Toward implementation of quorum sensing autoinducers as biomarkers for infectious disease states

Development of an analytical method to quantify N-acyl-homoserine lactones in bacterial cultures, river water, and treated wastewater

N-Acyl-homoserine lactones (AHL) play a major role in the communication of Gram-negative bacteria. They influence processes such as biofilm formation, swarming motility, and bioluminescence in the aquatic environment. A comprehensive analytical method was developed to elucidate the "chemical communication" in pure bacterial cultures as well as in the aquatic environment and engineered environments with biofilms. Due to the high diversity of AHLs and their low concentrations in water, a sensitive and selective LC-ESI-MS/MS method combined with solid-phase extraction was developed for 34 AHLs, optimized and validated to quantify AHLs in bacterial conditioned medium, river water, and treated wastewater. Furthermore, the developed method was optimized in terms of enrichment volume, internal standards, limits of detection, and limits of quantification in several matrices. An unanticipated variety of AHLs was detected in the culture media of Pseudomonas aeruginosa (in total 8 AHLs), Phaeobacter gallaeciensis (in total 6 AHLs), and Methylobacterium mesophilicum (in total 15 AHLs), which to our knowledge have not been described for these bacterial cultures so far. Furthermore, AHLs were detected in river water (in total 5 AHLs) and treated wastewater (in total 3 AHLs). Several detected AHLs were quantified (in total 24) using a standard addition method up to 7.3±1.0 µg/L 3-Oxo-C12-AHL (culture media of P. aeruginosa).

Pseudomonas aeruginosa and Staphylococcus aureus virulence factors as biomarkers of infection

The gold standard for the diagnosis of bacterial infections in clinical samples is based on culture tests that are time-consuming and labor-intense. For these reasons, an extraordinary effort has been made to identify biomarkers as the tools for sensitive, rapid and accurate identification of pathogenic microorganisms. Moreover, biomarkers have been tested to distinguish colonization from infection, monitor disease progression, determine the clinical status of patients or predict clinical outcomes. This mini-review describes Pseudomonas aeruginosa and Staphylococcus aureus biomarkers, which contribute to pathogenesis and have been used in culture-independent bacterial identification directly from patient samples.

N-3-oxododecanoyl homoserine lactone exacerbates endothelial cell death by inducing receptor-interacting protein kinase 1-dependent apoptosis

Endothelial dysfunction is associated with the initiation of sepsis-associated organ failure. Bacterial quorum-sensing molecules act as pathogen-associated molecular patterns; however, the effects of quorum-sensing molecules on endothelial cells remain less understood. This study investigated the molecular mechanisms of quorum-sensing molecule-induced cell death and their interaction with lipopolysaccharide (LPS) in human umbilical vein endothelial cells. Endothelial cells were treated with N-3-oxododecanoyl homoserine lactone (3OC12-HSL) and LPS derived from Pseudomonas aeruginosa. Treatment with 3OC12-HSL reduced cell viability in a dose-dependent manner, and cotreatment with 3OC12-HSL and LPS enhanced cell death. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling assay revealed an increase in apoptotic cell death following 3OC12-HSL treatment; furthermore, cotreatment with 3OC12-HSL and LPS enhanced apoptosis. Western blotting revealed that treatment with 3OC12-HSL activated the receptor-interacting protein kinase 1 (RIPK1) pathway, leading to an increase in the levels of cleaved caspase 8 and 3. In addition, we found that treatment with necrostatin-1, an RIPK1 inhibitor, reduced cell death and ameliorated the activation of the RIPK1-dependent apoptotic pathway in 3OC12-HSL-treated cells. In conclusion, 3OC12-HSL induced endothelial cell apoptosis via the activation of the RIPK1 pathway, independent of LPS toxicity. Inhibition of RIPK1 may act as a therapeutic option for preserving endothelial cell integrity in patients with sepsis by disrupting the mechanism by which quorum-sensing molecules mediate their toxicity.

Detection of gut microbiota and pathogen produced N-acyl homoserine in host circulation and tissues

Recent studies suggest that quorum-sensing molecules may play a role in gut microbiota-host crosstalk. However, whether microbiota produces quorum-sensing molecules and whether those molecules can trans-kingdom transport to the host are still unknown. Here, we develop a UPLC-MS/MS-based assay to screen the 27 N-acyl homoserine lactones (AHLs) in the gut microbiota and host. Various AHL molecules are exclusively detected in the cecal contents, sera and livers from conventionally-raised mice but cannot be detected in germ-free mice. Pathogen-produced C4-HSL is detected in the cecal contents and sera of Citrobacter rodentium (C. rodentium)-infected mice, but not found in uninfected controls. Moreover, C. rodentium infection significantly increases the level of multiple AHL molecules in sera. Our findings demonstrate that both commensal and pathogenic bacteria, can produce AHLs that can be detected in host bodies, suggesting that quorum-sensing molecules could be a group of signaling molecules in trans-kingdom microbiota-host crosstalk.

Rational design of a functionalized aluminum metal-organic framework as a turn-off fluorescence sensor for α-ketoglutaric acid

A 3D metal-organic framework (MOF) called Al-DUT-5-N2H3 (1) (DUT: Dresden University of Technology) was prepared hydrothermally using Al(iii) salt and a hydrazinyl functionalized linker called 2-hydrazinyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid (BPDC-N2H3). Material 1 was successfully characterized by X-ray powder diffraction (XRPD), FT-IR spectroscopy, N2 sorption (BET) experiment, thermogravimetric analysis (TGA), EDX and FE-SEM analyses. The activated form of material 1 (called 1') was achieved by a direct heating process. Material 1' was successfully employed for the solution-phase fluorescence detection of α-ketoglutaric acid (α-KG). It showed high detection performance even when there were other competitive analytes present in the mixture. Material 1' is the first MOF-based fluorescent turn-off sensor for the detection of α-KG. The response time for α-KG is exceptionally low (60 s) as compared to any other reported α-KG sensor. The limit of detection (LOD) was found to be 0.61 μM, which is far better as compared to any other reported sensor for α-KG to date. The mechanism for α-KG sensing was thoroughly investigated and proposed to be PET (photoinduced electron transfer) process by TD-DFT (time-dependent DFT) calculations.

Targeted and untargeted quantification of quorum sensing signalling molecules in bacterial cultures and biological samples via HPLC-TQ MS techniques

Quorum sensing (QS) is the ability of some bacteria to detect and to respond to population density through signalling molecules. QS molecules are involved in motility and cell aggregation mechanisms in diseases such as sepsis. Few biomarkers are currently available to diagnose sepsis, especially in high-risk conditions. The aim of this study was the development of new analytical methods based on liquid chromatography-mass spectrometry for the detection and quantification of QS signalling molecules, including N-acyl homoserine lactones (AHL) and hydroxyquinolones (HQ), in biofluids. Biological samples used in the study were Pseudomonas aeruginosa bacterial cultures and plasma from patients with sepsis. We developed two MS analytical methods, based on neutral loss (NL) and product ion (PI) experiments, to identify and characterize unknown AHL and HQ molecules. We then established a multiple-reaction-monitoring (MRM) method to quantify specific QS compounds. We validated the HPLC-MS-based approaches (MRM-NL-PI), and data were in accord with the validation guidelines. With the NL and PI MS-based methods, we identified and characterized 3 and 13 unknown AHL and HQ compounds, respectively, in biological samples. One of the newly found AHL molecules was C12-AHL, first quantified in Pseudomonas aeruginosa bacterial cultures. The MRM quantitation of analytes in plasma from patients with sepsis confirmed the analytical ability of MRM for the quantification of virulence factors during sepsis.

Inhibitory effects of novel 1,4-disubstituted 1,2,3-triazole compounds on quorum-sensing of P. aeruginosa PAO1

Quorum sensing (QS) inhibition is an essential strategy to combat bacterial infection. Previously, we have synthesized a series of thymidine derivatives bearing isoxazole and 1,2,3-triazole rings (TITL). Herein, the inhibitory effects of TITL on QS of Pseudomonas aeruginosa PAO1 were evaluated. In vitro results demonstrated that TITL effectively inhibited biofilm formation and reduced the virulence factors of P. aeruginosa PAO1. In combination with antibiotics, our TITL compounds significantly prolonged the lifespans of Caenorhabditis elegans N2 nematodes that were infected with P. aeruginosa PAO1 in vivo. In conclusion, TITL compounds are promising candidates for the treatment of antibiotic-resistant P. aeruginosa PAO1.

Detection of Quorum-Sensing Molecules for Pathogenic Molecules Using Cell-Based and Cell-Free Biosensors

Since the discovery and subsequent use of penicillin, antibiotics have been used to treat most bacterial infections in the U.S. Over time, the repeated prescription of many antibiotics has given rise to many antibiotic-resistant microbes. A bacterial strain becomes resistant by horizontal gene transfer, where surviving microbes acquire genetic material or DNA fragments from adjacent bacteria that encode for resistance. In order to avoid significant bacterial resistance, novel and target therapeutics are needed. Further advancement of diagnostic technologies could be used to develop novel treatment strategies. The use of biosensors to detect quorum-sensing signaling molecules has the potential to provide timely diagnostic information toward mitigating the multidrug-resistant bacteria epidemic. Resistance and pathogenesis are controlled by quorum-sensing (QS) circuits. QS systems secrete or passively release signaling molecules when the bacterial concentration reaches a certain threshold. Signaling molecules give an early indication of virulence. Detection of these compounds in vitro or in vivo can be used to identify the onset of infection. Whole-cell and cell-free biosensors have been developed to detect quorum-sensing signaling molecules. This review will give an overview of quorum networks in the most common pathogens found in chronic and acute infections. Additionally, the current state of research surrounding the detection of quorum-sensing molecules will be reviewed. Followed by a discussion of future works toward the advancement of technologies to quantify quorum signaling molecules in chronic and acute infections.

Vertebrate odorant binding proteins as antimicrobial humoral components of innate immunity for pathogenic microorganisms

The bacterium Pseudomonas aeruginosa (PA) and the yeast Candida albicans (CA) are pathogens that cohabit the mucosa of the respiratory tracts of animals and humans. Their virulence is largely determined by chemical communication driven by quorum sensing systems (QS), and the cross perception of their quorum sensing molecules (QSM) can modulate the prevalence of one microorganism over the other. Aiming to investigate whether some of the protein components dissolved in the mucus layering the respiratory mucosa might interfere with virulence and cross-communication of these, and eventually other microorganisms, ligand binding assays were carried out to test the scavenging potential of the bovine and porcine forms of the Lipocalin odorant binding protein (OBP) for several QSMs (farnesol, and acylhomoserine lactones), and for pyocyanin, a toxin produced by PA. In addition, the direct antimicrobial activity of the OBPs was tested by time kill assay (TKA) against CA, PA and other bacteria and yeasts. The positivity of all the ligand binding assays and the antimicrobial activity determined for CA, and for some of the other microorganisms tested, let hypothesize that vertebrate OBPs might behave as humoral components of innate immunity, active against pathogenic bacteria and fungi. In addition, TKAs with mutants of bovine OBP with structural properties different from those of the native form, and with OBP forms tagged with histidines at the amino terminal, provided information about the mechanisms responsible of their antimicrobial activity and suggested possible applications of the OBPs as alternative or co-adjuvants to antibiotic therapeutic treatments.

Establishment of LCMS Based Platform for Discovery of Quorum Sensing Inhibitors: Signal Detection in Pseudomonas aeruginosa PAO1

Targeting the main three networking systems, viz. Las, RhI, and PQS, via natural quenchers is a new ray of hope for combating the persistent behavior of Pseudomonas aeruginosa. In the bacterial chemical vocabulary pyocyanin, N-AHLs and rhamnolipids are the main keywords, which are responsible for the social and nomadic behavior of P. aeruginosa. In the present work, LC-MS based real-time qualitative and quantitative analysis of pyocyanin, green phenazine, N-AHLs, and rhamnolipids were performed on P. aeruginosa PAO1. The quantitative analysis indicates that the production of pyocyanin and NHSLs increases with time while the production of rhamnolipids discontinued after 16 h. This indicates the emergence of persisters in the medium instead of planktonic cells. Rhamnolipids acting as a surfactant enhances the motility of the bacterial cells, whereas the pyocyanin is responsible for the biofilm formation. In a microtiter plate based assay, an effect of capsaicin and 6-gingerol was recorded. In the presence of capsaicin and 6-gingerol, a substantial decrease in the production of rhamnolipids, phenazine, quinolone, and N-AHLs was observed. Most interestingly, the 6-gingerol treatment led to a drastic decrease of rhamnolipids, phenazine, quinolone, and N-AHLs versus capsaicin. These studies demonstrate the effectiveness of the capsaicin and 6-gingerol on Las, PQS, and Rhl circuits in a bacterium in order to understand the persistent and social behavior. Here, we are reporting LC-MS/MS based qualitative and quantitative analysis of QS molecules by taking a low volume of culture (up to 200 μL). This method can be used as a platform to screen the new antivirulence agents for fighting the resistant behavior of P. aeruginosa during biofilm formation.

A Cell-Free Biosensor for Detecting Quorum Sensing Molecules in P. aeruginosa-Infected Respiratory Samples

Synthetic biology designed cell-free biosensors are a promising new tool for the detection of clinically relevant biomarkers in infectious diseases. Here, we report that a modular DNA-encoded biosensor in cell-free protein expression systems can be used to measure a bacterial biomarker of Pseudomonas aeruginosa infection from human sputum samples. By optimizing the cell-free system and sample extraction, we demonstrate that the quorum sensing molecule 3-oxo-C12-HSL in sputum samples from cystic fibrosis lungs can be quantitatively measured at nanomolar levels using our cell-free biosensor system, and is comparable to LC-MS measurements of the same samples. This study further illustrates the potential of modular cell-free biosensors as rapid, low-cost detection assays that can inform clinical practice.

Albumin Inhibits Pseudomonas aeruginosa Quorum Sensing and Alters Polymicrobial Interactions

Polymicrobial interactions are complex and can influence the course of an infection, as is the case when two or more species exhibit a synergism that produces a disease state not seen with any of the individual species alone. Cell-to-cell signaling is key to many of these interactions, but little is understood about how the host environment influences polymicrobial interactions or signaling between bacteria. Chronic wounds are typically polymicrobial, with Staphylococcus aureus and Pseudomonas aeruginosa being the two most commonly isolated species. While P. aeruginosa readily kills S. aureusin vitro, the two species can coexist for long periods together in chronic wound infections. In this study, we investigated the ability of components of the wound environment to modulate interactions between P. aeruginosa and S. aureus We demonstrate that P. aeruginosa quorum sensing is inhibited by physiological levels of serum albumin, which appears to bind and sequester some homoserine lactone quorum signals, resulting in the inability of P. aeruginosa to produce virulence factors that kill S. aureus These data could provide important clues regarding the virulence of P. aeruginosa in albumin-depleted versus albumin-rich infection sites and an understanding of the nature of friendly versus antagonistic interactions between P. aeruginosa and S. aureus.

Peptides as Quorum Sensing Molecules: Measurement Techniques and Obtained Levels In vitro and In vivo

The expression of certain bacterial genes is regulated in a cell-density dependent way, a phenomenon called quorum sensing. Both Gram-negative and Gram-positive bacteria use this type of communication, though the signal molecules (auto-inducers) used by them differ between both groups: Gram-negative bacteria use predominantly N-acyl homoserine lacton (AHL) molecules (autoinducer-1, AI-1) while Gram-positive bacteria use mainly peptides (autoinducer peptides, AIP or quorum sensing peptides). These quorum sensing molecules are not only involved in the inter-microbial communication, but can also possibly cross-talk directly or indirectly with their host. This review summarizes the currently applied analytical approaches for quorum sensing identification and quantification with additionally summarizing the experimentally found in vivo concentrations of these molecules in humans.

Strategies for inhibiting quorum sensing

The ability of bacterial cells to synchronize their behaviour through quorum sensing (QS) regulatory networks enables bacterial populations to mount co-operative responses against competing micro-organisms and host immune defences and to adapt to environmental challenges. Since QS controls the ability of many pathogenic bacteria to cause disease, it is an attractive target for novel antibacterial agents that control infection through inhibition of virulence and by rendering biofilms more susceptible to conventional antibiotics and host clearance pathways. QS systems provide multiple druggable molecular targets for inhibitors (QSIs) that include the enzymes involved in QS signal molecule biosynthesis and the receptors involved in signal transduction. Considerable advances in our understanding of the chemical biology of QS systems and their inhibition have been made, some promising QS targets structurally characterized, QSI screens devised and inhibitors identified. However, much more work is required before any QSI ‘hits’ with the appropriate pharmacological and pharmacokinetic properties can enter human clinical trials. Indeed, the relative efficacy of QSIs alone or as prophylactics or therapeutics or as adjuvants in combination with conventional antibiotics still needs to be extensively evaluated in vivo. Particular attention must be given to the measurement of successful QSI therapy outcomes with respect to bacterial clearance, immune response and pathophysiology. Currently, our understanding of the potential of QS as a promising antibacterial target suggests that it is likely to be of value with respect to a limited number of major pathogens.

5-Hydroxyethyl-3-tetradecanoyltetramic acid represents a novel treatment for intravascular catheter infections due to Staphylococcus aureus

Objectives

Biofilm infections of intravascular catheters caused by Staphylococcus aureus may be treated with catheter lock solutions (CLSs). Here we investigated the antibacterial activity, cytotoxicity and CLS potential of 5-hydroxyethyl-3-tetradecanoyltetramic acid (5HE-C14-TMA) compared with the related compounds 3-tetradecanoyltetronic (C14-TOA) and 3-tetradecanoylthiotetronic (C14-TTA), which are variants of quorum sensing signalling molecules produced by Pseudomonas aeruginosa .

Methods

Antibacterial activity and mechanism of action of 5HE-C14-TMA, C14-TOA and C14-TTA were determined via MIC, bacterial killing, membrane potential and permeability assays. Susceptibility of S. aureus biofilms formed in the presence of plasma in vitro was investigated, MTT cytotoxicity testing was undertaken and cytokine release in human blood upon exposure to 5HE-C14-TMA and/or S. aureus biofilms was quantified. The effectiveness of 5HE-C14-TMA as CLS therapy in vivo was assessed using a rat intravascular catheter biofilm infection model.

Results

MICs of 5HE-C14-TMA, C14-TOA and C14-TTA ranged from 2 to 4 mg/L. 5HE-C14-TMA and C14-TTA were bactericidal; all three compounds perturbed the staphylococcal membrane by increasing membrane permeability, depolarized the transmembrane potential and caused ATP leakage. Cytotoxicity and haemolytic activity were compound and target cell type-dependent. 5HE-C14-TMA reduced S. aureus biofilm viability in a dose-dependent manner in vitro and in vivo and did not trigger release of cytokines in human blood, but inhibited the high levels of IL-8 and TNF-α induced by S. aureus biofilms.

Conclusions

5HE-C14-TMA, C14-TOA and C14-TTA are membrane-active agents. 5HE-C14-TMA was the most potent, eradicating S. aureus biofilms at 512-1024 mg/L both in vitro and in vivo as a CLS.

Innate Immune Signaling Activated by MDR Bacteria in the Airway

Health care-associated bacterial pneumonias due to multiple-drug resistant (MDR) pathogens are an important public health problem and are major causes of morbidity and mortality worldwide. In addition to antimicrobial resistance, these organisms have adapted to the milieu of the human airway and have acquired resistance to the innate immune clearance mechanisms that normally prevent pneumonia. Given the limited efficacy of antibiotics, bacterial clearance from the airway requires an effective immune response. Understanding how specific airway pathogens initiate and regulate innate immune signaling, and whether this response is excessive, leading to host-induced pathology may guide future immunomodulatory therapy. We will focus on three of the most important causes of health care-associated pneumonia, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae, and review the mechanisms through which an inappropriate or damaging innate immune response is stimulated, as well as describe how airway pathogens cause persistent infection by evading immune activation.

Synthesis and analysis of stable isotope-labelled N-acyl homoserine lactones

An easy, reliable manner to make suitable, deuterated standards of AHL-molecules belonging to all three important classes of AHLs is presented, starting from a cheap and commercially available deuterium source.

Recent applications of CE- and HPLC-MS in the analysis of human fluids

The present review intends to cover the literature on the use of CE-/LC-MS for the analysis of human fluids, from 2010 until present. It has been planned to provide an overview of the most recent practical applications of these techniques to less extensively used human body fluids, including, bronchoalveolar lavage fluid, synovial fluid, nipple aspirate, tear fluid, breast fluid, amniotic fluid, and cerumen. Potential pitfalls related to fluid collection and sample preparation, with particular attention to sample clean-up procedures, and methods of analysis, from the research laboratory to a clinical setting will also be addressed. While being apparent that proteomics/metabolomics represent the most prominent approaches for global identification/quantification of putative biomarkers for a variety of human diseases, evidence is also provided of the suitability of these sophisticated techniques for the detection of heterogeneous components carried by these fluids.

Whole-Cell Biosensors as Tools for the Detection of Quorum-Sensing Molecules: Uses in Diagnostics and the Investigation of the Quorum-Sensing Mechanism

Genetically engineered bacterial whole-cell biosensors are powerful tools that take advantage of bacterial proteins and pathways to allow for detection of a specific analyte. These biosensors have been employed for a broad range of applications, including the detection of bacterial quorum-sensing molecules (QSMs). Bacterial QSMs are the small molecules bacteria use for population density-dependent communication, a process referred to as quorum sensing (QS). Various research groups have investigated the presence of QSMs, including N-acyl homoserine lactones (AHLs) and autoinducer-2 (AI-2), in physiological samples in attempts to enhance our knowledge of the role of bacteria and QS in disease states. Continued studies in these fields may allow for improved patient care and therapeutics based upon QSMs. Furthermore, bacterial whole-cell biosensors have elucidated the roles of some antibiotics as QS agonists and antagonists. Graphical Abstract.

Novel Paraoxonase 2-Dependent Mechanism Mediating the Biological Effects of the Pseudomonas aeruginosa Quorum-Sensing Molecule N-(3-Oxo-Dodecanoyl)-L-Homoserine Lactone

Pseudomonas aeruginosa produces N-(3-oxo-dodecanoyl)-L-homoserine lactone (3OC12), a crucial signaling molecule that elicits diverse biological responses in host cells thought to subvert immune defenses. The mechanism mediating many of these responses remains unknown. The intracellular lactonase paraoxonase 2 (PON2) hydrolyzes and inactivates 3OC12 and is therefore considered a component of host cells that attenuates 3OC12-mediated responses. Here, we demonstrate in cell lines and in primary human bronchial epithelial cells that 3OC12 is rapidly hydrolyzed intracellularly by PON2 to 3OC12 acid, which becomes trapped and accumulates within the cells. Subcellularly, 3OC12 acid accumulated within the mitochondria, a compartment where PON2 is localized. Treatment with 3OC12 caused a rapid PON2-dependent cytosolic and mitochondrial pH decrease, calcium release, and phosphorylation of stress signaling kinases. The results indicate a novel, PON2-dependent intracellular acidification mechanism by which 3OC12 can mediate its biological effects. Thus, PON2 is a central regulator of host cell responses to 3OC12, acting to decrease the availability of 3OC12 for receptor-mediated effects and acting to promote effects, such as calcium release and stress signaling, via intracellular acidification.

Pseudomonas aeruginosa quorum sensing molecules correlate with clinical status in cystic fibrosis

Pseudomonas aeruginosa produces quorum sensing signal molecules that are potential biomarkers for infection.

A prospective study of 60 cystic fibrosis patients with chronic P. aeruginosa, who required intravenous antibiotics for pulmonary exacerbations, was undertaken. Clinical measurements and biological samples were obtained at the start and end of the treatment period. Additional data were available for 29 of these patients when they were clinically stable.

Cross-sectionally, quorum sensing signal molecules were detectable in the sputum, plasma and urine of 86%, 75% and 83% patients, respectively. They were positively correlated between the three biofluids. Positive correlations were observed for most quorum sensing signal molecules in sputum, plasma and urine, with quantitative measures of pulmonary P. aeruginosa load at the start of a pulmonary exacerbation. Plasma concentrations of 2-nonyl-4-hydroxy-quinoline (NHQ) were significantly higher at the start of a pulmonary exacerbation compared to clinical stability (p<0.01). Following the administration of systemic antibiotics, plasma 2-heptyl-4-hydroxyquinoline (p=0.02) and NHQ concentrations (p<0.01) decreased significantly.

In conclusion, quorum sensing signal molecules are detectable in cystic fibrosis patients with pulmonary P. aeruginosa infection and are positively correlated with quantitative measures of P. aeruginosa. NHQ correlates with clinical status and has potential as a novel biomarker for P. aeruginosa infection.

P. aeruginosa QS molecules correlate with clinical status in cystic fibrosis and are biomarkers for infectionhttp://ow.ly/MhzZp

Impact of storage conditions on metabolite profiles of sputum samples from persons with cystic fibrosis

BACKGROUND

Although recent studies have begun to elucidate how airway microbial community structure relates to lung disease in cystic fibrosis (CF), microbial community activity and the host's response to changes in this activity are poorly understood. Metabolomic profiling provides a means to investigate microbial activity and human cell activity within diseased airways. However, variables in sample storage and shipping likely affect downstream analyses and standards for sample handling are lacking.

METHODS

We assessed the impact of sample storage conditions on liquid chromatography mass spectrometry analysis of CF sputum samples.

RESULTS

Significant changes in global metabolomic profiles occurred in samples stored at room temperature or at 4°C for longer than one day. Untargeted metabolomic profiles were stable in sputum samples stored at -20°C or -80°C for at least 28 days. Quorum sensing molecules and phenazines, both considered important to the in vivo activity of Pseudomonas during airway infection, were detected after sample storage at room temperature for five days.

CONCLUSIONS

Sputum samples can be stored at -20°C or -80°C for weeks with minimal effect on global metabolomic profiles. This observation provides guidance in designing metabolomic studies that have the potential to deepen our understanding of how airway microbial communities impact lung disease progression in CF.