Spontaneous sputum conversion and reversion in Mycobacterium abscessus complex lung disease

Treatment of nontuberculous mycobacterial pulmonary disease requires a stepwise and multidisciplinary approach

INTRODUCTION

Nontuberculous mycobacterial pulmonary disease (NTM-PD) occurs in people with inborn or acquired susceptibility factors. Current treatment guideline recommendations include a watchful waiting strategy, antimycobacterial and surgical treatment, with a comprehensive assessment of clinical, microbiological, and radiological factors determining which approach is most suitable.

AREAS COVERED

Treatment outcomes in NTM-PD are unsatisfactory with culture conversion rates varying from 30 to 80% and recurrence rates up to 50%. Possible explanations include our insufficient knowledge and management of host susceptibility factors, poor guideline adherence by physicians, frequent adverse drug reactions demanding premature discontinuation, inadequate drug exposures due to both drug-drug interactions and inter-patient variability in pharmacokinetics, and a lack of pharmacokinetics/pharmacodynamics targets.

EXPERT OPINION

We describe a stepwise approach to NTM-PD treatment, complementing existing guidelines, including recommendations for a multidisciplinary assessment, classification of disease severity, personalized supportive care, antimycobacterial treatment, adjuvant surgery, and host-directed therapies. The recommendations are informed by PubMed literature and the authors' clinical expertise. Recognizing that our experience is shaped within a specialized reference clinic, we acknowledge that some of these recommendations may not be applicable in all settings.

Toward better cures for Mycobacterium abscessus lung disease

SUMMARYThe opportunistic pathogen Mycobacterium abscessus (Mab) causes fatal lung infections that bear similarities-and notable differences-with tuberculosis (TB) pulmonary disease. In contrast to TB, no antibiotic is formally approved to treat Mab disease, there is no reliable cure, and the discovery and development pipeline is incredibly thin. Here, we discuss the factors behind the unsatisfactory cure rates of Mab disease, namely intrinsic resistance and persistence of the pathogen, and the use of underperforming, often parenteral and toxic, repurposed drugs. We propose preclinical strategies to build injectable-free sterilizing and safe regimens: (i) prioritize oral bactericidal antibiotic classes, with an initial focus on approved agents or advanced clinical candidates to provide immediate options for desperate patients, (ii) test drug combinations early, (iii) optimize novel leads specifically for M. abscessus, and (iv) consider pharmacokinetic-pharmacodynamic targets at the site of disease, the lung lesions in which drug tolerant bacterial populations reside. Knowledge and tool gaps in the preclinical drug discovery process are identified, including validated mouse models and computational platforms to enable in vitro mouse-human translation. We briefly discuss recent advances in clinical development, the need for readouts and biomarkers that correlate with cure, and clinical trial concepts adapted to the uniqueness of Mab patient populations for new regimen development. In an era when most pharmaceutical firms have withdrawn from antimicrobial drug discovery, the breakthroughs needed to fill the regimen development pipeline will likely come from partnerships between academia, biotech, pharma, non-profit organizations, and governments, with incentives that reward cooperation.

Nonpharmacological Treatment for Nontuberculous Mycobacterial Pulmonary Disease

Nontuberculous mycobacterial pulmonary disease (NTM-PD) results from the exposure of susceptible hosts to a diverse group of environmental mycobacteria. The emphasis on nonpharmacological strategies is motivated by the widespread presence of NTM in various environments, and the inconsistent success rates of pharmacological treatments. Modifiable factors contributing to NTM-PD development include impaired airway clearance, low body mass index, gastroesophageal reflux disease, and exposure to NTM habitats. This suggests that lifestyle and environmental modifications could affect disease development and progression. The review highlights several modalities that can modify the risk factors. Airway clearance techniques, informed by the "gel-on-brush" model of the bronchial epithelium, aim to enhance mucociliary clearance, and have the potential to alleviate symptoms and improve lung function. The impact of nutritional status is also examined, with a lower body mass index linked to an increased risk and progression of NTM-PD, indicating the importance of targeted nutritional support. Additionally, the theoretical and epidemiological links between gastroesophageal reflux disease and NTM-PD advocate careful management of reflux episodes. Understanding the risk of NTM transmission through environmental exposure to contaminated water and soil is also crucial. Strategies to mitigate this risk, including effective water management and minimizing soil contact, are presented as vital preventive measures. The review supports the inclusion of nonpharmacological treatments within a comprehensive NTM-PD management strategy, alongside conventional pharmacological therapies. This integrated approach seeks to improve the overall understanding and handling of NTM-PD.

Supporting Patients with Nontuberculous Mycobacterial Pulmonary Disease: Ensuring Best Practice in UK Healthcare Settings

Nontuberculous mycobacterial pulmonary disease (NTM-PD) results from opportunistic lung infections by mycobacteria other than Mycobacterium tuberculosis or Mycobacterium leprae species. Similar to many other countries, the incidence of NTM-PD in the United Kingdom (UK) is on the rise for reasons that are yet to be determined. Despite guidelines established by the American Thoracic Society (ATS), the Infectious Diseases Society of America, and the British Thoracic Society, NTM-PD diagnosis and management remain a significant clinical challenge. In this review article, we comprehensively discuss key challenges in NTM-PD diagnosis and management, focusing on the UK healthcare setting. We also propose countermeasures to overcome these challenges and improve the detection and treatment of patients with NTM-PD.

The epidemiology of pulmonary Mycobacterium abscessus species in Japanese population

BACKGROUND

Mycobacterium abscessus species (MABS) is now a most virulent rapidly growing mycobacteria (RGM), and the rapid increase of MABS was recently observed worldwide, including in Japan. Thus, we gathered evidences of the presence of pulmonary MABS in Japanese population from Japanese articles.

METHODS

we searched studies that addressed the isolation of pulmonary non-tuberculous Mycobacteria (NTM) or MABS from clinical respiratory specimens in Japan.

RESULTS

the ratio of MABS to NTM was 3.04% (95% confidence interval [CI]: 2.51-3.68), found using the meta-analysis of single proportions. The estimated mean age of patients infected with MABS was 67.72 years (95% CI: 65.41-70.02), found using the meta-analysis of single means. The estimated proportion of females, never smoker, and the co-infection with Mycobacterium avium complex (MAC) was 66.75% (95% CI: 59.23-73.50), 67.57% (95% CI: 62.43-72.32), and 36.74% (95% CI: 25.30-49.90), respectively. The characteristics of MABS in Japan were considerably different from that in Europe and United States from the perspective of age, gender, and complications, wherein the patients in these countries tended to be younger, had lower number of females, and had more occurrences of hereditary diseases, including cystic fibrosis (CF).

CONCLUSION

we hypothesized that the characteristics of MABS in the Japanese were involved in those of non-CF MABS, and the distribution of gender and age of MABS were similar to that of MAC in the Japanese.

Epidemiological Characteristics of Nontuberculous Mycobacterial Pulmonary Disease in South Korea: A Meta-analysis of Individual Participant Data

BACKGROUND

Despite the global increase in nontuberculous mycobacterial pulmonary disease (NTM-PD), clinical characteristics show geographical variations. We investigated the clinical characteristics of patients with NTM-PD in South Korea.

METHODS

We systematically reviewed articles concerning patients with NTM-PD in South Korea until February 2022. Individual participant data, regardless of treatment, were collected using a standard case report form.

RESULTS

Data of 6,489 patients from 11 hospitals between 2002 and 2019 were analyzed. The mean age was 61.5±11.7 years, of whom 57.7% were women. Mycobacterium avium (41.4%) and Mycobacterium intracellulare (38.4%) comprised most of the causative species, followed by Mycobacterium abscessus subspecies abscessus (8.6%) and M. abscessus subspecies massiliense (7.8%). Bronchiectasis (59.4%) was the most common pulmonary comorbidity. Although reported cases of NTM-PD increased over the years, the proportions of causative species and radiologic forms remained similar. Distinct clinical characteristics were observed according to age and sex. Men were older at the time of diagnosis (median 63.8 years vs. 59.9 years, p<0.001), and had more cavitary lesions than women (38.8% vs. 21.0%, p<0.001). The older group (≥65 years) had higher proportions of patients with body mass index <18.5 kg/m2 (27.4% vs. 18.6%, p<0.001) and cavitary lesions (29.9% vs. 27.6%, p=0.009) than the younger group.

CONCLUSION

We conducted a meta-analysis of the clinical characteristics of patients with NTM-PD in South Korea, and found age- and sex-related differences in disease- specific severity. Further investigation would enhance our comprehension of the nature of the disease, and inherited and acquired host factors.

Therapeutic developments for tuberculosis and nontuberculous mycobacterial lung disease

Tuberculosis (TB) drug discovery and development has undergone nothing short of a revolution over the past 20 years. Successful public-private partnerships and sustained funding have delivered a much-improved understanding of mycobacterial disease biology and pharmacology and a healthy pipeline that can tolerate inevitable attrition. Preclinical and clinical development has evolved from decade-old concepts to adaptive designs that permit rapid evaluation of regimens that might greatly shorten treatment duration over the next decade. But the past 20 years also saw the rise of a fatal and difficult-to-cure lung disease caused by nontuberculous mycobacteria (NTM), for which the drug development pipeline is nearly empty. Here, we discuss the similarities and differences between TB and NTM lung diseases, compare the preclinical and clinical advances, and identify major knowledge gaps and areas of cross-fertilization. We argue that applying paradigms and networks that have proved successful for TB, from basic research to clinical trials, will help to populate the pipeline and accelerate curative regimen development for NTM disease.

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.

The Clinical Course and Prognosis of Patients With Nontuberculous Mycobacterial Pulmonary Disease After Solid Organ Transplantation

BACKGROUND

Due to impaired cell-mediated immunity, solid organ transplantation (SOT) recipients are at increased risk of developing nontuberculous mycobacterial pulmonary disease (NTM-PD). However, the clinical course of NTM-PD in SOT patients and the impact of SOT on the prognosis of NTM-PD remain unclear.

METHODS

We analyzed patients who developed NTM-PD after receiving SOT between January 2001 and December 2020, at a tertiary referral hospital in South Korea. Baseline characteristics, clinical course, and prognosis were evaluated. Propensity score-matched analysis was performed to assess the impact of SOT on long-term survival in patients with NTM-PD.

RESULTS

Among 4,685 SOT recipients over 20 years, 12 patients (median age, 64 years; interquartile range [IQR], 59-67 years; men, 66.7%) developed NTM-PD. Seven (58.3%) and five (41.7%) patients underwent kidney and liver transplantation, respectively, before the diagnosis of NTM-PD. The incidence of NTM-PD was 35.6 cases per 100,000 person-years among kidney transplant recipients and 28.7 cases per 100,000 person-years among liver transplant recipients. The median time between transplantation and the diagnosis of NTM-PD was 3.3 (IQR, 1.5-10.8) years. The most common mycobacterial species was Mycobacterium avium (50.0%). Antibiotic treatment was initiated in five (41.7%) patients, and two patients (40.0%) achieved microbiological cure. Two patients died during a median follow-up of 4.2 (IQR, 2.3-8.8) years and NTM-PD was assumed to be the cause of death in one patient. When matched to patients without a history of SOT, patients with a history of SOT did not show worse survival (P value for log-rank test = 0.62).

CONCLUSION

The clinical course of NTM-PD in SOT recipients was comparable to that of patients without SOT, and SOT did not increase the risk of all-cause mortality in patients with NTM-PD.

Redevelopment after spontaneous sputum conversion in noncavitary nodular bronchiectatic Mycobacterium avium complex lung disease

BACKGROUND

Although spontaneous sputum conversion can occur in noncavitary nodular bronchiectatic (NC-NB) Mycobacterium avium complex lung disease (MAC-LD), little is known about redevelopment after spontaneous conversion. We investigated the redevelopment phenomenon after spontaneous sputum conversion in patients with NC-NB MAC-LD.

MATERIAL AND METHODS

Among patients diagnosed with NC-NB MAC-LD between 2000 and 2013, 140 patients who experienced spontaneous sputum conversion, and whose follow-up duration after conversion was ≥6 months, were enrolled at a tertiary referral center in South Korea. Their medical records were retrospectively reviewed.

RESULTS

Of the 140 patients, 34 (24.3%) underwent redevelopment during the median follow-up period of 71.0 months (interquartile range [IQR], 58.8-87.5). Redevelopment occurred at a median interval of 25.0 months (IQR, 11.5-41.8) after spontaneous sputum conversion. The mean age of the 34 patients with redevelopment was 63.6 years, and 73.5% were women. No statistically significant differences in clinical characteristics were noted between the 34 patients with redevelopment and those with persistent conversion. Among the 34 patients with redevelopment, 6 received treatment at a median interval of 8 months (IQR, 1.5-16.8) after redevelopment. No significant differences in clinical characteristics were noted between the six treated and 28 untreated patients.

CONCLUSION

At least approximately 24% of patients with spontaneous sputum conversion in NC-NB MAC-LD had redevelopment, and a portion of them required treatment. These findings suggest that long-term follow-up is necessary for patients with NC-NB MAC-LD, even those who experience spontaneous sputum conversion.