Quinolone uptake by bacteria and bacterial killing.

A review of the mechanisms of the action of 4-quinolones is presented, concentrating on the process of uptake and bacterial killing. 4-Quinolones appear to cross the gram-negative outer membrane via diffusion through outer-membrane proteins, although disruption of the normal outer-membrane barrier by 4-quinolones may facilitate diffusion via a non-porin-mediated route. Accumulation in the cytoplasm may involve influx and efflux mechanisms. The inhibition of DNA synthesis by 4-quinolones has been investigated in Escherichia coli AB1157 and found to correlate with antibacterial activity (as measured by the minimal inhibitory concentration). 4-Quinolones have other pleotropic effects on bacterial cells, such as induction of the SOS (DNA repair) response, filamentation, and direct effects on membranes.