Combination therapy with polymyxin B for the treatment of multidrug-resistant Gram-negative respiratory tract infections

Background. The treatment of infections caused by multidrug-resistant (MDR) Gram-negative organisms poses a therapeutic challenge. The use of polymyxin B has been resurrected specifically for this purpose. Patients and methods: We retrospectively reviewed the clinical and microbiological efficacy, and safety profile of polymyxin B in the treatment of MDR Gram-negative bacterial infections of the respiratory tract. Twenty-five critically ill patients received a total of 29 courses of polymyxin B administered in combination with another antimicrobial agent. Results: Patients were treated with intravenous, and/or aerosolized polymyxin B. Mean duration of polymyxin B therapy was 19 days (range 2-57 days). End of treatment mortality was 21%, and overall mortality at discharge was 48%. Nephrotoxicity was observed in three patients (10%) and did not result in discontinuation of therapy. Conclusions: Polymyxin B in combination with other antimicrobials can be considered a reasonable and safe treatment option for MDR Gram-negative respiratory tract infections in the setting of limited therapeutic options.