DNA gyrase and to poi some rase IV. DNA gyrase is a tetrameric enzyme which catalyses negative DNA supercoiling and consists of two subunitsA and two subunitsB.Top is some rase IV isalsoa tetrameric enzyme, consisting of two subunitsC and two subunitsE, and is involved in the separation of daughter chromosomes during DNA replication (5). Resistance caused by point mutations arises spontaneously and results in the substitution of amino acids within the gyrase and to point is some rase genes (gyrA, gyrB, parC and parE), often in combination with reduced membrane porin expression and over‐ expression of the effluxpump system(5). Studies of strains isolated from clinical sources demonstrate that most mutations that induce quinolone resistance are found in gyrase subunitA(gyrA)(10).These are mainly found in a region called the quinolone resistance