[Animats]

An antibiotic is something that kills something you don't like while not killing things you do like. The survival strategy for hostile bacteria is to evolve towards not having vulnerabilities to things which have that antibiotic property. A century of antibiotics has pushed evolution in that direction. Antibiotics thus get harder to find. There may be a fundamental limit here.

The golden age of simple, broad-spectrum antibiotics is behind us.

[Salgat]

On the plus side, this forces bacteria to compromise in other ways in order to incorporate antibiotic resistance.