Derepressed transfer properties leading to the efficient spread of the plasmid encoding carbapenemase OXA-48.

The current emergence of the carbapenemase OXA-48 among Enterobacteriaceae is related to the spread of a single IncL/M-type plasmid, pOXA-48a. This plasmid harbors the blaOXA-48 gene within a composite transposon, Tn1999, which is inserted into the tir gene, encoding a transfer inhibition protein. We showed that the insertion of Tn1999 into the tir gene was involved in a higher transfer frequency of plasmid pOXA-48a. This may likely be the key factor for the successful dissemination of this plasmid.