Characterization of the IncA/C plasmid pCC416 encoding VIM-4 and CMY-4 beta-lactamases.
OBJECTIVE
To characterize the antibiotic resistance regions of pCC416, a VIM-4- and CMY-4-encoding plasmid from clinical enterobacteria, and to elucidate its relation with the CMY-encoding plasmids widely diffused in Salmonella.


METHODS
The enterobacterial multiresistant plasmid pCC416 was derived from an Escherichia coli transconjugant and characterized. Conventional and long-range PCR assays were performed using primers specific for VIM-4- and CMY-4-encoding segments of pCC416. Amplicons were characterized by sequencing. blaVIM-4, blaCMY-4 and IntI1-specific probes were prepared from PCR products and used for the identification of various pCC416 clones. VIM- and CMY-positive BamHI and Sau3AI fragments of pCC416 were cloned into pACYC184 and their sequences were determined by gene walking.


RESULTS
The pCC416 plasmid contained two distinct resistant loci carrying beta-lactamase genes. The blaVIM-4 gene was part of an integron located in a complex, multidrug-resistant region of novel structure, interspersed with mobile elements or remnants thereof and being similar to various regions of other resistance plasmids. Nevertheless, a region in the 3' end of this structure resembled the respective region found in a CMY-2-encoding plasmid from Salmonella. The blaCMY-4 gene was identified within an 11.3 kb region also related to the CMY-2-encoding plasmids.


CONCLUSIONS
pCC416 probably evolved from an IncA/C2, CMY-encoding plasmid through acquisition of a VIM-encoding In4-type integron providing an example of accretion of resistance determinants in a single replicon.
Colinon
Céline
C
Dipartimento di Biologia Molecolare, Laboratorio di Fisiologia e Biotecnologia dei Microorganismi, Università di Siena, Siena, and Laboratorio di Microbiologia, Ospedale di Circolo, Varese, Italy.
Miriagou
Vivi
V
Carattoli
Alessandra
A
Luzzaro
Francesco
F
Rossolini
Gian Maria
GM
D003001:Cloning, Molecular; D004251:DNA Transposable Elements / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004755:Enterobacteriaceae / Q000201:enzymology / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001618:beta-Lactamases / Q000235:genetics*
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D001618:beta-Lactamases; C476341:beta-lactamase CMY-4, Salmonella enterica; C477893:beta-lactamase bla(VIM-4), Pseudomonas aeruginosa