|No, that's not what we mean by superbug. We're talking about pathogenic bacteria.|
Speaking of being caught with our pants down, a recent case in point is Neisseria gonorrhoeae, the bacteria that causes gonorrhea. Once easily treated with a shot of penicillin, gonorrhea has quietly evolved resistance to multiple types of antibiotics over the years. Since there is now a danger of gonorrhea being untreatable once again (!), Neisseria gonorrhoeae is considered a superbug by the CDC. Pat Benatar warned us that "Love is a Battlefield"...and now the Huey Lewis request, "I Want a New Drug", takes on an urgent new meaning.
news broke that an elderly woman died in Nevada after losing a battle with a stubborn superbug. She succumbed to an infection caused by CRE - carbapenem-resistant enterobacteriaceae (carbapenem is one of our "last resort" antibiotics that is only used when others have failed). In other words, the bacteria that killed her was immune to every single antibiotic we have in our arsenal.
So how do bacteria develop resistance to our medicines? There are at least four different ways. One, bacteria can mutate, or change, the protein that is targeted by the antibiotic. For example, penicillin inhibits a bacterial enzyme called transpeptidase, which is required by the bacteria to build its cell wall properly. Bacteria that acquire a DNA mutation that makes a slightly different version of transpeptidase can become resistant to penicillin (the new version can still build the cell wall, but no longer interacts with penicillin). A related strategy bacteria can use involves increasing the amount of the drug target; in other words, the bacteria could make more transpeptidase - too much for the drug to inhibit effectively.
Two, the bacteria can acquire a gene that makes a protein called penicillinase, which can directly attack the penicillin compound and cut it up. Some bacteria already have this gene and can pass it along to other bacteria that do not have it. Penicillinase is like a bomb diffuser - the bacterial equivalent of Sergeant First Class William James in The Hurt Locker.
Three, bacteria can mutate proteins that are needed for the antibiotic to get into the bacteria cells. Finally, bacteria can also use "efflux" proteins to pump out the antibiotic. These two related strategies effectively keep the antibiotic out of the bacteria and away from its target. A cartoon summary of these mechanisms of antibiotic resistance is shown below.
In summary, bacteria have many ways to combat the drugs we use to kill them. We need to step up our game and fast if we want to stay ahead of the devastating infections bacteria inflict upon us. We need more kryptonite to defeat the superbugs!
For more on why bacteria develop resistance to antibiotics, check out this informative video from Everyday Elements.
Contributed by: Bill Sullivan
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Blair, J., Webber, M., Baylay, A., Ogbolu, D., & Piddock, L. (2014). Molecular mechanisms of antibiotic resistance Nature Reviews Microbiology, 13 (1), 42-51 DOI: 10.1038/nrmicro3380