The contribution of regulatory genes to fluoroquinolone resistance was studied with clinical Escherichia coli strains bearing mutations in gyrA and parC and with different levels of fluoroquinolone resistance. Expression of marA and soxS was evaluated by Northern blot analysis of isolates that demonstrated increased organic solvent tolerance, a phenotype that has been linked to overexpression o...

Strains of the multidrug-resistant (MDR) Salmonella enterica serovar Typhimurium isolated in Japan were examined for high-level fluoroquinolone resistance. Since the first isolation in 2000 (described in reference 13), we have identified 12 human and 5 nonhuman isolates with high-level fluoroquinolone-resistance (ciprofloxacin MIC of 24 microg/ml or more). Most of these isolates shared some fea...

Fluoroquinolone-resistant Campylobacter jejuni has been observed worldwide and is now being seen in the United States. Among patients in our health-care system in Pennsylvania, fluoroquinolone-resistant C. jejuni were not observed from 1982 to 1992; however, resistance increased to 40.5% in 2001. Resistance to erythromycin remains at a low level (<5%).

Fluoroquinolone resistance in Staphylococcus aureus results from amino acid substitutions at particular locations in the DNA gyrase A and B subunits as well as in the topoisomerase IV A subunit and from NorA-mediated efflux. More than one resistance mechanism may be present in a single strain. Fluoroquinolone-resistant derivatives of SA-1199, a methicillin-susceptible S. aureus strain, were sel...

Ceftazidime-avibactam and comparator antibiotics were tested by the broth microdilution method against 200 Enterobacteriaceae and 25 Pseudomonas aeruginosa strains resistant to fluoroquinolones (including strains with the extended-spectrum β-lactamase [ESBL] phenotype and ceftazidime-resistant strains) collected from our institution. The MICs and mechanisms of resistance to fluoroquinolone were...

In many countries, fluoroquinolones are among the most commonly used antibacterial drugs. Concerns about bacterial resistance to these and other frequently used drugs have been raised by the medical and scientific communities. While fluoroquinolone resistance has not yet developed among many bacteria, emergence of resistance in Escherichia coli would be a problem as multiple resistances to othe...

BACKGROUND & OBJECTIVES There is a worldwide emergence of fluoroquinolone resistance in Shigella species. To understand the molecular mechanisms associated with fluoroquinolone resistance, naturally occurring fluoroquinolone-resistant strains and laboratory-induced spontaneous mutants of Shigella spp. were used and the relative contributions of acrAB-tolC efflux pumps, gyrase and topoisomerase ...

Moxifloxacin-resistant mutants of Brucella melitensis 16M [moxifloxacin minimum inhibitory concentration (MIC)=1mg/L] were selected in order to characterise fluoroquinolone resistance mechanisms in this species. Eight independent mutants were obtained, with moxifloxacin MICs of 16-32mg/L. The mutants displayed variable cross-resistance levels to other fluoroquinolone compounds, but no increased...

AIM To evaluate bacterial resistance to clarithromycin and fluoroquinolones in Brazil using molecular methods. METHODS The primary antibiotic resistance rates of Helicobacter pylori (H. pylori) were determined from November 2012 to March 2015 in the Southern, South-Eastern, Northern, North-Eastern, and Central-Western regions of Brazil. Four hundred ninety H. pylori patients [66% female, mean...

This analysis of nearly 10,000 hospital-associated urinary tract infection (UTI) episodes due to Escherichia coli showed that fluoroquinolone and third-generation-cephalosporin resistance rates were 34.5% and 8.6%, respectively; the rate of concurrent resistance to both agents was 7.3%. Fluoroquinolone resistance rates exceeded 25% regardless of geographic location or hospital characteristics. ...