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 ...

DC-159a yielded MICs of or=4 microg/ml). Although the MICs for DC-159a against quinolone-susceptible pneumococci were a few dilutions higher than those of gemifloxacin, the MICs of these two compounds against 28 quinolone-resistant pneumococci were identical. ...

INTRODUCTION Plasmid-mediated quinolone resistance, which complicates treatment, has been increasingly identified in Escherichia coli isolates worldwide. The purpose of this study was to identify the plasmid-mediated qnrA and qnrB genes among the quinolone-resistant Escherichia coli isolated from urinary tract infections in Iran. METHODOLOGY A total of 140 Escherichia coli isolates were colle...

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...

Quinolone resistance normally arises by mutations in the chromosomal genes for type II topoisomerases and by changes in the expression of proteins that control the accumulation of quinolones inside bacteria. A novel mechanism of plasmid-mediated quinolone resistance was recently reported that involves DNA gyrase protection by a pentapeptide repeat family member called Qnr. This family includes ...

OBJECTIVES Pentapeptide repeat proteins (PRPs) QnrA, QnrB and QnrS confer reduced susceptibility to quinolones. This study presents an in vitro analysis of the genetic evolution of quinolone resistance mediated by changes in the coding sequences and promoter regions of qnrA1, qnrS1 and qnrB1 genes. METHODS A random mutagenesis technique was used to predict the evolutionary potential of these ...

BMS-284756, a novel des-fluoro(6)-quinolone, was used to select for in vitro mutants of Staphylococcus aureus ISP794. Step mutants were obtained, and the quinolone resistance-determining regions of four target genes, gyrA, gyrB, grlA, and grlB, were sequenced. The data suggest that DNA gyrase is the primary target for BMS-284756 in S. aureus.

When tested against 312 clinical isolates of rapidly growing mycobacteria, the quinolone pipemidic acid correctly separated Mycobacterium chelonae (M. chelonei) from Mycobacterium fortuitum biovar fortuitum but not from biovar peregrinum or the third biovar complex. The new 4-quinolone ciprofloxacin correctly separated all three biovars of M. fortuitum from M. chelonae and appears to provide a ...

We developed a novel rapid assay to detect the gyrA mutations that cause quinolone resistance in typhoid and paratyphoid fever Salmonella spp. using high-resolution melting (Idaho Technology, Salt Lake City, UT) analysis of polymerase chain reaction amplicons. The presence of gyrA mutations led to small but consistent changes in amplicon melting temperatures that allowed quinolone-resistant iso...

The uptakes of norfloxacin by quinolone-resistant and -susceptible strains of Serratia marcescens were almost the same and 50% inhibitory concentrations for DNA gyrase and the MICs of quinolones were correlated, suggesting that DNA gyrase alterations are the basis of quinolone resistance.