"acquiring a plasmid or phage carrying an enzyme that inactives teixobactin. This particular mode of acquiring antibiotic resistance is quite common."
Right, which is why I said the bit about bacteria kicking out genes that they don't need. Bacteria will "eject" a plasmid within a generation or two if they no longer need the gene(s) in question. Replicating a big gob of easily-ejectable DNA is not something bacteria do unless there's a good reason to do it.
Basically, for plasmid resistance to propagate, you need to have constant exposure to the antibiotic in question, or the resistance gene needs to be stably integrated into the bacterial genome. The former doesn't happen until an antibiotic is in extremely wide use, and the latter is one more rare step on top of an already unlikely chain of events.
Right, which is why I said the bit about bacteria kicking out genes that they don't need. Bacteria will "eject" a plasmid within a generation or two if they no longer need the gene(s) in question. Replicating a big gob of easily-ejectable DNA is not something bacteria do unless there's a good reason to do it.
Basically, for plasmid resistance to propagate, you need to have constant exposure to the antibiotic in question, or the resistance gene needs to be stably integrated into the bacterial genome. The former doesn't happen until an antibiotic is in extremely wide use, and the latter is one more rare step on top of an already unlikely chain of events.
It's not impossible, it's just unlikely.