This week, as MEPs advocated banning collective and preventive antibiotic treatment of animals, researchers at Newcastle University warned that policy makers risk ‘losing the fight’ against antibiotic resistance, unless they tackle the problem of resistance on all fronts.

Researchers said research shows that resistant genes, which could eventually make bacteria impossible to treat with even last resort medicines, are freely crossing environmental, agricultural and clinical boundaries.

Newcastle experts looked at soil archives dating back to 1923 and found a parallel between the appearance of antibiotic resistant bacteria in medicine and similar resistant microorganisms in agricultural soils treated with animal manure. Collected from a soil fertility experiment which has been running for more than one hundred years in Denmark - where antibiotics were banned in agriculture from the 1990s for non-therapeutic use - the soil archives provided an 'antibiotic resistance timeline' that reflects resistant genes found in the environment and the evolution of the same types of antibiotic resistance in medicine.

What’s more, the researchers said their findings indicate that using manure and antibiotic substitutes can allow soil bacteria to acquire resistance genes to new antibiotics. They recommended “reducing antibiotic use across all sectors if we are to reduce global antibiotic resistance.”

Though their findings are worrying, the Newcastle researchers’ stay is not the first to identify antibiotic resistance in the environment; last year scientists from Warwick’s School of Life Sciences and Exeter University warned that human and agricultural waste are both playing a role in the release of antibiotic resistant bacteria into the environment.
 
This week, David Graham, a Professor of Ecosystems Engineering who led the Newcastle University study commented, "The observed bridge between clinical and agricultural antibiotic resistance means we are not going to solve the resistance problem just by reducing the number of antibiotics we prescribe in our GP clinics.

"To reduce the global rise in resistance we need to reduce use and improve antibiotic stewardship across all sectors. If this is not done, antibiotic resistance from imprudent sectors will cross-contaminate the whole system and we will quickly find ourselves in a situation where our antibiotics are no longer effective."

Antibiotics have been used in medicine since the 1930s, saving millions of lives. Two decades later they were introduced into agricultural practices and Denmark was among the leaders in employing antibiotics to increase agricultural productivity. However, Denmark also took a leading role in phasing out non-therapeutic use of antibiotics once warnings began to be made about growing resistance and the role this could play.

Looking for genes which could confer resistance to medically important antibiotics, researchers from the Universities of Newcastle, Aarhus and Strathclyde found low levels of the genes in manured soil samples before 1960, but a rise from the 1970s onwards, peaking in the mid ‘80s.

"We chose these resistant genes because their appearance and rapid increase in hospitals from 1963 to 1989 is well-documented," Professor Graham explained. "By comparing the two timelines, we saw the appearance of each specific gene in the soil samples was consistent with the evolution of similar types of resistance in medicine. So the question now is not which came first, clinical or environmental resistance, but what do we do about it?"

Following the ban on non-therapeutic antibiotic use in Danish agriculture, farmers substituted metals for antibiotics, such as copper, and levels of the genes in the manured soils declined rapidly, reaching pre-industrialisation levels by 2010.

However, at the same time the team measured a 10-fold rise in Class 1 Integrons. These are gene carrier and exchange molecules - transporters which allow bacteria to readily share genes, including resistance genes. This suggests that even using antibiotic substitutes, such as copper, may be 'priming' the soils, readying them for increased resistance transmission in the future, the researchers warned.

"Once antibiotics were banned, operators substituted them with copper which has natural antibiotic properties," Professor Graham explained. "More research is needed but our findings suggest that by substituting antibiotics for metals such as copper we may have increased the potential for resistance transmission.

"Unless we reduce use and improve stewardship across all sectors - environmental, clinical and agricultural - we don't stand a chance of reducing antibiotic resistance in the future."