Bacteria create aquatic superbugs in waste treatment plants
They found the so-called superbugs - bacteria resistant to multiple antibiotics - up to 100 yards downstream from the discharge point into the Huron River. Xi stresses that while the finding may be disturbing, it is important to understand that much work is still needed to assess what risk, if any, the presence of superbugs in aquatic environments poses to humans.
"We still need to understand the link between aquatic and human multiple drug resistant bacteria," said Xi, assistant professor of public health.
Xi and colleagues found that while the total number of bacteria left in the final discharge effluent declined dramatically after treatment, the remaining bacteria was significantly more likely to resist multiple antibiotics than bacteria in water samples upstream. Some strains resisted as many as seven of eight antibiotics tested. The bacteria in samples taken 100 yards downstream also were more likely to resist multiple drugs than bacteria upstream.
"Twenty or 30 years ago, antibiotics would have killed most of these strains, no problem," he said.
Xi said the problem isn't that treatment plants don't do a good job of cleaning the water - it's that they simply aren't equipped to remove all antibiotics and other pharmaceuticals entering the treatment plants. The treatment process is fertile ground for the creation of superbugs because it encourages bacteria to grow and break down the organic matter. However, the good bacteria grow and replicate along with the bad. In the confined space, bacteria share resistant genetic materials, and remaining antibiotics and other stressors may select multi-drug resistant bacteria.
The next step, said Xi, is to see how far downstream the superbugs survive and try to understand the link between aquatic and human superbugs. This study did not look past 100 yards.
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