Study reveals that two wastewater treatment plants in China fail to kill antibiotic-resistant bacteria

Published on December 17, 2013 at 3:41 AM · No Comments

Rice U. study: 2 wastewater treatment plants in China fail to kill antibiotic-resistant bacteria

Tests at two wastewater treatment plants in northern China revealed antibiotic-resistant bacteria were not only escaping purification but also breeding and spreading their dangerous cargo.

Joint research by scientists from Rice, Nankai and Tianjin universities found "superbugs" carrying New Delhi Metallo-beta-lactamase (NDM-1), a multidrug-resistant gene first identified in India in 2010, in wastewater disinfected by chlorination. They found significant levels of NDM-1 in the effluent released to the environment and even higher levels in dewatered sludge applied to soils.

The study, led by Rice University environmental engineer Pedro Alvarez, appeared this month in the American Chemical Society journal Environmental Science and Technology Letters.

"It's scary," Alvarez said. "There's no antibiotic that can kill them. We only realized they exist just a little while ago when a Swedish man got infected in India, in New Delhi. Now, people are beginning to realize that more and more tourists trying to go to the upper waters of the Ganges River are getting these infections that cannot be treated.

"We often think about sewage treatment plants as a way to protect us, to get rid of all of these disease-causing constituents in wastewater. But it turns out these microbes are growing. They're eating sewage, so they proliferate. In one wastewater treatment plant, we had four to five of these superbugs coming out for every one that came in."

Antibiotic-resistant bacteria have been raising alarms for years, particularly in hospital environments where public health officials fear they can be transferred from patient to patient and are very difficult to treat. Bacteria harboring the encoding gene that makes them resistant have been found on every continent except for Antarctica, the researchers wrote.

NDM-1 is able to make such common bacteria as E. coli, salmonella and K. pneumonias resistant to even the strongest available antibiotics. The only way to know one is infected is when symptoms associated with these bacteria fail to respond to antibiotics.

In experiments described in the same paper, Alvarez and his team confirmed the microbes treated by wastewater plants that still carried the resistant gene could transfer it via plasmids to otherwise benign bacteria.

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