AUTHOR=Shanks Robert M. Q. , Atta Sarah , Stella Nicholas A. , Sundar-Raj Chollapadi V. , Romanowski John E. , Grewal Arman S. , Shanks Hazel Q. , Mumper Sonya M. , Dhaliwal Deepinder K. , Mammen Alex , Callaghan Jake D. , Calvario Rachel C. , Romanowski Eric G. , Kowalski Regis P. , Zegans Michael E. , Jhanji Vishal 

TITLE=A rise in the frequency of lasR mutant Pseudomonas aeruginosa among keratitis isolates between 1993 and 2021

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2023.1286842

DOI=10.3389/fcimb.2023.1286842

ISSN=2235-2988

ABSTRACT=<sec><title>Introduction</title><p><italic>Pseudomonas aeruginosa</italic> causes vision threatening keratitis. The <italic>LasR</italic> transcription factor regulates virulence factors in response to the quorum sensing molecule N-3-oxo-dodecanoyl-L-homoserine lactone. <italic>P. aeruginosa</italic> isolates with <italic>lasR</italic> mutations are characterized by an iridescent high sheen phenotype caused by a build-up of 2-heptyl-4-quinolone. A previous study demonstrated 22% (n=101) of <italic>P. aeruginosa</italic> keratitis isolates from India between 2010 and 2016 were sheen positive <italic>lasR</italic> mutants, and the sheen phenotype correlated with worse clinical outcomes for patients. In this study, a longitudinal collection of <italic>P. aeruginosa</italic> keratitis isolates from Eastern North America were screened for <italic>lasR</italic> mutations by the sheen phenotype and sequencing of the <italic>lasR</italic> gene.</p></sec><sec><title>Methods</title><p>Keratitis isolates (n=399) were classified by sheen phenotype. The <italic>lasR</italic> gene was cloned from a subset of isolates, sequenced, and tested for loss of function or dominant-negative status based on an azocasein protease assay. A retrospective chart review compared outcomes of keratitis patients infected by sheen positive and negative isolates.</p></sec><sec><title>Results</title><p>A significant increase in sheen positive isolates was observed between 1993 and 2021. Extracellular protease activity was reduced among the sheen positive isolates and a defined <italic>lasR</italic> mutant. Cloned <italic>lasR</italic> alleles from the sheen positive isolates were loss of function or dominant negative and differed in sequence from previously reported ocular <italic>lasR</italic> mutant alleles. Retrospective analysis of patient information suggested significantly better visual outcomes for patients infected by sheen positive isolates.</p></sec><sec><title>Discussion</title><p>These results indicate an increase in <italic>lasR</italic> mutations among keratitis isolates in the United States and suggest that endemic <italic>lasR</italic> mutants can cause keratitis.</p></sec>