Maintenance of Antimicrobial Susceptibility of Acinetobacter baumannii in Modeled Microgravity

Abstract

OBJECTIVE: The purpose of this study was to evaluate the effect of a modeled microgravity environment on the antimicrobial resistance of Acinetobacter baumannii.

DESIGN: Clinical isolates of A. baumannii (n=10) in Mueller Hinton broth were grown in high aspect ratio vessels using a rotary cell culture system oriented to achieve either normal earth gravity (1XG) or low sheer modeled microgravity (LSMMG) conditions. After culture MICs were determined by Etest. Antimicrobials included in the study were amikacin, ampicillin/sulbactam, azithromycin, ceftazidime, gatifloxacin, gentamicin, imipenem, meropenem, minocycline, ticarcillin/clavulanic acid, tigecycline, and trimethoprim/sulfamethoxazole. Results were compared for MIC value and category interpretation (S, I, R).

RESULTS: Overall category agreement was 100% (360/360). 100% of MIC values compared were within one twofold dilution of each other.

CONCLUSION: Under these test conditions LSMMG had no apparent effect on the resistance pattern of A. baumannii.

ABBREVIATIONS: 1XG = normal earth gravity; LSMMG = low-shear modeled microgravity, MIC = minimum inhibitory concentration; S = susceptible; I = intermediate; R = resistant; NASA = National Aeronautics and Space Administration; RWV = rotating wall vessel; MDR = multi-drug resistant; TSA II – trypticase soy agar with 5% sheep blood; WHMC = Wilford Hall Medical Center; MHB = cation adjusted Mueller Hinton Broth; HARV = high aspect ratio vessel; RCCS = rotary cell culture system; mL = milliliter; RPM = rotations per minute.