Characterization of class 1 integrons and gene cassettes in clinical isolates of Klebsiella pneumoniae from Taiwan.

We surveyed the prevalence and contents of class 1 integrons in clinical Klebsiella pneumoniae isolates collected from Kaohsiung, Taiwan, during 2 periods (1993 and 2004). Class 1 integrons were present in 78 isolates (34.2%) from 1993 (n = 228) and 129 (32.9%) from 2004 (n = 392) and contained varied gene cassette number, type, and array. We found 2 atypical sul3-associated class 1 integrons and identified 26 different gene cassettes, including an aac(6')-Ib-cr cassette here firstly described in K. pneumoniae from Taiwan. The continuing evolution of class 1 integrons is threatening to undermine the effectiveness of antimicrobial therapy for K. pneumoniae.