Multipronged impact of environmental temperature on Staphylococcus aureus infection by phage Kayvirus rodi:...

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.