When and how to treat pulmonary non-tuberculous mycobacterial diseases R
Transcription
When and how to treat pulmonary non-tuberculous mycobacterial diseases R
INVITED REVIEW SERIES: INFECTIOUS DISEASES When and how to treat pulmonary non-tuberculous mycobacterial diseases RACHEL M. THOMSON1,2 AND WING-WAI YEW3 1 QLD TB Control Centre, Specialised Health Services, 2Department of Thoracic Medicine, The Prince Charles Hospital, Brisbane, Queensland, Australia, and 3Tuberculosis and Chest Unit, Grantham Hospital, Hong Kong, China ABSTRACT Non-tuberculous mycobacteria are ubiquitous environmental organisms that have been recognized as a cause of pulmonary infection for over 50 years. Traditionally patients have had underlying risk factors for development of disease; however, the proportion of apparently immunocompetent patients involved appears to be rising. Not all patients culture-positive for mycobacteria will have progressive disease, making the diagnosis difficult, though criteria to aid in this process are available. The two main forms of disease are cavitary disease (usually involving the upper lobes) and fibronodular bronchiectasis (predominantly middle and lingular lobes). For patients with disease, combination antibiotic therapy for 12–24 months is generally required for successful treatment, and this may be accompanied by drug intolerances and sideeffects. Published success rates range from 30% to 82%. As the progression of disease is variable, for some patients, attention to pulmonary hygiene and underlying diseases without immediate antimycobacterial therapy may be more appropriate. Surgery can be a useful adjunct, though is associated with risks. Randomized controlled trials in well-described patients would provide stronger evidence-based data to guide therapy of non-tuberculous mycobacteria lung diseases, and thus are much needed. losis complex and Mycobacterium leprae. They are commonly occurring microbes that have differing geographic distributions worldwide in environmental reservoirs, particularly the soil and various water sources.1 The mode of transmission of NTM to humans has not been fully delineated, although person-to-person transmission is thought not to occur, at least in immunocompetent hosts. EPIDEMIOLOGY OF PULMONARY NTM INFECTIONS Correspondence: Rachel M. Thomson, QLD TB Control Centre, Specialised Health Services, 24-28 Cornwall Street, Annerley, Qld 4103, Australia. Email: [email protected] Received 30 May 2008; invited to revise 2 July 2008; revised 23 July 2008; accepted 4 August 2008 (Associate Editor: Kenneth Tsang). An increase in the prevalence of NTM infection/ disease worldwide has been noted in the past 1–2 decades.2–4 Postulated reasons include (i) a rise in prevalence of HIV infection and other acquired immunocompromised states, (ii) an increased understanding of the clinico-pathological relationship between host and pathogen5 and awareness of these organisms as potential pathogens, (iii) advances in methods of detection and recovery of the organisms, (iv) an aging population (as this is often a disease of the elderly), (v) increased survival of patients with conditions that increase susceptibility—such as cystic fibrosis and COPD, and (vi) increased environmental exposure. Factors driving this increase in exposure include (i) disinfection of drinking water with chlorine, selecting mycobacteria by reducing competition and (ii) disinfection attempts in medical and industrial settings. In 1999–2000, an estimated 1 in 6 persons in the USA demonstrated Mycobacterium intracellulare sensitization, up from 1 in 9 persons in 1971–1972. This observed rising prevalence of sensitization (as a measure of increased exposure) has paralleled the increase in rate of pulmonary NTM infections.6 A similar increase in NTM infections has also occurred in the Asia-Pacific region.2,7 In Queensland, Australia, where NTM disease is notifiable and a central laboratory performs all mycobacterial speciation, speciated pulmonary isolates from patients increased from 5.5 to 10.2 per 100 000 population between 1999 and 2005. M. intracellulare accounted for most of this increase. Significant pulmonary disease rose from © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology Respirology (2009) 14, 12–26 doi: 10.1111/j.1440-1843.2008.01408.x Key words: anti-mycobacterial therapeutics, bronchiectasis, lung diseases, mycobacteria, nontuberculous. INTRODUCTION Non-tuberculous mycobacteria (NTM) generally refer to mycobacteria other than Mycobacterium tubercu- Treatment of pulmonary NTM disease 2.2 to 3.2 per 100 000 (Thomson, unpubl. data, 2007). Marras et al. reported a similar increase in Ontario, Canada between 1997 and 2003.4 Mycobacterium avium complex (MAC), Mycobacterium kansasii and rapidly growing mycobacteria (RGM) such as M. abscessus and M. fortuitum constitute the main species associated with human pulmonary disease.7–9 While the underlying reason has not been totally unravelled, the higher innate resistance of MAC to chlorine and ozone, in comparison to other NTM, might help to explain the phenomenon. Other important NTM that can cause pulmonary infections/diseases are Mycobacterium xenopi, Mycobacterium malmoense and Mycobacterium szulgai.7–9 DIAGNOSIS OF PULMONARY NTM DISEASES Clinical features of NTM lung diseases Pulmonary diseases due to NTM generally belong to one of the following four patterns. (i) Fibrocavitary disease (Fig. 1) classically involves the upper lobes of middle-aged men with histories of smoking and alcoholism, and often with underlying lung diseases like COPD, previous tuberculosis and silicosis. This form of disease is particularly associated with MAC, M. 13 kansasii,10 M. xenopi,11 M. malmoense12 and RGM.13 (ii) Nodular bronchiectasis (Fig. 2) generally involves elderly non-smoking women with no underlying lung disease, but who may have thoracic deformities like pectus excavatum, kyphosis and scoliosis.14 (iii) Solitary pulmonary nodule15–19 presents very much like a tuberculoma, and has to be differentiated from a carcinoma.16 (iv) Hypersensitivity pneumonitis occurs in previously healthy subjects with exposure to contaminated indoor hot tubs19 or contaminated metal working fluids.20,21 In the interpretation of the literature on NTM disease, it is important to appreciate the proportion of patients in each of the above groups. There is a feeling among clinicians that the cavitary form of disease is becoming less common, while the nodular bronchiectatic form is more prevalent. This has important implications for treatment trials and epidemiological studies. COPD,3 cystic fibrosis,22 gastro-oesophageal reflux disease and vomiting23 and chest wall disorders14 have all been associated with NTM lung diseases. One large, multicentre study reported that NTM were isolated from the respiratory secretions of 13% of patients with cystic fibrosis.22 Recently, NTM and bronchiectasis together have been found to be associated with a higher risk of Aspergillus lung disease.24 The association between NTM colonization/infection and unselected cases of bronchiectasis still remains Figure 1 X-ray and CT scan of a patient with the cavitary form of pulmonary non-tuberculous mycobacteria disease, in association with COPD. Figure 2 Chest X-ray and CT cuts of a patient with the fibro-nodular bronchiectatic form of pulmonary non-tuberculous mycobacteria disease. © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology Respirology (2009) 14, 12–26 14 elusive, though it is likely that bronchiectasis acts as a predisposing underlying lung disease. The signs and symptoms of NTM lung diseases are generally non-specific. Malaise and chronic cough (with and without sputum production) are very common. Dyspnoea is more related to underlying lung disease (except with hypersensitivity pneumonitis). Occasional patients with the nodular bronchiectasis can have bronchiolitis and gas trapping associated with dyspnoea. Fatigue, weight loss and sweats also occur particularly as disease progresses. Haemoptysis occurs in more advanced lung disease, especially with cavitation and advanced bronchiectasis. Radiographic assessment of NTM lung diseases Cavitary NTM disease can be readily assessed by plain chest radiograph. The cavities are said to have thinner walls, and are associated with less surrounding parenchymal lesions, but more pleural reactions than those of tuberculosis. Other forms of NTM lung disease are better assessed by high-resolution CT (HRCT). The prevalent HRCT findings are bilateral centrilobular nodules and cylindrical bronchiectasis.25 These changes correlate with bronchiolar/peribronchiolar inflammation due to tissue invasion by NTM like MAC and M. abscessus.5 It has been suggested that about 30% of patients with changes of bilateral bronchiectasis and bronchiolitis on HRCT had NTM disease;26 extensive radiographic abnormalities, cavitation or consolidation and female gender provided additional risks. Classically, multifocal bronchiectasis and diffuse centrilobular nodules, especially involving the middle and lingular lobes found in elderly non-smoking women has been referred to as the Lady Windermere syndrome.27 Serial CT scanning in MAC lung disease has shown that bronchiectasis tends to be progressive, alongside spread of nodules. Finally progression to consolidation can also occur.28,29 In ‘hot tub’ lung due to MAC-associated hypersensitivity pneumonitis, chest CT often demonstrates diffuse ground-glass infiltrates and centrilobular nodules.30 A similar clinical and radiological syndrome occurs after exposure to metalworking fluid contaminated with M. immunogenum, a RGM closely related to M. abscessus.20,21 Solitary pulmonary nodules or masses have been described in several NTM lung diseases,15,17 though apparently rare. Identification of NTM and drug susceptibility testing NTM can be divided into slowly growing mycobacteria and RGM (Table 1). The former constitute members of the Runyon group I to group III, whereas the latter are equivalent to members of the Runyon group IV.31 Using modern microbiology laboratory methods, including liquid culture media, NTM growth can be detected by culture from patient specimens 1–3 weeks after incubation.32 Most rapid Respirology (2009) 14, 12–26 RM Thomson and W-W Yew Table 1 Classification of mycobacterial commonly causing human disease species Mycobacterium tuberculosis complex M. tuberculosis M. bovis M. africanum M. microti Slowly growing mycobacteria Runyon Group I, Photochromogens M. kansasii M. marinum Runyon Group II, Scotochromogens M. gordonae M. scrofulaceum Runyon Group III, Non-chromogens M. avium complex—M. avium, M. intracellulare M. terrae complex M. ulcerans M. xenopi M. simiae M. malmoense M. szulgai M. asiaticum Rapidly growing mycobacteria Runyon Group IV M. fortuitum M. chelonae M. abscessus growing NTM will grow in 7–10 days. Slow growers can grow in 1–3 weeks, but may take much longer. Cultures are usually kept for 6–8 weeks before being regarded as negative. In patients with chronic bronchial sepsis, such as cystic fibrosis and bronchiectasis, where colonization by Pseudomonas aeruginosa and other bacterial pathogens prevails, sputum specimens can be overgrown before NTM growth appears. Special decontamination methods are often necessary to reduce this overgrowth. Decontamination unfortunately reduces the yield of mycobacteria also, and persistence is needed if there is a clinical suspicion of NTM disease in these patients. Although semi-quantitative smear and culture results were used previously as NTM diagnostic criteria,33 the current use of liquid media has put less emphasis on such an approach. With recovery of the organism by culture, DNA probes are commercially available to identify some of the NTM—MAC, M. kansasii and M. gordonae. Other organisms have traditionally been identified by a combination of biochemical testing and HPLC. DNA amplification with PCR has emerged as a technique to aid the rapid identification of mycobacterial isolates. One such approach utilizes a multiplex PCR34 to identify multiple mycobacterial pathogens. Partial sequencing of a segment of 16S ribosomal RNA, sometimes complemented by sequencing of the 16S–23S internal transcribed spacer, has been used35,36 to identify those species not identified by other means. Clinically significant NTM isolates should be identified to the species level, except perhaps for M. © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology 15 Treatment of pulmonary NTM disease avium and M. intracellulare.37 The American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA) guidelines state that routine testing of MAC species for antimicrobial susceptibility (other than clarithromycin) is not generally recommended because of the paucity of evidence correlating in vitro results and in vivo (clinical) response.37 However, it has been postulated that drug combinations can produce synergistic activity, in both in vitro and in vivo settings.38,39 Some authors have shown a relationship between clinical response to treatment and administration of drugs to which the strains had demonstrated susceptibility.40–43 Patients with nodular bronchiectasis may be infected with multiple strains and even species at different time points in their disease;44 however, the significance of this with respect to treatment and antibiotic susceptibility is uncertain. The ATS does recommend clarithromycin susceptibility testing for new, previously untreated MAC isolates37 as macrolide resistance has been associated with a poorer outcome. It should also be performed for MAC isolates from patients who have failed macrolide treatment, or who have relapsed from apparently successful treatment. Previously untreated M. kansasii strains should be tested in vitro to rifampicin only.37 M. kansasii isolates resistant to rifampicin should be tested against a panel of secondary agents, inclusive of rifabutin, ethambutol, isoniazid, clarithromycin, fluoroquinolones, amikacin and sulphonamides. RGM should be tested against a panel of eight antimicrobials for susceptibility.37 This testing helps in identification of M. abscessus, M. chelonae and M. fortuitum as well as guidance of antimicrobial therapy. The eight drugs are amikacin, cefoxitin, clarithromycin, ciprofloxacin, doxycycline, linezolid, sulphamethoxazole and tobramycin. Other diagnostic tests for NTM lung diseases Skin test antigens specific for NTM species are no longer readily available for use. They do exhibit crossreaction with tuberculin and recent sequencing of the genome of M. avium has demonstrated that the strain of M. avium used in the avian skin test is not associated with human disease.45 The sensitivity, specificity and positive predictive value of PPD-B (M. intracellulare) and NTM disease were 70%, 61% and 64% respectively in one study, and the authors concluded it was no more useful in distinguishing pulmonary disease due to NTM than PPD-T alone.46 Thus, skin testing using these antigens has little role in the diagnosis of NTM lung disease. New interferon-g (IFN-g) release assays utilizing antigens largely specific for M. tuberculosis may help to differentiate active pulmonary tuberculosis from NTM lung disease,47,48 but these data are preliminary at present. It is useful to note that the M. tuberculosisspecific antigen, ESAT-6 is also present in M. kansasii, M. marinum and M. szulgai, and thus exposure to these NTM could result in false-positive test results. © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology Diagnostic criteria for NTM lung diseases Not all patients who have mycobacteria cultured from sputum or bronchial specimens are considered to have disease. It has been postulated that they are transiently contaminated or colonized by these organisms and that ingested water or inhaled aerosols are the source of the organisms.49,50 Wolinsky51 described three stages of interaction between the organism and host—colonization, infection and disease. The progression through these stages is dependent on the quantity of growth, repetitive isolation, the site of isolation, the species of organism and underlying host condition. Colonization can be defined as repeated isolation of an organism without evidence of a host response. The concept of colonization with NTM in the lung without infection or invasion is debated.52 The ATS guidelines on the management of non-tuberculous mycobacterial disease33 state that ‘colonisation in the true sense (i.e. no tissue invasion) is probably quite rare’. The ATS have proposed criteria to differentiate between colonization/contamination and disease, and encompass bacteriological, radiological and clinical criteria (Table 2).37 The criteria of 2007 have relaxed the microbiologic criteria, as it is recognized that patients with nodular bronchiectasis have paucibacillary disease and shed organisms intermittently, and therefore it can be difficult to document positive specimens repeatedly. The bacteriological criteria of 199733 may have led to an under-diagnosis of disease, yet the criteria from 2007 may allow over-diagnosis. Hence positive cultures need to be interpreted in light of the findings on CXR/HRCT (as a means of assessing Table 2 Summary of the ATS/IDSA criteria for diagnosis of pulmonary NTM diseases Clinical and radiographic (both required): Pulmonary symptoms, nodular or cavitary opacities on chest radiograph, or a HRCT scan that shows multifocal bronchiectasis, alongside multiple small nodules, AND Appropriate exclusion of other diagnoses, especially tuberculosis and mycosis Microbiological Positive culture results from at least two separately expectorated sputum samples. If results are non-diagnostic, consider repeat smears and cultures OR Positive culture results from at least one bronchial wash or lavage OR Transbronchial or other lung biopsy with mycobacterial histopathological features (granulomatous inflammation or stainable acid-fast bacilli), positive culture for NTM or biopsy showing mycobacterial histological features, and ⱖ1 sputum or bronchial washings that are culture positive for NTM. ATS/IDSA, American Thoracic Society/Infectious Diseases Society of America; HRCT, high-resolution CT; NTM, non-tuberculous mycobacteria. Respirology (2009) 14, 12–26 16 tissue invasion/host response) and the symptoms as well as underlying diseases of the patient. The significance of an isolate also varies with the species of mycobacteria. Isolation of mycobacteria like M. gordonae, M. mucogenicum, M. haemophilum, M. flavescens, M. gastri, M. terrae complex or M. triviale usually indicates transient colonization or contamination though disease has been reported. Because M. szulgai is rarely isolated from the environment, a single positive culture is usually pathologically significant.37 Similarly, many would like to relax the bacteriological criteria for diagnosing M. kansaii lung disease, by allowing diagnosis of disease with a single positive culture result, provided the clinical and radiographic grounds are strong.53 In general, expert consultation should be obtained, when NTM are recovered, that are either infrequently encountered, or that usually represent environmental contaminants. Treatment recommendations for these NTM are usually made on the basis of only a few reported cases. On the other hand, treatment recommendations for species like MAC and M. kansasii are generally more evidence based. Empiric therapy for suspected NTM lung disease is not recommended. Such cases should be followed up closely, until diagnosis is firmly established or excluded.37 WHEN TO TREAT PULMONARY NTM DISEASES Diagnosing pulmonary NTM infection/disease does not equate to the need for immediate treatment. Treatment constitutes an important undertaking for the physician and patient as it usually involves combination antibiotic therapy for 12–24 months. In some cases disease remits spontaneously. Indeed, lung involvement may range in severity from subclinical/ mild clinical (indolent) infection to disease associated with extensive invasion/destruction of the lungs. Early studies of MAC disease demonstrated a variable progression of infection, but the majority of symptomatic (and some supposedly asymptomatic) patients had progressive disease, and often died as a result.54,55 However, most of these early studies consisted of patients with cavitary disease, often associated with heavy smoking, COPD or other underlying lung disease, and alcohol excess—factors likely to affect mortality and response to treatment. There are few studies documenting the natural history of nodular bronchiectasis, which often occurs in the absence of significant co-morbidity; however, it seems to be quite variable. While the progression of disease is generally slower than in cavitary disease, it can lead to respiratory failure and death.56 There are also differences in the natural history of infection with different species and probably also between different strains within species.57 M. kansasii tends to be more associated with a tuberculosis-like illness, and is generally easier to treat—therefore the threshold for treatment with antimicrobials is somewhat lower, than for example, with M. abscessus. This latter pathogen is notoriously difficult to eradicate and requires a combination of Respirology (2009) 14, 12–26 RM Thomson and W-W Yew injectable antibiotics. This prospect often raises the threshold for the institution of therapy. Therefore, the decision to treat should involve a period of observation—usually for between 3 and 12 months—both for radiological and symptomatic progression. Apart from the usual symptoms of cough ⫾ sputum production, weight loss, fevers and sweats, the occurrence of frequent intercurrent infections due to other bacteria may be a suggestion of underlying inflammation caused by the presence of mycobacterial infection. Factors to consider in the decision to treat also include the patient’s age and potential for progressive parenchymal damage due to NTM, leading to colonization and infection with other pathogens (such as other species of mycobacteria, Pseudomonas aeruginosa, Sternotrophomonas and Aspergillus). A younger patient (<75 years) without major comorbidity has more to lose in terms of quality of life if disease is left untreated than a patient in his/her eighties with multiple comorbidities. It has been suggested that patients with more advanced radiological changes are less likely to respond to therapy,58,59 which would favour early treatment, particularly in the younger patient. Similarly, the presence of predisposing conditions, may affect the rate of progression of disease. Patients on immunosuppressive medication, or with hereditary disorders of immune function, may have more rapidly progressive disease and warrant earlier and more aggressive treatment. Patients with very little pulmonary reserve due to other disease (such as severe COPD, advanced bronchiectasis) may also warrant a more aggressive approach, as a delay in treatment while waiting for evidence of progressive NTM disease may contribute to significant morbidity. In instituting therapy, there is a need to establish realistic expectations regarding outcomes. In many patients the aim should be cure, and an aggressive approach warranted. In others it may simply be suppression in order to achieve symptom control. The cost, drug–drug interactions, side-effects and unclear impact of treatment on the quality and quantity of life should be considered. For some patients close observation and use of adjunctive therapies, such as airway clearance techniques, attention to underlying lung disease, gastro-oesophageal reflux disease, swallowing disorders and nutrition, may be a reasonable option. The risks (including potential adverse reactions) and benefits (such as improvement in symptoms, preservation of lung function, reduced risk of added infections) of antimicrobial therapy should be extensively discussed with the patient prior to deciding whether to institute such therapy. HOW TO TREAT PULMONARY NTM DISEASES General principles Patients respond best to NTM treatment the first time it is administered; therefore, it is very important that patients initially receive a recommended © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology 17 © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology Not recommended for severe/advanced/previously treated disease. ‡ Lower dose for body weight <50 kg. § If intolerance to rifampicin or ethambutol, clarithromycin or ciprofloxacin may be substituted. ¶ Given intermittently for the first 2–3 months. †† Given intermittently for the first 2–6 months. ‡‡ May be added if the patient is responding poorly at 12 months. ATS, American Thoracic Society; Azi, azithromycin; BD, two-times daily; BTS, British Thoracic Society; Clar, clarithromycin; JST, Japanese Society for Tuberculosis; MAC, Mycobacterium avium complex; TIW, three-times weekly. 12 months culture negative Duration Other drugs None Aminoglycoside † 12 months culture negative 12 months culture negative Isoniazid 300 mg/day Or Ciprofloxacin 750 mg bd‡‡ 2 years None or Amikacin or Streptomycin¶ Rifabutin 250–300 mg/day or Rifampicin 450‡–600 mg/day Amikacin or Streptomycin Rifampicin 450‡–600 mg/day Rifamycin 2 years Streptomycin or kanamycin†† Rifampicin 10 mg/kg/day Rifampicin 450‡–600 mg/day 15 mg/kg/day 15 mg/kg/day None§ Clar 500‡–1000 mg/day Or Azi 250‡–300 mg/day 15 mg/kg/day Clar 500‡–1000 mg/day Or Azi 250‡–300 mg/day 15 mg/kg/day Clar 1000 mg TIW Or Azi 500–600 mg TIW 25 mg/kg/day TIW Rifampicin 600 mg TIW Macrolide ATS Advanced (severe) or pretreated disease ATS Initial treatment of cavitary disease The treatment recommendations for MAC lung disease are summarized in Table 3. The ATS/IDSA recommended initial regimen for patients with mild nodular-bronchiectatic MAC lung disease is a three-times-weekly regimen including clarithromycin 1000 mg or azithromycin 500 mg, ethambutol 25 mg/kg and rifampicin 600 mg.37 Intermittent drug therapy is not recommended for patients with cavitary disease, patients who have been previously treated or patients who have moderate to severe disease.37,64 The ATS/IDSA recommended initial regimen for fibrocavitary or moderate to severe nodularbronchiectatic MAC lung disease includes daily clarithromycin 500–1000 mg/day or azithromycin 250 mg/day, ethambutol 15 mg/kg/day and rifampicin 10 mg/kg/day (maximum 600 mg), assuming normal liver and renal status. Lower doses of clarithromycin may be necessary in patients over 60 years of age who have low body weights. Aminoglycosides should be considered in the initial phase and are recommended for patients with severe or previously treated disease. The ATS guided primary microbiological goal is 12 months of negative sputum cultures prior to stopping ATS Initial treatment of nodular BE† MAC lung disease Table 3 Recommended treatment regimens for pulmonary MAC disease Only the pulmonary diseases due to the commonly encountered NTM organisms will be discussed below. The British Thoracic Society (BTS),61 Japanese Society for Tuberculosis,62 and ATS/IDSA37 have published guidelines for the management of disease due to NTM. While the British guidelines have not been updated since 1999, a recent randomized controlled trial performed by the BTS63 gives insight into their latest recommendations. The BTS guidelines are predominantly based on two large randomized controlled studies42,63 and historical studies performed in patients of the UK and Europe. The Japanese guidelines are very similar to those of the ATS/IDSA. The ATS/IDSA document is an extensive review of the available literature on NTM diseases combined with expert opinion, and the most recent version was published in 2007. The recommended treatment criteria are based on several smaller prospective nonrandomized controlled studies (using historical controls), in US patients. It is very difficult to compare the many different treatment studies done in pulmonary NTM disease. Geographic differences in patient populations, mix of disease type (i.e. nodular bronchiectasis vs cavitary disease), severity of disease, differing species of NTM, drugs used and dosages and study design and analysis are all factors contributing to the significant heterogeneity of findings and hence the recommendations made by the Societies. BTS Specific antimicrobial treatment guidelines Ethambutol JST multi-drug regimen.37,60 During chemotherapy, longterm management consists of microbiological surveillance, management of drug toxicity, nutrition and comorbidities. Clar 10 mg/kg/day Treatment of pulmonary NTM disease Respirology (2009) 14, 12–26 18 RM Thomson and W-W Yew therapy,37 as counted from the first of at least three consecutive negative sputum cultures. Macrolides should not be used as monotherapy for MAC disease because of the risk for developing macrolide-resistant MAC isolates.65–67 Macrolide-resistant MAC lung disease67 is difficult to treat and often requires prolonged parenteral aminoglycoside therapy and surgery. Similar to the ATS/IDSA, the JST recommends a combination of streptomycin, clarithromycin, E and R for all patients. In contrast, the BTS recommends 2 years of rifampicin (R) and ethambutol (E) ⫾ isoniazid (H) for MAC disease.61 Its recent randomized controlled trial (RCT) compared the addition of ciprofloxacin or clarithromycin to ER over 2 years.63 There was an additional option to compare M. vaccae immunotherapy in each arm. It is important to note that this study included 170 patients with MAC, 67% of whom had cavitary disease, and 54% had evidence of an underlying respiratory condition on CXR. The authors concluded there was no additional benefit in adding either clarithromycin or ciprofloxacin to ER, as the number of patients alive and cured at 5 years were similar, both for each arm of the trial and the results of a previous trial comparing ER and ERH. ERH had the best success rate, but highest disease associated mortality. ERclarithromycin was associated with the highest all-cause mortality. Interestingly, the reported side-effects leading to a change of treatment in the ERclarithromycin/ ERciprofloxacin trial were twice that of the ER/ERH trial. As such, their suggested treatment regimen would be 24 months ER with H or ciprofloxacin added at 12 months if patients were doing poorly. No analysis was performed according to radiological presentation as cavitary disease versus nodular bronchiectasis. Such data may be useful in assessing the relevance of the findings to these patient groups, as those with bronchiectasis may potentially benefit from both the anti-pseudomonal properties of ciprofloxacin, and the anti-inflammatory properties of clarithromycin. Similarly, the BTS makes no distinction in recommended therapy between the two radiological groups. There are still a number of controversies and unresolved questions in the management of MAC lung disease. First, there have been no head-to-head comparative trials between clarithromycin- and azithromycin-containing regimens for MAC lung disease. Thus, there is no demonstrated superiority of one macrolide among the two agents regarding efficacy or risk of resistance. It is felt that macrolides have helped to improve treatment of MAC lung disease,59 though not all studies have supported this.63 It would appear that this assumption may be more valid for patients with nodular bronchiectasis, rather than cavitary disease with the results of clinical studies at variance. If patients have not been pre-treated and are able to tolerate the medications for the required period of time, sputum conversion may be up to 90%,65,66 though overall success rates (12 months culture negative) with macrolide containing regimens range between 55% and 83%.37,65,66,68,69 Perhaps the immunomodulating effect of macrolides could be beneficial to some patients with bronchiectasis associated with NTM lung disease. When multiple drugs are prescribed at once in a treatment naive patient, gastrointestinal intolerance frequently results. Many experts would recommend a stepwise introduction to therapy. Clarithromycin seems to be the agent most patients have problems with, and it may be necessary to start at a dose of 250 mg twice daily, increasing to 500 mg twice daily after 1–2 weeks, prior to the introduction of companion drugs. While this approach would not be acceptable for tuberculosis, because of the risk of development of resistance, macrolide resistance in MAC develops comparatively slowly.65,66 Second, there has also been no demonstrated superiority of one rifamycin (rifabutin or rifampicin) in the treatment of MAC lung disease, but because of frequent adverse events (uveitis, leucopenia, etc.), most experts recommend the use of rifampicin.70,71 The roles for other medications such as fluoroquinolones and clofazimine in the treatment of MAC lung disease have not been fully explored, notwithstanding a report on the clinical efficacy of clofazimine,69 the recent BTS study63 which included ciprofloxacin, and a few reports regarding the in vitro and in vivo efficacy of moxifloxacin against MAC.72,73 The issue of whether an aminoglycoside should be used in the initial phase of treatment also needs to be addressed. The majority of early macrolide studies performed in the USA, included a 2- to 3-month period of intermittent injectable aminoglycoside. The JST guidelines from 1998 recommend initial streptomycin/kanamycin, with oral ERclarithromycin. Kobashi59 compared outcomes between patients treated 1993–1998, prior to these guidelines (when only 2.8% of patients received this combination) to those treated 1998–2003 (64.5% patients received combination). Sputum conversion rates, relapse rates and overall outcomes were better in the cohort treated with the recommended regimen. A Japanese RCT74 randomized patients to receive ERclarithromycin with or without intramuscular streptomycin for the first 3 months. Sputum conversion was significantly higher in those that received aminoglycoside, however, overall outcomes and relapse/reinfection rates were similar between the two groups at study conclusion. None of the BTS studies have used aminoglycosides, and the BTS does not include a role for these injectables in treatment guidelines. For hypersensitivity pneumonitis due to MAC, the treatment strategy appears somewhat different. Removal of the subject from environmental exposure to the contaminating source is mandatory. Corticosteroids and/or anti-mycobacterial drugs might be required to bring about improvement of the disease.37 When the latter are needed, a shorter regimen of 3–6 months may be appropriate.75 Respirology (2009) 14, 12–26 © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology M. kansaii lung disease For patients with lung disease due to rifampicin susceptible M. kansasii, treatment recommendations are summarized in Table 4. The ATS/IDSA recommend a daily regimen including rifampicin 10 mg/kg/day (maximum, 600 mg), ethambutol 15 mg/kg/day, 19 Treatment of pulmonary NTM disease Table 4 Recommended treatment regimens for rifampicin-susceptible Mycobacterium kansasii pulmonary disease Ethambutol Rifampicin Isoniazid‡ Duration ATS BTS 15 mg/kg/day 10 mg/kg/day (max 600 mg) 5 mg/kg/day (max 300 mg/day) 12 months culture negative 15 mg/kg/day 450†–600 mg/day 9 months † Lower dose for body weight <50 kg. ‡ Plus pyridoxine 50 mg/day. ATS, American Thoracic Society; BTS, British Thoracic Society. isoniazid 5 mg/kg/day (maximum, 300 mg), assuming normal underlying liver and renal chemistries.37 The treatment duration for M. kansasii lung disease should include 12 months of negative sputum cultures. There have been no prospective studies evaluating the efficacy of 18 months of therapy versus shorter (9 or 12 months) treatment durations. One small study demonstrated that adding intermittent streptomycin twice weekly for the first 3 months to the three-drug regimen given for 12 months resulted in apparent cure in 98% cases.76 The BTS guidelines recommend a combination of ethambutol and rifampicin given for 9 months.61 This is largely based on a prospective study organized by the British Thoracic Society in which good results (99% sputum culture conversion) were achieved.77 However, the relapse rate of 10% still appeared high and for many physicians, unacceptable, compared with results achieved with longer duration of therapy with the addition of isoniazid. For patients with rifampicin-resistant M. kansasii disease, a three-drug regimen is recommended by the ATS, based on in vitro susceptibilities including clarithromycin or azithromycin, moxifloxacin, ethambutol, sulphamethoxazole and streptomycin.37 High-dose isoniazid, high-dose ethambutol and sulphamethoxazole combined with prolonged streptomycin/amikacin administration gave good results in one report.78 M. kansasii generally is quite susceptible in vitro to clarithromycin. A recent preliminary study on 18 patients receiving three-timesweekly therapy with rifampicin (600 mg), ethambutol (25 mg/kg) and clarithromycin (500–1000 mg) reported that 12 months of negative sputum cultures was associated with no disease relapses at 46 ⫾ 8 months of (mean ⫾ SD) follow up.79 Moxifloxacin and linezolid80 are also promising agents based on in vitro data, but clinical data are still lacking. M. malmoense, M. szulgai and M. xenopi lung diseases Mycobacterium malmoense strains have variable susceptibility patterns to antimicrobials. They have © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology shown susceptibility in vitro to ethambutol, ethionamide, kanamycin and cycloserine and resistance to isoniazid and rifampicin.81 Pulmonary disease due to M. malmoense can be difficult to treat.37 A combination of rifampicin and ethambutol with or without isoniazid has shown some effectiveness.12,42,82 There have been two randomized controlled trials performed by the BTS. The first compared ER with ERH, and the outcomes were similar between the two groups, with 42% of patients alive and cured at 5 years.42 This study demonstrated no correlation between in vitro antibiotic susceptibilities to individual drugs and clinical response. The second, more recent study, compared the addition of ciprofloxacin or clarithromycin to ER (again with the option of M. vaccae in each arm).63 The proportion of people alive and cured at 5 years was 38.4% in the clarithromycin arm and 19.8% in the ciprofloxacin arm. The authors conclude that there is little difference between ER, ERH and ERclarithromycin in terms of outcome, but the use of clarithromycin is likely to be associated with increased side-effects. Mycobacterium szulgai is susceptible in vitro to most antituberculosis drugs, as well as to fluoroquinolones and macrolides.83,84 Although the optimal duration of therapy has not been delineated, a 3- or 4-drug regimen that includes 12 months of negative sputum cultures while on therapy appears adequate.37 Mycobacterium xenopi has variable drug susceptibility testing results that are hard to interpret, especially regarding the first-line antituberculous agents.37 The clinical response to treatment does not always correlate well with drug susceptibility testing results. Patients with disease due to M. xenopi were also included in the two BTS randomized controlled trials; however the numbers were small in this group. The BTS approach to treatment has been to use standard drugs in combination—ER ⫾ isoniazid;61 however, the more recent study suggests that clarithromycin may have a role.63 The ATS proposed regimen is a combination of ER,isoniazid and clarithromycin ⫾ an initial course of streptomycin.37 Moxifloxacin also has good in vitro activity against M. xenopi.85 Nevertheless, the mortality of lung disease due to M. xenopi can be high and the outlook from treatment is poor, possibly reflecting severe underlying pulmonary conditions.42,86 Lung diseases due to rapidly growing mycobacteria The three main species of RGM causing pulmonary diseases are M. abscessus, M. chelonae and M. fortuitum. Treatment relies heavily on guidance from antimicrobial susceptibility testing as there are virtually no large-scale clinical studies. Most data emerge from case reports87,88 or small series.13 The treatment of M. abscessus particularly can be quite difficult as it is highly resistant to antituberculous drugs. Treatment usually involves a combination of amikacin, cefoxitin/imipenem and clarithromycin. However, this is difficult to administer or tolerate for long periods. Respirology (2009) 14, 12–26 20 RM Thomson and W-W Yew Table 5 Treatment of diseases due to rapidly growing mycobacteria Mycobacterium abscessus Mycobacterium chelonae Mycobacterium fortuitum † Active drugs Duration Surgery Clarithromycin† Amikacin† Cefoxitin† Imipenem Linezolid‡ Tobramycin† Clarithromycin† Linezolid‡ Imipenem Amikacin Clofazimine Doxycycline Ciprofloxacin Amikacin† Ofloxacin†/Ciprofloxacin† Imipenem† Sulphonamides Clarithromycin Doxycycline 4 months (soft tissue) 6 months (bone) ? 12 months (lung) ++ 4 months (soft tissue) 6 months (bone) ? 12 months (lung) + 4 months (soft tissue) 6 months (bone) ? 12 months (lung) + Quite active agents. ‡ Newer active agent. Mycobacterium fortuitum can be more amenable to treatment as antimicrobial susceptibility testing often provides a much wider range of oral agents to choose from, including the macrolides, newer quinolones, doxycycline, minocycline and sulphonamides. Table 5 shows a summary of proposed treatment, inclusive of choice of drugs with duration and use of surgery. The goal of 12 months of negative sputum cultures while on therapy may be reasonable37,89 for M. fortuitum. However, few medication strategies for M. abscessus appear to be tolerable to achieve this goal reliably. Isolated case reports of successful treatment without relapse using shorter duration of therapy have been noted.87,88 It might be more realistic to consider intermittent treatment courses during exacerbations of the disease, especially when parenteral drugs are involved.37 Expert consultation is recommended for the management of patients with this disease. Side-effects and drug interactions Table 6 depicts the possible adverse reactions of drugs commonly used in the treatment of NTM lung diseases. The BTS recommended combination of rifampicin, and ethambutol only for treatment of lung diseases due to MAC, M. xenopi and M. malmoense has managed to produce cure rates of 30–40%.12,42,90 All-cause mortality has been up to 40% but diseaserelated mortality has stayed low. Nevertheless, drug tolerance was reasonable, especially when only rifampicin and ethambutol were used. The addition of clarithromycin or ciprofloxacin resulted in a doubling of drug side-effects.63 Curiously, the combination of ethambutol with clarithromycin resulted in Respirology (2009) 14, 12–26 more ocular toxicity than with ciprofloxacin, though there were some difficulties with documentation of ethambutol as a direct cause of visual problems. It is thus uncertain whether the conventional ER regimen should be completely abandoned. Macrolides can be quite toxic in elderly subjects, and dosage adjustment is often required.91,92 Ethambutol is reportedly less oculotoxic when given on an intermittent basis,93 and this may be advantageous in older patients. Rifampicin, while commonly administered with clarithromycin, has been shown to reduce the serum levels of the macrolide, through induction of cytochrome P-450 enzymes.94 However, the clinical significance of this interaction remains unknown. Laboratory data also revealed that the interaction of rifabutin with clarithromycin was less. Other drug– drug interactions of clinical significance involving clarithromycin in the treatment of patients with MAC disease have also been reported (Table 7), largely in HIV-infected patients.95 Compared with clarithromycin, azithromycin has fewer pharmacokinetic interactions, does not appear to prolong the QT interval as much and may be better tolerated overall. Adjunctive therapies A substantial proportion of patients with pulmonary NTM diseases have significant bronchiectasiscausing morbidity, thus mucus clearance strategies are likely to be beneficial. These methods include conventional chest physiotherapy and postural drainage, augmented by autogenic drainage and active cycle of breathing techniques; mucus clearance devices;96 and inhaled medications such as mannitol97 © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology 21 Treatment of pulmonary NTM disease Table 6 Adverse reactions to drugs used for treatment of NTM diseases Reactions Drug Common Uncommon Isoniazid Hepatitis Cutaneous hypersensitivity Peripheral neuropathy Rifampicin Hepatitis Cutaneous hypersensitivity Gastrointestinal reactions Thrombocytopenic purpura Febrile reactions ‘Flu syndrome’ Uveitis Leucopenia Thrombocytopenia ‘Flu syndrome’ Hepatitis Retrobulbar neuritis Arthralgia Rifabutin Abnormal taste Arthralgia Ethambutol Streptomycin Amikacin Kanamycin Capreomycin Clarithromycin Azithromycin Ofloxacin Ciprofloxacin Levofloxacin Moxifloxacin Clofazimine Linezolid † ⎧ ⎨ ⎩ Cutaneous hypersensitivity Dizziness Numbness Tinnitus Ototoxicity: hearing loss, vestibular disturbance Nephrotoxicity: deranged renal function Nausea Dyspepsia Nausea Vertigo Ataxia Deafness Rare Dizziness Convulsion Optic neuritis Mental symptoms Haemolytic anaemia Aplastic anaemia Lupoid reactions Arthralgia Gynaecomastia Shortness of breath Shock Haemolytic anaemia Acute renal failure Shock Haemolytic anaemia Hepatitis Cutaneous reaction Peripheral neuropathy Renal damage Aplastic anaemia Clinical renal failure Hypokalaemia Hypocalcaemia Hypomagnesaemia Diarrhoea Abdominal pain Rash Hepatic dysfunction Diarrhoea Abdominal pain Rash Anxiety Dizziness Headache Tremor Hearing loss QT prolongation Gastrointestinal reactions Retinopathy Intestinal obstruction Thrombocytopenia Aplastic anaemia† Colitis Peripheral and optic neuropathies† Hepatic dysfunction Tinnitus Hearing loss Gastrointestinal reactions Convulsion ⎧ Haemolysis ⎨ Insomnia ⎩ Oral candidiasis Tendonitis/Tendon rupture Arthropathy Colitis Similar to those of ofloxacin or ciprofloxacin except less central nervous system dysfunction Photosensitization Hyperpigmentation Cutaneous reactions Diarrhoea Dyspepsia Headache More common with prolonged administration. NTM, non-tuberculous mycobacteria. or hypertonic (7%) saline.98 Nutritional status should also be monitored in the management of pulmonary disease. Attention to conditions that cause aspiration may also help to minimize pulmonary contamination or prevent re-infection in treated patients. So far, none of the adjunctive interventions has been specifically evaluated in patients with pulmonary NTM diseases, and such studies may be warranted. © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology Respirology (2009) 14, 12–26 22 RM Thomson and W-W Yew Table 7 Examples of drug–drug interactions involving clarithromycin in treatment of MAC disease Drug Rifabutin Statin lipid-lowering agents Cyclosporine Terfenadine Nevirapine Efavirenz Itraconazole Delavirdine HIV protease inhibitors Result ↑ level of rifabutin ↑ level of statins ↑ level of cyclosporine ↑ level of terfenadine ↓ level of clarithromycin ↓ level of clarithromycin ⫾↑ level of clarithromycin ⫾↑ level of clarithromycin ⫾↑ level of clarithromycin MAC, Mycobacterium avium complex. Surgical treatment Surgical resection of limited (focal) pulmonary NTM disease (especially upper lobe cavitary disease) in a patient with adequate cardiopulmonary reserve can be successful in combination with multi-drug treatment regimens for MAC and M. abscessus lung diseases.37,99 Surgical resection of a solitary pulmonary nodule due to MAC is indeed also considered by experts to be curative, though the data to support this assumption are lacking.37 Other indications for surgical resection include failure of medical therapy,99,100 serious intolerance to drugs for treatment100 and macrolide-resistant MAC lung disease.67 Data have shown that, in light of good long-term results, surgery should be recommended before disease becomes exceedingly advanced and unresectable.101,102 In addition, in extensive disease, the excision of large cavitary mycobacterial foci might assist medical management of remaining lesions.102 Despite bronchial stump protection, pneumonectomy still carries a risk for bronchopleural fistula. However, pneumonectomy does help to confer high cure rates in patients with NTM lung diseases.103 Surgery should, therefore, be performed in centres with considerable medical and surgical expertise in the management of patients with NTM disease.37 Issues for future exploration Currently, the evaluation of a patient with a positive sputum culture for NTM is costly and timeconsuming. Patients require further sputum specimens and often CXRs and CT scans to fully evaluate for the presence/absence of disease. When there is doubt these are often repeated over time. Smearpositive specimens create extra testing (DNA probes where available) to differentiate the pathology from tuberculosis, and where these tests are not available, many patients receive unnecessary treatment and public health management resources in the assumption they have tuberculosis, until mycobacterial cultures confirm otherwise. Better diagnostic tests that obviate the need for these costly investigations would significantly improve health care in this area. Respirology (2009) 14, 12–26 Serodiagnosis of MAC pulmonary disease using an enzyme immunoassay to assess antibody response to glycopeptidolipid has been shown to be promising, though validation in larger populations still appears warranted. The most recent of four papers published from Japan,104 consisted of a multicentre study, which evaluated this test in 70 patients with MAC pulmonary disease (19 with fibrocavitary disease, 35 with nodular bronchiectasis, 16 unclassifiable), 18 considered contaminated with MAC, 36 patients with pulmonary tuberculosis, 45 with other lung diseases and 76 healthy controls. In discriminating MAC pulmonary disease from the other patient groups—the test demonstrated 84.3% sensitivity and 100% specificity (using a cut-off level of 0.7 U/mL). Significantly higher levels were found in nodular bronchiectasis than in cavitary disease, but there was no difference between M. avium and M. intracellulare. There was a positive correlation between antibody levels and radiographic extent of disease in patients who had CT and serodiagnosis at the same time. Future studies are needed to verify the chosen cut-off point from this study, using larger samples of cases and controls that encompass multiple underlying lung diseases, along with patients from more diverse ethnic and racial groups and geographic areas. As mycobacteria are ubiquitous and of low virulence it is presumed that a host defect of immune regulation must be present for disease to occur, particularly in patients with the nodular-bronchiectatic form, who are largely non-smokers, with no predisposing conditions. Defects in the IFN-g and IL-12 receptor pathways have been reported in cases of disseminated NTM infection in young patients. Unfortunately, no similar defect has been found in patients with pulmonary NTM infection. Kwon et al.105 investigated the ability of peripheral blood mononuclear cells to produce proinflammatory cytokines such as IFN-g, tumour necrosis factor-a (TNF-a) and IL-12, and anti-inflammatory cytokines such as IL-10 in NTM patients and controls. They confirmed the findings of previous investigators106,107 that patients with NTM pulmonary diseases (both MAC and M. abscessus) produce less IFN-g, TNF-a and IL-12 than healthy controls. This opens up a possible therapeutic approach, by including exogenous cytokine replacement. Aerosolized IFN-g, as adjunctive therapy for MAC lung disease, appeared initially promising,108 but a randomized controlled trial of aerosolized IFN-g was halted early because of lack of efficacy.64 The efficacy of systemically administered cytokines is limited to studies in mice.109,110 However, further evaluation of immunotherapy of NTM lung diseases appears warranted. As NTM lung diseases are generally difficult to treat, new drugs are needed to advance therapy. Aside from moxifloxacin as discussed, linezolid, a oxazolidinone, has been shown to have good activities against many rapidly111,112 and slowly growing mycobacteria.113 However, there are major problems to consider when using linezolid in the longer term, such as anaemia and peripheral neuropathy. Tigecycline, a glycylcycline has been shown to have promising activity against RGM, especially for M. abscessus and M. © 2008 The Authors Journal compilation © 2008 Asian Pacific Society of Respirology Treatment of pulmonary NTM disease chelonae.114 TMC207, a diarylquinoline developed for treatment of tuberculosis, incidentally has been found to have activity against some NTM,115 and might have potential in treating diseases caused by these organisms. 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