Association between colistin resistance and broad-spectrum recipient deficiency in Klebsiella pneumoniae.

A colistin-resistant mutant of Klebsiella pneumoniae served well as a donor but not as a recipient in conjugation. A nearly 1,000-fold difference between colistin-susceptible and colistin-resistant forms of this strain was observed by using donors of plasmids of four incompatibility groups. Recipient efficiency was not restored by filter matings.