Characterization of In3Mor, a new integron carrying VIM-1 metallo-beta-lactamase and sat1 gene, from Morganella morganii

Abstract

Objectives: A carbapenem-resistant Morganella morganii clinical isolate that was phenotypically metallo-beta-lactamase (MBL)-positive was recovered from a Greek patient. The aim of the study was to analyse the structure of the integron containing the MBL gene. Methods: MICs were determined by the broth microdilution method. PCR assays and nucleotide sequencing were used for identification of bla, gene types and mapping of the integron carrying the MBL gene. The location of the MBL allele was investigated by mating experiments and plasmid analysis as well as by Southern blotting of the plasmid extract and gene-specific hybridization with a bla(VIM-1) probe. Results: The strain contained In3Mor, a novel class 1 integron carrying a carbapenemase gene (bla(VIM-1)) associated with a trimethoprim (dfrA1), a streptothricin (sat1) and two aminoglycoside resistance genes (aacA7 and aadAl). Conjugation experiments failed to detect a transferable MBL determinant and plasmid DNA was not visualized. The chromosomal location of bla(VIM-1) was confirmed after hybridization of the chromosomal band with the bla(VIM-1) probe. Conclusions: Production of a VIM-type MBL in a M. morganii clinical isolate is documented in this study for the first time. Also, the dfrA1-sat1-aadA1 array which is typically described in the variable region of class 2 integrons consistent with that on Tn 7 transposons, is originally detected herein in a class 1 integron.