I'll just refer to my other comment. It may very well have been the right treatment, but I also don't think it's the right move make a patient continue using it and not even change the dosage when it's doing no good. I was instructed to continue to take it despite him eventually moving on to viral, then STD, then HIV, despite my condition getting progressively worse.
The use of antibiotics is actually very institution specific. Hospital usually have antibiotic protocols - the tests that should be run and what drugs are used 1st line, 2nd line, etc.
Antibiotic resistance can be really high at one hospital and really low at another hospital down the street.
https://news.ycombinator.com/item?id=20398927