Summary
Antibiotics are commonly used in the management of respiratory disorders such as cystic fibrosis (CF), non-CF bronchiectasis, asthma and COPD. In those conditions long-term antibiotics can be delivered as nebulised aerosols or administered orally. In CF, nebulised colomycin or tobramycin improve lung function, reduce number of exacerbations and improve quality of life (QoL). Oral antibiotics, such as macrolides, have acquired wide use not only as anti-microbial agents but also due to their anti-inflammatory and pro-kinetic properties. In CF, macrolides such as azithromycin have been shown to improve the lung function and reduce frequency of infective exacerbations. Similarly macrolides have been shown to have some benefits in COPD including reduction in a number of exacerbations. In asthma, macrolides have been reported to improve some subjective parameters, bronchial hyperresponsiveness and airway inflammation; however have no benefits on lung function or overall asthma control. Macrolides have also been used with beneficial effects in less common disorders such as diffuse panbronchiolitis or post-transplant bronchiolitis obliterans syndrome. In this review we describe our current knowledge the use of long-term antibiotics in conditions such as CF, non-CF bronchiectasis, asthma and COPD together with up-to-date clinical and scientific evidence to support our understanding of the use of antibiotics in those conditions.
Keywords
Introduction
Respiratory diseases are commonly associated with significant morbidity and mortality, affecting patients' quality of life (QoL) and leading to associated increased costs to the health services. Therefore therapeutic anti-bacterial and anti-inflammatory modalities that may reduce the frequency of exacerbations, the need for hospitalisation and resulting improvement in patients QOL may have important health economic implications. In recent years there has been an improvement in our understanding of managing respiratory conditions using anti-bacterial and/or anti-inflammatory agents. Control of infective exacerbations and thereby the inflammation with oral or aerosol preparations of antibiotics has been shown to have beneficial effects in many of respiratory disorders. This review aims to examine the studies on long-term antibiotic use in management of respiratory diseases, to identify evidence supporting their role and to discuss their potential clinical benefits and limitations.
Role for macrolides
Macrolide antibiotics belong to an expansive family of compounds that are characterized by the presence of a macrocyclic lactone ring.
1
They exert their effects by binding to 50 s ribosomal RNA and have a broad spectrum of activity against many organisms.2
The immunomodulatory properties of macrolides is related to the lactone ring which is seen with the 14 (erythromycin, clarithromycin and roxithromycin) and the 15 (azithromycin) member macrolides.3
Though the precise mechanism of action of macrolides is unknown it has been proposed that macrolides can: attenuate mucous hypersecretion; reduce production of pro-inflammatory cytokines which can lead to a reduction in accumulation and proliferation of neutrophils in the mucosal epithelium; and a suppressive effect on lymphocytic activity.4
In human and animal models macrolides suppress the production of cytokines such as interleukin (IL)-5, IL-8, IL-6, IL-1β, IL-10, tumour necrosis factor (TNF)-α and granulocyte-monocyte colony stimulating factor (GM-CSF); inhibit neutrophil adhesion to epithelial cells; the respiratory burst of neutrophils; and the mucous secretion from airways.5
, 6
, 7
, 8
, 9
Macrolides also inhibit RNA-dependent protein synthesis and binding to the bacterial ribosomal subunits. Moreover, macrolides attenuate lipopolysaccharide-induced MUC5AC gene expression and clarithromycin in particular significantly reduces the MUC5AC expression at both the mRNA and protein levels.- Fonseca-Aten M.
- Okada P.J.
- Bowlware K.L.
- Chavez-Bueno S.
- Mejias A.
- Rios A.M.
- et al.
Effect of clarithromycin on cytokines and chemokines in children with an acute exacerbation of recurrent wheezing: a double-blind, randomized, placebo-controlled trial.
Ann Allergy Asthma Immunol. 2006 Oct; 97: 457-463
10
It has also been reported that in COPD patients, macrolides improve macrophage phagocytosis of apoptotic airways epithelial cells, reduce systemic inflammation and induced increased expression of macrophage mannose receptors.11
, 12
Hence the dual action of enhanced clearance of apoptotic cells and bacteria may diminish the secondary necrosis and production of inflammatory mediators.In patients infected with Pseudomonas (P.) aeruginosa macrolides have effects on biofilm development. Biofilm formation and virulence factors in P. aeruginosa are controlled by a system of bacterial intercommunication, known as quorum sensing. This system comprises genes encoding transcriptional activators, namely lasR and rhlR and macrolides inhibit the transcription of several of these genes.
13
, 14
Macrolides can affect bacterial adherence of pathogens like P. aeruginosa15
and consequently there has been an increasing interest in the use of macrolides in patients colonised with pseudomonas. Macrolides have also been proposed to have pro-kinetic activity on the gastrointestinal tract hence reducing gastro-oesophageal reflux and micro-aspiration which are common phenomena in pulmonary conditions.16
, 17
, 18
Additionally, macrolides have been reported to have anti-proliferative actions and slow both bronchial epithelial cell proliferation and fibroblast migration.19
, 20
Despite the numerous positive outcomes macrolides possess, more recently, there have been reports in murine models
21
and CF patients22
, 23
that long-term macrolides may be associated with the development of non-tuberculous mycobactria (NTM) infections by blocking the autophagosomal clearance of human macrophages by preventing lysosomal acidification, hence impairing autophagic and phagosomal degradation. Hence macrolide therapy may predispose NTM infections by hampering intracellular mycobacterial killing in macrophages.Role for nebulised antibiotics
Antibiotics delivered directly to the airways by nebulisation have been shown to be very effective in managing pulmonary complications of cystic fibrosis (CF).
24
The benefits of inhaled antibiotics are related to the local delivery of the drug to the lung resulting in much higher sputum concentrations compared with that of intravenous or oral agents. In addition, nebulised antibiotics seem to have a lower side effect profile and toxicity. In the context of inhaled antibiotics therapies, it is important to highlight, the role of the inhalation devices as they determine optimal particle size and the lung deposition of the medication.25
, 26
Besides the anti-microbial features of antibiotics, their bioavailability as well as the profile of the adverse effects should also be taken into account. A potential problem associated with the long-term use of nebulised antibiotics is related to patients' adequate adherence with their medications.27
Despite some limitations, inhaled antibiotics have been shown to be beneficial in CF patients, especially those with chronic colonisation with P. aeruginosa.Asthma
There is a reasonable body of evidence indicating attenuation of corticosteroid requirements with the use of macrolides in stable corticosteroid-dependent asthma patients. It has been proposed that the anti-inflammatory mechanism of macrolides is due to the inhibition of the cytochrome P450 system (CYP3A4).
28
Erythromycin, clarithromycin and troleandomycin have been reported to reduce methylpredinsolone clearance in asthmatics29
, 30
, 31
, 32
besides independently manifesting anti-inflammatory activity to those of corticosteroids and theophyllines. Roxithromycin and azithromycin do not inhibit the cytochrome P450 system, but still are effective in reducing bronchial hyperresponsiveness (BHR).33
, 34
Moreover macrolides by inhibiting IL-6 and IL-8 may possibly lead to improvements in FEV1 in asthmatics.35
, 36
Several case series' and open-labelled studies using macrolides have been conducted in asthmatic patients with positive outcomes.6
, 29
, 30
, 32
, 33
, 34
, 37
, 38
, 39
In 2005, a Cochrane review assessed the use of macrolides in asthma.6
Seven studies with a total of 416 asthma patients were considered based on an inclusion criteria of (summarised in Table 1): the studies being double-blind placebo-controlled (DBPC); ≥4 weeks of treatment in patients with varying severity of asthma (clarithromycin – 3 studies, roxithromycin – 2 studies; troleandomycin – 2 studies); evaluation of asthma symptoms and at least one measure of lung function (FEV1, FVC and/or PEF).40
, 41
, 42
, 43
, 44
, 45
, 46
There were no significant differences in forced expiratory volume in 1 s (FEV1), and difference between forced vital capacity (FVC) and corticosteroid usage in the studies. However, significant improvements in favour of macrolides in symptom control, BHR, attenuation in eosinophilic inflammation and good drug tolerability. Despite the positive outcomes, caution in the interpretation is vital as the studies include small numbers, different macrolides assessed, a variety in severities of asthma and chronic infection with Chlamydia (C.) pneumonia, as well as diverse range outcome measures.Table 1Summary of the studies of macrolides in asthma (Modified from Richeldi et al.
6
).| Study (Reference) | Study design | Number of subjects | Duration of study | Antibiotic | Outcomes |
|---|---|---|---|---|---|
| Amayasu et al. 40 | Randomised DBPC Crossover study | 17 adult subjects with mild-to-moderate atopic asthma | 8 weeks | CRM |
|
| Black et al. 41 | Randomised DBPC | 219 asthmatic subjects with serological evidence of C. pneumoniae infection as demonstrated by IgG and IgA antibody titres | 6 weeks | RXM |
|
| Kamada et al. 42 | Randomised DBPC Gp A: TDM + MP; Gp B: TDM + prednisolone; Gp C: placebo + MP | 19 children (6–17 yrs) with OCS-dependent asthma (OCS tapering study) | 12 weeks | TDM |
|
| Kostadima et al. 43 | Randomised DBPC of Gp A: CRM b.i.d.; Gp B: CRM t.i.d.; Gp C: placebo | 75 adult subjects with mild persistent asthma | 8 weeks | CRM |
|
| Kraft et al. 44 | Randomised DBPC | 55 adult subjects with moderate persistent asthma (31 with evidence of C. pneumoniae or M. pneumoniae infection) | 6 weeks | CRM |
|
| Nelson et al. 45 | Randomised DBPC of TDM + MP vs. placebo + MP | 75 adult asthmatic subjects with severe persistent asthma (OCS tapering study) | 52 weeks (single blind for 52 weeks for 57 subjects [TDM n = 30; Placebo n = 27] | TDM |
|
| Shoji et al. 46 | Randomised DBPC Crossover study | 14 adult subjects with aspirin-intolerant mild/moderate asthma | 8 weeks | RXM |
|
Abbreviations: DBPC – Double-blind, placebo-controlled study; CRM – Clarithromycin; PC20 – Provocation concentration causing a 20% reduction in FEV1; Gp – Group; FEV1 – Forced expiratory volume in 1 s; FVC – Forced vital capacity; ECP – Eosinophilic cationic protein; RXM – Roxithromycin; C. pneumomiae – Chlamydia pneumoniae; Ig – Immunoglobulin; flow; PEF – Peak expiratory flow; AQLQ – Asthma-related quality of life; TDM – Troleandomycin; MP – Methylprednisolone; yrs – years; OCS – Oral corticosteroids; FEF25–75 – Forced expiratory flow 25%–75%; b.i.d – Twice daily; t.i.d. – thrice daily; PD20 – Provocation dose causing a 20% reduction in FEV1; M. pneumoniae – Mycoplasma pneumoniae; IL – Interleukin; TNF-α – Tumour necrosis factor alpha; PCR – Polymerase chain reaction; +ve – Positive; –ve – Negative; vs. – versus.
Following this review, a number of new studies have been published in the literature using clarithromycin and azithromycin. A trial on patients with severe refractory asthma
47
reported significant improvements in the clarithromycin-treated group compared to placebo in Juniper's Asthma-related Quality of Life Questionnaire (AQLQ) scores,48
and reduction in sputum IL-8 and neutrophils, and self-reported wheezing; particularly in the subgroup of patients with non-eosinophilic (sputum) asthma but there was no improvements in FEV1, hypertonic saline challenge or sputum eosinophil counts. Piacentini et al. conducted an 8 week trial on the efficacy of azithromycin versus placebo on lung function, BHR and airway inflammation in 16 asthmatic children49
and reported significant reduction in hypertonic saline-induced BHR and sputum neutrophilia in favour of the azithromycin-treated children compared to placebo, but no changes in FEV1 between both groups. In another randomised placebo-controlled, blinded, allocation-concealed parallel group clinical trial in 45 adults with stable, persistent asthma, it was observed that there were significant improvements in azithromycin-treated (compared to placebo) subjects in asthma symptoms and rescue inhaler use during treatment that persisted at 3 months after treatment, but not in the AQLQ.50
Of note, in the azithromycin-treated subjects the overall asthma symptom improvement was higher in the subgroup of patients with high immunoglobin (Ig) A to Chlamydia pnuemoniae than in the lower IgA (28% vs. 12%), but not significant. Moreover, there was a positive and significant association between anti-Chlamydial IgA, but not anti-Chlamydial IgG, with asthma symptom changes at 6 months. Hence, it was proposed that the anti-Chlamydial IgA could help with 6-month asthma prognosis, as measured by an overall asthma symptom scale. From the various studies, we can see that there may be a possible role for macrolides in chronic asthma; however their routine use is not clearly justified based on current evidence.Chronic Obstructive Pulmonary Disease (COPD)
Exacerbations of Chronic Obstructive Pulmonary Disease (COPD) impair health status, accelerate the progression of the disease and are associated with significant early mortality.
51
The frequency and severity of exacerbations is associated with long-term mortality independent of co-morbidities, FEV1, age and body mass index (BMI).52
Airway inflammation plays a key role in the pathogenesis of COPD and a variety of microbial organisms promote the inflammatory process precipitating an acute exacerbation. Given the role of inflammation and infections in COPD the use of long-term antibiotics may offer a distinctive benefit to control this disease.53
One of the earliest studies by Gomez and colleagues observed a statistically significant reduction in the number of acute infectious episodes and hospital admissions in azithromycin-treated versus placebo following a 3-day prophylactic treatment course every 21 days during the winter months.
54
The important trials are summarised in Table 2.- Gomez J.
- Banos V.
- Simarro E.
- Lorenzo Cruz M.
- Ruiz Gomez J.
- Latour J.
- et al.
Prospective, comparative study (1994–1998) of the influence of short-term prophylactic treatment with azithromycin on patients with advanced COPD.
Revista espanola de quimioterapia: publicacion oficial de la Sociedad Espanola de Quimioterapia. 2000 Dec; 13 ([Clinical Trial Comparative Study Randomized Controlled Trial]): 379-383
55
, 56
, 57
, 58
, 59
, - Seemungal T.A.
- Wilkinson T.M.
- Hurst J.R.
- Perera W.R.
- Sapsford R.J.
- Wedzicha J.A.
Long-term erythromycin therapy is associated with decreased chronic obstructive pulmonary disease exacerbations.
Am J Respir Crit Care Med. 2008 Dec 1; 178 ([Randomized Controlled Trial Research Support, Non-U.S. Gov't]): 1139-1147
60
The first prospective study investigating the efficacy of long-term macrolide therapy in patients with stable COPD was an open-label, randomized trial of erythromycin (200–400 mg/d) for 12 months in 109 patients with COPD. Thirty patients (56%) compared to six patients (11%) in the control group and erythromycin group respectively had one or more exacerbations. Although this trial was noteworthy, it was unblinded. However, not all the initial trials were supportive of a role for long-term antibiotics. Banerjee et al. examined the role of 3-months oral clarithromycin or placebo once-daily in 67 patients with moderate-to-severe COPD. The authors concluded that treatment of stable COPD with clarithromycin yielded no clinical advantage and did not improve health status, sputum bacterial numbers, or prevent infective exacerbations.56
However, the short duration (3 months) of the antibiotic could have had a bearing on the results. Seemungal and colleagues in a randomized, DPBC study of 109 patients administered erythromycin 250 mg twice daily to patients with moderate COPD (80% of patients on inhaled corticosteroids) over 12 months.59
They found that erythromycin treatment was associated with a significant reduction in exacerbations compared with placebo, but had no significant impact on FEV1, sputum inflammatory markers, serum inflammatory markers or bacterial flora. The frequency of side effects was low in both arms with no differences between the two arms.- Seemungal T.A.
- Wilkinson T.M.
- Hurst J.R.
- Perera W.R.
- Sapsford R.J.
- Wedzicha J.A.
Long-term erythromycin therapy is associated with decreased chronic obstructive pulmonary disease exacerbations.
Am J Respir Crit Care Med. 2008 Dec 1; 178 ([Randomized Controlled Trial Research Support, Non-U.S. Gov't]): 1139-1147
Table 2Summary of the studies of long term antibiotics in COPD.
| Study | Study design | Number of subjects | Duration of study | Antibiotic | Outcomes |
|---|---|---|---|---|---|
| Albert et al. 55 | Randomised placebo control study | 1577 | 12 months | Azithromycin250 mg daily |
|
| He et al. 58 | Randomised DPBC trial | 36 | 6 months | Erythromycin125 mg three times daily |
|
| Blasi et al. 57 | Randomised uncontrolled trial | 22 | 6 months | Azithromycin 500 mg three times a week |
|
| Seemungal et al. 59
Long-term erythromycin therapy is associated with decreased chronic obstructive pulmonary disease exacerbations. Am J Respir Crit Care Med. 2008 Dec 1; 178 ([Randomized Controlled Trial Research Support, Non-U.S. Gov't]): 1139-1147 | Randomised DPBC trial | 109 | 12 months | Erythromycin250 mg twice daily |
|
| Banerjee et al. 56 | Prospective Randomised DPBC trial | 67 | 3 months | Clarithromycin 500 mg once daily |
|
| Sethi et al. 60 | Randomised DPBC trial | 1157 | 48 months | 6 courses of Moxifloxacin 400 mg OD for 5 days |
|
The results of the above studies suggest that macrolide therapy may be beneficial in COPD patients preventing acute exacerbations of COPD (AECOPD) and altering the natural course of the disease. Whether this is due to its anti-microbial properties or due to immunomodulation needs to be established. The balance between inflammation and immunomodulation is important in chronic airway diseases and macrolides may have a possible effect on this balance in addition to its anti-microbial effects to reduce AECOPD. That said, a randomised DBPC trial in stable COPD patients with pulsed moxifloxacin (moxifloxacin 400 mg/day) (N = 573) or placebo (N = 584) once daily for 5 days and treatment repeated every 8 weeks for a total of 6 courses found that at 48 weeks the odds ratio (OR) for suffering an exacerbation was reduced by 20% in the intention-to-treat group.
60
No changes in the overall health status, rates of hospitalization or mortality, or attenuation of lung function decline were noted. Subgroup analyses demonstrated that the reduction in exacerbations with moxifloxacin was seen in COPD of all severity categories, supporting a role for quinolones in preventing exacerbations.Recently, Albert and colleagues conducted a multicenter randomised trial of 1142 patients at risk of AECOPD to receive 250 mg daily of azithromycin (n = 570) or placebo (n = 572) for a year in addition to usual care.
55
The primary outcome i.e. time to first exacerbation was significantly increased in the azithromycin group when compared to placebo (226 days vs. 174 days). The hazard ratio for having an acute exacerbation per patient year was 0.74 in the azithromycin group. Although there was no significant reduction in the hospitalisation rates, urgent care visits or mortality between the two groups, azithromycin treatment improved the QoL measures and had similar frequency of serious adverse events in both groups except for hearing loss and colonisation with macrolide-resistant organisms. While there was a question on the role of long-term antibiotics in stable COPD to prevent exacerbations, the trial by Albert et al. has provided support for the long-term use of azithromycin to reduce exacerbations. It is still unclear whether this beneficial effect is due to the anti-bacterial properties or to the immunomodulatory effects of macrolides. Furthermore, the likely development of resistance to antibiotics in the long-run and the role for azithromycin on a once, twice or thrice weekly regimen, given the extremely long tissue persistence of the drug needs to be explored. Therefore, adverse effects of macrolides such as hearing loss, effects on QTc and interactions with other agents need to be taken into account and balanced against possible benefits in individual patients. In addition, patients need ongoing assessments for potential benefits of long term therapy with macrolides and at the same time be aware of potential adverse effects. Although, there have been no studies or guidelines recommended how long one should administer macrolides to assess the efficacy of macrolides, we suggest a trial of 3–6 months in the first instance, followed by regular reviews on benefit vs adverse events.Cystic fibrosis (CF)
CF is one of the most common genetic disorders
61
, 62
, 63
in which the main defect relates to the malfunction in the CF trans-membrane conductance regulator (CFTR). This defect in turn results in chronic respiratory infections which remain the main cause of morbidity and mortality in CF.64
, 65
, 66
, 67
In early CF, Staphylococcus (S.) aureus and Haemophilus (H.) influenzae remain the main pathogens.24
, 61
However, overall the most commonly isolated pathogen in CF is P aeruginosa. Recently, pathogens such as Burkholderia (B.) cepacia and Stenotrophomonas (S.) maltophilia have been reported in CF with increasing frequency.24
, 61
Antibiotics in CF are used to manage exacerbations as well as to prevent, eradicate and control respiratory infections, hence potentially improving survival.
24
Flucloxacillin, which has shown to reduce the incidence of infection with S. aureus, has acquired long term use in young children with CF aged up to 3 years.68
Similarly, other oral agents in particular macrolides have been shown to be beneficial in CF (Table 3).69
, 70
, 71
, 72
, 73
, 74
, 75
, 76
, 77
A number of studies have shown that the long-term use of azithromycin in CF patients resulted in improved lung function, reduction in a number of infective exacerbations and the use of antibiotics.69
, 70
, 71
, 72
, 73
, 74
, 75
, 76
, 77
, 78
, 79
For example, Wolter et al. reported that in adults with CF, azithromycin improved QoL, reduced both the number of respiratory exacerbations, and the rate of decline in the lung function.70
Similar outcomes were reported by Saiman and colleagues with oral azithromycin in CF patients chronically infected with P. aeruginosa.71
Although the exact mode of action of macrolides in CF is not fully understood, the benefits are mainly observed in patients colonised with P. aeruginosa. However, some also reported the benefit of long-term macrolides in CF patients even prior to P. aeruginosa infection.73
Chronic colonisation with P. aeruginosa is one of the main predictors of morbidity and mortality in CF,80
hence the need to control this infection.Table 3Summary of the studies of long term antibiotics in cystic fibrosis.
| Study | Study design | Number of subjects | Duration of study | Antibiotic used | Outcomes |
|---|---|---|---|---|---|
| Saiman et al. 71 | Randomised Placebo controlled | 185(87 treatment group) | 6 months | Azithromycin | Improved FEV1, reduced number of exacerbations, |
| Wolter et al. 70 | Randomised placebo controlled | 60 adult CF patients | 3 months | Azithromycin | No decline in FEV1, fewer courses of IV antibiotics, decline in C reactive protein, improvement in QOL |
| Kabra et al. 78 | Randomised controlled | 56 children | 12 months | Azithromycin low dose 5 mg/kg/day compared with high dose 15 mg/kg/day | No difference in clinical score, FEV1 and pulmonary exacerbation rates between the two groups |
| Hodson et al. 83 | Randomised controlled | 115 | 4 weeks | Nebulised colomycin compared with nebulised tobramycin | Both treatments reduced bacterial load. Nebulised tobramycin improved lung function in CF patients chronically colonised with P. aeruginosa |
| Ramsey et al. 84 | Randomised placebo controlled | 520 | 24 weeks | Nebulised tobramycin | Improvement in pulmonary function, decrease in the density of P. aeruginosa in sputum, decreased risk of hospitalization |
| McCoy et al. 93 | Randomised controlled | 211 | 28 days | Inhaled aztreonam solution | Improvement in pulmonary function and respiratory symptoms |
| Retsch-Bogart et al. 94 | Randomised placebo controlled | 164 | 28 days | Inhaled aztreonam solution | Improvement in pulmonary function and respiratory symptoms |
| Oermann et al. 95 | Open label | 274 | 18 moths | Inhaled aztreonam solution | Clinical benefits in pulmonary function, health-related quality of life, and weight |
| Ledson et al. 88 | Randomised double blinded cross over | 20 | 4 weeks | Inhaled taurolidine | No change in B. cepacia colony count or spirometry, nor symptom score |
| Frederiksen et al. 81 | Comparison with historical control | 48 patients compared with 43 control | 44 moths | Inhalation of colistin and oral ciprofloxacin | 16% of the treated patients developed chronic P. aeruginosa infection compared with 72% of the control patients (P < 0.005), improvement in lung function |
| Gibson et al. 89 | Randomised double blind | 21 | 28 days | Inhaled tobramycin | Reduction in P. aeruginosa density |
| Geller et al. 96 | Randomised placebo controlled | 151 | 28 days | Inhaled ciprofloxacin | Reduction in P. aeruginosa density, improvement in pulmonary function (FEV1), reduction in need for anti-pseudomonal antibiotics |
Numerous antibiotics have been tested for aerosolized use in CF, including tobramycin, colomycin, gentamicin, aztreonam and taurolidine and some of them have acquired clinical use in CF.
81
, 82
, 83
, 84
, 85
, 86
, 87
, 88
Nebulised antibiotics in CF have been used to manage acute respiratory exacerbations as well as chronic therapy to stabilise lung function and prevent chronic colonisation with P. aeruginosa. For example, studies have shown that treatment with nebulised colomycin can lead to effective eradication of colonisation of P. aeruginosa.81
, 82
In fact, three months thrice daily regime of nebulised colistin showed that after 3.5 years only 16% of treated patients had developed chronic P. aeruginosa infection compared to 72% of untreated historical controls.81
Similarly, studies revealed that in CF patients inhaled tobramycin resulted in effective eradication of early infection with P. aeruginosa.89
Moreover, long-term intermittent administration of inhaled tobramycin has been well tolerated and resulted in improved lung function and decreased density of P. aeruginosa in the sputum as well as reducing the risk of hospitalization.84
, 90
Similar observations have been reported with nebulised tobramycin and colomycin in CF patients colonised with P. aeruginosa by others83
; hence both of these agents are being regularly used in clinical practice. A recent Cochrane review on long term inhaled antibiotics in CF has concluded that inhaled antibiotic treatment probably improves lung function and reduces exacerbation rate, but a pooled estimate of the level of benefit was not possible. The best evidence was for inhaled tobramycin.91
Amongst the new inhalation antibiotics approved for the use in CF patients with P. aeruginosa colonisation is a monobactam formulation, aztreonam lysinate.
87
, 92
The use of inhaled aztreonam in CF patients with P. aeruginosa colonisation resulted in reduction of bacterial burden, preservation of lung function, and improvement in symptoms associated with disease.93
, 94
, 95
McCoy and colleagues observed that 28-days of nebulised aztreonam compared with the placebo in CF patients on nebulised tobramycin improved lung function, respiratory symptoms and reduced sputum density of P. aeruginosa.93
Similar observations were noted in an 18-month study with nebulised aztreonam besides being well tolerated.95
Another novel inhaled antibiotic tested in CF patients with chronic P. aeruginosa includes an aerosol formulation of levofloxacin (MP-376, Aeroquin).96
This new preparation of inhaled levofloxacin resulted in improved lung function and reduction in antibiotics use. Geller et al. observed that in CF patients colonised with P. aeruginosa nebulised levofloxacin was well tolerated, improved FEV1 by 8.7% and reduced sputum P. aeruginosa density.96
There have also been attempts to use nebulised antibiotics to treat CF patients colonised with B. cepacia as those patients have an increased morbidity and mortality. Taurolidine is an antibiotic with a broad spectrum of activity against gram negative and positive bacteria as well as being an anti-endotoxin. Ledson and colleagues assessed the effects of inhaled taurolidine in CF patients infected with B. cepacia.
88
Although Taurolidine was well tolerated it did not affect the B. cepacia colony count or other outcomes assessed. Inhaled formulations of ciprofloxacin have shown promise in patients with non-CF bronchiectasis97
and will be of interest to see whether similar effects will be seen in CF. Overall the use of inhaled antibiotics in CF has been widely accepted. The main role of inhaled antibiotics in CF has been in patients with chronic colonisation with P. aeruginosa, however there are potential new agents currently being assessed which may acquire clinical use in the future.- Bilton D.
- Serisier D.J.
- De Soyza A.T.
- Wolfe R.
- Bruinenberg P.
Multicenter, randomized, double-blind, placebo-controlled study (ORBIT 1) to evaluate the efficacy, safety, and tolerability of once daily ciprofloxacin for inhalation in the management of Pseudomonas aeruginosa infections in patients with non-cystic fibrosis bronchiectasis.
Eur Respir J. 2011; 38: 333S
Non-CF bronchiectasis
Long-term antibiotics in bronchiectasis reduces exacerbations, improves symptoms and QoL by reducing bacterial load and airway inflammation.
98
The early evidence for long-term antibiotics in bronchiectasis stems from the MRC multi-centre study where 122 patients with bronchiectasis were allocated to penicillin (n = 38), oxytetracycline (n = 44) and placebo (n = 40). After a year, in the oxytetracycline group there was a 64% reduction in sputum volume, had fewer days off work; fewer days confined to bed and reduced episodes of fever. Unfortunately, no formal statistical analyses were performed.99
Currie et al. in a randomised placebo controlled trial evaluated the effect of high-dose amoxicillin (3 gm twice daily) in 38 patients with bronchiectasis.100
The frequency of exacerbations during the study treatment phase was similar in both groups, but they were less severe than before study treatment in the amoxicillin group. There was a greater reduction in purulent sputum volume between exacerbations during the study treatment in the amoxicillin group compared to placebo. Independent assessment of the overall response based on patients' diary cards showed that a higher proportion improved in the amoxicillin-treated (11 of 17) compared to placebo (4 of 19). Adverse events experienced by patients were minor and there was no change in the bacterial flora based on sputum and stool cultures. More recently a New Zealand group conducted a DBPC study to evaluate the role of azithromycin in reducing frequency of exacerbations, improvement in lung function and health-related QoL in 141 (71 azithromycin; 70 placebo) patients with non-CF bronchiectasis for 6 months.101
They reported a significant reduction in the rate of exacerbations but no differences in the other parameters assessed.Studies in non-CF bronchiectasis include both oral and nebulised antibiotics and are summarised in Table 4.
100
, 102
, 103
, 104
, 105
, 106
Davies and colleagues in an open-labelled prospective trial evaluated the role of azithromycin 250 mg thrice/wk for 4 months in 39 bronchiectasis patients.102
All the patients had more than 4 documented exacerbations during the previous 12 months. There was a reduction in exacerbations warranting oral and intravenous antibiotics, and an improvement in TLCO. Yalcin and colleagues examined the effects of clarithromycin on inflammatory markers (IL-8, TNF-alpha, IL-10 levels and cell profiles in bronchoalveolar lavage (BAL) fluid, pulmonary function and sputum production in children with non-CF bronchiectasis in a randomised DBPC trial.106
Following 3 months of treatment compared to placebo, the clarithromycin-treated subjects showed a significant decrease in IL-8 levels, total cell count, neutrophil ratios in BAL fluid and daily sputum production, but no significant differences in pulmonary function test parameters. Barker and colleagues examined the microbiological efficacy and safety of nebulised tobramycin twice daily for 4 weeks in 74 patients with bronchiectasis and P. aeruginosa in a randomised DBPC trial (n = 37 in each group).107
At Week-4, the treatment group had a mean decrease in P. aeruginosa density of 4.54 log10 colony-forming units/g sputum (p < 0.01). At Week-6, P. aeruginosawas eradicated in 35% in the treatment group but was detected in all placebo patients. No differences in lung function were reported. This study supported a role for nebulised antibiotics in bronchiectasis, albeit for a 4-week duration.- Barker A.F.
- Couch L.
- Fiel S.B.
- Gotfried M.H.
- Ilowite J.
- Meyer K.C.
- et al.
Tobramycin solution for inhalation reduces sputum Pseudomonas aeruginosa density in bronchiectasis.
Am J Respir Crit Care Med. 2000 Aug; 162 ([Clinical Trial Clinical Trial, Phase II Randomized Controlled Trial Research Support, Non-U.S. Gov't]): 481-485
Table 4Summary of the studies of long term antibiotics in Non-CF bronchiectasis.
| Study | Study design | Number of subjects | Duration of study | Antibiotic | Outcomes |
|---|---|---|---|---|---|
| Murray et al. 104 | Randomised placebo controlled trial | 65 | 12 months | Neb gentamicin 80 mg twice daily |
|
| Orriols et al. 105 | Open labelled study | 17 | 12 months | Neb ceftazidime 1 gm bd & Neb tobramycin 100 mg bd or placebo |
|
| Drobnic et al. 103 | Double blind placebo controlled crossover trial | 30 | 6 months | Nebulised tobramycin 300 mg twice daily |
|
| Yalcin et al. 106 | Randomised placebo controlled | 34 (children) | 3 months | Clarithromycin 15 mg/kg |
|
| Davies et al. 102 | Prospective open labelled | 39 | 10 months | Azithromycin 250 mg three times weekly |
|
| Currie et al. 100 | Randomised placebo controlled | 38 | 32 weeks | Amoxicillin 39 twice daily |
|
In a trial involving 30 bronchiectatic patients with nebulised tobramycin for 6 months with
103
there was a reduction in hospital admissions and in-patient days during treatment phase and a decrease in P. aeruginosa density up to 3 months of stopping tobramycin. However, there was no difference in exacerbations, antibiotic use, lung function or QoL between the treatment periods. Another trial involving nebulised ceftazidime and tobramycin twice daily in patients with bronchiectasis concluded that the treatment group had less admissions and in-patient days, but there was no difference in the lung function or use of oral antibiotics use between groups.105
More recently, a study from Edinburgh randomised sixty-five patients to either twice daily nebulised gentamicin, or 0.9% saline, for 12 months.104
At 12 months the treatment group had reduced sputum bacterial density with 30.8% eradication in those infected with P. aeruginosa and 92.8% eradication in those infected with other pathogens; less sputum purulence; greater exercise capacity and fewer exacerbations with increased time to first exacerbation. No differences were seen in 24-h sputum volume and lung function parameters. Of note, P. aeruginosa isolates developed resistance to gentamicin. Recently, the ORBIT 1 study evaluated the efficacy, safety, and tolerability of once daily inhaled ciprofloxacin in the management of P. aeruginosa infections in patients with non-CF bronchiectasis.97
The data revealed that at 28 days nebulised ciprofloxacin reduced P. aeruginosa density and improved QoL. Murray et al. conducted a 1-year randomised placebo controlled study assessing the efficacy of nebulised gentamicin compared to placebo in a number of sputum, objective, subjective and exacerbations parameters.- Bilton D.
- Serisier D.J.
- De Soyza A.T.
- Wolfe R.
- Bruinenberg P.
Multicenter, randomized, double-blind, placebo-controlled study (ORBIT 1) to evaluate the efficacy, safety, and tolerability of once daily ciprofloxacin for inhalation in the management of Pseudomonas aeruginosa infections in patients with non-cystic fibrosis bronchiectasis.
Eur Respir J. 2011; 38: 333S
104
They reported substantial improvements sputum bacterial density with over 30% having eradicated P. aeruginosa and over 90% eradicating other pathogens, sputum purulence, fewer exacerbations and delay to first exacerbations, improved exercise capacity as well as improvement in subjective parameters of cough and QoL. Moreover there were no P. aeroginosa isolates developing resistance to gentamicin. Of note, there were no improvement sin 24-h sputum volume and various assessments of lung function.There is consistent evidence that long-term antibiotics either oral or nebulised improves QoL, decreases exacerbation frequency and reduces the bacterial load. Unlike the CF experience, there does not seem to be an improvement of pulmonary function after treatment with nebulised antibiotics. In practice, the prescription of long-term antibiotics should be considered for patients exacerbating at least 3 times/yr and in patients with fewer exacerbations but with greater morbidity.
108
There may also be a lower threshold for starting long-term antibiotics in patients with primary or secondary immunodeficiency. Antibiotic choices should be based on sputum microbiology and careful monitoring needs to be in place regarding microbial resistance and adverse events.Diffuse panbronchiolitis (DPB)
DPB is a chronic respiratory condition of unknown aetiology, almost exclusively described in the Far East (mainly Japan, but also Korea and China), characterised by chronic inflammation of the respiratory tract with progressive destruction of the lung parenchyma.
109
, 110
, Up to the early 1980s DPB was a fatal condition, however with the use of long-term macrolides it is now a very treatable condition with its 5-year prognosis increasing from 63% in the 1970s to about 90% in the late 1990s.112
Initially, case reports and series' using low-dose erythromycin112
, 113
reported clinical and radiological improvements in patients with DPB, but recent reports have also reported similar positive findings with clarithromycin, roxithromycin and azithromycin (Table 5).114
, 115
, 116
, 117
A recent Cochrane review reported that, of the many studies assessed only one was identified to have adequate quality.4
In this study of 19 subjects with DPB, 12 were randomly assigned to receive low-dose erythromycin and rest no treatment.118
It was observed that compared to the pre-treatment CT scan, there were marked improvements in the interval CT scan in all subjects following treatment with the erythromycin. Of note, 71.4% of the control group subjects had worsening of their interval scan. This study had a number of methodological errors with no fixed times of treatments, interval scans, and mention of adverse events besides the small cohort of subjects. Despite the lack of large RCTs to confirm the efficacy and safety of macrolides in DPB, the Ministry of Health and Welfare of Japan have implemented the use of macrolides in its treatment on diagnosis for 6-months based on the observational studies and expert opinion.Table 5Summary of the studies of macrolides in diffuse panbronchiolitis.
| Study | Study design | Number of subjects | Duration of study | Antibiotic used | Outcomes |
|---|---|---|---|---|---|
| Akira et al. 118 | Observational RCT of efficacy of macrolide treatment | 19 subjects (12 active treatment and 7 no treatment) | Not specified | Erythromycin |
|
| Kudoh et al. 112 | Retrospective observational survival study based on year of diagnosis | 498 subjects(Gp A: 1970–79 [only std ABx avail} [n = 190]; Gp B: 1980–84 [quinolones avail][n = 221]; Gp C: 1985–90 (Erythromycin avail} [n = 87]) | N/A | Erythromycin |
|
| Yamamoto et al. 134 | Retrospective observational study comparing quinolone vs. macrolide | 101 subjects | N/A | Erythromycin |
|
| Kobayashi et al. 117 | Open-labelled study of efficacy and safety | 60 subjects (efficacy data on 52 and safety data on 55) | 12 weeks | Azithromycin |
|
| Kadota et al. 115 | Prospective open-labelled study | 10 subjects | 4 years | Clarithromycin |
|
Abbreviations: RCT – Randomised control trial; CT scan – Computed tomography scan; Gp – Group; std – standard; ABx – antibiotics; avail – available; n – number; N/A – Not applicable; vs. – versus; CXR – Chest X-ray; PaO2 – Partial pressure of oxygen in arterial blood; ESR – erythrocyte sedimentation rate; FEV1 – Forced expiratory volume in 1 s; CRP – C-reactive protein; FVC – Forced vital capacity.
Post-transplant bronchiolitis obliterans syndrome (BOS)
Obliterative bronchiolitis (OB) is an airway inflammatory process that results in significant long-term morbidity and mortality in post-transplant patients, mainly of the lung, but also of other organs, synonymous with chronic graft rejection.
119
, 120
, 121
Although OB is thought to be mainly immunologically mediated and is rarely successfully managed with the use of immunosuppressive agents, significant numbers of transplant patients experience concurrent bacterial and non-bacterial infections which may worsen lung inflammation and potentially worsen the chronic rejection. Azithromycin has been examined in several small post-lung transplant studies with potential benefits, but this has been questioned. Four prospective open-labelled studies with azithromycin treatment have been described in the literature, 3 have shown significant improvements in FEV1,122
, 123
, 124
but 1 showing no improvement in FEV1.125
Furthermore, 2 retrospective case series' using azithromycin have been conducted, one reporting positive FEV1 improvements beyond 3 months of treatment cessation in a majority of patients,126
but the other did not.127
In the largest prospective study of 14 lung transplant patients receiving azithromycin for 3 months, besides the mean increase in FEV1, it was reported that BAL neutrophils, % neutrophils and IL-8 mRNA ratio decreased significantly but had no impact on IL-17 mRNA ratio.124
They noted a responder group of 6 patients (increase >10% FEV1) who had a marked reduction in %BAL neutrophilia, IL-8 mRNA and IL-17 mRNA. Moreover, they reported a significantly positive correlation between the initial %BAL neutrophilia and response to treatment. Of note, a BAL neutrophilia of >15% had a positive predictive value of 85% for a significant FEV1 response to azithromycin, and that a BAL neutrophilia <15% had a negative predictive value of 100%.124
Similar positive and negative predictive values have been reported by another group.128
The clinical benefits of azithromycin have been hypothesised to be due to: the pro-kinetic effect diminishing the gastro-oesophageal reflux
122
and enzyme inhibition, increasing the plasma concentrations of immunosupressors.123
, 124
, 125
, 126
However, these have not been substantiated. The role of C. pneumoniae infection has been implicated in the development of BOS, with donor-recipient serology mismatch (i.e. donor positive/recipient negative) being an independent risk factor for BOS development.129
Furthermore, it has been reported that C. pneumoniae infection in lung transplant patients is associated with poor outcome and increased risk of BOS.130
From the available data, azithromycin has been associated with positive outcomes; physicians need to be cautious that this therapy is not viewed as a panacea for treatment of BOS, and that larger clinical trial with long-term follow-up are needed to determine the benefits in all and responding patients.Opinions and conclusions
Different macrolides have variable pharmacokinetic and pharmcodynamic properties such as the long half-life of azithromycin and its higher concentration in sputum,
131
, 132
whereas roxithromycin with its higher anti-inflammatory activity,133
compared to other macrolides. It is also not clear as to whether the actual mechanism of action of macrolides is due to the anti-microbial (deep-seated infection clearance), anti-reflux or anti-inflammatory, and in certain cases anti-fibrotic properties. From this it appears that macrolides may manifest their biological efficacy in a range of respiratory conditions through a number of recognised potential mechanisms or others that still yet to be established. To investigate these mechanisms needs substantial effort and collaboration between clinicians and scientists not only in translational studies, but also on the bench. From the available evidence it should be noted that guidelines recommend the use of macrolides in the management of CF (azithromycin in particular) and panbronchiolitis. In the former, the recommendations are based on well designed DBPC studies and meta-analyses and in the latter by consensus opinion (Japanese health authority). In the remaining conditions discussed in this review the data are not so stringently clear and hence there remains a need for well-conducted studies to establish their efficacy. Lastly, it may be that with the aid of these mechanistic and efficacy-based studies in the future, we may be in a better position to determine a disease-specific macrolide, i.e. ‘tailored treatment’ for the individual patients.Aerosolised antibiotics deliver anti-microbial therapy to diseased lungs, hence providing targeted therapy with possibly limited adverse events to patients. Most of the current available data on inhaled antibiotics involve anti-pseudomonal agents which if administered early enough may help with eradication, or in the long-term reduce the risk of recurrent infections especially in CF and non-CF bronchiectasis patients.
In this review we have highlighted the various respiratory conditions in which long-term antibiotics, oral or nebulised, have been investigated. The data is more robust in CF (nebulised antibiotics and oral azithromycin) compared to non-CF bronchiectasis, panbronchiolitis and COPD, and even less so with asthma and BOOP. The CF model can serve as a foundation to investigate the role of long-term antibiotics, especially nebulised in non-CF bronchiectasis. Identification of the precise mechanism of anti-inflammatory effect of macrolides would encourage development of newer molecules with immunomodulatory effects, hence circumventing the anti-bacterial effects. There appears to be a role for long-term antibiotics, especially macrolides, in a number of chronic inflammatory airway disorders, however there is an urgent need to establish this by performing longer, macrolide-specific, DBPC and bench studies to establish their efficacy, safety and mechanisms of action.
Conflict of interest statement
KSB has received honoraria for speaking and financial support to attend meetings from Chiesi, Astra Zeneca, Boehringer, GSK/Allen & Hanburys and Wyeth.JK has no conflict of interest.JBM has received honoraria for speaking and financial support to attend meetings/advisory boards from Wyeth, Chiesi, Pfizer, MSD, Boehringer Ingelheim, Teva, GSK/Allen & Hanburys, Napp, Almirall and Novartis.
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Article Info
Publication History
Published online: March 25, 2013
Accepted:
February 11,
2013
Received:
March 20,
2012
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© 2013 Elsevier Ltd. Published by Elsevier Inc.
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