Quite possible, especially because there's a safe haven of antibiotic-free medium just across the border, and the likelihood of a beneficial mutation is correla

Quite possible, especially because there's a safe haven of antibiotic-free medium just across the border, and the likelihood of a beneficial mutation is correlated with the number of individuals present. In a properly-applied therapeutic situation, there is no such safe haven, and one hopes that the subject's immune system would be able to exterminate the much smaller load once the antibiotic's done its job, instead of leaving any stragglers behind to develop resistance.