[21]

Antibiotic Effectiveness in Simulated Microgravity.  H.N. Howard and D.M. Klaus, Dept. of Aerospace Engineering Sciences, University of Colorado, Boulder, CO.

   Several prior experiments have indicated that bacteria are able to proliferate in normally inhibitory concentrations of antibiotics during spaceflight.  Due to the inherent limitations associated with space-based biological research (few flight opportunities, limited sample numbers, difficult reproducibility, etc.), the reason for this apparent decrease in antibiotic efficacy has not been well characterized.  Although a definite causal mechanism has yet to be established, the quiescent fluid environment associated with microgravity is thought to contribute to the observed changes, perhaps as a consequence of reducing the uptake rate of the drug.

   This study focuses on characterizing antibiotic effectiveness in a simulated microgravity environment created using a clinostat.  A broth dilution method has been developed to determine the Minimum Inhibitory Concentration (MIC) of antibiotics in simulated microgravity for a model strain of E. coli (ATCC 4157).  Five different antibiotics were selected based on their mechanisms of action and associated microbial resistance factors (streptomycin, ampicillin, polymyxin B, tetracycline and nalidixic acid).  Determination of MIC for 1 g controls is contrasted with results achieved under clinorotation. 

   Future plans include exploring antibiotic effectiveness at simulated fractional and hyper-gravity levels, evaluating the influence of cell motility on effectiveness and investigating additional bacterial strains. 

(Supported by BioServe Space Technologies NASA NCC8-242)