I am not sure I understand the logic your doctor is using in saying “Because I've had surgery, my doctor says I can never take z's again, they're too weak.” While it is true more and more organisms are becoming resistant to standard antibiotics, it is not you becoming resistant, but the bacteria. The bacteria you may have needed to fend off post surgery last time are not the same ones you may encounter next time. Automatically, using a higher-powered antibiotic without trying a standard antibiotic first, is one of the reasons we are in the situation we are in with an ever increasing population of antibiotic resistant organisms.

Pete