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Background

Most KPC-producing organisms have maintained susceptibility to polymyxins; however, development of resistance to polymyxins has been increasingly reported. One potential treatment modality is to optimize the use of combination therapy. Therefore, we evaluated the in vitro activity of doripenem, colistin sulfate, polymyxin B alone and in combination against KPC-producing K. pneumoniae.

Methods

In-vitro time-kill assays were performed for four non-duplicate KPC-3 producing K. pneumoniae isolates with the following antibiotics: doripenem, polymyxin B and colistin sulfate alone and in combination. Bacterial densities were determined at 0, 4, 8, 12, 24 and 48 hours. Bactericidal activity was defined as≥ 3-log 10 CFU/mL reduction from the starting inoculum. Synergism was defined as≥ 2-log 10 reduction with the combination when compared to the most active single agent at 24 hours.

Results …