Institut für Molekulare Infektionsbiologie, Universität Würzburg, Würzburg, Germany.
Int J Med Microbiol. 2013 Jan;303(1):1-8. doi: 10.1016/j.ijmm.2012.11.006. Epub 2013 Jan 10.
The largest EHEC outbreak up to now in Germany occurred in 2011. It was caused by the non-O157:H7 Shiga-toxinogenic enterohemorrhagic E. coli strain O104:H4. This strain encodes in addition to the Shiga toxin 2 (Stx2), responsible for the hemolytic uremic syndrome (HUS), several adhesins such as aggregative adherence fimbriae. Currently, there is no effective prophylaxis and treatment available for EHEC infections in humans. Especially antibiotics are not indicated for treatment as they may induce Stx production, thus worsening the symptoms. Alternative therapeutics are therefore desperately needed. We tested the probiotic Escherichia coli strain Nissle 1917 (EcN) for antagonistic effects on two O104:H4 EHEC isolates from the 2011 outbreak and on the classical O157:H7 EHEC strain EDL933. These tests included effects on adherence, growth, and Stx production in monoculture and co-culture together with EcN. The inoculum of each co-culture contained EcN and the respective EHEC strain either at a ratio of 1:1 or 10:1 (EcN:EHEC). Adhesion of EHEC strains to Caco-2 cells and to the mucin-producing LS-174T cells was reduced significantly in co-culture with EcN at the 1:1 ratio and very dramatically at the 10:1 ratio. This inhibitory effect of EcN on EHEC adherence was most likely not due to occupation of adhesion sites on the epithelial cells, because in monocultures EcN adhered with much lower bacterial numbers than the EHEC strains. Both EHEC strains of serotype O104:H4 showed reduced growth in the presence of EcN (10:1 ratio). EHEC strain EDL933 grew in co-culture with EcN only during the first 2h of incubation. Thereafter, EHEC counts declined. At 24h, the numbers of viable EDL933 was at or slightly below the numbers at the time of inoculation. The amount of Stx2 after 24h co-incubation with EcN (EcN:EHEC ratio 10:1) was for all 3 EHEC strains tested significantly reduced in comparison to EHEC monocultures. Obviously, EcN shows very efficient antagonistic activity on the EHEC strains of serotype O104:H4 and O157:H7 tested here regarding adherence to human gut epithelial cells, bacterial growth, and Stx2 production in vitro.
到目前为止，德国最大的肠出血性大肠杆菌爆发发生在 2011 年。它是由非 O157:H7 志贺毒素产生的肠出血性大肠杆菌 O104:H4 引起的。该菌株除了编码志贺毒素 2（Stx2）外，还编码几种黏附素，如聚集黏附菌毛。目前，人类感染肠出血性大肠杆菌尚无有效预防和治疗方法。特别是抗生素不适合治疗，因为它们可能会诱导 Stx 的产生，从而加重症状。因此，迫切需要替代疗法。我们测试了益生菌大肠杆菌菌株 Nissle 1917（EcN）对 2011 年爆发的两株 O104:H4 肠出血性大肠杆菌分离株和经典 O157:H7 肠出血性大肠杆菌菌株 EDL933 的拮抗作用。这些测试包括在单独培养和与 EcN 共同培养时对粘附、生长和 Stx 产生的影响。每种共培养物的接种物均含有 EcN 和相应的肠出血性大肠杆菌菌株，比例为 1:1 或 10:1（EcN:EHEC）。当 EcN 与肠出血性大肠杆菌菌株的比例为 1:1 时，肠出血性大肠杆菌菌株对 Caco-2 细胞和产生粘蛋白的 LS-174T 细胞的粘附显著降低，当 EcN 与肠出血性大肠杆菌菌株的比例为 10:1 时，粘附显著降低。EcN 对肠出血性大肠杆菌粘附的这种抑制作用很可能不是由于上皮细胞上粘附位点的占据，因为在单独培养物中，EcN 的粘附细菌数量远低于肠出血性大肠杆菌菌株。两种 O104:H4 血清型的肠出血性大肠杆菌菌株在 EcN 的存在下生长减少（10:1 比例）。EDL933 肠出血性大肠杆菌仅在孵育的前 2 小时与 EcN 共培养时生长。此后，肠出血性大肠杆菌的数量下降。在 24 小时时，活的 EDL933 的数量与接种时的数量相同或略低。与肠出血性大肠杆菌单独培养相比，用 EcN（EcN:EHEC 比例 10:1）共孵育 24 小时后，所有 3 株肠出血性大肠杆菌菌株的 Stx2 含量均显著降低。显然，EcN 对这里测试的 O104:H4 和 O157:H7 血清型肠出血性大肠杆菌菌株在粘附人肠道上皮细胞、细菌生长和 Stx2 产生方面具有非常有效的拮抗活性。
