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J Infect Dis. 1993 Aug;168(2):484-8.

A multidrug resistance regulatory chromosomal locus is widespread among enteric bacteria.

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Center for Adaptation Genetics and Drug Resistance, Tufts University School of Medicine, Boston, MA 02111.


Constitutive expression of the mar operon (marRAB) in Escherichia coli produces a multiple antibiotic resistance phenotype mediated by the expression of multiple genetic loci in response to regulatory proteins in the operon. A mar-specific DNA probe was used to search for the operon in bacterial strains representing 53 species and 27 genera. Among these, 6 other Enterobacteriaceae, Salmonella, Shigella, Klebsiella, Citrobacter, Hafnia, and Enterobacter species, contained DNA sequences that hybridized to the probe under high-stringency conditions. By use of a selection protocol developed to obtain multiple antibiotic resistant mutants of E. coli, multiply resistant mutants that showed increased expression of mar-specific RNA were obtained from Enterobacter agglomerans and Salmonella species.

[Indexed for MEDLINE]

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