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Phenotypes of a Pseudomonas aeruginosa hypermutator lineage that emerged during prolonged mechanical ventilation in a patient without cystic fibrosis

Nozick SH, Ozer EA, Medernach R, Kochan TJ, Kumar R, Mills JO, Wunderlink RG, Qi C et al.

mSystems, 2024

7 citations

Abstract

Hypermutator lineages of Pseudomonas aeruginosa arise frequently during the years of airway infection experienced by patients with cystic fibrosis and bronchiectasis but are rare in the absence of chronic infection and structural lung disease. Since the onset of the COVID-19 pandemic, large numbers of patients have remained mechanically ventilated for extended periods of time. These patients are prone to acquire bacterial pathogens that persist for many weeks and have the opportunity to evolve within the pulmonary environment. However, little is known about what types of adaptations occur in these bacteria and whether these adaptations mimic those observed in chronic infections. We describe a COVID-19 patient with a secondary P. aeruginosa lung infection in whom the causative bacterium persisted for >50 days. Over the course of this infection, a hypermutator lineage of P. aeruginosa emerged and co-existed with a non-hypermutator lineage. Compared to the parental lineage, the hypermutator lineage evolved to be less cytotoxic and less virulent. Genomic analyses of the hypermutator lineage identified numerous mutations, including in the mismatch repair gene mutL and other genes frequently mutated in individuals with cystic fibrosis. Together, these findings demonstrate that hypermutator lineages can emerge when P. aeruginosa persists following acute infections such as ventilator-associated pneumonia and that these lineages have the potential to affect patient…

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