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. 2001 May;45(5):1550-2.
doi: 10.1128/AAC.45.5.1550-1552.2001.

Absence of mutations in marRAB or soxRS in acrB-overexpressing fluoroquinolone-resistant clinical and veterinary isolates of Escherichia coli

M A Webber  1 , L J Piddock
Affiliations

Absence of mutations in marRAB or soxRS in acrB-overexpressing fluoroquinolone-resistant clinical and veterinary isolates of Escherichia coli

M A Webber et al. Antimicrob Agents Chemother. 2001 May.

Abstract

The amount of acrB, marA, and soxS mRNA was determined in 36 fluoroquinolone-resistant E. coli from humans and animals, 27 of which displayed a multiple-resistance phenotype. acrB mRNA was elevated in 11 of 36 strains. A mutation at codon 45 (Arg-->Cys) in acrR was found in 6 of these 11 strains. Ten of the 36 isolates appeared to overexpress soxS, and five appeared to overexpress marA. A number of mutations were found in the marR and soxR repressor genes, correlating with greater amounts of marA and soxS mRNA, respectively.

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Figures

FIG. 1
FIG. 1
Overproduction of acrB. The strains that overproduced acrB mRNA (I87, I94, I238, I241, I244, I245, I254 and I279) gave brighter bands than AG102 (which constitutively overexpresses marA mRNA), indicating that they produced more acrB than a Mar mutant strain.
FIG. 2
FIG. 2
Overproduction of soxS. The strains that overproduced soxS mRNA gave intensities of the transcript similar to that of the positive control strain, JTG1078 (Sox +ve). The soxS transcript was barely detectable in wild-type strains (e.g., I113).
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