DNA gyrase is a target of quinolone antibacterial agents, but the molecular details of the quinolone-gyrase interaction are not clear. Quinolone resistance mutations frequently occur at residues Ser(83) and Asp(87) of the gyrase A subunit, suggesting that these residues are involved in drug binding. Single and double alanine substitutions were created at these positions (Ala(83), Ala(87), and A...

Resistance of various pathogens toward quinolones has emerged as a serious threat to combat infections. Analysis of plethora of genes and resistance mechanisms associated with quinolone resistance reveals chromosome-borne and transferable determinants. qnr genes have been found to be responsible for transferable quinolone resistance. In the present work, a new allele qnrVC5 earlier reported in ...

OBJECTIVES To investigate the potential relationship between quinolone resistance and biofilm production in a collection of Salmonella enterica clinical isolates and in S. enterica serovar Typhimurium serial mutants with increasing resistance to ciprofloxacin. METHODS Nalidixic acid susceptibility and biofilm formation were assessed in a collection of 122 S. enterica clinical isolates. An in ...

The growing frequency of antibiotic resistances is now a universal problem. Increasing resistance to new generations of β-lactam and quinolone antibiotics in multidrug-resistant Enterobacteriaceae isolates is considered an emergency health issue worldwide. The aim of this study was to evaluate plasmid-mediated quinolone resistance genes in ESBL-producing Escherichia coli isolated from urinary t...

Fluoroquinolone resistance is emerging in gram-negative pathogens worldwide. The traditional understanding that quinolone resistance is acquired only through mutation and transmitted only vertically does not entirely account for the relative ease with which resistance develops in exquisitely susceptible organisms, or for the very strong association between resistance to quinolones and to other ...

Quinolone susceptibility was analyzed in 17 clinical isolates of Corynebacterium striatum and 9 strains of Corynebacterium amycolatum by the E-test method in Mueller-Hinton agar plates. The C. striatum ATCC 6940 strain was used as a control strain. The amplified quinolone resistance determining regions of the gyrA genes of C. amycolatum and C. striatum were characterized. Four in vitro quinolon...

DNA gyrase is a target of quinolone antibacterial agents, but the molecular details of the quinolone-gyrase interaction are not clear. Quinolone resistance mutations frequently occur at residues Ser and Asp of the gyrase A subunit, suggesting that these residues are involved in drug binding. Single and double alanine substitutions were created at these positions (Ala, Ala, and Ala Ala), and the...

We used an assay to measure quinolone sensitivity as a shift in the position of the cleavage-religation equilibrium. This assay was found to be useful in identifying the primary target of a quinolone drug and assessing the effect of quinolone resistance-conferring mutations.

Fourteen out of 16 carbapenem-resistant quinolone-susceptible Enterobacter cloacae isolates were found to carry qnrB2 and bla(KPC-2) genes encoded on the same plasmid. One isolate also carried the aac(6')-Ib-cr gene. Coexistence of quinolone resistance determinants and bla(KPC-2) on the same plasmid in quinolone-susceptible E. cloacae isolates may have important clinical implications.

Sir, Fluoroquinolones are broad-spectrum antibacterial agents commonly used in clinical practice. When quinolones became widely used, bacterial resistance to them emerged rapidly and, over the past three decades, resistance has continued to increase. In Gram-negative bacteria, quinolone resistance is due primarily to mutations in chromosomal genes encoding quinolone targets DNA gyrase and topoi...