Threat of 'nightmare bacteria' exhibiting resistance to last-resort antibiotic colistin

The team's research results were published in the Journal of Antimicrobial Chemotherapy.

Colistin, an old antibiotic discovered in 1950, kills or inhibits the growth of Gram-negative bacteria, such as E. coli and Pseudomonas aeruginosa. It is one of the few critical antibacterial drugs for treating multidrug-resistant bacteria and is listed on the WHO Essential Medicines List (EML) as a last-resort antibiotic.

Colistin-resistance is mostly related to chromosomal mutations. Although its frequency was low, a certain level of colistin-resistance was observed. However, since colistin-resistance caused by mutations was not transferred to other bacterial species, it was not considered problematic. However, a transmissible colistin resistance gene (mcr) was discovered in China in 2015 and the possibility of the transfer of colistin-resistance to other bacterial species was shown, becoming a global concern. This presents the potential danger that carriage of mcr1 gene in pathogens with other resistance genes will produce super drug-resistant bacteria called "Nightmare bacteria." This bacteria exhibits resistance to all antibiotics, even to the last-resort antibiotic colistin, posing a great threat in infectious disease treatment.

Drug-resistant strains are spread in livestock and livestock products in developing countries. This group has pointed out that meat contains colistin-resistant bacteria because a large amount of colistin has been added to livestock food in Vietnam.

Thus, the group investigated the prevalence of colistin-resistant bacteria in Vietnam and revealed that the dissemination of colistin-resistant Escherichia coli (CR-E) in the faecal microbiota of residents was extremely high (70.4% of residents) and that CR-E had the transmissible colistin resistance gene (mcr).

First author Yoshimasa Yamamoto says, "CR-E carriers don't cause health problems immediately, but it's clear that the number of refractory infections for which antibiotics don't work will increase, which will become a great menace to clinical practice. In this borderless society, drug-resistant bacteria quickly spread beyond national and regional borders, so it is necessary to strengthen international surveillance systems and promptly take preventative measures."