Massive Use Of "Growth Promoters' (Antibiotics) Powering Antibiotic Resistance In Chinese Pork
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To investigate, Yong-Guan Zhu of the Chinese Academy of Science in Xiamen, James Tiedje of Michigan State University in East Lansing, and colleagues tested soil along with fresh and composted manure at three big Chinese pig farms in different provinces. They also tested compost and manure from Chinese pigs not fed antibiotics, and soil from a remote forest.
Using a quantitative PCR assay to pick up specific DNA sequences, the researchers measured the amounts of 244 different ARGs in their samples. They used the amount of a gene common to all bacterial in the sample as a measure of the total bacteria present, to establish how many ARGs there were for a given number of bacterial cells.
"We were able to measure many more kinds of resistance than had been studied before," Tiedje says. The team's approach gave a clearer picture than traditional investigation methods, in which bacteria in a sample are grown in the lab and then tested for their antibiotic resistance. Many bacterial strains do not culture well and so this older approach risks underestimating antibiotic resistance.
In the farm samples, the team found 149 ARGs that, between them, confer resistance to all classes of antibiotics – and the levels of some were "enriched" 28,000-fold compared to those in the soil samples not taken from farms. "Composting the manure and spreading that on soil reduced the load of some, but not all, types of ARGs," says Tiedje.
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http://www.newscientist.com/article/dn23168-chinese-pig-farms-breed-drugresistant-bacteria.html
