Impact of simulated microgravity on antibiotic resistance, biofilm formation and desiccation tolerance of vancomycin resistant Enterococcus faecium

Kurzfassung

Vancomycin resistant Enterococcus (E.) faecium (VRE) is a healthcare associated nosocomial pathogen causing serious diseases in immunocompromised patients. As previously shown, immune functions of astronauts during spaceflight are also dysregulated and, moreover, the treatment options are limited during long-term missions. Thus, the question arises how opportunistic and gastrointestinal bacteria, like VRE, may change regarding their resistance behavior to antibiotics, desiccation tolerance and biofilm formation under the loss of gravity. Therefore, we tested the change in antibiotic susceptibility of vancomycin susceptible (VSE, n=20), vancomycin resistant (VRE, n=17) and vancomycin-variable (VVE-B, n=5) E. faecium isolates to 22 different antibiotics, after incubation in simulated microgravity (sim. µg, by clinorotation) and as a control after seven days of incubation at 1 x g. Additionally, the clinical isolates were characterized regarding their biofilm formation and tolerance to desiccation after sim. µg. Three isolates increased in their minimal inhibitory concentration (MIC) to Vancomycin, Daptomycin and Fosfomycin after sim. µg. Whereas one isolate decreased in MIC to Oxacillin after sim. µg. Furthermore, we found four isolates which showed significant increase in biofilm formation and in total nine isolates that were more tolerant to desiccation after incubation under sim. µg. To prevent VRE infections and guarantee health of the crewmembers for future longterm space missions, it is essential to improve the understanding about the tenacity of VRE and gain knowledge about the influence of microgravity on the resistance behavior to different stressors. In this study sim. µg was generated by using a 2D Clinostat, which is a functional simulation and differs from real microgravity. Nevertheless, these first insights show how VRE are able to adapt in their resistance behavior and change due to spaceflight analog conditions like sim. µg.