Institute of Microbiology and Epizootics, Freie Universität Berlin, Berlin, Germany.
Veterinary Centre for Resistance Research (TZR), Freie Universität Berlin, Berlin, Germany.
Microbiol Spectr. 2023 Aug 17;11(4):e0187423. doi: 10.1128/spectrum.01874-23. Epub 2023 Jun 12.
Persister cells are drug-tolerant bacteria capable of surviving antibiotic treatment despite the absence of heritable resistance mechanisms. It is generally thought that persister cells survive antibiotic exposure through the implementation of stress responses and/or energy-sparing strategies. Exposure to DNA gyrase-targeting antibiotics could be particularly detrimental for bacteria that carry prophages integrated in their genomes. Gyrase inhibitors are known to induce prophages to switch from their dormant lysogenic state into the lytic cycle, causing the lysis of their bacterial host. However, the influence of resident prophages on the formation of persister cells has only been recently appreciated. Here, we evaluated the effect of endogenous prophage carriage on the generation of bacterial persistence during Salmonella enterica serovar Typhimurium exposure to both gyrase-targeting antibiotics and other classes of bactericidal antibiotics. Results from the analysis of strain variants harboring different prophage combinations revealed that prophages play a major role in limiting the formation of persister cells during exposure to DNA-damaging antibiotics. In particular, we present evidence that prophage Gifsy-1 (and its encoded lysis proteins) are major factors limiting persister cell formation upon ciprofloxacin exposure. Resident prophages also appear to have a significant impact on the initial drug susceptibility, resulting in an alteration of the characteristic biphasic killing curve of persister cells into a triphasic curve. In contrast, a prophage-free derivative of Typhimurium showed no difference in the killing kinetics for β-lactam or aminoglycoside antibiotics. Our study demonstrates that induction of prophages increased the susceptibility toward DNA gyrase inhibitors in Typhimurium, suggesting that prophages have the potential for enhancing antibiotic efficacy. Bacterial infections resulting from antibiotic treatment failure can often be traced to nonresistant persister cells. Moreover, intermittent or single treatment of persister cells with β-lactam antibiotics or fluoroquinolones can lead to the formation of drug-resistant bacteria and to the emergence of multiresistant strains. It is therefore important to have a better understanding of the mechanisms that impact persister formation. Our results indicate that prophage-associated bacterial killing significantly reduces persister cell formation in lysogenic cells exposed to DNA-gyrase-targeting drugs. This suggests that therapies based on gyrase inhibitors should be favored over alternative strategies when dealing with lysogenic pathogens.
持久菌是一种能够在缺乏遗传抗性机制的情况下耐受抗生素治疗的耐药细菌。一般认为，持久菌通过实施应激反应和/或节能策略来存活抗生素暴露。暴露于靶向 DNA 回旋酶的抗生素可能对携带整合在其基因组中的原噬菌体的细菌特别有害。已知回旋酶抑制剂会诱导原噬菌体从休眠的溶原状态转变为裂解周期，导致其细菌宿主裂解。然而，驻留原噬菌体对持久菌形成的影响直到最近才被认识到。在这里，我们评估了内源性原噬菌体携带对沙门氏菌血清型鼠伤寒沙门氏菌暴露于靶向回旋酶的抗生素和其他杀菌抗生素期间细菌持久性形成的影响。分析携带不同原噬菌体组合的菌株变体的结果表明，原噬菌体在限制 DNA 损伤抗生素暴露期间持久菌形成方面起着重要作用。特别是，我们提供的证据表明，原噬菌体 Gifsy-1（及其编码的裂解蛋白）是限制环丙沙星暴露时持久菌形成的主要因素。驻留原噬菌体似乎也对初始药物敏感性有重大影响，导致持久菌的特征双峰杀伤曲线转变为三峰曲线。相比之下，鼠伤寒沙门氏菌的无原噬菌体衍生物在β-内酰胺或氨基糖苷类抗生素的杀伤动力学方面没有差异。我们的研究表明，原噬菌体的诱导增加了鼠伤寒沙门氏菌对 DNA 回旋酶抑制剂的敏感性，这表明原噬菌体有可能增强抗生素的功效。抗生素治疗失败导致的细菌感染通常可归因于非耐药持久菌。此外，用β-内酰胺或氟喹诺酮类抗生素间歇性或单次治疗持久菌会导致耐药菌的形成，并导致多耐药株的出现。因此，更好地了解影响持久菌形成的机制非常重要。我们的结果表明，在暴露于靶向 DNA 回旋酶的药物的溶原细胞中，与原噬菌体相关的细菌杀伤显著减少了持久菌的形成。这表明，在处理溶原性病原体时，应优先考虑基于回旋酶抑制剂的治疗方法，而不是替代策略。
