Diversity of DHA-1-encoding plasmids in Klebsiella pneumoniae isolates from 16 French hospitals.

OBJECTIVES

To provide new insights into the spread of plasmidic cephalosporinase DHA-1, 16 strains of Klebsiella pneumoniae and a strain of Klebsiella variicola producing DHA-1 were isolated between January 2012 and December 2013 in six regions of France and two French overseas departments and territories.

METHODS

Disc diffusion assays, isoelectric focusing and PCRs were used to characterize the plasmidic DHA-1 β-lactamase. Plasmid analysis was performed by the method of Kado and Liu and WGS. Virulence of the strains was studied by biofilm formation and the survival of Drosophila.

RESULTS

The strains were of low virulence and had one to three plasmids including one of various sizes (∼40 to 319 kb) mediating DHA-1. Nine strains belonged to ST11 and possessed a pKPS30-type DHA-1 plasmid of the IncR (incompatibility) group. A strain of ST307 possessed pENVA, a DHA-1 plasmid of the IncH-type group. The seven remaining plasmids were unknown. Three belonged to the IncL/M group. They were closely related and their sequences were determined. One of the four remaining strains was chosen for further investigation. This strain of ST16 had two plasmids, a pUUH239.2-related plasmid and a new DHA-1 plasmid of ∼319 kb of IncHI2 type.

CONCLUSIONS

These findings demonstrate the major role of the pKPS30-type plasmid in the spread of DHA-1 cephalosporinase in France and provide evidence of two new emerging plasmids carrying this enzyme.