The tolerability of linezolid in the treatment of nontuberculous mycobacterial disease

Recent advances in immunopathogenesis and clinical practice: mastering the challenge-managing of non-tuberculous mycobacteria

Non-tuberculous mycobacteria (NTM) are widespread environmental pathogens that can lead to significant disease burden, particularly in immunocompromised individuals, but also in those with a normal immune system. The global incidence of NTM is increasing rapidly, with Mycobacterium avium complex (MAC) being one of the most common types. The immunopathogenesis of the MAC involves a complex interaction between the bacteria and the host immune system. MAC survives and replicates within macrophages by preventing the fusion of phagosomes and lysosomes. The mycobacteria can neutralize reactive oxygen and nitrogen species produced by the macrophages through their own enzymes. Additionally, MAC modulates cytokine production, allowing it to suppress or regulate the immune response. Diagnosing MAC infections can be challenging, and the effectiveness of available treatments may be limited due to MAC's unpredictable resistance to various antimycobacterial drugs in different regions. Treating MAC infection requires a collaborative approach involving different healthcare professionals and ensuring patient compliance. This review aims to shed light on the complexities of MAC infection treatment, discussing the challenges of MAC infection diagnosis, pharmacological considerations, such as drug regimens, drug monitoring, drug interactions, and the crucial role of a multidisciplinary healthcare team in achieving the best possible treatment outcomes for patients.

Benchmarking antimicrobial use to antimicrobial resistance: a comparative study of two hospitals using current National Healthcare Safety Network (NHSN) metrics

OBJECTIVE

We aimed to determine whether benchmarking antimicrobial use (AU) to antimicrobial resistance (AR) using select AU/AR ratios is more informative than AU metrics in isolation.

DESIGN

We retrospectively measured AU (antimicrobial therapy days per 1,000 days present) and AU/AR ratios (specific antimicrobial therapy days per corresponding AR event) in two hospitals during 2020 through 2022. We then had antimicrobial stewardship committee members evaluate each AU and corresponding AU/AR value and indicate whether they believed it represented potential overuse, appropriate use, or potential underuse of the antimicrobials, or whether they could not provide an assessment.

SETTING

Two acute-care hospitals.

PATIENTS

Hospitalized patients.

RESULTS

In semi-annual facility-wide analyses, echinocandins had a median AU/AR ratio of 658.5 therapy days per fluconazole-resistant Candida event in Hospital A, IV vancomycin had a median AU/AR ratio of 114.9 and 108.2 therapy days per methicillin-resistant Staphylococcus aureus event in Hospital A and B, respectively, and linezolid had a median AU/AR ratio of 33.8 and 88.0 therapy days per vancomycin-resistant Enterococcus event in Hospital A and B, respectively. When AU and AU/AR values were evaluated by stewardship committees, more respondents were able to assess antimicrobial use based on AU/AR values compared to AU values. Based on AU/AR ratios, most respondents identified potential overuse of echinocandins and IV vancomycin in Hospital A, and potential overuse of linezolid and IV vancomycin in Hospital B.

CONCLUSION

Select AU/AR ratios provided informative metrics to antimicrobial stewardship personnel, which can be used to motivate audits of antimicrobial administration to determine appropriateness.

Treatment outcomes in NTM-PD in a high TB burden context

BACKGROUND

Non-tuberculous mycobacterial (NTM) pulmonary disease (PD) is a significant concern in China, compounding the existing burden of TB. This review aims to summarise the treatment outcomes for NTM-PD in China.

METHODS

We reviewed the evidence on NTM-PD, including treatment regimens and clinical outcomes, from 17 studies identified through screening of three Chinese biomedical databases.

RESULTS

Antimicrobial treatment showed a microbiological cure rate ranging from 17.2% to 60.0% in studies with ≥50 NTM-PD patients, with lower rates observed among older and malnourished patients. The Mycobacterium chelonae abscessus group (MC-AG) and Mycobacterium avium-intracellulare complex (MAC) were the most prevalent NTM species in China. Higher microbiological cure rates were seen in MAC PD compared with MC-AG PD. The addition of cefoxitin and linezolid improved culture conversion rates in MC-AG-infected patients. One study (n = 24) demonstrated that resecting lesions and chemotherapy led to more favourable clinical outcomes.

CONCLUSION

Treatment regimens recommended in Chinese guidelines yielded poor-to-moderate outcomes for NTM-PD in China, highlighting the need for further research into alternative antimicrobial treatments to improve efficacy.

In vitro effects of the new oral β-lactamase inhibitor xeruborbactam in combination with oral β-lactams against clinical Mycobacterium abscessus isolates

Non-tuberculosis mycobacteria (NTM), particularly Mycobacterium abscessus subsp. abscessus (M. abscessus), are increasingly being recognized as etiological agents of NTM pulmonary disease. However, treatment options for M. abscessus are limited owing to their natural resistance to most antibiotics, including β-lactams. M. abscessus produces a class A β-lactamase, whose activity is inhibited by cyclic boronic acid β-lactamase inhibitors. We aimed to evaluate the in vitro effects of xeruborbactam, a cyclic boronic acid β-lactamase inhibitor, against M. abscessus when combined with five β-lactams (amoxicillin, tebipenem, cefdinir, cefuroxime, and cefoxitin). The drug susceptibilities of 43 M. abscessus clinical isolates obtained from 43 patients between August 2005 and May 2014 were tested. The MIC results for each β-lactam with or without 4 µg/mL xeruborbactam were examined. Xeruborbactam lowered the MIC90 values of tebipenem, amoxicillin, cefuroxime, and cefdinir by 5, ≥4, 3, and 3 dilutions, respectively. The MIC90 values of cefoxitin without xeruborbactam were 32 µg/mL and did not change upon the addition of xeruborbactam. The lowest MIC90 value was obtained for tebipenem with xeruborbactam. Almost all isolates had an MIC of 4 µg/mL; one isolate had an MIC of 2 µg/mL. With respect to the susceptibility to the same family drug, the number of susceptible isolates increased from 1/43 (2%) to 43/43 (100%) for tebipenem with xeruborbactam. Combining tebipenem and xeruborbactam could be considered an effective all-oral regimen that benefits outpatient treatment of M. abscessus pulmonary disease.

IMPORTANCE

Mycobacterium abscessus subsp. abscessus (M. abscessus) disease is treated in two phases; injectable drugs for initial followed by others for continuation. There is a need to develop all-oral treatment methods for M. abscessus infection, especially in the continuation phase. However, treatment options for M. abscessus are limited owing to their natural resistance to most antibiotics. This is the first report to evaluate the in vitro effects of xeruborbactam, a cyclic boronic acid β-lactamase inhibitor capable of inhibiting the class A β-lactamase produced by M. abscessus, against 43 M. abscessus clinical isolates when combined with five β-lactam antibiotics. Xeruborbactam lowered the MIC90 values of tebipenem by five dilutions, and the number of susceptible isolates increased from 1/43 (2%) to 43/43 (100%). We showed that the tebipenem-xeruborbactam combination might be of interest to explore further as a potentially effective oral regimen for outpatient treatment of M. abscessus pulmonary disease.

Drugs for treating infections caused by non-tubercular mycobacteria: a narrative review from the study group on mycobacteria of the Italian Society of Infectious Diseases and Tropical Medicine

BACKGROUND

Non-tuberculous mycobacteria (NTM) are generally free-living organism, widely distributed in the environment, with sporadic potential to infect. In recent years, there has been a significant increase in the global incidence of NTM-related disease, spanning across all continents and an increased mortality after the diagnosis has been reported. The decisions on whether to treat or not and which drugs to use are complex and require a multidisciplinary approach as well as patients' involvement in the decision process.

METHODS AND RESULTS

This review aims at describing the drugs used for treating NTM-associated diseases emphasizing the efficacy, tolerability, optimization strategies as well as possible drugs that might be used in case of intolerance or resistance. We also reviewed data on newer compounds highlighting the lack of randomised clinical trials for many drugs but also encouraging preliminary data for others. We also focused on non-pharmacological interventions that need to be adopted during care of individuals with NTM-associated diseases CONCLUSIONS: Despite insufficient efficacy and poor tolerability this review emphasizes the improvement in patients' care and the needs for future studies in the field of anti-NTM treatments.

[A pharmacologic approach to treatment of Mycobacterium abscessus pulmonary disease]

Mycobacterium abscessus is a fast-growing non-tuberculous mycobacteria complex causing pulmonary infections, comprising the subspecies abscessus, massiliense and bolletii. Differences are based predominantly on natural inducible macrolide resistance, active in most Mycobacterium abscessus spp abscessus species and in Mycobacterium abscessus spp bolletii but inactive in Mycobacterium abscessus spp massiliense. Therapy consists in long-term treatment, combining multiple antibiotics. Prognosis is poor, as only 40% of patients experience cure. Pharmacodynamic and pharmacokinetic data on M. abscessus have recently been published, showing that therapy ineffectiveness might be explained by intrinsic bacterial resistance (macrolides…) and by the unfavorable pharmacokinetics of the recommended antibiotics. Other molecules and inhaled antibiotics are promising.

Effectiveness and safety of regimens containing linezolid for treatment of Mycobacterium abscessus pulmonary Disease

OBJECTIVE

To evaluate the effectiveness and safety of linezolid-containing regimens for treatment of M. abscessus pulmonary disease.

METHODS

The records of 336 patients with M. abscessus pulmonary disease who were admitted to Shanghai Pulmonary Hospital from January 2018 to December 2020 were retrospectively analyzed. A total of 164 patients received a linezolid-containing regimen and 172 controls did not. The effectiveness, safety, antibiotic susceptibility profiles, outcomes, culture conversion, cavity closure, and adverse reactions were compared in these two groups.

RESULTS

The two groups had similar treatment success (56.1% vs. 48.8%; P > 0.05), but treatment duration was shorter in the linezolid group (16.0 months [inter-quartile ranges, IQR: 15.0-17.0] vs. 18.0 months [IQR: 16.0-18.0]; P < 0.01). The rates of sputum culture conversion were similar (53.7% vs. 46.5%, P > 0.05), but time to conversion was shorter in the linezolid group (3.5 months [IQR: 2.5-4.4] vs. 5.5 months [IQR: 4.0-6.8]; P < 0.01). The linezolid group had a higher rate of cavity closure (55.2% vs. 28.6%, P < 0.05) and a shorter time to cavity closure (3.5 months [IQR: 2.5-4.4] vs. 5.5 months [IQR: 4.0-6.8]; P < 0.01). Anemia and peripheral neuropathy were more common in the linezolid group (17.7% vs. 1.7%, P < 0.01; 12.8% vs. 0.6%, P < 0.01).

CONCLUSIONS

The linezolid and control groups had similar treatment success rates. The linezolid group had a shorter treatment duration, shorter time to sputum culture conversion, and higher rate and shorter time to lung cavity closure. More patients receiving linezolid developed anemia and peripheral neuropathy.

Treatment Approaches to Mycobacterium abscessus Pulmonary Disease

Mycobacterium abscessus pulmonary disease is highly antibiotic-resistant, and the current armamentarium of antibiotics yields poor treatment outcomes with significant drug toxicity. Macrolide susceptibility is a key prognostic factor. Optimal drug combinations, duration of therapy, and management of refractory disease are unknown. Surgical resection, performed at centers with experience in surgical management of nontuberculous mycobacterial pulmonary disease, may produce favorable outcomes in select patients. Multiple emerging therapeutic candidates hold promise for more efficacious and tolerable treatment options.

Treatment of Mycobacterium avium Complex Pulmonary Disease: When Should I Treat and What Therapy Should I Start?

Treatment of M avium pulmonary disease requires a three-drug, macrolide-based regimen that is administered for 12 months beyond culture conversion. The regimen can be administered 3 days a week in non-cavitary, nodular bronchiectatic disease but should be given daily when cavitary disease is present. For treatment refractory disease, amikacin liposome inhalation suspension is added to the regimen. Parenteral amikacin or streptomycin should be administered in the setting of extensive radiographic involvement or macrolide resistance. Recurrence of disease is common and often due to reinfection. Novel and repurposed agents are being evaluated in clinical trials.

Intracellular and in vivo activities of oxazolidinone drugs against Mycobacterium avium complex infection

The prevalence of Mycobacterium avium complex-pulmonary disease (MAC-PD) has become a growing concern worldwide, and current treatments involving macrolides (clarithromycin [CLR] or azithromycin), ethambutol, and rifampicin have limited success, highlighting the need for better therapeutic strategies. Recently, oxazolidinone drugs have been identified as novel anti-tuberculosis drugs effective against drug-resistant M. tuberculosis. However, the effects of these drugs against MAC are still controversial due to limited data. Here, we first evaluated the intracellular anti-MAC activities of two oxazolidinone drugs, linezolid (LZD) and delpazolid (DZD), against 10 macrolide-susceptible MAC strains and one macrolide-resistant M. avium strain in murine bone marrow-derived macrophages (BMDMs) and found that both drugs demonstrated similar potential. The synergistic efficacies with CLR were then determined in a chronic progressive MAC-PD murine model by initiating a 4-week treatment at 8 weeks post-infection. Upon assessment of bacterial burdens and inflamed lesions, oxazolidinone drugs exhibited no anti-MAC effect, and there was no significant difference in the synergistic effect of CLR between LZD and DZD. These findings suggest that oxazolidinone drugs inhibit intracellular bacterial growth, even against macrolide-resistant MAC, but their clinical application requires further consideration.

In Vitro Synergistic Effects of Omadacycline with Other Antimicrobial Agents against Mycobacterium abscessus

The clinical importance of Mycobacterium abscessus species (MABS) infections has been increasing. However, the standard treatment regimens recommended in the current guidelines often result in unfavorable outcomes. Therefore, we investigated the in vitro activity of omadacycline (OMC), a novel tetracycline, against MABS to explore its potential as a novel therapeutic option. The drug susceptibilities of 40 Mycobacterium abscessus subsp. abscessus (Mab) clinical strains obtained from the sputum of 40 patients from January 2005 to May 2014 were investigated. The MIC results for OMC, amikacin (AMK), clarithromycin (CLR), clofazimine (CLO), imipenem (IPM), rifabutin (RFB), and tedizolid (TZD) alone and their combined effects (with OMC) were examined using the checkerboard method. Additionally, we studied the differences in the effectiveness of the antibiotic combinations based on the colony morphotype of Mab. The MIC50 and MIC90 of OMC alone were 2 and 4 μg/mL, respectively. The combinations of OMC with AMK, CLR, CLO, IPM, RFB, and TZD showed synergy against 17.5%, 75.8%, 25.0%, 21.1%, 76.9%, and 34.4% of the strains, respectively. Additionally, OMC combined with CLO (47.1% versus 9.5%, P = 0.023) or TZD (60.0% versus 12.5%, P = 0.009) showed significantly higher synergy against strains with rough morphotypes than those with smooth morphotypes. In conclusion, the checkerboard analyses revealed that the synergistic effects of OMC were observed most frequently with RFB, followed by CLR, TZD, CLO, IPM, and AMK. Furthermore, OMC tended to be more effective against rough-morphotype Mab strains.

ISPD Catheter-related Infection Recommendations: 2023 Update

Peritoneal dialysis (PD) catheter-related infections are important risk factors for catheter loss and peritonitis. The 2023 updated recommendations have revised and clarified definitions and classifications of exit site infection and tunnel infection. A new target for the overall exit site infection rate should be no more than 0.40 episodes per year at risk. The recommendation about topical antibiotic cream or ointment to catheter exit site has been downgraded. New recommendations include clarified suggestion of exit site dressing cover and updated antibiotic treatment duration with emphasis on early clinical monitoring to ascertain duration of therapy. In addition to catheter removal and reinsertion, other catheter interventions including external cuff removal or shaving, and exit site relocation are suggested.

Contemporary Pharmacotherapies for Nontuberculosis Mycobacterial Infections: A Narrative Review

Nontuberculous mycobacteria (NTM) are a group of atypical bacteria that may cause a spectrum of clinical manifestations, including pulmonary, musculoskeletal, skin and soft tissue, and cardiac infections. Antimycobacterial medication regimens for NTM infections require multiple agents with prolonged treatment courses and are often associated with poor tolerance in patients and suboptimal clinical outcomes. This review summarizes NTM pharmacotherapy, including treatment concepts, preferred medication regimens according to NTM species and site of infection, and emerging treatment methods for difficult-to-treat species.

In vitro Susceptibility of Nontuberculous Mycobacteria to Tedizolid

Objective

Nontuberculous mycobacteria (NTM) can cause pulmonary and extrapulmonary diseases. Tedizolid (TZD) is a new oxazolidinone with in vitro activity against NTM such as Mycobacterium avium complex (MAC), Mycobacterium fortuitum, and Mycobacterium abscessus complex. The aim of this study was to evaluate the TZD susceptibility profiles of clinical isolates of NTM.

Methods

The microdilution method was used to identify the minimum inhibitory concentration (MIC) of TZD and linezolid (LZD) for 133 clinical NTM isolates. Broth microdilution chequerboard assays were used to investigate the synergistic effects of TZD and three antibiotics on two reference isolates and eleven clinical isolates of NTM.

Results

The TZD MIC₅₀ and MIC₉₀ for M. abscessus complex were 2 and 4 μg/mL, 16 and >32 μg/mL for MAC, respectively. TZD exhibited lower MICs than that of LZD for most NTM, which were positively correlated. Due to the high MIC values of TZD against MAC, it is necessary to conduct drug sensitivity tests before TZD administration. TZD-clarithromycin combination had synergistic response on M. abscessus complex in 3 of the 8 isolates, which lasted only 3-5 days. TZD-cefoxitin had synergistic effect against all five M. fortuitum isolates.

Conclusion

Our study demonstrates that TZD had greater in vitro potency than LZD, and synergy studies suggested that TZD may be an important component of multi-drug treatment regimen.

Nontuberculous Mycobacterial Resistance to Antibiotics and Disinfectants: Challenges Still Ahead

The mortality incidence from nontuberculous mycobacteria (NTM) infections has been steadily developing globally. These bacterial agents were once thought to be innocent environmental saprophytic that are only dangerous to patients with defective lungs or the immunosuppressed. Nevertheless, the emergence of highly resistant NTM to different antibiotics and disinfectants increased the importance of these agents in the health system. Currently, NTM frequently infect seemingly immunocompetent individuals at rising rates. This is of concern as the resistant NTM are difficult to control and treat. The details behind this NTM development are only beginning to be clarified. The current study will provide an overview of the most important NTM resistance mechanisms to not only antibiotics but also the most commonly used disinfectants. Such evaluations can open new doors to improving control strategies and reducing the risk of NTM infection. Moreover, further studies are crucial to uncover this association.

Minimum Inhibitory Concentrations before and after Antibacterial Treatment in Patients with Mycobacterium abscessus Pulmonary Disease

The clinical importance of Mycobacterium abscessus (MABS) pulmonary disease has been increasing. However, there is still a lack of information about MIC distribution patterns and changes in clinical practice settings. The MIC results of rapidly growing mycobacteria isolated from 92 patients with nontuberculous mycobacterial pulmonary disease diagnosed from May 2019 to March 2021 were retrospectively analyzed. Most of the patients (86 patients; 93.5%) were infected with MABS; 46 with Mycobacterium abscessus subsp. abscessus (Mab), and 40 with Mycobacterium abscessus subsp. massiliense (Mma). Significant differences in susceptibility to clarithromycin (15.2% versus 80.0%, P < 0.001) and azithromycin (8.7% versus 62.5%, P < 0.001) were observed between Mab and Mma. Most isolates were susceptible to amikacin (80; 93.0%), and over half were susceptible to linezolid (48; 55.8%). Only one-quarter of isolates (22, 25.6%) were susceptible to imipenem, while more than half (56; 65.1%) had intermediate susceptibility. Fifty-one isolates (59.3%) had MIC values of less than 1 μg/mL for sitafloxacin, which were significantly higher than isolates for moxifloxacin (5; 5.8%), especially in Mab. Sixty-five (75.6%) isolates had MICs of less than 0.5 μg/mL to clofazimine. Two patients showed obvious MIC result changes: from susceptible to resistant to clarithromycin and from resistant to susceptible to amikacin and imipenem. In conclusion, MABS isolates were relatively susceptible to amikacin and linezolid, and clarithromycin and azithromycin were especially effective against Mma. In addition, sitafloxacin and clofazimine had low MICs and might be effective treatment agents. IMPORTANCE The MICs of isolates from 86 patients with Mycobacterium abscessus (MABS); 46 with Mycobacterium abscessus subsp. abscessus (Mab), and 40 with Mycobacterium abscessus subsp. massiliense (Mma) were retrospectively analyzed. The main findings are as follows: (i) Mma were significantly more susceptible to clarithromycin and azithromycin than Mab, and both subspecies tended to be more susceptible to clarithromycin than azithromycin. (ii) Most isolates were susceptible to amikacin (93.0%), and over half to linezolid (55.8%). (iii) Fifty-one isolates (59.3%) had MIC values of less than 1 μg/mL for sitafloxacin, and 65 (75.6%) had less than 0.5 μg/mL for clofazimine, which seems worth clinical investigating. (iv) Among nine cases analyzed chronological changes, only two patients showed obvious MIC result changes even after the long-term multidrug treatment. The present study revealed MICs of MABS clinical isolates before and after treatment in clinical settings, which could help develop future MABS treatments strategies.

Management of Multidrug Resistant Infections in Lung Transplant Recipients with Cystic Fibrosis

Cystic fibrosis (CF) is an inherited multisystem disease characterised by bronchiectasis and chronic respiratory infections which eventually cause end stage lung disease. Lung transplantation (LTx) is a well-established treatment option for patients with CF-associated lung disease, improving survival and quality of life. Navigating recurrent infections in the setting of LTx is often difficult, where immune suppression must be balanced against the constant threat of infection. Sepsis/infections are one of the major contributors to post-LTx mortality and multiresistant organisms (eg, Burkholderia cepacia complex, Mycobacterium abscessus complex, Scedosporium spp. and Lomentospora spp.) pose a significant threat to survival. This review will summarize current and novel therapies to assist with the management of multiresistant bacterial, mycobacterial, viral and fungal infections which threaten the CF LTx cohort.

Pharmacotherapy for nontuberculous mycobacterial pulmonary disease

DISCLAIMER

In an effort to expedite the publication of articles , AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

To provide an updated review of the diagnosis and pharmacotherapy of nontuberculous mycobacteria pulmonary disease (NTM-PD) and summarize guideline recommendations for an interdisciplinary treatment approach.

SUMMARY

A systemic approach was taken in which all articles in English in MEDLINE and PubMed were reviewed. DAILYMED was used to assess drug package inserts. Analysis of NTM treatment guidelines is summarized in the article with a focus on medications, dosing, interactions, and medication monitoring.

CONCLUSION

It is critical to manage patients with NTM with a multidisciplinary team approach. Treatment is prolonged and expensive, and the potential for drug toxicity, adverse effects, and drug interactions requires monitoring. Clinical pharmacists play a role in the management of NTM.

Nontuberculous mycobacterial lung disease caused by Mycobacterium avium complex - disease burden, unmet needs, and advances in treatment developments

INTRODUCTION

Nontuberculous mycobacterial (NTM) lung disease (LD) is the most common clinical manifestation of NTM infection and is a growing health concern. Up to 85% of NTM-LD cases are caused by Mycobacterium avium complex (MAC). Increased awareness of NTM-LD caused by MAC is needed as patients with this disease experience substantial burden and unmet treatment needs.

AREAS COVERED

This review provides clinicians and regulatory and healthcare decision makers an overview of the clinical, economic, and humanistic burden of NTM-LD and the unmet treatment needs faced by patients and clinicians. The review focuses on NTM-LD caused by MAC. A summary of the 2020 NTM guidelines specifically for MAC-LD and an overview of novel treatment options, including amikacin liposome inhalation suspension (ALIS) as the first approved therapy for refractory MAC-LD, and investigational drugs in testing phase are provided.

EXPERT OPINION

Key advancements in NTM-LD management include recent updates to clinical practice guidelines, approval of ALIS for the treatment of refractory MAC-LD, and ongoing clinical trials of investigational treatments. Yet opportunities still exist to improve patient outcomes, including development of better screening tools, such as reliable and responsive biomarkers to help identify high-risk patients, and addressing unmet treatment needs.

Prolonged tedizolid use in cutaneous non-tuberculous mycobacterial infection

Cutaneous non-tuberculous mycobacterial (NTM) infections are an emerging infectious disease and require a protracted course of combination antibiotics. Antimicrobial choice is limited by resistance and toxicity. Tedizolid is a new oxazolidinone antibiotic with in vitro activity against some NTM, but its use in the management of extrapulmonary NTM has not been described. We report on the utility of prolonged tedizolid use (8 months), after linezolid intolerance, in combination therapy in a case of difficult Mycobacterium chelonae cutaneous infection. Although tedizolid contributed to clinical remission, it may have also contributed to a multifocal peripheral neuropathy. Its efficacy may also have been limited by continued immunosuppression, with evidence to suggest disease relapse or treatment failure after completion of combination therapy. Tedizolid can be considered, with caution, in combination therapy for difficult cases of cutaneous NTM infection.

Nontuberculous Mycobacteria

Nontuberculous mycobacteria (NTM) are ubiquitous in the environment and 193 species of NTM have been discovered thus far. NTM species vary in virulence from benign environmental organisms to difficult-to-treat human pathogens. Pulmonary infections remain the most common manifestation of NTM disease in humans and bronchiectasis continues to be a major risk factor for NTM pulmonary disease (NTM PD). This article will provide a useful introduction and framework for clinicians involved in the management of bronchiectasis and NTM. It includes an overview of the epidemiology, pathogenesis, diagnosis, and management of NTM PD. We will address the challenges faced in the diagnosis of NTM PD and the importance of subspeciation in guiding treatment and follow-up, especially in Mycobacterium abscessus infections. The treatment of both Mycobacterium avium complex and M. abscessus, the two most common NTM species known to cause disease, will be discussed in detail. Elements of the recent ATS/ERS/ESCMID/IDSA NTM guidelines published in 2020 will also be reviewed.

Is there a role for tedizolid in the treatment of non-tuberculous mycobacterial disease?

Background

Pulmonary infections caused by non-tuberculous mycobacteria (NTM) are hard to treat and have low cure rates despite intensive multidrug therapy.

Objectives

To assess the feasibility of tedizolid, a new oxazolidinone, for the treatment of Mycobacterium avium and Mycobacterium abscessus.

Methods

We determined MICs of tedizolid for 113 isolates of NTM. Synergy with key antimycobacterial drugs was assessed using the chequerboard method and calculation of the FIC index (FICI). We performed time–kill kinetics assays of tedizolid alone and combined with amikacin for M. abscessus and with ethambutol for M. avium. Human macrophages were infected with M. abscessus and M. avium and subsequently treated with tedizolid; intracellular and extracellular cfu were quantified over time.

Results

NTM isolates generally had a lower MIC of tedizolid than of linezolid. FICIs were lowest between tedizolid and amikacin for M. abscessus (FICI = 0.75) and between tedizolid and ethambutol for M. avium (FICI = 0.72). Clarithromycin and tedizolid showed initial synergy, which was abrogated by erm(41)-induced macrolide resistance (FICI = 0.53). Tedizolid had a weak bacteriostatic effect on M. abscessus and combination with amikacin slightly prolonged its effect. Tedizolid had concentration-dependent activity against M. avium and its efficacy was enhanced by ethambutol. Both combinations had a concentration-dependent synergistic effect. Tedizolid could inhibit the intracellular bacterial population of both M. avium and M. abscessus.

Conclusions

Tedizolid should be further investigated in pharmacodynamic studies and clinical trials for M. avium complex pulmonary disease. It is less active against M. abscessus, but still promising.

A review of current and promising nontuberculous mycobacteria antibiotics

Nontuberculous mycobacteria infections are a growing concern, and their incidence has been increasing worldwide in recent years. Current treatments are not necessarily useful because many were initially designed to work against other bacteria, such as Mycobacterium tuberculosis. In addition, inadequate treatment means that resistant strains are increasingly appearing, particularly for Mycobacterium abscessus, one of the most virulent nontuberculous mycobacteria. There is an urgent need to develop new antibiotics specifically directed against these nontuberculous mycobacteria. To help in this fight against the emergence of these pathogens, this review describes the most promising heterocyclic antibiotics under development, with particular attention paid to their structure-activity relationships.

Approach to the diagnosis and treatment of non-tuberculous mycobacterial disease

Non-tuberculous mycobacteria (NTM) is a collective name given to a group of more than 190 species of Mycobacterium. The clinical presentation for most NTM infections is non-specific, often resulting in delayed diagnosis. Further complicating matters is that NTM organisms can be difficult to isolate. Medications used to treat NTM infection can be difficult for patients to tolerate, and prolonged courses of anti-mycobacterial therapy are often required for adequate suppression or eradication. Herein, we review different NTM syndromes, appropriate diagnostic tests, and treatment regimens.

A tale of two images: From mycobacterium avium complex-lung disease (MAC-LD) to mycobacterium avium complex-pleural disease

The typical radiographic presentation for Mycobacterium avium complex lung disease (MAC-LD) is either nodular bronchiectasis or cavitary lung disease. The former is seen most commonly in middle-aged or elderly Caucasian females with the characteristic asthenic phenotype, and the latter in middle-aged male smokers with COPD. We present the case of a young, otherwise healthy woman, with no significant risk factors, who was incidentally found to have MAC-LD with associated bronchiectasis. The patient's treatment and clinical course over a period of 5 years was marred by erratic follow up, intermittent treatment and poor adherence to guideline-based antibiotic therapy. Over this period of time, the patient developed significant worsening of her MAC-LD, macrolide resistance and failure to thrive. Upon presentation 5 years after her initial diagnosis, she had developed MAC-Pleural Disease with an empyema and broncho-pleural fistula. This case illustrates the progression of MAC-LD from nodular bronchiectasis to cavitary disease and pleural involvement leading to clinical deterioration. It highlights challenges related to short and long term management of macrolide resistant MAC-LD and the importance and need for surgical intervention and drainage procedures in patient with MAC-Pleural Disease.

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Non-Adherence to comprehensive guideline based therapy contribute to disease progression in patients with MAC-LD.

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Untreated or erratically treated MAC-LD can progress to MAC-PD in immunocompetent hosts with no underlying risk factors.

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A combined medical and surgical approach is essential in managing patients with MAC-PD.

Tedizolid vs Linezolid for the Treatment of Nontuberculous Mycobacteria Infections in Solid Organ Transplant Recipients

Background

Treatment options for nontuberculous mycobacteria (NTM) infections are limited by the pathogen's intrinsic resistance profile and toxicities. Tedizolid and linezolid display in vitro activity against NTM species. However, safety data and treatment outcomes are limited in the solid organ transplant (SOT) population.

Methods

This was a single-center retrospective cohort study of adult SOT recipients receiving linezolid or tedizolid for an NTM infection from January 1, 2010, to August 31, 2019. The primary outcome compared the hematologic safety profiles of tedizolid vs linezolid. We also described nonhematological adverse drug events (ADEs) and therapy discontinuation rates. In an exploratory analysis, we assessed symptomatic microbiologic and clinical outcomes in those receiving tedizolid or linezolid for at least 4 weeks.

Results

Twenty-four patients were included (15 tedizolid, 9 linezolid). No differences were identified comparing the effects of tedizolid vs linezolid on platelet counts, absolute neutrophil counts (ANCs), and hemoglobin over 7 weeks using mixed-effects analysis of variance models. ANC was significantly decreased in both groups after 7 weeks of therapy (P = .04). Approximately 20% of patients in each arm discontinued therapy due to an ADE. Seven of 12 (58%) and 2 of 3 (67%) patients were cured or clinically cured with tedizolid- and linezolid-containing regimens, respectively.

Conclusions

This study suggests no significant safety benefit of tedizolid over linezolid for the treatment of NTM infections in SOT recipients. Tedizolid or linezolid-containing regimens demonstrated a potential benefit in symptomatic and microbiologic improvement. Larger cohorts are needed to further delineate the comparative role of linezolid and tedizolid for the treatment of NTM infections in SOT recipients.

Outcomes of Inhaled Amikacin-Containing Multidrug Regimens for Mycobacterium abscessus Pulmonary Disease

BACKGROUND

Mycobacterium abscessus pulmonary disease (M abscessus-PD) is challenging to treat because of its resistance to antibiotics.

RESEARCH QUESTION

What are the outcomes of treatment-naive patients with M abscessus-PD treated with inhaled amikacin-containing multidrug regimens?

STUDY DESIGN AND METHODS

We identified 82 treatment-naive patients with M abscessus-PD from a prospective observational cohort treated with regimens containing inhaled amikacin with or without clofazimine between March 2015 and June 2018 (ClinicalTrials.gov identifier: NCT00970801). During the initial phase, all patients received IV amikacin, imipenem (or cefoxitin), and oral azithromycin. Oral clofazimine was added in cases of (1) M abscessus subspecies abscessus (here M abscessus) or (2) M abscessus subspecies massiliense (here M massiliense) with cavitary lesions. During the continuation phase, amikacin was changed from an injectional to inhalational form.

RESULTS

Of 82 patients, 46 (56%) had M massiliense-PD and 36 (44%) had M abscessus-PD. Among 59 patients with nodular bronchiectatic disease (72%), 23 of 59 had a concurrent cavitary lesion. The remaining 23 patients (28%) had fibrocavitary disease. Twelve months after treatment initiation, cure was achieved in 53 patients (65%): 42 of 46 patients (91%) with M massiliense-PD and 11 of 36 patients (31%) with M abscessus-PD (P < .001). Symptomatic and radiologic improvements were observed in 72 patients (88%) and 64 patients (78%), respectively, with significantly greater improvement in patients with M massiliense-PD (symptom improvement, 96% vs 78% [P = .047]; improvement on CT scanning, 93% vs 61% [P = .002]).

INTERPRETATION

Inhaled amikacin with or without clofazimine in the regimen provides favorable treatment outcomes in M massiliense-PD. However, more effective treatments are needed for M abscessus-PD.

Treatment for Mycobacterium abscessus complex-lung disease

Nontuberculous mycobacterial infections and colonization are becoming more prevalent worldwide. Mycobacterium abscessus complex (MABC) is one of the predominant pathogens capable of a wide spectrum of infections, with 50% of infections involving the lungs. The decision to commence treatment is determined according to the severity of the disease, risk of progressive disease, presence of comorbidities, and goals of treatment. MABC is resistant to standard antituberculous agents and has variable drug susceptibility across different geographical locations, therefore, antibiotic susceptibility testing of all clinically significant isolates is crucial for selecting a treatment strategy. Pulmonary infections due to MABC is difficult to cure using the currently recommended regimens from the American Thoracic Society and British Thoracic Society. Macrolides are the cornerstone of treatment, but the efficacy of macrolide-based chemotherapy may be compromised by resistance. Despite the introduction of new drugs for treatment, treatment outcomes remain unsatisfactory. The combination of surgical resection of limited lung disease regions with a multidrug, macrolide-based therapy offers the optimal chance of achieving clinical cure of the disease. This review focuses on medical treatment of MABC-lung disease and the efficacy of new agents, such as clofazimine, amikacin inhalation therapy, tigecycline and linezolid, for treating MABC-lung disease.

Treatment of pulmonary disease caused by Mycobacterium kansasii

As a cause of lung disease (LD), Mycobacterium kansasii is regarded as a highly virulent species among nontuberculous mycobacteria (NTM). Both the frequency of M. kansasii isolates and global prevalence of M. kansasii-LD have increased gradually over recent decades. Treatment of M. kansasii-LD is recommended because of the disease's poor prognosis and fatal outcome. The decision on the optimal time point for treatment initiation should be based on both the benefits and risks posed by multiple antimicrobial agents. For treatment-naïve patients with M. kansasii-LD, rifampin-containing multiple antimicrobial regimens for ≥12 months after culture negative conversion are effective. However, some challenges remain, such as determining the precise length of treatment duration as well as addressing intolerable adverse effects, the uncertain effectiveness of isoniazid and ethambutol in treatment, the uncertain correlation between in vitro drug susceptibility testing and clinical outcomes, and the increasing prevalence of clarithromycin-resistant M. kansasii isolates. Short-course and effective therapies must be developed. New candidate drugs, such as tedizoid and clofazimine, exhibit excellent antimycobacterial activity against M. kansasii in vitro, but in vivo studies of their clinical applications are lacking. This paper reviews the treatment, outcomes and future directions in patients with M. kansasii-LD.

Looking beyond Typical Treatments for Atypical Mycobacteria

The genus Mycobacterium comprises not only the deadliest of bacterial pathogens, Mycobacterium tuberculosis, but several other pathogenic species, including M. avium and M. abscessus. The incidence of infections caused by atypical or nontuberculous mycobacteria (NTM) has been steadily increasing, and is associated with a panoply of diseases, including pulmonary, soft-tissue, or disseminated infections. The treatment for NTM disease is particularly challenging, due to its long duration, to variability in bacterial susceptibility profiles, and to the lack of evidence-based guidelines. Treatment usually consists of a combination of at least three drugs taken from months to years, often leading to severe secondary effects and a high chance of relapse. Therefore, new treatment approaches are clearly needed. In this review, we identify the main limitations of current treatments and discuss different alternatives that have been put forward in recent years, with an emphasis on less conventional therapeutics, such as antimicrobial peptides, bacteriophages, iron chelators, or host-directed therapies. We also review new forms of the use of old drugs, including the repurposing of non-antibacterial molecules and the incorporation of antimicrobials into ionic liquids. We aim to stimulate advancements in testing these therapies in relevant models, in order to provide clinicians and patients with useful new tools with which to treat these devastating diseases.

Can cryotherapy be used as an adjunct in select cases of recalcitrant endophthalmitis? - A case report

We report two cases of recalcitrant endophthalmitis, a delayed postoperative fungal endophthalmitis following cataract surgery and an atypical mycobacterial endogenous endophthalmitis associated with infective scleritis. Due to recalcitrant nature of the endophthalmitis, one or more sittings of double freeze and thaw cryotherapy was applied over and adjacent to the infective foci in each case. This cryotherapy was used as an adjunct alongside conventional endophthalmitis management following which resolution of infection was observed in both cases.

Pharmacotherapy Approaches in Nontuberculous Mycobacteria Infections

Nontuberculous mycobacteria (NTM) comprise a heterogeneous group of organisms, with only a small subset known to cause disease in humans. Although NTM infection is not a reportable disease, both the increasing clinical recognition and recent advancements in laboratory diagnostic capabilities of NTM infections in immunocompromised and immunocompetent patients are rapidly evolving. We reviewed antimicrobial agents used to treat the most frequently encountered NTM infections and examined optimized drug dosing strategies, toxicity profiles, drug-drug interactions, and the role of therapeutic drug monitoring. Antimicrobial susceptibility testing and patient monitoring on therapy were also examined. We used PubMed to review the published literature on the management of select NTM pathogens, the common syndromes encountered since 2000, and select pharmacokinetic principles of select antimicrobial agents used since 1990. We included select clinical trials, systematic reviews, published guidelines, and observational studies when applicable. The prolonged duration and the necessity for combination therapy for most forms of NTM disease can be problematic for many patients. A multidisciplinary care team that includes pharmacy engagement may help increase rates of optimal patient tolerability and successful treatment completion.

Non-tuberculous mycobacterial pulmonary disease

Nontuberculous mycobacterial pulmonary disease (NTM-PD) is a challenging infection which is becoming increasingly prevalent, particularly in the elderly, for reasons which are unknown. While underlying lung disease is a well-established risk factor for NTM-PD, it may also occur in apparently healthy individuals. No single common genetic or immunological defect has been identified in this group, and it is likely that multiple pathways contribute towards host susceptibility to NTM-PD which further interact with environmental and microbiological factors leading to the development of disease.The diagnosis of NTM-PD relies on the integration of clinical, radiological and microbiological results. The clinical course of NTM-PD is heterogeneous, with some patients remaining stable without the need for treatment and others developing refractory disease associated with considerable mortality and morbidity. Treatment regimens are based on the identity of the isolated species, drug sensitivity testing (for some agents) and the severity of disease. Multiple antibiotics are typically required for prolonged periods of time and treatment is frequently poorly tolerated. Surgery may be beneficial in selected cases. In some circumstances cure may not be attainable and there is a pressing need for better regimens to treat refractory and drug-resistant NTM-PD.This review summarises current knowledge on the epidemiology, aetiology and diagnosis of NTM-PD and discusses the treatment of two of the most clinically significant species, the M. avium and M. abscessus complexes, with a focus on refractory disease and novel therapies.

Managing antibiotic resistance in nontuberculous mycobacterial pulmonary disease: challenges and new approaches

Introduction: The incidence and prevalence rates of nontuberculous mycobacterial (NTM) pulmonary disease have been continuously increasing worldwide. However, the rate of successful treatment of this disease greatly needs improving, particularly when intrinsic (natural) drug resistance and acquired drug resistance in NTM pulmonary disease are associated with poor outcomes for patients. Areas covered: This review covers the major pathogens that cause NTM pulmonary disease caused by Mycobacterium avium complex, Mycobacterium abscessus, and Mycobacterium kansasii; the key drugs and recommended regimens used in the treatment of NTM pulmonary disease; the factors that contribute to resistance to the key drugs, including genetic factors and monotherapy; and the treatment strategies, including revised antibiotic regimens and surgery, that can be used to treat drug-resistant NTM pulmonary disease. Expert opinion: To avoid and overcome drug resistance in NTM pulmonary disease, the appropriate guideline-based treatments are essential, and clinical studies to evaluate new or repurposed drugs are urgently needed.

Medical Management of Pulmonary Nontuberculous Mycobacterial Disease

Nontuberculous mycobacterial (NTM) lung infections are increasingly recognized as a cause of chronic pulmonary disease. This article focuses on the most common NTM species known to cause human lung disease and the treatment options currently available. The diagnosis of NTM lung disease is also discussed, emphasizing the necessity for treating clinicians to have sufficient familiarity of the mycobacteria laboratory to provide optimal patient management.

Recent advances in molecular diagnostics and understanding mechanisms of drug resistance in nontuberculous mycobacterial diseases

Accumulating evidence suggests that human infections caused by nontuberculous mycobacteria (NTM) are increasing worldwide, indicating that NTM disease is no longer uncommon in many countries. As a result of an increasing emphasis on the importance of differential identification of NTM species, several molecular tools have recently been introduced in clinical and experimental settings. These advances have led to a much better understanding of the diversity of NTM species with regard to clinical aspects and the potential factors responsible for drug resistance that influence the different outcomes of NTM disease. In this paper, we review currently available molecular diagnostics for identification and differentiation of NTM species by summarizing data from recently applied methods, including commercially available assays, and their relevant strengths and weaknesses. We also highlight drug resistance-associated genes in clinically important NTM species. Understanding the basis for different treatment outcomes with different causative species and drug-resistance mechanisms will eventually improve current treatment regimens and facilitate the development of better control measures for NTM diseases.

Management of a Mycobacterium immunogenum infection of a peritoneal dialysis catheter site

Mycobacterium immunogenum is a member of the rapidly growing non-tuberculous mycobacteria and is a relatively new species identified within this group. An 81-year-old immune-competent male was diagnosed with M. immunogenum infection of his peritoneal dialysis catheter exit site and surrounding soft tissue. To our knowledge, this is the first reported case of M. immunogenum infection of a peritoneal catheter. Treatment included catheter removal, local surgical debridement, and combination antimicrobial therapy. Herein, we review literature describing antibiotic management of M. immunogenum, an organism for which optimal therapy is not defined.

Respiratory infections due to nontuberculous mycobacterias

The most common infections caused by nontuberculous mycobacteria (NTM) are lung infections. The microorganisms causing these infections most frequently are Mycobacterium avium complex, Mycobacterium kansasii and Mycobacterium abscessus complex. Their incidence has increased in the last three decades. After identifying an NTM in the respiratory tract, clinical and radiological aspects must be considered to determine if isolations are clinically relevant. Predisposing conditions that could contribute to infection must also be investigated. Pulmonary disease due to NTM is presented in three clinical forms: a) pneumonitis due to hypersensitivity; b) fibrocavitary form; and c) nodular-bronchiectasic. The diagnosis of respiratory disease due to NTM does not make it obligatory to immediately initiate treatment. Before initiating the latter, other factors must be considered, such as age, comorbidities, life expectancy, due to the prolonged nature of treatments, with potential side effects and, in many cases, only a slight response to the treatment.

Nontuberculous mycobacteria in cystic fibrosis: Updates and the path forward

Nontuberculous mycobacteria (NTM) are troublesome pathogens that can cause significant pulmonary disease in patients with cystic fibrosis (CF). Diagnosis can be difficult in the setting of underlying CF and treatment regimens are burdensome on both patients and providers. Recent consensus guidelines for treatment of NTM in CF have provided a guide for the CF community, however research is lagging regarding accuracy of our diagnostic abilities and treatment efficacy. In this review, we provide new insights into the complexity of NTM from emerging whole genome sequencing data, a summary of current NTM diagnosis and treatment guidelines, highlight new treatment options, and discuss future research projects which aim to better define which patients to treat and timing and duration of treatment.

Pulmonary disease by non-tuberculous mycobacteria - clinical management, unmet needs and future perspectives

INTRODUCTION

The number of patients with pulmonary disease caused by non-tuberculous mycobacteria (NTM) is increasing globally. Poor resistance against infections, for example, due to pre-existing lung diseases, immune deficiency and immune-modulating treatment, predisposes the population to developing pulmonary NTM disease. The incidence of pre-existing lung diseases such as chronic obstructive pulmonary disease and bronchiectasis has also increased. NTM disease diagnosis is often delayed due to non-specific symptoms. The therapeutic arsenal is limited and adherence to treatment guidelines is often low since the treatment regimens are complex, lengthy and side effects are common. Thus, current disease management is far from satisfactory and needs to be improved. Areas covered: This review provides an overview of the current knowledge of NTM infections and includes pathogenesis, disease patterns, epidemiology, disease management, unmet needs and future perspectives. Expert commentary: NTM disease is becoming more prevalent, in part with our increased awareness and improved diagnostic methods. However, our understanding of the disease pathogenesis is limited and treatment decisions are challenging, with difficult to employ drug regimens. Optimal management requires collaboration between healthcare providers, patients and expert centers.

Mycobacterium avium Complex Disease

Despite the ubiqitous nature of Mycobacterium avium complex (MAC) organisms in the environment, relatively few of those who are infected develop disease. Thus, some degree of susceptibility due to either underlying lung disease or immunosuppression is required. The frequency of pulmonary MAC disease is increasing in many areas, and the exact reasons are unknown. Isolation of MAC from a respiratory specimen does not necessarily mean that treatment is required, as the decision to treatment requires the synthesis of clinical, radiographic, and microbiologic information as well as a weighing of the risks and benefits for the individual patient. Successful treatment requires a multipronged approach that includes antibiotics, aggressive pulmonary hygiene, and sometimes resection of the diseased lung. A combination of azithromycin, rifampin, and ethambutol administered three times weekly is recommend for nodular bronchiectatic disease, whereas the same regimen may be used for cavitary disease but administered daily and often with inclusion of a parenteral aminoglycoside. Disseminated MAC (DMAC) is almost exclusively seen in patients with late-stage AIDS and can be treated with a macrolide in combination with ethambutol, with or without rifabutin: the most important intervention in this setting is to gain HIV control with the use of potent antiretroviral therapy. Treatment outcomes for many patients with MAC disease remain suboptimal, so new drugs and treatment regimens are greatly needed. Given the high rate of reinfection after cure, one of the greatest needs is a better understanding of where infection occurs and how this can be prevented.

[Nontuberculous mycobacterial pulmonary disease]

Nontuberculous mycobacteria (NTM) are a group of biologically diverse, ubiquitous and naturally multi-drug resistant bacteria with facultative pathogenicity. Recent data suggest that their clinical significance is increasing worldwide and that susceptible individuals may be at risk for infection via contaminated surfaces and aerosols. These individuals often have a predisposition for chronic respiratory diseases, e. g. bronchiectasis, chronic obstructive pulmonary disease (COPD) and cystic fibrosis and these conditions frequently share the same unspecific signs and symptoms with NTM pulmonary disease (NTM-PD). As a consequence, the diagnosis of NTM-PD, which is established based on clinical, radiological and microbiological criteria, is often delayed. Treating NTM-PD is more demanding than treating pulmonary tuberculosis as therapy is generally more tedious, toxic and expensive as well as being prone to failure. Patient and pathogen-specific factors guide the choice of an appropriate antimicrobial combination regimen, which should comply with national and international recommendations. Adverse events are common, should be anticipated and closely monitored. If infections with infrequently encountered mycobacterial species and severe or refractory disease occur, an interdisciplinary approach should be used, involving infectious disease specialists, experienced thoracic surgeons and referral to an NTM specialist center.

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.

Pulmonary Disease Caused by Non-Tuberculous Mycobacteria

Non-tuberculous mycobacteria (NTM) include more than 160 ubiquitous, environmental, acid-fast-staining bacterial species, some of which may cause disease in humans. Chronic pulmonary infection is the most common clinical manifestation. Although patients suffering from chronic lung diseases are particularly susceptible to NTM pulmonary disease, many affected patients have no apparent risk factors. Host and pathogen factors leading to NTM pulmonary disease are not well understood and preventive therapies are lacking. NTM isolation and pulmonary disease are reported to rise in frequency in Europe as well as in other parts of the world. Differentiation between contamination, infection, and disease remains challenging. Treatment of NTM pulmonary disease is arduous, lengthy, and costly. Correlations between results of in vitro antibiotic susceptibility testing and clinical treatment outcomes are only evident for the Mycobacterium avium complex, M. kansasii, and some rapidly growing mycobacteria. We describe the epidemiology of NTM pulmonary disease as well as emerging NTM pathogens and their geographical distribution in non-cystic fibrosis patients in Europe. We also review recent innovations for the diagnosis of NTM pulmonary disease, summarize treatment recommendations, and identify future research priorities to improve the management of patients affected by NTM pulmonary disease.

Diagnosis and Treatment of Nontuberculous Mycobacterial Lung Disease: Clinicians' Perspectives

Nontuberculous mycobacteria (NTM) are emerging pathogens that affect both immunocompromised and immunocompetent patients. The incidence and prevalence of NTM lung disease are increasing worldwide and rapidly becoming a major public health problem. For the diagnosis of NTM lung disease, patients suspected to have NTM lung disease are required to meet all clinical and microbiologic criteria. The development of molecular methods allows the characterization of new species and NTM identification at a subspecies level. Even after the identification of NTM species from respiratory specimens, clinicians should consider the clinical significance of such findings. Besides the limited options, treatment is lengthy and varies by species, and therefore a challenge. Treatment may be complicated by potential toxicity with discouraging outcomes. The decision to start treatment for NTM lung disease is not easy and requires careful individualized analysis of risks and benefits. Clinicians should be alert to those unique aspects of NTM lung disease concerning diagnosis with advanced molecular methods and treatment with limited options. Current recommendations and recent advances for diagnosis and treatment of NTM lung disease are summarized in this article.

Antibiotic treatment for nontuberculous mycobacterial lung disease

Pulmonary infections are the most frequent diseases caused by nontuberculous mycobacteria (NTM). Common causative organisms of pulmonary infection are slowly growing mycobacteria including Mycobacterium avium complex and Mycobacterium kansasii, and rapidly growing mycobacteria including Mycobacterium abscessus complex. Clinical concern has been raised over the increasing incidence of NTM lung disease combined with the poor treatment outcomes of these chronic infectious diseases. Since treatment guidelines of the American Thoracic Society/Infectious Disease Society of America were published in 2007 there have been continuous efforts to improve the outcomes of NTM lung disease, albeit slowly and with limitations. Here, we focus on recent advances in the antibiotic treatment of NTM lung disease.