Elastase Production Research Articles

Study of biological characteristics of Pseudomonas aeruginosa strains isolated from patients with cystic fibrosis and from patients with extra-pulmonary infections

A total of 120 strains of Pseudomonas aeruginosa, isolated from cystic fibrosis (CF) patients (n = 80) and from patients having extra-pulmonary infections (n = 40) were studied regarding the presence of some virulence factors (hemolysin, gelatinase and elastase production) and presence of the algD and algU genes as detected by polymerase chain reaction-PCR. There was not a significant difference for the production of gelatinase and hemolysin between non-mucoid strains from CF patients and other isolates from extra-pulmonary infections and mucoid strains. The production of elastase was found to be significant among these strains. The algD gene was detected by PCR in all studied strains but the algU gene was detected only in 25% of the mucoid strains. Conclusion withdrawn from the results were: (i) hemolysin and gelatinase production although present in many strains of P aeruginosa should not be considered as general virulence factors for the mucoid phenotype but could help in the pathogenic process; (ii) elastase production could be a necessary virulence factor for the initial pathogenesis process; (iii) mucoid and non-mucoid phenotypes could also be expressed according to the host's tissues or environment, and finally, (iv) more than one regulator system for alginate production is probably present in each strain.

Co‐infection of respiratory bacterium with severe acute respiratory syndrome coronavirus induces an exacerbated pneumonia in mice

ABSTRACTSARS‐CoV grows in a variety of tissues that express its receptor, although the mechanism for high replication in the lungs and severe respiratory illness is not well understood. We recently showed that elastase enhances SARS‐CoV infection in cultured cells, which suggests that SARS development may be due to elastase‐mediated, enhanced SARS‐CoV infection in the lungs. To explore this possibility, we examined whether co‐infection of mice with SARS‐CoV and Pp, a low‐pathogenic bacterium which elicits elastase production in the lungs, induces exacerbation of pneumonia. Mice co‐infected with SARS‐CoV and Pp developed severe respiratory disease with extensive weight loss, resulting in a 33∼90% mortality rate. Mice with exacerbated pneumonia showed enhanced virus infection in the lungs and histopathological lesions similar to those found in human SARS cases. Intranasal administration of LPS, another elastase inducer, showed an effect similar to that of Pp infection. Thus, this study shows that exacerbated pneumonia in mice results from co‐infection with SARS‐CoV and a respiratory bacterium that induces elastase production in the lungs, suggesting a possible role for elastase in the exacerbation of pneumonia.

The Intestinal Epithelial Cell Modulates the Effect of Alcohol on Neutrophil Inflammatory Potential

Ethanol (EtOH) intoxication increases posttraumatic infectious complications. EtOH is thought to be immunosuppressive, but the effect of the interaction with the gut and associated microflora on host defense is unknown. We studied the ability of intestinal epithelial cells and bacteria to modulate EtOH effects on polymorphonuclear (PMN) cell function in vitro. Confluent Caco2 monolayers were exposed to 0.1% EtOH with or without Escherichia coli on the apical side of each chamber. Supernatants were collected from the basal side of the chambers and incubated with neutrophils. Controls were incubated with or without 0.1% EtOH alone. Chemotaxis, elastase, and superoxide anion release, and CD11b measurements were undertaken in these neutrophils and compared with controls. Alcohol exhibited differing effects on the inflammatory potential of neutrophils in regards to CD11b expression, elastase production, and superoxide production. Direct effects of EtOH were anti-inflammatory, whereas indirect effects of EtOH on neutrophils modulated by Caco2 cells were proinflammatory. Chemotaxis was significantly reduced when neutrophils were directly treated with alcohol. EtOH direct downregulates PMN inflammatory potential, but its impact of the intestinal epithelial cells produces a proinflammatory microenvironment for PMNs. The interaction of EtOH on the intestinal milieu may lead to neutrophil activation and increased organ injury after trauma in the intoxicated patient.

Modulation of Bacterial Quorum Sensing with Synthetic Ligands: Systematic Evaluation of N-Acylated Homoserine Lactones in Multiple Species and New Insights into Their Mechanisms of Action

Bacteria use a language of low molecular weight ligands to assess their population densities in a process called quorum sensing. This chemical signaling process plays a pivotal role both in the pathogenesis of infectious disease and in beneficial symbioses. There is intense interest in the development of synthetic ligands that can intercept quorum-sensing signals and attenuate these divergent outcomes. Both broad-spectrum and species-selective modulators of quorum sensing hold significant value as small-molecule tools for fundamental studies of this complex cell-cell signaling process and for future biomedical and environmental applications. Here, we report the design and synthesis of focused collections of non-native N-acylated homoserine lactones and the systematic evaluation of these approximately 90 ligands across three Gram-negative bacterial species: the pathogens Agrobacterium tumefaciens and Pseudomonas aeruginosa; the model symbiont Vibrio fischeri. This study is the first to report and compare the activities of a set of ligands across multiple species and has revealed some of the most potent synthetic modulators of quorum sensing to date. Moreover, several of these ligands exhibit agonistic or antagonistic activity in all three species, while other ligands are only active in one or two species. Analysis of the screening data revealed that at least a subset of these ligands modulate quorum sensing via a partial agonism mechanism. We also demonstrate that selected ligands can either inhibit or promote the production of elastase B, a key virulence factor in wild-type P. aeruginosa, depending on their concentrations. Overall, this work provides broad insights into the molecular features required for small-molecule inhibition or activation of quorum sensing in Gram-negative bacteria. In addition, this study has supplied an expansive set of chemical tools for the further investigation of quorum-sensing pathways and responses.

Enhanced production of elastase by Bacillus licheniformis ZJUEL31410: optimization of cultivation conditions using response surface methodology

Sequential methodology based on the application of three types of experimental designs was used to optimize the fermentation conditions for elastase production from mutant strain ZJUEL31410 of Bacillus licheniformis in shaking flask cultures. The optimal cultivation conditions stimulating the maximal elastase production consist of 220 r/min shaking speed, 25 h fermentation time, 5% (v/v) inoculums volume, 25 ml medium volume in 250 ml Erlenmeyer flask and 18 h seed age. Under the optimized conditions, the predicted maximal elastase activity was 495 U/ml. The application of response surface methodology resulted in a significant enhancement in elastase production. The effects of other factors such as elastin and the growth factor (corn steep flour) on elastase production and cell growth were also investigated in the current study. The elastin had no significant effect on enzyme-improved production. It is still not clear whether the elastin plays a role as a nitrogen source or not. Corn steep flour was verified to be the best and required factor for elastase production and cell growth by Bacillus licheniformis ZJUEL31410.

Ribosome Protection Prevents Azithromycin-Mediated Quorum-Sensing Modulation and Stationary-Phase Killing of Pseudomonas aeruginosa

In Pseudomonas aeruginosa, azithromycin has been shown to reduce virulence factor production, to retard biofilm formation, and to exhibit bactericidal effects on stationary-phase cells. In this study we analyzed whether these azithromycin-mediated effects require interaction with the ribosome. We blocked the access of azithromycin to the ribosome in P. aeruginosa PAO1 by expressing the 23S rRNA methylase ErmBP from Clostridium perfringens. Ribosome protection prevented the azithromycin-mediated reduction of elastase and rhamnolipid production, as well as the inhibition of swarming motility. Ribosome protection also prevented the killing of stationary-phase cells, suggesting that the cell-killing effect of azithromycin does not result solely from membrane destabilization. We further show that rhamnolipids are involved in cell killing, probably by increasing the uptake of the hydrophobic azithromycin molecule. These results have important implications for the treatment with azithromycin of patients chronically colonized by P. aeruginosa and might explain the variability in the efficacy of azithromycin treatments.

Neutrophil Elastase Converts Human Immature Dendritic Cells into Transforming Growth Factor-β1-Secreting Cells and Reduces Allostimulatory Ability

During microbial infection, neutrophils (polymorphonuclear leukocytes; PMNs) activate dendritic cells (DCs). However, early reports illustrated that neutrophil-derived mediators may suppress responses to mitogens. In the present study, we investigated the mechanism used by PMNs to modulate the immunostimulatory ability of DCs. Autologous syngeneic PMNs decreased T-cell proliferation induced by allogeneic DCs. Culture supernatant (CS) derived from PMNs also decreased allostimulation ability of immature DCs and increased the expression of transforming growth factor (TGF)-beta1 on DCs. A TGF-beta1 monoclonal antibody, a CD40 monoclonal antibody, or a serine protease inhibitor reversed the effect of PMN CS on DC allostimulatory ability. Furthermore, elastase reproduced the inhibitory effect of PMN CS on DC allostimulatory ability and the TGF-beta1 production. The role of elastase was confirmed by examining PMN CS from two patients with cyclic neutropenia, a disease due to mutations in the neutrophil elastase gene. These PMN CS samples had reduced elastase activity and were unable to increase DC TGF-beta1 production. Moreover, elastase and PMN CS induced IkappaBalpha degradation in DCs. We conclude that PMNs decrease DC allostimulatory ability via production of elastase leading to a switch of immature DCs into TGF-beta1-secreting cells.

Ethanol Effects Proinflammatory State of Neutrophils in Shock

Ethanol (EtOH) intoxication plays an important role in the etiology of traumatic events and has often been described as having immunosuppressive effects. EtOH has been shown to affect intestinal barrier function in prior studies. The ability of gut derived factors on neutrophil function in this setting is unknown. This study looks at the role of ethanol in modulating proinflammatory states in the neutrophil in vitro. Confluent Caco2 monolayers were exposed to 0.1% EtOH and/or Escherichia coli C-25 (EC) under normoxia (21% O(2)) or hypoxia (5% O(2)) followed by normoxic conditions (H/R). Neutrophils were then incubated with the supernatants from the treated cells. Chemotaxis, elastase and superoxide anion release, and CD11b measurements were undertaken in these neutrophils and compared with controls. In the presence of EtOH, Caco2 cells undergoing H/R and bacterial challenge demonstrated a proinflammatory effect on neutrophils. The production of both elastase and superoxide anion were significantly increased from controls. Additionally, the presence of EtOH in Caco2 cells undergoing H/R with/without EC showed a statistically significant increase in CD11b expression and chemotaxis, when compared with controls. EtOH has a proinflammatory role in the activation of neutrophils at the intestinal epithelial cell barrier in shock states. EtOH may play an important role in worsening septic complication in severely traumatized patients via dysregulation of neutrophils.

CD8+ T Cells Are Required for Inflammation and Destruction in Cigarette Smoke-Induced Emphysema in Mice

Increased numbers of T lymphocytes are observed in the lungs of patients with chronic obstructive pulmonary disease, but their role in the disease process is not known. We investigated the role of CD8+ T cells in inflammatory cell recruitment and lung destruction in a cigarette smoke-induced murine model of emphysema. In contrast to wild-type C57BL/6J mice that displayed macrophage, lymphocyte, and neutrophil recruitment to the lung followed by emphysema in response to cigarette smoke, CD8+ T cell-deficient (CD8-/-) mice had a blunted inflammatory response and did not develop emphysema when exposed to long-term cigarette smoke. Further studies supported a pathogenetic pathway whereby the CD8+ T cell product, IFN-gamma-inducible protein-10, induces production of macrophage elastase (matrix metalloproteinase 12) that degrades elastin, both causing lung destruction directly and generating elastin fragments that serve as monocyte chemokines augmenting macrophage-mediated lung destruction. These studies demonstrate a requirement for CD8+ T cells for the development of cigarette smoke-induced emphysema and they provide a unifying pathway whereby CD8+ T cells are a central regulator of the inflammatory network in chronic obstructive pulmonary disease.

Autoinducer production and quorum-sensing dependent phenotypes of Pseudomonas aeruginosa vary according to isolation site during colonization of intubated patients

BackgroundPseudomonas aeruginosa frequently colonizes and is responsible for severe ventilator-associated pneumonia in intubated patients. A quorum-sensing (QS) circuit, depending on the production of the two QS-signaling molecules (autoinducers, AIs) 3-oxo-C12-HSL and C4-HSL, regulates the production by P. aeruginosa of several virulence factors and is required for biofilm formation. Therefore QS-inhibition has been suggested as a new target for preventive and/or therapeutic strategies. However the precise role of QS during colonization and subsequent infections of intubated patients remains unclear.ResultsWe wondered whether QS is active during colonization of intubated patients, and whether P. aeruginosa isolates growing inside the biofilm covering the intubation devices and those resident in the lungs of colonized patients differ in their QS-dependent phenotypes. We collected the intubation devices of eight patients colonized by P. aeruginosa. We detected 3-oxo-C12-HSL on eight, and C4-HSL on six of these devices. In three of these patients we also obtained P. aeruginosa isolates from tracheal aspirates at the time of extubation (n = 18), as well as isolates from the intubation devices (n = 25). We genotyped these isolates, quantified their AIs production, and determined three QS-dependent phenotypes (adherence capacity, biofilm and elastase production). The production of 3-oxo-C12-HSL was consistently increased for isolates from the intubation devices, whereas the production of C4-HSL was significantly higher for isolates from tracheal aspirates. Isolates from tracheal aspirates produced significantly higher amounts of elastase but less biofilm, and had a marginally reduced adhesion capacity than isolates from the intubation devices. Levels of 3-oxo-C12-HSL and elastase production correlated statistically for tracheal intubation isolates, whereas levels of 3-oxo-C12-HSL production and adhesion ability, as well as biofilm production, correlated weakly amongst intubation device isolates.ConclusionOur findings demonstrate that autoinducers are produced during the colonization of intubated patients by P. aeruginosa. The microenvironment, in which P. aeruginosa grows, may select for bacteria with different capacities to produce autoinducers and certain QS-dependent phenotypes. QS-inhibition might therefore affect differently isolates growing inside the biofilm covering intubation devices and those resident in the lungs.

Corneal Virulence of Pseudomonas aeruginosa Elastase B and Alkaline Protease Produced by Pseudomonas putida

Purpose: To measure the specific virulence contributions of two Pseudomonas aeruginosa proteases, elastase B and alkaline protease, when expressed separately by Pseudomonas putida in a rabbit model of bacterial keratitis. Methods: P. putida KT2440 was transformed with plasmids that enabled the extracellular production of either elastase or alkaline protease. Protease expression was confirmed by zymography and immunoblotting. P. putida expressing elastase, alkaline protease, or vector alone was injected intrastromally (10 colony forming units [CFU]) into rabbit corneas (n = 6). Infected eyes were graded by slit-lamp examination (SLE) at 20, 24, 28, and 32 hr postinfection (PI). Rabbits were sacrificed at 33 hr PI, and the log CFU (±SEM) per cornea was determined. Results: SLE scores for eyes infected with P. putida producing elastase were significantly higher than those infected with vector alone at all time points (p ≤ 0.008). SLE scores for eyes infected with P. putida producing alkaline protease were not significantly higher than the control (p ≥ 0.1), but small erosions formed in 33% of corneas. At both 24 and 28 hr PI, the SLE scores for corneas infected with P. putida producing elastase were significantly higher than those infected with P. putida producing alkaline protease (p ≤ 0.002). Conclusions: Elastase production by P. putida caused significant increases in SLE scores whereas expression of alkaline protease caused limited corneal erosions. This suggests that the production of elastase during P. aeruginosa keratitis enhances ocular pathology, whereas alkaline protease production contributes to limited corneal erosion.

Transcriptional Regulatory Cascade for Elastase Production in Vibrio vulnificus

Vibrio vulnificus causes diseases through actions of various virulence factors, including the elastase encoded by the vvpE gene. Through transposon mutagenesis of V. vulnificus, vvpE expression was shown to be increased by luxO mutation. Since the vvpE gene is known to be positively regulated by SmcR via direct binding to the vvpE promoter, the role of LuxO in smcR expression was investigated. The luxAB-transcriptional fusions containing different lengths of the smcR promoter region indicated that the smcR transcription was negatively regulated by LuxO and that a specific upstream region of the smcR gene was required for this repression. Since LuxO is a known member of positive regulators, the negative regulation of smcR transcription by LuxO prompted us to identify the factor(s) linking LuxO and smcR transcription. LuxT was isolated in a ligand fishing experiment using the smcR upstream region as bait, and smcR expression was increased by luxT mutation. Recombinant LuxT bound to a specific upstream region of the smcR gene, -154 to -129 relative to the smcR transcription start site. The expression of luxT was positively regulated by LuxO, and the luxT promoter region contained a putative LuxO-binding site. Mutagenesis of the LuxO-binding site in the luxT promoter region resulted in a loss of transcriptional control by LuxO. Therefore, this study demonstrates a transcriptional regulatory cascade for elastase production, where LuxO activates luxT transcription and LuxT represses smcR transcription.

Expression of the las and rhl quorum-sensing systems in clinical isolates of Pseudomonas aeruginosa does not correlate with efflux pump expression or antimicrobial resistance

Quorum-sensing systems regulate expression of several virulence factors and may affect the MexAB-OprM efflux system in Pseudomonas aeruginosa. This study investigated the relationship between two quorum-sensing systems, efflux pump MexAB-OprM expression and antimicrobial resistance in 33 clinical isolates of P. aeruginosa. Expression of the quorum-sensing regulatory genes lasR and rhlR was assessed by real time RT-PCR. The autoinducer synthetase genes lasI and rhlI and the regulatory genes mexT and mexS were characterized by DNA sequencing. Production of pyocyanin and elastase in each of the isolates was also determined. While there was a significant correlation between expression of the quorum-sensing regulatory genes and production of pyocyanin and elastase, there was no correlation with expression of mexA or with antimicrobial resistance. There were no mutations in lasI, rhlI, mexT or mexS that correlated with quorum-sensing expression. Increased activity of two quorum-sensing systems in P. aeruginosa does not contribute to increased mexA expression or antimicrobial resistance.

Effets anti-inflammatoires des macrolides

Besides their antibiotic effect, C14 and C15 macrolides exhibit immunomodulatory properties which can have therapeutic applications for chronic inflammation of the airways. In vitro studies have demonstrated the anti-inflammatory effects of macrolides: decreased productions of IL-6, IL-8, TNF alpha, chemotactism of polymorphonuclear neutrophils. Cell activity is modified with reduced production of elastase and oxidizing agents. These immunomodulator effects appear to result from an interaction with transcription factors which regulate the expression of cell gens. In addition, they lead to a modified bronchial mucosal secretion and have an action on the biofilm and the pseudomonas pilis. Their clinical activity has been demonstrated in panbronchiolitis and is in favor of use in cystic fibrosis. Use of macrolides should be carefully monitored in the event of bronchectasia, COPD, asthma, or chronic rhinosinusitis.

Functional Genetic Analysis Reveals a 2-Alkyl-4-Quinolone Signaling System in the Human Pathogen Burkholderia pseudomallei and Related Bacteria

Pseudomonas aeruginosa synthesizes diverse 2-alkyl-4(1H)-quinolones (AHQs), including the signaling molecule 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS), via the pqsABCDE locus. By examining the genome databases, homologs of the pqs genes were identified in other bacteria. However, apart from P. aeruginosa, only Burkholderia pseudomallei and B. thailandensis contained a complete pqsA-E operon (termed hhqA-E). By introducing the B. pseudomallei hhqA and hhqE genes into P. aeruginosa pqsA and pqsE mutants, we show that they are functionally conserved and restore virulence factor and PQS production. B. pseudomallei, B. thailandensis, B. cenocepacia, and P. putida each produced 2-heptyl-4(1H)-quinolone (HHQ), but not PQS. Mutation of hhqA in B. pseudomallei resulted in the loss of AHQ production, altered colony morphology, and enhanced elastase production, which was reduced to parental levels by exogenous HHQ. These data reveal a role for AHQs in bacterial cell-to-cell communication beyond that seen in P. aeruginosa.

Effect of a Polymorphonuclear Elastase Inhibitor (Sivelestat Sodium) on Acute Lung Injury After Cardiopulmonary Bypass: Findings of a Double-Blind Randomized Study

We evaluated the effect of sivelestat sodium (SiV), a novel synthesized polymorphonuclear (PMN) elastase inhibitor, on acute lung injury (ALI) caused by cardiopulmonary bypass (CPB). Fourteen patients who underwent cardiopulmonary surgery using CPB, followed by the development of both systemic inflammatory response syndrome (SIRS) and ALI, were treated with either 0.2 mg/kg per hour SiV (SiV group, n = 7) or saline (control group, n = 7) for 4 days from the time of arrival in the intensive care unit. The SiV group had a significantly lower ratio of serum PMN elastase and interleukin (IL)-8, a significantly lower ratio of the respiratory index, and a significantly higher ratio of PaO(2)/FiO(2) after 24 h of treatment than the control group. Sivelestat sodium suppressed the production of PMN elastase and IL-8, resulting in improved respiratory function in patients with ALI caused by CPB.

Quorum Quenching by an N -Acyl-Homoserine Lactone Acylase from Pseudomonas aeruginosa PAO1

The virulence of the opportunistic human pathogen Pseudomonas aeruginosa PAO1 is controlled by an N-acyl-homoserine lactone (AHL)-dependent quorum-sensing system. During functional analysis of putative acylase genes in the P. aeruginosa PAO1 genome, the PA2385 gene was found to encode an acylase that removes the fatty acid side chain from the homoserine lactone (HSL) nucleus of AHL-dependent quorum-sensing signal molecules. Analysis showed that the posttranslational processing of the acylase and the hydrolysis reaction type are similar to those of the beta-lactam acylases, strongly suggesting that the PA2385 protein is a member of the N-terminal nucleophile hydrolase superfamily. In a bioassay, the purified acylase was shown to degrade AHLs with side chains ranging in length from 11 to 14 carbons at physiologically relevant low concentrations. The substituent at the 3' position of the side chain did not affect activity, indicating broad-range AHL quorum-quenching activity. Of the two main AHL signal molecules of P. aeruginosa PAO1, N-butanoyl-l-homoserine lactone (C4-HSL) and N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C12-HSL), only 3-oxo-C12-HSL is degraded by the enzyme. Addition of the purified protein to P. aeruginosa PAO1 cultures completely inhibited accumulation of 3-oxo-C12-HSL and production of the signal molecule 2-heptyl-3-hydroxy-4(1H)-quinolone and reduced production of the virulence factors elastase and pyocyanin. Similar results were obtained when the PA2385 gene was overexpressed in P. aeruginosa. These results demonstrate that the protein has in situ quorum-quenching activity. The quorum-quenching AHL acylase may enable P. aeruginosa PAO1 to modulate its own quorum-sensing-dependent pathogenic potential and, moreover, offers possibilities for novel antipseudomonal therapies.

Burn Injury Exacerbates Hemodynamic and Metabolic Responses in Rats with Polymicrobial Sepsis

The most common and life-threatening complication of severe burn injury is infection, which often results in multiple organ failure (MOF). However, the mechanism of development of MOF after burn injury associated with infection is not fully understood. Our previous studies showed that when polymorphonuclear neutrophils (PMNs) are depleted, burn injury-induced increase in microvascular permeability to albumin is markedly attenuated. Thus, we hypothesized that the combination of burn injury and polymicrobial infection exacerbates PMN activation, increases intestinal microvascular permeability to albumin, and alters hemodynamics and metabolism more than burn injury or infection alone. Sprague-Dawley rats (250-275 g) were divided into four groups. In the burn group, rats were subjected to a 30% TBSA burn injury. In the cecal-ligation puncture (CLP) group, CLP was performed using a 22-gauge needle with one puncture. In burn+CLP group, rats were subjected to CLP immediately after burn procedure. In sham group, rats were subjected to sham procedures. Transient polymicrobial bacteremia and persistent polymicrobial bacteremia were induced in the CLP group and burn+CLP group, respectively. Microvascular permeability, myeloperoxidase, and PMN production of elastase and reactive oxygen species increased in the burn group and CLP group and further increased in the burn+CLP group. Hemodunamic and metabolic alterations on day 1 and 3 after injury correlated with those alterations. Although there was only a low mortality in the burn group and CLP group, there was a high mortality in burn+CLP group (79%). The mechanism of MOF that leads to high mortality in burn injury complicated by infection may involve uncontrolled microvascular damage mediated by PMN activation.

Effects of Quorum Sensing Molecules of Pseudomonas aeruginosa on Organism Growth, Elastase B Production, and Primary Adhesion to Hydrogel Contact Lenses

Extracellular proteinase production and biofilm structure of Pseudomonas aeruginosa are affected by acylated homoserine lactones (AHLs) termed quorum sensing (QS) factors. C12- and C4-AHLs of P. aeruginosa and a synthetic furanone signaling antagonist were evaluated for effects on growth, primary adhesion to hydrogel contact lenses, and elastase B production of P. aeruginosa strains, including QS mutants, and isolates of Staphylococcus aureus and Staphylococcus epidermidis. Acylated homoserine lactones and furanone were added to cultures of bacteria at various growth stages. Primary adhesion of P. aeruginosa to lenses soaked in AHLs and furanone was examined by adenosine triphosphate analysis. Elastase B activity of cultures exposed to AHLs and furanone was determined by an elastin congo red assay. Acylated homoserine lactones had no significant effects on maximal cell densities or primary adhesion. Adhesion of a lasI-rhlI- QS mutant to lenses was significantly lower than its wild-type (WT) strain, regardless of added AHL or furanone. Exogenous AHLs had negligible effects on elastase production of WT P. aeruginosa but restored elastase production in QS-deficient mutants. The furanone was biocidal for staphylococci but enhanced growth of the lasI-rhlI- QS mutant. The furanone decreased elastase production of WT strains but increased QS mutant elastase production. Exogenous AHLs and the furanone were of minor importance in initial adhesion of P. aeruginosa to lenses. The furanone decreased staphylococci growth and elastase production of WT P. aeruginosa but increased growth and elastase production of QS mutants. The data further indicate strain diversity in P. aeruginosa and complexity of AHL systems.

Has the time come to prescribe azithromycin in cystic fibrosis patients?

Has the time come to prescribe azithromycin in cystic fibrosis patients?