Tuesday, May 19, 2009
Wastewater Treatment Plants Generate Superbugs
The biological reactor is a rich soup of everything liquid produced by a city, including hormones from anticonceptive pills, antibiotics and all kinds of biological stressors. Bacteria in this soup live and reproduce interchanging genetic material, and soon all the biomass becomes antibiotic resistant. In the first known study of its kind, Chuanwu Xi of the University of Michigan School of Public Health and his team sampled water containing the bacteria Acinetobacter at five sites in and near Ann Arbor's wastewater treatment plant.
They found the so-called superbugs—bacteria resistant to multiple antibiotics—up to 100 yards downstream from the discharge point into the Huron River. 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. "Twenty or 30 years ago, antibiotics would have killed most of these strains, no problem," he said.
Multiple antibiotic-resistant bacteria has emerged as one of the top public health issues worldwide in the last few decades as the overuse of antibiotics and other factors have caused bacteria to become resistant to common drugs. Xi's group chose to study Acinetobacter because it is a growing cause of hospital-acquired infections and because of its ability to acquire antibiotic resistance. Pic: Kever Banjamin's Wastewater Plant in 1996.