Widespread Distribution of Antibiotic-Resistant Bacteria in China

Researchers have detected the gene for colistin- resistance in human, food and environmental samples from Hong Kong and China. A group of Scientists at the Hong Kong Polytechnic University (PolyU) have detected the gene conferring bacteria with colistin resistance in human, food and environmental samples collected from Hong Kong and China.

They published their discoveries in Enrosurveillance. Colistin is a last resort antibiotic used to treat severe infections caused by carbapenem-resistant Enterobacteriaceae strains. The gene that enables bacteria to survive colistin treatment is MCR-1, and assessing the spread of the MCR-1 gene could help in estimating the clinical effect of colistin.

In this examination, a team of researchers led by Professor Chen Sheng of the Food Safety and Technology Research Center at PolyU utilized the polymerase chain reaction to distinguish bacteria that carry the colistin resistance gene MCR-1.

They found that MCR-1 was present in organisms recovered from human samples, and also an extensive variety of food and environment samples. The nature of distribution of MCR-1-bearing organisms in the test samples recommended that MCR-1 resistance initially started in Escherichia coli bacteria present in the gastrointestinal tract of animals.

Subsequently, the MCR-1 gene may have been transmitted to people through the food chain or by direct contact with animals. On the other hand, the contamination of fresh and seawater systems with MCR-1-positive bacteria could have resulted in the eventual contamination of vegetables and seafood.

Persistence of MCR-1 in the human gastrointestinal tract microflora can cause additional contamination of our water systems through improper disposal of wastewater containing human defecation.

Outstandingly, the scientists found that pet animals, which are rarely presented to colistin, exhibited a much lower level of prevalence of MCR-1-positive organisms than livestock. Freshwater reservoirs that were not contaminated by defecation additionally tested negative for the MCR-1 gene.

Among Enterobacteriaceae strains, given the prevalence of MCR-1 in various environmental niches, increased usage of colistin to treat carbapenem-resistant Enterobacteriaceae infections may result in the rapid selection of organisms that show resistance from both carbapenems and colistin.

These discoveries highlight a need to develop effective inhibitors of MCR-1 or intervention measures that disrupt the transmission of MCR-1-bearing plasmids, in order to preserve the value of colistin as a last-line antibiotic for the treatment of life-threatening bacterial infections.

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