Bacteria are Philosophers

First published: 12th February 2011

Some bacteria have been studying, and studying Friedrich Nietzsche in particular. I'm talking about Methicillin-resistant Staphylococcus aureus, usually referred to as MRSA, or just the "Super-Bug".

It has been known for a long time (it was discussed when I was a Microbiology undergraduate in the early 1980's) that bacteria can do cool things with drug resistance. Many bacteria carry little extra circles of DNA called plasmids which can copy themselves and be transferred to other bacteria, even ones of different species. Some plasmids code for antibiotic resistance, maybe resistance to more than one antibiotic. The problem for people comes when a bacterium that can cause a disease suddenly acquires resistance to a whole bunch of antibiotics. We can no longer treat the disease with antibiotics, and must rely mostly on the body's natural defences, which can be overwhelmed. That's what the Super-Bug is, a fairly common bacteria, Staphylococcus aureus, which is often found on people's skin, or in their nose, and may cause a range of infections, from the very mild, like acne, to deadly, like staphylococcal endocarditis, but with an added package of genes that make our best antibiotics ineffective.

To anyone who has just heard the entry-level, schoolbook version of evolution: organisms inherit genes from their ancestors and their environment kills the least suitable; the idea of bacteria swapping groups of genes around, even between species, seems weird. However, it fits in beautifully with the Selfish Gene perspective of evolution: organisms don't matter, it is genes being selected.

Now, for a bacterium, carrying a plasmid isn't easy, there are extra genes to turn into proteins, true, those genes make the bacterium resistant to antibiotics, but, if there aren't antibiotics around, bacteria with a plasmid are probably going to get outgrown by the ones without a plasmid. In a wild environment with no antibiotics, most bacteria will be non-resistant. But if people routinely take antibiotics for minor infections, say a sore throat that will clear up in a few days anyway, then to be a surviving bacterium, you want that resistance. Swap those plasmids!

Worse, people feel better as the infection reduces, before it is completely gone. Then, they might not bother finishing the course. The bacteria that are left are the most resistant ones, and they will grow and spread, perhaps to someone who has shared a doorhandle, to cause a less-treatable infection. They are the Nietzschian Bacteria - the antibiotics that did not kill them made them stronger.

"What does not destroy me, makes me stronger", is Nietzsche's best known quote, actually, he wrote, "Was mich nicht umbringt, macht mich stärker", in 1888 in his book Twilight of the Idols, and I should thank the translators who make knowledge more available. But I've often thought it is not a convincing aphorism, leprosy is just one of many things that doesn't kill but clearly weakens a person. It only occurred to me today that antibiotic resistance was one area where Nietzsche was right. My advice to bacteria is: read Nietzsche. To people: finish the job. Don't use antibiotics for every minor infection, and when you do need them, take the full course, or that which does not kill you, might get you the next time it tries.

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