Chronic Infection With Pseudomonas aeruginosa in Cystic Fibrosis

Chronic infection of the cystic fibrosis (CF) airway by the opportunistic pathogen Pseudomonas aeruginosa is the leading cause of morbidity and mortality for adult CF patients. Prolonged infections are accompanied by adaptation of P. aeruginosa to the unique conditions of the CF lung environment, as well as marked diversification of the pathogen into phenotypically and genetically distinct strains that can coexist for years within a patient. Little is known, however, about the causes of this diversification and its impact on patient health. Here, we show experimentally that, consistent with ecological theory of diversification, the nutritional conditions of the CF airway can cause rapid and extensive diversification of P. aeruginosa. Mucin, the substance responsible for the increased viscosity associated with the thick mucus layer in the CF airway, had little impact on within-population diversification but did promote divergence among populations. Furthermore, in vitro evolution recapitulated traits thought to be hallmarks of chronic infection, including reduced motility and increased biofilm formation, and the range of phenotypes observed in a collection of clinical isolates. Our results suggest that nutritional complexity and reduced dispersal can drive evolutionary diversification of P. aeruginosa independent of other features of the CF lung such as an active immune system or the presence of competing microbial species. We suggest that diversification, by generating extensive phenotypic and genetic variation on which selection can act, may be a key first step in the development of chronic infections.

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Draft Genome Sequences of 63 Pseudomonas aeruginosa Isolates Recovered from Cystic Fibrosis Sputum: TABLE 1

Genome Announcements ◽

10.1128/genomea.00231-16 ◽

2016 ◽

Vol 4 (2) ◽

Cited By ~ 1

Author(s):

Theodore Spilker ◽

John J. LiPuma

Keyword(s):

Cystic Fibrosis ◽

Pseudomonas Aeruginosa ◽

Chronic Infection ◽

Bacterial Pathogens ◽

Care Center ◽

Draft Genome ◽

Genome Sequences ◽

Cystic Fibrosis Sputum ◽

Host Evolution

Here, we report the draft genome sequences of 63 Pseudomonas aeruginosa isolates, recovered in culture of sputum from 15 individuals with cystic fibrosis (CF) receiving care in a single CF care center over a 13-year period. These sequences add value to studies of within-host evolution of bacterial pathogens during chronic infection.

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Pseudomonas aeruginosa, mucoidy and the chronic infection phenotype in cystic fibrosis

Trends in Microbiology ◽

10.1016/s0966-842x(00)88974-x ◽

1995 ◽

Vol 3 (9) ◽

pp. 351-356 ◽

Cited By ~ 77

Author(s):

V. Deretic ◽

Michael J. Schurr ◽

Hongwei Yu

Keyword(s):

Cystic Fibrosis ◽

Pseudomonas Aeruginosa ◽

Chronic Infection

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Non-hierarchical, RhlR-regulated acyl-homoserine lactone quorum sensing in a cystic fibrosis isolate of Pseudomonas aeruginosa

10.1101/755314 ◽

2019 ◽

Author(s):

Renae L. Cruz ◽

Kyle L. Asfahl ◽

Sara Van den Bossche ◽

Tom Coenye ◽

Aurélie Crabbé ◽

...

Keyword(s):

Cystic Fibrosis ◽

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Virulence Factors ◽

Chronic Infection ◽

Cell Model ◽

Lung Epithelium ◽

Independent Manner ◽

Epithelium Cell ◽

Regulated Gene Expression

ABSTRACTThe opportunistic pathogen Pseudomonas aeruginosa is a leading cause of airway infection in cystic fibrosis (CF) patients. P. aeruginosa employs several hierarchically arranged and interconnected quorum sensing (QS) regulatory circuits to produce a battery of virulence factors such as elastase, phenazines, and rhamnolipids. The QS transcription factor LasR sits atop this hierarchy, and activates the transcription of dozens of genes, including that encoding the QS regulator RhlR. Paradoxically, inactivating lasR mutations are frequently observed in isolates from CF patients with chronic P. aeruginosa infections. In contrast, mutations in rhlR are rare. We have recently shown that in CF isolates, the QS circuitry is often “rewired” such that RhlR acts in a LasR-independent manner. To begin understanding how QS activity differs in this “rewired” background, we characterized QS activation and RhlR-regulated gene expression in P. aeruginosa E90, a LasR-null, RhlR-active chronic infection isolate. In this isolate, RhlR activates the expression of 53 genes in response to increasing cell density. The genes regulated by RhlR include several that encode virulence factors. Some, but not all, of these genes are present in the QS regulon described in the well-studied laboratory strain PAO1. We also demonstrate that E90 produces virulence factors at similar concentrations to that of PAO1. Unlike PAO1, cytotoxicity by E90 in a three-dimensional lung epithelium cell model is also RhlR-regulated. These data illuminate a “rewired” LasR-independent RhlR regulon in chronic infection isolates and suggest that RhlR may be a target for therapeutic development in chronic infections.AUTHOR SUMMARYPseudomonas aeruginosa is a prominent cystic fibrosis (CF) pathogen that uses quorum sensing (QS) to regulate virulence. In laboratory strains, the key QS regulator is LasR. Some isolates from patients with chronic CF infections appear to use an alternate QS circuitry in which another transcriptional regulator, RhlR, mediates QS. We show that a LasR-null CF clinical isolate engages in QS through RhlR and remains capable of inducing cell death in an in vivo-like lung epithelium cell model. Our findings support the notion that LasR-null clinical isolates can engage in RhlR QS and highlight the centrality of RhlR gene regulation in chronic P. aeruginosa infections.

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Evaluation of Inhaled Tobramycin in Early Eradication of Pseudomonas aeruginosa in Infants With Cystic Fibrosis

The Journal of Pediatric Pharmacology and Therapeutics ◽

10.5863/1551-6776-25.8.709 ◽

2020 ◽

Vol 25 (8) ◽

pp. 709-716

Author(s):

Jane Choi ◽

Kimberly Novak ◽

Rohan Thompson

Keyword(s):

Cystic Fibrosis ◽

Pseudomonas Aeruginosa ◽

Chronic Infection ◽

Primary Outcome ◽

Efficacy And Safety ◽

Limited Data ◽

Pseudomonas Aeruginosa Infection ◽

Secondary Outcomes ◽

Safety Assessments ◽

First Time

OBJECTIVE Early antibiotic therapy has the potential to eradicate initial Pseudomonas aeruginosa infection and postpone chronic infection. There are limited data evaluating the efficacy and safety of inhaled tobramycin in patients with cystic fibrosis (CF) who are younger than 1 year. The objective of this study was to evaluate the effectiveness of inhaled tobramycin in early eradication of P aeruginosa in infants with CF. METHODS This retrospective study evaluated patients with CF younger than 1 year with first time infection with P aeruginosa. The primary outcome was the frequency of P aeruginosa eradication. Secondary outcomes were sustained culture negativity at 12 and 18 months and safety assessments. RESULTS Of 18 patients included in the study, 9 received inhaled tobramycin and an enteral fluoroquinolone and 9 received inhaled tobramycin alone. Microbiologic clearance of respiratory cultures was observed in 83% patients at end of therapy and 78% of patients at 1 month posttherapy. Eradication of P aeruginosa was observed in 56% of patients at 6 months posttreatment with sustained culture negativity observed in 39% of patients up to 18 months. CONCLUSIONS Inhaled-tobramycin therapy is effective in early eradication of P aeruginosa infection and is well tolerated in infants younger than 1 year.

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RhlR-Regulated Acyl-Homoserine Lactone Quorum Sensing in a Cystic Fibrosis Isolate of Pseudomonas aeruginosa

mBio ◽

10.1128/mbio.00532-20 ◽

2020 ◽

Vol 11 (2) ◽

Cited By ~ 4

Author(s):

Renae L. Cruz ◽

Kyle L. Asfahl ◽

Sara Van den Bossche ◽

Tom Coenye ◽

Aurélie Crabbé ◽

...

Keyword(s):

Cystic Fibrosis ◽

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Virulence Factors ◽

Chronic Infection ◽

Cell Model ◽

Lung Epithelium ◽

Content Type ◽

Epithelium Cell ◽

Regulated Gene Expression

ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa is a leading cause of airway infection in cystic fibrosis (CF) patients. P. aeruginosa employs several hierarchically arranged and interconnected quorum sensing (QS) regulatory circuits to produce a battery of virulence factors such as elastase, phenazines, and rhamnolipids. The QS transcription factor LasR sits atop this hierarchy and activates the transcription of dozens of genes, including that encoding the QS regulator RhlR. Paradoxically, inactivating lasR mutations are frequently observed in isolates from CF patients with chronic P. aeruginosa infections. In contrast, mutations in rhlR are rare. We have recently shown that in CF isolates, the QS circuitry is often rewired such that RhlR acts in a LasR-independent manner. To begin understanding how QS activity differs in this rewired background, we characterized QS activation and RhlR-regulated gene expression in P. aeruginosa E90, a LasR-null, RhlR-active chronic infection isolate. In this isolate, RhlR activates the expression of 53 genes in response to increasing cell density. The genes regulated by RhlR include several that encode virulence factors. Some, but not all, of these genes are present in the QS regulon described in the well-studied laboratory strain PAO1. We also demonstrate that E90 produces virulence factors at similar concentrations as PAO1, and in E90, RhlR plays a significant role in mediating cytotoxicity in a three-dimensional lung epithelium cell model. These data illuminate a rewired LasR-independent RhlR regulon in chronic infection isolates and suggest further investigation of RhlR as a possible target for therapeutic development in chronic infections. IMPORTANCE Pseudomonas aeruginosa is a prominent cystic fibrosis (CF) pathogen that uses quorum sensing (QS) to regulate virulence. In laboratory strains, the key QS regulator is LasR. Many isolates from patients with chronic CF infections appear to use an alternate QS circuitry in which another transcriptional regulator, RhlR, mediates QS. We show that a LasR-null CF clinical isolate engages in QS through RhlR and remains capable of inducing cell death in an in vivo-like lung epithelium cell model. Our findings support the notion that LasR-null clinical isolates can engage in RhlR QS and highlight the centrality of RhlR in chronic P. aeruginosa infections.

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Evolutionary Genomics of Niche-Specific Adaptation to the Cystic Fibrosis Lung in Pseudomonas aeruginosa

Molecular Biology and Evolution ◽

10.1093/molbev/msaa226 ◽

2020 ◽

Author(s):

Jeremy R Dettman ◽

Rees Kassen

Keyword(s):

Cystic Fibrosis ◽

Pseudomonas Aeruginosa ◽

Positive Selection ◽

Chronic Infection ◽

Iron Homeostasis ◽

Acute Infection ◽

Whole Genome Sequence ◽

Chronic Infections ◽

Environmental Strain ◽

Single Strain

Abstract The comparative genomics of the transition of the opportunistic pathogen Pseudomonas aeruginosa from a free-living environmental strain to one that causes chronic infection in the airways of cystic fibrosis (CF) patients remain poorly studied. Chronic infections are thought to originate from colonization by a single strain sampled from a diverse, globally distributed population, followed by adaptive evolution to the novel, stressful conditions of the CF lung. However, we do not know whether certain clades are more likely to form chronic infections than others and we lack a comprehensive view of the suite of genes under positive selection in the CF lung. We analyzed whole-genome sequence data from 1,000 P. aeruginosa strains with diverse ecological provenances including the CF lung. CF isolates were distributed across the phylogeny, indicating little genetic predisposition for any one clade to cause chronic infection. Isolates from the CF niche experienced stronger positive selection on core genes than those derived from environmental or acute infection sources, consistent with recent adaptation to the lung environment. Genes with the greatest differential positive selection in the CF niche include those involved in core cellular processes such as metabolism, energy production, and stress response as well as those linked to patho-adaptive processes such as antibiotic resistance, cell wall and membrane modification, quorum sensing, biofilms, mucoidy, motility, and iron homeostasis. Many genes under CF-specific differential positive selection had regulatory functions, consistent with the idea that regulatory mutations play an important role in rapid adaptation to novel environments.

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