A fluoroquinolone-resistant Acinetobacter baumannii without the quinolone resistance-determining region mutations.

Recently another MITE-like structure, called the integron mobilization unit (IMU), has been described flanking a defective class 1 integron harbouring a carbapenem resistance gene, blaGES-5, in a clinical Enterobacter cloacae strain. Although the IMU sequence is not related to the MITE reported in our study, IMU-based mobilization of the integron could be demonstrated using a transposase provided in trans. Similar mobilization has been described for MITEs. There are no data in the scientific literature on the prevalence of MITEs in clinical bacteria. This is the second report of this 439 bp MITE-like structure, but the first in a clinical strain of the emergent pathogenic species A. baumannii. Moreover, it is a unique structure surrounding an IMP-type carbapenemase, suggesting that this resistance-encoding integron can be mobilized by a transposition-like mechanism. Our study emphasizes the need to determine the genetic context of mobile elements to fully understand the history of and future potential for dissemination of resistance genes.