Fever-like temperature impacts onStaphylococcus aureusandPseudomonas aeruginosainteraction, physiology, and virulence bothin vitroandin vivo

Abstract

AbstractBackgroundStaphylococcus aureusandPseudomonas aeruginosacause a wide variety of bacterial infections and coinfections, showing a complex interaction that involves the production of different metabolites and metabolic changes. Temperature is a key factor for bacterial survival and virulence and within the host, bacteria could be exposed to an increment in temperature during fever development. We analyzed the previously unexplored effect of fever-like temperatures (39°C) onS. aureusUSA300 andP. aeruginosaPAO1 microaerobic mono- and co-cultures compared with 37°C, by using RNAseq and physiological assays includingin-vivoexperiments.ResultsIn general terms both temperature and co-culturing had a strong impact on both PA and SA with the exception of the temperature response of monocultured PA. We studied metabolic and virulence changes on both species. Altered metabolic features at 39°C included arginine biosynthesis and the periplasmic glucose oxidation inS. aureusandP. aeruginosamonocultures respectively. When PA co-cultures were exposed at 39°C they upregulated ethanol oxidation related genes along with an increment in organic acid accumulation. Regarding virulence factors, monocultured SA showed an increase in the mRNA expression of theagroperon andhld, pmsαandpmsβgenes at 39°C. Supported by mRNA data, we performed physiological experiments and detected and increment in hemolysis, staphylxantin production and a decrease in biofilm formation at 39°C. On the side of PA monocultures, we observed increase in extracellular lipase and protease and biofilm formation at 39°C along with a decrease in motility in correlation with changes observed at mRNA abundance. Additionally, we assessed host-pathogen interaction bothin-vitroandin-vivo.S. aureusmonocultured at 39°C showed a decrease in cellular invasion and an increase in IL-8 -but not in IL-6- production by A549 cell line. PA also decreased its cellular invasion when monocultured at 39°C and did not induce any change in IL-8 or IL-6 production. PA strongly increased cellular invasion when co-cultured at 37°C and 39°C. Finally, we observed increased lethality in mice intranasally inoculated withS. aureusmonocultures pre-incubated at 39°C and even higher levels when inoculated with co-cultures. The bacterial burden forP. aeruginosawas higher in liver when the mice were infected with co-cultures previously incubated at 39°C comparing with 37°C.ConclusionOur results highlight a relevant change in the virulence of bacterial opportunistic pathogens exposed to fever-like temperatures in presence of competitors, opening new questions related to bacteria-bacteria and host-pathogen interactions and coevolution.