IncC bla-positive plasmid characterised from ST648 Escherichia coli.

Objectives: This study describes the characterisation of type 2 IncC plasmids pC-Ec20-KPC and pC-Ec2-KPC, carrying thebla gene, from two multiresistant Escherichia coli recovered in University Hospital of Larissa (Greece) in 2018.

Methods: E. coli strains Ec-2Lar and Ec-20Lar were recovered from rectal swabs of two patients during monthly surveillance cultures. Transfer experiments by conjugation were carried out using rifampicin-resistant E. coli A15 laboratory strain as recipient. bla-carrying plasmids were characterised by S1 profiling. Isolates were typed by MLST. Whole-genome sequencing was performed using the Sequel platform.

Results: Both E. coli isolates, belonging to ST648, transferred bla to E. coli A15 by conjugation. Plasmid analysis revealed that the transconjugants harboured bla-positive plasmids of different sizes. Analysis of plasmid sequences showed that in both isolates the bla gene was carried on a type 2 IncC plasmid (pC-Ec20-KPC and pC-Ec2-KPC, respectively). Both plasmids carried the ARI-B resistance island consisting of several resistance genes, intact and truncated copies of several mobile elements, and a 25 571-bp segment harbouring coding sequences for an iron transporter. The bla gene was part of transposon Tn4401a, which was bounded by 5-bp direct repeats (TCCTT) suggesting its transposition into the IncC plasmids.

Conclusion: To our knowledge, this is the first report on complete nucleotide sequences of type 2 IncC plasmids. These findings, which hypothesise the acquisition of KPC-2-encoding transposon Tn4401a by an IncC replicon, indicate the ongoing need for molecular surveillance studies of multidrug-resistant pathogens. In addition, they underline the increasing clinical importance of the IncC plasmid family.