Direct evidence for antipseudomonal activity of macrolides: exposure-dependent bactericidal activity and inhibition of protein synthesis by erythromycin, clarithromycin, and azithromycin

Increased susceptibility to azithromycin of Pseudomonas aeruginosa biofilms using RPMI 1640 testing media

Azithromycin (AZM) is efficient for treatment of chronic Pseudomonas aeruginosa biofilm lung infections, despite of resistance in conventional susceptibility testing. It has been shown that planktonic P. aeruginosa are more susceptible to AZM when tested in RPMI 1640 medium. The aim of the study was to test the susceptibility to AZM of P. aeruginosa biofilms in LB vs RPMI 1640 media. We investigated the effect of AZM on planktonic and biofilms of (WT) P. aeruginosa (PAO1), the hypermutable (ΔmutS) and the antibiotic-resistant phenotype(ΔnfxB) mutants. The effect of AZM on young and mature biofilms was investigated in the modified Calgary Biofilm Device by estimation of the minimal biofilm inhibitory concentration (MBIC). The AZM MBIC90 in LB/RPMI1640 on young biofilms treated for 24 h was 16/4 μg/mL for PAO1, 32/8 μg/mL for ΔmutS, and 256/16 μg/mL for ΔnfxB, while in mature biofilms was 256/2 μg/mL for PAO1 and ΔmutS and 16/1 μg/mL for ΔnfxB. The effect of AZM was improved when the treatment was prolonged to 72 h, supporting the intracellular accumulation of AZM. An increased susceptibility of P. aeruginosa biofilms to AZM was observed in RPMI 1640 than in LB medium. Our results might improve susceptibility testing and dosing of AZM for treatment of biofilm infections.

Macrolide-loaded nanofibrous inserts with polycaprolactone and cellulose acetate base for sustained ocular delivery: Pharmacokinetic study in Rabbit's eye

The present study aimed to prepare nanofibrous inserts for sustained ocular drug delivery of Azithromycin (AZM) toward conquering the obstacles of conventional topical drug delivery. Nanofibers were fabricated by electrospinning using polycaprolactone (PCL) and cellulose acetate (CA) which are biocompatible and biodegradable polymers. Prepared nanofibers were evaluated in terms of physicochemical, morphological properties, pharmacokinetic study and ocular irritation. SEM images revealed average diameters of about 160 nm and 190 nm for CA and PCL nanofibers, respectively. These ocular drug delivery systems were strong, flexible, and stable under humid and dry conditions. Quantification was performed using microbiological assay by M. luteus as a microorganism. While PCL-based nanofibrous inserts released AZM in a two-step manner initiated by a burst release via Peppas kinetical model, CA-based inserts showed a gradual release profile without any burst release which followed the first-order model. Results showed that these inserts were non-cytotoxic and non-irritating. The nanofibers showed antibacterial efficacy against Escherichia coli and Staphylococcus aureus. In addition, according to a pharmacokinetic study in Rabbit's Eye, a higher Cmax and lower Tmax were achieved by PCL nanofibers compared to CA-based ones. The pharmacokinetic study of nanofibers in rabbit eyes showed that all formulations were able to maintain the effective concentration of AZM for about 6 days. In conclusion, the prepared nanofibers can be effectively utilized for prolonged ocular delivery of AZM in the treatment of conjunctival infections.

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.

Animal models of chronic and recurrent Pseudomonas aeruginosa lung infection: significance of macrolide treatment

Animal models of human diseases are invaluable and inevitable elements in identifying and testing novel treatments for serious diseases, including severe infections. Planning and conducting investigator-initiated human trials are generally accepted as being enormously challenging. In contrast, it is often underestimated how much planning, including background and modifying experiments, is needed to establish a relevant infectious disease animal model. However, representative animal infectious models, well designed to test generated hypotheses, are useful to improve our understanding of pathogenesis, virulence factors and host response and to identify novel treatment candidates and therapeutic strategies. Such results can subsequently proceed to clinical testing if suitable. The present review aims at presenting all the pulmonary Pseudomonas aeruginosa infectious models we have knowledge of and the detailed descriptions of established animal models in our laboratory focusing on macrolide therapy are presented.

N-acyl homoserine lactone molecules assisted quorum sensing: effects consequences and monitoring of bacteria talking in real life

Bacteria utilize small signal molecules to monitor population densities. Bacteria arrange gene regulation in a method called Quorum Sensing (QS). The most widespread signalling molecules are N-Acyl Homoserine Lactones (AHLs/HSLs) for Gram-negative bacteria communities. QS plays significant role in the organizing of the bacterial gene that adapts to harsh environmental conditions for bacteria. It is involved in the arrangement of duties, such as biofilm formation occurrence, virulence activity of bacteria, production of antibiotics, plasmid conjugal transfer incident, pigmentation phenomenon and production of exopolysaccharide (EPS). QS obviously impacts on human health, agriculture and environment. AHL-related QS researches have been extensively studied and understood in depth for cell to cell intercommunication channel in Gram-negative bacteria. It is understood that AHL-based QS research has been extensively studied for cell-to-cell communication in Gram-negative bacteria; hence, a comprehensive study of AHLs, which are bacterial signal molecules, is required. The purpose of this review is to examine the effects of QS-mediated AHLs in many areas by looking at them from a different perspectives, such as clinic samples, food industry, aquatic life and wastewater treatment system.

Exploring the possible targeting strategies of liposomes against methicillin-resistant Staphylococcus aureus (MRSA)

Multi antibiotic-resistant bacterial infections are on the rise due to the overuse of antibiotics. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the pathogens listed under the category of serious threats where vancomycin remains the mainstay treatment despite the availability of various antibacterial agents. Recently, decreased susceptibility to vancomycin from clinical isolates of MRSA has been reported and has drawn worldwide attention as it is often difficult to overcome and leads to increased medical costs, mortality, and longer hospital stays. Development of antibiotic delivery systems is often necessary to improve bioavailability and biodistribution, in order to reduce antibiotic resistance and increase the lifespan of antibiotics. Liposome entrapment has been used as a method to allow higher drug dosing apart from reducing toxicity associated with drugs. The surface of the liposomes can also be designed and enhanced with drug-release properties, active targeting, and stealth effects to prevent recognition by the mononuclear phagocyte system, thus enhancing its circulation time. The present review aimed to highlight the possible targeting strategies of liposomes against MRSA bacteremia systemically while investigating the magnitude of this effect on the minimum inhibitory concentration level.

Azithromycin Exhibits Activity Against Pseudomonas aeruginosa in Chronic Rat Lung Infection Model

Pseudomonas aeruginosa forms biofilms in the lungs of chronically infected cystic fibrosis patients, which are tolerant to both the treatment of antibiotics and the host immune system. Normally, antibiotics are less effective against bacteria growing in biofilms; azithromycin has shown a potent efficacy in cystic fibrosis patients chronically infected with P. aeruginosa and improved their lung function. The present study was conducted to evaluate the effect of azithromycin on P. aeruginosa biofilm. We show that azithromycin exhibited a potent activity against P. aeruginosa biofilm, and microscopic observation revealed that azithromycin substantially inhibited the formation of solid surface biofilms. Interestingly, we observed that azithromycin restricted P. aeruginosa biofilm formation by inhibiting the expression of pel genes, which has been previously shown to play an essential role in bacterial attachment to solid-surface biofilm. In a rat model of chronic P. aeruginosa lung infection, we show that azithromycin treatment resulted in the suppression of quorum sensing-regulated virulence factors, significantly improving the clearance of P. aeruginosa biofilms compared to that in the placebo control. We conclude that azithromycin attenuates P. aeruginosa biofilm formation, impairs its ability to produce extracellular biofilm matrix, and increases its sensitivity to the immune system, which may explain the clinical efficacy of azithromycin in cystic fibrosis patients.

Could Azithromycin Be Part of Pseudomonas aeruginosa Acute Pneumonia Treatment?

Azithromycin (AZM) is a 15-membered-ring macrolide that presents a broad-spectrum antimicrobial activity against Gram-positive bacteria and atypical microorganisms but suffers from a poor diffusion across the outer-membrane of Gram-negative bacilli, including Pseudomonas aeruginosa (PA). However, AZM has demonstrated clinical benefits in patients suffering from chronic PA respiratory infections, especially cystic fibrosis patients. Since the rise of multidrug-resistant PA has led to a growing need for new therapeutic options, this macrolide has been proposed as an adjunctive therapy. Clinical trials assessing AZM in PA acute pneumonia are scarce. However, a careful examination of the available literature provides good rationales for its use in that context. In fact, 14- and 15-membered-ring macrolides have demonstrated immunomodulatory and immunosuppressive effects that could be of major interest in the management of acute illness. Furthermore, growing evidence supports a downregulation of PA virulence dependent on direct interaction with the ribosomes, and based on the modulation of several key regulators from the Quorum Sensing network. First highlighted in vitro, these interesting properties of AZM have subsequently been confirmed in the animal models. In this review, we systematically analyzed the literature regarding AZM immunomodulatory and anti-PA effects. In vitro and in vivo studies, as well as clinical trials were reviewed, looking for rationales for AZM use in PA acute pneumonia.

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.

A Quantitative Survey of Bacterial Persistence in the Presence of Antibiotics: Towards Antipersister Antimicrobial Discovery

Background: Bacterial persistence to antibiotics relates to the phenotypic ability to survive lethal concentrations of otherwise bactericidal antibiotics. The quantitative nature of the time-kill assay, which is the sector's standard for the study of antibiotic bacterial persistence, is an invaluable asset for global, unbiased, and cross-species analyses. Methods: We compiled the results of antibiotic persistence from antibiotic-sensitive bacteria during planktonic growth. The data were extracted from a sample of 187 publications over the last 50 years. The antibiotics used in this compilation were also compared in terms of structural similarity to fluorescent molecules known to accumulate in Escherichia coli. Results: We reviewed in detail data from 54 antibiotics and 36 bacterial species. Persistence varies widely as a function of the type of antibiotic (membrane-active antibiotics admit the fewest), the nature of the growth phase and medium (persistence is less common in exponential phase and rich media), and the Gram staining of the target organism (persistence is more common in Gram positives). Some antibiotics bear strong structural similarity to fluorophores known to be taken up by E. coli, potentially allowing competitive assays. Some antibiotics also, paradoxically, seem to allow more persisters at higher antibiotic concentrations. Conclusions: We consolidated an actionable knowledge base to support a rational development of antipersister antimicrobials. Persistence is seen as a step on the pathway to antimicrobial resistance, and we found no organisms that failed to exhibit it. Novel antibiotics need to have antipersister activity. Discovery strategies should include persister-specific approaches that could find antibiotics that preferably target the membrane structure and permeability of slow-growing cells.

Integration of Bioinformatics and in vitro Analysis Reveal Anti-leishmanial Effects of Azithromycin and Nystatin

Background:

Leishmaniasis is the major cause of mortality in under-developed countries. One of the main problems in leishmaniasis is the limited number of drug options, resistance and side effects. Such a situation requires to study the new chemical series with anti-leishmanial activity.

Objective:

To assess the anti-leishmanial activity of antibacterial and antifungal drugs.

Methods:

We have applied an integrative approach based on computational and in vitro methods to elucidate the efficacy of different antibacterial and antifungal drugs against Leishmania tropica (KWH23). Firstly these compounds were analyzed using in silico molecular docking. This analysis showed that the nystatin and azithromycin interacted with the active site amino acids of the target protein leishmanolysin. The nystatin, followed by azithromycin, produced the lowest binding energies indicating their inhibitive activity against the target. The efficacy of the docked drugs was further validated in vitro which showed that our bioinformatics based predictions completely agreed with experimental results. Stock solutions of drugs, media preparation and parasites cultures were performed according to the standard in-vitro protocol.

Results:

We found that the half maximal inhibitory concentration (IC50) value of dosage form of nystatin (10,000,00 U) and pure nystatin was 0.05701 µM and 0.00324 µM respectively. The IC50 value of combined azithromycin and nystatin (dosage and pure form) was 0.156 µg/ml and 0.0023 µg /ml (0.00248 µM) respectively. It was observed that IC50 value of nystatin is better than azithromycin and pure form of drugs had significant activity than the dosage form of drugs.

Conclusion:

From these results, it was also proven that pure drugs combination result is much better than all tested drugs results. The results of both in vitro and in silico studies clearly indicated that comparatively, nystatin is the potential candidate drug in combat against Leishmania tropica.

Macrolides Inhibit Capsule Formation of Highly Virulent Cryptococcus gattii and Promote Innate Immune Susceptibility

Cryptococcus gattii is a fungal pathogen, endemic in tropical and subtropical regions, the west coast of Canada, and the United States, that causes a potentially fatal infection in otherwise healthy individuals. Because the cryptococcal polysaccharide capsule is a leading virulence factor due to its resistance against innate immunity, the inhibition of capsule formation may be a promising new therapeutic strategy for C. gattii Macrolides have numerous nonantibiotic effects, including immunomodulation of mammalian cells and suppression of bacterial (but not fungal) pathogenicity. Thus, we hypothesized that a macrolide would inhibit cryptococcal capsule formation and improve the host immune response. Coincubation with clarithromycin (CAM) and azithromycin significantly reduced the capsule thickness and the amount of capsular polysaccharide of both C. gattii and C. neoformans CAM-treated C. gattii cells were significantly more susceptible to H₂O₂ oxidative stress and opsonophagocytic killing by murine neutrophils. In addition, more C. gattii cells were phagocytosed by murine macrophages, resulting in increased production of tumor necrosis factor alpha (TNF-α) by CAM exposure. After CAM exposure, dephosphorylation of Hog1, one of the mitogen-activated protein kinase (MAPK) signaling pathways of Cryptococcus, was observed in Western blot analysis. In addition, CAM exposure significantly reduced the mRNA expression of LAC1 and LAC2 (such mRNA expression is associated with cell wall integrity and melanin production). These results suggest that CAM may aid in inhibiting capsular formation via the MAPK signaling pathway and by suppressing virulent genes; thus, it may be a useful adjunctive agent for treatment of refractory C. gattii infection.

Azithromycin Modulates 3',5'-cyclic Diguanylic Acid Signaling in Pseudomonas aeruginosa

Macrolides have been reported to exert a variety of effects on both host immunomodulation and repression of bacterial pathogenicity. In this study, we report that the 3',5'-cyclic diguanylic acid (c-di-GMP) signaling system, which regulates virulence in Pseudomonas aeruginosa, is affected by the macrolide azithromycin. Using DNA microarray analysis, we selected a gene encoding PA2567 related to c-di-GMP metabolism that was significantly affected by azithromycin treatment. Expression of the PA2567 gene was significantly repressed by azithromycin in a time- and dose-dependent manner, whereas no difference in PA2567 gene expression was observed in the absence of azithromycin. In-frame deletion of the PA2567 gene affected both virulence factors and the quorum-sensing system, and significantly decreased total bacteria in a mouse pneumonia model compared to the wild-type strain (P < 0.05). These results suggest that macrolides possess the ability to modulate c-di-GMP intracellular signaling in P. aeruginosa.

Novel antimicrobial peptide-modified azithromycin-loaded liposomes against methicillin-resistant Staphylococcus aureus

Infections caused by multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), have become a public threat; therefore, development of new antimicrobial drugs or strategies is urgently required. In this study, a new antibacterial peptide DP7-C (Chol-suc-VQWRIRVAVIRK-NH2) and DP7-C-modified azithromycin (AZT)-loaded liposomes (LPs) are developed for the treatment of MRSA infection, and it was found that DP7-C inserted into the LP lipid bilayer not only functioned as a carrier to encapsulate the antibiotic AZT but also synergized the antibacterial effect of the encapsulated AZT. In vitro assays showed that DP7-C-modified LPs possessed sustained drug release profile and immune regulatory effect and did not show obvious cytotoxicity in mammal cells, but they did not possess direct antibacterial activity in vitro. In vivo studies revealed that DP7-C-modified LPs did not exhibit obvious side effects or toxicity in mice but were able to significantly reduce the bacterial counts in an MRSA-infectious mouse model and possessed high antibacterial activity. In particular, DP7-C-modified AZT-loaded LPs showed more positive therapeutic effects than either DP7-C-modified blank LPs or nonmodified AZT-loaded LPs treatment alone. Molecular mechanism studies demonstrated that DP7-C formulations effectively upregulated the production of anti-inflammatory cytokines and chemokines without inducing harmful immune response, suggesting that DP7-C was synergistic with AZT against the bacterial infection by activating the innate immune response. Most importantly, although DP7-C activated the innate immune response, it did not possess direct antibacterial activity in vitro, indicating that DP7-C did not possess the potential to induce bacteria resistance. The findings indicate that DP7-C-modified AZT-loaded LPs developed in this study have a great potential required for the clinical treatment of MRSA infections.

Ciprofloxacin plus erythromycin or ambroxol ameliorates endotracheal tube-associated Pseudomonas aeruginosa biofilms in a rat model

BACKGROUND AND OBJECTIVE

Pseudomonas aeruginosa is a multi-drug resistant bacterium, with its biofilm-growing mucoid (alginate-producing) strains being particularly resistant. As atomized drug administration is a common practice in pediatric patients, we compared the effect of inhalational therapy with erythromycin plus ciprofloxacin, with that of ambroxol plus ciprofloxacin, against biofilm producing strains of P. aeruginosa.

RESULTS

Both combined treatment regimens were associated with a significant reduction in bacterial counts in endotracheal (ET) tubes and lungs, as compared to that observed with ambroxol and erythromycin monotherapies (P<0.05). Ciprofloxacin plus ambroxol appeared to have a higher efficacy than ciprofloxacin plus erythromycin, both in lowering bacterial counts (P<0.05) and in disrupting the structural integrity of biofilm. Histopathological changes in the lungs were milder in the two combined treatment groups, as compared to that in groups treated with single drugs.

CONCLUSION

Erythromycin or ambroxol in combination with ciprofloxacin could eliminate P. aeruginosa biofilms. When combined with ciprofloxacin, ambroxol outperformed erythromycin in eradicating P. aeruginosa biofilm.

Mass Spectrometry Analysis of Pseudomonas aeruginosa Treated with Azithromycin

In microbiology, changes in specialized metabolite production (cell-to-cell signaling metabolites, virulence factors, and natural products) are measured using phenotypic assays. However, advances in mass spectrometry-based techniques including imaging mass spectrometry (IMS) now allow researchers to directly visualize the production of specialized metabolites from microbial colony biofilms. In this study, a combination of IMS and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to visualize the effect of the macrolide antibiotic azithromycin (AZM) on colony biofilms of Pseudomonas aeruginosa. Although previous research suggested that AZM may inhibit cell-to-cell signaling of P. aeruginosa and thereby reduce pathogenicity, we observed no clear decrease in specialized metabolite production.

Biofilm-related infections: bridging the gap between clinical management and fundamental aspects of recalcitrance toward antibiotics

Surface-associated microbial communities, called biofilms, are present in all environments. Although biofilms play an important positive role in a variety of ecosystems, they also have many negative effects, including biofilm-related infections in medical settings. The ability of pathogenic biofilms to survive in the presence of high concentrations of antibiotics is called "recalcitrance" and is a characteristic property of the biofilm lifestyle, leading to treatment failure and infection recurrence. This review presents our current understanding of the molecular mechanisms of biofilm recalcitrance toward antibiotics and describes how recent progress has improved our capacity to design original and efficient strategies to prevent or eradicate biofilm-related infections.

Antivirulence activity of azithromycin in Pseudomonas aeruginosa

Antibiotics represent our bulwark to combat bacterial infections, but the spread of antibiotic resistance compromises their clinical efficacy. Alternatives to conventional antibiotics are urgently needed in order to complement the existing antibacterial arsenal. The macrolide antibiotic azithromycin (AZM) provides a paradigmatic example of an "unconventional" antibacterial drug. Besides its growth-inhibiting activity, AZM displays potent anti-inflammatory properties, as well as antivirulence activity on some intrinsically resistant bacteria, such as Pseudomonas aeruginosa. In this bacterium, the antivirulence activity of AZM mainly relies on its ability to interact with the ribosome, resulting in direct and/or indirect repression of specific subsets of genes involved in virulence, quorum sensing, biofilm formation, and intrinsic antibiotic resistance. Both clinical experience and clinical trials have shown the efficacy of AZM in the treatment of chronic pulmonary infections caused by P. aeruginosa. The aim of this review is to combine results from laboratory studies with evidence from clinical trials in order to unify the information on the in vivo mode of action of AZM in P. aeruginosa infection.

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.

Azithromycin inhibits expression of the GacA-dependent small RNAs RsmY and RsmZ in Pseudomonas aeruginosa

Azithromycin at clinically relevant doses does not inhibit planktonic growth of the opportunistic pathogen Pseudomonas aeruginosa but causes markedly reduced formation of biofilms and quorum-sensing-regulated extracellular virulence factors. In the Gac/Rsm signal transduction pathway, which acts upstream of the quorum-sensing machinery in P. aeruginosa, the GacA-dependent untranslated small RNAs RsmY and RsmZ are key regulatory elements. As azithromycin treatment and mutational inactivation of gacA have strikingly similar phenotypic consequences, the effect of azithromycin on rsmY and rsmZ expression was investigated. In planktonically growing cells, the antibiotic strongly inhibited the expression of both small RNA genes but did not affect the expression of the housekeeping gene proC. The azithromycin treatment resulted in reduced expression of gacA and rsmA, which are known positive regulators of rsmY and rsmZ, and of the PA0588-PA0584 gene cluster, which was discovered as a novel positive regulatory element involved in rsmY and rsmZ expression. Deletion of this cluster resulted in diminished ability of P. aeruginosa to produce pyocyanin and to swarm. The results of this study indicate that azithromycin inhibits rsmY and rsmZ transcription indirectly by lowering the expression of positive regulators of these small RNA genes.

Mechanisms of action and clinical application of macrolides as immunomodulatory medications

Macrolides have diverse biological activities and an ability to modulate inflammation and immunity in eukaryotes without affecting homeostatic immunity. These properties have led to their long-term use in treating neutrophil-dominated inflammation in diffuse panbronchiolitis, bronchiectasis, rhinosinusitis, and cystic fibrosis. These immunomodulatory activities appear to be polymodal, but evidence suggests that many of these effects are due to inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and nuclear factor kappa B (NF-kappaB) activation. Macrolides accumulate within cells, suggesting that they may associate with receptors or carriers responsible for the regulation of cell cycle and immunity. A concern is that long-term use of macrolides increases the emergence of antimicrobial resistance. Nonantimicrobial macrolides are now in development as potential immunomodulatory therapies.

Azithromycin paradox in the treatment of cystic fibrosis airway disease

Evaluation of: Saiman L, Anstead M, Mayer-Hamblett N et al.: Effect of azithromycin on pulmonary function in patients with cystic fibrosis uninfected with Pseudomonas aeruginosa: a randomized controlled trial. JAMA 303(17), 1707–1715 (2010). Chronic airway infection and inflammation are hallmarks of cystic fibrosis (CF). Disease progression can be described as chronic inflammation punctuated by acute exacerbations with overt immunological responses. Macrolide antibiotics, which have both immunomodulatory and antibacterial activities, have been shown to be beneficial in the management of CF airway disease, although the mechanism of action is unknown. It is also unclear whether all patients, particularly those not colonized with Pseudomonas aeruginosa, benefit from this treatment. In this article, Saiman et al. examine the effects of azithromycin on lung function in pediatric and adolescent CF patients who are not colonized with P. aeruginosa. The data indicate beneficial effects of azithromycin treatment and suggest the mechanisms of action of azithromycin is at least partially independent of P. aeruginosa.

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 immunomodulation of chronic respiratory diseases

Important immunomodulatory properties of 14- and 15-membered macrolides may benefit patients with respiratory diseases associated with chronic inflammation. These properties include decreased neutrophil chemotaxis and infiltration into the respiratory epithelium, inhibition of transcription factors leading to decreased proinflammatory cytokine production, downregulation of adhesion molecule expression, inhibition of microbial virulence factors including biofilm formation, reduced generation of oxygen-free radicals, enhanced neutrophil apoptosis, and decreased mucus hypersecretion with improved mucociliary clearance. Chronic, low-dose macrolides have dramatically improved survival in patients with diffuse panbronchiolitis (DPB). Given the overlap in pathogenesis between DPB and other chronic respiratory diseases, macrolides are being investigated for cystic fibrosis, asthma, chronic bronchitis, chronic sinusitis, and chronic obstructive pulmonary disease. Preliminary data (largely from open-label trials) are promising, but conclusive results are needed.

Azithromycin is associated with increased survival in lung transplant recipients with bronchiolitis obliterans syndrome

BACKGROUND

Previous studies have suggested that azithromycin improves lung function in lung transplant recipients with bronchiolitis obliterans syndrome (BOS). However, these studies did not include a non-treated BOS control cohort or perform survival analysis. This study was undertaken to estimate the effect of azithromycin treatment on survival in lung transplant recipients with BOS.

METHODS

We conducted a retrospective cohort study of consecutive lung transplant recipients who developed BOS between 1999 and 2007. An association between azithromycin treatment and death was assessed using univariate and multivariate time-dependent Cox regression analysis.

RESULTS

Of the 178 recipients who developed BOS in our study, 78 did so after 2003 and were treated with azithromycin. The azithromycin-treated and untreated cohorts had similar baseline characteristics. Univariate analysis demonstrated that azithromycin treatment was associated with a survival advantage and this beneficial treatment effect was more pronounced when treatment was initiated during BOS Stage 1. Multivariate analysis demonstrated azithromycin treatment during BOS Stage 1 (adjusted hazard ratio = 0.23, p = 0.01) and absolute forced expiratory volume in 1 second (FEV(1)) at the time of BOS Stage 1 (adjusted hazard ratio = 0.52, p = 0.003) were both associated with a decreased risk of death.

CONCLUSIONS

In lung transplant recipients with BOS Stage 1, azithromycin treatment initiated before BOS Stage 2 was independently associated with a significant reduction in the risk of death. This finding supports the need for a randomized, controlled trial to confirm the impact of azithromycin on survival in lung transplant recipients.

[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.

Effects of prolonged use of azithromycin in patients with cystic fibrosis: a meta-analysis

Azithromycin has been studied as potential therapeutic anti-inflammatory agent for cystic fibrosis (CF) patients. Azithromycin (AZM) has been used as an immunomodulating agent, based on few small studies. Considering the cost and potential side effects of long-term azithromycin therapy, it is important to identify the group of patients that would benefit the most. Weighted mean difference was used for pulmonary function tests, and risk ratios for all other variables. The random-effects model was applied for all reports. Combining four studies (N=368), azithromycin showed increase in FEV(1) (3.53%, 95% CI 0.00, 7.07, p=0.05; I(2)=38%) and FVC (4.24%, 95% CI 2.02, 6.45, p=0.0002; I(2)=0%). When trials were analyzed by baseline Pseudomonas sputum colonization, the heterogeneity decreased (I(2)=0%), FEV(1) significantly increased to 4.66% (95% CI 1.18, 8.15, p=0.009), and FVC increased to 4.64% (95% CI 2.11, 7.17, p=0.0003). The GI side effects were 72% higher with azithromycin use (RR 1.72, 95% CI 1.33, 2.21, p=0.00003), the main side effects being nausea (RR 2.04, 95% CI 1.19, 3.45, p=0.009), and diarrhea (RR 2.12, 95% CI 1.10, 4.08, p=0.02). Azithromycin improves lung function of CF patients, especially in the subgroup colonized with Pseudomonas. However, nausea and diarrhea are significantly more frequent with azythromycin.

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.

Cystic fibrosis lung disease in adult patients

As the longevity of all patients with cystic fibrosis (CF) continues to increase (median 2005 survival=36.8 years), more adult patients will be receiving their medical care from nonpediatric adult-care providers. Cystic fibrosis remains a fatal disease, with more than 80% of patients dying after the age of 18 years, and most deaths resulting from pulmonary disease. The changing epidemiology requires adult-care providers to become knowledgeable and competent in the clinical management of adults with CF. Physicians must understand the influence of specific genotype on phenotypic disease presentation and severity, the pathogenic factors determining lung disease onset and progression, the impact of comorbid disease factors such as CF-related diabetes and malnutrition upon lung disease severity, and the currently approved or standard accepted therapies used for chronic management of CF lung disease. This knowledge is critical to help alleviate morbidity and improve mortality for the rapidly expanding population of adults with CF.

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.

Macrolides in cystic fibrosis

Cystic fibrosis (CF) results in chronic pulmonary disease in the majority of patients resulting from the production of viscous secretions and impairment of mucociliary clearance due to alterations in airway surface liquid. Chronic infection results, and the combination of tissue damage by pathogenic organisms and a robust host inflammatory response leads to the development of bronchiectasis and progressive lung disease. Macrolide antibiotics have demonstrated efficacy in diffuse panbronchiolitis, a disease that shares many similarities to CF, and this has generated interest in the use of these agents in patients who have CF. The authors review the data that demonstrate clinical benefits of long-term azithromycin administration in patients who have CF and discuss potential host- and pathogen-related explanations for the positive therapeutic effect.

Azithromycin blocks quorum sensing and alginate polymer formation and increases the sensitivity to serum and stationary-growth-phase killing of Pseudomonas aeruginosa and attenuates chronic P. aeruginosa lung infection in Cftr(-/-) mice

The consequences of O-acetylated alginate-producing Pseudomonas aeruginosa biofilms in the lungs of chronically infected cystic fibrosis (CF) patients are tolerance to both antibiotic treatments and effects on the innate and the adaptive defense mechanisms. In clinical trials, azithromycin (AZM) has been shown to improve the lung function of CF patients. The present study was conducted in accordance with previous in vitro studies suggesting that the effect of AZM may be the inhibition of alginate production, blockage of quorum sensing (QS), and increased sensitivity to hydrogen peroxide and the complement system. Moreover, we show that AZM may affect the polymerization of P. aeruginosa alginate by the incomplete precipitation of polymerized alginate and high levels of readily dialyzable uronic acids. In addition, we find that mucoid bacteria in the stationary growth phase became sensitive to AZM, whereas cells in the exponential phase did not. Interestingly, AZM-treated P. aeruginosa lasI mutants appeared to be particularly resistant to serum, whereas bacteria with a functional QS system did not. We show in a CF mouse model of chronic P. aeruginosa lung infection that AZM treatment results in the suppression of QS-regulated virulence factors, significantly improves the clearance of P. aeruginosa alginate biofilms, and reduces the severity of the lung pathology compared to that in control mice. We conclude that AZM attenuates the virulence of P. aeruginosa, impairs its ability to form fully polymerized alginate biofilms, and increases its sensitivity to complement and stationary-phase killing, which may explain the clinical efficacy of AZM.

Pharmacokinetics and sputum penetration of azithromycin during once weekly dosing in cystic fibrosis patients

In this study we examined pharmacokinetics, systemic exposure and sputum penetration of azithromycin (AZM) in CF patients on chronic daily AZM therapy after changing to a once weekly dosing scheme. Eight adult CF patients using AZM 500 mg/day were changed to a once weekly dose of 1000 mg during 3 months. Once per month sputum and blood samples were collected. AZM was quantified in blood plasma and polymorphonuclear neutrophils. The cumulative weekly dose was reduced with a factor of 3.5 (7x500 mg vs. 1x1000 mg weekly). This led to a reduction in area under the curve (AUC+/-S.D.) with a factor of 2.5+/-0.8 in plasma, 2.8+/-0.9 in blood, 2.2+/-1.1 in PMNNs and to a reduction in average sputum concentration with a factor of 3.0 (+/-1.5). At 1000 mg once weekly reduced but still substantial concentrations were achieved in PMNNs and in sputum. Although not significant, a tendency towards less than linear reduction was found. In order to calculate and propose an optimal dosing scheme we need to establish a relation between exposure levels and clinical efficacy.

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.

Quorum-sensing antagonistic activities of azithromycin in Pseudomonas aeruginosa PAO1: a global approach

The administration of macrolides such as azithromycin for chronic pulmonary infection of cystic fibrosis patients has been reported to be of benefit. Although the mechanisms of action remain obscure, anti-inflammatory effects as well as interference of the macrolide with Pseudomonas aeruginosa virulence factor production have been suggested to contribute to an improved clinical outcome. In this study we used a systematic approach and analyzed the impact of azithromycin on the global transcriptional pattern and the protein expression profile of P. aeruginosa PAO1 cultures versus those in untreated controls. The most remarkable result of this study is the finding that azithromycin exhibited extensive quorum-sensing antagonistic activities. In accordance with the inhibition of the quorum-sensing systems, virulence factor production was diminished and the oxidative stress response was impaired, whereas the type III secretion system was strongly induced. Moreover, P. aeruginosa motility was reduced, which probably accounts for the previously observed impaired biofilm formation capabilities of azithromycin-treated cultures. The interference of azithromycin with quorum-sensing-dependent virulence factor production, biofilm formation, and oxidative stress resistance in P. aeruginosa holds great promise for macrolide therapy in cystic fibrosis. Clearly quorum-sensing antagonist macrolides should be paid more attention in the management of chronic P. aeruginosa infections, and as quorum-sensing antagonists, macrolides might gain vital importance for more general application against chronic infections.

Microbiologic and immunologic evaluation of a single high dose of azithromycin for treatment of experimental Mycoplasma pneumoniae pneumonia

We evaluated the efficacy of azithromycin therapy given as a single high dose or divided over 5 days for the treatment of mild experimental Mycoplasma pneumoniae pneumonia. Although both azithromycin regimens significantly reduced quantitative cultures, lung histopathology, and pulmonary cytokines and chemokines, there were no significant differences between the two regimens.

Effects of azithromycin on clinical isolates of Pseudomonas aeruginosa from cystic fibrosis patients

There is considerable interest in the use of azithromycin for the treatment of lung disease in patients with cystic fibrosis (CF). Although its mechanism of action as an inhibitor of bacterial protein synthesis has been well-established, it is less clear how azithromycin ameliorates the lung disease associated with Pseudomonas aeruginosa, which is considered to be resistant to the drug. We tested the effects of azithromycin on clinical isolates (CIs) from CF patients and compared them with laboratory reference strains to establish how this drug might interfere with the production of bacterial virulence factors that are relevant to the pathogenesis of airway disease in CF patients. Azithromycin inhibited P aeruginosa PAO1 protein synthesis by 80%, inhibiting bacterial growth and the expression of immunostimulatory exoproducts such as pyocyanin, as well as the gene products necessary for biofilm formation. In contrast, the effects of azithromycin on CIs of P aeruginosa were much more variable, due in large part to their slow growth and limited exoproduct expression. Culture supernatants for two of three clinical strains induced appreciable CXCL8 expression from cultured epithelial cells. Azithromycin treatment of the organisms inhibited 65 to 70% of this induction; azithromycin had no direct effect on the ability of either normal cells or CF epithelial cells to produce CXCL8. Azithromycin does decrease the P aeruginosa synthesis of immunostimulatory exoproducts and is likely to be most effective against planktonic, actively growing bacteria. This effect is less predictable against CIs than the prototypic strain PAO1.

Macrolides and airway inflammation in children

For more than 20 years macrolide antibiotics have been used to treat chronic inflammatory airway diseases based on their immunomodulatory activity. Macrolide antibiotics down-regulate damaging prolonged inflammation as well as increase mucus clearance, decrease bacterial virulence and prevent biofilm formation. Initially shown to decrease morbidity and mortality in diffuse panbronchiolitis and in steroid-dependent asthma, long-term macrolide therapy has now been shown to significantly reduce exacerbations and improve lung function and quality of life in children with cystic fibrosis. They have also proven beneficial in Japanese children and adults with chronic sinobronchitis especially when there is nasal polyposis. Long-term macrolides have also proven clinically beneficial in some patients with plastic bronchitis. Adverse reactions are few and generally self-limited when used at the recommended dosage for immunomodulation.

Antiinflammatory Therapies for Cystic Fibrosis: Past, Present, and Future

Inflammation is a major component of the vicious cycle characterizing cystic fibrosis pulmonary disease. If untreated, this inflammatory process irreversibly damages the airways, leading to bronchiectasis and ultimately respiratory failure. Antiinflammatory drugs for cystic fibrosis lung disease appear to have beneficial effects on disease parameters. These agents include oral corticosteroids and ibuprofen, as well as azithromycin, which, in addition to its antimicrobial effects, also possesses antiinflammatory properties. Inhaled corticosteroids, colchicine, methotrexate, montelukast, pentoxifylline, nutritional supplements, and protease replacement have not had a significant impact on the disease. Therapy with oral corticosteroids, ibuprofen, and fish oil is limited by adverse effects. Azithromycin appears to be safe and effective, and is thus the most promising antiinflammatory therapy available for patients with cystic fibrosis. Pharmacologic therapy with antiinflammatory agents should be started early in the disease course, before extensive irreversible lung damage has occurred.

Multidrug-resistant Pseudomonas aeruginosa in Brooklyn, New York: molecular epidemiology and in vitro activity of polymyxin B

Multidrug-resistant strains of Pseudomonas aeruginosa have become increasingly problematic in certain hospitals. For a 3-month period in 2001, all unique patient isolates were collected from 15 hospitals in Brooklyn, New York, USA. Of 691 isolates, only 70% were susceptible to imipenem and 56% to ciprofloxacin. These susceptibility rates were lower than those found in a prior surveillance study in 1999 (76% and 71% susceptible to imipenem and ciprofloxacin, respectively; p<0.001). The rate of imipenem resistance was associated with fluoroquinolone usage at each hospital (p=0.04). All isolates were susceptible to polymyxin B and 95% to amikacin. Among 195 imipenem-resistant isolates, 47 unique ribotypes were found. However, four ribotypes accounted for >50% of isolates and were shared by most hospitals. Time-kill studies with 13 unique multiresistant strains revealed that polymyxin B was bactericidal against all strains at 4 mg/l, but only against 3 of 13 (23%) strains at 2 mg/l. Using 2 mg/l, significant bacterial regrowth was evident for 5 of 13 (38%) strains. The addition of azithromycin to polymyxin B (2 mg/l) produced a mean decrease of 1 log cfu/ml greater than polymyxin alone and allowed bacterial regrowth in only 2 of 13 (15%) strains. Multiresistant P. aeruginosa is highly endemic to this city, with a few strains having spread among most hospitals. Polymyxin B remains active against all isolates and produces concentration-dependent killing in vitro. Azithromycin appears to enhance the in vitro activity of polymyxin B. The clinical utility of this combination remains to be established.

Long-term azitromycin treatment of cystic fibrosis patients with chronic Pseudomonas aeruginosa infection; an observational cohort study

BACKGROUND

In cystic fibrosis (CF), chronic endobronchial infection with Pseudomonas aeruginosa is a serious complication. Macrolides can increase lung function and weight in patients, and reduce exacerbations.

METHODS

In 2001, we introduced long-term, low-dose azithromycin (AZ) treatment as an integral part of our routine treatment of these patients. Our study is an observational cohort study of all CF patients with chronic P. aeruginosa infection in our CF center comparing clinical parameters of the patients 12 months prior to treatment with the same values during 12 months of treatment.

RESULTS

45 patients (27 men, median age 29 years) completed 1-year treatment. Median weight increased from 63.1 kg in the pre-treatment period to 63.9 kg during treatment (p=0.01). Median slope of decline in lung function increased from pre-treatment FEV1 -4.1% and FVC -3.0% to +0.8% (p<0.001) and +1.6% (p=0.01), respectively. 90% of sputum samples contained mucoid P. aeruginosa before treatment, decreasing to 81% during treatment (p=0.003). Median CRP decreased from 6.2 mmol/l to 5.8 mmol/l (ns).

CONCLUSION

Long-term, low-dose AZ treatment in adult CF patients with chronic P. aeruginosa infection is safe and reduces the decline in lung function, increases weight, and reduces the percentage of mucoid strains of P. aeruginosa in sputum samples.

Effect of macrolides on in vivo ion transport across cystic fibrosis nasal epithelium

Fourteen- and 15-member macrolide antibiotics are under investigation as potential therapeutic agents for cystic fibrosis (CF). The nonantibiotic mechanisms of action of these compounds in CF are not understood. We used nasal potential difference (NPD) measurements to test the effect of macrolides on airway epithelial ion (chloride, sodium) transport of CF mice and humans. We tested clarithromycin and azithromycin in mice, and clarithromycin in patients with CF. Baseline and post-treatment NPD was measured in two strains (C57Bl6 and BalbC) of CF transmembrane regulator "knockout" and littermate control mice, and in DeltaF508/DeltaF508 mice. In addition, NPD was measured in 18 human subjects with CF (17 DeltaF-508/DeltaF-508 and 1 DeltaF-508/other) who were undergoing a 12-month, randomized, double-blind crossover study of the effects of clarithromycin on pulmonary outcome in CF. Neither clarithromycin nor azithromycin affected ion transport characteristics of normal or CF nasal epithelium in either mouse or humans. We conclude that the apparent beneficial effects of macrolides on pulmonary outcome in CF are not mediated by their modulation of ion transport.

Use of Macrolides and Tetracyclines for Chronic Inflammatory Diseases

OBJECTIVE:

To review the efficacy of macrolides and tetracyclines in several chronic inflammatory conditions.

DATA SOURCES:

Searches of MEDLINE (1966–March 2004) and an extensive bibliography search were undertaken. Key terms included acne, blepharitis, cardiovascular disease, cystic fibrosis, periodontitis, rosacea, and rheumatoid arthritis.

STUDY SELECTION AND DATA EXTRACTION:

Data were obtained primarily from randomized placebo-controlled trials upon which key recommendations are based.

DATA SYNTHESIS:

Antibiotics are often prescribed for months or even years for treatment of chronic inflammatory conditions such as acne, blepharitis, cardiovascular disease, cystic fibrosis, periodontitis, rosacea, and rheumatoid arthritis. Randomized controlled trials have shown that azithromycin is useful in the management of cystic fibrosis and the tetracyclines are beneficial in the management of rheumatoid arthritis, acne, blepharitis, and periodontitis. Several large, randomized controlled trials have failed to show any benefit of macrolides in the secondary prevention of cardiovascular disease. No randomized placebo-controlled clinical trials have been performed to assess the efficacy of macrolides or tetracyclines in patients with rosacea.

CONCLUSIONS:

The use of tetracyclines and macrolides for rosacea is based primarily on anecdotal reports or open-label trials. Limited clinical trials support the use of tetracyclines or macrolides in acne, blepharitis, periodontitis, rheumatoid arthritis, and cystic fibrosis. Trials to date do not support the use of antibiotics for secondary prevention of cardiovascular disease.

Quantitative determination of azithromycin in plasma, blood and isolated neutrophils by liquid chromatography using pre-column derivatization with 9-fluorenylmethyloxycarbonyl-chloride and fluorescence detection

In this study, a high-performance liquid chromatographic method with pre-column derivatization and fluorescence detection was optimised and validated for the quantification of azithromycin (AZM) in plasma. Clarithromycin (CLM) was used as an internal standard. Pre-column derivatization was done with 9-fluorenylmethyloxycarbonyl-chloride. Recovery from blood and polymorphonuclear neutrophils (PMNNs) isolated by a gravity separation procedure was also assessed. Analytical separation was carried out using a C18 column as stationary phase and acetonitril-phosphatebuffer as mobile phase. Peak quantification was carried out by excitation at 26 7 nm and detection at 317 nm. A lower limit of quantitation of 0.042+/-0.017 mg/l in plasma, 0.119+/-0.065 mg/l in blood and 0.072+/-0.036 in water was achieved. Linearity was assessed from 0 to 1.5mg/l in plasma and blood and from 0-9 mg/l in water. The analytical method proved to be applicable in a pharmacokinetic study of AZM in a Cystic Fibrosis patient.

Anti-inflammatory effects of macrolides—an underappreciated benefit in the treatment of community-acquired respiratory tract infections and chronic inflammatory pulmonary conditions?

BACKGROUND

It has been recognized for more than 20 years that the macrolides have immunomodulatory effects that are beneficial for those suffering from chronic pulmonary inflammatory syndromes, such as diffuse panbronchiolitis, cystic fibrosis, asthma and bronchiectasis. The macrolides have consistently been associated with decreased length of stay and mortality when used alone or in combination with beta-lactam antibiotics. This effect can be demonstrated against combinations consisting of beta-lactams and other antibiotics active against 'atypical chest pathogens' when treating community-acquired pneumonia (CAP) in hospitalized patients. As such, it appears that the macrolides' effects in CAP patients are more than just antibacterial in nature. AIMS OF THIS REVIEW: This review aims: to give the reader information on the background areas described, as well as related areas; to review the CAP benefits with macrolides and how they may be related to the immunomodulatory properties they demonstrate, albeit in a shorter period of time than previously demonstrated with chronic pulmonary disorders; to use ex vivo data to support these extrapolations.

LITERATURE SEARCH

A literature search using Medline was conducted from 1966 onwards, searching for articles with relevant key words such as macrolide, diffuse panbronchiolitis, community-acquired pneumonia, biofilm, immunomodulation, cystic fibrosis, erythromycin, clarithromycin, roxithromycin and azithromycin, bronchiectasis and asthma. When appropriate, additional references were found from the bibliographies of identified papers of interest. Any relevant scientific conference proceedings or medical texts were checked when necessary.

CONCLUSIONS

(1) Research into macrolide immunomodulation for chronic pulmonary disorders demonstrates consistent positive effects, although of types other than seen with diffuse panbronchiolitis. These effects, together with their inhibitory activity on biofilms, have the potential to make them a useful option. (2) The benefits for CAP are consistent, and higher when a macrolide is given with another atypical agent than if the other atypical agent is given alone, suggesting a non-antibacterial benefit. (3) Recent research of the immunomodulatory properties of azithromycin imply that azithromycin may have a previously unknown short-term biphasic effect on inflammation modulation: enhancement of host defence mechanisms shortly after initial administration followed by curtailment of local infection/inflammation in the following period. (4) Additional in vivo research is needed prior to developing any firm conclusions.