scholarly journals Adaptation to an amoeba host leads to Pseudomonas aeruginosa isolates with attenuated virulence

2022 ◽  
Author(s):  
Wai Leong ◽  
Wee Han Poh ◽  
Jonathan Williams ◽  
Carla Lutz ◽  
M. Mozammel Hoque ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Late Stage ◽  
Early Stage ◽  
Opportunistic Pathogen ◽  
Phenotypic Traits ◽  
Nucleotide Polymorphisms ◽  
Chronic Infections ◽  
The Impact

The opportunistic pathogen Pseudomonas aeruginosa , is ubiquitous in the environment, and in humans is capable of causing acute or chronic infections. In the natural environment, predation by bacterivorous protozoa represents a primary threat to bacteria. Here, we determined the impact of long-term exposure of P. aeruginosa to predation pressure. P. aeruginosa persisted when co-incubated with the bacterivorous Acanthamoeba castellanii for extended periods and produced genetic and phenotypic variants. Sequencing of late-stage amoeba-adapted P. aeruginosa isolates demonstrated single nucleotide polymorphisms within genes that encode known virulence factors and this correlated with a reduction in expression of virulence traits. Virulence towards the nematode, Caenorhabditis elegans , was attenuated in late-stage amoeba-adapted P. aeruginosa compared to early-stage amoeba-adapted and non-adapted counterparts. Further, late-stage amoeba-adapted P. aeruginosa showed increased competitive fitness and enhanced survival in amoeba as well as in macrophage and neutrophils. Interestingly, our findings indicate that the selection imposed by amoeba resulted in P. aeruginosa isolates with reduced virulence and enhanced fitness, similar to those recovered from chronic cystic fibrosis infections. Thus, predation by protozoa and long-term colonization of the human host may represent similar environments that select for similar losses of gene function. Importance Pseudomonas aeruginosa is an opportunistic pathogen that causes both acute infections in plants and animals, including humans, and chronic infections in immunocompromised and cystic fibrosis patients. This bacterium is commonly found in soils and water where bacteria are constantly under threat of being consumed by bacterial predators, e.g. protozoa. To escape being killed, bacteria have evolved a suite of mechanisms that protect them from being consumed or digested. Here, we examine the effect of long-term predation on the genotypes and phenotypes expressed by P. aeruginosa . We show that long term co-incubation with protozoa resulted in mutations that resulted in P. aeruginosa becoming less pathogenic. This is particularly interesting as we see similar mutations arise in bacteria associated with chronic infections. Importantly, the genetic and phenotypic traits possessed by late-stage amoeba-adapted P. aeruginosa are similar to what is observed for isolates obtained from chronic cystic fibrosis infections. This notable overlap in adaptation to different host types suggests similar selection pressures amongst host cell types as well as similar adaptation strategies.

scholarly journals Pseudomonas aeruginosa isolates co-incubated with Acanthamoeba castellanii exhibit phenotypes similar to chronic cystic fibrosis isolates

2020 ◽  
Author(s):  
Wai Leong ◽  
Carla Lutz ◽  
Jonathan Williams ◽  
Yan Hong Poh ◽  
Benny Yeo Ken Yee ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Late Stage ◽  
Early Stage ◽  
Acanthamoeba Castellanii ◽  
Opportunistic Pathogen ◽  
Human Neutrophils ◽  
Phenotypic Traits ◽  
Chronic Infections

AbstractThe opportunistic pathogen, Pseudomonas aeruginosa, is ubiquitous in the environment, and in humans is capable of causing acute and chronic infections. P. aeruginosa, when co-incubated with the bacterivorous amoeba, Acanthamoeba castellanii, for extended periods, produced genetic and phenotypic variants. Sequencing of late-stage amoeba-adapted P. aeruginosa isolates demonstrated single nucleotide polymorphisms within genes that encode known virulence factors, and this correlated with a reduction in expression of virulence traits. Virulence towards the nematode, Caenorhabditis elegans, was attenuated in late-stage amoeba-adapted P. aeruginosa compared to early stage amoeba-adapted and non-adapted counterparts. Late-stage amoeba-adapted P. aeruginosa lost competitive fitness compared to non-adapted counterparts when grown in nutrient rich media. However, non-adapted P. aeruginosa were rapidly cleared by amoeba predation, whereas late-stage amoeba-adapted isolates remained in higher numbers 24 h after ingestion by amoeba. In addition, there was reduced uptake by macrophage of amoeba-adapted isolates and reduced uptake by human neutrophils as well as increased survival in the presence of neutrophils. Our findings indicate that the selection imposed by amoeba on P. aeruginosa resulted in reduced virulence over time. Importantly, the genetic and phenotypic traits possessed by late-stage amoeba-adapted P. aeruginosa are similar to what is observed for isolates obtained from chronic cystic fibrosis infections. This notable overlap in adaptation to different host types suggests similar selection pressures among host cell types.Author SummaryPseudomonas aeruginosa is an opportunistic pathogen that causes both acute infections in plants and animals, including humans and also causes chronic infections in immune compromised and cystic fibrosis patients. This bacterium is commonly found in soils and water where bacteria are constantly under threat of being consumed by the bacterial predators, protozoa. To escape being killed, bacteria have evolved a suite of mechanisms that protect them from being consumed or digested. Here we examined the effect of long-term predation on the genotype and phenotypes expressed by P. aeruginosa. We show that long-term co-incubation with protozoa resulted in mutations in the bacteria that made them less pathogenic. This is particularly interesting as we see similar mutations arise in bacteria associated with chronic infections. Thus, predation by protozoa and long term colonization of the human host may represent similar environments that select for similar losses in gene functions.

scholarly journals Heterogenous response to R-pyocin killing in populations of Pseudomonas aeruginosa sourced from cystic fibrosis lungs

2020 ◽  
Author(s):  
Madeline Mei ◽  
Jacob Thomas ◽  
Stephen P. Diggle
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Genotypic Diversity ◽  
Opportunistic Pathogen ◽  
Chronic Infections ◽  
Bacterial Populations ◽  
Heterogeneous Populations ◽  
Lung Infections ◽  
The Impact ◽  
Lps Binding

AbstractBacteriocins are proteinaceous antimicrobials produced by bacteria which are active against other strains of the same species. R-type pyocins are phage tail-like bacteriocins produced by Pseudomonas aeruginosa. Due to their anti-pseudomonal activity, R-pyocins have potential as therapeutics in infection. P. aeruginosa is a Gram-negative opportunistic pathogen and is particularly problematic for individuals with cystic fibrosis (CF). P. aeruginosa from CF lung infections develop increasing resistance to antibiotics, making new treatment approaches essential. P. aeruginosa populations become phenotypically and genotypically diverse during infection, however little is known of the efficacy of R-pyocins against heterogeneous populations. R-pyocins vary by subtype (R1-R5), distinguished by binding to different residues on the lipopolysaccharide (LPS). Each type varies in killing spectrum, and each strain produces only one R-type. To evaluate the prevalence of different R-types, we screened P. aeruginosa strains from the International Pseudomonas Consortium Database (IPCD) and from our biobank of CF strains. We found that (i) R1-types were the most prevalent R-type among strains from respiratory sources and (ii) isolates collected from the same patient have the same R-type. We then assessed the impact of diversity on R-pyocin susceptibility and found a heterogenous response to R-pyocins within populations, likely due to differences in the LPS core. Our work reveals that heterogeneous populations of microbes exhibit variable susceptibility to R-pyocins and highlights that there is likely heterogeneity in response to other types of LPS-binding antimicrobials, including phage.ImportanceR-pyocins have potential as alternative therapeutics against Pseudomonas aeruginosa in chronic infection, however little is known about the efficacy of R-pyocins in heterogeneous bacterial populations. P. aeruginosa is known to become resistant to multiple antibiotics, as well as evolve phenotypic and genotypic diversity over time; thus it is particularly difficult to eradicate in chronic cystic fibrosis (CF) lung infections. In this study, we found that P. aeruginosa populations from CF lungs maintain the same R-pyocin genotype but exhibit heterogeneity in susceptibility to R-pyocins from other strains. Our findings suggest there is likely heterogeneity in response to other types of LPS-binding antimicrobials, such as phage, highlighting the necessity of further studying the potential of LPS-binding antimicrobial particles as alternative therapies in chronic infections.

scholarly journals Molecular Epidemiology and Dynamics of Pseudomonas aeruginosa Populations in Lungs of Cystic Fibrosis Patients

2007 ◽  
Vol 75 (5) ◽  
pp. 2214-2224 ◽  
Author(s):  
Lars Jelsbak ◽  
Helle Krogh Johansen ◽  
Anne-Louise Frost ◽  
Regitze Thøgersen ◽  
Line E. Thomsen ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Opportunistic Pathogen ◽  
Infection Process ◽  
Fundamental Aspect ◽  
Chronic Infections ◽  
Persistent Infections ◽  
Infection Dynamics ◽  
Evolutionary Success

ABSTRACT The ability to establish lifelong persistent infections is a fundamental aspect of the interactions between many pathogenic microorganisms and their mammalian hosts. One example is chronic lung infections by the opportunistic pathogen Pseudomonas aeruginosa in cystic fibrosis (CF) patients. This infection process is associated with extensive genetic adaptation and microevolution of the infecting bacteria. Through investigations of P. aeruginosa populations and infection dynamics in a group of CF patients followed at the Danish CF Clinic in Copenhagen, we have identified two distinct and dominant clones that have evolved into highly successful colonizers of CF patient airways. A significant component of the evolutionary success of these two clones has been their efficient transmissibility among the CF patients. The two clones have been present and transmitted among different CF patients for more than 2 decades. Our data also suggest that the P. aeruginosa population structure in the CF patient airways has been influenced by competition between different clones and that the two dominant clones have been particularly competitive within the lungs, which may add to their overall establishment success. In contrast, we show that adaptive traits commonly associated with establishment of chronic P. aeruginosa infections of CF patients, such as transition to the mucoid phenotype and production of virulence factors, play minor roles in the ability of the two dominant clones to spread among patients and cause long-term chronic infections. These findings suggest that hitherto-unrecognized evolutionary pathways may be involved in the development of successful and persistent P. aeruginosa colonizers of CF patient lungs.

scholarly journals Heterogenous Susceptibility to R-Pyocins in Populations of Pseudomonas aeruginosa Sourced from Cystic Fibrosis Lungs

mBio ◽  
2021 ◽  
Vol 12 (3) ◽  
Author(s):  
Madeline Mei ◽  
Jacob Thomas ◽  
Stephen P. Diggle
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Genotypic Diversity ◽  
Opportunistic Pathogen ◽  
Chronic Infections ◽  
Heterogeneous Populations ◽  
Content Type ◽  
Lung Infections ◽  
The Impact ◽  
Lps Binding

ABSTRACT Bacteriocins are proteinaceous antimicrobials produced by bacteria that are active against other strains of the same species. R-type pyocins are phage tail-like bacteriocins produced by Pseudomonas aeruginosa. Due to their antipseudomonal activity, R-pyocins have potential as therapeutics in infection. P. aeruginosa is a Gram-negative opportunistic pathogen and is particularly problematic for individuals with cystic fibrosis (CF). P. aeruginosa organisms from CF lung infections develop increasing resistance to antibiotics, making new treatment approaches essential. P. aeruginosa populations become phenotypically and genotypically diverse during infection; however, little is known of the efficacy of R-pyocins against heterogeneous populations. R-pyocins vary by subtype (R1 to R5), distinguished by binding to different residues on the lipopolysaccharide (LPS). Each type varies in killing spectrum, and each strain produces only one R-type. To evaluate the prevalence of different R-types, we screened P. aeruginosa strains from the International Pseudomonas Consortium Database (IPCD) and from our biobank of CF strains. We found that (i) R1-types were the most prevalent R-type among strains from respiratory sources, (ii) a large number of strains lack R-pyocin genes, and (iii) isolates collected from the same patient have the same R-type. We then assessed the impact of intrastrain diversity on R-pyocin susceptibility and found a heterogenous response to R-pyocins within populations, likely due to differences in the LPS core. Our work reveals that heterogeneous populations of microbes exhibit variable susceptibility to R-pyocins and highlights that there is likely heterogeneity in response to other types of LPS-binding antimicrobials, including phage. IMPORTANCE R-pyocins have potential as alternative therapeutics against Pseudomonas aeruginosa in chronic infection; however, little is known about the efficacy of R-pyocins in heterogeneous bacterial populations. P. aeruginosa is known to become resistant to multiple antibiotics and to evolve phenotypic and genotypic diversity over time; thus, it is particularly difficult to eradicate in chronic cystic fibrosis (CF) lung infections. In this study, we found that P. aeruginosa populations from CF lungs maintain the same R-pyocin genotype but exhibit heterogeneity in susceptibility to R-pyocins from other strains. Our findings suggest there is heterogeneity in response to other types of LPS-binding antimicrobials, such as phage, highlighting the necessity of further studying the potential of LPS-binding antimicrobial particles as alternative therapies in chronic infections.

scholarly journals Rapid diversification of Pseudomonas aeruginosa in cystic fibrosis lung-like conditions

2018 ◽  
Vol 115 (42) ◽  
pp. 10714-10719 ◽  
Author(s):  
Alana Schick ◽  
Rees Kassen
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Chronic Infection ◽  
Opportunistic Pathogen ◽  
Chronic Infections ◽  
Evolutionary Diversification ◽  
Nutritional Conditions ◽  
Patient Health ◽  
Rapid Diversification

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.

scholarly journals Poly (acetyl arginyl) glucosamine attenuates Pseudomonas aeruginosa in a rat lung infection model

2021 ◽  
Author(s):  
Bryan Garcia ◽  
Melissa S. McDaniel ◽  
Allister J. Loughran ◽  
J. Dixon Johns ◽  
Vidya Narayanaswamy ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Respiratory Infections ◽  
Bacterial Species ◽  
Membrane Integrity ◽  
Opportunistic Pathogen ◽  
Infection Model ◽  
Total Biomass ◽  
Chronic Infections

Pseudomonas aeruginosa is a common opportunistic pathogen that can cause chronic infections in multiple disease states, including respiratory infections in patients with cystic fibrosis (CF) and non-CF bronchiectasis. Like many opportunists, P. aeruginosa forms multicellular biofilm communities that are widely thought to be an important determinant of bacterial persistence and resistance to antimicrobials and host immune effectors during chronic/recurrent infections. Poly (acetyl, arginyl) glucosamine (PAAG) is a glycopolymer which has antimicrobial activity against a broad range of bacterial species, and also has mucolytic activity which can normalize rheologic properties of cystic fibrosis mucus. In this study, we sought to evaluate the effect of PAAG on P. aeruginosa bacteria within biofilms in vitro, and in the context of experimental pulmonary infection in a rodent infection model. PAAG treatment caused significant bactericidal activity against P. aeruginosa biofilms, and a reduction in the total biomass of preformed P. aeruginosa biofilms on abiotic surfaces, as well as on the surface of immortalized cystic fibrosis human bronchial epithelial cells. Studies of membrane integrity indicated that PAAG causes changes to P. aeruginosa cell morphology and dysregulates membrane polarity. PAAG treatment reduced infection and consequent tissue inflammation in experimental P. aeruginosa rat infections. Based on these findings we conclude that PAAG represents a novel means to combat P. aeruginosa infection, which may warrant further evaluation as a therapeutic.

scholarly journals Recycling of Peptidyl-tRNAs by Peptidyl-tRNA Hydrolase Counteracts Azithromycin-Mediated Effects on Pseudomonas aeruginosa

2013 ◽  
Vol 57 (4) ◽  
pp. 1617-1624 ◽  
Author(s):  
Julia Gödeke ◽  
Christian Pustelny ◽  
Susanne Häussler
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Molecular Mechanisms ◽  
Expression Profiles ◽  
Opportunistic Pathogen ◽  
Phase Cell ◽  
Chronic Infections ◽  
Content Type ◽  
Mediated Effects ◽  
Protein Expression Profiles ◽  
The Impact

ABSTRACTAcute and chronic infections caused by the opportunistic pathogenPseudomonas aeruginosapose a serious threat to human health worldwide, and its increasing resistance to antibiotics requires alternative treatments that are more effective than available strategies. Clinical studies have clearly demonstrated that cystic fibrosis (CF) patients with chronicP. aeruginosainfections benefit from long-term low-dose azithromycin (AZM) treatment. Immunomodulating activity, the impact of AZM on the expression of quorum-sensing-dependent virulence factors, type three secretion, and motility inP. aeruginosaseem to contribute to the therapeutic response. However, to date, the molecular mechanisms underlying these AZM effects have remained elusive. Our data indicate that the AZM-mediated phenotype is caused by a depletion of the intracellular pools of tRNAs available for protein synthesis. Overexpression of theP. aeruginosapeptidyl-tRNA hydrolase, which recycles the tRNA from peptidyl-tRNA drop-off during translation, counteracted the effects of AZM on stationary-phase cell killing, cytotoxicity, and the production of rhamnolipids and partially restored swarming motility. Intriguingly, the exchange of a rare for a frequent codon inrhlRalso explicitly diminished the AZM-mediated decreased production of rhamnolipids. These results indicate that depletion of the tRNA pools by AZM seems to affect the translation of genes that use rare aminoacyl-tRNA isoacceptors to a great extent and might explain the selective activity of AZM on theP. aeruginosaproteome and possibly also on the protein expression profiles of other bacterial pathogens.

scholarly journals The high persister phenotype ofPseudomonas aeruginosais associated with increased fitness and persistence in cystic fibrosis airways

2019 ◽  
Author(s):  
Biljana Mojsoska ◽  
David R. Cameron ◽  
Jennifer A. Bartell ◽  
Janus Anders Juul Haagensen ◽  
Lea M. Sommer ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistance ◽  
Genetic Alterations ◽  
Antibiotic Tolerance ◽  
High Throughput Screening Assay ◽  
The Impact ◽  
Over Time ◽  
Better Than

AbstractDespite intensive antibiotic treatment of cystic fibrosis (CF) patients,Pseudomonas aeruginosaoften persists in patient airways for decades, and can do so without the development of antibiotic resistance. Using a high-throughput screening assay of survival after treatment with high concentrations of ciprofloxacin, we have determined the prevalence of high-persister variants (Hip) in a large patient cohort. In a screen of 467 longitudinal clinical isolates ofP. aeruginosafrom 40 CF patients, we classified 25.7% as Hip. Hip were identified in 26 patients, but only a few bacterial lineages were dominated by Hip. Instead, the emergence of Hip increased over time, suggesting that CF airways treated with ciprofloxacin select for Hip with an increased fitness in this environment. We generally observed diverse genetic changes in the Hip isolate population (as many co-occurring routes to increased fitness exist), but interestingly elevated mutation counts in the RpoN gene of 18 Hip isolates suggest that this sigma factor plays a role in shaping levels of antibiotic tolerance. To probe the impact of the Hip phenotype in a CF-similar environment, we tested the fitness properties of otherwise genotypically and phenotypically similar low-persister (Lop) and Hip isolates in co-culture using a specialized flow-cell biofilm system mimicking pharmacokinetic/-dynamic antibiotic dosing. Hip survived ciprofloxacin treatment far better than Lop isolates. The results of this investigation provide novel insights into persister dynamics and fitness contributions to survival in the CF lung, and show that the Hip phenotype of antibiotic susceptible bacteria plays an important role in long-term infections.SignificanceAntibiotic resistance is emphasized as a rapidly increasing health threat, but antibiotic tolerance via the occurrence of persister cells in antibiotic-treated bacterial populations is clinically and publicly neglected. In 40 CF patients representing a well-established human infection model – long-term lung infections byPseudomonas aeruginosa– we show the emergence and accumulation of persister variants in a clinical population heavily reliant on antibiotic therapy. We observe that the high-persister (Hip) phenotype is independent of resistance and likely the consequence of numerous genetic alterations, complicating surveillance and inhibition in the clinic. Furthermore, we find Hip are selected for over time, survive better than ‘normal’ bacteria, and can outcompete them in CF-similar conditions, ultimately affecting 65% of patients in an early disease cohort.

scholarly journals Small molecules with antibiofilm, antivirulence and antibiotic synergy activities againstPseudomonas aeruginosa

2016 ◽  
Author(s):  
Erik van Tilburg Bernardes ◽  
Laetitia Charron-Mazenod ◽  
David Reading ◽  
Shauna L. Reckseidler-Zenteno ◽  
Shawn Lewenza
Keyword(s):  
Cystic Fibrosis ◽  
Extracellular Matrix ◽  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistance ◽  
Small Molecules ◽  
Biofilm Formation ◽  
Chronic Infections ◽  
Term Survival ◽  
Lung Infections

AbstractBiofilm formation is a universal bacterial strategy for long-term survival in nature and during infections. Biofilms are dense microbial communities enmeshed within a polymeric extracellular matrix that protects bacteria from antibiotic exposure and the immune system and thus contribute to chronic infections.Pseudomonas aeruginosais an archetypal biofilm-forming organism that utilizes a biofilm growth strategy to cause chronic lung infections in Cystic Fibrosis (CF) patients. The extracellular matrix ofP. aeruginosabiofilms is comprised mainly of exopolysaccharides (EPS) and DNA. Both mucoid and non-mucoid isolates ofP. aeruginosaproduces the Pel and Psl EPS, each of which have important roles in antibiotic resistance, biofilm formation and immune evasion. Given the central importance of the Pel and Psl EPS in biofilm structure, they are attractive targets for novel anti-infective compounds. In this study we used a high throughput gene expression screen to identify compounds that repress expression ofpelandpslgenes as measured by transcriptionalluxfusions. Testing of thepel/pslrepressors demonstrated an antibiofilm activity against microplate and flow chamber biofilms formed by wild type and hyperbiofilm forming strains. To determine the potential role of EPS in virulence, mutants inpel/pslwere shown to have reduced virulence in the feeding behavior and slow killing virulence assays inCaenorhabditis elegans. The antibiofilm molecules also reducedP. aeruginosaPAO1 virulence in the nematode slow killing model. Importantly, the combination of antibiotics and antibiofilm compounds were synergistic in killingP. aeruginosabiofilms. These small molecules represent a novel anti-infective strategy for the possible treatment of chronicP. aeruginosainfections.Author summaryBacteria use the strategy of growing as a biofilm to promote long-term survival and therefore to cause chronic infections. One of the best examples isPseudomonas aeruginosaand the chronic lung infections in individuals with Cystic Fibrosis (CF). Biofilms are generally a dense community of bacteria enmeshed in an extracellular matrix that protects bacteria from numerous environmental stresses, including antibiotics and the immune system. In this study we developed an approach to identifyP. aeruginosabiofilm inhibitors by repressing the production of the matrix exopolysaccharide (EPS) polymers. Bacteria treated with compounds and then fed to the nematode also had showed reduced virulence by promoting nematode survival. To tackle the problem of biofilm tolerance of antibiotics, the compounds identified here also had the beneficial property of increasing the biofilm sensitivity to different classes of antibiotics. The compounds disarm bacteria but they do not kill or limit growth like antibiotics. We provide further support that disarmingP. aeruginosamay be a critical anti-infective strategy that limits the development of antibiotic resistance, and provides a new way for treating chronic infections.

scholarly journals Rapid diversification of Pseudomonas aeruginosa in cystic fibrosis lung-like conditions

2017 ◽  
Author(s):  
Alana Schick ◽  
Rees Kassen
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Chronic Infection ◽  
Opportunistic Pathogen ◽  
Clinical Isolates ◽  
Chronic Infections ◽  
Evolutionary Diversification ◽  
Nutritional Conditions ◽  
Patient Health

AbstractChronic 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. The increased viscosity associated with the thick mucous layer in the CF airway had little impact on within-population diversification but did promote divergence among populations. Notably, in vitro evolution recapitulated patho-adaptive 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. They also underscore the need to obtain diverse samples of P. aeruginosa when developing treatment plans. We suggest that diversification, by generating extensive phenotypic and genetic variation on which selection can act, may be a key first step in the transition from transient to chronic infection.Significance StatementChronic infection with the opportunistic pathogen Pseudomonas aeruginosa is the leading cause of lung transplant or death in cystic fibrosis patients. P. aeruginosa diversifies in the CF lung, although why this happens remains a mystery. We allowed P. aeruginosa to evolve in the laboratory under a range of conditions approximating the CF lung. The diversity of evolved populations was highest, and most closely resembled the range of phenotypes among clinical isolates, in environments resembling the spectrum of nutritional resources available in the CF lung. Our results point to the nutritional complexity of the CF lung as a major driver of diversification and they suggest that diversity could be important in the development of chronic infections.

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