Fever-like temperature impacts on Staphylococcus aureus and Pseudomonas aeruginosa interaction, physiology, and virulence both in vitro and in vivo

Abstract

Staphylococcus aureus and Pseudomonas aeruginosa are two bacterial species that cause a wide variety of infections and coinfections. The interaction between these species is complex and involves the production of different metabolites and metabolic changes. The impact of elevated body temperature, such as fever, on the physiology and interaction of these pathogens remains poorly understood. Therefore, the aim of this work was to analyze the effect of moderate fever-like temperatures (39°C) on S. aureus USA300 and P. aeruginosa PAO1 mono- and co-cultures in comparison with 37°C, by using RNAseq and physiological assays in microaerobiosis. Both bacterial species showed metabolic alterations in response to temperature but also in response to the competitor. Organic acid production and nitrite content in the supernatant were altered both by the presence of the competitor and the incubation temperature. Interaction ANOVA showed that, in S. aureus, gene expression presented interaction between the temperature and the presence of the competitor. Among these genes, the most relevant were the agr operon and three of its direct target genes psmβ, psmβ2 and hld. In the A549 epithelial lung cell line, fever-like temperatures impacted in vitro virulence, antibiotic resistance, cell invasion, and cytokine production. In agreement with the in vitro assays, the survival of mice that had been intranasally inoculated with S. aureus monocultures pre-incubated at 39°C showed reduced survival after 10 days. An even higher mortality of around 30% was observed in mice that had been inoculated with co-cultures pre-incubated at 39°C. The bacterial burden in the lungs, kidney, and liver was higher for both species when the mice were infected with co-cultures previously incubated at 39°C. Our results highlight a relevant change in the virulence of bacterial opportunistic pathogens exposed to fever-like temperatures, opening new questions related to bacteria-bacteria and host-pathogen interactions and coevolution.