Reciprocal resistance behavior of Enterococcus faecium to copper and vancomycin under the influence of simulated microgravity

Abstract

Since ancient times, the disinfecting properties of various metals have been known. When being integrated into different materials, these metals can be used to produce antimicrobial fabrics and surfaces for interiors meant to be sterile. This also applies for the modules of the International Space Station (ISS). Astronauts living here have an impaired immune system due to several unaccustomed conditions like micro gravitation, radiation, changed circadian rhythm, psychological stress and more. Hence, they are depending on best possible infection prevention. Studies have shown that some bacterial species develop antibiotic resistances or form stronger biofilms when being exposed to microgravitational conditions. As recent studies have stated a possible connection between glycopeptide and copper resistance, this work was meant to elucidate the reciprocal resistance development between copper and glycopeptides for Enterococcus faecium under the influence of simulated microgravity. To achieve this, a variety of experiments was conducted to investigate how E. faecium is altering its resistance behavior to glycopeptides and copper, after being exposed to low and high concentrations of copper for short and long-time incubation. To simulate microgravitational conditions a 2-D clinostat was used. It was shown that, in the used setups, microgravity does not have any influences on the copper and vancomycin resistance level of E. faecium, whereas an acclimatization effect to copper got visible for those strains not carrying the transferable copper resistance plasmid A17sv1. For the copper tolerant strain A17sv1, it could be seen that vancomycin stress is potentially triggering an augmented tolerance to higher copper concentrations. Taken together, the gained insights will serve as steppingstone for further essays on the copper resistance behavior of E. faecium and its adaptation to spaceflight conditions.