How to make a Superbug
It is always scary when someone in your family is admitted to hospital, even if it’s just a routine procedure. No-one wants to stay longer in hospital than they have to, and healthcare-acquired infections happen all the time. These are infections that immunocompromised patients catch while in hospital, which are increasingly caused by superbugs that cannot be killed by any drugs on the market. Prevention is always better than cure, so how do we prevent superbugs from emerging in the first place?
Today we are talking about superbugs - how a scientist can create a superbug in the lab to better understand this whole process, and how this helps science educators better communicate this topic to students.
When I say “superbugs”, I’m talking about bacteria that have developed resistance against a broad range of drugs - namely antibiotics targeted at killing them. Now some bacteria are just naturally resistant to some antibiotics, and it wasn’t a big deal - we would simply go to another antibiotic in our arsenal, built up over decades of scientific research and drug discovery. But we’re running out of options - it is has been years since a brand new category of antibiotic was discovered, and bacteria have developed mechanisms to defend against all of them. If you’re infected by a superbug, doctors don’t have any good options. They can increase the dosage of the antibiotic so much that it becomes toxic for your kidneys and liver, or just hope your immune system can fight off the bug by itself. Not a great treatment plan by any measure.
The Advantage
For a bacteria to become resistant to a drug, it needs to acquire a gene that stop the activity of that drug. Scientists refer to this process as horizontal gene transfer - bacteria move genes to and from each other using a range of different mechanisms - conjugation, transformation, or transduction. If the new gene has no function, then those bacteria will grow normally, and the new gene doesn’t spread very far. If the gene provides a survival advantage though, those bacteria can grow and replicate faster than normal, and naturally that new gene is now present in more bacterial cells.
The key to all of this is how we define survival or selective advantage, which is largely dependent on the environment you’re in. If I’m wearing basketball sneakers designed for running and pivotting on hardwood floors I have an advantage over other players on hardwood courts who are wearing sandals and flip-flops (athletic talent not withstanding). People will realise this, and start wearing the shoes that give them the best advantage in that environment – it spreads. If we change the environment – say we’re playing on concrete, or a slippery grassy field - any advantage I had from wearing those sneakers, is now gone. The same principle applies in gene transfer. Antibiotic resistance genes are only valuable to the bacteria in an environment constantly surrounded by antibiotics. Antibiotic resistance genes would not spread very far at all if there were not antibiotics that the bacteria had to defend against.
The Hook
This all sounds quite abstract, and it can be challenging to convince your students of the importance of antimicrobial resistance without some practical examples. An exercise I ask my students to do is to (safely) make their own superbugs in the lab. The ease at which students can perform genetic manipulations that lead to antibiotic resistance should set off alarm bells…
It shouldn’t be this easy…
So bacteria are doing this by themselves all the time?
Is anyone monitoring or controlling the rate of antibiotic resistance?
I go into more detail in the video below, but these are the basic steps for making a “superbug”:
Identify an antibiotic resistance gene (e.g. beta-lactamases), find its gene sequence and design PCR primers against it
Find a bacterial strain that is safe to work with in PC1 or PC2 labs (suitable for teaching) that contains said gene
Purify genomic DNA from the bacteria using readily available DNA extraction kits
Run a PCR reaction using the PCR primers designed in step 1, against the genomic DNA purified in step 3
Clone the amplified PCR product of the antibiotic resistance gene inside a plasmid
Transform the recombinant plasmid into bacterial cells
Measure the antibiotic resistance of the transformed bacteria using a disk diffusion assay
And there you have it - we’ve chaperoned the transfer of DNA between bacteria, and created a prototype of a superbug. This is all doable across 2-3 prac sessions, and students can experience first hand the ease at which the foundational building blocks of life can evolve within a span of days to weeks. Of course this process needs to be safe for students, and it’s as safe as the gene and bacterial strain you select. Ensure all the right risk assessments are in place, and if in doubt collaborate with research laboratories that are directly working with these reagents.
The Outlook
Superbugs are a problem that modern medicine created. Patients want our doctors to prescribe antibiotics for our sore throats, which are caused by viruses 70-80% of the time - the bacteria-targeting antibiotics won’t help the sore throat recover, it just amplifies the need for antibiotic resistance genes. Hospitals are prescribing more and more antibiotics to prevent surgical wounds from getting infected, and antibiotics are also prescribed to animals and livestock as a growth promoter, so that there is more meat on the bone to be sold to supermarkets. Sure we can try to invent new types of antibiotics, but we simply cannot keep up with the superbugs - they are evolving at a much faster rate than any R&D project, even one financed by billion dollar pharma companies. More superbugs will continue appearing, infecting people in the community as well as patients in hospitals, until we find an effective strategy for monitoring and controlling antibiotic misuse.
Most people aren’t even aware that this is an issue, so it’s our job as scientists and science-lovers to spread the word. When it comes to science communication to the general public, a little bit goes a long way.
Jack.
