Less than a week after the EU, United States and Australian governments held their respective Antibiotics Awareness days, scientists from Washington State University have discovered a possible means of spreading antibiotic resistance.

The researchers warned that indiscriminate use of antibiotics in farming and medicine is accelerating the natural selection processes and threatening the effectiveness of antibiotics. Although antibiotics are still used as growth promoters in US agriculture, a practice which has been banned in the EU, the US authorities have done more to curtail use of some vital antibiotics, including fluoroquinolones.

The WSU researchers found that a widely used cephalosporin antibiotic, which passes through the body in urine, wiped out normal E.coli in manure and soil and allowed resistant bacteria to flourish, with the potential for reinfecting animals through pasture, forage or bedding. The researchers found concentrations of the antibiotics "significantly prolonged persistence of [resistant] bacteria in the soil" and added "We further show that resistant strains readily colonize calves by contact with contaminated bedding and without antibiotic selection pressure."

Dr Doug Call, who led the research commented, "I was surprised at how well this works, but it was not a surprise that it could be happening. Given that about 70 percent of the drug is excreted in the urine, this was about the only pathway through which it could exert such a large effect on bacterial populations that can reside in both the gut and the environment."

Dr Call said that his study is important as it reveals a means of developing antibiotic resistance in the environment, rather than in individual animals, which has previously been the focus of most research into resistance. Although the findings are sobering, the researchers’ investigation was carried out in a laboratory; further experiments will need to be carried out in the field in order to establish whether the process is taking place and its possible effects.

The research was undertaken to test a hypothesis that environmental factors could be contributing to the development of bacteria resistant to Ceftiofur, a cephalosporin. The US Food and Drug Administration has issued new rules on the use of some cephalosphorins due to concerns over increasing resistance to the drugs.

The researchers also pointed out that, "Because ceftiofur degradation is temperature dependent, these compounds may accumulate during colder months and this could further enhance selection as seasonal temperatures increase."

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