Objectives: To investigate the diversity of plasmids that carry bla(TEM-52) genes among Escherichia coli and Salmonella enterica originating from animals, meat products and humans.
Methods: A collection of 22 bla(TEM-52)-encoding plasmids was characterized by restriction fragment length polymorphism (RFLP), replicon typing (by PCR or replicon sequencing), susceptibility testing, assessment of plasmid ability to self-transfer by conjugation and typing of the genetic environment of the bla(TEM-52) gene. Detected IncI1 plasmids underwent further plasmid multilocus sequence typing.
Results: RFLP profiles demonstrated dissemination of bla(TEM-52) in Denmark (imported meat from Germany), France, Belgium and the Netherlands from 2000 to 2006 by mainly two different plasmids, one encoding bla(TEM-52b) (IncX1A, 45 kb) and the other bla(TEM-52c) (IncI1, 80 kb). In addition, bla(TEM-52b) was also found to be located on various other plasmids belonging to IncA/C and IncL/M, while bla(TEM-52c) was found on IncN-like as well as on IncR plasmids. In the majority of cases (n = 21) the bla(TEM-52) gene was located on a Tn3 transposon. Seven out of 10 bla(TEM-52) plasmids tested in conjugation experiments were shown to be capable of self-transfer to a plasmid-free E. coli recipient.
Conclusions: The bla(TEM-52) gene found in humans could have been transmitted on transferable plasmids originating from animal sources. Some of the bla(TEM-52) plasmids carry replicons that differ from the classical ones. Two novel replicons were detected, IncX1A and IncN-like. Unlike its predecessor bla(TEM-1), the bla(TEM-52) gene was not detected on F-type replicons suggesting that this gene evolved on other types of plasmid scaffolds.