Wang Rong, Kalchayanand Norasak, Bono James L
U.S. Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, P.O. Box 166, State Spur 18D, Clay Center, Nebraska 68933-0166, USA.
J Food Prot. 2015 Aug;78(8):1554-9. doi: 10.4315/0362-028X.JFP-15-009.
Bacterial biofilms are one of the potential sources of cross-contamination in food processing environments. Shiga toxin-producing Escherichia coli (STEC) O157:H7 and O111:H8 are important foodborne pathogens capable of forming biofilms, and the coexistence of these two STEC serotypes has been detected in various food samples and in multiple commercial meat plants throughout the United States. Here, we investigated how the coexistence of these two STEC serotypes and their sequence of colonization could affect bacterial growth competition and mixed biofilm development. Our data showed that E. coli O157:H7 strains were able to maintain a higher cell percentage in mixed biofilms with the co-inoculated O111:H8 companion strains, even though the results of planktonic growth competition were strain dependent. On solid surfaces with preexisting biofilms, the sequence of colonization played a critical role in determining the composition of the mixed biofilms because early stage precolonization significantly affected the competition results between the E. coli O157:H7 and O111:H8 strains. The precolonizer of either serotype was able to outgrow the other serotype in both planktonic and biofilm phases. The competitive interactions among the various STEC serotypes would determine the composition and structure of the mixed biofilms as well as their potential risks to food safety and public health, which is largely influenced by the dominant strains in the mixtures. Thus, the analysis of mixed biofilms under various conditions would be of importance to determine the nature of mixed biofilms composed of multiple microorganisms and to help implement the most effective disinfection operations accordingly.
细菌生物膜是食品加工环境中交叉污染的潜在来源之一。产志贺毒素大肠杆菌（STEC）O157:H7和O111:H8是能够形成生物膜的重要食源性病原体，在美国各地的各种食品样本和多家商业肉类加工厂中均检测到这两种STEC血清型共存。在此，我们研究了这两种STEC血清型的共存及其定殖顺序如何影响细菌生长竞争和混合生物膜的形成。我们的数据表明，尽管浮游生长竞争的结果因菌株而异，但大肠杆菌O157:H7菌株在与共同接种的O111:H8伴生菌株形成的混合生物膜中能够保持较高的细胞百分比。在已存在生物膜的固体表面上，定殖顺序在决定混合生物膜的组成方面起着关键作用，因为早期的预定殖显著影响了大肠杆菌O157:H7和O111:H8菌株之间的竞争结果。任一血清型的预定殖菌在浮游和生物膜阶段都能够胜过另一种血清型。各种STEC血清型之间的竞争相互作用将决定混合生物膜的组成和结构以及它们对食品安全和公共卫生的潜在风险，这在很大程度上受混合物中优势菌株的影响。因此，分析各种条件下的混合生物膜对于确定由多种微生物组成的混合生物膜的性质以及相应地帮助实施最有效的消毒操作具有重要意义。
