Selective toxicity antibacterial agents

Although the antibacterial spectmm is similar for many of the sulfas, chemical modifications of the parent molecule have produced compounds with a variety of absorption, metaboHsm, tissue distribution, and excretion characteristics. Administration is typically oral or by injection. When absorbed, they tend to distribute widely in the body, be metabolized by the Hver, and excreted in the urine. Toxic reactions or untoward side effects have been characterized as blood dyscrasias crystal deposition in the kidneys, especially with insufficient urinary output and allergic sensitization. Selection of organisms resistant to the sulfonamides has been observed, but has not been correlated with cross-resistance to other antibiotic families (see Antibacterial AGENTS, synthetic-sulfonamides). 

Antibacterial drugs are examples of chemicals that are selectively toxic to specific cells or organisms such as bacteria or fungi. These agents are useful to man because they are toxic to bacteria and have been designed to be that way. 

On this basis, the proteins of riboflavin biosynthesis may be relevant targets for the development of novel antibacterial agents, notably with selectivity for mycobacteria, Enterobacteriaceae, or pathogenic yeasts. Since these proteins are absent in human and animal hosts, the risks of off-target toxicity should be comparatively low. 

Although the antibacterial and antifungal activities of bialaphos and phosphinothricin were not found to be usehil, the two agents were later used as biodegradeable, relatively nonselective, postemergent herbicides. Glutamine synthetase inhibition is toxic to plants because the enzyme is key to ammonia assimilation. There is some selectivity for individual plant species as shown by the LD for bialaphos ranging from 0.125 to 8.5 kg/ha (301—303). 

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