<p><strong>Neomycin</strong>, an aminoglyoside with antimicrobial spectrum similar to gentamicin, binds to the 30S subunits of the bacterial ribosome, inhibiting protein synthesis and thereby disrupting DNA synthesis. It is active against many gram-negative aerobes and against some strains of staphylococci.<br />
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<strong>Bacitracin</strong>, on the other hand, inhibits bacterial cell wall synthesis and is active against many gram-positive bacteria (e.g. staphylococci, streptococci, corynebacteria and Clostridia) and some gram-negative species (e.g. Neisseria and Haemophilus influenzae). They are often found in combinations in topical preparations as broad spectrum antibacterial agents.<br />
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<strong>Polymyxin B</strong>&nbsp;disrupts the bacterial cytoplasmic membrane of mostly gm-ve organisms allowing leakage of intracellular constituents by binding to membrane phospholipids.</p>