Interplay among IncA and blaKPC-Carrying Plasmids in Citrobacter freundii

Abstract

We report two KPC-producing Citrobacter freundii isolates from unrelated patients. In one case, bla_KPC-2 was harbored on a novel variant of a Tn4401 transposon of an IncN plasmid conjugated together with a coresident IncA plasmid, whereas in the other one, bla_KPC-3 was on a Tn4401a transposon located on an IncX3-IncA self-conjugative plasmid fusion. The interplay among plasmids carrying bla_KPC and the coresident IncA plasmids offers new information on plasmids coresident within clinically relevant enterobacteria.

Keywords: Citrobacter freundii; IncA; IncN; IncX3; KPC; Tn4401a; Tn4401i.

FIG 1

(a) Circular map of pIBAC_IncN plasmid compared with pKp148 (black circular box). Green arrows, conjugal transfer system of the plasmid; red arrow, bla_KPC gene; yellow arrows, mobile elements; white arrows, hypothetical proteins; purple arrow, replication protein repN; orange arrow, stability protein stdB. Gray circular box represents the plasmid backbone, and transposon Tn4401i is represented by a blue arrow. (b) Alignment in the position of interest between the sequence of Tn4401i and that of Tn4401b. −35 and −10, putative promoter regions; +1, putative transcription starting point; RBS, ribosome-binding site.

FIG 2

Linear map of pIBAC_IncA and pIBAC_IncX3_A. Arrows, direction of transcription of open reading frames (ORFs); rectangles, truncated ORFs. Replicons, partitioning genes, mobile elements, conjugal transfer genes, antibiotic resistance, bla_KPC-3, and other remaining genes are designated by violet, gray, yellow, green, red, blue, and white, respectively. Gray shaded area in upper part shows similarity of both IncA plasmids. Lower part shows the IncX3 plasmid region of pIBAC_IncX3_A and its insertion/fusion point, which is shown as striped yellow arrows/rectangles in the IncX3 region.