Quinolone resistance in Escherichia coli

Escherichia coli is an important pathogen of animals and humans that causes great financial cost in food production by causing disease in food animals . The quinolones are a class of synthetic antimicrobial agents with excelle nt activity against Escherichia coli and other Gram-negative bacteria used in human and veterinary medicine. Different quinolones are used to treat va rious conditions in animals in different parts of the world. All members of this class of drug have the same mode of action: inhibition of topoisomera se enzymes, DNA Gyrase and Topoisomerase IV. Escherichia coli can become re sistant to quinolones by altering the target enzymes, reducing permeability of the cell to inhibit their entry, or by actively pumping the drug out of the cell. All these resistance mechanisms can play a role in high-level fl uoroquinolone resistance, however target site mutations appear to be most i mportant. As all quinolones act in the same way resistance to one member of the class will also confer decreased susceptibility to all members of the family. Quinolone resistant Escherichia coli in animals have increased in n umbers after quinolone introduction in a number of different case studies. The resistance mechanisms in these isolates are the same as those in resist ant strains found in humans. Care needs to be taken to ensure that quinolon es are used sparingly and appropriately as highly resistant strains of Esch erichia coli can be selected and may pass into the food chain. As these dru gs are of major therapeutic importance in human medicine, this is a public health concern. More information as to the numbers of quinolone resistant E scherichia coli and the relationship between resistance and quinolone use i s needed to allow us to make better informed decisions about when and when not to use quinolones in the treatment of animals.