Dataset Information

In vivo evidence of Pseudomonas aeruginosa nutrient acquisition and pathogenesis in the lungs of cystic fibrosis patients.

ABSTRACT: One of the hallmarks of Pseudomonas aeruginosa infection in cystic fibrosis (CF) patients is very-high-cell-density (HCD) replication in the lung, allowing this bacterium to induce virulence controlled by the quorum-sensing systems. However, the nutrient sources sustaining HCD replication in this chronic infection are largely unknown. Here, we performed microarray studies of P. aeruginosa directly isolated from the lungs of CF patients to demonstrate its metabolic capability and virulence in vivo. In vivo microarray data, confirmed by real-time reverse transcription-PCR, indicated that the P. aeruginosa population expressed several genes for virulence, drug resistance, and utilization of multiple nutrient sources (lung surfactant lipids and amino acids) contributing to HCD replication. The most abundant lung surfactant lipid molecule, phosphatidylcholine (PC), induces key genes of P. aeruginosa pertinent to PC degradation in vitro as well as in vivo within the lungs of CF patients. The results support recent research indicating that P. aeruginosa exists in the lungs of CF patients as a diverse population with full virulence potential. The data also indicate that there is deregulation of several pathways, suggesting that there is in vivo evolution by deregulation of a large portion of the transcriptome during chronic infection in CF patients. To our knowledge, this is the first in vivo transcriptome analysis of P. aeruginosa in a natural infection in CF patients, and the results indicate several important aspects of P. aeruginosa pathogenesis, drug resistance, nutrient utilization, and general metabolism within the lungs of CF patients.

SUBMITTER: Son MS

PROVIDER: S-EPMC2168270 | biostudies-literature | 2007 Nov

REPOSITORIES: biostudies-literature

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In vivo evidence of Pseudomonas aeruginosa nutrient acquisition and pathogenesis in the lungs of cystic fibrosis patients.

Son Mike S MS Matthews Wallace J WJ Kang Yun Y Nguyen David T DT Hoang Tung T TT

Infection and immunity 20070827 11

One of the hallmarks of Pseudomonas aeruginosa infection in cystic fibrosis (CF) patients is very-high-cell-density (HCD) replication in the lung, allowing this bacterium to induce virulence controlled by the quorum-sensing systems. However, the nutrient sources sustaining HCD replication in this chronic infection are largely unknown. Here, we performed microarray studies of P. aeruginosa directly isolated from the lungs of CF patients to demonstrate its metabolic capability and virulence in viv ...[more]

PMID: 17724070

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Project description:One of the hallmarks of Pseudomonas aeruginosa cystic fibrosis (CF) infection is very high-cell-density (HCD) replication in the lung, allowing this bacterium to induce virulence controlled by HCD quorum-sensing systems. However, the nutrient sources sustaining HCD replication in this chronic infection is largely unknown. Hence, understanding the nutrient factors contributing to HCD in the CF lung will yield new insights into the 'metabolic pathogenicity' and potential treatment of CF infections caused by P. aeruginosa. Herein, we performed microarray studies of P. aeruginosa directly isolated from the CF lung to demonstrate its metabolic capability and virulence in vivo. Our in vivo microarray data, confirmed by real-time reverse-transcription-PCR, indicated P. aeruginosa expressed several genes for virulence, drug-resistance, and utilization of multiple nutrient sources (lung surfactant lipids and amino acids) contributing to HCD replication. The data also indicates deregulation of several pathways, suggesting in vivo evolution by deregulation of a large portion of the transcriptome during chronic CF infection. To our knowledge, this is the first in vivo transcriptome of P. aeruginosa in a natural CF infection, and it indicates several important aspects of pathogenesis, drug-resistance, and nutrient-utilization never before observed in vivo. Experiment Overall Design: The purpose of the experiment was to observe which genes are upregulated in P. aeruginosa during chronic CF lung infection as compared to PAO1. All in vitro studies were grown in 1x M9 minimal media supplemented with 20 mM citrate and grown to mid-log phase prior to RNA isolation. The in vivo RNA was isolated directly from CF sputum samples after TRIzol treatment. Each in vitro sample (both for PAO1 and the CF sputum pool isolate) were processed individually and in triplicate. Two in vivo isolations from sputum were conducted from the same patient but two different sputum samples. After isolation of total RNA, samples were processed for microarrays (i.e. cDNA synthesis, fragmentation, labeling, etc) as recommended by Affymetrix, and processed on the GeneChip as recommended by Affymetrix.

Project description:Epidemic strains of Pseudomonas aeruginosa are highly virulent opportunistic pathogens with increased transmissibility and enhanced antimicrobial resistance. Understanding the cellular mechanisms behind this heightened virulence and resistance is critical. Peptidoglycan (PG) is an integral component of P. aeruginosa cells that is essential to its survival and a target for antimicrobials. Here, we examined the global PG composition of two P. aeruginosa epidemic strains, LESB58 and LESlike1, and compared them to the common laboratory strains PAO1 and PA14. We also examined changes in PG composition when the strains were cultured under nutrient conditions that resembled cystic fibrosis lung infections. We identified 448 unique muropeptides and provide the first evidence for stem peptides modified with O-methylation, meso-diaminopimelic acid (mDAP) deamination, and novel substitutions of mDAP residues within P. aeruginosa PG. Our results also present the first evidence for both d,l- and l,d-endopeptidase activity on the PG sacculus of a Gram-negative organism. The PG composition of the epidemic strains varied significantly when grown under conditions resembling cystic fibrosis (CF) lung infections, showing increases in O-methylated stem peptides and decreases in l,d-endopeptidase activity as well as an increased abundance of de-N-acetylated sugars and l,d-transpeptidase activity, which are related to bacterial virulence and antibiotic resistance, respectively. We also identified strain-specific changes where LESlike1 increased the addition of unique amino acids to the terminus of the stem peptide and LESB58 increased amidase activity. Overall, this study demonstrates that P. aeruginosa PG composition is primarily influenced by nutrient conditions that mimic the CF lung; however, inherent strain-to-strain differences also exist. IMPORTANCE Using peptidoglycomics to examine the global composition of the peptidoglycan (PG) allows insights into the enzymatic activity that functions on this important biopolymer. Changes within the PG structure have implications for numerous physiological processes, including virulence and antimicrobial resistance. The identification of highly unique PG modifications illustrates the complexity of this biopolymer in Pseudomonas aeruginosa. Analyzing the PG composition of clinical P. aeruginosa epidemic strains provides insights into the increased virulence and antimicrobial resistance of these difficult-to-eradicate infections.

Project description: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.

Project description:Genome analyses have documented that there are differences in gene repertoire between evolutionary distant lineages of the same bacterial species; however, less is known about microevolutionary dynamics of gene loss and acquisition within bacterial lineages as they evolve over years. Here, we analyzed the genomes of 45 Pseudomonas aeruginosa lineages evolving in the lungs of cystic fibrosis (CF) patients to identify genes that are lost or acquired during the first years of infection. On average, lineage genome content changed by 88 genes (range, 0 to 473). Genes were more often lost than acquired, and prophage genes were more variable than bacterial genes. We identified convergent loss or acquisition of the same genes across lineages, suggesting selection for loss and acquisition of certain genes in the host environment. We found that a notable proportion of such genes are associated with virulence; a trait previously shown to be important for adaptation. Furthermore, we also compared the genomes across lineages to show that the within-lineage variable genes (i.e., genes that had been lost or acquired during the infection) often belonged to genomic content not shared across all lineages. In sum, our analysis adds to the knowledge on the pace and drivers of gene loss and acquisition in bacteria evolving over years in a human host environment and provides a basis to further understand how gene loss and acquisition play roles in lineage differentiation and host adaptation.IMPORTANCE Bacterial airway infections, predominantly caused by P. aeruginosa, are a major cause of mortality and morbidity of CF patients. While short insertions and deletions as well as point mutations occurring during infection are well studied, there is a lack of understanding of how gene loss and acquisition play roles in bacterial adaptation to the human airways. Here, we investigated P. aeruginosa within-host evolution with regard to gene loss and acquisition. We show that during long-term infection P. aeruginosa genomes tend to lose genes, in particular, genes related to virulence. This adaptive strategy allows reduction of the genome size and evasion of the host's immune response. This knowledge is crucial to understand the basic mutational steps that, on the timescale of years, diversify lineages and adds to the identification of bacterial genetic determinants that have implications for CF disease.

Dataset Information

In vivo evidence of Pseudomonas aeruginosa nutrient acquisition and pathogenesis in the lungs of cystic fibrosis patients.

Publications

In vivo evidence of Pseudomonas aeruginosa nutrient acquisition and pathogenesis in the lungs of cystic fibrosis patients.

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