Multiple mutations conferring ciprofloxacin resistance in Staphylococcus aureus demonstrate long-term stability in an antibiotic-free environment.

Two unrelated strains of Staphylococcus aureus, one with a single mutation in grlA, the other with multiple mutations in gyrA, gyrB, grlA, grlB, norA and the norA promoter region, encoding low-level and high-level ciprofloxacin resistance, respectively, were studied. The characterized mutations in these genes were conserved when both strains were passaged for at least 500 generations in an antibiotic-free environment. New, rapidly stabilized mutations and higher MICs were detected for strains passaged in sub-MIC ciprofloxacin concentrations.

PDZ-GEF1, a guanine nucleotide exchange factor specific for Rap1 and Rap2.

The small GTPase Rap1 has been implicated in a variety of cellular processes including the control of cell morphology, proliferation, and differentiation. Stimulation of a large variety of cell surface receptors results in the rapid activation of Rap1, i.e.