First Report of a Clinical, Multidrug-Resistant Enterobacteriaceae Isolate Coharboring Fosfomycin Resistance Gene fosA3 and Carbapenemase Gene blaKPC-2 on the Same Transposon, Tn1721

ABSTRACT In order to understand the genetic background and dissemination mechanism of carbapenem resistance and fosfomycin resistance in Enterobacteriaceae isolates, we studied a clinical Escherichia coli strain HS102707 isolate and an Enterobacter aerogenes strain HS112625 isolate, both of which were resistant to carbapenem and fosfomycin and positive for the bla KPC-2 and fosA3 genes. In addition, a clinical Klebsiella pneumoniae strain HS092839 isolate which was resistant to carbapenem was also studied. A 70-kb plasmid was successfully transferred to recipient E. coli J53 by a conjugation test. PCR and Southern blot analysis showed that bla KPC-2 was located on this plasmid. The complete sequence of pHS102707 showed that this plasmid belongs to the P11 subfamily (IncP1) and has a replication gene, several plasmid-stable genes, an intact type IV secretion system gene cluster, and a composite transposon Tn 1721 -Tn 3 that harbored bla KPC-2 . Interestingly, a composite IS 26 transposon carrying fosA3 was inserted in the Tn 1721-tnpA gene in pHS102707 and pHS112625, leading to the disruption of Tn 1721-tnpA and the deletion of Tn 1721-tnpR . However, only IS 26 with a truncated Tn 21-tnpR was inserted in pHS092839 at the same position. To our knowledge, this is the first report of fosA3 and bla KPC-2 colocated in the same Tn 1721 -Tn 3 –like composite transposon on a novel IncP group plasmid.