Leading articles Mechanisms

of resistance to qninolones and clinical perspectives The primary target for the action of the quinolones is the A sub-units of DNA gyrase, although the actual mechanism of bactericidal action may involve a cascade of cellular events (Piddock & Wise, 1987a). Mutants of Escheri-chia coli with high-level resistance to nalidixic acid can easily be selected in the laboratory at a frequency of approximately 10"7, and have been shown to possess an altered DNA gyrase (Gellert et al., 1976). DNA gyrase has been shown to exist in all bacterial species examined to date (Gellert, 1981). In several species, including Pseudomonas aervginosa, Haemo