A study, led by Rice University environmental engineer Pedro Alvarez, published in the American Chemical Society journal Environmental Science and Technology Letters revealed antibiotic-resistant bacteria were not only escaping purification but also breeding and spreading in water treatment plants. Scientists from Rice, Nankai and Tianjin Universities participated in this joint research. They found significant levels of “superbugs” carrying New Delhi Metallo-beta-lactamase (NDM-1) in treated water disinfected by chlorination. The gene NDM-1 was first identified in India.
There’s no antibiotic that can kill them.
“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 waste water. But it turns out these microbes are growing. They’re eating sewage, so they proliferate. In one waste water 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 and are very difficult to treat. These have been found on every continent except for Antarctica, the researchers wrote. NDM-1 is capable of making common bacteria such 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.
Alvarez and his team confirmed the microbes treated by waste water plants that still carried the resistant gene could transfer it via plasmids to otherwise benign bacteria.
A subsequent study by Alvarez and his colleagues published this month in Environmental Science and Technology defined a method to extract and analyze antibiotic-resistant genes from water and sediment and applied it to sites in the Haihe River basin in China, which drains an area of intensive antibiotic use. The study showed plasmids persist for weeks in river sediment, where they can invade indigenous bacteria.
“It turns out that they transfer these genetic determinants for antibiotic resistance to indigenous bacteria in the environment, so they are not only proliferating within the waste water treatment plant, they’re also propagating and dispersing antibiotic resistance,” Alvarez said.
“This calls for us to take a look at these breeding grounds for antibiotic-resistant bacteria and how we might be able to create better barriers than chlorination,” he said. “I think we need to take a serious look at photo-disinfection processes, like ultraviolet disinfection. It has been shown to be more effective on resistant organisms. We also need a better understanding of how these microbes flow through the environment.”