sides of leaves at populations of 6 to 7 log and 4 log CFU per plant. The five strains were individually inoculated into soil at populations of 3 and 6 log CFU/g. Soil, leaves, and roots were analyzed for the presence and population of E. coli O157:H7. Ten (4.7%) of 212 samples of leaves inoculated on the adaxial side were positive for E. coli O157:H7, whereas 38 (17.9%) of 212 samples inoculated on the abaxial side were positive. E. coli O157:H7 survived for at least 25 days on leaf surfaces, with survival greater on the abaxial side of the leaves than on the adaxial side. All 212 rhizosphere samples and 424 surface-sanitized leaf and root samples from plants with inoculated leaves were negative for E. coli O157:H7, regardless of plant age at the time of inoculation or the location on the leaf receiving the inoculum. The pathogen survived in soil for at least 60 days. Five hundred ninety-eight (99.7%) of 600 surface-sanitized leaf and root samples from plants grown in inoculated soil were negative for E. coli O157:H7. Internalization of E. coli O157:H7 in lettuce leaves and roots did not occur, regardless of the type of lettuce, age of plants, or strain of E. coli O157:H7.
研究了经叶面和土壤接种后，大肠杆菌 O157:H7 在冰山生菜、罗马生菜和叶用莴苣中的存活和内化特性。采用大肠杆菌 O157:H7 的五株混合菌在水中和牛粪便提取物中的混合物作为接种物，以 6 到 7 对数和 4 对数 CFU/株的浓度接种于叶片的下表皮和上表皮。将这 5 株菌分别以 3 和 6 对数 CFU/g 的浓度接种到土壤中。对土壤、叶片和根系进行分析，以确定是否存在和检测大肠杆菌 O157:H7 的数量。在叶面接种的 212 个样本中，有 10 个（4.7%）在上表皮检测到大肠杆菌 O157:H7 呈阳性，而在背面接种的 212 个样本中，有 38 个（17.9%）呈阳性。大肠杆菌 O157:H7 在叶片表面至少存活 25 天，在叶片背面的存活时间比在叶片正面更长。所有接种叶片的植物的 212 个根际样本和 424 个叶面和根表面消毒样本均未检出大肠杆菌 O157:H7，无论接种时植物的年龄大小或接种部位在哪。该病原体在土壤中至少存活 60 天。在接种土壤中生长的植物的 600 个叶面和根表面消毒样本中，有 598 个（99.7%）未检出大肠杆菌 O157:H7。无论生菜的种类、植物的年龄或大肠杆菌 O157:H7 的菌株如何，大肠杆菌 O157:H7 均未在生菜叶片和根系内化。
