In the late 1960s US Surgeon General William Stewart declared to Congress “it’s time to close the book on infectious diseases.” After two decades in which deaths from bacterial infection dropped dramatically, and average life span was increasing each year, the top American doctor could be forgiven for thinking infections were a problem for the past.

Just over 40 years later, Dr Stewart’s words are looking as prophetic as the Chairman of IBM’s 1947 declaration that there would be a world market for “maybe five computers”. The book on infectious diseases is threatening to reef back open, with a whole host of bacterial infections ready to pour forth. And with increasing numbers of bacteria proving resistant to treatment, specialists fear we will return to a state where a simple wound infection could prove deadly. This was the case for people living in the 1930s and prior, when more than half the population died from bacterial infections.

This all changed with the discovery of antibiotics, the first of which was penicillin. Alexander Fleming famously discovered this fungal derivative and demonstrated that it killed bacteria. However, he was unable to isolate penicillin. It was only through the work of Howard Florey and Ernst Chain that penicillin was isolated and able to be used in mass-produced medicine.

Penicillin became available during World War II, where it was used to treat infections on soldiers. Its effect was immediate. World War II became the first war since records began where bacterial infection was not the leading cause of death. After the war, when the drug was widely available, deaths from bacterial infection plummeted, leading to Dr Stewart’s misplaced confidence that bacterial infection was no longer an issue for first-world medicine.

Today deaths are on the rise again. In 2010, bacterial infection killed more people than cancer, according to figures from the WHO’s Global Health Observatory Database. In the U.S., hospital-acquired bacterial infections have become one of the leading causes of death, with more people dying from bacterial infections than AIDS and breast cancer combined.

How did we get here? Why are people living in the 21st century subject to the threats from bacteria of the 1930s, when a scratch that became infected was a potential death sentence?

The problem lies with the success of the very antibiotics that propelled us into a golden age where infections were easily treated. The effectiveness of these antibiotics prompted their widespread use, and misuse in some cases, which allowed bacteria to adapt and become resistant to them. An antibiotic might kill most bacteria, but those left alive spread their genes for resistance to other bacteria. When these bacteria reproduced, the result would be a new generation that was larger and with more resistant individuals than the previous generation.

In one way, this shouldn’t be a surprise to health professionals. After all, bacteria have been adapting and developing resistance to antibiotics for billions of years. Antibiotics were in fact originally produced by bacteria for chemical warfare, in order to attack and defend against other bacteria. Today’s antibiotics are a mixture of natural antibiotics derived from bacteria and synthetic antibiotics designed in a laboratory to kill bacteria.

What has surprised researchers is the speed at which this resistance has arisen. Bacteria have been around nearly as long as the Earth, but it’s taken them just 80 years to develop a resistance to mass-produced antibiotics. For individual antibiotics, the time frame is far shorter, with resistant bacteria emerging in less than five years for antibiotics such as linezolid and methicillin.

Today’s bacteria aren’t just resistant, they’re multi-resistant, with genes that enable them to survive the administration of several different types of antibiotics. These bacteria are known informally as ‘superbugs’.

“Multi-resistant bacteria are shaping as a major health crisis,” Professor Matt Cooper from the Institute for Molecular Bioscience said. “It’s one that researchers and health professionals have been recognising for a few years now. Hopefully governments and policy makers will follow, otherwise we’re going to be in serious trouble.

“I think part of the problem is that people can’t imagine going backwards, going back to a time when a simple infection could kill them. However that’s where we are headed if new drugs aren’t developed to combat these bacteria and we re-think how we use antibiotics, both in humans and animals.”

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