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  • Alex Cloherty

How does antibiotic resistance work?

Most of you have probably heard the phrase "antibiotic resistance" being thrown around lately. This is becoming an increasingly large problem, but has been looming at the edge of the microbiology world for a long time. In fact, Alexander Fleming, the guy who discovered penicillin (the first antibiotic used in modern Western medicine), actually predicted that bacteria would develop resistance to the very "wonder drug" he had just found. But how do bacteria suddenly get this superpower that allows them to beat the drugs we throw at them?

You can think of the bacterial struggle to survive antibiotics like a human struggle to win a sprint at the Olympics. This task has a few parts to it. Probably more than a few, actually, but I'm not an expert on sprinting so please humour me here. First, if you want to be the best sprinter in the world, you need to have a body that can physically push you forward fast enough. Sprinters with some natural talent often rise above the ones lacking the sprinter's body type early on in qualifying rounds. The same goes for bacteria. Within each bacterial species are many different individual bacteria, just like for humans. And just like for humans, each bacterium has different traits. And some have a "body type" that lets them better survive the onslaught of antibiotics. It's these bacteria who make it through to the next round: it's these ones that survive the first days of an antibiotic treatment. As you continue taking antibiotics, you can view this as the next qualifying rounds for the Olympics: more and more individual bacteria are weeded out of the pool. The big difference between the bacteria and the Olympic runners here is that if you've taken the right antibiotics for the right time course, by the end of the qualifying rounds all the remaining bacteria will have died or be so tired out that your immune system can kill the rest.

There is a second part to this analogy, as well: training. This is where we have been running into many problems lately. Just like humans will be better to do Olympic level sprints if they've been runners all their lives, bacteria will collectively be better able to survive a dose of antibiotics better if they've already been living in a stew of antibiotics. The 'slow' bacteria will have already been weeded out, so you'll only be left with the fastest sprinters. This stew is exactly the kind of environment we give bacteria by over-using antibiotics, for instance in agriculture or by over-prescribing for human illnesses. ​

So how can we help prevent the "bad" bacteria from taking over the world again with their antibiotic resistance superpowers? For most of us, the main thing is not to over-use antibiotics ourselves. It's hard if you're feeling sick, but don't take antibiotics that haven't been prescribed specifically for a bacterial infection. In fact, if you over-use antibiotics, for instance by taking them when you have a viral infection, you may do more harm than good by killing some of your "good" bacteria. Antibiotics can only help with bacterial infections (antivirals are used against viral infections like the flu). Personally, if I go to a doctor with flu-like symptoms and he or she suggests that I take antibiotics without doing any tests to confirm that what I have is bacterial, I don't go back to that doctor.

That's all for this week - until next week, stay healthy and use normal (antibiotic-free) soap!

- Alex

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