For many years, DNA gyrase was thought to be responsible both for unlinking replicated daughter chromosomes and for controlling negative superhelical tension in bacterial DNA. However, in 1990 a homolog of gyrase, topoisomerase IV, that had a potent decatenating activity was discovered. It is now clear that topoisomerase IV, rather than gyrase, is responsible for decatenation of interlinked chr...

INTRODUCTION Rapid dissemination of plasmid-mediated quinolone resistance (PMQR) has been reported in clinical isolates. METHODOLOGY A total of 149 clinical isolates of Enterobacteriaceae were collected in Beijing and screened for PMQR genes using polymerase chain reaction (PCR). Real-time quantitative PCR was used to study the expression of qnrS. RESULTS The rates of qnr and aac(6')-Ib-cr ...

Rifamycins have proven efficacy in the treatment of persistent bacterial infections. However, the frequency with which bacteria develop resistance to rifamycin agents restricts their clinical use to antibiotic combination regimens. In a program directed toward the synthesis of rifamycins with a lower propensity to elicit resistance development, a series of compounds were prepared that covalentl...

OBJECTIVES To determine the frequency of selecting mutants resistant to ozenoxacin, a des-fluoro-(6)-quinolone active against pathogens involved in skin and skin structure infections, compared with levofloxacin and ciprofloxacin in quinolone-susceptible and -resistant Gram-positive cocci. METHODS Forty-nine quinolone-susceptible and -resistant Gram-positive cocci strains with different profil...

BACKGROUND Emergence of quinolone-resistant Escherichia coli (QREC) is an increasing clinical challenge mostly originating in fecal microbiota. The dynamics of the emergence of QREC in feces from individuals exposed to ciprofloxacin is unknown. METHODS A total of 48 healthy volunteers received oral ciprofloxacin for 14 days. Fecal specimens were collected on days 0, 8, 14, and 42. Subpopulati...

OBJECTIVES Nalidixic acid-resistant Salmonella enterica serovars Kentucky (n = 5) and Virchow (n = 6) cultured from individuals were investigated for the presence of plasmid-mediated quinolone resistance (PMQR) determinants. METHODS PMQR markers and mutations within the quinolone resistance-determining regions of the target genes were investigated by PCR followed by DNA sequencing. Conjugatio...

Although plasmid-mediated quinolone resistance (PMQR) was thought not to exist before its discovery in 1998, the past decade has seen an explosion of research characterizing this phenomenon. The best-described form of PMQR is determined by the qnr group of genes. These genes, likely originating in aquatic organisms, code for pentapeptide repeat proteins. These proteins reduce susceptibility to ...