Risk factors for isolation of strains susceptible only to polymyxin among patients with Pseudomonas aeruginosa bacteremia.

We conducted a case-control study to identify risk factors associated with the isolation of Pseudomonas aeruginosa strains susceptible only to polymyxin from blood by comparing data between 16 patients with blood isolates that were susceptible only to polymyxins and 40 patients with blood isolates that were susceptible to carbapenems. The multivariable analysis showed that exposure to carbapenems was associated with the development of P. aeruginosa bacteremia susceptible only to polymyxin (odds ratio, 9.0; 95% confidence interval, 2.4 to 34.3; P = 0.001).