Diffuse panbronchiolitis and cystic fibrosis: East meets West

The microenvironment in antibiotic susceptibility testing

Antibiotic susceptibility testing (AST) by agar diffusion has been repeatedly standardized and, in most cases, gives results which predict clinical success when antibiotic treatment is based on such results. The formation of the inhibition zone is due to a transition from planktonic to biofilm mode of growth. The kinetics of the interaction of antibiotics with bacteria is similar during AST by agar diffusion and during administration of antibiotics to the patients. However, the Mueller-Hinton agar (MHA) recommended for AST agar diffusion test is fundamentally different from the composition of the interstitial fluid in the human body where the infections take place and human cells do not thrive in MH media. Use of RPMI 1640 medium designed for growth of eucaryotic cells for AST of Pseudomonas aeruginosa against azithromycin results in lower minimal inhibitory concentration, compared to results obtained by MHA. The reason is that the RPMI 1640 medium increases uptake and reduces efflux of azithromycin compared to MHA. During treatment of cystic fibrosis patients with azithromycin, mutational resistance occur which is not detected by AST with MHA. Whether this is the case with other antibiotics and bacteria is not known but it is of clinical importance to be studied.

Characterization of Pseudomonas aeruginosa from subjects with diffuse panbronchiolitis

Diffuse panbronchiolitis (DPB) is a rare, idiopathic inflammatory disease primarily diagnosed in East Asian populations. DPB is characterized by diffuse pulmonary lesions, inflammation of the respiratory bronchioles, and bacterial infections of the airway. Historically, sputum cultures reveal Pseudomonas aeruginosa in 22% of DPB patients, increasing to 60% after 4 years from disease onset. Although DPB patients have a known susceptibility to respiratory P. aeruginosa infections, as is observed in other chronic lung diseases such as cystic fibrosis (CF), the characterization of DPB P. aeruginosa strains is limited. In this study, we characterized 24 strains obtained from a cohort of DPB patients for traits previously associated with virulence, including growth, motility, antibiotic susceptibility, lipopolysaccharide structure, and genomic diversity. Our cohort of DPB P. aeruginosa strains exhibits considerable genomic variability when compared with isolates from people with cystic fibrosis chronically colonized with P. aeruginosa and acute P. aeruginosa infection isolates. Similar to CF, DPB P. aeruginosa strains produce a diverse array of modified lipid A structures. Antibiotic susceptibility testing revealed increased resistance to erythromycin, a representative agent of the macrolide antibiotics used to manage DPB patients. Differences in the O-antigen type among P. aeruginosa strains collected from these different backgrounds were also observed. Ultimately, the characterization of DPB P. aeruginosa strains highlights several unique qualities of P. aeruginosa strains collected from chronically diseased airways, underscoring the challenges in treating DPB, CF, and other obstructive respiratory disease patients with P. aeruginosa infections.

IMPORTANCE

Diffuse panbronchiolitis (DPB), a chronic lung disease characterized by persistent P. aeruginosa infection, serves as an informative comparator to more common chronic lung diseases, such as cystic fibrosis (CF). This study aimed to better address the interplay between P. aeruginosa and chronically compromised airway environments through the examination of DPB P. aeruginosa strains, as existing literature regarding DPB is limited to case reports, case series, and clinical treatment guidelines. The evaluation of these features in the context of DPB, in tandem with prevailing knowledge of P. aeruginosa strains collected from more common chronic lung diseases (e.g., CF), can aid in the development of more effective strategies to combat respiratory P. aeruginosa infections in patients with chronic lung diseases.

Effects of quorum sensing-interfering agents, including macrolides and furanone C-30, and an efflux pump inhibitor on nitrosative stress sensitivity in Pseudomonas aeruginosa

Long-term administration of certain macrolides is efficacious in patients with persistent pulmonary Pseudomonas aeruginosa infection, despite how limited the clinically achievable concentrations are, being far below their MICs. An increase in the sub-MIC of macrolide exposure-dependent sensitivity to nitrosative stress is a typical characteristic of P. aeruginosa. However, a few P. aeruginosa clinical isolates do not respond to sub-MIC of macrolide treatment. Therefore, we examined the effects of sub-MIC of erythromycin (EM) on the sensitivity to nitrosative stress together with an efflux pump inhibitor (EPI) phenylalanine arginyl β-naphthylamide (PAβN). The sensitivity to nitrosative stress increased, suggesting that the efflux pump was involved in inhibiting the sub-MIC of macrolide effect. Analysis using efflux pump-mutant P. aeruginosa revealed that MexAB-OprM, MexXY-OprM, and MexCD-OprJ are factors in reducing the sub-MIC of macrolide effect. Since macrolides interfere with quorum sensing (QS), we demonstrated that the QS-interfering agent furanone C-30 (C-30) producing greater sensitivity to nitric oxide (NO) stress than EM. The effect of C-30 was decreased by overproduction of MexAB-OprM. To investigate whether the increase in the QS-interfering agent exposure-dependent sensitivity to nitrosative stress is characteristic of P. aeruginosa clinical isolates, we examined the viability of P. aeruginosa treated with NO. Although treatment with EM could reduce cell viability, a high variability in EM effects was observed. Conversely, C-30 was highly effective at reducing cell viability. Treatment with both C-30 and PAβN was sufficiently effective against the remaining isolates. Therefore, the combination of a QS-interfering agent and an EPI could be effective in treating P. aeruginosa infections.

Macrolide antibiotics (including azithromycin) for cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is a life-limiting genetic condition, affecting over 90,000 people worldwide. CF affects several organs in the body, but airway damage has the most profound impact on quality of life (QoL) and survival. Causes of lower airway infection in people with CF are, most notably, Staphylococcus aureus in the early course of the disease and Pseudomonas aeruginosa at a later stage. Macrolide antibiotics, e.g. azithromycin and clarithromycin, are usually taken orally, have a broad spectrum of action against gram-positive (e.g. S aureus) and some gram-negative bacteria (e.g. Haemophilus influenzae), and may have a modifying role in diseases involving airway infection and inflammation such as CF. They are well-tolerated and relatively inexpensive, but widespread use has resulted in the emergence of resistant bacteria. This is an updated review.

OBJECTIVES

To assess the potential effects of macrolide antibiotics on clinical status in terms of benefit and harm in people with CF. If benefit was demonstrated, we aimed to assess the optimal type, dose and duration of macrolide therapy.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals, and abstract books of conference proceedings. We last searched the Group's Cystic Fibrosis Trials Register on 2 November 2022. We last searched the trial registries WHO ICTRP and clinicaltrials.gov on 9 November 2022. We contacted investigators known to work in the field, previous authors and pharmaceutical companies manufacturing macrolide antibiotics for unpublished or follow-up data, where possible.

SELECTION CRITERIA

We included randomised controlled trials of macrolide antibiotics in adults and children with CF. We compared them to: placebo; another class of antibiotic; another macrolide antibiotic; or the same macrolide antibiotic at a different dose or type of administration.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed risk of bias. We assessed the certainty of evidence using GRADE.

MAIN RESULTS

We included 14 studies (1467 participants) lasting 28 days to 36 months. All the studies assessed azithromycin: 11 compared oral azithromycin to placebo (1167 participants); one compared a high dose to a low dose (47 participants); one compared nebulised to oral azithromycin (45 participants); and one looked at weekly versus daily dose (208 participants). Oral azithromycin versus placebo There is a slight improvement in forced expiratory volume (FEV1 % predicted) in one second in the azithromycin group at up to six months compared to placebo (mean difference (MD) 3.97, 95% confidence interval (CI) 1.74 to 6.19; high-certainty evidence), although there is probably no difference at three months, (MD 2.70%, 95% CI -0.12 to 5.52), or 12 months (MD -0.13, 95% CI -4.96 to 4.70). Participants in the azithromycin group are probably at a decreased risk of pulmonary exacerbation with a longer time to exacerbation (hazard ratio (HR) 0.61, 95% CI 0.50 to 0.75; moderate-certainty evidence). Mild side effects were common, but there was no difference between groups (moderate-certainty evidence). There is no difference in hospital admissions at six months (odds ratio (OR) 0.61, 95% CI 0.36 to 1.04; high-certainty evidence), or in new acquisition of P aeruginosa at 12 months (HR 1.00, 95% CI 0.64 to 1.55; moderate-certainty evidence). High-dose versus low-dose azithromycin We are uncertain whether there is any difference in FEV1 % predicted at six months between the two groups (no data available) or in the rate of exacerbations per child per month (MD -0.05 (95% CI -0.20 to 0.10)); very low-certainty evidence for both outcomes. Only children were included in the study and the study did not report on any of our other clinically important outcomes. Nebulised azithromycin versus oral azithromycin We were unable to include any of the data into our analyses and have reported findings directly from the paper; we graded all evidence as being of very low certainty. The authors reported that there was a greater mean change in FEV1 % predicted at one month in the nebulised azithromycin group (P < 0.001). We are uncertain whether there was a change in P aeruginosa count. Weekly azithromycin versus daily azithromycin There is probably a lower mean change in FEV1 % predicted at six months in the weekly group compared to the daily group (MD -0.70, 95% CI -0.95 to -0.45) and probably also a longer period of time until first exacerbation in the weekly group (MD 17.30 days, 95% CI 4.32 days to 30.28 days). Gastrointestinal side effects are probably more common in the weekly group and there is likely no difference in admissions to hospital or QoL. We graded all evidence as moderate certainty.

AUTHORS' CONCLUSIONS

Azithromycin therapy is associated with a small but consistent improvement in respiratory function, a decreased risk of exacerbation and longer time to exacerbation at six months; but evidence for treatment efficacy beyond six months remains limited. Azithromycin appears to have a good safety profile (although a weekly dose was associated with more gastrointestinal side effects, which makes it less acceptable for long-term therapy), with a relatively minimal treatment burden for people with CF, and it is inexpensive. A wider concern may be the emergence of macrolide resistance reported in the most recent study which, combined with the lack of long-term data, means we do not feel that the current evidence is strong enough to support azithromycin therapy for all people with CF. Future research should report over longer time frames using validated tools and consistent reporting, to allow for easier synthesis of data. In particular, future trials should report important adverse events such as hearing impairment or liver disease. More data on the effects of azithromycin given in different ways and reporting on our primary outcomes would benefit decision-making on whether and how to give macrolide antibiotics. Finally, it is important to assess azithromycin therapy for people with CF who are established on the relatively new cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapies which correct the underlying molecular defect associated with CF (none of the trials included in the review are relevant to this population).

Macrolide therapy in Pseudomonas aeruginosa infections causes uL4 ribosomal protein mutations leading to high-level resistance

OBJECTIVES

Pseudomonas aeruginosa colonizes the cystic fibrosis (CF) airways causing chronic bacterial lung infections. CF patients are routinely treated with macrolides, however, P. aeruginosa is considered insusceptible as consequence of inadequate susceptibility testing leaving resistance mechanism completely overlooked. Here, we investigated a new mechanism of macrolide resistance caused by ribosomal protein mutations.

METHODS

Investigating a longitudinal collection of 529 isolates from CF patients and analysing 5758 protein sequences from different sources, mutations in P. aeruginosa's ribosomal proteins connected to macrolide resistance were identified. Using a modified susceptibility testing protocol, isolates harbouring a mutated uL4 ribosomal protein were tested for resistance against macrolide antibiotics and macrolide-induced quorum sensing modulation. Proteome and ribosome profiling were applied to assess the impact of the mutations on the bacterial physiology.

RESULTS

Five uL4 mutations were identified in isolates from different CF patients. Most mapped to the conserved loop region of uL4 and resulted in increased macrolide tolerance (>10-fold relative to wt strains). Greater concentrations (>10-fold) of macrolide antibiotic were needed to inhibit the growth, reduce swimming motility, and induce redox sensitivity of the uL4 mutants. 16 proteins involved in ribosome adaptation displayed altered expression possibly to compensate for the uL4 mutations, which changed the ribosome stoichiometry without negatively affecting bacterial physiology.

CONCLUSIONS

Macrolide antibiotics should, therefore, be considered as active antimicrobial agents against P. aeruginosa and resistance development should be contemplated when patients are treated with prolonged courses of macrolides. Importantly, improved macrolide susceptibility testing is necessary for the detection of resistant bacteria.

Treatment of Pulmonary Disease of Cystic Fibrosis: A Comprehensive Review

Cystic fibrosis (CF) is a genetic disease that causes absence or dysfunction of a protein named transmembrane conductance regulatory protein (CFTR) that works as an anion channel. As a result, the secretions of the organs where CFTR is expressed are very viscous, so their functionality is altered. The main cause of morbidity is due to the involvement of the respiratory system as a result of recurrent respiratory infections by different pathogens. In recent decades, survival has been increasing, rising by around age 50. This is due to the monitoring of patients in multidisciplinary units, early diagnosis with neonatal screening, and advances in treatments. In this chapter, we will approach the different therapies used in CF for the treatment of symptoms, obstruction, inflammation, and infection. Moreover, we will discuss specific and personalized treatments to correct the defective gene and repair the altered protein CFTR. The obstacle for personalized CF treatment is to predict the drug response of patients due to genetic complexity and heterogeneity of uncommon mutations.

Effect of Sub-MICs of Macrolides on the Sensitivity of Pseudomonas aeruginosa to Nitrosative Stress: Effectiveness against P. aeruginosa with and without Multidrug Resistance

Sub-MICs of the 14-membered macrolides erythromycin (EM) and clarithromycin (CAM) decreased the growth of Pseudomonas aeruginosa PAO1 and increased its sensitivity to endogenous and exogenous nitrosative stress. However, a 16-membered macrolide, josamycin (JM), was not or less effective. In 9 of 13 non-multidrug-resistant P. aeruginosa (non-MDRP) and 9 of 27 MDRP ST235 strains, the sub-MIC of EM induced significant reductions in bacterial numbers following treatment with a nitric oxide donor.

Two novel synthetic peptides inhibit quorum sensing-dependent biofilm formation and some virulence factors in Pseudomonas aeruginosa PAO1

Quorum sensing (QS) regulates virulence factor expression in Pseudomonas aeruginosa. Inhibiting the QS-controlled virulence factors without inhibiting the growth of P. aeruginosa is a promising approach for overcoming the widespread resistance of P. aeruginosa. This study was proposed to investigate the effects of two novel synthetic peptides on the biofilm development and virulence factor production of P. aeruginosa. The tested strain was P. aeruginosa PAO1. The results indicated that both of the synthetic peptides (LIVRHK and LIVRRK) inhibited (P < 0.05) the formation of biofilms and the production of virulence factors, including pyocyanin, protease, and rhamnolipids, without inhibiting the growth of PAO1. Additionally, we detected transcriptional changes related to QS and found a significant reduction in the levels of gene expression of lasI, lasR, rhlI, and rhlR. This study demonstrates that LIVRRK and LIVRHK are novel synthetic peptides that can act as potent inhibitors of QS-regulated virulence factors in P. aeruginosa. Moreover, these synthetic peptides have potential applications in the treatment of biofilmrelated diseases. Both peptides may be able to control chronic infections and biofilm-associated problems of P. aeruginosa.

Immune and xenobiotic response crosstalk to chemical exposure by PA01 infection in the nematode Caenorhabditis elegans

Most organisms simultaneously face various chemical and biological stresses in the environment. Herein, we investigated how pathogen infection modifies an organism's response to chemical exposure. To explore this phenomenon, we conducted a toxicity study combined with pathogen infection by using the nematode Caenorhabditis elegans, the pathogen Pseudomonas aeruginosa, and various environmental chemicals. C. elegans preinfected with PA01, when subsequently exposed to chemicals, became sensitized to the toxicity of nonylphenol (NP) and cadmium (Cd), whereas they became tolerant to the toxicity of silver nanoparticles (AgNPs); this led us to conduct a mechanistic study focusing on AgNP exposure. A gene expression profiling study revealed that most of the immune response genes activated by PA01 infection remained activated after subsequent exposure to AgNPs, thereby suggesting that the acquired tolerance of C. elegans to AgNP exposure may be due to boosted immunity resulting from PA01 preinfection. Further, a functional genetic analysis revealed that the immune response pathway (i.e., PMK-1/p38 MAPK) was involved in defense against AgNP exposure in PA01-preinfected C. elegans, thus suggesting immune and stress response crosstalk to xenobiotic exposure. This study will aid in the elucidation of how pathogen infection impacts the way the defense system responds to subsequent xenobiotic exposure.

Expression of extracellular polysaccharides and proteins by clinical isolates of Pseudomonas aeruginosa in response to environmental conditions

The opportunistic pathogen Pseudomonas aeruginosa causes chronic respiratory infections in patients with cystic fibrosis (CF). Persistence of this bacterium is attributed to its ability to form biofilms which rely on an extracellular polymeric substance matrix. Extracellular polysaccharides (EPS) and secreted proteins are key matrix components of P. aeruginosa biofilms. Recently, nebulized magnesium sulfate has been reported as a significant bronchodilator for asthmatic patients including CF. However, the impact of magnesium sulfate on the virulence effect of P. aeruginosa is lacking. In this report, we investigated the influence of magnesium sulfate and other environmental factors on the synthesis of alginate and secretion of proteins by a mucoid and a non-mucoid strain of P. aeruginosa, respectively. By applying the Plackett-Burman and Box-Behnken experimental designs, we found that phosphates (6.0 g/l), ammonium sulfate (4.0 g/l), and trace elements (0.6 mg/l) markedly supported alginate production by the mucoid strain. However, ferrous sulfate (0.3 mg/l), magnesium sulfate (0.02 g/l), and phosphates (6.0 g/l) reinforced the secretion of proteins by the non-mucoid strain.

Autoinflammatory disease in the lung

Ascertaining the dominant cell type driving an immunological disease is essential to understanding the causal pathology and, therefore, selecting or developing an effective treatment. Classifying immunological diseases in this way has led to successful treatment regimens for many monogenic diseases; however, when the dominant cell type is unclear and there is no obvious causal genetic mutation, then identifying the correct disease classification and appropriate therapy can be challenging. In this review we focus on pulmonary immunological diseases where an innate immune signature has been identified as a predominant aspect of the immunopathology. We describe the molecular pathology of 'autoinflammatory diseases of the lung' and propose that small molecule and biological therapies, including recombinant interleukin-1 receptor antagonist, that target key innate immune pathways, are likely be beneficial in the control of pulmonary and systemic inflammation in these conditions. In addition, the successful use of macrolide antibiotics to treat lung infections in these conditions further confirms that the innate immune system is the key conductor of inflammation in these pulmonary diseases, as there is a strong body of evidence that macrolides are able to modulate the NLRP3 inflammasome and interleukin-1β and interleukin-18 secretion, both of which are central players in the innate immune response. Throughout this review we highlight the published evidence of autoinflammatory disease in chronic obstructive pulmonary disease, bronchiectasis, cystic fibrosis and rheumatoid lung disease and suggest that the fundamental pathology of these diseases places them towards the autoinflammatory pole of the immunological disease continuum.

Azithromycin Attenuates Pseudomonas-Induced Lung Inflammation by Targeting Bacterial Proteins Secreted in the Cultured Medium

Background

Pseudomonas aeruginosa airway infections are a major cause of morbidity and mortality in patients with cystic fibrosis (CF). Azithromycin improves the related clinical outcomes, but its mechanisms of action remain poorly understood. We tested the hypothesis that azithromycin downregulates P. aeruginosa-induced pro-inflammatory responses by modifying release of bacterial proteins.

Methods

We monitored inflammatory markers in lungs of CF mutant mice and their littermate controls in response to conditioned media (CM) collected from the reference P. aeruginosa PAO1 strain cultured in the presence or in the absence of azithromycin. A mass spectrometry-based proteomic approach was applied to examine whether the macrolide elicits a differential release of bacterial proteins.

Results

CM collected from azithromycin-untreated PAO1 cultures induced powerful pro-inflammatory neutrophil-dominated responses. Azithromycin attenuated the responses, mainly of macrophage chemoattractant protein-1, tumor necrosis factor-α, and interferon-γ, in CF but not in wild-type mice. Proteomic analysis showed that azithromycin upregulated an array of bacterial proteins including those associated with regulation of immune functions and with repair and resolution of inflammatory responses like the chaperone DnaK and the S-adenosylmethionine synthase, while it downregulated the extracellular heme acquisition protein HasA and the catalytic enzyme lysylendopeptidase.

Conclusion

Supernatants collected from cultures of the bacterial strain PAO1 represent a novel experimental model to trigger in vivo lung inflammatory responses that should be closer to those obtained with live bacteria, but without bacterial infection. Combined with a bactericidal effect, complex regulation of bacterial innate immune and metabolic factors released in the cultured medium by the action of the macrolide can contribute to its anti-inflammatory effects.

Management of Pulmonary Disease in Patients with Cystic Fibrosis

Cystic fibrosis is the most common, life-shortening autosomal recessive disease, affecting approximately 1 in 3400 live births in the United States. Gastrointestinal and pulmonary manifestations are most common. With the introduction of pancreatic enzyme and vitamin supplementation, lung disease accounts for the vast majority of morbidity and mortality in patients with cystic fibrosis. The lungs of cystic fibrosis patients are essentially normal at birth but demonstrate evidence of airway inflammation and infection in early infancy. A vicious cycle of inflammation, infection and obstruction ultimately leads to destruction of airways, impairment of gas exchange and death.

Current pharmacological management of pulmonary disease targets reducing airway obstruction, controlling infection and more recently, controlling inflammation. An increased recovery of unusual and highly resistant bacteria from patients with more advanced disease has been observed. Aggressive treatment of acute pulmonary exacerbations with combination antibiotic therapy for two to three weeks has shown pronounced beneficial effects. The routine use of prophylactic antistaphylococcal antibiotics is still controversial.

Although current pharmacologic treatment is symptomatic, new agents are being developed and studied that target the underlying defect in the CFTR protein. This review focuses on current pharmacologic management of pulmonary disease in patients with cystic fibrosis and the role of new agents emerging for the treatment of this disease.

Mechanism of azithromycin inhibition of HSL synthesis in Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen and a leading cause of nosocomial infections. Unfortunately, P. aeruginosa has low antibiotic susceptibility due to several chromosomally encoded antibiotic resistance genes. Hence, we carried out mechanistic studies to determine how azithromycin affects quorum sensing and virulence in P. aeruginosa. lasI and rhlI single and double mutants were constructed. We then undertook a quantitative approach to determine the optimal concentration of azithromycin and culture time that can affect the expression of HSLs. Furthermore, based on the above results, the effect on quorum sensing was analyzed at a transcriptional level. It was found that 2 μg/mL azithromycin caused a 79% decrease in 3-oxo-C12-HSL secretion during cultivation, while C4-HSL secretion was strongly repressed in the early stages. Azithromycin acts on ribosomes; to determine whether this can elicit alternative modes of gene expression, transcriptional regulation of representative virulence genes was analyzed. We propose a new relationship for lasI and rhlI: lasI acts as a cell density sensor, and rhlI functions as a fine-tuning mechanism for coordination between different quorum sensing systems.

Mycofabricated biosilver nanoparticles interrupt Pseudomonas aeruginosa quorum sensing systems

Quorum sensing (QS) is a chemical communication process that Pseudomonas aeruginosa uses to regulate virulence and biofilm formation. Disabling of QS is an emerging approach for combating its pathogenicity. Silver nanoparticles (AgNPs) have been widely applied as antimicrobial agents against human pathogenic bacteria and fungi, but not for the attenuation of bacterial QS. Here we mycofabricated AgNPs (mfAgNPs) using metabolites of soil fungus Rhizopus arrhizus BRS-07 and tested their effect on QS-regulated virulence and biofilm formation of P. aeruginosa. Transcriptional studies demonstrated that mfAgNPs reduced the levels of LasIR-RhlIR. Treatment of mfAgNPs inhibited biofilm formation, production of several virulence factors (e.g. LasA protease, LasB elastrase, pyocyanin, pyoverdin, pyochelin, rhamnolipid, and alginate) and reduced AHLs production. Further genes quantification analyses revealed that mfAgNPs significantly down-regulated QS-regulated genes, specifically those encoded to the secretion of virulence factors. The results clearly indicated the anti-virulence property of mfAgNPs by inhibiting P. aeruginosa QS signaling.

Pseudomonas aeruginosa disrupts Caenorhabditis elegans iron homeostasis, causing a hypoxic response and death

The opportunistic pathogen Pseudomonas aeruginosa causes serious human infections, but effective treatments and the mechanisms mediating pathogenesis remain elusive. Caenorhabditis elegans shares innate immune pathways with humans, making it invaluable to investigate infection. To determine how P. aeruginosa disrupts host biology, we studied how P. aeruginosa kills C. elegans in a liquid-based pathogenesis model. We found that P. aeruginosa-mediated killing does not require quorum-sensing pathways or host colonization. A chemical genetic screen revealed that iron chelators alleviate P. aeruginosa-mediated killing. Consistent with a role for iron in P. aeruginosa pathogenesis, the bacterial siderophore pyoverdin was required for virulence and was sufficient to induce a hypoxic response and death in the absence of bacteria. Loss of the C. elegans hypoxia-inducing factor HIF-1, which regulates iron homeostasis, exacerbated P. aeruginosa pathogenesis, further linking hypoxia and killing. As pyoverdin is indispensable for virulence in mice, pyoverdin-mediated hypoxia is likely to be relevant in human pathogenesis.

Clinical efficacy of roxithromycin in men with chronic prostatitis/chronic pelvic pain syndrome in comparison with ciprofloxacin and aceclofenac: a prospective, randomized, multicenter pilot trial

Roxithromycin is effective in the treatment of intracellular organisms, including chlamydia and mycoplasma, and exhibits anti-inflammatory and immunomodulatory effects on respiratory diseases. To explore the potential therapeutic benefit of roxithromycin in chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), this study compared the effect of roxithromycin with ciprofloxacin and aceclofenac. A total of 75 patients with CP/CPPS were randomized to three groups in open-label: group 1, ciprofloxacin; group 2, aceclofenac; and group 3, roxithromycin. The patients were treated for 4 weeks and were subsequently followed for 12 weeks. Changes from baseline in the total and domain scores of the NIH Chronic Prostatitis Symptom Index (NIH-CPSI) were evaluated. The NIH-CPSI score decreased in the roxithromycin, ciprofloxacin, and aceclofenac groups to a similar degree. The NIH-CPSI initial and 12-week total scores were 20.3 and 10.0, respectively, in group 1; 23.6 and 14.3, respectively, in group 2; and 21.1 and 9.8, respectively, in group 3. The three treatment arms did not differ significantly with respect to the efficiency of treatment (p > 0.05). Compared to patients in groups 1 and 2, group 3 patients with Category IIIb disease exhibited favorable results upon follow-up 12 weeks after treatment. The International Prostate Symptom Score (IPSS), uroflowmetry, and post-void residual volume were equivalent between the groups. Roxithromycin exhibits similar or favorable effects on the improvement of CP/CPPS compared to ciprofloxacin and aceclofenac. Roxithromycin could be used as a new therapeutic agent for CP/CPPS. Further study of the immunomodulatory action of roxithromycin in CP/CPPS is required.

Exploiting quorum sensing to confuse bacterial pathogens

Cell-cell communication, or quorum sensing, is a widespread phenomenon in bacteria that is used to coordinate gene expression among local populations. Its use by bacterial pathogens to regulate genes that promote invasion, defense, and spread has been particularly well documented. With the ongoing emergence of antibiotic-resistant pathogens, there is a current need for development of alternative therapeutic strategies. An antivirulence approach by which quorum sensing is impeded has caught on as a viable means to manipulate bacterial processes, especially pathogenic traits that are harmful to human and animal health and agricultural productivity. The identification and development of chemical compounds and enzymes that facilitate quorum-sensing inhibition (QSI) by targeting signaling molecules, signal biogenesis, or signal detection are reviewed here. Overall, the evidence suggests that QSI therapy may be efficacious against some, but not necessarily all, bacterial pathogens, and several failures and ongoing concerns that may steer future studies in productive directions are discussed. Nevertheless, various QSI successes have rightfully perpetuated excitement surrounding new potential therapies, and this review highlights promising QSI leads in disrupting pathogenesis in both plants and animals.

Macrolide antibiotics for cystic fibrosis

BACKGROUND

Macrolide antibiotics may have a modifying role in diseases which involve airway infection and inflammation, like cystic fibrosis.

OBJECTIVES

To test the hypotheses that, in people with cystic fibrosis, macrolide antibiotics: 1. improve clinical status compared to placebo or another antibiotic; 2. do not have unacceptable adverse effects. If benefit was demonstrated, we aimed to assess the optimal type, dose and duration of macrolide therapy.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings.We contacted investigators known to work in the field, previous authors and pharmaceutical companies manufacturing macrolide antibiotics for unpublished or follow-up data (May 2010).Latest search of the Group's Cystic Fibrosis Trials Register: 29 February 2012.

SELECTION CRITERIA

Randomised controlled trials of macrolide antibiotics compared to: placebo; another class of antibiotic; another macrolide antibiotic; or the same macrolide antibiotic at a different dose.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed risk of bias. Seven groups were contacted and provided additional data which were incorporated into the review.

MAIN RESULTS

Ten of 31 studies identified were included (959 patients). Five studies with a low risk of bias examined azithromycin versus placebo and demonstrated consistent improvement in forced expiratory volume in one second over six months (mean difference at six months 3.97% (95% confidence interval 1.74% to 6.19%; n = 549, from four studies)). Patients treated with azithromycin were approximately twice as likely to be free of pulmonary exacerbation at six months, odds ratio 1.96 (95% confidence interval 1.15 to 3.33). With respect to secondary outcomes, there was a significant reduction in need for oral antibiotics and greater weight gain in those taking azithromycin. Adverse events were uncommon and not obviously associated with azithromycin, although a once-weekly high dose regimen was associated with more frequent gastrointestinal adverse events. Treatment with azithromycin was associated with reduced identification of Staphylococcus aureus on respiratory culture, but also a significant increase in macrolide resistance.

AUTHORS' CONCLUSIONS

This review provides evidence of improved respiratory function after six months of azithromycin. Data beyond six months were less clear, although reduction in pulmonary exacerbation was sustained. Treatment appeared safe over a six-month period; however, emergence of macrolide resistance was a concern. A multi-centre trial examining long-term effects of this antibiotic treatment is needed, especially for infants recognised through newborn screening.

Diffuse Panbronchiolitis

Diffuse panbronchiolitis (DPB) is characterized by chronic sinobronchial infection and diffuse bilateral micronodular pulmonary lesions consisting of inflammatory cells. Studies on disease etiology point to a genetic predisposition unique to Asians. Early therapy for DPB was largely symptomatic. The advent of macrolide antibiotics, including erythromycin, roxithromycin and clarithromycin, has strikingly changed disease prognosis. Low-dose, long-term macrolide therapy for DPB originated from detailed observations of response to therapy in a single patient. The bactericidal activity of macrolides, particularly erythromycin, is not a significant factor for their clinical efficacy in DPB. Firstly, irrespective of bacterial clearance, clinical improvement is observed in patients treated with erythromycin. Secondly, even in cases with bacterial superinfection with Pseudomonas aeruginosa resistant to macrolides, treatment has proved effective. Thirdly, the recommended dosage of macrolides produces peak levels in tissue that are below the minimum inhibitory concentrations for major pathogenic bacteria that colonize the airway. In the last two decades, the possible mechanism underlying the effectiveness of macrolide therapy has been extensively studied. The proposed mechanism of action includes inhibition of excessive mucus and water secretion from the airway epithelium, inhibition of neutrophil accumulation in the large airway, inhibition of lymphocyte and macrophage accumulation around the small airway, and modulation of bacterial virulence. The great success of macrolide therapy in diffuse panbronchiolitis may extend its application to the treatment of other chronic inflammatory disorders. If the anti-inflammatory activity of macrolides is independent of their bactericidal effect, new anti-inflammatory macrolides without antimicrobial activity should be developed to minimize emergence of macrolide-resistant micro-organisms.

The role of macrolides in childhood non-cystic fibrosis-related bronchiectasis

Non-cystic fibrosis-related bronchiectasis is a chronic inflammatory lung disease, which is regarded as an “orphan” lung disease, with little research devoted to the study of this condition. Bronchiectasis results in impaired quality of life and mortality if left untreated. The tools available in the armamentarium for the management of bronchiectasis entail antibiotic therapy traditionally used to treat exacerbations, stratagems to improve mucociliary clearance, and avoidance of toxins. Macrolides have been known for the last two decades to have not only anti-bacterial effects but immunomodulatory properties as well. In cystic fibrosis, the use of macrolides is well documented in subjects colonized with Pseudomonas aeruginosa, to improve quality of life and lung function. There is currently emerging evidence to suggest the benefit of macrolides in subjects not colonized with Pseudomonas aeruginosa. This beneficial effect has been less explored in the context of bronchiectasis from other causes. The purpose of this paper is to review the current literature on the use of macrolides in non-cystic fibrosis related bronchiectasis in paediatrics.

Macrolide antibiotics for cystic fibrosis

BACKGROUND

Macrolide antibiotics may have a modifying role in diseases which involve airway infection and inflammation, like cystic fibrosis.

OBJECTIVES

To test the hypotheses that, in people with cystic fibrosis, macrolide antibiotics: 1. improve clinical status compared to placebo or another antibiotic; 2. do not have unacceptable adverse effects. If benefit was demonstrated, we aimed to assess the optimal type, dose and duration of macrolide therapy.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings.We contacted investigators known to work in the field, previous authors and pharmaceutical companies manufacturing macrolide antibiotics for unpublished or follow-up data (May 2010).Latest search of the Group's Cystic Fibrosis Trials Register: 09 February 2011.

SELECTION CRITERIA

Randomised controlled trials of macrolide antibiotics compared to: placebo; another class of antibiotic; another macrolide antibiotic; or the same macrolide antibiotic at a different dose.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed risk of bias. Seven groups were contacted and provided additional data which were incorporated into the review.

MAIN RESULTS

Ten of 31 studies identified were included (959 patients). Five studies with a low risk of bias examined azithromycin versus placebo and demonstrated consistent improvement in forced expiratory volume in one second over six months (mean difference at six months 3.97% (95% confidence interval 1.74% to 6.19%; n = 549, from four studies)). Patients treated with azithromycin were approximately twice as likely to be free of pulmonary exacerbation at six months, odds ratio 1.96 (95% confidence interval 1.15 to 3.33). With respect to secondary outcomes, there was a significant reduction in need for oral antibiotics and greater weight gain in those taking azithromycin. Adverse events were uncommon and not obviously associated with azithromycin, although a once-weekly high dose regimen was associated with more frequent gastrointestinal adverse events. Treatment with azithromycin was associated with reduced identification of Staphylococcus aureus on respiratory culture, but also a significant increase in macrolide resistance.

AUTHORS' CONCLUSIONS

This review provides evidence of improved respiratory function after six months of azithromycin. Data beyond six months were less clear, although reduction in pulmonary exacerbation was sustained. Treatment appeared safe over a six-month period; however, emergence of macrolide resistance was a concern. A multi-centre trial examining long-term effects of this antibiotic treatment is needed, especially for infants recognised through newborn screening.

Guideline on the design and conduct of cystic fibrosis clinical trials: the European Cystic Fibrosis Society-Clinical Trials Network (ECFS-CTN)

We describe the rationale for disease specific research networks in general as well as the aims and function of the European Cystic Fibrosis Society-Clinical Trials Network (ECFS-CTN) specifically. The ECFS-CTN was founded in 2009 with the aim of improving the quality and quantity of clinical research in the area of cystic fibrosis (CF) in Europe. A network of 18 clinical trial sites in 8 European countries was established according to uniform state-of-the-art quality criteria. To support the ECFS-CTN in the acquisition, planning and conduct of clinical trials, the network is equipped with a coordinating centre, steering and executive committees, and committees for protocol review, standardization, training and networking as well as a data safety monitoring board. A strong partnership with European CF patient parent organizations aims to increase awareness of the need for efficient clinical research and the participation of patients in clinical trials.

Genetic predisposition to diffuse panbronchiolitis

Diffuse panbronchiolitis is characterized by chronic inflammation in respiratory bronchioles and sinobronchial infection. The pathophysiology accompanying the persistent bacterial infection is noteworthy for the accumulation of lymphocytes and foamy macrophages around the small airways, for mucus hypersecretion, and for the number of neutrophils in the large airways. Until the establishment of long-term macrolide therapy, the prognosis was generally poor. Case studies of diffuse panbronchiolitis in East Asians, including Japanese, Koreans and Chinese, have frequently been reported, and genetic predisposition to the disease has been assumed in Asians. Immunogenetic studies revealed a strong association with human leukocyte antigen (HLA)-B54 in Japanese, whereas an association with HLA-A11 was reported in Koreans. These findings imply that a major susceptibility gene may be located between the HLA-A and HLA-B loci on the short arm of human chromosome 6. We have recently cloned novel mucin-like genes in this candidate region. In addition to accumulated knowledge of classical HLA genes and mucin genes, further analysis of newly identified genes may provide insights into the pathogenesis of the disease.

The role of azithromycin in patients with cystic fibrosis

Interest in azithromycin in the management of patients with cystic fibrosis has grown over the last decade. Uniquely this drug has both antibacterial and immune modulating effects which appear to be the reason for its clinical benefit as proven in several well designed clinical studies. In this review we discuss the proposed mechanisms of action of azithromycin and review the evidence for its clinical effectiveness and safety in cystic fibrosis.

Macrolide antibiotics and the airway: antibiotic or non-antibiotic effects?

IMPORTANCE OF THE FIELD

The macrolides are a class of antibiotics widely prescribed in infectious disease. More recently, there has been considerable interest in potential indications for these agents, in addition to their simple antibacterial indications, in a number of lung pathophysiologies.

AREAS COVERED IN THIS REVIEW

Demonstrated clinical efficacy of macrolides in diseases such as diffuse panbronchiolitis was difficult to ascribe to a direct antimicrobial action. More recently, positive experiences in dealing with post-transplant bronchiolitis obliterans syndrome suggests that other chronic lung diseases may benefit from macrolide therapy. This is important, as the treatment options for such diseases are often very limited. In this review, potential antibiotic and non-antibiotic beneficial actions of macrolide therapy are discussed and conclusions drawn from a limited but growing literature.

WHAT THE READER WILL GAIN

The reader will gain an overview of lung diseases that may benefit from macrolides, and a consideration of the possible mechanisms underlying such benefit.

TAKE HOME MESSAGE

The key message from our review is that this class of agents may prove to be a useful therapeutic option for a range of respiratory diseases, but that further trials and mechanistic studies are required to clarify their role.

[Usefulness of macrolides as anti-inflammatories in respiratory diseases]

The macrolides are antibiotics that, besides their anti-bacterial action, have an anti-inflammatory effect, by decreasing the activity of the immune cells and bacteria cell changes. An increase the survival of patients suffering from diffuse panbronchiolitis was already seen in the 1980s, after being treated with erythromycin. Currently, the use of macrolides in various chronic inflammatory diseases has increased significantly. Clinical improvements associated to the administration of macrolides have been observed in diseases such as, cystic fibrosis, asthma, and bronchiectasis. However, despite the apparent clinical benefit they seem to provide, the published results up until now are controversial and conclusive results are unable to be obtained. This means that further clinical trials are necessary to confirm or refute the long-term use of these drugs, which are not free of adverse effects, mainly the appearance of resistant bacteria.

A low concentration of azithromycin inhibits the mRNA expression of N-acyl homoserine lactone synthesis enzymes, upstream of lasI or rhlI, in Pseudomonas aeruginosa

Low-dose macrolides are effective therapy in patients with chronic lung infections, but the mechanisms of action are unclear. In this study, we performed DNA microarray analysis of Pseudomonas aeruginosa after treatment with a low concentration of azithromycin. We found that a sub-MIC of azithromycin didn't change mRNA expression of quorum-sensing related genes (lasI, lasR, rhlI, rhlR, vft, rsaL), but lowered expression of most N-acyl homoserine lactone (AHL) synthesis enzymes upstream of lasI and rhlI. We propose that small down regulation of these enzymes cumulatively resulted in a larger decrease of AHL production and inhibition of quorum-sensing in P. aeruginosa.

Long-term, low-dose azithromycin treatment reduces the incidence but increases macrolide resistance in Staphylococcus aureus in Danish CF patients

BACKGROUND

Since 2001, long-term, low-dose azithromycin treatment has been used for CF patients chronically infected with Pseudomonas aeruginosa in the Copenhagen CF centre. Our study investigates changes in incidence of colonization with Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis and changes in macrolide sensitivity in these microorganisms during azithromycin treatment.

METHODS

CF patients treated continuously with azithromycin for at least 3 months were included. Results of microbiological examination, including phage typing results of S. aureus, obtained during treatment were compared to results obtained 2 years before treatment.

RESULTS

70 patients (median age 29.1 years) treated for a median of 4 years (range 0.7-5.1) were included. Before treatment, 44 patients had at least one culture positive for S. aureus compared to 25 patients during treatment (p<0.01). Mean percentage of sputum samples with growth of S. aureus decreased from 12.1% (range 0-82.6%) before treatment to 6.1% (range 0-93.2) during treatment (p<0.0006). Prevalence's of H. influenzae and S. pneumoniae also decreased significantly. Fifteen of 214 isolates (7%) of S. aureus were macrolide resistant before treatment, increasing to 95 of 181 isolates (52.5%) during treatment (p<0.001). Macrolide resistant strains were found in 3 of 44 S. aureus colonized patients before treatment and in 11 of 25 patients at some time during treatment (p<0.03), all belonging to different phage types. First resistant S. aureus isolate was isolated after a median treatment duration of 1.5 years (range 0.3-2.9). No MRSA were isolated. Only 1 macrolide resistant isolate of M. catarrhalis was found during treatment. No macrolide resistance was found in H. influenzae or S. pneumoniae.

CONCLUSION

Long-term, low-dose treatment with azithromycin in CF patients leads to reduced prevalence of S. aureus, S. pneumoniae, and H. influenzae, but increased macrolide resistance in S. aureus. Reduction in the prevalence of S. aureus will make increasing macrolide resistance clinically insignificant in these patients.

Long-term erythromycin therapy is associated with decreased chronic obstructive pulmonary disease exacerbations

RATIONALE

Frequent chronic obstructive pulmonary disease (COPD) exacerbations are a major cause of hospital admission and mortality and are associated with increased airway inflammation. Macrolides have airway antiinflammatory actions and may reduce the incidence of COPD exacerbations.

OBJECTIVES

To determine whether regular therapy with macrolides reduces exacerbation frequency.

METHODS

We performed a randomized, double-blind, placebo-controlled study of erythromycin administered at 250 mg twice daily to patients with COPD over 12 months, with primary outcome variable being the number of moderate and/or severe exacerbations (treated with systemic steroids, treated with antibiotics, or hospitalized).

MEASUREMENTS AND MAIN RESULTS

We randomized 109 outpatients: 69 (63%) males, 52 (48%) current smokers, mean (SD) age 67.2 (8.6) years, FEV1 1.32 (0.53) L, FEV1% predicted 50 (18)%. Thirty-eight (35%) of the patients had three or more exacerbations in the year before recruitment, with no differences between treatment groups. There were a total of 206 moderate to severe exacerbations: 125 occurred in the placebo arm. Ten in the placebo group and nine in the macrolide group withdrew. Generalized linear modeling showed that the rate ratio for exacerbations for the macrolide-treated patients compared with placebo-treated patients was 0.648 (95% confidence interval: 0.489, 0.859; P = 0.003) and that these patients had shorter duration exacerbations compared with placebo. There were no differences between the macrolide and placebo arms in terms of stable FEV1, sputum IL-6, IL-8, myeloperoxidase, bacterial flora, serum C-reactive protein, or serum IL-6 or in changes in these parameters from baseline to first exacerbation over the 1-year study period.

CONCLUSIONS

Macrolide therapy was associated with a significant reduction in exacerbations compared with placebo and may be useful in decreasing the excessive disease burden in this important patient population. Clinical trial registered with www.clinicaltrials.gov (NCT 00147667).

Attenuation of Pseudomonas aeruginosa virulence by medicinal plants in a Caenorhabditis elegans model system

Expression of a myriad of virulence factors and innate antibiotic resistance enables the opportunistic human pathogen Pseudomonas aeruginosa to create intractable infections. Using a nematode model, we screened for novel inhibitors of this pathogen. Aqueous extracts of three plants, Conocarpus erectus, Callistemon viminalis and Bucida buceras, were examined for their effects on P. aeruginosa killing of the nematode Caenorhabditis elegans. The results were evaluated in toxin-based and infection-based assays using P. aeruginosa strains PAO1 and PA14. The tested plant extracts prevented mortality via gut infection in approximately 60 % of the worms and caused a 50-90 % reduction in death from toxin production. All extracts inhibited nematode death by P. aeruginosa without host toxicity, indicating their potential for further development as anti-infectives.

Small and rough colony pseudomonas aeruginosa with elevated biofilm formation ability isolated in hospitalized patients

Pseudomonas aeruginosa is a key pathogen of nosocomial infection, and causes persistent infection in patients with specific diseases like cystic fibrosis (CF). It has been reported that patients affected with CF discharge, at a high frequency, small colony variants with high adherence ability. In routine laboratory testing, we found atypical small and rough type (SR) colony variants of P. aeruginosa. The SRs and the counterpart wild type (WT) colonies showed similar biochemical features, antimicrobial susceptibilities, pulsed-field gel electrophoresis (PFGE) profiles, serotypes, and twitching motilities. The biofilm formation abilities of all the SR colonies, however, were extremely elevated as compared to those of the counterpart WT colonies. The frequency of SR-positive patients was 3.1% of the P. aeruginosa-positive inpatients (5/160), and that of the SR isolates was 0.6% of the P. aeruginosa strains (6/970) isolated in our laboratory over a period of 6 months. The SR-positive patients did not have any common disease or particular antibiotics treatment. The PFGE profiles showed that the SRs and the counterpart WTs were identical to each other, and also that three of the five SR/WT pairs were clonally similar. The three pairs were recovered from the feces, urine, and endotracheal secretion, respectively, of three patients hospitalized in two distinct wards. The results suggest that P. aeruginosa spontaneously produced highly adherent SR colonies in hospitalized patients, and these colonies may tend to spread in a hospital.

Suppression of Pseudomonas aeruginosa quorum-sensing systems by macrolides: a promising strategy or an oriental mystery?

A breakthrough in antibiotic chemotherapy for patients with chronic Pseudomonas aeruginosa pulmonary infections was brought about by findings in a patient with diffuse panbronchiolitis (DPB), who had been treated with erythromycin over a period of years. Recent clinical trials have demonstrated that long-term macrolide therapy can be used not only for DPB patients but also for those with other chronic infections, including patients with cystic fibrosis (CF). The pathogenesis of chronic P. aeruginosa infection is considered to arise from a bacterial cell-to-cell signaling mechanism, named "quorum-sensing", which enables the bacteria to coordinately turn on and off their virulence genes through the production of autoinducer molecules. Accumulating evidence from clinical and basic science fields suggests the potential of macrolides as Pseudomonas quorum-sensing inhibitors. In this review, we briefly summarize the data on the clinical efficacy of macrolides in DPB and CF patients. Then we discuss the mechanisms of action of macrolides from the viewpoint of sub-minimum inhibitory concentration (sub-MIC) macrolide effects on P. aeruginosa, particularly the potential activity of this antibiotic to suppress the bacterial quorum-sensing system.

Traitement de l'inflammation bronchique dans la mucoviscidose

Cystic fibrosis airway inflammation is characterized by neutrophilic efflux and high levels of proinflammatory cytokines such as IL-8 and IL-6. Inhaled corticosteroids are widely used despite lack of evidence of efficacity. Despite evidence of efficacity of ibuprofen, many clinicians have chosen not to use this therapy because of concerns regarding potential side effects. Azithromycin has antiinflammatory properties and is effective in cystic fibrosis (CF) patients. Deoxyribonuclease (rhDNase) has been shown to improve lung function in patients with cystic fibrosis and may also have a positive effect on inflammation. Other antiinflammatory drugs are in the process of validation.

Inhibition of quorum sensing-controlled virulence factor production in Pseudomonas aeruginosa by South Florida plant extracts

Quorum sensing (QS) is a key regulator of virulence and biofilm formation in Pseudomonas aeruginosa and other medically relevant bacteria. Aqueous extracts of six plants, Conocarpus erectus, Chamaesyce hypericifolia, Callistemon viminalis, Bucida buceras, Tetrazygia bicolor, and Quercus virginiana, were examined in this study for their effects on P. aeruginosa virulence factors and the QS system. C. erectus, B. buceras, and C. viminalis caused a significant inhibition of LasA protease, LasB elastase, pyoverdin production, and biofilm formation. Additionally, each plant presented a distinct effect profile on the las and rhl QS genes and their respective signaling molecules, suggesting that different mechanisms are responsible for efficacy. Extracts of all plants caused the inhibition of QS genes and QS-controlled factors, with marginal effects on bacterial growth, suggesting that the quorum-quenching mechanisms are unrelated to static or cidal effects.

Immunomodulatory effects of macrolide antibiotics in respiratory disease: therapeutic implications for asthma and cystic fibrosis

The macrolide antibiotics are a family of related 14- or 15-membered lactone ring antibiotics. There has been recent interest in the beneficial effects of these drugs as immune modulators in respiratory conditions in children. Cystic fibrosis (CF) and asthma, both of which occur in childhood, have an underlying inflammatory component and are associated with significant morbidity. The pathogenesis of both conditions is poorly understood but several molecular mechanisms have been suggested. In CF, these mechanisms broadly involve altered chloride transport and alteration of the airway surface liquid with disordered neutrophilic inflammation. There is much evidence for a proinflammatory propensity in CF immune effector and epithelial cells and many studies indicate that macrolides modulate these inflammatory processes. Recent studies have confirmed a clinical improvement in CF following treatment with macrolides, but the exact mechanisms by which they work are unknown. Asthma is likely to represent several different phenotypes but in all of these, airway obstruction, bronchial hyperresponsiveness, and inflammation are central processes. Results from trials using macrolides have suggested an improvement in clinical outcome. The putative mechanisms of macrolide immunomodulatory action include improvement of the primary defense mechanisms, inhibition of the bacteria-epithelial cell interaction, modulation of the signaling pathway and chemokine release, and direct neutrophil effects. Putative mechanisms of phenotypic modulation have also been proposed involving interactions with nitric oxide, endothelin-1, and bronchoconstriction, endothelial growth factors and airway remodeling, and bioactive phospholipids in both CF and asthma. Further characterization of these effects and development of targeted designer drugs will further expand our therapeutic repertoire and lead to improved quality and quantity of life for patients with CF and asthma.

Association of HLA genes with diffuse panbronchiolitis in Chinese patients

Diffuse panbronchiolitis (DPB) is a pulmonary disease of unknown etiology that predominantly affects East Asians, particularly Japanese with a prevalence of 0.00028. Research has shown that HLA-B54 and HLA-A11 are positively associated with this disease. HLA-A, -B, and -DR loci were analyzed using an oligonucleotide microarray in both Chinese patients with DPB and normal control subjects. The most marked difference between the patients and the controls was the decreased frequency of HLA-A2 (p=0.001, OR=0.12), which showed a negative association with the disease; however, there was no significant contribution of HLA-B loci. Interestingly, the frequency of HLA-A11 was increased (p=0.007, OR=3.9), in accordance with previous reports on Japanese and Koreans. In addition, the frequency of HLA-DRB5*010/020 slightly increased (p=0.049). The HLA-associated genes for DPB are located between the HLA-A and HLA-B loci. Differences in HLA-associated genes may partially explain differences in the incidence of DPB among different populations.

Maintenance azithromycin treatment in pediatric patients with cystic fibrosis: long-term outcomes related to macrolide resistance and pulmonary function

BACKGROUND

Maintenance azithromycin therapy may improve pulmonary function in patients with cystic fibrosis (CF) with Pseudomonas aeruginosa infection because of its antiinflammatory properties. However, azithromycin therapy might increase macrolide resistance in Staphylococcus aureus cultured from respiratory secretions. We studied the emergence of macrolide resistance in S. aureus and correlated this to pulmonary function decline in pediatric patients with CF on daily azithromycin therapy.

METHODS

Respiratory cultures of 100 patients with CF were analyzed for S. aureus colonization and its resistance pattern before and during 3 years after initiation of azithromycin maintenance therapy. Mean annual change in forced expiratory volume as percent of predicted (FEV1 %) was calculated to compare pulmonary function before and after azithromycin therapy.

RESULTS

Staphylococcal colonization did not significantly decrease after initiation of azithromycin (50% versus 48%). Before start of therapy, 10% of patients with staphylococcal colonization had macrolide-resistant strains. Staphylococcal resistance increased to 83% in the first year; 97% in the second and 100% in the third year after initiation of azithromycin therapy (P < 0.001). Half of macrolide-resistant S. aureus comprised the macrolide-lincosamide-streptogramin phenotype. Percent forced expiratory volume in 1 second improved in the first year after initiation of azithromycin (mean annual change: -4.75% before versus +3.09% after initiation; P < 0.01) but decreased during the second and third years after initiation (-5.15% and -3.65%, respectively). Emergence of macrolide-resistant S. aureus was not related to pulmonary function decline.

CONCLUSION

Maintenance azithromycin therapy in patients with CF leads to macrolide resistance in nearly all S. aureus carriers. Pulmonary function improvement after initiation of azithromycin therapy seems to be temporary and appears not to be related to macrolide resistance of S. aureus.

Immunization with 3-oxododecanoyl-L-homoserine lactone-protein conjugate protects mice from lethal Pseudomonas aeruginosa lung infection

Quorum-sensing systems have been reported to play a critical role in the pathogenesis of several bacterial infections. Recent data have demonstrated that Pseudomonas N-3-oxododecanoyl-L-homoserine lactone (3-oxo-C12-homoserine lactone, 3-oxo-C12-HSL), but not N-butanoyl-L-homoserine lactone (C4-HSL), induces apoptosis in macrophages and neutrophils. In the present study, the effects of active immunization with 3-oxo-C12-HSL-carrier protein conjugate on acute P. aeruginosa lung infection in mice were investigated. Immunization with 3-oxo-C12-HSL-BSA conjugate (subcutaneous, four times, at 2-week intervals) elaborated significant amounts of specific antibody in serum. Control and immunized mice were intranasally challenged with approximately 3 x 10(6) c.f.u. P. aeruginosa PAO1, and survival was then compared. All control mice died by day 2 post bacterial challenge, while 36 % of immunized mice survived to day 4 (P<0.05). Interestingly, bacterial numbers in the lungs did not differ between control and immunized groups, whereas the levels of pulmonary tumour necrosis factor (TNF)-alpha in the immunized mice were significantly lower than those of control mice (P<0.05). Furthermore, the extractable 3-oxo-C12-HSL levels in serum and lung homogenate were also significantly diminished in the immunized mice. Immune serum completely rescued reduction of cell viability by 3-oxo-C12-HSL-mediated apoptosis in macrophages in vitro. These results demonstrated that specific antibody to 3-oxo-C12-HSL plays a protective role in acute P. aeruginosa infection, probably through blocking of host inflammatory responses, without altering lung bacterial burden. The present data identify a promising potential vaccine strategy targeting bacterial quorum-sensing molecules, including autoinducers.

Azithromycin reduces spontaneous and induced inflammation in DeltaF508 cystic fibrosis mice

Background

Inflammation plays a critical role in lung disease development and progression in cystic fibrosis. Azithromycin is used for the treatment of cystic fibrosis lung disease, although its mechanisms of action are poorly understood. We tested the hypothesis that azithromycin modulates lung inflammation in cystic fibrosis mice.

Methods

We monitored cellular and molecular inflammatory markers in lungs of cystic fibrosis mutant mice homozygous for the ΔF508 mutation and their littermate controls, either in baseline conditions or after induction of acute inflammation by intratracheal instillation of lipopolysaccharide from Pseudomonas aeruginosa, which would be independent of interactions of bacteria with epithelial cells. The effect of azithromycin pretreatment (10 mg/kg/day) given by oral administration for 4 weeks was evaluated.

Results

In naive cystic fibrosis mice, a spontaneous lung inflammation was observed, characterized by macrophage and neutrophil infiltration, and increased intra-luminal content of the pro-inflammatory cytokine macrophage inflammatory protein-2. After induced inflammation, cystic fibrosis mice combined exaggerated cellular infiltration and lower anti-inflammatory interleukin-10 production. In cystic fibrosis mice, azithromycin attenuated cellular infiltration in both baseline and induced inflammatory condition, and inhibited cytokine (tumor necrosis factor-α and macrophage inflammatory protein-2) release in lipopolysaccharide-induced inflammation.

Conclusion

Our findings further support the concept that inflammatory responses are upregulated in cystic fibrosis. Azithromycin reduces some lung inflammation outcome measures in cystic fibrosis mice. We postulate that some of the benefits of azithromycin treatment in cystic fibrosis patients are due to modulation of lung inflammation.

Diffuse panbronchiolitis in East Asia

Diffuse panbronchiolitis is characterized by chronic sinobronchial infection and diffuse bilateral centrilobular lesions consisting of peribronchial infiltration of inflammatory cells. At present, it is known that diffuse panbronchiolitis is relatively restricted to East Asia. This uneven distribution is suspected to be highly associated with genetic predisposition located between human leucocyte antigen-A and -B loci. Low-dose, long-term macrolide therapy for the disease was suggested from a detailed observation of a single case that significantly improved by erythromycin therapy. Otherwise simple bactericidal activity of macrolides has been assumed as a candidate because of their clinical effect on the pathogenesis. In the last 10 years, the possible mechanism underlying the effectiveness of macrolide therapy has been dynamically investigated. To understand the pathological features and potential targets for macrolides in diffuse panbronchiolitis, the authors introduce the incidence of diffuse panbronchiolitis in East Asia, the profile of the disease and then trace the history of macrolide therapy in this review. The proposed mechanism of action includes the inhibition of excessive mucus and water secretion from the airway, the inhibition of neutrophil, and sometimes of lymphocyte and macrophage accumulating in the airway, the inhibition of transcription factors expressing several cytokines and the attenuation of bacterial virulence. Intracellular mechanisms of the action of macrolide are a hot topic of interest in research. The anti-inflammatory activity of macrolides is independent of their bactericidal effect, and a new anti-inflammatory analogue without antimicrobial activity should be developed to minimize the emergence of macrolide-resistant microorganisms and to maintain the safety of this treatment.

Treatment of chronic rhinosinusitis with low-dose, long-term macrolide antibiotics: an evolving paradigm

The 14-membered and 15-membered ring macrolide antibiotics express immunomodulatory effects in chronic respiratory disorders in humans that are distinct from their antimicrobial properties. These drugs downregulate the excessive immune and inflammatory responses observed in these conditions while promoting tissue repair. To this end, chronic rhinosinusitis is characterized by mucosal inflammation of nasal and sinus mucosa for more than 3 months and accounts for significant health care resource allocation due to difficulties in treatment. Clinical efficacy of macrolide antibiotics as biologic response modifiers in patients with chronic rhinosinusitis is suggested by compelling basic research and small, uncontrolled clinical studies. Hence, long-term, prospective double-blind placebo-controlled clinical studies are indicated to establish the utility of these drugs in the treatment of patients with chronic rhinosinusitis.

Long-term azithromycin in cystic fibrosis: another possible mechanism of action?

Azithromycin is used for the treatment of cystic fibrosis lung disease, although its mechanisms of action are not completely understood. Besides its antiinflammatory and antimicrobial activities, one possibility could be the overexpression induction of the multidrug resistance-associated protein (MRP), which could affect chloride transport, thus overcoming the ion transport defect of cystic fibrosis. Seven patients were evaluated before and after 4 weeks of azithromycin treatment (500 mg once daily). Ion transport was studied in vivo by measuring nasal potential difference (NPD). MRP mRNA expression was studied in nasal cells by an internal standard-based semiquantitative RT-PCR assay. NPD was consistent with cystic fibrosis before treatment. After azithromycin treatment, sodium transport was still impaired, whereas a significant increase in chloride conductance was observed (p = 0.03). A significant direct correlation was found between MRP mRNA expression levels and NPD chloride response after azithromycin treatment (p = 0.04, r = 0.78). In conclusion, azithromycin may induce MRP overexpression and restore chloride conductance in the airways of cystic fibrosis patients. These findings suggest a new potential role of azithromycin in the treatment of cystic fibrosis pulmonary disease, i.e. the possibility to upregulate proteins whose function may, at least in part, compensate for the basic defect of cystic fibrosis.