Evolution finds a way: resistance to antibiotic of last resort

In the original Jurassic Park movie, Jeff Goldblum’s character, mathematician Ian Malcolm, became known for the phrase: “life finds a way“, referring to the chaotic behaviour of even the most simple systems.  Indeed, the entire movie becomes an exercise in unpacking the meaning of that statement when applied to reviving an entire ecosystem of dinosaurs.  The increasing resistance of pathogens to antibiotics over the last few decades, could be considered a real-world case of evolution finding a way.  It is also a good example of why evolution isn’t just about events of the dim, distant past, but very much the here and now.  I’m often puzzled that the word “evolution” isn’t used more often when describing this significant threat to global public health: a quick Google search shows approximately 11,000 mentions of the phrase “developing antibiotic resistance“, compared with only about 1,800 for “evolving antibiotic resistance“.

Over on Evolution in a Toxic World, toxicologist and fellow Ronin Institute Research Scholar, Emily Monosson, has a very interesting post on a newly evolved, and worrisome, mechanism of resistance to an older class of antibiotics.  This class of antibiotics, polymyins, discovered in the 1940s but not used in recent decades, has been recently revived, as other antibiotics have began to fail.  Unfortunately it seems that pig farmers around the world  have jumped on the polymyin bandwagon and have been using a particular polymyin, colistin, in large quantities.

The evolution of resistance in an otherwise peacefully co-existing gut bacteria such as E. coli,  isn’t that surprising in and of itself.  Resistant mutations occur in the DNA of individual bacteria in contained subpopulations all the time. But Monosson points out that what is new here is that these particular mutants are appearing on a plasmid in E. coli, making it more likely that completely different strains or populations of E. coli could pick up the resistant mutation more easily:

Plasmids are circular bits of DNA that bacteria can pass like a bit of gossip from one bacterium to another. While bacteria reproduce by splitting apart (making little clones) they aren’t completely celibate. Sometimes bacteria engage in microbial hanky-panky and actually conjugate,  joining together passing plasmids from one to the other.

One E. coli may pass its plasmid – and its resistance – to another strain of E. coli (like the infamous E. coli 0157).  Or, it may even engage with an all-together different kind of bacterium, like Klebsiella pneumoniae – notorious for causing pneumonia and other hospital acquired infections.

The concern of course is that colistins have become an antibiotic of last resort. Now we not only have resistance in a common bacterium but one that is ready and able to share.

It seems that evolution really has found a way in this case, and the end of the “antibiotic era” may be just one step closer.

Read more at Evolution in a Toxic World…


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