Via: NPR: What do you mean?
A lot of Gram-negative bacteria, they come out of the box, if you will, resistant to a number of important antibiotics that we might use to treat them. We're talking about agents with names like Acinetobacter, Pseudomonas, E. coli.
These are bacteria that have historically done a very good job of very quickly developing resistance to antibiotics. They have a lot of tricks up their sleeves for developing resistance to antibiotics, so they're a group of agents that can quickly become resistant, can pose major challenges to resistance.
And what we've seen over the past decade is these Gram-negative agents becoming very rapidly more and more resistant to all of the agents that we have available to treat them.
To all of the agents?
There are Gram-negative bacteria that have developed resistance to everything, for which we have no viable antibiotics left to treat them. …
So why are we so worried about these new bacteria that are Gram negatives, and what's happened recently?
…For a long time we've seen Gram negatives develop resistance to antibiotics, but we had other tricks up our sleeves. We had other antibiotics that we could use.
Increasingly, though, what we've seen is that they're developing resistance even to the agents that we've been sort of holding back and only using in the most serious infections. They were our last, best line of defense, and we now see some of these Gram-negative organisms that are resistant to even that last line of defense.