In vitro activity of colistin (polymyxin E) against 3,480 isolates of gram-negative bacilli obtained from patients in Canadian hospitals in the CANWARD study, 2007-2008.

The in vitro activity of colistin was evaluated versus 3,480 isolates of gram-negative bacilli using CLSI broth microdilution methods. The MIC(90) of colistin was <= 2 mu g/ml against a variety of clinically important gram-negative bacilli, including Escherichia coli, Klebsiella spp., Enterobacter spp., Acinetobacter baumannii, and Pseudomonas aeruginosa. All multidrug-resistant (n = 76) P. aeruginosa isolates were susceptible to colistin (MIC, <= 2 mu g/ml). These data support a role for colistin in the treatment of infections caused by multidrug-resistant P. aeruginosa.