Treatment of the Less Common Nontuberculous Mycobacterial Pulmonary Disease

Nontuberculous mycobacterial pulmonary disease caused by the less common nontuberculous mycobacteria have distinct features depending on the species. Diagnostic evaluation follows the established criteria for all nontuberculous mycobacteria, but with certain qualifications given species-specific and regional differences in pathogenicity. Clinicians should first institute nonpharmacologic management and evaluate clinical, radiologic, and microbiologic factors in the decision regarding antimycobacterial therapy. Treatment is challenging, and evidence-based recommendations are limited for most species. Drug susceptibility testing is used to help with regimen selection; however, this approach is imperfect given the uncertain correlation between in vitro activity and clinical response for most drugs.

The Other Nontuberculous Mycobacteria: Clinical Aspects of Lung Disease Caused by Less Common Slowly Growing Nontuberculous Mycobacteria Species

Slowly growing nontuberculous mycobacteria (NTM) comprise a diverse group of environmental organisms, many of which are important human pathogens. The most common and well-known member of this group is Mycobacterium avium, the leading cause of nontuberculous mycobacterial pulmonary disease (NTM-PD) globally. This review focuses on the less common, but notable, species of slowly growing NTM with respect to lung disease. To prepare this article, literature searches were performed using each species name as the key word. Society guidelines were consulted, and relevant articles also were identified through the reference lists of key articles. The specific organisms highlighted include Mycobacterium kansasii, Mycobacterium xenopi, Mycobacterium malmoense, Mycobacterium simiae, and Mycobacterium szulgai. Although these organisms are closely related, they have distinct epidemiologic features and behavior as pathogens. Therefore, the diagnosis and management of NTM-PD require a nuanced approach that takes into consideration the unique characteristics of each species. There is limited evidence to inform the optimal treatment of NTM-PD. Antimicrobial therapy is often challenging because of the presence of drug resistance and few antibiotic options. Regimen selection should generally be guided by drug susceptibility testing, although the correlation between clinical outcomes and in vitro susceptibility thresholds has not been defined for most species.

Efficacy and safety of fluoroquinolone-containing regimens in treating pulmonary Mycobacterium avium complex disease: A propensity score analysis

Background

Although combination therapy using clarithromycin, rifampicin, and ethambutol is recommended for patients with pulmonary Mycobacterium avium complex (MAC) disease, some patients do not tolerate it because of adverse effects or underlying diseases. The efficacy and safety of fluoroquinolone-containing combination regimens as an alternative remain uncertain. This study aimed to compare the efficacy and safety of fluoroquinolone-containing regimens with those of the standard regimens for treating pulmonary MAC disease.

Methods

We retrospectively included consecutive MAC patients who were treated in our hospital between January 2011 and May 2019. Patients treated with fluoroquinolone-containing regimens who had relapsed after treatment with standard regimens were excluded. A propensity score analysis was conducted to reduce selection bias, and the proportions of clinical improvement, defined by chest imaging findings and sputum conversion, were compared between the fluoroquinolone-containing regimen and standard regimen groups.

Results

We analyzed 28 patients who received fluoroquinolone-containing regimens and 46 who received the standard regimen. Fluoroquinolone-containing regimens were more likely selected for patients with cavitary lesions, diabetes mellitus, culture negativity, a low daily physical activity level, a decreased lymphocyte count and an increased CRP level. The propensity score was calculated using these variables (C-statistic of the area under the receiver operating characteristic curve of the propensity score: 0.807, p < 0.0001). The fluoroquinolone-containing regimens were significantly inferior to the standard regimen in clinical improvements (p = 0.002, Log-rank test) in the univariate analysis, but the significance was lost after adjusting for the propensity score (HR 0.553, 95% CI 0.285–1.074, p = 0.080). Six (21%) patients in the fluoroquinolone-containing regimen group and ten (22%) patients in the standard regimen group experienced low-grade adverse effects.

Conclusions

There was no significant difference in clinical improvement between these regimens after propensity score adjustment. A large-scale prospective study is required to validate these results.

Microbiologic Outcome of Interventions Against Mycobacterium avium Complex Pulmonary Disease: A Systematic Review

OBJECTIVE

Pulmonary disease (PD) caused by Mycobacterium avium complex (MAC) is increasing worldwide. We conducted a systematic review of studies that include microbiologic outcomes to evaluate current macrolide-based treatment regimens.

METHODS

We searched literature published before April 2017 by using the MEDLINE, Cochrane, and Embase databases. Risk of bias in randomized trials was assessed using the Cochrane tool.

RESULTS

We retrieved 333 citations and evaluated 42 studies including 2,748 patients: 18 studies were retrospective chart reviews, 18 were prospective, and six were randomized. The weighted average proportion of sputum culture conversions in macrolide-containing regimens after subtracting posttreatment microbiologic recurrences was 52.3% (95% CI, 44.7%-59.9%). Using the triple-drug regimens recommended by the American Thoracic Society (ATS) achieved treatment success in 61.4% (95% CI, 49.7%-72.5%), which further increased to 65.7% (95% CI, 53.3%-77.4%) when drugs were taken for at least 1 year by patients who were macrolide susceptible and had previously untreated MAC. The overall risk of bias was low in five of the six randomized trials. However, selective outcome reporting because of a posteriori exclusion of initially included patients (14.0%), uncompleted treatment (17.6%), and inconsistent use of outcome parameters (17 definitions of treatment success) hampered the comparison of nonrandomized trials.

CONCLUSIONS

To date, randomized studies on treatment outcome in patients with MAC PD are scarce. Long-term treatments with ATS-recommended regimens for patients who are macrolide susceptible are superior to other macrolide-based therapies. A standardized definition of treatment success and genotypic distinction between reinfection and relapse by means of pretreatment and posttreatment identification of MAC species in cases of microbiologic recurrences may help to optimize evaluation of treatment regimens in the future.

Pulmonary Cavity From Mycobacterium malmoense in an HIV-Infected Patient: Complicated by Bronchopleural Fistula

We present a case of M. malmoense and HIV co-infection complicated by aspergilloma leading to bronchopleural fistula with intractable pneumothorax and pleural aspergillosis, ultimately requiring surgical intervention. Treatment guidelines for M. malmoense are reviewed, literature regarding M. malmoense and HIV co-infection is reviewed, and the epidemiology of M. malmoense in North America is discussed.

Other Slow-Growing Nontuberculous Mycobacteria

The list of clinically important slow-growing nontuberculous mycobacteria (NTM) continues to expand as new species are identified and older ones are found to be pathogenic. Based on pigment production, the strains may be classified as photochromogenic, scotochromogenic, or unpigmented. Some of these organisms are not newly discovered but have heretofore been considered virtually nonpathogenic. Previously, many were regarded as contaminants when isolated from clinical specimens. Ubiquitous in nature, many NTM have been isolated from groundwater or tap water, soil, house dust, domestic and wild animals, and birds. Most infections result from inhalation or direct inoculation from environmental sources. They are not spread from person to person. The infections may be localized or disseminated. In most cases, the optimal regimen or duration of therapy has not been firmly established. The results of in vitro susceptibility testing may be used to select a therapeutic regimen. Many experts recommend clarithromycin with companion drugs such as rifampin and ethambutol for most, but not all, slowly growing species. Aminoglycosides, clofazimine, fluoroquinolones, linezolid, pyrazinamide, or trimethoprim-sulfamethoxazole also may be effective against some strains. Immunocompetent patients with clinically significant infections with NTM usually should receive 18 to 24 months of therapy. Infected immunocompromised patients, particularly those with disseminated infection, probably should receive therapy as long as their immune systems remain impaired. Some of the species discussed include Mycobacterium alsiense, M. celatum, M. gordonae, M. haemophilum, M. kyorinense, M. malmoense, M. simiae complex, M. szulgai, M. terrae complex, M. ulcerans, and M. xenopi.

Treatment of Non-Tuberculous Mycobacterial Lung Disease

Treatment of non-tuberculous mycobacterial lung disease (NTM-LD) is challenging for several reasons including the relative resistance of NTM to currently available drugs and the difficulty in tolerating prolonged treatment with multiple drugs. Yet-to-be-done, large, multicenter, prospective randomized studies to establish the best regimens will also be arduous because multiple NTM species are known to cause human lung disease, differences in virulence and response to treatment between different species and strains within a species will make randomization more difficult, the need to distinguish relapse from a new infection, and the difficulty in adhering to the prescribed treatment due to intolerance, toxicity, and/or drug-drug interactions, often necessitating modification of therapeutic regimens. Furthermore, the out-of-state resident status of many patients seen at the relatively few centers that care for large number of NTM-LD patients pose logistical issues in monitoring response to treatment. Thus, current treatment regimens for NTM-LD is largely based on small case series, retrospective analyses, and guidelines based on expert opinions. It has been nearly 10 years since the publication of a consensus guideline for the treatment of NTM-LD. This review is a summary of the available evidence on the treatment of the major NTM-LD until more definitive studies and guidelines become available.

Update on pulmonary disease due to non-tuberculous mycobacteria

Non-tuberculous mycobacteria (NTM) are emerging worldwide as significant causes of chronic pulmonary infection, posing a number of challenges for both clinicians and researchers. While a number of studies worldwide have described an increasing prevalence of NTM pulmonary disease over time, population-based data are relatively sparse and subject to ascertainment bias. Furthermore, the disease is geographically heterogeneous. While some species are commonly implicated worldwide (Mycobacterium avium complex, Mycobacterium abscessus), others (e.g., Mycobacterium malmoense, Mycobacterium xenopi) are regionally important. Thoracic computed tomography, microbiological testing with identification to the species level, and local epidemiology must all be taken into account to accurately diagnose NTM pulmonary disease. A diagnosis of NTM pulmonary disease does not necessarily imply that treatment is required; a patient-centered approach is essential. When treatment is required, multidrug therapy based on appropriate susceptibility testing for the species in question should be used. New diagnostic and therapeutic modalities are needed to optimize the management of these complicated infections.

Efficacy and safety of World Health Organization group 5 drugs for multidrug-resistant tuberculosis treatment

The efficacy and toxicity of several drugs now used to treat multidrug-resistant tuberculosis (MDR-TB) have not been fully evaluated.

We searched three databases for studies assessing efficacy in MDR-TB or safety during prolonged treatment of any mycobacterial infections, of drugs classified by the World Health Organization as having uncertain efficacy for MDR-TB (group 5).

We included 83 out of 4002 studies identified. Evidence was inadequate for meropenem, imipenem and terizidone. For MDR-TB treatment, clarithromycin had no efficacy in two studies (risk difference (RD) −0.13, 95% CI −0.40–0.14) and amoxicillin–clavulanate had no efficacy in two other studies (RD 0.07, 95% CI −0.21–0.35). The largest number of studies described prolonged use for treatment of non-tuberculous mycobacteria. Azithromycin was not associated with excess serious adverse events (SAEs). Clarithromycin was not associated with excess SAEs in eight controlled trials in HIV-infected patients (RD 0.00, 95% CI −0.02–0.02), nor in six uncontrolled studies in HIV-uninfected patients, whereas six uncontrolled studies in HIV-infected patients clarithromycin caused substantial SAEs (proportion 0.20, 95% CI 0.12–0.27).

For most group 5 drugs we found inadequate evidence of safety for prolonged use or for efficacy for MDR-TB, although macrolides appeared to be safe in prolonged use.

Human infections due to nontuberculous mycobacteria: the infectious diseases and clinical microbiology specialists' point of view

Nontuberculous mycobacteria (>150 species such as Mycobacterium avium, Mycobacterium kansasii, Mycobacterium chelonae and Mycobacterium abscessus) are opportunistic pathogens causing lung and extrarespiratory infections, beside M. ulcerans and M. marinum that are pathogens causing specific skin and soft tissue infections. Disseminated infections occur only in severe immunosuppressed conditions such as AIDS. The diagnosis is based on repeated isolations of the same mycobacterium associated with clinical and radiological signs, and the absence of tuberculosis. Precise species identification is obtained by molecular biology. Therapeutic antibiotic regimens differ with regard to the mycobacterial species that are involved. Prevention of iatrogenic infections relies on using sterile water in all injections, healthcare and cosmetic occupations. Future perspectives are to set effective antibiotic regimens tested in randomized therapeutic trials.

Drug treatment of pulmonary nontuberculous mycobacterial disease in HIV-negative patients: the evidence

Pulmonary disease (PD) caused by nontuberculous mycobacteria is an emerging infection mainly in countries where the incidence of tuberculosis is in decline. It affects an elderly population, often with underlying chronic lung diseases, but its epidemiology shows significant regional variation. Guidelines and recommendations for treatment of these infections exist, but build strongly on expert opinion, as very few good quality clinical trials have been performed in this field. Only for the most frequent causative agents, the Mycobacterium avium complex, Mycobacterium kansasii and Mycobacterium abscessus, a reasonable number of trials and case series is now available. For the less frequent causative agents of pulmonary nontuberculous mycobacterial (NTM) disease (Mycobacterium xenopi, Mycobacterium malmoense, Mycobacterium fortuitum, Mycobacterium chelonae) data is mostly limited to a few very small case series. Within this review, we have collected and combined evidence from all available trials and case series. From the data of these trials and case series, we reconstruct a more evidence-based overview of possible drug treatment regimens and their outcomes.

Mycobacterium intracellulare Pleurisy Identified on Liquid Cultures of the Pleural Fluid and Pleural Biopsy

Pleural effusion is a rare complication in non-tuberculous mycobacterial infection. We report a case of Mycobacterium intracellulare pleuritis with idiopathic pulmonary fibrosis in a 69-year-old man presenting with dyspnea. Pleural effusion revealed lymphocyte dominant exudate. M. intracellulare was identified using a polymerase chain reaction-restriction fragment length polymorphism method and liquid cultures of pleural effusion and pleural biopsy. After combination therapy for M. intracellulare pulmonary disease, the patient was clinically well at a 1-month follow-up.

Antimicrobial susceptibility testing, drug resistance mechanisms, and therapy of infections with nontuberculous mycobacteria

Within the past 10 years, treatment and diagnostic guidelines for nontuberculous mycobacteria have been recommended by the American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA). Moreover, the Clinical and Laboratory Standards Institute (CLSI) has published and recently (in 2011) updated recommendations including suggested antimicrobial and susceptibility breakpoints. The CLSI has also recommended the broth microdilution method as the gold standard for laboratories performing antimicrobial susceptibility testing of nontuberculous mycobacteria. This article reviews the laboratory, diagnostic, and treatment guidelines together with established and probable drug resistance mechanisms of the nontuberculous mycobacteria.

Aging, COPD, and other risk factors do not explain the increased prevalence of pulmonary Mycobacterium avium complex in Ontario

BACKGROUND

The cause of observed increases in pulmonary Mycobacterium avium complex (pMAC) isolation and disease is unexplained. To explore possible causes of the increase in pMAC isolation and disease prevalence in Ontario, Canada, we studied age and other population-level risk factors.

METHODS

We determined age and sex of patients with pMAC disease between 2003 and 2008. We then estimated whether the potential effect of population aging and changes in prevalence of HIV infection, solid organ transplant, COPD, and tumor necrosis factor-α (TNF-α) inhibition have contributed to the observed increase in pMAC disease.

RESULTS

During 2003 to 2008, pMAC isolation and disease prevalence (per 100,000) both increased (8.44 to 12.62 and 4.35 to 6.81, respectively). The total number of cases of disease increased by 348 (2.46 per 100,000). Based on actual contemporary population changes, aging could explain 70 additional cases (increase of 0.57 per 100,000). The increase in self-reported COPD prevalence could potentially explain 11 (95% CI, 0-42) additional cases (increase of 0.09 per 100,000 [95% CI, 0-0.34 per 100,000]). HIV infection, solid organ transplant, and TNF-α inhibition combined could potentially explain no more than 73 additional cases (increase of 0.60 per 100,000).

CONCLUSIONS

Although population aging appears to be a major risk factor, the increase in pMAC disease in Ontario could be only partly explained by aging, increases in COPD, HIV, solid organ transplantation, and TNF-α inhibition therapy. The increase in pMAC is likely multifactorial and may be affected by environmental or pathogen factors not addressed in this study.

Management of pulmonary nontuberculous mycobacterial disease

Nontuberculous mycobacteria are increasingly recognized as causes of chronic pulmonary disease. Treatment decisions are guided by the clinical presentation, microbial isolate, and condition of the patient. Management may include antibiotic therapy, surgical resection, or observation. Definitive trials are lacking, and optimum management remains uncertain.