Chapter 7 : Fluoroquinolones, Sulfa Drugs, and Antituberculosis Drugs

Abstract:

This chapter takes a look at antibiotics that have targets other than the bacterial cell wall and bacterial ribosomes. Ciprofloxacin and other fluoroquinolones are among the most frequently prescribed antibiotics today, due in no small part to aggressive marketing by drug salesmen. These drugs are a relatively new entry into the antibiotic armamentarium and are currently regarded as one of the front-line antibiotics to defend patients against infections caused by bacteria that are resistant to other antibiotics. Also, fluoroquinolones are now being used to treat tuberculosis (TB), a very dangerous disease, especially in cases where the bacterium that causes tuberculosis has become resistant to the traditional antituberculosis (anti-TB) drugs. Fluoroquinolones are administered to chickens in their water to prevent infections caused by Escherichia coli. DNA gyrase is an enzyme that is involved in returning newly replicated DNA to its supercoiled form. Fluoroquinolones act by binding tightly to DNA gyrase. In the process, they distort its structure sufficiently to prevent the gyrase from doing its job. As was the case of the fluoroquinolones, resistance to sulfa drugs or trimethoprim develops easily if these antibiotics are taken separately. The protein target of the antibiotic mutates so that it still works but no longer binds the antibiotic. The acute symptoms of TB are caused by rapidly dividing Mycobacterium tuberculosis cells.