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Reuven AD, Mwaura BW, Bliska JB. ExoS Effector in Pseudomonas aeruginosa Hyperactive Type III Secretion System Mutant Promotes Enhanced Plasma Membrane Rupture in Neutrophils. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.24.577040. [PMID: 38328038 PMCID: PMC10849719 DOI: 10.1101/2024.01.24.577040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Pseudomonas aeruginosa is an opportunistic bacterial pathogen responsible for a large percentage of airway infections that cause morbidity and mortality in immunocompromised patients, especially those with cystic fibrosis (CF). One important P. aeruginosa virulence factor is a type III secretion system (T3SS) that translocates effectors into host cells. ExoS is a T3SS effector with ADP ribosyltransferase (ADPRT) activity. The ADPRT activity of ExoS promotes P. aeruginosa virulence by inhibiting phagocytosis and limiting the oxidative burst in neutrophils. The P. aeruginosa T3SS also translocates flagellin, which can activate the NLRC4 inflammasome, resulting in: 1) gasdermin-D (GSDMD) pores, release of IL-1β and pyroptosis; and 2) histone 3 citrullination (CitH3) and decondensation and expansion of nuclear DNA into the cytosol. However, recent studies with the P. aeruginosa laboratory strain PAO1 indicate that ExoS ADPRT activity inhibits activation of the NLRC4 inflammasome in neutrophils. Here, an ExoS+ CF clinical isolate of P. aeruginosa with a hyperactive T3SS was identified. Variants of the hyperactive T3SS mutant or PAO1 were used to infect neutrophils from C57BL/6 mice or mice engineered to have a CF genotype or a defect in inflammasome assembly. Responses to NLRC4 inflammasome assembly or ExoS ADPRT activity were assayed, results of which were found to be similar for C57BL/6 or CF neutrophils. The hyperactive T3SS mutant had enhanced resistance to neutrophil killing, like previously identified hypervirulent P. aeruginosa isolates. ExoS ADPRT activity in the hyperactive T3SS mutant regulated inflammasome and nuclear DNA decondensation responses like PAO1 but promoted enhanced CitH3 and plasma membrane rupture (PMR). Glycine supplementation inhibited PMR caused by the hyperactive T3SS mutant, suggesting ninjurin-1 is required for this process. These results identify enhanced neutrophil PMR as a pathogenic activity of ExoS ADPRT in a hypervirulent P. aeruginosa isolate.
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Affiliation(s)
- Arianna D. Reuven
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH, USA
| | - Bethany W. Mwaura
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH, USA
| | - James B. Bliska
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH, USA
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Raghuram V, Gunoskey JJ, Hofstetter KS, Jacko NF, Shumaker MJ, Hu YJ, Read TD, David MZ. Comparison of genomic diversity between single and pooled Staphylococcus aureus colonies isolated from human colonization cultures. Microb Genom 2023; 9:001111. [PMID: 37934072 PMCID: PMC10711313 DOI: 10.1099/mgen.0.001111] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 09/21/2023] [Indexed: 11/08/2023] Open
Abstract
The most common approach to sampling the bacterial populations within an infected or colonized host is to sequence genomes from a single colony obtained from a culture plate. However, it is recognized that this method does not capture the genetic diversity in the population. Sequencing a mixture of several colonies (pool-seq) is a better approach to detect population heterogeneity, but it is more complex to analyse due to different types of heterogeneity, such as within-clone polymorphisms, multi-strain mixtures, multi-species mixtures and contamination. Here, we compared 8 single-colony isolates (singles) and pool-seq on a set of 2286 Staphylococcus aureus culture samples to identify features that can distinguish pure samples, samples undergoing intraclonal variation and mixed strain samples. The samples were obtained by swabbing 3 body sites on 85 human participants quarterly for a year, who initially presented with a methicillin-resistant S. aureus skin and soft-tissue infection (SSTI). We compared parameters such as sequence quality, contamination, allele frequency, nucleotide diversity and pangenome diversity in each pool to those for the corresponding singles. Comparing singles from the same culture plate, we found that 18% of sample collections contained mixtures of multiple multilocus sequence types (MLSTs or STs). We showed that pool-seq data alone could predict the presence of multi-ST populations with 95% accuracy. We also showed that pool-seq could be used to estimate the number of intra-clonal polymorphic sites in the population. Additionally, we found that the pool may contain clinically relevant genes such as antimicrobial resistance markers that may be missed when only examining singles. These results highlight the potential advantage of analysing genome sequences of total populations obtained from clinical cultures rather than single colonies.
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Affiliation(s)
- Vishnu Raghuram
- Microbiology and Molecular Genetics Program, Graduate Division of Biological and Biomedical Sciences, Laney Graduate School, Emory University, Atlanta, Georgia, USA
| | - Jessica J. Gunoskey
- Division of Infectious Diseases, Department of Medicine, University of Pennsylvania, Philadelphia, USA
| | - Katrina S. Hofstetter
- Division of Infectious Diseases, Department of Medicine, Emory University, Atlanta, Georgia, USA
| | - Natasia F. Jacko
- Division of Infectious Diseases, Department of Medicine, University of Pennsylvania, Philadelphia, USA
| | - Margot J. Shumaker
- Division of Infectious Diseases, Department of Medicine, University of Pennsylvania, Philadelphia, USA
| | - Yi-Juan Hu
- Department of Biostatistics and Bioinformatics, Emory University, Atlanta, Georgia, USA
| | - Timothy D. Read
- Division of Infectious Diseases, Department of Medicine, Emory University, Atlanta, Georgia, USA
| | - Michael Z. David
- Division of Infectious Diseases, Department of Medicine, University of Pennsylvania, Philadelphia, USA
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Raghuram V, Gunoskey JJ, Hofstetter KS, Jacko NF, Shumaker MJ, Hu YJ, Read TD, David MZ. Comparison of genomic diversity between single and pooled Staphylococcus aureus colonies isolated from human colonisation cultures. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.14.544959. [PMID: 37397999 PMCID: PMC10312683 DOI: 10.1101/2023.06.14.544959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
The most common approach to sampling the bacterial populations within an infected or colonised host is to sequence genomes from a single colony obtained from a culture plate. However, it is recognized that this method does not capture the genetic diversity in the population. An alternative is to sequence a mixture containing multiple colonies ("pool-seq"), but this has the disadvantage that it is a non-homogeneous sample, making it difficult to perform specific experiments. We compared differences in measures of genetic diversity between eight single-colony isolates (singles) and pool-seq on a set of 2286 S. aureus culture samples. The samples were obtained by swabbing three body sites on 85 human participants quarterly for a year, who initially presented with a methicillin-resistant S. aureus skin and soft-tissue infection (SSTI). We compared parameters such as sequence quality, contamination, allele frequency, nucleotide diversity and pangenome diversity in each pool to the corresponding singles. Comparing singles from the same culture plate, we found that 18% of sample collections contained mixtures of multiple Multilocus sequence types (MLSTs or STs). We showed that pool-seq data alone could predict the presence of multi-ST populations with 95% accuracy. We also showed that pool-seq could be used to estimate the number of polymorphic sites in the population. Additionally, we found that the pool may contain clinically relevant genes such as antimicrobial resistance markers that may be missed when only examining singles. These results highlight the potential advantage of analysing genome sequences of total populations obtained from clinical cultures rather than single colonies.
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Affiliation(s)
- Vishnu Raghuram
- Microbiology and Molecular Genetics Program, Graduate Division of Biological and Biomedical Sciences, Laney Graduate School, Emory University, Atlanta, Georgia, USA
| | - Jessica J. Gunoskey
- Division of Infectious Diseases, Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Katrina S. Hofstetter
- Division of Infectious Diseases, Department of Medicine, Emory University, Atlanta, Georgia, USA
| | - Natasia F. Jacko
- Division of Infectious Diseases, Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Margot J. Shumaker
- Division of Infectious Diseases, Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Yi-Juan Hu
- Department of Biostatistics and Bioinformatics, Emory University, Atlanta, Georgia, USA
| | - Timothy D. Read
- Division of Infectious Diseases, Department of Medicine, Emory University, Atlanta, Georgia, USA
| | - Michael Z. David
- Division of Infectious Diseases, Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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Cramer N, Klockgether J, Tümmler B. Microevolution of Pseudomonas aeruginosa in the airways of people with cystic fibrosis. Curr Opin Immunol 2023; 83:102328. [PMID: 37116385 DOI: 10.1016/j.coi.2023.102328] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 03/26/2023] [Accepted: 03/27/2023] [Indexed: 04/30/2023]
Abstract
The chronic infections of cystic fibrosis (CF) airways with Pseudomonas aeruginosa are a paradigm of how environmental bacteria can conquer, adapt, and persist in an atypical habitat and successfully evade defense mechanisms and chemotherapy in a susceptible host. The within-host evolution of intraclonal diversity has been examined by whole-genome sequencing, phenotyping, and competitive fitness experiments of serial P. aeruginosa isolates collected from CF airways since onset of colonization for a period of up to 40 years. The spectrum of de novo mutations and the adaptation of phenotype and fitness of the bacterial progeny were more influenced by the living conditions in the CF lung than by the clone type of their ancestor and its genetic repertoire.
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Affiliation(s)
- Nina Cramer
- Department of Pediatric Pneumology, Allergology and Neonatology, Hannover Medical School, D-30625 Hannover, Germany
| | - Jens Klockgether
- Department of Pediatric Pneumology, Allergology and Neonatology, Hannover Medical School, D-30625 Hannover, Germany
| | - Burkhard Tümmler
- Department of Pediatric Pneumology, Allergology and Neonatology, Hannover Medical School, D-30625 Hannover, Germany; Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Center for Lung Research (DZL), Hannover, Germany.
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Cameron DR, Pitton M, Oberhaensli S, Schlegel K, Prod’hom G, Blanc DS, Jakob SM, Que YA. Parallel Evolution of Pseudomonas aeruginosa during a Prolonged ICU-Infection Outbreak. Microbiol Spectr 2022; 10:e0274322. [PMID: 36342287 PMCID: PMC9769503 DOI: 10.1128/spectrum.02743-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 10/19/2022] [Indexed: 11/09/2022] Open
Abstract
Most knowledge about Pseudomonas aeruginosa pathoadaptation is derived from studies on airway colonization in cystic fibrosis; little is known about adaptation in acute settings. P. aeruginosa frequently affects burned patients and the burn wound niche has distinct properties that likely influence pathoadaptation. This study aimed to genetically and phenotypically characterize P. aeruginosa isolates collected during an outbreak of infection in a burn intensive care unit (ICU). Sequencing reads from 58 isolates of ST1076 P. aeruginosa taken from 23 patients were independently mapped to a complete reference genome for the lineage (H25338); genetic differences were identified and were used to define the population structure. Comparative genomic analysis at single-nucleotide resolution identified pathoadaptive genes that evolved multiple, independent mutations. Three key phenotypic assays (growth performance, motility, carbapenem resistance) were performed to complement the genetic analysis for 47 unique isolates. Population structure for the ST1076 lineage revealed 11 evolutionary sublineages. Fifteen pathoadaptive genes evolved mutations in at least two sublineages. The most prominent functional classes affected were transcription/two-component regulatory systems, and chemotaxis/motility and attachment. The most frequently mutated gene was oprD, which codes for outer membrane porin involved in uptake of carbapenems. Reduced growth performance and motility were found to be adaptive phenotypic traits, as was high level of carbapenem resistance, which correlated with higher carbapenem consumption during the outbreak. Multiple prominent linages evolved each of the three traits in parallel providing evidence that they afford a fitness advantage for P. aeruginosa in the context of human burn infection. IMPORTANCE Pseudomonas aeruginosa is a Gram-negative pathogen causing infections in acutely burned patients. The precise mechanisms required for the establishment of infection in the burn setting, and adaptive traits underpinning prolonged outbreaks are not known. We have assessed genotypic data from 58 independent P. aeruginosa isolates taken from a single lineage that was responsible for an outbreak of infection in a burn ICU that lasted for almost 2.5 years and affected 23 patients. We identified a core set of 15 genes that we predict to control pathoadaptive traits in the burn infection based on the frequency with which independent mutations evolved. We combined the genotypic data with phenotypic data (growth performance, motility, antibiotic resistance) and clinical data (antibiotic consumption) to identify adaptive phenotypes that emerged in parallel. High-level carbapenem resistance evolved rapidly, and frequently, in response to high clinical demand for this antibiotic class during the outbreak.
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Affiliation(s)
- David R. Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Melissa Pitton
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences (GCB), University of Bern, Bern, Switzerland
| | - Simone Oberhaensli
- Interfaculty Bioinformatics Unit and SIB Swiss Institute of Bioinformatics, University of Bern, Bern, Switzerland
| | - Katja Schlegel
- Institute of Psychology, University of Bern, Bern, Switzerland
| | - Guy Prod’hom
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Dominique S. Blanc
- Service of Hospital Preventive Medicine, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Stephan M. Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Yok-Ai Que
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Chronic Bronchial Infection Is Associated with More Rapid Lung Function Decline in Chronic Obstructive Pulmonary Disease. Ann Am Thorac Soc 2022; 19:1842-1847. [PMID: 35666811 DOI: 10.1513/annalsats.202108-974oc] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Rationale: Some patients with chronic obstructive pulmonary disease (COPD) suffer accelerated lung function (forced expiratory volume in 1 second [FEV1]) decline over time. Objectives: To investigate the relationship between chronic bronchial infection (CBI) and, in particular, the isolation of Pseudomonas aeruginosa (PA), and FEV1 decline in COPD. Methods: Post-hoc analysis of a prospective cohort of 201 patients with COPD followed up every 3-6 months for 84 months. CBI was defined as ⩾3 sputum positive cultures of the same pathogenic micro-organism (PPM) over 1 year. Patients were stratified according to the presence of CBI by any PPM, as well by a single or multiple isolation of PA during follow-up. An adjusted mixed-effects linear regression model was used to investigate the independent effects of CBI and PA isolation on FEV1 decline over time. Results: During follow-up, PPMs were never isolated in 43.3% of patients, in 23.9% of them PPMs were isolated once, and CBI by any PPM was confirmed in 32.8% of participants. FEV1 decline in the entire cohort was 33.7 (95% confidence interval [CI], 21.4-46.1) ml/year. This was significantly increased in patients with CBI by any PPM (57.1 [95% CI, 28.5-79.3] ml/year) and in those in whom PA was isolated at least once (48.5 [95% CI, 27.3-88.2] ml/year). Multivariable analysis showed that the presence of both CBI by any PPM, and at least one PA isolation, were independent factors associated with faster FEV1 decline adjusted by baseline FEV1, presence of bronchiectasis, body mass index, age, exacerbations, smoking status, symptoms, baseline treatment, and comorbidities. Conclusions: The presence of CBI by any PPM, and one or more PA isolation, were independently associated with FEV1 decline in patients with COPD.
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Carter SC, Franciosi AN, O’Shea KM, O’Carroll OM, Sharma A, Bell A, Keogan B, O’Reilly P, Coughlan S, Law SM, Gray RD, Hisert KB, Singh PK, Cooke G, Grogan B, De Gascun CF, Gallagher CG, Nicholson TT, Quon BS, McKone EF. Acute Pulmonary Exacerbation Phenotypes in Patients with Cystic Fibrosis. Ann Am Thorac Soc 2022; 19:1818-1826. [PMID: 35713619 PMCID: PMC9667812 DOI: 10.1513/annalsats.202111-1266oc] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Rationale: The etiology of cystic fibrosis (CF) pulmonary exacerbations (PEx) is likely multifactorial with viral, bacterial, and non-infectious pathways contributing. Objectives: To determine whether viral infection status and CRP (C-reactive protein) can classify subphenotypes of PEx that differ in outcomes and biomarker profiles. Methods: Patients were recruited at time of admission for a PEx. Nasal swabs and sputum samples were collected and processed using the respiratory panel of the FilmArray multiplex polymerase chain reaction (PCR). Serum and plasma biomarkers were measured. PEx were classified using serum CRP and viral PCR: "pauci-inflammatory" if CRP < 5 mg/L, "non-viral with systemic inflammation" if CRP ⩾ 5 mg/L and no viral infection detected by PCR and "viral with systemic inflammation" if CRP ⩾ 5 mg/L and viral infection detected by PCR. Results: Discovery cohort (n = 59) subphenotype frequencies were 1) pauci-inflammatory (37%); 2) non-viral with systemic inflammation (41%); and 3) viral with systemic inflammation (22%). Immunoglobulin G, immunoglobulin M, interleukin-10, interleukin-13, serum calprotectin, and CRP levels differed across phenotypes. Reduction from baseline in forced expiratory volume in 1 second as percent predicted (FEV1pp) at onset of exacerbation differed between non-viral with systemic inflammation and viral with systemic inflammation (-6.73 ± 1.78 vs. -13.5 ± 2.32%; P = 0.025). Non-viral with systemic inflammation PEx had a trend toward longer duration of intravenous antibiotics versus pauci-inflammation (18.1 ± 1.17 vs. 14.8 ± 1.19 days, P = 0.057). There were no differences in percent with lung function recovery to <10% of baseline FEV1pp. Similar results were seen in local and external validation cohorts comparing a pauci-inflammatory to viral/non-viral inflammatory exacerbation phenotypes. Conclusions: Subphenotypes of CF PEx exist with differences in biomarker profile, clinical presentation, and outcomes.
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Affiliation(s)
- Suzanne C. Carter
- National Referral Centre for Adult Cystic Fibrosis, St. Vincent’s University Hospital, Dublin, Ireland
- University College Dublin School of Medicine, Dublin, Ireland
| | | | - Kate M. O’Shea
- University College Dublin School of Medicine, Dublin, Ireland
| | - Orla M. O’Carroll
- National Referral Centre for Adult Cystic Fibrosis, St. Vincent’s University Hospital, Dublin, Ireland
| | - Ashutosh Sharma
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Aoife Bell
- University College Dublin School of Medicine, Dublin, Ireland
| | - Brian Keogan
- National Virus Reference Laboratory, University College Dublin, Dublin, Ireland
| | - Paul O’Reilly
- National Virus Reference Laboratory, University College Dublin, Dublin, Ireland
| | - Suzie Coughlan
- National Virus Reference Laboratory, University College Dublin, Dublin, Ireland
| | - Sheonagh M. Law
- Centre for Inflammation Research, University of Edinburgh, Edinburgh, Scotland
| | - Robert D. Gray
- Centre for Inflammation Research, University of Edinburgh, Edinburgh, Scotland
| | - Katherine B. Hisert
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, National Jewish Health, Denver, Colorado
- University of Washington, Seattle, Washington; and
| | | | - Gordon Cooke
- University College Dublin School of Medicine, Dublin, Ireland
- Technological University Dublin, Dublin, Ireland
| | - Brenda Grogan
- National Referral Centre for Adult Cystic Fibrosis, St. Vincent’s University Hospital, Dublin, Ireland
| | | | - Charles G. Gallagher
- National Referral Centre for Adult Cystic Fibrosis, St. Vincent’s University Hospital, Dublin, Ireland
- University College Dublin School of Medicine, Dublin, Ireland
| | - Trevor T. Nicholson
- National Referral Centre for Adult Cystic Fibrosis, St. Vincent’s University Hospital, Dublin, Ireland
| | - Bradley S. Quon
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Edward F. McKone
- National Referral Centre for Adult Cystic Fibrosis, St. Vincent’s University Hospital, Dublin, Ireland
- University College Dublin School of Medicine, Dublin, Ireland
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Genome Capture Sequencing Selectively Enriches Bacterial DNA and Enables Genome-Wide Measurement of Intrastrain Genetic Diversity in Human Infections. mBio 2022; 13:e0142422. [PMID: 36121157 PMCID: PMC9601202 DOI: 10.1128/mbio.01424-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Within-host evolution produces genetic diversity in bacterial strains that cause chronic human infections. However, the lack of facile methods to measure bacterial allelic variation in clinical samples has limited understanding of intrastrain diversity’s effects on disease. Here, we report a new method termed genome capture sequencing (GenCap-Seq) in which users inexpensively make hybridization probes from genomic DNA or PCR amplicons to selectively enrich and sequence targeted bacterial DNA from clinical samples containing abundant human or nontarget bacterial DNA. GenCap-Seq enables accurate measurement of allele frequencies over targeted regions and is scalable from specific genes to entire genomes, including the strain-specific accessory genome. The method is effective with samples in which target DNA is rare and inhibitory and DNA-degrading substances are abundant, including human sputum and feces. In proof-of-principle experiments, we used GenCap-Seq to investigate the responses of diversified Pseudomonas aeruginosa populations chronically infecting the lungs of people with cystic fibrosis to in vivo antibiotic exposure, and we found that treatment consistently reduced intrastrain genomic diversity. In addition, analysis of gene-level allele frequency changes suggested that some genes without conventional resistance functions may be important for bacterial fitness during in vivo antibiotic exposure. GenCap-Seq’s ability to scalably enrich targeted bacterial DNA from complex samples will enable studies on the effects of intrastrain and intraspecies diversity in human infectious disease.
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Planet PJ. Adaptation and Evolution of Pathogens in the Cystic Fibrosis Lung. J Pediatric Infect Dis Soc 2022; 11:S23-S31. [PMID: 36069898 PMCID: PMC9451014 DOI: 10.1093/jpids/piac073] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 07/11/2022] [Indexed: 02/05/2023]
Abstract
As opposed to acute respiratory infections, the persistent bacterial infections of the lung that characterize cystic fibrosis (CF) provide ample time for bacteria to evolve and adapt. The process of adaptation is recorded in mutations that accumulate over time in the genomes of the infecting bacteria. Some of these mutations lead to obvious phenotypic differences such as antibiotic resistance or the well-known mucoid phenotype of Pseudomonas aeruginosa. Other mutations may be just as important but harder to detect such as increased mutation rates, cell surface changes, and shifts in metabolism and nutrient acquisition. Remarkably, many of the adaptations occur again and again in different patients, signaling that bacteria are adapting to solve specific challenges in the CF respiratory tract. This parallel evolution even extends across distinct bacterial species. This review addresses the bacterial systems that are known to change in long-term CF infections with a special emphasis on cross-species comparisons. Consideration is given to how adaptation may impact health in CF, and the possible evolutionary mechanisms that lead to the repeated parallel adaptations.
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Affiliation(s)
- Paul J Planet
- Corresponding Author: Paul J. Planet, MD, PhD, 3615 Civic Center Blvd, Philadelphia, PA 19104. E-mail:
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Genetic and Transcriptomic Characteristics of RhlR-Dependent Quorum Sensing in Cystic Fibrosis Isolates of Pseudomonas aeruginosa. mSystems 2022; 7:e0011322. [PMID: 35471121 PMCID: PMC9040856 DOI: 10.1128/msystems.00113-22] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In people with the genetic disease cystic fibrosis (CF), bacterial infections involving the opportunistic pathogen Pseudomonas aeruginosa are a significant cause of morbidity and mortality. P. aeruginosa uses a cell-cell signaling mechanism called quorum sensing (QS) to regulate many virulence functions. One type of QS consists of acyl-homoserine lactone (AHL) signals produced by LuxI-type signal synthases, which bind a cognate LuxR-type transcription factor. In laboratory strains and conditions, P. aeruginosa employs two AHL synthase/receptor pairs arranged in a hierarchy, with the LasI/R system controlling the RhlI/R system and many downstream virulence factors. However, P. aeruginosa isolates with inactivating mutations in lasR are frequently isolated from chronic CF infections. We and others have shown that these isolates frequently use RhlR as the primary QS regulator. RhlR is rarely mutated in CF and environmental settings. We were interested in determining whether there were reproducible genetic characteristics of these isolates and whether there was a central group of genes regulated by RhlR in all isolates. We examined five isolates and found signatures of adaptation common to CF isolates. We did not identify a common genetic mechanism to explain the switch from Las- to Rhl-dominated QS. We describe a core RhlR regulon encompassing 20 genes encoding 7 products. These results suggest a key group of QS-regulated factors important for pathogenesis of chronic infections and position RhlR as a target for anti-QS therapeutics. Our work underscores the need to sample a diversity of isolates to understand QS beyond what has been described in laboratory strains. IMPORTANCE The bacterial pathogen Pseudomonas aeruginosa can cause chronic infections that are resistant to treatment in immunocompromised individuals. Over the course of these infections, the original infecting organism adapts to the host environment. P. aeruginosa uses a cell-cell signaling mechanism termed quorum sensing (QS) to regulate virulence factors and cooperative behaviors. The key QS regulator in laboratory strains, LasR, is frequently mutated in infection-adapted isolates, leaving another transcription factor, RhlR, in control of QS gene regulation. Such isolates provide an opportunity to understand Rhl-QS regulation without the confounding effects of LasR, as well as the scope of QS in the context of within-host evolution. We show that a core group of virulence genes is regulated by RhlR in a variety of infection-adapted LasR-null isolates. Our results reveal commonalities in infection-adapted QS gene regulation and key QS factors that may serve as therapeutic targets in the future.
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