Institute of Hygiene, University of Münster, Münster, Germany.
Department of Biological Sciences, University at Buffalo, Buffalo, USA.
Sci Rep. 2019 Dec 11;9(1):18777. doi: 10.1038/s41598-019-55332-2.
Shiga toxins (Stx) induce the symptoms of the life-threatening hemolytic uremic syndrome (HUS) and are the main virulence factors of enterohemorrhagic Escherichia coli (EHEC). The bacterial SOS response is the essential signal for high level production and release of Stx1/2. To assess the potential effectiveness of different antibiotics in blocking SOS response and Stx1/2 production, we constructed a reporter gene based test system that allows for the time-resolved, simultaneous read-out of the SOS response (recAP-cfp) and Stx1 production (stx1::yfp) in EHEC O157:H7 EDL933. We find that cells exposed to inhibitory or subinhibitory concentrations of ciprofloxacin did induce the SOS response, but not when the cells were exposed to rifaximine, azithromycin, tetracycline, gentamicin or ampicillin. Cell lysis and the peak in Stx1 production were substantially delayed with respect to the peak of the SOS response. We used this feature to show that adding transcriptional or translational inhibitors can block Stx1 production even after the SOS response is fully induced. RT-qPCR based tests with other clinically relevant EHEC isolates showed similar results for both Stx1 and Stx2. These observations suggest that transcriptional and translational inhibitors may be of value in treating EHEC infections.
志贺毒素（Stx）会引发危及生命的溶血性尿毒综合征（HUS）的症状，是肠出血性大肠杆菌（EHEC）的主要毒力因子。细菌 SOS 反应是高水平产生和释放 Stx1/2 的必要信号。为了评估不同抗生素在阻断 SOS 反应和 Stx1/2 产生方面的潜在效果，我们构建了一个基于报告基因的测试系统，该系统允许对 EHEC O157:H7 EDL933 的 SOS 反应（recAP-cfp）和 Stx1 产生（stx1::yfp）进行时间分辨、同时读取。我们发现，暴露于抑制或亚抑制浓度环丙沙星的细胞确实会诱导 SOS 反应，但当细胞暴露于利福昔明、阿奇霉素、四环素、庆大霉素或氨苄西林时则不会。与 SOS 反应的峰值相比，细胞裂解和 Stx1 产生的峰值大大延迟。我们利用这一特性表明，即使在 SOS 反应完全诱导后，添加转录或翻译抑制剂也可以阻断 Stx1 的产生。使用其他临床相关 EHEC 分离株进行基于 RT-qPCR 的测试，对 Stx1 和 Stx2 均得到了类似的结果。这些观察结果表明，转录和翻译抑制剂在治疗 EHEC 感染方面可能具有价值。
