Systematic screening of 42 major VRE Enterococcus faecium strains towards changes in the antibiotic resistance, biofilm formation and desiccation tolerance after exposure to simulated microgravity

Abstract

Vancomycin resistant Enterococcus (E.) faecium (VRE) is a healthcare associated pathogen causing serious diseases in immunocompromised patients. As previously shown, immune functions of astronauts during spaceflight are dysregulated, increasing infection risk with endogenous and exogenous pathogens. Additionally, treatment options are limited during long-term missions. Thus, the question arises how opportunistic gastrointestinal bacteria, like E. faecium, may change in regards to their antimicrobial susceptibility, desiccation tolerance and biofilm formation under the loss of gravity. We tested the changes in antibiotic susceptibility of Vancomycin susceptible (VSE), Vancomycin resistant (VRE) and Vancomycin-variable (VVE-B) E. faecium isolates to 22 different antibiotics, after 7 days of incubation in simulated microgravity (sim. µg) and at normal gravity (1 g). All isolates were also characterized regarding their biofilm formation and tolerance to desiccation after sim. µg. We observed in- and decrease in MIC for seven isolates to Ceftarolin, Gentamycin, Moxifloxacin, Oxacillin, Rifampicin, Synercid and Vancomycin after sim. µg. Moreover, 55 % (23/42 isolates) showed an increase in biofilm formation and 59 % (25/42) increase in desiccation tolerance after sim. µg. This study provides first insights on how E. faecium is able to adapt in resistance behavior and change due to spaceflight analog conditions like sim. µg. The found alterations distinctly demonstrate the adaptability of E. faecium while also showing a great variability to sim. µg. To prevent VRE infections and guarantee health of the crewmembers for future long-term 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.