Microbial Food Safety Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania 19038, USA.
Foodborne Pathog Dis. 2010 Aug;7(8):935-43. doi: 10.1089/fpd.2009.0503.
In a previous study we showed that an Escherichia coli O157:H7 strain that was unable to form biofilm was retained in large numbers in dual-strain biofilms formed with an E. coli O-:H4 companion strain. In this study we tested additional companion strains for their ability to retain E. coli O157:H7 strain 0475s. Companion strains producing biofilm that withstood aggressive washes were able to significantly increase serotype O157:H7 retention. Dual-strain biofilms with certain companion strains retained higher percentages of strain 0475s, and that ability was independent of biofilm total cell numbers. Tests with additional non-biofilm-forming E. coli O157:H7 strains showed that enhancement by companion strains was not unique to strain 0475s. Experiments using an E. coli companion strain with deletions of various curli and cellulose genes indicated that dual-strain biofilm formation was dependent on companion strain properties. Strain 0475s was not able to generate biofilm or persist on plastic when grown in broth with a biofilm-forming companion and separated by a 0.2 microm porous membrane, indicating a requirement for intimate contact with the companion strain. When dual-strain biofilms and planktonic cells were challenged with 5% H(2)O(2), strain 0475 showed greater survival in biofilms with certain companion strains compared to the corresponding planktonic cells. The results of this study indicate that non-biofilm-forming E. coli O157:H7 strains are retained on solid surfaces associated with biofilms generated by companion strains. However, properties other than biofilm mass enable certain companion strains to retain greater numbers of E. coli O157:H7.
在之前的研究中,我们发现一株不能形成生物膜的大肠杆菌 O157:H7 菌株与一株大肠杆菌 O-:H4 伴随菌株形成的双菌株生物膜中大量保留。在这项研究中,我们测试了其他伴随菌株保留大肠杆菌 O157:H7 菌株 0475s 的能力。能够抵抗强烈冲洗的产生生物膜的伴随菌株能够显著增加血清型 O157:H7 的保留率。某些伴随菌株的双菌株生物膜保留了更高百分比的 0475s 菌株,这种能力独立于生物膜总细胞数量。用额外的非生物膜形成大肠杆菌 O157:H7 菌株进行的测试表明,伴随菌株的增强作用并非仅针对 0475s 菌株。使用具有各种卷曲和纤维素基因缺失的大肠杆菌伴随菌株进行的实验表明,双菌株生物膜形成依赖于伴随菌株的特性。当在含有形成生物膜的伴随菌株的肉汤中生长并用 0.2 微米多孔膜分离时,0475s 菌株不能在塑料上形成生物膜或持续存在,表明需要与伴随菌株密切接触。当双菌株生物膜和浮游细胞受到 5% H(2)O(2)的挑战时,与某些伴随菌株相比,0475s 菌株在生物膜中表现出更高的存活率。本研究的结果表明,非生物膜形成的大肠杆菌 O157:H7 菌株在与伴随菌株生成的生物膜相关的固体表面上保留。然而,除了生物膜质量之外的特性使某些伴随菌株能够保留更多数量的大肠杆菌 O157:H7。