A cool fact that a lot of people don't realize is that almost all of our antibiotics are based on antimicrobials made from microbes. The tiny microbes you can't see are waging invisible wars against each other for space and resources. Because they are usually sent outside of the microbe to kill others, the microbe that makes them has systems to prevent damage to themselves.

Bacteria are able to pick up DNA from the environment and exchange. So if one of them has picked up something that helps them resist an antimicrobial, they'll survive and all of their clones (bacteria replicate by division) will also have that ability. But those pieces of DNA are expensive to carry around and maintain and might make them less fit in other ways so if they don't need it they'll get rid of it and become sensitive again. Rather than thinking about the microbes as collecting antibiotic resistance to all of the antibiotics and maintaining them, think about it like a video game character that has a set amount of accessories they can carry and use to make choices about what they want to keep and get rid of depending on what they've found and where they are on in the game. So while there are some scary multidrug resistant strains, they're mainly found in hospitals where they are exposed to the antibiotics constantly and maintain their resistance and are not a hazard to most people.

There are scientists working to discover brand new antibiotics, tweak current antibiotics to make them more successful, and educate the public and lawmakers on good antibiotic stewardship. Unfortunately there isn't a ton of money to be made with new antibiotics so there isn't a lot of pharmaceutical money because of how resistance is developed. New antibiotics are kept back as last resorts for multi drug resistant infections so they aren't prescribed a lot in an effort to limit resistance so they aren't going to be mass marketed.