Beneath the cell wall, the cytoplasmic membrane essentially acts as a bag that contains the cytoplasm and controls the passage of chemicals into and out of the cell. Extensive damage to membranes' proteins or phospholipids allows the cellular contents to leak out and if not immediately repaired causes death (Manuselis and Mahon, 2007).
Polymyxin B, polymyxin E (colistin), amphotricin B, imidazoles, triazoles and polyenes exert their actions by altering the bacterial cell membranes. The inhibition of cell membrane function leads to escape of macromolecules from the cell resulting in cell damage or death (Chakraborty, 2009).
Polymyxin is effective against gram-negative bateria, particularly pseudomonas, but because it is toxic to human kidneys it is usually reserved for use against pathogens that are resistant to other antibacterial drugs (Bauman, 2009b).
Daptomycin is a new lipopeptide antibiotic that is rapidly bactericidal by binding to the cell membrane in a calcium dependent manner causing depolarization of bacterial membrane potential. This leads to intracellular potassium release. This agent has been approved for use in the treatment of Staphylococcus aureus blood stream infections and skin and soft tissue infections caused by gram-positive bacteria, particularly those organisms that are highly resistant to β-lactam agents and vancomycin (Brooks and Carroll, 2010).
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