Ibekwe A Mark, Papiernik Sharon K, Grieve Catherine M, Yang Ching-Hong
USDA-ARS, U.S. Salinity Laboratory, 450 W-Big springs Roael, Riverside, CA 92507, USA.
Int J Microbiol. 2011;2011. doi: 10.1155/2011/421379. Epub 2010 Sep 8.
Persistence of Escherichia coli (E. coli) O157:H7 in the environment is a major concern to vegetable and fruit growers where farms and livestock production are in close proximity. The objectives were to determine the effects of preplant fumigation treatment on the survival of E. coli O157:H7 in two soils and the effects of indigenous bacterial populations on the survival of this pathogen. Real-time PCR and plate counts were used to quantify the survival of E. coli O157:H7 in two contrasting soils after fumigation with methyl bromide (MeBr) and methyl iodide (MeI). Ten days after fumigation, E. coli O157:H7 counts were significantly lower (P = .0001) in fumigated soils than in the non-fumigated. Direct comparison between MeBr and MeI within each soil indicated that these two fumigants showed similar impacts on E. coli O157:H7 survival. Microbial species diversity as determined by DGGE was significantly higher in clay soil than sandy soil and this resulted in higher initial decline in population in clay soil than in sandy soil. This study shows that if soil is contaminated with E. coli O157:H7, fumigation alone may not eliminate the pathogen, but may cause decrease in microbial diversity which may enhance the survival of the pathogen.
在农场与畜牧生产紧密相邻的蔬菜水果种植区，环境中大肠杆菌O157:H7的持续存在是种植者主要担忧的问题。本研究的目的是确定种植前熏蒸处理对两种土壤中大肠杆菌O157:H7存活的影响，以及本地细菌种群对该病原体存活的影响。采用实时荧光定量PCR和平板计数法来量化用溴甲烷（MeBr）和甲基碘（MeI）熏蒸后两种不同土壤中大肠杆菌O157:H7的存活情况。熏蒸十天后，熏蒸土壤中大肠杆菌O157:H7的数量显著低于未熏蒸土壤（P = 0.0001）。在每种土壤中对MeBr和MeI进行直接比较表明，这两种熏蒸剂对大肠杆菌O157:H7存活的影响相似。通过变性梯度凝胶电泳（DGGE）测定的微生物物种多样性在粘土中显著高于砂土，这导致粘土中种群数量的初始下降高于砂土。本研究表明，如果土壤被大肠杆菌O157:H7污染，仅熏蒸可能无法消除病原体，但可能会导致微生物多样性降低，从而可能提高病原体的存活率。
