(Genome) size matters.

The quotation above has led to the commonly held view that all bacteria will eventually become resistant to any antibiotic given enough time and exposure. However not all bacteria develop resistance to antibiotics at the same rate (and perhaps some species of bacteria may never develop resistance to certain antibiotics). And some bacteria that have been labeled “resistant” are not, in any clinically meaningful way, actually resistant (i.e. result in a therapeutic failure). Indeed, all antibiotics, even within the same chemical class, are not created equal (in terms of their propensity to select for resistant strains).