RT Journal Article SR Electronic(1) A1 Peck, Kyong Ran A1 Kim, Min Ja A1 Choi, Ji Young A1 Kim, Hong Sun A1 Kang, Cheol-In A1 Cho, Yong Kyun A1 Park, Dae Won A1 Lee, Hee Joo A1 Lee, Mi Suk A1 Ko, Kwan SooYR 2012 T1 In vitro time-kill studies of antimicrobial agents against blood isolates of imipenem-resistant Acinetobacter baumannii, including colistin- or tigecycline-resistant isolates JF Journal of Medical Microbiology, VO 61 IS 3 SP 353 OP 360 DO https://doi.org/10.1099/jmm.0.036939-0 PB Microbiology Society, SN 1473-5644, AB The emergence of colistin or tigecycline resistance as well as imipenem resistance in Acinetobacter baumannii poses a great therapeutic challenge. The bactericidal and synergistic effects of several combinations of antimicrobial agents against imipenem-, colistin- or tigecycline-resistant A. baumannii isolates were investigated by in vitro time-kill experiments. Six imipenem-resistant A. baumannii blood isolates were examined in this study, including colistin- and tigecycline-susceptible, colistin-resistant but tigecycline-susceptible, and colistin-susceptible but tigecycline-resistant isolates. Time-kill studies were performed using five antimicrobial agents singly or in combinations (imipenem plus colistin, imipenem plus ampicillin-sulbactam, colistin plus rifampicin, colistin plus tigecycline, and tigecycline plus rifampicin) at concentrations of 0.5× and 1× their MICs. Only imipenem was consistently effective as a single agent against all six A. baumannii isolates. Although the effectiveness of combinations of 0.5× MIC antimicrobial agents was inconsistent, combination regimens using 1× MIC of the antimicrobial agents displayed excellent bactericidal activities against all six A. baumannii isolates. Among the combinations of 0.5× MIC antimicrobial agents, the combination of colistin and tigecycline showed synergistic or bactericidal effects against four of the isolates. This in vitro time-kill analysis suggests that antimicrobial combinations are effective for killing imipenem-resistant A. baumannii isolates, even if they are simultaneously resistant to either colistin or tigecycline. However, the finding that the combinations of 0.5× MIC antimicrobial agents were effective on only some isolates may warrant further investigation of the doses of combination agents needed to kill resistant A. baumannii., UL https://www.microbiologyresearch.org/content/journal/jmm/10.1099/jmm.0.036939-0