Investigation of diversity of plasmids carrying the bla TEM-52 gene

Abstract

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 blaTEM-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. © The Author 2011. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.