The high amino-acid content of sputum from cystic fibrosis patients promotes growth of auxotrophic Pseudomonas aeruginosa

Barth, A. L.; Pitt, T. L.

doi:10.1099/00222615-45-2-110

Cited by 126 publications

(124 citation statements)

References 22 publications

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“…The behavior of P. aeruginosa-and Climax Community-dominated samples matches much of what is recorded in the literature: that the organism grows anaerobically using denitrification in antibiotic-resistant biofilms (Worlitzsch et al, 2002;Palmer et al, 2005;Hogardt and Heesemann, 2010;Schobert and Jahn, 2010). The elevated pH in the media may be due to the production of ammonia from amino-acid breakdown, often observed with P. aeruginosa grown in a CF state (Verhoogt et al, 1992;Barth and Pitt, 1996;Thomas et al, 2000;Frimmersdorf et al, 2010), and previously demonstrated to accumulate in WinCF capillary tubes after the growth of CF microbes . Thus the P. aeruginosa WinCF responses may reflect the true physiology of this microbe and others like it in the CF lung and is in stark contrast to the physiology of the Attack Community during exacerbation events.…”

Section: Sources Of the Fermentative Responsesupporting

confidence: 78%

A Winogradsky-based culture system shows an association between microbial fermentation and cystic fibrosis exacerbation

et al. 2014

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There is a poor understanding of how the physiology of polymicrobial communities in cystic fibrosis (CF) lungs contributes to pulmonary exacerbations and lung function decline. In this study, a microbial culture system based on the principles of the Winogradsky column (WinCF system) was developed to study the physiology of CF microbes. The system used glass capillary tubes filled with artificial sputum medium to mimic a clogged airway bronchiole. Chemical indicators were added to observe microbial physiology within the tubes. Characterization of sputum samples from seven patients showed variation in pH, respiration, biofilm formation and gas production, indicating that the physiology of CF microbial communities varied among patients. Incubation of homogenized tissues from an explant CF lung mirrored responses of a Pseudomonas aeruginosa pure culture, supporting evidence that end-stage lungs are dominated by this pathogen. Longitudinal sputum samples taken through two exacerbation events in a single patient showed that a two-unit drop in pH and a 30% increase in gas production occurred in the tubes prior to exacerbation, which was reversed with antibiotic treatment. Microbial community profiles obtained through amplification and sequencing of the 16S rRNA gene showed that fermentative anaerobes became more abundant during exacerbation and were then reduced during treatment where P. aeruginosa became the dominant bacterium. Results from the WinCF experiments support the model where two functionally different CF microbial communities exist, the persistent Climax Community and the acute Attack Community. Fermentative anaerobes are hypothesized to be the core members of the Attack Community and production of acidic and gaseous products from fermentation may drive developing exacerbations. Treatment targeting the Attack Community may better resolve exacerbations and resulting lung damage.

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Section: Sources Of the Fermentative Responsesupporting

confidence: 78%

A Winogradsky-based culture system shows an association between microbial fermentation and cystic fibrosis exacerbation

et al. 2014

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“…Surprisingly, the catabolome as monitored by the Biolog phenotype arrays shows only loss of function (Fig. S2), which is paradoxical, taking the abundance of, for example, amino acids in the sputum into consideration (33). We hypothesize that the airway mucus and the surrounding environment is rich in a variety of nutrients and that the competition for these from other infecting species is marginal, providing ample opportunities for alternative feeding by P. aeruginosa.…”

Section: Resultsmentioning

confidence: 96%

Evolutionary dynamics of bacteria in a human host environment

Yang

Jelsbak

Marvig

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

318

413

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Laboratory evolution experiments have led to important findings relating organism adaptation and genomic evolution. However, continuous monitoring of long-term evolution has been lacking for natural systems, limiting our understanding of these processes in situ. Here we characterize the evolutionary dynamics of a lineage of a clinically important opportunistic bacterial pathogen, Pseudomonas aeruginosa , as it adapts to the airways of several individual cystic fibrosis patients over 200,000 bacterial generations, and provide estimates of mutation rates of bacteria in a natural environment. In contrast to predictions based on in vitro evolution experiments, we document limited diversification of the evolving lineage despite a highly structured and complex host environment. Notably, the lineage went through an initial period of rapid adaptation caused by a small number of mutations with pleiotropic effects, followed by a period of genetic drift with limited phenotypic change and a genomic signature of negative selection, suggesting that the evolving lineage has reached a major adaptive peak in the fitness landscape. This contrasts with previous findings of continued positive selection from long-term in vitro evolution experiments. The evolved phenotype of the infecting bacteria further suggests that the opportunistic pathogen has transitioned to become a primary pathogen for cystic fibrosis patients.

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“…However, recent genetic studies using diverse P. aeruginosa clinical isolates reported that adaptive mutations in the lasR gene occur spontaneously in the course of chronic airway infection in CF (9,12,19,42). Phenotype on April 7, 2019 by guest http://iai.asm.org/ changes conferred on P. aeruginosa by these mutations include (i) facilitated growth on amino acids present in relatively large quantities in CF airways (1,12), (ii) an efficient shift to an anaerobic mode of growth using nitrate over oxygen (20), and (iii) elevated antibiotic resistance (12,20). Therefore, frequent identification of lasR mutants suggests that P. aeruginosa may acquire the mutation to increase its survival fitness in a harsh host environment at the expense of its ability to regulate QS-mediated virulence properties.…”

Section: Discussionmentioning

confidence: 99%

Anaerobiosis-Induced Loss of Cytotoxicity Is Due to Inactivation of Quorum Sensing in Pseudomonas aeruginosa

et al. 2011

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Pseudomonas aeruginosa, an opportunistic pathogen of clinical importance, causes chronic airway infections in patients with cystic fibrosis (CF). Current literature suggests that pockets with reduced oxygen tension exist in the CF airway mucus. However, virulence features of this opportunistic pathogen under such conditions are largely unknown. Cell-free supernatant of the standard laboratory P. aeruginosa strain PAO1 obtained from anaerobic culture, but not aerobic culture, failed to kill A549 human airway epithelial cells. Further investigation revealed that this reduced cytotoxicity upon anaerobiosis was due to the suppressed secretion of elastase, a virulence factor controlled by P. aeruginosa quorum sensing (QS). Both a lacZ-reporter fusion assay and quantitative real-time PCR (RT-PCR) analysis demonstrated that transcription of the elastase-encoding lasB gene was substantially decreased during anaerobic growth compared with aerobic growth. Moreover, transcription of other genes controlled by the LasI/R QS system, such as rhlR, vqsR, mvfR, and rsaL, was also repressed under the same anaerobic growth conditions. Importantly, synthesis of 3-oxo-C 12 -HSL (PAI-1), an autoinducer molecule that mediates induction of the LasI/R QS system, was >22-fold decreased during anaerobic growth while C 4 -HSL (PAI-2), which mediates RhlI/R QS, was nondetectable under the same growth conditions. Transcription of the lasB gene was restored by exogenous supplementation with autoinducers, with PAI-2 more effective than PAI-1 or Pseudomonas quinolone signal (PQS) at restoring transcription of the lasB gene. Together, these results suggest that anaerobiosis deprives P. aeruginosa of the ability to regulate its virulence via QS and this misregulation attenuates the pathogenic potential of this important pathogen.

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The high amino-acid content of sputum from cystic fibrosis patients promotes growth of auxotrophic Pseudomonas aeruginosa

Cited by 126 publications

References 22 publications

A Winogradsky-based culture system shows an association between microbial fermentation and cystic fibrosis exacerbation

A Winogradsky-based culture system shows an association between microbial fermentation and cystic fibrosis exacerbation

Evolutionary dynamics of bacteria in a human host environment

Anaerobiosis-Induced Loss of Cytotoxicity Is Due to Inactivation of Quorum Sensing in Pseudomonas aeruginosa

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