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Closed Access item Class 1 and class 2 integrons in non-prevalent serovars of Salmonella enterica: structure and association with transposons and plasmids

Authors:Rodríguez, Irene
Martín, M. Cruz
Mendoza, M. Carmen
Rodicio, M. Rosario
Keywords:Multidrug resistance, Mobile genetic elements, Gene mapping, PFGE
Issue Date:Oct-2006
Publisher:Oxford University Press
Citation:Journal of Antimicrobial Chemotherapy 58(6): 1124-1132 (2006)
Abstract:[Objectives] To characterize class 1 and class 2 integrons which were simultaneously detected in non-typhoid Salmonella enterica strains of non-prevalent serovars, and to investigate their possible association with transposons and/or plasmids.
[Methods] Eight multidrug-resistant S. enterica strains belonging to serovars Virchow (4), Panama (2), Grumpensis (1) and Worthington (1), each containing a class 1 and a class 2 integron, were analysed. Nested PCR amplification was used to determine the gene-cassette configuration of the integrons. Overlapping PCR amplifications were applied in integron–transposon linkage experiments. Conjugation and hybridization experiments were used to localize integrons and transposons in the bacterial genome (plasmid and chromosome associated).
[Results] One of two different class 1 integrons (with variable regions of 1000 bp/aadA1 and 2300 bp/sat-smr-aadA1) inserted into Tn21-like transposons, were found to coexist with the class 2 integron (2300 bp/dfrA1-sat1-aadA1) of Tn7 in the analysed strains. Class 1 integrons were always found in large conjugative plasmids whereas apparently intact or defective copies of the Tn7 integron could be located on the same plasmid and/or the bacterial chromosome.
[Conclusions] This report describes different associations between mobile genetic elements that play a crucial role in the capture and spread of antimicrobial drug resistance. As far as we are aware, this is the first description of class 2 integrons in serovars Panama, Grumpensis and Worthington.
Publisher version (URL):http://dx.doi.org/10.1093/jac/dkl400
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