Oral Macrolide Therapy Following Short-term Combination Antibiotic Treatment of Mycobacterium massiliense Lung Disease

Outcomes of Intermittent Multidrug IV Therapy for Refractory Mycobacterium abscessus Pulmonary Disease

BACKGROUND

No studies have reported therapies for the treatment of patients with refractory Mycobacterium abscessus pulmonary disease (MAB-PD). We implemented intermittent multidrug IV therapy (IMIT) through repeated hospitalizations for patients with MAB-PD who were refractory to antibiotics for more than 12 months.

RESEARCH QUESTION

What are the effects of IMIT on patients with refractory MAB-PD?

STUDY DESIGN AND METHODS

The IV antibiotics administered for IMIT included amikacin, imipenem, and tigecycline, and the outcomes for 36 patients who underwent IMIT for refractory MAB-PD were evaluated. Patients were repeatedly hospitalized and administered IMIT on recurrent symptoms or radiographic evidence of deterioration, while maintaining oral/inhaled antibiotics.

RESULTS

Of the 36 patients, 26 (72%) had M abscessus subspecies abscessus (herein, M abscessus)-PD, and 10 (28%) had M abscessus subspecies massiliense (herein, M massiliense)-PD. The median number of hospitalizations for IMIT was two (interquartile range, 1-3) for patients with M abscessus-PD and one (interquartile range, 1-2) for patients with M massiliense-PD. At least one negative culture result and culture conversion were observed in 62% and 12% of patients with M abscessus-PD, and in 80% and 60% of patients with M massiliense-PD, respectively. Symptomatic improvement was observed in all patients, and radiologic improvement, including cavity amelioration or no deterioration, was observed in 42% and 70% of patients with M abscessus-PD and with M massiliense-PD, respectively. No resistance to clarithromycin or amikacin was acquired.

INTERPRETATION

IMIT with intermittent hospitalization can be a beneficial palliative treatment for patients with refractory MAB-PD. This therapy alleviated symptoms, slowed radiologic progression, and reduced the bacterial burden in some patients. However, radiologic and microbiological responses to IMIT were more apparent in M massiliense-PD than in M abscessus-PD.

Medications and Monitoring in Treatment of Nontuberculous Mycobacterial Pulmonary Disease

In the treatment of nontuberculous mycobacteria (NTM) lung disease, clinicians must consider potential toxicities that may occur as a result of prolonged exposure to a multidrug antibiotic regimen. Frequent clinical and microbiological monitoring is required to assess response and guide treatment duration. This article summarizes toxicity profiles of the antibiotics that are most frequently prescribed for the treatment of NTM lung disease. The role of therapeutic drug monitoring during use of amikacin and linezolid is discussed. The available evidence to guide frequency and extent of medication monitoring during NTM treatment is provided.

Efficacy of Omadacycline-Containing Regimen in a Mouse Model of Pulmonary Mycobacteroides abscessus Disease

Mycobacteroides abscessus is an opportunistic pathogen in people with structural lung conditions such as bronchiectasis, chronic obstructive pulmonary disease, and cystic fibrosis. Pulmonary M. abscessus infection causes progressive symptomatic and functional decline as well as diminished lung function and is often incurable with existing antibiotics. We investigated the efficacy of a new tetracycline, omadacycline, in combination with existing antibiotics recommended to treat this indication, in a mouse model of M. abscessus lung disease. Amikacin, azithromycin, bedaquiline, biapenem, cefoxitin, clofazimine, imipenem, linezolid, and rifabutin were selected as companions to omadacycline. M. abscessus burden in the lungs of mice over a 4-week treatment duration was considered the endpoint. Omadacycline in combination with linezolid, imipenem, cefoxitin, biapenem, or rifabutin exhibited early bactericidal activity compared to any single drug. Using three M. abscessus isolates, we also determined the in vitro frequency of spontaneous resistance against omadacycline to be between 1.9 × 10-10 and 6.2 × 10-10 and the frequency of persistence against omadacycline to be between 5.3 × 10-6 and 1.3 × 10-5. Based on these findings, the combination of omadacycline and select drugs that are included in the recent treatment guidelines may exhibit improved potency to treat M. abscessus lung disease. IMPORTANCE M. abscessus disease incidence is increasing in the United States. This disease is difficult to cure with existing antibiotics. In this study, we describe the efficacy of a new tetracycline antibiotic, omadacycline, in combination with an existing antibiotic to treat this disease. A mouse model of M. abscessus lung disease was used to assess the efficacies of these experimental treatment regimens. Omadacycline in combination with select existing antibiotics exhibited bactericidal activity during the early phase of treatment.

Rapid and Accurate Discrimination of Mycobacterium abscessus Subspecies Based on Matrix-Assisted Laser Desorption Ionization-Time of Flight Spectrum and Machine Learning Algorithms

Mycobacterium abscessus complex (MABC) has been reported to cause complicated infections. Subspecies identification of MABC is crucial for adequate treatment due to different antimicrobial resistance properties amid subspecies. However, long incubation days are needed for the traditional antibiotic susceptibility testing (AST). Delayed effective antibiotics administration often causes unfavorable outcomes. Thus, we proposed a novel approach to identify subspecies and potential antibiotic resistance, guiding early and accurate treatment. Subspecies of MABC isolates were determined by secA1, rpoB, and hsp65. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) spectra were analyzed, and informative peaks were detected by random forest (RF) importance. Machine learning (ML) algorithms were used to build models for classifying MABC subspecies based on spectrum. The models were validated by repeated five-fold cross-validation to avoid over-fitting. In total, 102 MABC isolates (52 subspecies abscessus and 50 subspecies massiliense) were analyzed. Top informative peaks including m/z 6715, 4739, etc. were identified. RF model attained AUROC of 0.9166 (95% CI: 0.9072-0.9196) and outperformed other algorithms in discriminating abscessus from massiliense. We developed a MALDI-TOF based ML model for rapid and accurate MABC subspecies identification. Due to the significant correlation between subspecies and corresponding antibiotics resistance, this diagnostic tool guides a more precise and timelier MABC subspecies-specific treatment.

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.

Case report of a near-fatal case of Mycobacterium massiliense sepsis after de-clotting of an arteriovenous fistula

Background

Mycobacterium massiliense is a rapidly growing a non-tuberculous mycobacterium that has been validated as a separate species from the Mycobacterium abscessus group. Only few antibiotics have demonstrated germicidal activity against Mycobacterium massiliense, and some of those include amikacin, clarithromycin, and cefoxitin.

Case presentation

We present the first reported case of near-fatal septic shock caused by disseminated Mycobacterium massiliense after de-clotting of an infected arteriovenous fistula, in a patient with end-stage renal disease with concomitant human immunodeficiency virus infection. Early recognition of the culprit organism and treatment with a combination therapy of clarithromycin and amikacin led to rapid improvement.

Conclusion

This unique case can highlight the importance of taking into consideration Mycobacterium massiliense infection as a cause of arteriovenous fistula thrombosis and highlights the risk of disseminated infection leading to life threatening sepsis upon de-clotting of the fistula.

Treatment of Mycobacterium abscessus Pulmonary Disease

Mycobacterium abscessus is the second most common nontuberculous mycobacterial lung disease pathogen and comprises three subspecies: abscessus, massiliense, and bolletii. Subspecies identification is critical for disease management, as subspecies abscessus and bolletii have an inducible macrolide resistance gene [erm(41)] that results in clinical macrolide resistance. In contrast, subspecies massiliense does not have an active erm(41) gene and is therefore susceptible in vitro and clinically to macrolide-containing regimens. M abscessus is also vulnerable to acquired mutational macrolide resistance. Macrolide resistance has such a profoundly negative impact on M abscessus treatment response that preserving macrolide susceptibility with adequate companion drugs for macrolides is among the highest treatment priorities. After the macrolides, amikacin is regarded as the next most important drug for M abscessus treatment, although data validating that assertion are lacking. The considerations for preventing acquired macrolide resistance also apply to amikacin. Recent guidelines suggest that treatment should be guided by in vitro susceptibilities but, aside from macrolides and amikacin, no other antibiotics have a validated minimum inhibitory concentration for M abscessus. Currently, phase therapy (intensive and continuation) is recommended for M abscessus. This approach is successful with macrolide-susceptible M abscessus but not with macrolide-resistant M abscessus, in which even more aggressive therapy is not predictably successful. Newer drugs have become available, with encouraging in vitro activity against M abscessus, but in vivo validation of their superiority to current agents is not yet available. In the absence of unequivocally effective regimens, we offer suggestions for managing this treatment-refractory organism.

Clinical Pharmacokinetic and Pharmacodynamic Considerations in the Drug Treatment of Non-Tuberculous Mycobacteria in Cystic Fibrosis

Non-tuberculous mycobacteria (NTM) are an emerging group of pulmonary infectious pathogens of increasing importance to the management of patients with cystic fibrosis (CF). NTM include slow-growing mycobacteria such as Mycobacterium avium complex (MAC) and rapidly growing mycobacteria such as Mycobacterium abscessus. The incidence of NTM in the CF population is increasing and infection contributes to significant morbidity to the patient and costs to the health system. Treating M. abscessus requires the combination of multiple costly antibiotics for months, with potentially significant toxicity associated with treatment. Although international guidelines for the treatment of NTM infection in CF are available, there are a lack of robust pharmacokinetic studies in CF patients to inform dosing and drug choice. This paper aims to outline the pharmacokinetic and pharmacodynamic factors informing the optimal treatment of NTM infections in CF.

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 of Nontuberculous Mycobacterial Pulmonary Disease: An Official ATS/ERS/ESCMID/IDSA Clinical Practice Guideline

Nontuberculous mycobacteria (NTM) represent over 190 species and subspecies, some of which can produce disease in humans of all ages and can affect both pulmonary and extrapulmonary sites. This guideline focuses on pulmonary disease in adults (without cystic fibrosis or human immunodeficiency virus infection) caused by the most common NTM pathogens such as Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium xenopi among the slowly growing NTM and Mycobacterium abscessus among the rapidly growing NTM. A panel of experts was carefully selected by leading international respiratory medicine and infectious diseases societies (ATS, ERS, ESCMID, IDSA) and included specialists in pulmonary medicine, infectious diseases and clinical microbiology, laboratory medicine, and patient advocacy. Systematic reviews were conducted around each of 22 PICO (Population, Intervention, Comparator, Outcome) questions and the recommendations were formulated, written, and graded using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. Thirty-one evidence-based recommendations about treatment of NTM pulmonary disease are provided. This guideline is intended for use by healthcare professionals who care for patients with NTM pulmonary disease, including specialists in infectious diseases and pulmonary diseases.

Treatment of nontuberculous mycobacterial pulmonary disease: an official ATS/ERS/ESCMID/IDSA clinical practice guideline

Nontuberculous mycobacteria (NTM) represent over 190 species and subspecies, some of which can produce disease in humans of all ages and can affect both pulmonary and extrapulmonary sites. This guideline focuses on pulmonary disease in adults (without cystic fibrosis or human immunodeficiency virus infection) caused by the most common NTM pathogens such as Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium xenopi among the slowly growing NTM and Mycobacterium abscessus among the rapidly growing NTM. A panel of experts was carefully selected by leading international respiratory medicine and infectious diseases societies (ATS, ERS, ESCMID, IDSA) and included specialists in pulmonary medicine, infectious diseases and clinical microbiology, laboratory medicine, and patient advocacy. Systematic reviews were conducted around each of 22 PICO (Population, Intervention, Comparator, Outcome) questions and the recommendations were formulated, written, and graded using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. Thirty-one evidence-based recommendations about treatment of NTM pulmonary disease are provided. This guideline is intended for use by healthcare professionals who care for patients with NTM pulmonary disease, including specialists in infectious diseases and pulmonary diseases.

Prognostic factors associated with long-term mortality in 1445 patients with nontuberculous mycobacterial pulmonary disease: a 15-year follow-up study

Limited data are available regarding the prognostic factors for patients with nontuberculous mycobacterial pulmonary disease (NTM-PD). We investigated the prognostic factors associated with long-term mortality in NTM-PD patients after adjusting for individual confounders, including aetiological organism and radiological form.

A total of 1445 patients with treatment-naïve NTM-PD who were newly diagnosed between July 1997 and December 2013 were included. The aetiological organisms were as follows: Mycobacterium avium (n=655), M. intracellulare (n=487), M. abscessus (n=129) and M. massiliense (n=174). The factors associated with mortality in NTM-PD patients were analysed using a multivariable Cox model after adjusting for demographic, radiological and aetiological data.

The overall 5-, 10- and 15-year cumulative mortality rates for the NTM-PD patients were 12.4%, 24.0% and 36.4%, respectively. On multivariable analysis, the following factors were significantly associated with mortality in NTM-PD patients: old age, male sex, low body mass index, chronic pulmonary aspergillosis, pulmonary or extrapulmonary malignancy, chronic heart or liver disease and erythrocyte sedimentation rate. The aetiological organism was also significantly associated with mortality: M. intracellulare had an adjusted hazard ratio (aHR) of 1.40, 95% CI 1.03–1.91; M. abscessus had an aHR of 2.19, 95% CI 1.36–3.51; and M. massiliense had an aHR of 0.99, 95% CI 0.61–1.64, compared to M. avium. Mortality was also significantly associated with the radiological form of NTM-PD for the cavitary nodular bronchiectatic form (aHR 1.70, 95% CI 1.12–2.59) and the fibrocavitary form (aHR 2.12, 95% CI 1.57–3.08), compared to the non-cavitary nodular bronchiectatic form.

Long-term mortality in patients with NTM-PD was significantly associated with the aetiological NTM organism, cavitary disease and certain demographic characteristics.

Computed tomographic findings of macrolide-resistant Mycobacterium massiliense pulmonary disease and changes after antibiotic treatment

The purpose of this study was to present the computed tomographic (CT) findings of lung abnormalities in macrolide-resistant Mycobacterium massiliense pulmonary disease and its changes in follow-up CT after antibiotic treatment.Chest CT scans of patients with macrolide-resistant M massiliense pulmonary disease (n = 19) were retrospectively reviewed. Patients were treated with multidrug therapy, and sputum examinations were performed. Follow-up CT scans obtained during antibiotic treatment after detection of macrolide resistance were also reviewed, if available (n = 13). The CT scores at detection of macrolide resistance and at the last follow-up periods were also compared.Of all patients with macrolide-resistant M massiliense pulmonary disease, 2 (11%) patients achieved sputum culture conversion during the follow-up period. The most common CT findings of M massiliense pulmonary disease at detection of macrolide resistance were bronchiectasis and bronchiolitis (n = 19, 100%), followed by consolidation (n = 16, 84%), cavities (n = 11, 58%), and nodules (n = 6, 32%). On the last follow-up CT, overall CT scores were increased in 8 (62%) of 13 patients, and total mean CT score was significantly increased (P = .021). For each CT pattern, the cavity showed the greatest increase in CT score (P = .027), followed by bronchiectasis (P = .038).Common CT findings of macrolide-resistant M massiliense pulmonary disease were similar to those of pulmonary disease caused by other species of nontuberculous mycobacteria at presentation. However, in macrolide-resistant M massiliense pulmonary disease, serial CT scans showed deterioration with cavitary and bronchiectatic change in most patients despite multidrug antibiotic therapy.

M ycobacterium abscessus pulmonary disease: individual patient data meta-analysis

Treatment of Mycobacterium abscessus pulmonary disease (MAB-PD), caused by M. abscessus subsp. abscessus, M. abscessus subsp. massiliense or M. abscessus subsp. bolletii, is challenging.We conducted an individual patient data meta-analysis based on studies reporting treatment outcomes for MAB-PD to clarify treatment outcomes for MAB-PD and the impact of each drug on treatment outcomes. Treatment success was defined as culture conversion for ≥12 months while on treatment or sustained culture conversion without relapse until the end of treatment.Among 14 eligible studies, datasets from eight studies were provided and a total of 303 patients with MAB-PD were included in the analysis. The treatment success rate across all patients with MAB-PD was 45.6%. The specific treatment success rates were 33.0% for M. abscessus subsp. abscessus and 56.7% for M. abscessus subsp. massiliense For MAB-PD overall, the use of imipenem was associated with treatment success (adjusted odds ratio (aOR) 2.65, 95% CI 1.36-5.10). For patients with M. abscessus subsp. abscessus, the use of azithromycin (aOR 3.29, 95% CI 1.26-8.62), parenteral amikacin (aOR 1.44, 95% CI 1.05-1.99) or imipenem (aOR 7.96, 95% CI 1.52-41.6) was related to treatment success. For patients with M. abscessus subsp. massiliense, the choice among these drugs was not associated with treatment outcomes.Treatment outcomes for MAB-PD are unsatisfactory. The use of azithromycin, amikacin or imipenem was associated with better outcomes for patients with M. abscessus subsp. abscessus.

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.

Long-term natural history of non-cavitary nodular bronchiectatic nontuberculous mycobacterial pulmonary disease

BACKGROUND

Information about the natural history of nontuberculous mycobacterial pulmonary disease (NTM-PD) is limited. The purpose of this study was to evaluate the long-term natural history of non-cavitary nodular bronchiectatic NTM-PD and the factors associated with treatment initiation and the frequency of spontaneous sputum culture conversion after diagnosis of NTM-PD.

METHODS

We evaluated 1,021 patients with newly diagnosed non-cavitary nodular bronchiectatic NTM-PD caused by Mycobacterium avium complex or M. abscessus between 2003 and 2013.

RESULTS

Of 1,021 patients, 562 (55%) initiated antibiotic treatment and 459 (45%) did not. Young age (adjusted hazard ratio [aHR] = 0.99; 95% confidence interval [CI] = 0.98-0.99), low body mass index (aHR = 0.96; 95% CI = 0.93-0.99), previous history of tuberculosis (aHR = 1.23; 95% CI = 1.01-1.50), respiratory complaints such as cough (aHR = 1.36; 95% CI = 1.05-1.75) and sputum production (aHR = 1.47; 95% CI = 1.13-1.91), and high number of involved lobes on high-resolution computed tomography (aHR = 1.22; 95% CI = 1.14-1.31) were associated with treatment initiation. Of 459 patients who did not initiate treatment, 157 (34%) showed spontaneous sputum culture conversion. None of the clinical factors was associated with spontaneous conversion. After spontaneous culture conversion, 26 of 157 (17%) showed redeveloped NTM-PD caused by a species different from the original species.

CONCLUSIONS

The natural history of non-cavitary nodular bronchiectatic NTM-PD is variable. After diagnosis, the decision to initiate antibiotic therapy should be individualized based on consideration of the risk factors for disease progression. However, for patients who do not start antibiotic therapy, continuous and lifetime follow-up is recommended to manage underlying bronchiectasis and the possibility of late progression of NTM-PD.

Assessment of Vitamin Status in Patients with Nontuberculous Mycobacterial Pulmonary Disease: Potential Role of Vitamin A as a Risk Factor

As microbiological diagnostic techniques improve and the frequency of nontuberculous mycobacterial pulmonary disease (NTM-PD) infection increases worldwide, NTM-PD is becoming increasingly important to clinicians and researchers. Vitamin activity has been associated with the host immune response in tuberculosis; however, such information is very limited in NTM-PD. We performed a case-control study in 150 patients with NTM-PD and 150 healthy controls to investigate serum vitamin status. We measured concentrations of vitamins A, D, and E along with homocysteine and methylmalonic acid (MMA) as indicators of vitamin B₁₂ deficiency, using high-performance liquid chromatography (HPLC) or HPLC-tandem mass spectrometry. The serum concentrations of vitamins A and E were significantly lower in patients with NTM-PD than in healthy controls (1.5 vs. 2.1 µmol/L, p < 0.01 for vitamin A; and 27.3 vs. 33.1 µmol/L, p < 0.01 for vitamin E). In contrast, the serum concentrations of vitamin D and homocysteine were not significantly different between the two groups. Vitamin A deficiency (< 1.05 µmol/L) was significantly more prevalent in patients with NTM-PD than in healthy controls (p < 0.01) and was associated with an 11-fold increase in risk of NTM-PD. Multiple vitamin deficiencies were only observed in patients with NTM-PD (7.3% of all NTM-PD patients). Positive correlations were observed among vitamins (vitamins A and D; r = 0.200, p < 0.05; vitamins D and E, r = 0.238, p < 0.05; vitamins A and E, r = 0.352, p < 0.05). Serum vitamin status, demographic variables, and biochemical indicators were not associated with treatment outcomes. Vitamin A deficiency was strongly associated with patients with NTM-PD. Our study suggests that altered vitamin status is associated with mycobacterial disease. Future well-designed prospective studies with large patient cohorts addressing these issues are needed to clarify the significance of vitamins in NTM-PD.

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.

Nontuberculous Mycobacterial Lung Diseases Caused by Mixed Infection with Mycobacterium avium Complex and Mycobacterium abscessus Complex

Mycobacterium avium complex (MAC) and M. abscessus complex (MABC) comprise the two most important human pathogen groups causing nontuberculous mycobacterial lung disease (NTM-LD). However, there are limited data regarding NTM-LD caused by mixed NTM infections. This study aimed to evaluate the clinical characteristics and treatment outcomes in patients with NTM-LD caused by mixed infection with these two major NTM pathogen groups. Seventy-one consecutive patients who had been diagnosed with NTM-LD caused by mixed infection with MAC (M. avium or M. intracellulare) and MABC (M. abscessus or M. massiliense) between January 2010 and December 2015 were identified. Nearly all patients (96%) had the nodular bronchiectatic form of NTM-LD. Mixed infection with MAC and M. massiliense (n = 47, 66%) was more common than mixed infection with MAC and M. abscessus (n = 24, 34%), and among the 43 (61%) patients who were treated for NTM-LD for more than 12 months, sputum culture conversion rates were significantly lower in patients infected with MAC and M. abscessus (25% [3/12]) than in patients infected with MAC and M. massiliense (61% [19/31, P = 0.033]). Additionally, M. massiliense and M. abscessus showed marked differences in clarithromycin susceptibility (90% versus 6%, P < 0.001). Of the 23 patients who successfully completed treatment, 11 (48%) redeveloped NTM lung disease, with mycobacterial genotyping results indicating that the majority of cases were due to reinfection. Precise identification of etiologic NTM organisms could help predict treatment outcomes in patients with NTM-LD due to mixed infections.

Amikacin Inhalation as Salvage Therapy for Refractory Nontuberculous Mycobacterial Lung Disease

Although guidelines recommend amikacin (AMK) inhalation therapy for difficult-to-treat nontuberculous mycobacterial lung disease (NTM-LD), data are limited regarding the safety and clinical efficacy of this salvage therapy. We retrospectively evaluated the treatment outcomes of 77 patients with refractory NTM-LD caused by Mycobacterium abscessus complex (MABC) or M. avium complex (MAC) who initiated AMK inhalation therapy between February 2015 and June 2016. MABC was the most common etiology (n = 48, 62%), followed by MAC (n = 20, 26%) and mixed infections (n = 9, 12%). Isolates with macrolide resistance and baseline AMK resistance were identified in 63 (82%) patients and 5 (6%) patients, respectively. At 12 months after AMK inhalation therapy, 49% of patients had symptomatic improvement, whereas 42% had radiological improvement. Conversion to a negative sputum culture occurred in 14 (18%) patients, and the culture conversion rate was higher in patients infected with macrolide-susceptible isolates (7/14, 50%) than in those infected with macrolide-resistant isolates (7/63, 11%) (P = 0.003). Significant decreases in sputum semiquantitative culture positivity occurred after AMK inhalation therapy (P < 0.001). On multivariate analysis, conversion to a negative sputum culture was associated with mixed infections (P = 0.009), a forced expiratory volume in 1 s of greater than 60% (P = 0.008), and the absence of macrolide resistance (P = 0.003). Thirty-eight percent of patients experienced adverse effects, with ototoxicity (n = 15) being the most common. AMK inhalation salvage therapy may improve the treatment responses in some patients with refractory NTM-LD. However, considering the common adverse effects, further evaluation of the optimal dosage and intervals for AMK inhalation therapy is needed.

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.

Treatment outcomes of macrolide-susceptible Mycobacterium abscessus lung disease

Mycobacterium abscessus lung disease is difficult to treat due to inducible resistance to macrolides. However, 15%-20% of isolates are macrolide susceptible. In 14 patients with macrolide-susceptible M. abscessus lung disease, all isolates had nonfunctional erm(41) gene, and sputum culture conversion rate was achieved in 93% (13/14) following antibiotic therapy.

Association between sequevar and antibiotic treatment outcome in patients with Mycobacterium abscessus complex infections in Japan

PURPOSE

Macrolide susceptibility differs between subspecies in the Mycobacterium abscessus complex, likely due to differences in erm(41) sequevars. Patients with M. abscessus complex infection generally show poor clinical outcomes in response to antibiotic treatment. Here, the association between genotype and treatment outcome was investigated.

METHODOLOGY

We collected 69 isolates from 35 patients with non-cystic fibrosis bronchiectasis: 24 had M. abscessus complex lung disease and non-cystic fibrosis bronchiectasis, and 11 were colonized. Outcome analysis was performed in the 24 infected patients. Molecular analyses, including erm(41) and rrl sequencing, and variable-number tandem-repeat (VNTR) analysis of 69 isolates, from 24 infected and 11 colonized patients, were performed to elucidate the influence of genotype on antibiotic susceptibility.

RESULTS

Among the 24 patients, 18 (14 infected with M. abscessus subsp. abscessus and 4 with M. abscessus subsp. massiliense) showed unfavourable outcomes; six (three infected with M. abscessus subsp. abscessus and three with M. abscessus subsp. massiliense) exhibited favourable outcomes. Patients with unfavourable outcomes showed acquired clarithromycin resistance (33.3 vs 0 %), mixed sequevars (38.9 vs 16.7 %) and differing VNTR patterns between initial and serial isolates (33.3 vs 16.7 %). In contrast, in the 11 colonized patients, M. abscessus subsp. abscessus C28 (sequevar 02) and M. abscessus subsp. massiliense were the most prevalent subspecies.

CONCLUSION

Patients infected with multiple sequevars and genotypes were more likely to exhibit treatment failure and/or recurrence. The precise identification of subspecies and analyses of mycobacterial characteristics may help to predict treatment outcomes in patients with M. abscessus complex lung disease.

Risk factors for the development of chronic pulmonary aspergillosis in patients with nontuberculous mycobacterial lung disease

Nontuberculous mycobacterial lung disease (NTM-LD) is increasingly recognized as an important predisposing condition for the development of chronic pulmonary aspergillosis (CPA), but there are limited data on the risk factors for CPA development in NTM-LD patients. We reviewed the medical records of 566 patients who, at the time of diagnosis of NTM-LD, did not have CPA and who received ≥12 months of treatment for NTM-LD between January 2010 and June 2015. Of these patients, 41 (7.2%) developed CPA (NTM-CPA group), whereas the remaining 525 patients did not develop CPA (NTM group). The median time to the development of CPA was 18.0 months from treatment initiation for NTM-LD. The NTM-CPA group was older and had significantly higher proportions of males, current smokers, and patients with a low body mass index (<18.5 kg/m2), when compared to the NTM group. Moreover, the NTM-CPA group was more likely to have a history of tuberculosis and chronic obstructive lung disease and to have used inhaled or systemic steroids. In the NTM-CPA group, more than 40% of patients had Mycobacterium abscessus complex (MABC) as the cause of NTM-LD, and the fibrocavitary form of NTM-LD was the most common; both associations were higher than in the NTM group. Overall, 17 (3%) patients died, and the NTM-CPA group had a higher mortality rate than did the NTM group (19.5% vs. 1.7%, respectively; P<0.001). In a multivariable analysis, old age, male gender, low body mass index, chronic obstructive lung disease, systemic steroids, MABC as the etiologic organism, and the fibrocavitary form of NTM-LD remained significant predictors of development of CPA. In conclusion, CPA occurred in 7.2% of patients after initiation of treatment for NTM-LD, and some risk factors were associated with CPA development. Given the worse prognosis, early diagnosis and treatment of CPA are important in patients with NTM-LD.

Systematic Review and Meta-analyses of the Effect of Chemotherapy on Pulmonary Mycobacterium abscessus Outcomes and Disease Recurrence

In pharmacokinetic/pharmacodynamic models of pulmonary Mycobacterium abscessus complex, the recommended macrolide-containing combination therapy has poor kill rates. However, clinical outcomes are unknown. We searched the literature for studies published between 1990 and 2017 that reported microbial outcomes in patients treated for pulmonary M. abscessus disease. A good outcome was defined as sustained sputum culture conversion (SSCC) without relapse. Random effects models were used to pool studies and estimate proportions of patients with good outcomes. Odds ratios (OR) and 95% confidence intervals (CI) were computed. Sensitivity analyses and metaregression were used to assess the robustness of findings. In 19 studies of 1,533 patients, combination therapy was administered to 508 patients with M. abscessus subsp. abscessus, 204 with M. abscessus subsp. massiliense, and 301 with M. abscessus with no subspecies specified. Macrolide-containing regimens achieved SSCC in only 77/233 (34%) new M. abscessus subsp. abscessus patients versus 117/141 (54%) M. abscessus subsp. massiliense patients (OR, 0.108 [95% CI, 0.066 to 0.181]). In refractory disease, SSCC was achieved in 20% (95% CI, 7 to 36%) of patients, which was not significantly different across subspecies. The estimated recurrent rates per month were 1.835% (range, 1.667 to 3.196%) for M. abscessus subsp. abscessus versus 0.683% (range, 0.229 to 1.136%) for M. abscessus subsp. massiliense (OR, 6.189 [95% CI, 2.896 to 13.650]). The proportion of patients with good outcomes was 52/223 (23%) with M. abscessus subsp. abscessus versus 118/141 (84%) with M. abscessus subsp. massiliense disease (OR, 0.059 [95% CI, 0.034 to 0.101]). M. abscessus subsp. abscessus pulmonary disease outcomes with the currently recommended regimens are atrocious, with outcomes similar to those for extensively drug-resistant tuberculosis. Therapeutically, the concept of nontuberculous mycobacteria is misguided. There is an urgent need to craft entirely new treatment regimens.

Clinical Characteristics and Treatment Outcomes of Patients with Acquired Macrolide-Resistant Mycobacterium abscessus Lung Disease

Macrolide antibiotics are mainstays in the treatment of lung disease due to the Mycobacterium abscessus complex. Although previous studies have reported development of acquired macrolide resistance in this species, limited data are available on the outcomes of lung disease due to macrolide-resistant Mycobacterium abscessus subsp. abscessus This study evaluated the clinical features, treatment outcomes, and molecular characteristics of macrolide-resistant isolates of M. abscessus subsp. abscessus We performed a retrospective review of medical records and genetic analysis of clinical isolates from 13 patients who had acquired macrolide-resistant M. abscessus subsp. abscessus lung disease between November 2006 and March 2016. Eleven (85%) patients had the nodular bronchiectatic form of the disease, and two (15%) patients had the fibrocavitary form. When acquired macrolide resistance was detected, 10 (77%) patients were on antibiotic therapy for M. abscessus subsp. abscessus, and three (23%) patients were on therapy for lung disease due to other nontuberculous mycobacteria. The median treatment duration after detecting resistance was 24.0 months (interquartile range, 16.0 to 43.0 months). Treatment outcomes were poor, and final sputum culture conversion was achieved in only one (8%) patient, after resectional surgery. All 13 clinical isolates demonstrated point mutations at position 2058 (n = 10) or 2059 (n = 3) of the 23S rRNA gene, which resulted in acquired macrolide resistance. This study indicates that treatment outcomes are very poor after the development of acquired macrolide resistance in patients with M. abscessus subsp. abscessus lung disease. Thus, more effective measures are needed to prevent development and effectively treat macrolide-resistant M. abscessus subsp. abscessus lung disease.

Clofazimine-Containing Regimen for the Treatment of Mycobacterium abscessus Lung Disease

Patients with lung disease caused by Mycobacterium abscessus subsp. abscessus (here M. abscessus) typically have poor treatment outcomes. Although clofazimine (CFZ) has been increasingly used in the treatment of M. abscessus lung disease in clinical practice, there are no reported data on its effectiveness for this disease. This study sought to evaluate the clinical efficacy of a CFZ-containing regimen for the treatment of M. abscessus lung disease. We performed a retrospective review of the medical records of 42 patients with M. abscessus lung disease who were treated with CFZ-containing regimens between November 2013 and January 2015. CFZ was administered in combination with other antibiotics as an initial antibiotic regimen in 15 (36%) patients (initial treatment group), and it was added to an existing antibiotic regimen for refractory M. abscessus lung disease in 27 (64%) patients (salvage treatment group). Overall, there was an 81% treatment response rate based on symptoms and a 31% response rate based on radiographic findings. Conversion to culture-negative sputum samples was achieved in 10 (24%) patients after CFZ-containing antibiotic treatment, and during treatment, there were significant decreases in the positivity of semiquantitative sputum cultures for acid-fast bacilli in both the initial (P = 0.018) and salvage (P = 0.001) treatment groups. Our study suggests that CFZ-containing regimens may improve treatment outcomes in patients with M. abscessus lung disease and that a prospective evaluation of CFZ in M. abscessus lung disease is warranted.

Mycobacteriological characteristics and treatment outcomes in extrapulmonary Mycobacterium abscessus complex infections

OBJECTIVES

The differentiation between Mycobacterium abscessus subspecies abscessus (M. abscessus) and Mycobacterium abscessus subspecies massiliense (M. massiliense) and determination of the presence of inducible resistance to macrolide antibiotics are important factors in the management of patients with Mycobacterium abscessus complex (MABC) infections. Unlike pulmonary MABC infections, little information on extrapulmonary MABC infections is available.

METHODS

The molecular identification of clinical isolates was performed, and the clinical characteristics and treatment outcomes of 20 consecutive patients with extrapulmonary MABC infections were assessed.

RESULTS

M. abscessus and M. massiliense each caused 10 (50%) of the cases. Eight (80%) M. abscessus isolates that had inducible resistance to clarithromycin harbored an intact erm(41) gene of the T28 variant, whereas two (20%) M. abscessus isolates had the C28 erm(41) variant and were susceptible to clarithromycin. All M. massiliense isolates had a truncated erm(41) gene and were susceptible to clarithromycin. The drug susceptibility profiles other than clarithromycin were similar for the M. abscessus and M. massiliense isolates. Of the 20 patients, 17 (85%) showed a favorable outcome, including all patients with M. massiliense infection and 70% (7/10) of patients with M. abscessus infection. Favorable outcomes were associated with M. massiliense and M. abscessus isolates with a non-functional erm(41) gene (p=0.049).

CONCLUSIONS

Precise species and subspecies identification and the determination of macrolide susceptibility are recommended for the optimal treatment of extrapulmonary MABC infections.

[Infections in cystic fibrosis: Up-to-date]

This review focused on the news in CF airways infection. International guidelines were provided for the care of non tuberculous mycobacteria, and recent studies stressed on the benefit effect of azithromycin or combined antibiotics. The identification of multiresistant environmental bacteria in airways made to account for little-known consequences. Early diagnosis and eradication of Pseudomonas aeruginosa and Staphylococcus aureus methi-R were still a concern, and reports were proposed. However, the studies on staphylococcus methi-R should be interpreted as regards the European or American continent. Thus, levofloxacine has demonstrated its efficacy without enhancing the efficiency. This drug will increase the choice for treating the patient, but no study were provided on the expected modification of the patient microbiota and the known risk of emergent resistance to antibiotics. Lastly, this review underlined that the CF practitioner was encouraged to search and not underestimate the presence of fungus, of which the not so well studied Aspergillus fumigatus.

Clinical Characteristics and Treatment Outcomes of Patients with Macrolide-Resistant Mycobacterium massiliense Lung Disease

Macrolide antibiotics are cornerstones in the treatment of Mycobacterium massiliense lung disease. Despite the emergence of resistance, limited data on macrolide-resistant M massiliense lung disease are available. This study evaluated the clinical features and treatment outcomes of patients and the molecular characteristics of macrolide-resistant M massiliense isolates. We performed a retrospective review of medical records and genetic analyses of clinical isolates from 15 patients who had macrolide-resistant M massiliense lung disease between September 2005 and February 2015. Nine patients (60%) had the nodular bronchiectatic form of the disease, and six (40%) had the fibrocavitary form. Before the detection of macrolide resistance, three patients (20%) were treated with macrolide monotherapy, four (27%) with therapy for presumed Mycobacterium avium complex infections, and eight (53%) with combination antibiotic therapy for M massiliense lung disease. The median treatment duration after the detection of resistance was 18.7 months (interquartile range, 11.2 to 39.8 months). Treatment outcomes were poor, with a favorable outcome being achieved for only one patient (7%), who underwent surgery in addition to antibiotic therapy. The 1-, 3-, and 5-year mortality rates were 7, 13, and 33%, respectively. Of the 15 clinical isolates, 14 (93%) had point mutations at position 2058 (n = 9) or 2059 (n = 5) of the 23S rRNA gene, resulting in macrolide resistance. Our study indicates that treatment outcomes are poor and mortality rates are high after the development of macrolide resistance in patients with M massiliense lung disease. Thus, preventing the development of macrolide resistance should be a key consideration during treatment.

Progression and Treatment Outcomes of Lung Disease Caused by Mycobacterium abscessus and Mycobacterium massiliense

BACKGROUND

Mycobacterium abscessus and Mycobacterium massiliense are grouped as the Mycobacterium abscessus complex. The aim of this study was to elucidate the differences between M. abscessus and M. massiliense lung diseases in terms of progression rate, treatment outcome, and the predictors thereof.

METHODS

Between 1 January 2006 and 30 June 2015, 56 patients and 54 patients were diagnosed with M. abscessus and M. massiliense lung diseases, respectively. The time to progression requiring treatment and treatment outcomes were compared between the 2 groups of patients, and predictors of progression and sustained culture conversion with treatment were analyzed. In addition, mediation analysis was performed to evaluate the effect of susceptibility to clarithromycin on treatment outcomes.

RESULTS

During follow-up, 21 of 56 patients with M. abscessus lung diseases and 21 of 54 patients with M. massiliense lung diseases progressed, requiring treatment. No difference was detected in the time to progression between the 2 patient groups. Lower body mass index, bilateral lung involvement, and fibrocavitary-type disease were identified as predictors of disease progression. Among the patients who began treatment, infection with M. massiliense rather than M. abscessus and the use of azithromycin rather than clarithromycin were associated with sustained culture conversion. The difference in treatment outcomes was partly mediated by the organism's susceptibility to clarithromycin.

CONCLUSIONS

Progression rates were similar but treatment outcomes differed significantly between patients with lung disease caused by M. abscessus and M. massiliense. This difference in treatment outcomes was partly explained by the susceptibility of these organisms to clarithromycin.

Mycobacterial Characteristics and Treatment Outcomes in Mycobacterium abscessus Lung Disease

Background

Treatment outcomes of patients with Mycobacterium abscessus subspecies abscessus lung disease are poor, and the microbial characteristics associated with treatment outcomes have not been studied systematically. The purpose of this study was to identify associations between microbial characteristics and treatment outcomes in patients with M. abscessus lung disease.

Methods

Sixty-seven consecutive patients with M. abscessus lung disease undergoing antibiotic treatment for ≥12 months between January 2002 and December 2012 were included. Morphotypic and genetic analyses were performed on isolates from 44 patients.

Results

Final sputum conversion to culture negative occurred in 34 (51%) patients. Compared to isolates from 24 patients with persistently positive cultures, pretreatment isolates from 20 patients with final negative conversion were more likely to exhibit smooth colonies (9/20, 45% vs 2/24, 8%; P = .020), susceptibility to clarithromycin (7/20, 35% vs 1/24, 4%; P = .015), and be of the C28 sequevar with regard to the erm(41) gene (6/20, 30% vs 1/24, 4%; P = .035). Mycobacterium abscessus lung disease recurred in 5 (15%) patients after successful completion of antibiotic therapy. Genotypic analysis revealed that most episodes (22/24, 92%) of persistently positive cultures during antibiotic treatment and all cases of microbiologic recurrence after treatment completion were caused by different M. abscessus genotypes within a patient.

Conclusions

Precise identification to the subspecies level and analysis of mycobacterial characteristics could help predict treatment outcomes in patients with M. abscessus lung disease. Treatment failures and recurrences are frequently associated with multiple genotypes, suggesting reinfection.

Clinical Trials Registration

NCT00970801.

Clinical Characteristics, Treatment Outcomes, and Resistance Mutations Associated with Macrolide-Resistant Mycobacterium avium Complex Lung Disease

Macrolide antibiotics are key components of the multidrug treatment regimen for treating lung disease (LD) due to Mycobacterium avium complex (MAC). Despite the emergence of macrolide resistance, limited data are available on macrolide-resistant MAC-LD. This study evaluated the clinical features and treatment outcomes of patients with macrolide-resistant MAC-LD and the molecular characteristics of the macrolide-resistant isolates. A retrospective review of the medical records of 34 patients with macrolide-resistant MAC-LD who were diagnosed between January 2002 and December 2014 was performed, along with genetic analysis of 28 clinical isolates. Nineteen (56%) patients had the fibrocavitary form of MAC-LD, and 15 (44%) had the nodular bronchiectatic form. M. intracellulare was the etiologic organism in 21 (62%) patients. Approximately two-thirds (22/34 [65%]) of the patients had been treated with currently recommended multidrug regimens that included macrolide, ethambutol, and rifamycin prior to the emergence of macrolide resistance, and none had been treated with macrolide monotherapy. The median duration of treatment after the detection of macrolide resistance was 23.0 months (interquartile range, 16.8 to 45.3 months). Treatment outcomes were poor after the development of macrolide resistance, with favorable treatment outcomes achieved in only five (15%) patients, including two patients who underwent surgical resection. One-, 3-, and 5-year mortality rates were 9, 24, and 47%, respectively. Molecular analysis of 28 clinical isolates revealed that 96% (27/28) had point mutations at position 2058 or 2059 of the 23S rRNA gene. Our analyses indicate that more effective therapy is needed to treat macrolide-resistant MAC-LD and prevent its development.