AUTHOR=Ding Fengming , Han Lei , Xue Yishu , Yang Iris Tingshiuan , Fan Xinxin , Tang Rong , Zhang Chen , Zhu Miao , Tian Xue , Shao Ping , Zhang Min 

TITLE=Multidrug-resistant Pseudomonas aeruginosa is predisposed to lasR mutation through up-regulated activity of efflux pumps in non-cystic fibrosis bronchiectasis patients

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=12

YEAR=2022

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2022.934439

DOI=10.3389/fcimb.2022.934439

ISSN=2235-2988

ABSTRACT=<sec><title>Background</title><p>Multidrug-resistant (MDR) <italic>Pseudomonas aeruginosa</italic> is a frequent opportunistic pathogen that causes significant mortality in patients with non-cystic fibrosis bronchiectasis (NCFB). Although the quorum sensing (QS) system is a potential target for treatment, <italic>lasR</italic> mutants that present with a QS-deficient phenotype have been frequently reported among clinical <italic>P. aeruginosa</italic> isolates. We aimed to investigate whether antibiotic resistance would select for <italic>lasR</italic> mutants during chronic <italic>P. aeruginosa</italic> lung infection and determine the mechanism underlying the phenomenon.</p></sec><sec><title>Methods</title><p>We prospectively evaluated episodes of chronic <italic>P. aeruginosa</italic> lung infections in NCFB patients over a 2-year period at two centers of our institution. QS phenotypic assessments and whole-genome sequencing (WGS) of <italic>P. aeruginosa</italic> isolates were performed. Evolution experiments were conducted to confirm the emergence of <italic>lasR</italic> mutants in clinical MDR <italic>P. aeruginosa</italic> cultures.</p></sec><sec><title>Results</title><p>We analyzed episodes of <italic>P. aeruginosa</italic> infection among 97 NCFB patients and found only prior carbapenem exposure independently predictive of the isolation of MDR <italic>P. aeruginosa</italic> strains. Compared with non-MDR isolates, MDR isolates presented significantly QS-deficient phenotypes, which could not be complemented by the exogenous addition of 3OC12-HSL. The paired isolates showed that their QS-phenotype deficiency occurred after MDR was developed. Whole-genome sequencing analysis revealed that <italic>lasR</italic> nonsynonymous mutations were significantly more frequent in MDR isolates, and positive correlations of mutation frequencies were observed between genes of <italic>lasR</italic> and negative-efflux-pump regulators (<italic>nalC</italic> and <italic>mexZ</italic>). The addition of the efflux pump inhibitor PAβN could not only promote QS phenotypes of these MDR isolates but also delay the early emergence of <italic>lasR</italic> mutants in evolution experiments.</p></sec><sec><title>Conclusions</title><p>Our data indicated that MDR <italic>P. aeruginosa</italic> was predisposed to <italic>lasR</italic> mutation through the upregulated activity of efflux pumps. These findings suggest that anti-QS therapy combined with efflux pump inhibitors might be a potential strategy for NCFB patients in the challenge of MDR <italic>P. aeruginosa</italic> infections.</p></sec>