Antibiotic awareness week has been given a whole new meaning this year due to one particularly eye-opening discovery. We have been slowly emptying our armory of antibiotics for a while now, with few new examples being developed in the past two decades and new infectious diseases being discovered almost every year. We’re also living in a time when diseases are evolving and becoming increasingly resistant to antibiotics, and it looks like they’ve now breached our last line of defense.
A report in The Lancet Infectious Diseases has just revealed the existence of bacteria with resistance to the most aggressive of our antibiotics; a drug known as Colistin. Colistin has had a rough history, being deemed too toxic for human use not long after its discovery due to the damage it caused to kidney cells. But it made a comeback in the early 2000s when more drug resistant bacteria began to emerge, and kidney damage started to seem like the lesser of two evils. And by 2012, the World Health Organisation had classified Colistin as critically important for human health.
But, unknown to the many medical professionals in the West, Colistin was also being used in China. While it was never approved for human use, understandable considering its toxicity, it was approved for use in animals. It has been known for quite some time that feeding animals with low doses of antibiotics fattens them up, and the local pig farmers took to using large quantities of Colisten for this very reason.
This near constant use of Colisten meant that bacteria were being repeatedly exposed to it; long enough for them to learn how to fight back. Colistin resistance has occurred in the past, but the relevant gene was found in the chromosomal DNA, and could not be passed on to non-resistant bacteria. But these guys were a cut above the rest. This time the mutation, now dubbed MCR-1, occurred in the plasmid. This is a circular loop of DNA that all bacteria posses, and it can be passed on in a process called horizontal gene transfer. This is outlined in the graphic below.
This means there is now potential for the resistance gene to end up in the DNA of many different species of bacteria, and it has already been found in some known to cause infections in humans, such as E.Coli and Klebsiella Pneumonia. Now this wouldn’t be so bad if the gene could effectively quarantined, but the researchers report that the gene is already widespread in southern China. The study found that the gene was present in 15% of meat samples and 21% of animals tested between 2011 and 2014, as well as 16 of 1322 samples taken from humans. To make matters worse, there is also some evidence that the gene has managed to spread outside of China in to countries such as Laos and Malaysia.
If this gene continues to spread, which is highly likely since reports state that it has an extremely high transfer rate, then we could see the emergence of “pan-resistant bacteria” – bacteria resistant to all known methods of treatment. This is a very frightening prospect for modern medicine, and if MCR-1 combines with other resistance genes, then medicine could be launched back in to the dark ages. As Professor Timothy Walsh told BBC news, “At that point if a patient becomes seriously ill, say with E. Coli, then there is virtually nothing you can do”.
But the apocalypse is not upon us yet! Although the prospect of the MCR-1 gene going global seems to be a case of when not if, we still have time to prevent a complete breakdown of modern medicine if we act fast enough. There are even new antibiotics that could help delay the onset of the post-antibiotic era, such as Teixobactin, that are currently being researched. But this is not something we should rely on, as it is still a long way from being ready for medical use.
This is one hell of a wakeup call, and the authors of the report know this, stating that their findings “emphasise the urgent need for coordinated global action” in the fight against antibiotic resistance. Whether it’s through the discovery of new antibiotics or entirely new methods of treatment, we need to work together to restock our armory and find new weapons to combat this new breed of superbug. If not, deaths from routine surgeries and minor infections could become commonplace once again due to the lack of treatment options. So let’s hope our scientists are on the case! They have quite the challenge ahead.
- Bsac.org.uk,. (2015). Antimicrobial resistance poses ‘catastrophic threat’, says Chief Medical Officer. Retrieved 23 November 2015, from http://bsac.org.uk/antimicrobial-resistance-poses-catastrophic-threat-says-chief-medical-officer/
- Gallagher, J. (2015). Antibiotic resistance: World on cusp of ‘post-antibiotic era’ – BBC News. BBC News. Retrieved 23 November 2015, from http://www.bbc.co.uk/news/health-34857015
- Liu, Y., Wang, Y., Walsh, T., Yi, L., Zhang, R., & Spencer, J. et al. (2015). Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study. The Lancet Infectious Diseases. http://dx.doi.org/10.1016/s1473-3099(15)00424-7
- MacKenzie, D. (2015). Bacteria now resistant even to ‘last resort’ antibiotics. newscientist.com. Retrieved 23 November 2015, from https://www.newscientist.com/article/dn28513-bacteria-now-resistant-even-to-last-resort-antibiotics/
- Zhang, S. (2015). A Once Powerful Antibiotic Goes the Way of All Flesh. wired.com. Retrieved 23 November 2015, from http://www.wired.com/2015/11/colistin-last-report-antibiotic-drug-resistance/