Pulmonary sequestration infected with nontuberculous mycobacteria: a report of two cases and literature review

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.

Unravelling the mystery of a rare infection: a challenging case of pulmonary sequestration with Mycobacterium avium complex and the importance of a thorough microbiological investigation

Pulmonary sequestration is a rare congenital condition. It is a dysplastic lung tissue with a separate systemic blood supply and without a bronchial tree connection. The emergence of a superimposed infection can lead to its diagnosis, such as Staphylococcus aureus, Pseudomonas aeruginosa, Nocardia asteroids and Aspergillus sp pneumonia. Mycobacterium avium complex (MAC) superimposed disease is exceedingly rare. We report a case of a man in his third decade without known medical disorders presenting with a persistent cough. After an extensive microbiological workup, an MAC infection was diagnosed. An elevated carbohydrate antigen 19-9 (CA 19-9) was also noted. He was treated with antimycobacterial therapy and lobectomy resulting in clinical improvement and CA19-9 normalisation. This case illustrates the value of comprehensive microbiological investigations in patients with chronic respiratory symptoms and imaging findings that are not typical of bacterial pneumonia. Clinical studies remain needed to investigate the utility of CA 19-9 in a scoring system to guide MAC therapy.

Comparison of clinical outcomes of pulmonary sequestration in adults between surgery and non-surgery groups

BACKGROUND

Pulmonary sequestration (PS) is a rare congenital lung malformation that can be incidentally diagnosed in adulthood. The natural course of PS in adults is scarcely known.

METHODS

In this retrospective cohort study, medical records and imaging results of adult patients diagnosed with PS between 1994 and 2019 were reviewed. Diagnoses of PS were confirmed by histopathological findings in resected cases, while non-resected cases were diagnosed based on the presence of anomalous systemic arterial supply and abnormal lung parenchyma on enhanced chest computed tomography (CT).

RESULTS

Among 104 patients with PS, the median age at diagnosis was 40.5 years, and 69 (66.3%) patients were asymptomatic. Patients in the surgery group were significantly younger (38.6 vs. 45.3 years, respectively, P=0.016), were more likely to be symptomatic initially (51.6% vs. 28.6%, respectively, P=0.015), and had larger PS (90.0 vs. 66.3 mm, respectively, P<0.001) than the non-surgery group. Of the patients in the surgery group, 29.0% (18/62) experienced postoperative complications. In the surgically resected cases, infections were only detected in intralobar PS, not in extralobar PS. Among 25 subjects without initial symptoms in the non-surgery group, 24 (96.0%) remained asymptomatic at the last follow-up.

CONCLUSIONS

Adults with PS tended to undergo resection if they were young, symptomatic, and had large PS (a median diameter of 90.0 mm). Almost all subjects who were initially asymptomatic and did not undergo surgery remained asymptomatic at the last follow-up. Therefore, considering the indolent course of PS, initially asymptomatic adults with PS could be followed up without surgery.

A rabbit model to study antibiotic penetration at the site of infection for non-tuberculous mycobacterial lung disease: macrolide case study

Nontuberculous mycobacterial pulmonary disease (NTM-PD) is a potentially fatal infectious disease requiring long treatment duration with multiple antibiotics and against which there is no reliable cure. Among the factors that have hampered the development of adequate drug regimens is the lack of an animal model that reproduces the NTM lung pathology required for studying antibiotic penetration and efficacy. Given the documented similarities between tuberculosis and NTM immunopathology in patients, we first determined that the rabbit model of active tuberculosis reproduces key features of human NTM-PD and provides an acceptable surrogate model to study lesion penetration. We focused on clarithromycin, a macrolide and pillar of NTM-PD treatment, and explored the underlying causes of the disconnect between its favorable potency and pharmacokinetics, and inconsistent clinical outcome. To quantify pharmacokinetic-pharmacodynamic target attainment at the site of disease, we developed a translational model describing clarithromycin distribution from plasma to lung lesions, including the spatial quantitation of clarithromycin and azithromycin in mycobacterial lesions of two patients on long-term macrolide therapy. Through clinical simulations, we visualized the coverage of clarithromycin in plasma and four disease compartments, revealing heterogeneous bacteriostatic and bactericidal target attainment depending on the compartment and the corresponding potency against nontuberculous mycobacteria in clinically relevant assays. Overall, clarithromycin's favorable tissue penetration and lack of bactericidal activity indicated that its clinical activity is limited by pharmacodynamic rather than pharmacokinetic factors. Our results pave the way towards the simulation of lesion pharmacokinetic-pharmacodynamic coverage by multi-drug combinations, to enable the prioritization of promising regimens for clinical trials.

Pulmonary Sequestration Associated with Actinomycosis: A Case Report

Background: Bronchopulmonary sequestration is a rare congenital malformation of the lower respiratory tract; it consists of a nonfunctioning mass of lung tissue that is irrigated by an anomalous systemic artery. The association with Actinomyces superinfection has not been well established. Methods: We present the case of a 35-year-old woman with a history of recurrent episodes of pneumonia. Based on radiological and histopathological examination, she was diagnosed with intralobar bronchopulmonary sequestration associated with Actinomyces infection. Promoting clinical suspicion is essential to diagnose pulmonary actinomycosis in patients with recurrent pneumonia, to improve early recognition and timely management.

Atherosclerosis of aberrant arteries from the left gastric artery into the right intralobar pulmonary sequestration complicated by mycobacterial epithelioid cell granuloma

Vascular changes observed in intralobar pulmonary sequestration (PS) have been reported to be similar to those observed in pulmonary hypertension (PH). However, atherosclerosis in the pulmonary artery, which is one of the characteristic arterial changes of PH, has scarcely been reported in PS. Here, we report this unique manifestation in a 66-year-old man, in whom an intralobar PS fed by an aberrant artery branching from the left gastric artery had been identified 10 years earlier, and who was diagnosed with pneumonia after having symptoms of fever and cough. He was treated by lobectomy of the lower lobe of his right lung. Subsequently, a culture test of the fluid from the sequestrated lung was performed, which identified Mycobacterium avium. Subsequent pathological examination of the sequestrated lung demonstrated multiple epithelioid cell granulomas. Furthermore, atherosclerosis of the aberrant artery was also found, which may be associated with his advanced age. This is an extremely rare case of right intralobar PS supplied by aberrant artery with atherosclerosis originating from left gastric artery passing over the diaphragm.

Mycobacterium abscessus Lung Infection: A Case Report

-

Susceptibility of Mycobacterium abscessus to antimycobacterial drugs in preclinical models

Over the last 10 years, Mycobacterium abscessus group strains have emerged as important human pathogens, which are associated with significantly higher fatality rates than any other rapidly growing mycobacteria. These opportunistic pathogens are widespread in the environment and can cause a wide range of clinical diseases, including skin, soft tissue, central nervous system, and disseminated infections; by far, the most difficult to treat is the pulmonary form. Infections with M. abscessus are often multidrug-resistant (MDR) and require prolonged treatment with various regimens and, many times, result in high mortality despite maximal therapy. We report here the evaluation of diverse mouse infection models for their ability to produce a progressive high level of infection with M. abscessus. The nude (nu/nu), SCID (severe combined immunodeficiency), gamma interferon knockout (GKO), and granulocyte-macrophage colony-stimulating factor (GMCSF) knockout mice fulfilled the criteria for an optimal model for compound screening. Thus, we set out to assess the antimycobacterial activity of clarithromycin, clofazimine, bedaquiline, and clofazimine-bedaquiline combinations against M. abscessus-infected GKO and SCID murine infection models. Treatment of GKO and SCID mice with a combination of clofazimine and bedaquiline was the most effective in decreasing the M. abscessus organ burden.