Emergence of colistin resistance during treatment of recurrent pneumonia caused by carbapenemase producing Klebsiella pneumoniae.

A 60-year-old woman received meropenem/colistin treatment for bilateral pneumonia caused by a ST15 carbapenemase producing Klebsiella pneumoniae. The patient recovered but re-infection with the same (ST15), but now colistin-resistant K. pneumoniae, occurred. The molecular mechanism of the emerged colistin resistance was identified as mgrB gene modification by insertion element (IS) IS903B.