Induction and nosocomial dissemination of carbapenem and polymyxin-resistant Klebsiella pneumoniae.

INTRODUCTION Polymyxins are antimicrobial agents capable of controlling carbapenemase-producing Klebsiella pneumoniae infection. METHODS We report a cluster of four patients colonized or infected by polymyxin-resistant and Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae. RESULTS Three patients were hospitalized in adjacent wards, and two were admitted to the intensive care unit. The index case maintained prolonged intestinal colonization by KPC-producing K. pneumoniae. Three patients received polymyxin B before the isolation of polymyxin-resistant K. pneumoniae. CONCLUSIONS Colonization by KPC-producing K. pneumoniae and previous use of polymyxin B may be causally related to the development of polymyxin-resistant microorganisms.