Sewage sludge contains large amounts of triclosan, a component of toothpastes, soaps and cleaning products. It is known that even in small amounts this substance can cause the growth of dangerous bacteria that are resistant to antibiotics. An article with the results of a study of triclosan in wastewater scientists at the University of Toronto (Canada) and the University of Chinese Academy of Sciences was published in the journal Environmental Science & Technology.The researchers analyzed sewage sludge at an Ontario wastewater treatment plant where both antibiotics and other substances with antimicrobial activity accumulate. These compounds are known to contribute to the natural selection of resistant microorganisms that can potentially cause severe infections that are not amenable to conventional treatment. Sewage sludge contains thousands of unknown compounds, but scientists have identified only those that affect Escherichia coli.A total of 10 samples of sewage sludge were extracted, with six of them demonstrating a significant inhibitory effect on the growth of E. coli. Scientists screened suspicious substances when searching for substances whose exact structure is unknown, but a number of properties they are supposed to have are known. A total of 103 candidate substances were identified from 10 samples of sewage sludge, with triclosan, an inhibitor of the bacterial enzyme enoyl-ACP reductase (FabI), being the most common.Because there are so many different antibiotics in sewage sludge, the researchers were surprised to find that most of the antibacterial activity of sludge could be directly related to triclosan alone, says lead study author Holly Barrett.The scientists explain that triclosan is still used in thousands of different household and cosmetic products, as well as in medical settings. And despite the fact that there are several rules limiting the maximum amount of triclosan in consumer products, even very low levels of this chemical can eventually lead to the formation of antibiotic-resistant bacteria.Today, antibiotic resistance is considered one of the greatest threats to global health. Around the world, infections that were once easy to treat, such as pneumonia, tuberculosis, gonorrhea and salmonellosis, are becoming increasingly difficult to treat as the antibiotics used become less effective. Between 2014 and 2016, there were 700,000 deaths worldwide attributed to antibiotic-resistant bacteria.
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