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Title: Quorum-sensing regulator sdiA and marA overexpression is involved in in vitro-selected multidrug resistance of Escherichia coli
Authors: Tavío, María M. 
Aquili, Virginia D.
Poveda, José B. 
Antunes, Nuno T.
Sánchez-Céspedes, Javier
Vila, Jordi
Keywords: Multiple Antibiotic-Resistance
Organic-Solvent Tolerance
Beta-Lactam Antibiotics
Enterica Serovar Typhimurium
Penicillin-Binding Proteins, et al
Issue Date: 2010
Publisher: 0305-7453
Journal: Journal of Antimicrobial Chemotherapy 
Abstract: The role of sdiA in the acquisition of low-level multidrug resistance (MDR) was analysed and compared with that of marA and soxS in two Escherichia coli clinical isolates and two in vitro-selected mutants.The mutants were developed by growth in lomefloxacin and ceftazidime. The sdiA, marA, soxS, ftsI, tolC and acrB gene transcript levels were determined by RT-PCR. Analyses of 2,4-dinitrophenol susceptibility, the effect of an active efflux inhibitor on antibiotic and mitomycin C susceptibility, beta-lactamase hydrolytic activity, outer and inner membrane proteins and acrR gene sequencing were also performed.Both mutants showed elevated marA and sdiA gene transcript levels, which were associated with increased susceptibility to 2,4-dinitrophenol; soxS overexpression was only seen in the mutant selected with ceftazidime. The two mutants showed MDR phenotypes in which ceftazidime, cefpirome and aztreonam MICs increased 4- to 128-fold, in addition to decreased susceptibility to quinolones, chloramphenicol and mitomycin C. The highest ceftazidime MIC in one of the mutants coincided with a frameshift mutation in acrR and the highest transcript level of ftsI (penicillin-binding protein 3), but not with a higher beta-lactamase activity. Likewise, active efflux associated with increased levels of acrB and tolC and decreased OmpF expression contributed to low-level MDR in both mutants.marA and sdiA overexpression was a common feature of multidrug-resistant mutants selected by growth in lomefloxacin and ceftazidime. To our knowledge, this report is the first to describe in vitro selection with a fluoroquinolone or ceftazidime triggering sdiA overexpression in E. coli isolates.
ISSN: 0305-7453
DOI: 10.1093/jac/dkq112
Source: Journal of Antimicrobial Chemotherapy[ISSN 0305-7453],v. 65 (dkq112), p. 1178-1186
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