Abstract
Bacteria of the genus Staphylococcus are persistent inhabitants of human spaceflight habitats and represent potential opportunistic pathogens. The effect of the human spaceflight environment on the growth and the frequency of mutations to antibiotic resistance in the model organism Staphylococcus epidermidis strain ATCC12228 was investigated. Six cultures of the test organism were cultivated in biological research in canisters–Petri dish fixation units for 122 h on orbit in the International Space Station (ISS) as part of the SpaceX-3 resupply mission. Asynchronous ground controls (GCs) consisted of identical sets of cultures cultivated for 122 h in the ISS Environmental Simulator at Kennedy Space Center. S. epidermidis exhibited significantly lower viable counts but significantly higher frequencies of mutation to rifampicin (Rif) resistance in space vs. GC cultures. The spectrum of mutations in the rpoB gene leading to RifR was altered in S. epidermidis isolates cultivated in the ISS compared to GCs. The results suggest that the human spaceflight environment induces unique physiologic stresses on growing bacterial cells leading to changes in mutagenic potential.
Highlights
Planning is currently underway for future long-duration missions through interplanetary space to the Moon, near-Earth asteroids, or Mars (NASA, 2015)
The observations that (i) astronaut immune function becomes dysregulated during long-term spaceflight (Guéguinou et al, 2009; Crucian et al, 2014; Taylor, 2015); (ii) certain opportunistic bacteria can upregulate virulence functions in spaceflight (Rosenzweig et al, 2014; Taylor, 2015); and (iii) spaceflight can alter the antibiotic resistance profiles of bacteria (Lapchine et al, 1986; Tixador et al, 1994) have underscored the importance of studying the causes and consequences of the development of bacterial antibiotic resistance in the human spaceflight environment
Understanding how microgravity affects the development of bacterial antibiotic resistance, but of bacterial growth and metabolism in general, has been difficult to achieve despite substantial interest in the topic
Summary
Planning is currently underway for future long-duration missions through interplanetary space to the Moon, near-Earth asteroids, or Mars (NASA, 2015). Both the National Research Council (NRC) and the International Space Exploration Coordination Group (ISECG) have assigned a high priority to studies aimed at better understanding astronaut health risks during space exploration; these agencies have recognized the International Space Station (ISS) as the best available platform to conduct research activities to address these challenges (International Space Exploration Coordination Group (ISECG), 2013; National Research Council [NRC], 2014). Opportunistic bacterial infections of the urinary tract, upper respiratory tract, and subcutaneous tissue have been documented from Shuttle missions STS-1 to STS-108 (Sams, 2009), and conjunctivitis, respiratory tract, and dental infections were documented among long-term inhabitants of space station Mir (Ball and Evans, 2001)
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