Chapter 25 : Antibacterial Agents That Cause Damage to DNA

Abstract:

The 5-nitrofurans are a class of totally synthetic antibacterial agents characterized by being derivatives of 5-nitrofuran and by containing the azomethine group (--CH=N--). Nitrofurantoin is still in use in humans because of its broad spectrum of activity, which covers gram-positive and gram-negative bacteria (except Pseudomonas aeruginosa and some Klebsiella and Proteus strains), its relatively low toxicity, and the infrequent development of resistance. Since the introduction of nitrofurantoin for use in urinary tract infections (UTIs), essentially no resistance has occurred, unlike other antibacterial agents. It was suggested that this is due to the ability of the 5-nitrofurans to affect multiple cytoplasmic targets such as inhibiting various enzymes within bacteria and that they may also damage bacterial DNA, leading to DNA strand breakage. Urinary antiseptics are antibacterial agents that concentrate in the urine but do not produce adequate levels in serum. Therefore, these antibacterial agents are useful only in the prevention or therapy of lower UTIs and not for treatment of severe pyelonephritis or associated systemic infections. Bacteria have no mitochondria; in bacteria, the mitochondrial functions are all carried out within the plasma membrane, where all the needed enzymes are anchored. This relatively poor protection of the enzyme system (compared with that in the host cell) could explain the selective toxicity of these 5-nitro aromatic antibacterial agents.