Laboratoire de Chimie Bactérienne, UMR7283, Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France.
Faculty of Exact and Natural Sciences, Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia.
PLoS Pathog. 2023 Sep 13;19(9):e1011602. doi: 10.1371/journal.ppat.1011602. eCollection 2023 Sep.
Phages are promising tools to fight antibiotic-resistant bacteria, and as for now, phage therapy is essentially performed in combination with antibiotics. Interestingly, combined treatments including phages and a wide range of antibiotics lead to an increased bacterial killing, a phenomenon called phage-antibiotic synergy (PAS), suggesting that antibiotic-induced changes in bacterial physiology alter the dynamics of phage propagation. Using single-phage and single-cell techniques, each step of the lytic cycle of phage HK620 was studied in E. coli cultures treated with either ceftazidime, cephalexin or ciprofloxacin, three filamentation-inducing antibiotics. In the presence of sublethal doses of antibiotics, multiple stress tolerance and DNA repair pathways are triggered following activation of the SOS response. One of the most notable effects is the inhibition of bacterial division. As a result, a significant fraction of cells forms filaments that stop dividing but have higher rates of mutagenesis. Antibiotic-induced filaments become easy targets for phages due to their enlarged surface areas, as demonstrated by fluorescence microscopy and flow cytometry techniques. Adsorption, infection and lysis occur more often in filamentous cells compared to regular-sized bacteria. In addition, the reduction in bacterial numbers caused by impaired cell division may account for the faster elimination of bacteria during PAS. We developed a mathematical model to capture the interaction between sublethal doses of antibiotics and exposition to phages. This model shows that the induction of filamentation by sublethal doses of antibiotics can amplify the replication of phages and therefore yield PAS. We also use this model to study the consequences of PAS on the emergence of antibiotic resistance. A significant percentage of hyper-mutagenic filamentous bacteria are effectively killed by phages due to their increased susceptibility to infection. As a result, the addition of even a very low number of bacteriophages produced a strong reduction of the mutagenesis rate of the entire bacterial population. We confirm this prediction experimentally using reporters for bacterial DNA repair. Our work highlights the multiple benefits associated with the combination of sublethal doses of antibiotics with bacteriophages.
噬菌体是对抗抗生素耐药细菌的有前途的工具，到目前为止，噬菌体疗法基本上是与抗生素联合进行的。有趣的是，包括噬菌体和广泛的抗生素在内的联合治疗会导致细菌杀伤增加，这种现象称为噬菌体-抗生素协同作用（PAS），这表明抗生素诱导的细菌生理变化改变了噬菌体繁殖的动力学。使用单噬菌体和单细胞技术，在使用头孢他啶、头孢氨苄或环丙沙星（三种诱导丝状化的抗生素）处理的大肠杆菌培养物中研究了噬菌体 HK620 的裂解周期的每个步骤。在亚致死剂量抗生素的存在下，激活 SOS 反应后会触发多种应激耐受和 DNA 修复途径。最显著的影响之一是抑制细菌分裂。结果，由于其表面积增大，大量细胞形成停止分裂但具有更高突变率的丝状体。由于抗生素诱导的丝状体的表面积增大，噬菌体很容易成为这些丝状体的靶标，这通过荧光显微镜和流式细胞术技术得到证实。与正常大小的细菌相比，丝状细胞中的吸附、感染和裂解发生得更频繁。此外，由于细胞分裂受损导致的细菌数量减少可能是 PAS 期间细菌更快消除的原因。我们开发了一个数学模型来捕获亚致死剂量的抗生素和噬菌体暴露之间的相互作用。该模型表明，亚致死剂量的抗生素诱导的丝状化可以放大噬菌体的复制，从而产生 PAS。我们还使用该模型研究 PAS 对抗生素耐药性出现的影响。由于感染的易感性增加，大量超突变丝状细菌有效地被噬菌体杀死。因此，即使添加少量噬菌体也会导致整个细菌群体的突变率大大降低。我们使用细菌 DNA 修复报告基因来实验验证这一预测。我们的工作强调了亚致死剂量抗生素与噬菌体联合使用的多种好处。
