Complex Class 1 Integron in a Clinical Escherichia coli Strain From Vietnam Carrying Both mcr-1 and bla NDM-1 .

The co-production of MCR and carbapenemase in Enterobacteriaceae has been previously reported. Here, we describe a clinical strain of Escherichia coli from Vietnam carrying both mcr-1 and bla _NDM-1 . Whole-genome sequencing showed that the genome of this strain consists of a 4,975,832-bp chromosome and four plasmids. The mcr-1 and bla _NDM-1 genes are located on IncI2 and IncA/C2-type plasmids, respectively. Genetic analysis revealed the presence of a multidrug-resistant region with the structure of a novel complex class 1 integron including a class 1 integron region bearing two 5' conserved segments and one 3' conserved segment and two complete structures of IS CR1 . The complex integron contains aminoglycoside resistance genes aadA2 , aadB , strA , strB , and aphA6 , quinolone resistance gene qnrA1 , extended-spectrum β-lactamase gene bla _{OXA- 4} , and a Tn 125 -like transposon bearing bla _NDM-1 . In addition, the dfrA12 - gcuF - aadA2 - cmlA1 - aadA1-qacH gene cassette array belonging to the sul3 -type integron was also identified, but the region found downstream of the gene cassette array is the IS 440 - tet(M) -IS 26 element instead of the sul3 gene. The results further support that Enterobacteriaceae isolates co-harboring mcr and bla _NDM are widely being distributed. The structural characteristics of the complex integron reveal that IS CR1 elements play an important role in the mobilization of bla _NDM-1 and the development of multidrug-resistant regions.
(Copyright © 2019 Le-Vo, Tran, Le, Matsumoto, Motooka, Nakamura, Jones, Iida and Cao.)