Back-teria in black

Mark Condon explains why heavy metals incur antibiotic resistance in common bacterial strains

When the first antibiotics were invented, it must have seemed like diseases caused by bacteria would soon be a thing of the past. These amazing drugs could hunt down and kill harmful microbes with little effect on the patient; the holy grail of drug treatment.

However, over the last century, more and more antibiotic-resistant strains of common bacteria have been discovered. Resistant ‘superbugs’ like MRSA, immune to the usual treatments, are a constant threat to vulnerable patients. According to the World Health Organisation, superbugs kill 25,000 people every year in the EU.

The blame for this phenomenon is usually placed squarely on irresponsible users of antibiotics; the patient who doesn’t finish their prescribed course, or the farmer who feeds antibiotics to their livestock to keep diseases, and costs, down. These approaches kill normal, non-resistant bacteria and allow the resistant strains to grow and spread even more rapidly.

However, new research suggests that there might be another major cause. Oddly enough, antibiotic resistance seems to relate to the amount of metal in the ground. The findings were made by a group of experts, including Professor David Graham of Newcastle University, who studied soil samples collected from various sites across Scotland. They measured the number of genes in bacteria  relating to antibiotic resistance, and found that it was higher in areas with metals like copper, lead and tin in the soil.

The mechanisms microbes use to avoid antibiotics were originally developed to survive the effects of environmental chemicals. Lead is toxic to most organisms, ourselves included, and bacteria on copper surfaces die within hours. Those that don’t evolve fast enough are killed by these natural poisons, and those that can recognise a harmful chemical, and dispose of it, survive and grow. Developing antibiotic resistance might just have been a case of learning to throw out a few more chemicals along with the rest.

So what does this mean for the future of antibiotics? Professor Graham said “One implication of this result is that past mining areas, such as Cornwall with soils rich in tin and copper, or Northumberland with its former zinc and lead mines, might have an intrinsically higher potential for antibiotic resistance than elsewhere.” Bad news for mining towns, where the bigger populations of resistant bacteria might result in more superbug infections.

It’s not all doom and gloom though; Dr Charles Knapp from the University of Strathclyde, Glasgow, who led the research, suggested that: “With our chemical arsenal to battle infections ever decreasing, the findings will help to develop an effective approach to address these environmental factors.” Hopefully, further research in this field could eventually lead to a more permanent solution to the resistance problem; until then, the chemical arms race continues.