Increased resistance of Helicobacter pylori to clarithromycin and metronidazole has resulted in recommendation to substitute fluoroquinolones for eradication therapy. The aims of the study were to determine the prevalence and changes in primary levofloxacin resistance related to H. pylori gyrA sequences. The study utilized H. pylori strains isolated from patients undergoing gastroscopy in Bogot...

OBJECTIVES Although the prevalence of fluoroquinolone resistance among methicillin-resistant Staphylococcus aureus (MRSA) is known to be higher than in methicillin-susceptible S. aureus (MSSA), the reasons have never been identified. METHODS We randomly selected 115 isolates of S. aureus collected from 10 different hospitals in Korea between June 2009 and May 2011. To investigate the differen...

Nalidixic acid, enoxacin, and other antibacterial 4-quinolones inhibit DNA gyrase activity by interrupting DNA breakage and reunion by A subunits of the A2B2 gyrase complex. Despite their clinical importance, the mode of quinolone action and mechanisms of resistance are poorly understood at the molecular level. Using a DNA fragment enrichment procedure, we isolated the gyrA gene from a uropatho...

Twenty P. aeruginosa isolates were collected from six cystic fibrosis (CF) patients, aged 27 to 33, in 1994 (9 isolates) and 1997 (11 isolates) at the CF Center, Copenhagen, Denmark, and were typed by pulse-field gel electrophoresis (PFGE) or ribotyping. Five of the patients had isolates with the same PFGE or ribotyping patterns in 1997 as in 1994, and ciprofloxacin had a two- to fourfold highe...

We determined the prevalence of fluoroquinolone resistance among the isolates of Mycobacterium tuberculosis from 605 pulmonary tuberculosis patients in Shanghai, China. Mutations in gyrA were found in 81.5% of phenotypically fluoroquinolone-resistant isolates and were used as a molecular marker of fluoroquinolone resistance. gyrA mutations were detected in 1.9% of strains pan-susceptible to fir...

The accuracy of genotypic resistance to levofloxacin (gyrA mutations) and its agreement with treatment outcomes after levofloxacin-based therapy have not been reported. We aimed to assess the correlation. Helicobacter pylori strains isolated from patients who received levofloxacin-based and clarithromycin-based triple therapies in a previous randomized trial were analyzed for point mutations in...

Mechanisms of antibiotic resistance were examined in nalidixic acid-resistant Salmonella enterica serovar Enteritidis field isolates displaying decreased susceptibility to ciprofloxacin and in in vitro-derived ciprofloxacin-resistant mutants (104-cip and 5408-cip). All field isolates harbored a single gyrA mutation (D87Y). Deletion of acrB and complementation with wild-type gyrA increased quino...

We have analyzed by gene amplification and sequencing mutations in the quinolone resistance-determining regions of the gyrA, gyrB, and parC genes of fluoroquinolone-resistant Streptococcus pneumoniae mutants obtained during therapy or in vitro. Mutations leading to substitutions in ParC were detected in the two mutants obtained in vivo, BM4203-R (substitution of a histidine for an aspartate at ...

MICs of DU-6859a, a novel fluoroquinolone, for 18 Klebsiella pneumoniae isolates and 21 Enterobacter cloacae isolates with altered GyrA or altered GyrA and ParC ranged from < or =0.025 to 6.25 microg/ml and from 0.1 to 3.13 microg/ml, respectively. Based on the MICs at which 90% of the isolates were inhibited for these strains of K. pneumoniae and E. cloacae, DU-6859a exhibited 16- to 256-fold-...

gyrA mutations in quinolone-resistant pathogenic isolates of Staphylococcus spp. have been detected by the direct HinfI digestion of polymerase chain reaction products. Homology among gyrA genes allowed rapid examination of both coagulase-positive and -negative isolates. DNA sequence analysis revealed that ciprofloxacin resistance in Staphylococcus epidermidis is associated with a novel Ser-84-...