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Environmentally Endemic Pseudomonas aeruginosa Strains with Mutations in lasR Are Associated with Increased Disease Severity in Corneal Ulcers
The Steroids for Corneal Ulcers Trial (SCUT) was a multicenter, international study of bacterial keratitis in which 101 Pseudomonas aeruginosa infections were treated. Twenty-two of 101 P. aeruginosa isolates collected had a colony morphology characteristic of a loss-of-function mutation in lasR, th...
Autores principales: | , , , , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Society for Microbiology
2016
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5014915/ https://www.ncbi.nlm.nih.gov/pubmed/27631025 http://dx.doi.org/10.1128/mSphere.00140-16 |
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author | Hammond, John H. Hebert, Wesley P. Naimie, Amanda Ray, Kathryn Van Gelder, Rachel D. DiGiandomenico, Antonio Lalitha, Prajna Srinivasan, Muthiah Acharya, Nisha R. Lietman, Thomas Hogan, Deborah A. Zegans, Michael E. |
author_facet | Hammond, John H. Hebert, Wesley P. Naimie, Amanda Ray, Kathryn Van Gelder, Rachel D. DiGiandomenico, Antonio Lalitha, Prajna Srinivasan, Muthiah Acharya, Nisha R. Lietman, Thomas Hogan, Deborah A. Zegans, Michael E. |
author_sort | Hammond, John H. |
collection | PubMed |
description | The Steroids for Corneal Ulcers Trial (SCUT) was a multicenter, international study of bacterial keratitis in which 101 Pseudomonas aeruginosa infections were treated. Twenty-two of 101 P. aeruginosa isolates collected had a colony morphology characteristic of a loss-of-function mutation in lasR, the gene encoding a quorum-sensing master regulator. Ulcers caused by these 22 strains were associated with larger areas of corneal opacification, worse vision, and a lower rate of vision recovery in response to treatment than ulcers caused by the other isolates. The lasR sequences from these isolates each contained one of three nonsynonymous substitutions, and these strains were deficient in production of LasR-regulated protease and rhamnolipids. Replacement of lasR with either of the two most common lasR alleles from the SCUT isolates was sufficient to decrease protease and rhamnolipid production in PA14. Loss of LasR function is associated with increased production of CupA fimbriae, and the LasR-defective isolates exhibited higher production of CupA fimbriae than LasR-intact isolates. Strains with the same lasR mutation were of the same multilocus sequence type, suggesting that LasR-deficient, environmental P. aeruginosa strains were endemic to the area, and infections caused by these strains were associated with worse patient outcomes in the SCUT study. (This study has been registered at ClinicalTrials.gov under registration no. NCT00324168.) IMPORTANCE The LasR transcription factor is an important regulator of quorum sensing in P. aeruginosa and positively controls multiple virulence-associated pathways. The emergence of strains with lasR loss-of-function alleles in chronic disease is well described and is thought to represent a specific adaptation to the host environment. However, the prevalence and virulence of these strains in acute infections remain unclear. This report describes observations revealing that lasR mutants were common among isolates from a large, multicenter clinical study of keratitis and were associated with worse clinical outcomes than LasR-intact strains despite reduced production of LasR-regulated factors. Additionally, these lasR mutants were closely related strains or clones, as determined by molecular analysis. Because bacterial keratitis is community acquired, these data indicate infection by endemic, LasR-deficient strains in the environment. These results suggest that the conventional paradigm regarding the role for LasR-mediated regulation of virulence is more complex than previously appreciated. |
format | Online Article Text |
id | pubmed-5014915 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2016 |
publisher | American Society for Microbiology |
record_format | MEDLINE/PubMed |
spelling | pubmed-50149152016-09-14 Environmentally Endemic Pseudomonas aeruginosa Strains with Mutations in lasR Are Associated with Increased Disease Severity in Corneal Ulcers Hammond, John H. Hebert, Wesley P. Naimie, Amanda Ray, Kathryn Van Gelder, Rachel D. DiGiandomenico, Antonio Lalitha, Prajna Srinivasan, Muthiah Acharya, Nisha R. Lietman, Thomas Hogan, Deborah A. Zegans, Michael E. mSphere Research Article The Steroids for Corneal Ulcers Trial (SCUT) was a multicenter, international study of bacterial keratitis in which 101 Pseudomonas aeruginosa infections were treated. Twenty-two of 101 P. aeruginosa isolates collected had a colony morphology characteristic of a loss-of-function mutation in lasR, the gene encoding a quorum-sensing master regulator. Ulcers caused by these 22 strains were associated with larger areas of corneal opacification, worse vision, and a lower rate of vision recovery in response to treatment than ulcers caused by the other isolates. The lasR sequences from these isolates each contained one of three nonsynonymous substitutions, and these strains were deficient in production of LasR-regulated protease and rhamnolipids. Replacement of lasR with either of the two most common lasR alleles from the SCUT isolates was sufficient to decrease protease and rhamnolipid production in PA14. Loss of LasR function is associated with increased production of CupA fimbriae, and the LasR-defective isolates exhibited higher production of CupA fimbriae than LasR-intact isolates. Strains with the same lasR mutation were of the same multilocus sequence type, suggesting that LasR-deficient, environmental P. aeruginosa strains were endemic to the area, and infections caused by these strains were associated with worse patient outcomes in the SCUT study. (This study has been registered at ClinicalTrials.gov under registration no. NCT00324168.) IMPORTANCE The LasR transcription factor is an important regulator of quorum sensing in P. aeruginosa and positively controls multiple virulence-associated pathways. The emergence of strains with lasR loss-of-function alleles in chronic disease is well described and is thought to represent a specific adaptation to the host environment. However, the prevalence and virulence of these strains in acute infections remain unclear. This report describes observations revealing that lasR mutants were common among isolates from a large, multicenter clinical study of keratitis and were associated with worse clinical outcomes than LasR-intact strains despite reduced production of LasR-regulated factors. Additionally, these lasR mutants were closely related strains or clones, as determined by molecular analysis. Because bacterial keratitis is community acquired, these data indicate infection by endemic, LasR-deficient strains in the environment. These results suggest that the conventional paradigm regarding the role for LasR-mediated regulation of virulence is more complex than previously appreciated. American Society for Microbiology 2016-09-07 /pmc/articles/PMC5014915/ /pubmed/27631025 http://dx.doi.org/10.1128/mSphere.00140-16 Text en Copyright © 2016 Hammond et al. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license (http://creativecommons.org/licenses/by/4.0/) . |
spellingShingle | Research Article Hammond, John H. Hebert, Wesley P. Naimie, Amanda Ray, Kathryn Van Gelder, Rachel D. DiGiandomenico, Antonio Lalitha, Prajna Srinivasan, Muthiah Acharya, Nisha R. Lietman, Thomas Hogan, Deborah A. Zegans, Michael E. Environmentally Endemic Pseudomonas aeruginosa Strains with Mutations in lasR Are Associated with Increased Disease Severity in Corneal Ulcers |
title | Environmentally Endemic Pseudomonas aeruginosa Strains with Mutations in lasR Are Associated with Increased Disease Severity in Corneal Ulcers |
title_full | Environmentally Endemic Pseudomonas aeruginosa Strains with Mutations in lasR Are Associated with Increased Disease Severity in Corneal Ulcers |
title_fullStr | Environmentally Endemic Pseudomonas aeruginosa Strains with Mutations in lasR Are Associated with Increased Disease Severity in Corneal Ulcers |
title_full_unstemmed | Environmentally Endemic Pseudomonas aeruginosa Strains with Mutations in lasR Are Associated with Increased Disease Severity in Corneal Ulcers |
title_short | Environmentally Endemic Pseudomonas aeruginosa Strains with Mutations in lasR Are Associated with Increased Disease Severity in Corneal Ulcers |
title_sort | environmentally endemic pseudomonas aeruginosa strains with mutations in lasr are associated with increased disease severity in corneal ulcers |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5014915/ https://www.ncbi.nlm.nih.gov/pubmed/27631025 http://dx.doi.org/10.1128/mSphere.00140-16 |
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