Category: Fellows Posters
Acinetobacter Baumannii possess inherent and acquired resistance mechanisms that have rendered most antibiotics inactive. Dual therapy including COL given in combination with meropenem (MEM) or tigecycline (TGC) has been shown to be successful in eradicating A. baumanniiinfections complicated by Multidrug-Resistance (MDR). Numerous methods exist to evaluate in vitro synergy; with time-kill analysis (TKA) and checkerboard testing (CB) being most widely used. The objective of this study was to assess and compare the synergy presented through various synergy testing methods including minimum inhibition concentration (MIC) testing of antimicrobials in combination, CB, and TKA in 50 A. baumannii strains.
The MIC testing of COL in the presence of MEM or TGC showed a >2- fold reduction in 96% and 80% of the 50 strains for each combination, respectively. CB revealed synergy in 64% of strains utilizing the COL+MEM combination, while synergy was observed in 22% of the strains with the COL+TGC dual therapy. In TKA, synergy was observed in 90% and 64% of the strains with the use of the COL+MEM and COL+TGC combinations, respectively.
Among the methods tested, TKA was the most consistent in demonstrating synergy for both the COL+MEM and COL+TGC combinations. Nevertheless, the results of this study show different synergy methods produce differing results. Further research is warranted to establish the best synergy testing modality for determiningin vivosuccess.