Mutations in gene araB producing an l-arabinose-negative phenotype cause either an increase (hyperinducible), decrease (polar), or have no effect at all on the inducible rate of expression of the l-arabinose operon. Fourteen araB gene mutants exhibiting such effects were shown to be the result of: nonsense, frameshift, or missense mutations. All missense mutants were hyperinducible, exhibiting ...

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...

Exposure to biocides may result in cross-resistance to other antimicrobials. Changes in biocide and antibiotic susceptibilities, metabolism, and fitness costs were studied here in biocide-selected Escherichia coli and Klebsiella pneumoniae mutants. E. coli and K. pneumoniae mutants with various degrees of triclosan susceptibility were obtained after exposure to triclosan (TRI), benzalkonium chl...

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...