OBJECTIVES Besifloxacin is a new fluoroquinolone in development for ocular use. We investigated its mode of action and resistance in two major ocular pathogens, Streptococcus pneumoniae and Staphylococcus aureus, and in the reference species Escherichia coli. METHODS Primary and secondary targets of besifloxacin were evaluated by: (i) mutant selection experiments; (ii) MIC testing of defined ...

We examined the potential for the development of fluoroquinolone resistance in Neisseria meningitidis by cultivating two clinical isolates of meningococci in the presence of concentrations of ciprofloxacin at and about the predetermined MIC. The quinolone resistance determining regions (QRDRs) of gyrA and parC of 50 stable quinolone-resistant mutants derived in vitro were sequenced and compared...

We investigated the contribution of quinolone resistance-determining region (QRDR) mutations to fluoroquinolone (enrofloxacin, orbifloxacin and danofloxacin) susceptibility in 58 Mycoplasma bovis isolates from dairy cattle in Japan. Fluoroquinolone non-resistant isolates (fluoroquinolone-MICs≤2 μg/ml) possessed no QRDR mutations (19 isolates) or Ser83Leu in GyrA (32 isolates). Fluoroquinolone-r...

In a recently published article, Fukushima et al. (3) described a novel PCR-melting curve analysis (PCR-MCA) method for rapid screening of the most prevalent point mutations related to fluoroquinolone resistance in Streptococcus pneumoniae. In their study, they included 22 levofloxacin (LVX)-resistant strains and 50 LVX-susceptible isolates. None of the isolates in that study were shown to harb...

OBJECTIVES To compare the in vitro activity of moxifloxacin and ciprofloxacin against 226 nosocomial isolates of Acinetobacter baumannii from 44 hospitals in the UK. METHODS MICs of ciprofloxacin and moxifloxacin were determined by Etest. PCR analysis was used to detect chromosomal mutations in the gyrA and parC genes. Isolates resistant to ciprofloxacin and susceptible to moxifloxacin were e...

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.

The genes encoding the DNA gyrase A and B subunits of Bacteroides fragilis were cloned and sequenced. The gyrA and gyrB genes code for proteins of 845 and 653 amino acids, respectively. These proteins were expressed in Escherichia coli, and the combination of GyrA and GyrB exhibited ATP-dependent supercoiling activity. To analyze the role of DNA gyrase in quinolone resistance of B. fragilis, we...

Mutations in loci other than genes for the target topoisomerases of fluoroquinolones, gyrA and parC, may play a role in the development of fluoroquinolone resistance in Escherichia coli. A series of mutants with increasing resistance to ofloxacin was obtained from an E. coli K-12 strain and five clinical isolates. First-step mutants acquired a gyrA mutation. Second-step mutants reproducibly acq...

The potential for selection in vitro of Legionella pneumophila mutants resistant to fluoroquinolones was investigated. Six distinct clinical isolates of L. pneumophila were subcultured in subinhibitory concentrations of ciprofloxacin, levofloxacin, clinafloxacin, trovafloxacin and moxifloxacin until MICs increased at least eight-fold. The numbers of serial passages required in microbroth diluti...

Antibiotic resistance of Salmonella species is well reported. Ciprofloxacin the frontline antibiotic for salmonellosis. The repeated exposure to ciprofloxacin leads resistant strains. After 20 cycles exposure, bacterial clones were evaluated. colony size mutants was small and had an extended lag phase compared parent strain. whole genome sequencing showed 40,513 mutations across genome. Small p...