Summary
In a preprint, researchers report that antibiotic selection on human airway tissue favoured Pseudomonas aeruginosa clones that preserved the tissue and survived treatment better. The finding suggests that standard susceptibility measurements can miss infection traits shaped by the host environment.
A bioRxiv preprint reports that evolving Pseudomonas aeruginosa on differentiated human airway epithelium under antibiotic treatment produced an infection state that preserved the tissue while helping the bacteria survive treatment. The result comes from a laboratory airway-tissue model, not observations of patients.
The researchers compared evolution under different conditions, including antibiotic exposure in liquid culture and on airway tissue. Ceftazidime selected canonical resistance mutations in every condition. But only the combination of airway tissue and antibiotic selection produced bacteria that remained restricted to the epithelial surface and caused less damage. These clones survived treatment better than liquid-evolved clones with the same minimum inhibitory concentration, or MIC—the lowest antibiotic concentration that inhibits bacterial growth in a susceptibility test.
The tissue environment shaped the infection
The tissue-preserving phenotype arose independently in three bacterial lineages, through different mutational routes. Its survival advantage also persisted during treatment with tobramycin, an antibiotic not used during evolution, when the compared clones had equal susceptibility to it.
The researchers also disrupted pilA, involved in building type IV pili, or pscC, involved in type III secretion. Each intervention reproduced the tissue-preserving phenotype and enhanced survival without changing antibiotic susceptibility. This links those bacterial systems to the observed infection behaviour, although the abstract does not identify the mutations that arose in each evolved lineage.
Why susceptibility tests may miss this behaviour
MIC measurements describe bacterial growth inhibition under test conditions. The preprint’s results point to another dimension of treatment response: how bacteria behave and survive while interacting with host tissue. Clones with matched MICs can therefore differ in survival in the airway model.
The study suggests that antibiotic selection within host tissue can favour a less damaging mode of infection that nevertheless persists better during treatment. This is a preprint describing experimental evolution in a laboratory model; whether the same process shapes infections or treatment outcomes in patients requires clinical evidence.