Jh. Jorgensen et al., DEVELOPMENT OF AN ANTIMICROBIAL SUSCEPTIBILITY TESTING METHOD SUITABLE FOR PERFORMANCE DURING SPACE-FLIGHT, Journal of clinical microbiology, 35(8), 1997, pp. 2093-2097
Very little is known regarding the effects of the microgravity environ
ment of space flight upon the action of antimicrobial agents on bacter
ial pathogens, This study was undertaken to develop a simple method fo
r conducting antibacterial susceptibility tests during a space shuttle
mission, Specially prepared susceptibility test research cards (bioMe
rieux Vitek, Hazelwood, Mo.) were designed to include 6 to 11 serial t
wofold dilutions of 14 antimicrobial agents, including penicillins, ce
phalosporins, a beta-lactamase inhibitor, vancomycin, erythromycin, te
tracycline, gentamicin, ciprofloxacin, and trimethoprim-sulfamethoxazo
le. MICs of the drugs were determined by visual reading of color end p
oints in the Vitek research cards made possible by incorporation of a
colorimetric growth indicator (alamarBlue; Accumed International, West
lake, Ohio), This study has demonstrated reproducible susceptibility r
esults in the testing of isolates of Staphylococcus aureus, group A St
reptococcus species, Enterococcus faecalis, Escherichia coli (beta-lac
tamase-positive and -negative strains), Klebsiella pneumoniae, Enterob
acter cloacae, and Pseudomonas aeruginosa, In some instances, the MICs
were comparable to those determined by a standard broth microdilution
method, while in some cases the unique test media and format yielded
slightly different values that were themselves reproducible, The propo
sed in-flight experiment will include inoculation of the Vitek cards o
n the ground prior to launch of the space shuttle, storage of inoculat
ed cards at refrigeration temperature aboard the space shuttle until e
xperiment initiation, and then incubation of the cards for 18 to 48 h
prior to visual interpretation of MICs by the mission's astronauts, Gr
ound-based studies have shown reproducible MICs following storage of i
noculated cards for 7 days at 4 to 8 degrees C to accommodate the miss
ion's time schedule and the astronaut's activities, For comparison, gr
ound-based control (normal gravity) MIC values will be generated by si
multaneous inoculation and incubation of a second set of test cards in
a laboratory at the launch site, This procedure can provide for a saf
e and compact experiment that should yield new information on the effe
cts of microgravity on the biological activities of various classes of
antibiotics.