Dissociated resistance among fluoroquinolones

Dissociated resistance among cephalosporins.

When disks containing cefuroxime (CXM) or HR 756 (756) were placed next to cefoxitin (FOX) on plates inoculated with Enterobacter resistant to FOX, there was marked flattening of the zones of inhibition produced by CXM or 756, but colonies growing near the CXM or 756 disks were found to be fully susceptible to these drugs on retesting. In contrast, when a checkerboard titration with CXM or 756 ...

Does mutation rate drive resistance to fluoroquinolones?

High levels of resistance to fluoroquinolones among Clostridium difficile isolates in a Spanish hospital.

The appearance of Clostridium difficile NAP1/027 (the epidemic strain) has been blamed for an increase in the incidence and severity of C. difficile infection. Some authors consider quinolone resistance to be a good marker of the epidemic strain. We performed a prospective study to assess C. difficile infection at our institution in Madrid, Spain (Hospital General Universitario Gregorio Marañón...

Suppression of gyrase-mediated resistance by C7 aryl fluoroquinolones

Fluoroquinolones form drug-topoisomerase-DNA complexes that rapidly block transcription and replication. Crystallographic and biochemical studies show that quinolone binding involves a water/metal-ion bridge between the quinolone C3-C4 keto-acid and amino acids in helix-4 of the target proteins, GyrA (gyrase) and ParC (topoisomerase IV). A recent cross-linking study revealed a second drug-bindi...

Mechanisms of clinical resistance to fluoroquinolones in Staphylococcus aureus.

Mechanisms of Staphylococcus aureus resistance to fluoroquinolones were characterized. Subunit A and B proteins of DNA gyrase were partially purified from fluoroquinolone-susceptible strain SA113 and resistant isolate MS16405, which was 250- to 1,000-fold less susceptible to fluoroquinolones such as ciprofloxacin, norfloxacin, ofloxacin, temafloxacin, and sparfloxacin than SA113 was. The superc...