Resistance of Helicobacter pylori to the standard therapeutic antimicrobials (clarithromycin, metronidazole, amoxicillin [AMX], and tetracycline) (9) has been demonstrated; therefore, there is an urgent need to introduce other treatment options. Fluoroquinolones, such as levofloxacin (LVX) and gatifloxacin (GAT), have been evaluated as an alternative to standard antibiotics against H. pylori. A...

Campylobacter jejuni, a major foodborne human pathogen, has become increasingly resistant to fluoroquinolone (FQ) antimicrobials. By using clonally related isolates and genetically defined mutants, we determined the fitness of FQ-resistant Campylobacter in chicken (a natural host and a major reservoir for C. jejuni) in the absence of antibiotic selection pressure. When monoinoculated into the h...

Fluoroquinolones are antibacterial drugs that inhibit DNA Gyrase and Topoisomerase IV. These essential enzymes facilitate chromosome replication and RNA transcription by regulating chromosome supercoiling. High-level resistance to fluoroquinolones in E. coli requires the accumulation of multiple mutations, including those that alter target genes and genes regulating drug efflux. Previous studie...

The low prevalence of ciprofloxacin-resistant (Cp r) Streptococcus pneumoniae isolates carrying recombinant topoisomerase IV genes could be attributed to a fitness cost imposed by the horizontal transfer, which often implies the acquisition of larger-than-normal parE-parC intergenic regions. A study of the transcription of these genes and of the fitness cost for 24 isogenic Cp r strains was per...

OBJECTIVES To investigate the prevalence of fluoroquinolone resistance in Streptococcus pyogenes and its in vitro selection by ciprofloxacin and the respiratory fluoroquinolones, levofloxacin and moxifloxacin. METHODS S. pyogenes (n = 5851) recovered from pharyngitis and invasive infections during 2003-06 in Belgium were screened for fluoroquinolone non-susceptibility (ciprofloxacin MIC > or ...

Fluoroquinolone MICs are increased through the acquisition of chromosomal mutations in the genes encoding gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE), increased levels of the multidrug efflux pump AcrAB, and the plasmid-borne genes aac(6')-Ib-cr and the qnr variants in Escherichia coli. In the accompanying report, we found that ciprofloxacin, gatifloxacin, levofloxacin, and norf...