Only two truly new (new mechanism of action) antibiotics have been developed in the last 30-40 years. A number of new antibiotics were approved in the 80's and 90's, but I wouldn't say people thought we had won the war.

The really challenging thing with antibiotics (as a reply below notes) is that if you create a great new antibiotic, nobody will use it unless they have to.

There is resistance out there, but for most infections, the 40+ year old antibiotics work just fine. It's not like almost every other disease where the best drug gets used first line.

Unless the financial incentives are fixed, it's unlikely there will be enough incentive to do the R&D to create new antibiotics.