Multipronged impact of environmental temperature on Staphylococcus aureus infection by phage Kayvirus rodi: Implications for biofilm control

Environmental cues sometimes have a direct impact on phage particle stability, as well as bacterial physiology and metabolism, having a profound effect on phage infection outcome. Here, we explore the impact of temperature on the interplay between phage Kayvirus rodi (phiIPLA-RODI) and its host, Staphylococcus aureus. Our results show that phiIPLA-RODI is a more effective predator at room (25 °C) compared to body temperature (37 °C) against planktonic cultures of several strains with varying degrees of phage susceptibility. This result differs from most known examples of temperature-dependent phage infection, in which optimum infection is correlated with the host growth rate. Further characterization of this phenomenon was carried out with strains IPLA15 and IPLA16, whose respective MICs were 7 log units and a 1-log unit higher at 37 °C than at 25 °C. Our results demonstrated that the phage also had a greater impact at room temperature during biofilm development and for the treatment of preformed biofilms. There was no difference in phage adsorption between the two temperatures for strain IPLA16. Conversely, adsorption of phiIPLA-RODI to IPLA15 was reduced at 37 °C compared to 25 °C. Moreover, confocal microscopy analysis indicated that the biofilm matrix of both strains has a greater content of PIA/PNAG at 37 °C than at 25 °C. Regarding infection parameters, we observed longer duration of the lytic cycle at 25 °C for both strains, and infection of IPLA15 by phiIPLA-RODI resulted in a smaller burst size at 37 °C than at 25 °C. Finally, we also found that the rate of phage resistant mutant selection was higher at 37 °C for both strains. Altogether, this information highlights the impact that bacterial responses to environmental factors have on phage-host interactions. Moreover, phage phiIPLA-RODI appears to be a highly effective candidate for biofilm disinfection at room temperature, while its efficacy in biofilm-related infections will require combination with other antimicrobials. Overall design: 6 samples were analyzed, correponding to 3 biological replicates of 24 hours biofilms formed by S. aureus IPLA16 at 25 ºC or 37 ºC

环境信号有时会直接影响噬菌体颗粒的稳定性，以及细菌的生理状态与代谢过程，进而对噬菌体的感染结局产生深远影响。本研究探讨了温度对Kayvirus rodi噬菌体（phiIPLA-RODI）与其宿主金黄色葡萄球菌（Staphylococcus aureus）之间相互作用的影响。研究结果显示，相较于体温（37℃），phiIPLA-RODI在室温（25℃）下对多种不同噬菌体敏感性程度的菌株的浮游菌培养物具有更优异的裂解活性。这一结果与多数已知的温度依赖性噬菌体感染案例不同，此类案例中最优感染效率与宿主生长速率呈正相关。我们选取菌株IPLA15与IPLA16对该现象进行了进一步表征：相较于25℃，二者在37℃下的最低抑菌浓度（Minimum Inhibitory Concentration，MIC）值分别升高7个对数单位与1个对数单位。研究结果同时证实，在生物膜形成阶段以及预形成生物膜的清除实验中，该噬菌体在室温下的作用效果同样更为显著。对于菌株IPLA16，两个温度下的噬菌体吸附率并无显著差异。与之相反，相较于25℃，37℃下phiIPLA-RODI对IPLA15的吸附率有所降低。此外，共聚焦显微镜分析结果表明，两种菌株的生物膜基质在37℃下的PIA/PNAG含量均显著高于25℃条件下。在感染参数方面，我们观察到两种菌株的裂解周期在25℃下均更长；且phiIPLA-RODI感染IPLA15时，37℃下的噬菌体裂解量相较于25℃时更低。最后，我们还发现，两种菌株在37℃下的噬菌体抗性突变体筛选率均更高。综上，本研究结果凸显了细菌对环境因素的应答在噬菌体-宿主相互作用中的重要影响。此外，phiIPLA-RODI噬菌体在室温下可作为一种高效的生物膜清除候选制剂，但其在生物膜相关感染中的应用效果则需与其他抗菌药物联合使用方能实现。实验整体设计：共分析6个样本，对应由金黄色葡萄球菌IPLA16在25℃或37℃下形成的24小时生物膜的3个生物学重复。