Polymyxin

So instead of breaking down the cell wall, like the beta-lactam antibiotics and vancomycin that I talked about in the last episode, these drugs go straight for that plasma membrane.

And the first example is polymyxin B, which you've probably seen before in topical ointments like Neosporin.

Polymyxins acts almost like a detergent, disrupting the bacterial cell membrane and causing the cell to leak and die, so they're bactericidal.

Polymyxins are especially useful against Gram-negative bacteria, including Pseudomonas species, but they can be toxic to the kidneys, which is why they're limited to topical use or are very controlled in other forms.

Another drug in this category is daptomycin, which is more active against Gram-positive bacteria and is used for more serious infections.

This is a good time to point out that not all drugs work equally well on all bacteria, and a lot of that comes down to differences in cell envelope structure.