Antibiotic-Resistant Bacteria Widespread In China

Scientists in Hong Kong have detected the gene for colistin-resistance in human, food and environmental samples from Hong Kong and China.

AsianScientist (Dec. 15, 2017) – A team of researchers 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 finings in Enrosurveillance.

Colistin is a last-resort antibiotic used to treat severe infections caused by carbapenem-resistant Enterobacteriaceae strains. The gene that allows bacteria to survive colistin treatment is mcr-1, and assessing the spread of the mcr-1 gene could help in estimating the clinical impact of colistin.

In this study, a team of scientists led by Professor Chen Sheng of the Food Safety and Technology Research Centre at PolyU used the polymerase chain reaction to identify bacteria that carry the colistin resistance gene mcr-1. They found that mcr-1 was present in organisms recovered from human samples, as well as a wide range of food and environment samples.

The nature of distribution of mcr-1-bearing organisms in the test samples suggested that mcr-1 resistance first originated in Escherichia coli bacteria present in the gastrointestinal tract of animals. Subsequently, the mcr-1 gene might have been transmitted to humans through the food chain or by direct contact with animals.

Alternatively, the contamination of fresh and seawater systems with mcr-1-positive bacteria could have resulted in the eventual contamination of vegetables and seafood. The persistence of mcr-1 in the human gastrointestinal tract microflora can cause further contamination of our water systems through improper disposal of wastewater containing human feces.

Notably, the researchers found that pet animals, which are rarely exposed to colistin, exhibited a much lower level of prevalence of mcr-1-positive organisms than livestock. Fresh water reservoirs that were not contaminated by feces also tested negative for the mcr-1 gene.

Given the prevalence of mcr-1 among Enterobacteriaceae strains in various environmental niches, increased usage of colistin to treat carbapenem-resistant Enterobacteriaceae infections may result in rapid selection of organisms that exhibit resistance to both carbapenems and colistin.

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

The article can be found at: Chen et al. (2017) Widespread Distribution of MCR-1-bearing Bacteria in the Ecosystem, 2015 to 2016.


Source: Hong Kong Polytechnic University; Photo: Shutterstock.
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