Phage Inhibit Pathogen Dissemination by Targeting Bacterial Migrants in a Chronic Infection Model

ABSTRACT The microbial communities inhabiting chronic infections are often composed of spatially organized micrometer-sized, highly dense aggregates. It has recently been hypothesized that aggregates are responsible for the high tolerance of chronic infections to host immune functions and antimicrob...

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Autores principales:	Sophie E. Darch, Kasper N. Kragh, Evelyn A. Abbott, Thomas Bjarnsholt, James J. Bull, Marvin Whiteley
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2017
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/b61446f38f17452bbbd9665af5fb0f65
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spelling	oai:doaj.org-article:b61446f38f17452bbbd9665af5fb0f652021-11-15T15:50:59ZPhage Inhibit Pathogen Dissemination by Targeting Bacterial Migrants in a Chronic Infection Model10.1128/mBio.00240-172150-7511https://doaj.org/article/b61446f38f17452bbbd9665af5fb0f652017-05-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00240-17https://doaj.org/toc/2150-7511ABSTRACT The microbial communities inhabiting chronic infections are often composed of spatially organized micrometer-sized, highly dense aggregates. It has recently been hypothesized that aggregates are responsible for the high tolerance of chronic infections to host immune functions and antimicrobial therapies. Little is currently known regarding the mechanisms controlling aggregate formation and antimicrobial tolerance primarily because of the lack of robust, biologically relevant experimental systems that promote natural aggregate formation. Here, we developed an in vitro model based on chronic Pseudomonas aeruginosa infection of the cystic fibrosis (CF) lung. This model utilizes a synthetic sputum medium that readily promotes the formation of P. aeruginosa aggregates with sizes similar to those observed in human CF lung tissue. Using high-resolution imaging, we exploited this model to elucidate the life history of P. aeruginosa and the mechanisms that this bacterium utilizes to tolerate antimicrobials, specifically, bacteriophage. In the early stages of growth in synthetic sputum, planktonic cells form aggregates that increase in size over time by expansion. In later growth, migrant cells disperse from aggregates and colonize new areas, seeding new aggregates. When added simultaneously with phage, P. aeruginosa was readily killed and aggregates were unable to form. When added after initial aggregate formation, phage were unable to eliminate all of the aggregates because of exopolysaccharide production; however, seeding of new aggregates by dispersed migrants was inhibited. We propose a model in which aggregates provide a mechanism that allows P. aeruginosa to tolerate phage therapy during chronic infection without the need for genetic mutation. IMPORTANCE Bacteria in chronic infections often reside in communities composed of micrometer-sized, highly dense aggregates. A primary challenge for studying aggregates has been the lack of laboratory systems that promote natural aggregate formation in relevant environments. Here, we developed a growth medium that mimics chronic lung infection and promotes natural aggregate formation by the bacterium Pseudomonas aeruginosa. High-resolution, single-cell microscopy allowed us to characterize P. aeruginosa’s life history—seeding, aggregate formation, and dispersal—in this medium. Our results reveal that this bacterium readily forms aggregates that release migrants to colonize new areas. We also show that aggregates allow P. aeruginosa to tolerate therapeutic bacteriophage addition, although this treatment limits P. aeruginosa dissemination by targeting migrants.Sophie E. DarchKasper N. KraghEvelyn A. AbbottThomas BjarnsholtJames J. BullMarvin WhiteleyAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 8, Iss 2 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Sophie E. Darch Kasper N. Kragh Evelyn A. Abbott Thomas Bjarnsholt James J. Bull Marvin Whiteley Phage Inhibit Pathogen Dissemination by Targeting Bacterial Migrants in a Chronic Infection Model
description	ABSTRACT The microbial communities inhabiting chronic infections are often composed of spatially organized micrometer-sized, highly dense aggregates. It has recently been hypothesized that aggregates are responsible for the high tolerance of chronic infections to host immune functions and antimicrobial therapies. Little is currently known regarding the mechanisms controlling aggregate formation and antimicrobial tolerance primarily because of the lack of robust, biologically relevant experimental systems that promote natural aggregate formation. Here, we developed an in vitro model based on chronic Pseudomonas aeruginosa infection of the cystic fibrosis (CF) lung. This model utilizes a synthetic sputum medium that readily promotes the formation of P. aeruginosa aggregates with sizes similar to those observed in human CF lung tissue. Using high-resolution imaging, we exploited this model to elucidate the life history of P. aeruginosa and the mechanisms that this bacterium utilizes to tolerate antimicrobials, specifically, bacteriophage. In the early stages of growth in synthetic sputum, planktonic cells form aggregates that increase in size over time by expansion. In later growth, migrant cells disperse from aggregates and colonize new areas, seeding new aggregates. When added simultaneously with phage, P. aeruginosa was readily killed and aggregates were unable to form. When added after initial aggregate formation, phage were unable to eliminate all of the aggregates because of exopolysaccharide production; however, seeding of new aggregates by dispersed migrants was inhibited. We propose a model in which aggregates provide a mechanism that allows P. aeruginosa to tolerate phage therapy during chronic infection without the need for genetic mutation. IMPORTANCE Bacteria in chronic infections often reside in communities composed of micrometer-sized, highly dense aggregates. A primary challenge for studying aggregates has been the lack of laboratory systems that promote natural aggregate formation in relevant environments. Here, we developed a growth medium that mimics chronic lung infection and promotes natural aggregate formation by the bacterium Pseudomonas aeruginosa. High-resolution, single-cell microscopy allowed us to characterize P. aeruginosa’s life history—seeding, aggregate formation, and dispersal—in this medium. Our results reveal that this bacterium readily forms aggregates that release migrants to colonize new areas. We also show that aggregates allow P. aeruginosa to tolerate therapeutic bacteriophage addition, although this treatment limits P. aeruginosa dissemination by targeting migrants.
format	article
author	Sophie E. Darch Kasper N. Kragh Evelyn A. Abbott Thomas Bjarnsholt James J. Bull Marvin Whiteley
author_facet	Sophie E. Darch Kasper N. Kragh Evelyn A. Abbott Thomas Bjarnsholt James J. Bull Marvin Whiteley
author_sort	Sophie E. Darch
title	Phage Inhibit Pathogen Dissemination by Targeting Bacterial Migrants in a Chronic Infection Model
title_short	Phage Inhibit Pathogen Dissemination by Targeting Bacterial Migrants in a Chronic Infection Model
title_full	Phage Inhibit Pathogen Dissemination by Targeting Bacterial Migrants in a Chronic Infection Model
title_fullStr	Phage Inhibit Pathogen Dissemination by Targeting Bacterial Migrants in a Chronic Infection Model
title_full_unstemmed	Phage Inhibit Pathogen Dissemination by Targeting Bacterial Migrants in a Chronic Infection Model
title_sort	phage inhibit pathogen dissemination by targeting bacterial migrants in a chronic infection model
publisher	American Society for Microbiology
publishDate	2017
url	https://doaj.org/article/b61446f38f17452bbbd9665af5fb0f65
work_keys_str_mv	AT sophieedarch phageinhibitpathogendisseminationbytargetingbacterialmigrantsinachronicinfectionmodel AT kaspernkragh phageinhibitpathogendisseminationbytargetingbacterialmigrantsinachronicinfectionmodel AT evelynaabbott phageinhibitpathogendisseminationbytargetingbacterialmigrantsinachronicinfectionmodel AT thomasbjarnsholt phageinhibitpathogendisseminationbytargetingbacterialmigrantsinachronicinfectionmodel AT jamesjbull phageinhibitpathogendisseminationbytargetingbacterialmigrantsinachronicinfectionmodel AT marvinwhiteley phageinhibitpathogendisseminationbytargetingbacterialmigrantsinachronicinfectionmodel
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Phage Inhibit Pathogen Dissemination by Targeting Bacterial Migrants in a Chronic Infection Model

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