Inhibition of cell metabolism.Antibacterial agents which inhibit cell metabolism are called antimetabolites. Thesecompounds inhibit the metabolism of a microorganism, but not the metabolism ofthe host. They do this by inhibiting an enzyme-catalysed reaction which is presentin the bacterial cell, but not in animal cells. The best known examples of antibacterialagents acting in this way are the sulfonamides.Inhibition of bacterial cell wall synthesis.Inhibition of cell wall synthesis leads to bacterial cell lysis (bursting) and death.Agents operating in this way include penicillins and cephalosporins. Since animalcells do not have a cell wall, they are unaffected by such agents.Interactions with the plasma membrane.Some antibacterial agents interact with the plasma membrane of bacterial cells toaffect membrane permeability. This has fatal results for the cell. Polymyxins andtyrothricin operate in this way.Antibacterial agents which act against cell metabolism (antimetabolites) 159• Disruption of protein synthesis.Disruption of protein synthesis means that essential enzymes required for the cell'ssurvival can no longer be made. Agents which disrupt protein synthesis include therifamycins, aminoglycosides, tetracyclines, and chloramphenicol.• Inhibition of nucleic acid transcription and replication.Inhibition of nucleic acid function prevents cell division and/or the synthesis ofessential enzymes. Agents acting in this way include nalidixic acid and proflavin.
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