Mode of Action

Quinolone antibacterials act by inhibition of bacterial topoisomerase II (DNA gyrase) and topoisomerase IV in Gram-positive species, thus inhibiting tertiary negative supercoiling of bacterial DNA [4-8]. This effect, probably associated with binding of quinolones to a DNA gyrase complex [9], is rapidly bactericidal [8]. The minimum bactericidal concentration is usually only two- to fourfold the MIC, and a prolonged post-antibiotic effect is produced at concentrations exceeding the MIC.

Fluoroquinolones only rarely demonstrate synergy or antagonism with other agents [10]. Combination therapy can be expected to enhance therapy only by the individual and additive activity of the compounds used, except possibly with imipenem in some P. aeruginosa infections and with rifampicin in staphylococcal disease where improved clinical outcomes may result.

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