Researchers at Osaka University have discovered that polymyxin E-resistant Escherichia coli is widely prevalent among people living in rural Vietnam.

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Polymyxin E is an antibiotic that is used to prevent the growth of Gram-negative bacteria such as E.coli and Pseudomonas aeruginosa. It is one of only a few remaining drugs that can treat multidrug-resistant bacteria and is categorized as a last-resort antibiotic by the World Health Organisation.

Previously, E. coli resistance against this antibiotic was mostly been related to chromosomal mutations. Since this type of resistance is not transferred to other bacterial species, it was not thought to be particularly concerning.

However, a transmissible polymyxin E-resistant gene called mcr1 was found in China in 2015, raising global concerns that the resistance could be transferred to other bacterial species. The transmission of the mcr1 gene to other bacterial species would lead to super resistant "nightmare bacteria" that are resistant to every kind of antibiotic, including the last-resort polymyxin E.

Since drug-resistant bacteria are known to spread through livestock and livestock products in developing countries, Yoshimasa Yamamoto and colleagues hypothesized that the large quantities of polymyxin E being added to animal feed in Vietnam could be driving the spread of resistance. They therefore decided to test the prevalence of the resistant bacteria in rural communities.

As reported in the Journal of Antimicrobial Chemotherapy, the researchers found that the prevalence of polymyxin E-resistant bacteria was extremely high among residents of rural communities; at 70.4%.

They also discovered that the resistant bacteria carried the mcr1 gene, and that the spread of resistance had occured much faster than expected.

Commenting on the significant threat that “nightmare bacteria” could pose in the treatment of infectious disease, Yamamoto says that the number of refractory infections for which antibiotics do not work will increase, significantly affecting clinical practice.