Bacteria develop resistance through three hidden mechanisms doctors didn't know about
Researchers discovered that dangerous bacteria like E. coli survive antibiotics by amplifying resistance genes through multiple genetic tricks—tandem copying, plasmid multiplication, and mobile gene insertion. These mechanisms are unstable and reversible, but can still cause treatment failures in patients, forcing a rethink of how hospitals should dose and monitor antibiotic therapy.
Originaltitel: Three concurrent mechanisms generate gene copy number variation and transient antibiotic heteroresistance
<p>Heteroresistance is a medically relevant phenotype where small antibiotic-resistant subpopulations coexist within predominantly susceptible bacterial populations. Heteroresistance reduces treatment efficacy across diverse bacterial species and antibiotic classes, yet its genetic and physiological mechanisms remain poorly understood. Here, we investigated a multi-resistant <em>Klebsiella pneumoniae</em> isolate and identified three primary drivers of gene dosage-dependent heteroresistance for several antibiotic classes: tandem amplification, increased plasmid copy number, and transposition of resistance genes onto cryptic plasmids. All three mechanisms imposed fitness costs and were genetically unstable, leading to fast reversion to susceptibility in the absence of antibiotics. We used a mouse gut colonization model to show that heteroresistance due to elevated resistance-gene dosage can result in antibiotic treatment failures. Importantly, we observed that the three mechanisms are prevalent among <em>Escherichia coli</em> bloodstream isolates. Our findings underscore the necessity for treatment strategies that address the complex interplay between plasmids, resistance cassettes, and transposons in bacterial populations.</p>