Resistant super-bugs lead to extinction

Such trials are desperately needed. We are on the threshold of returning to the dark ages that preceded antibiotics. In the late 19th century, tuberculosis was humanity’s greatest scourge. Robert Koch, who identified the causative Mycobacterium tuberculosis, estimated that “one-seventh of all humans die of tuberculosis”. The disease is now on its way to becoming untreatable once more. Every year, nearly half a million new cases of multidrug-resistant tuberculosis (MDR-TB) occur world-wide. Extensively drug-resistant tuberculosis (XDR-TB) strains, impervious to the most potent antibiotics in our arsenal, have already reared their head.

Even normally benign bacteria like Staphylococcus aeureus – golden staph – which harmlessly colonises our skin and nostrils, can cause lethal infections if they hitch a ride into the bloodstream on a catheter or through a surgical incision.

In the post-antibiotic era, drug-resistant strains could render elective surgery, like knee or hip replacements, too risky. According to a 2016 review from Britain led by economist Jim O’Neill, by 2050 drug-resistant infections could kill 10 million people each year – higher than the toll from cancer.

Our profligate use of antibiotics is responsible. Antibiotics unleash massive die-offs within bacterial ecosystems. In a textbook case of evolution, that antibiotic-laden environment selects for the rare bacterium that happens to have acquired a resistance gene. By mechanisms that range from shredding or pumping out the antibiotic to shielding vulnerable targets, resistance genes enable bacteria to dodge whatever weapons we throw at them.

Thus armed, a single bacterial cell can quickly blossom into a resistant army of trillions. The resistance genes, which are carried on rings of DNA called plasmids, can be shared with unrelated bacteria like the latest piece of malware. Since the first use of penicillin more than 70 years ago, this story has played out for every antibiotic deployed. In most cases, resistance emerges within a few short years.

In 2015 a new shock emerged. Researchers in China reported finding E. Coli bacteria in pigs, chicken and humans that had acquired a plasmid that made them resistant to colistin, an antibiotic of last resort. It’s not often used in humans because it causes kidney damage, which is why it had remained effective. But in China, and other places, this cheap antibiotic has been a mainstay of animal farming. Indeed 70% of our global use of antibiotics is for the purpose of accelerating growth in farm animals, reducing the time needed to get them ready for market. The 2015 report in Lancet Infectious Diseases made it clear that resistant bugs in farm animals could spread their malware to bacteria that infect humans – till then a hypothetical risk. China banned the use of colistin in farm animals a year later.

Until recently, we’ve managed to out-manoeuvre disease-causing bacteria. When one antibiotic succumbed to resistance, there was another popping out of the pipeline. Over the past few decades, however, the steady flow has dried to a trickle.

Pharmaceutical makers see little profit in the costly development of new antibiotics. That’s because, at least in the near future, the majority of infections will still be treatable by available low-cost antibiotics. That leaves a relatively small market for the new drug. “For a pharmaceutical company, the economics just don’t make any sense,” says chemist Mark Blaskovich from the University of Queensland. “Why would you invest in something where it’s a single two-week course and you’re cured, as opposed to an ongoing therapy [like new treatments for cancer] costing thousands, or hundreds of thousands, of dollars a year.”

According to a recent report from the PewCharitable Trust, just 40 antibiotics are chugging along the drug development pipeline, compared to several hundred drugs for cancer. To make matters worse, bacteria are increasingly arming themselves with multiple resistance mechanisms. When it comes to treating gonorrhoea and tuberculosis, for example, doctors now have few drugs that still work.

While health authorities like the World Health Organisation exhort the community to limit their use of antibiotics to slow the spread of resistant bacteria, it won’t eliminate the hordes of resistant microbes already in our midst. In 2014, at the time of announcing the O’Neill-led review, then British prime minister David Cameron warned: “If we fail to act, we are looking at an almost unthinkable scenario where antibiotics no longer work and we are cast back into the dark ages of medicine.”. Now we are “beyond a tipping point”, according to Michael Gillings, a microbiologist at Macquarie University, Sydney. “It might have been possible to stop this 40 to 50 years ago,” he says, “now we have the problem forever.”