The First Report of a Fully Sequenced Resistance Plasmid from .

The purpose of this study was to characterize mechanisms of plasmid-mediated antimicrobial resistance in . strain 2246 with resistance to ciprofloxacin, ceftriaxone and azithromycin was isolated from a human case of watery diarrhea in a Chinese public hospital. Resistance in strain 2246 to ceftriaxone and azithromycin was attributable to the presence of , and and ), respectively, which were co-located on a multidrug-resistant (MDR) plasmid p2246-CTXM. p2246-CTXM represented a novel IncFII-type MDR plasmid with a very complex chimera structure. Its master backbone was genetically closely related to the R100 plasmid, but p2246-CTXM had evolved to integrate additional R100-unrelated backbone regions as well as massive exogenous mobile elements that carried multiple resistance determinants. In p2246-CTXM together with its leading peptide gene , ) together with its regulatory genes and , and were captured by three different mobile elements Tn, the IS----IS unit, and a truncated IS--IS- transposition unit, respectively, all of which were harbored in a large Tn-family transposon Tn. p2246-CTXM still carried additional resistance determinants (mercury resistance), (aminoglycoside resistance), (chloramphenicol resistance), and (quaternary ammonium compound resistance). This is the first report of identifying a clinical strain simultaneously resistant to ciprofloxacin, ceftriaxone, and azithromycin, and determining the complete sequence of a resistance plasmid from .