A bacterium which can cause dangerous infections in those with a weakened immune system can now rapidly develop resistance to antibiotics, researchers warned last night.
Writing in Cell Reports, Professor Craig MacLean of the University of Oxford, UK, and colleagues describe the antibiotic colistin as an important last line of defence for the treatment of infections caused by antibiotic-resistant gram-negative pathogens.
In the laboratory, they gave a high dose of colistin to over 900 populations of a multi-drug-resistant strain of P. aeruginosa.
“Colistin exposure caused rapid cell death,” they report, “but some cell populations eventually recover due to the growth of sub-populations of heteroresistant cells.”
Their results suggest that this pathogen may have evolved a highly mutable gene called pmrB as an adaptation to host immunity. This gene appears to mutate at a rate 1,000 times higher than the ‘normal’ background rate of mutation.
Professor MacLean said: “Our work has shown that a gene involved in resistance to a last resort antibiotic mutates at an incredibly high rate, allowing bacteria to quickly evolve antibiotic resistance.
“For this particular case, selective pressures generated by this gene’s association with the immune system may have driven the evolution of extra-fast mutation rate.”
Kapel, N. et al. Localized pmrB hypermutation drives the evolution of colistin heteroresistance. Cell Reports 7 June 2022; doi: 10.1016/j.celrep.2022.110929
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