Clinical significance of the differentiation between Mycobacterium avium and Mycobacterium intracellulare in M avium complex lung disease

Diversity and antimicrobial resistance profiles of Mycobacterium avium complex clinical isolates in Thailand based on whole genome comparative analysis

The Mycobacterium avium complex (MAC) is a group of closely related nontuberculous mycobacteria that can cause various diseases in humans. In this study, genome sequencing, comprehensive genomic analysis, and antimicrobial susceptibility testing of 66 MAC clinical isolates from King Chulalongkorn Memorial Hospital, Bangkok, Thailand were carried out. Whole-genome average nucleotide identity (ANI) revealed the MAC species distribution, comprising 54 (81.8%) M. intracellulare, 6 (9.1%) M. avium, 5 (7.6%) M. colombiense, and 1 (1.5%) M. timonense. Phylogenetic analysis revealed a high diversity of M. intracellulare isolates and their evolutionary relationships which could be divided into 2 subspecies: M. intracellulare subsp. intracellulare and M. intracellulare subsp. chimaera. In addition, M. intracellulare subsp. chimaera mostly clustered in the distinct clades separated from M. intracellulare strains originating from other countries. Most MAC isolates were resistant to linezolid and moxifloxacin based on phenotypic antimicrobial susceptibility testing. Mutations within rrl gene associated with clarithromycin resistance were detected in M. intracellulare and M. colombiense. The pan-genome analysis presented clade-specific proteins for M. intracellulare, such as PE and PPE protein families. This study provides valuable insights into the genomic diversity and antimicrobial resistance profiles of MAC isolates circulating in Thailand, which are useful for clinical management, guiding the development of targeted diagnostic, and treatment strategies for MAC infections.

Ceftriaxone Efficacy for Mycobacterium avium Complex Lung Disease in the Hollow Fiber and Translation to Sustained Sputum Culture Conversion in Patients

BACKGROUND

Only 35.6%-50.8% of patients with Mycobacterium avium complex (MAC) pulmonary disease achieve sustained sputum culture conversion (SSCC) on treatment with the azithromycin-ethambutol-rifabutin standard of care (SOC). We tested the efficacy of ceftriaxone, a β-lactam with a lung-to-serum penetration ratio of 12.18-fold.

METHODS

We mimicked lung concentration-time profiles of 7 ceftriaxone once-daily doses for 28 days in the hollow fiber system model of intracellular MAC (HFS-MAC). Monte Carlo experiments were used for dose selection. We also compared once-daily ceftriaxone monotherapy to 3-drug SOC against 5 MAC clinical isolates in HFS-MAC using γ (kill) slopes, and translated to SSCC rates.

RESULTS

Ceftriaxone killed 1.02-3.82 log10 colony-forming units (CFU)/mL, at optimal dose of 2 g once-daily. Ceftriaxone killed all 5 strains below day 0 versus 2 of 5 for SOC. The median γ (95% confidence interval [CI]) was 0.49 (.47-.52) log10 CFU/mL/day for ceftriaxone and 0.38 (.34-.43) log10 CFU/mL/day for SOC. In patients, the SOC was predicted to achieve SSCC rates (CI) of 39.3% (36%-42%) at 6 months. The SOC SSCC was 50% at 8.18 (3.64-27.66) months versus 3.58 (2.20-7.23) months for ceftriaxone, shortening time to SSCC 2.35-fold.

CONCLUSIONS

Ceftriaxone is a promising agent for creation of short-course chemotherapy.

CT findings as predictive factors for treatment failure in Mycobacterium abscessus complex lung disease: a retrospective cohort study

PURPOSE

Mycobacterium abscessus complex (MABC) commonly causes lung disease (LD) and has a high treatment failure rate of around 50%. In this study, our objective is to investigate specific CT patterns for predicting treatment prognosis and monitoring treatment response, thus providing valuable insights for clinical physicians in the management of MABC-LD treatment.

METHODS

We retrospectively assessed 34 patients with MABC-LD treated between January 2015 and December 2020. CT scores for bronchiectasis, cellular bronchiolitis, consolidation, cavities, and nodules were measured at initiation and after treatment. The ability of the CT scores to predict treatment outcomes was analyzed in logistic regression analyses.

RESULTS

The CT scoring system had excellent inter-reader agreement (all intraclass correlation coefficients, > 0.82). The treatment failure (TF) group (17/34; 50%) had higher cavitation diameter (p = 0.049) and extension (p = 0.041) at initial CT and higher cavitation diameter (p = 0.049) and extension (p =0 .045), consolidation (p = 0.022), and total (p = 0.013) scores at follow-up CT than the treatment success (TS) group. The changes of total score and consolidation score (p = 0.049 and 0.024, respectively) increased in the TF group more than the TS group between the initial and follow-up CT. Multivariable logistic regression analysis showed initial cavitation extension, follow-up consolidation extension, and change in consolidation extension (adjusted odds ratio: 2.512, 2.495, and 9.094, respectively, per 1-point increase; all p < 0.05) were significant predictors of treatment failure.

CONCLUSIONS

A high pre-treatment cavitation extension score and an increase in the consolidation extension score during treatment on CT could be alarm signs of treatment failure requiring tailor the treatment of MABC-LD carefully.

Clinical Predictors of Nontuberculous Mycobacteria Lung Disease and Coisolates of Potential Pathogenic Microorganisms in Noncystic Fibrosis Bronchiectasis

Background

In bronchiectasis, nontuberculous mycobacteria (NTM) lung disease (NTM-LD) is a well-known coexisting infection. However, microorganism coisolates and clinical NTM-LD predictors are poorly studied.

Methods

Patients with bronchiectasis diagnosed by means of computed tomography between January 2017 and June 2020 were screened, using the date of computed tomography as the index date. Those with a major bronchiectasis diagnosis in ≥2 follow-up visits after the index date were enrolled in the study, and NTM-LD occurrence and its association with pneumonia and hospitalization within 1 year were analyzed.

Results

Of the 2717 participants, 79 (2.9%) had NTM-LD diagnosed. The factors associated with NTM-LD included hemoptysis, postinfectious bronchiectasis, a tree-in-bud score ≥2, a modified Reiff score ≥4, and chronic obstructive pulmonary disease (adjusted odds ratios, 1.80, 2.36, 1.78, 2.95, and 0.51, respectively). Compared with patients in the non-NTM group, those with NTM-LD had higher rates of hospitalization (15.9% vs 32.9%; P < .001) and pneumonia (9.8% vs 20.3%; P = .003). Pseudomonas aeruginosa was the most common microorganism in those with NTM-LD and those in the non-NTM group (10.1% vs 7.8%; P = .40). However, compared with those in the non-NTM group, Acinetobacter baumannii and Escherichia coli were more prevalent in patients with NTM-LD (0.7% vs 3.8% [P = .03%] and 1.0% vs 3.8% [P = .05], respectively).

Conclusions

Postinfectious bronchiectasis with hemoptysis, higher radiological involvement, and a tree-in-bud pattern were associated with NTM-LD risk. The rate of A baumannii and E coli coisolation was higher in bronchiectasis populations with NTM-LD.

Formative evaluation and structural analysis of non-tuberculosis mycobacterial biofilm using material pieces

Non-tuberculosis mycobacteria (NTM) can form biofilms on diverse artificial surfaces. In the present study, we induced NTM biofilm formation on materials used in various medical devices, evaluated the total amount of biofilm, and observed the ultrastructure by scanning electron microscopy.

Broad-Spectrum In Vitro Activity of Nα-Aroyl-N-Aryl-Phenylalanine Amides against Non-Tuberculous Mycobacteria and Comparative Analysis of RNA Polymerases

This study investigates the in vitro activity of Nα-aroyl-N-aryl-phenylalanine amides (AAPs), previously identified as antimycobacterial RNA polymerase (RNAP) inhibitors, against a panel of 25 non-tuberculous mycobacteria (NTM). The compounds, including the hit compound MMV688845, were selected based on their structural diversity and previously described activity against mycobacteria. Bacterial strains, including the M. abscessus complex, M. avium complex, and other clinically relevant NTM, were cultured and subjected to growth inhibition assays. The results demonstrate significant activity against the most common NTM pathogens from the M. abscessus and M. avium complexes. Variations in activity were observed against other NTM species, with for instance M. ulcerans displaying high susceptibility and M. xenopi and M. simiae resistance to AAPs. Comparative analysis of RNAP β and β' subunits across mycobacterial species revealed strain-specific polymorphisms, providing insights into differential compound susceptibility. While conservation of target structures was observed, differences in compound activity suggested influences beyond drug-target interactions. This study highlights the potential of AAPs as effective antimycobacterial agents and emphasizes the complex interplay between compound structure, bacterial genetics, and in vitro activity.

Evaluation of mycobacteria infection prevalence and optimization of the identification process in North Sardinia, Italy

IMPORTANCE

Mycobacterial infection is a major threat to public health worldwide. Accurate identification of infected species and drug resistance detection are critical factors in treatment. We focused on shortening the turn-around time of identifying mycobacteria species and antibiotic resistance tests.

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.

Evaluation of the mycobacteria MBT kit for identification of nontuberculous mycobacteria by MALDI-TOF Biotyper (Bruker)

Identification of mycobacteria is crucial for clinical management of patients. The new MBT Mycobacteria kit from the Easy MycoEx protocol (Bruker) is used for the identification of mycobacteria by MALDI Biotyper. The Easy MycoEx protocol was compared to the MycoEx protocol (1) for identification of various mycobacterial isolates collected from samples in 2021, (2) for prospective identification on primary culture during 2 periods. For 44 isolates in MGIT broth, identification rates were high and similar for both protocols (98% vs 95% at cut-off 1.6 and 91% vs 82% at cut-off 1.8). For 42 mycobacteria on Coletsos agar, identification rates were 88% versus 90% at cut-off 1.6 and 76% for both protocols at cut-off 1.8. For slow-growing mycobacteria in MGIT, reproducibility of deposit results was superior with Easy MycoEx. No difference of score was observed between 2 protocols performed on primary culture. Clinical laboratories can easily implement the Easy MycoEx protocol.

Usefulness of the BACES score in nontuberculous mycobacterial pulmonary disease for various clinical outcomes

A uniform prognostic marker is needed for nontuberculous mycobacterial pulmonary disease (NTM-PD) due to the diverse clinical course. We aimed to seek the utility of the BACES score, originally derived to predict all-cause mortality, for various outcomes. To calculate the BACES score, one point was given for each of the following factors: body mass index < 18.5 kg/m², age ≥ 65 years, presence of cavities, elevated erythrocyte sedimentation rate, or male sex. The study included 681 patients, of whom 97 (14.2%), 189 (27.7%), 192 (28.2%), 143 (21.0%), 47 (6.9%), and 13 (1.9%) had BACES scores of 0 to 5. Those with greater BACES scores were more likely to experience dyspnea, body weight loss, and anorexia. With severe disease, the risk of disease progression increased while the rate of treatment culture conversion decreased. After adjustment of comorbidities, higher BACES score was independently associated with the risk of mortality from respiratory causes or infection. As a simple and efficient bedside tool for assessing the severity of NTM-PD, the BACES score has the potential to be utilized as a surrogate marker for uniform severity assessment.

Synthesis and Characterization of Phenylalanine Amides Active against Mycobacterium abscessus and Other Mycobacteria

Nα-2-thiophenoyl-d-phenylalanine-2-morpholinoanilide [MMV688845, Pathogen Box; Medicines for Malaria Venture; IUPAC: (2R)-N-(1-((2-morpholinophenyl)amino)-1-oxo-3-phenylpropan-2-yl)thiophene-2-carboxamide)] is a hit compound, which shows activity against Mycobacterium abscessus (MIC90 6.25-12.5 μM) and other mycobacteria. This work describes derivatization of MMV688845 by introducing a thiomorpholine moiety and the preparation of the corresponding sulfones and sulfoxides. The molecular structures of three analogs are confirmed by X-ray crystallography. Conservation of the essential R configuration during synthesis is proven by chiral HPLC for an exemplary compound. All analogs were characterized in a MIC assay against M. abscessus, Mycobacterium intracellulare, Mycobacterium smegmatis, and Mycobacterium tuberculosis. The sulfone derivatives exhibit lower MIC90 values (M. abscessus: 0.78 μM), and the sulfoxides show higher aqueous solubility than the hit compound. The most potent derivatives possess bactericidal activity (99% inactivation of M. abscessus at 12.5 μM), while they are not cytotoxic against mammalian cell lines.

A marmoset model for Mycobacterium avium complex pulmonary disease

RATIONALE

Mycobacterium avium complex, is the most common nontuberculous mycobacterial respiratory pathogen in humans. Disease mechanisms are poorly understood due to the absence of a reliable animal model for M. avium complex pulmonary disease.

OBJECTIVES

The objectives of this study were to assess the susceptibility, immunologic and histopathologic responses of the common marmoset (Callithrix jacchus) to M. avium complex pulmonary infection.

METHODS

7 adult female marmosets underwent endobronchial inoculation with 108 colony-forming units of M. intracellulare and were monitored for 30 or 60 days. Chest radiograph was assessed at baseline (prior to infection) and at the time of sacrifice (30 days for 3 animals and 60 days for 4 animals), and bronchoalveolar lavage cytokines, histopathology and cultures of the bronchoalveolar lavage, lungs, liver and kidney were assessed at time of sacrifice. Serum cytokines were monitored at baseline and weekly for 30 days for all animals and at 60 days for those alive. Group differences in serum cytokine measurements between those that tested positive versus negative for the M. intracellulare infection were assessed using a series of linear mixed models.

MEASUREMENTS AND MAIN RESULTS

Five of seven animals (two at 30 days and three at 60 days of infection) had positive lung cultures for M. intracellulare. Extra-pulmonary cultures were positive in three animals. All animals appeared healthy throughout the study. All five animals with positive lung cultures had radiographic changes consistent with pneumonitis. At 30 days, those with M. intracellulare lung infection showed granulomatous inflammation, while at 60 days there were fewer inflammatory changes but bronchiectasis was noted. The cytokine response in the bronchoalveolar lavage fluid was uniformly greater in the animals with positive M. intracellulare cultures than those without a productive infection, with greater levels at 30-days compared to 60-days. Similarly, serum cytokines were more elevated in the animals that had positive M. intracellulare cultures compared to those without a productive infection, peaking 14-21 days after inoculation.

CONCLUSION

Endobronchial instillation of M. intracellulare resulted in pulmonary mycobacterial infection in marmosets with a differential immune response, radiographic and histopathologic abnormalities, and an indolent course consistent with M. avium complex lung infection in humans.

Molecular assessment of mycobacterial burden in the treatment of nontuberculous mycobacterial disease

Introduction

Nontuberculous pulmonary disease causes significant morbidity and mortality. Efforts to tackle infections are hampered by the lack of reliable biomarkers for diagnosis, assessment and prognostication. The aim of this study was to develop molecular assays capable of identifying and quantifying multiple nontuberculous mycobacterial (NTM) species and to examine their utility in following individual patients' clinical courses.

Methods

DNA was extracted from 410 sputum samples obtained longitudinally from a cohort of 38 patients who were commencing treatment for either Mycobacterium abscessus or Mycobacterium avium complex or who were patients with bronchiectasis who had never had positive cultures for mycobacteria. NTM quantification was performed with quantitative PCR assays developed in-house.

Results

The molecular assays had high in vitro sensitivity and specificity for the detection and accurate quantification of NTM species. The assays successfully identified NTM DNA from human sputum samples (in vivo sensitivity: 0.86-0.87%; specificity: 0.62-0.95%; area under the curve: 0.74-0.92). A notable association between NTM copy number and treatment (Friedman ANOVA (df)=22.8 (3), p≤0.01 for M. abscessus treatment group) was also demonstrated.

Conclusion

The quantitative PCR assays developed in this study provide affordable, real-time and rapid measurement of NTM burden, with significant implications for prompt management decisions.

Differences in Drug-Susceptibility Patterns between Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium chimaera Clinical Isolates: Prospective 8.5-Year Analysis by Three Laboratories

Background: It has been suggested that Mycobacterium avium, Mycobacterium intracellulare, and M. chimaera have differential drug susceptibility patterns. We prospectively analyzed and compared the drug susceptibility patterns among these species over an 8.5-year period. Methods: A microdilution method (Slomyco^®) was performed for drug susceptibility testing of 402 M. avium, 273 M. intracellulare, and 139 M. chimaera clinical isolates. Results: M. avium showed significantly higher resistance to moxifloxacin, ciprofloxacin, rifampicin, ethambutol, streptomycin, linezolid, cotrimoxazole, and clarithromycin. M. avium also showed higher minimum inhibitory concentrations (MIC) than M. intracellulare and M. chimaera against all drugs except ethionamide, to which M. intracellulare and M. chimaera showed greater resistance. Conclusions: Our series demonstrated differential drug resistance patterns among the most frequent M. avium complex species. M. avium was more resistant than M. intracellulare and M. chimaera versus eight antibiotics and showed greater MIC values to most of the antibiotics studied. These data suggest that knowledge of the local distribution and susceptibility profiles of these pathogens is essential for adequate clinical management.

Identification and drug susceptibility testing of the subspecies of Mycobacterium avium complex clinical isolates in mainland China

OBJECTIVES

The Mycobacterium avium complex (MAC), comprising a series of subspecies, has a worldwide distribution, with differences in drug susceptibility among subspecies. This study aimed to assess the composition of MAC and susceptibility differences among subspecies in mainland China.

METHODS

A total of 287 MAC clinical strains were included in the study. Multitarget sequences were applied to accurately identify subspecies, and a microdilution method was used to evaluate minimum inhibitory concentrations (MICs) among subspecies using Sensititre SLOMYCO plates.

RESULTS

Mycobacterium intracellular (N = 169), Mycobacterium avium (N = 52), Mycobacterium chimaera (N = 22), Mycobacterium marseillense (N = 25), Mycobacterium colombiense (N = 14), Mycobacterium yongonense (N = 4), Mycobacterium vulneris (N = 3) and Mycobacterium timonense (N = 2) were isolated from MAC. Clarithromycin, amikacin and rifabutin showed lower MIC₅₀ and MIC₉₀ values than other drugs, and the resistance rates of clarithromycin, amikacin, linezolid and moxifloxacin were 6.3%, 10.5%, 51.9% and 46.3%, respectively. The resistance rates of clarithromycin and moxifloxacin in the initial treatment group were significantly lower than those in the retreatment group (4.09% vs. 12.94%; 30.41% vs. 75.29%; P < 0.05). Drug susceptibility differences were observed in clarithromycin and moxifloxacin among the five major subspecies (P < 0.05); however, those statistically significant differences disappeared when MACs were divided into two groups according to previous anti-tuberculosis (anti-TB) treatment history.

CONCLUSION

This study revealed that MAC, primarily comprising M. intracellulare, was susceptible to clarithromycin, amikacin and rifabutin. Drug susceptibility among subspecies did not exhibit intrinsic differences in our study. Previous anti-TB treatment patients are more resistant to drugs; thus, attention should be given to those patients in the clinic.

High diversity of clinical Mycobacterium intracellulare in China revealed by whole genome sequencing

Mycobacterium intracellulare is the most common cause of nontuberculous mycobacterial lung disease, with a rapidly growing prevalence worldwide. In this study, we performed comparative genomic analysis and antimicrobial susceptibility characteristics analysis of 117 clinical M. intracellulare strains in China. Phylogenetic analysis showed that clinical M. intracellulare strains had high genetic diversity and were not related to the geographical area. Notably, most strains (76.07%, 89/117) belonged to Mycobacterium paraintracellulare (MP) and Mycobacterium indicus pranii (MIP) in the genome, and we named them MP-MIP strains. These MP-MIP strains may be regarded as a causative agent of chronic lung disease. Furthermore, our data demonstrated that clarithromycin, amikacin, and rifabutin showed strong antimicrobial activity against both M. intracellulare and MP-MIP strains in vitro. Our findings also showed that there was no clear correlation between the rrs, rrl, and DNA gyrase genes (gyrA and gyrB) and the aminoglycosides, macrolides, and moxifloxacin resistance, respectively. In conclusion, this study highlights the high diversity of M. intracellulare in the clinical setting and suggests paying great attention to the lung disease caused by MP-MIP.

Treatment Outcomes of Cavitary Nodular Bronchiectatic-Type Mycobacterium avium Complex Pulmonary Disease

We investigated the treatment outcomes of patients with cavitary nodular bronchiectatic (C-NB)-type Mycobacterium avium complex (MAC) pulmonary disease (PD) via outcome comparisons between the fibrocavitary (FC) and C-NB types treated with guideline-based therapy (GBT) composed of daily three-drug oral antibiotics and injectable aminoglycoside. Additionally, we analyzed whether treatment with oral antibiotics alone would result in acceptable outcomes for the C-NB type. From 2002 to 2019, patients with cavitary MAC-PD who received three-drug oral antibiotics with or without an injectable aminoglycoside for ≥1 year were retrospectively enrolled at a tertiary referral center in South Korea. We compared the rates of culture conversion at 12 months according to the radiological type and treatment regimen. The overall culture conversion rate at 12 months of 154 patients with cavitary MAC-PD who received GBT was 75.3%. Among them, the culture conversion rates of 114 patients with the C-NB type were higher than that of 40 patients with the FC-type (80.7% versus 60.0%, respectively; P = 0.009). Of 166 patients with the C-NB-type treated with oral medications with or without an injectable drug, 83.7% achieved culture conversion at 12 months. The conversion rates of those who received oral medications alone and those treated with oral medications and an injectable aminoglycoside were similar (90.4% versus 80.7%, respectively; P = 0.117). In conclusion, the culture conversion rates of the patients with C-NB type treated with GBT were significantly higher than those of patients with the FC type. Additionally, the C-NB type could be treated with oral medications alone.

Novel Screening System of Virulent Strains for the Establishment of a Mycobacterium avium Complex Lung Disease Mouse Model Using Whole-Genome Sequencing

The establishment of animal models reflecting human Mycobacterium avium complex (MAC) lung disease (LD) pathology has the potential to expand our understanding of the disease pathophysiology. However, inducing sustained infection in immunocompetent mice is difficult since MAC generally shows less virulence and higher genetic variability than M. tuberculosis. To overcome this hurdle, we developed a screening system for identifying virulent MAC strains using whole-genome sequencing (WGS). We obtained nine clinical strains from Mycobacterium avium complex lung disease (MAC-LD) patients and divided them into two groups to make the mixed strain inocula for infection. Intranasal infection with the strain mixture of both groups in BALB/c mice resulted in progressive infection and extensive granuloma formation in the lungs, suggesting the existence of highly pathogenic strains in each group. We hypothesized that the change in the abundance of strain-specific single-nucleotide variants (SNVs) reflects the change in bacterial number of each strain in infected lungs. Based on this hypothesis, we quantified individual strain-specific SNVs in bacterial DNA from infected lungs. Specific SNVs for four strains were detected, suggesting the pathogenicity of these four strains. Consistent with these results, individual infection with these four strains induced a high lung bacterial burden, forming extensive peribronchial granuloma, while the other strains showed a decreased lung bacterial burden. The current method combining mixed infection and WGS accurately identified virulent strains that induced sustained infection in mice. This method will contribute to the establishment of mouse models that reflect human MAC-LD and lead to antimycobacterial drug testing. IMPORTANCE To promote research on Mycobacterium avium complex (MAC) pathogenicity, animal models reflecting human progressive MAC lung disease (MAC-LD) are needed. Because there is high genetic and virulence diversity among clinical MAC strains, choosing a suitable strain is an important process for developing a mouse model. In this study, we developed a screening system for virulent strains in mice by combining mixed infection and whole-genome sequencing analysis. This approach is designed on the hypothesis that in vivo virulence of MAC strains can be examined simultaneously by comparing changes in the abundance of strain-specific single-nucleotide variants in the mouse lungs after infection with mixed strains. The identified strains were shown to induce high bacterial burdens and cause extensive peribronchial granuloma resembling the pulmonary pathology of human MAC-LD. The current method will help researchers develop mouse models that reflect human MAC-LD and will lead to further investigation of MAC pathogenicity.

Impact of chronic co-infection in pulmonary Mycobacterium avium complex disease after treatment initiation

Background

The impact of co-infection with other pathogenic microorganisms after initiation of treatment for Mycobacterium avium complex pulmonary disease (MAC-PD) has not been clearly described. This study sought to clarify the clinical outcomes of co-infection with MAC after antimycobacterial therapy for MAC.

Methods

Co-infection status was defined as the detection of pathogenic microorganisms other than MAC in at least two consecutive sputum cultures 6–24 months after initiation of treatment. Chest computed tomography (CT) findings and culture results were compared between co-infection and MAC alone groups.

Results

The co-infection and MAC alone groups comprised 12 and 36 patients, respectively. The proportion of patients with sputum culture positive for MAC after 24 months of therapy did not differ significantly between the two groups [25% (3/12) vs. 16.7% (6/36); p = 0.671]. The proportion of patients with improved chest CT score after 24 months of starting treatment compared to baseline was significantly lower for the co-infection group than for the MAC alone group [16.7% (2/12) vs. 79.4% (27/34); p < 0.001]. In the co-infection group, median CT score values at 12 and 24 months did not differ from baseline. However, the MAC alone group showed significant improvement at 12 and 24 months compared with baseline.

Conclusions

In the patient group with co-infection of other pathogenic microorganisms after treatment initiation for MAC there was no impact on therapeutic efficacy compared to the MAC alone group. However, therapeutic intervention interfered with improvement in chest CT findings such as nodule formation, bronchiectasis, infiltration, and cavitary lesions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01947-7.

Non-tuberculous mycobacteria isolation from presumptive tuberculosis patients in Lambaréné, Gabon

OBJECTIVE

The prevalence of clinical cases of pulmonary non-tuberculous mycobacteria (NTM) is increasing worldwide. The aim of this study was to determine the proportion and the NTM species isolated from presumptive tuberculosis patients in Lambaréné, Gabon.

METHOD

From January 2018 to December 2020, sputum samples from presumptive TB patients were analysed at the tuberculosis reference laboratory of the Centre de Recherches Médicales de Lambaréné. Two sputum samples were collected per patient, and culture was performed using Bactec MGIT 960. The GenoType Mycobacterium CM/AS was used for NTM isolates confirmation and species differentiation.

RESULTS

Among 1363 sputum samples analysed, 285 (20.9%) were Auramin acid fast bacilli (AFB) smear-positive. NTM were isolated in 137/1363 (10%) of the samples. The most prevalent NTM species was Mycobacterium intracellulare (n=74; 54%).

CONCLUSION

These results show the presence of NTM among presumptive TB patients in Gabon, which could potentially complicate TB diagnosis. This presents a new public health challenge, and emphasises the need to consider NTM in planning the prevention and management of tuberculosis control.

High genetic heterogeneity of Mycobacterium intracellulare isolated from respiratory specimens

Background

M. intracellulare is a frequent causative pathogen of nontuberculous mycobacteria infection that causes infections in the respiratory tract, whose incidence is increasing in many countries. This study aimed at determining the VNTR-based genetic diversity of a collection of 39 M. intracellulare human strains isolated from respiratory specimens over the last 5 years.

Results

The VNTR analysis showed that M. intracellulare strains displayed a high genetic diversity, indicating that the M. intracellulare genotypes are quite heterogeneous in our geographical area. Moreover, a comparison with VNTR profiles of strains from other countries confirmed that genotypes of clinical strains of M. intracellulare are not related to geographical origin.

Conclusions

VNTR typing has proved to be a highly discriminatory method for better understanding the molecular epidemiology of M. intracellulare.

Life-threatening Mycobacterium intracellulare pleuritis in an immunocompetent host: Case reports

RATIONALE

Nontuberculous mycobacteria (NTM)-associated pleuritis is a very rare disease. Here, we describe 2 cases of life-threatening Mycobacterium intracellulare-associated pleuritis in immunocompetent hosts.

PATIENT CONCERNS

A 78-year-old man with sudden onset-onset dyspnea (case 1) and an 80-year-old man with cough, sputum and fever (case 2) presented to our emergency room.

DIAGNOSES

Both the patients were diagnosed with Mycobacterium intracellulare-associated pleuritis.

INTERVENTION

In case 1, the patient underwent intubation with mechanical ventilation due to hypoxemic respiratory failure. Daily azithromycin, rifampin and ethambutol, and intravenous amikacin 3 times a week was administered. In case 2, the patient received daily azithromycin, rifampin and ethambutol, and intravenous amikacin 3 times a week.

OUTCOMES

In case 1, after receiving NTM treatment for 14 months, NTM-associated pleuritis was cured, with radiologic improvement. In case 2, however, bronchopleural fistula was developed. Despite tube drainage, air leak continued. The patient refused surgical management and eventually died of respiratory failure.

LESSONS

Pleural effusion arising from NTM lung disease located in the subpleural area should be considered a possible cause of NTM-associated pleuritis. Drainage and a multidrug regimen are required to treat NTM, and surgical treatment should be considered when complications occur.

Population-Based Distribution of Mycobacterium avium and Mycobacterium intracellulare in Japan

This study aimed to clarify the population-based distributions of Mycobacterium avium and Mycobacterium intracellulare in Japan. We conducted a combined analysis of the national insurance claim and microbiological databases. The incidence rates of M. avium by province were similar throughout the country, with some exceptions, such as in Okinawa, probably because the bathing customs are different from those in mainland Japan. In contrast, M. intracellulare showed a gradual increase from the central part of the country to the southwestern region, with precise gradation, which may indicate infection sources in the natural environment. This study found that assessment of the infection route of M. intracellulare in the natural environment, which is similar to the distribution of M. intracellular patients, is warranted. In conclusion, improvement of the household environment could decrease the incidence of M. avium, while environmental countermeasures will be required to decrease the incidence of M. intracellulare.

Factors affecting in-hospital mortality of non-tuberculous mycobacterial pulmonary disease

Background

The incidence and prevalence of non-tuberculous mycobacterial pulmonary disease (NTM-PD) are reportedly increasing in many parts of the world. However, there are few published data on NTM-PD-related death. Using data from a national inpatient database in Japan, we aimed in this study to identify the characteristics of patients with NTM-PD and clinical deterioration and to identify risk factors for in-hospital mortality.

Methods

We examined data from the Diagnosis Procedure Combination (DPC) database in Japan from July 2010 to March 2014. We extracted data for HIV-negative NTM-PD patients who required unscheduled hospitalization. We evaluated these patients’ characteristics and performed multivariable logistic regression analysis to identify risk factors for all-cause in-hospital mortality.

Results

A total of 16,192 patients (median age: 78 years; women: 61.2%) were identified. The median body mass index (BMI) was 17.5 kg/m² (IQR 15.4–20.0). All cause In-hospital death occurred in 3166 patients (19.6%). The median BMI of the patients who had died was 16.0 kg/m² (IQR 14.2–18.4). Multivariable analysis revealed that increased mortality was associated with male sex, lower BMI, lower activities of daily living scores on the Barthel index, hemoptysis, and comorbidities, including pulmonary infection other than NTM, interstitial lung disease, pneumothorax, and malignant disease.

Conclusions

We found associations between being underweight and having several comorbidities and increased in-hospital mortality in patients with NTM-PD. Preventing weight loss and management of comorbidities may have a crucial role in improving this disease’s prognosis.

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.

Association between serum anti-glycopeptidolipid-core IgA antibody titers and clinical characteristics of Mycobacterium avium complex pulmonary disease

OBJECTIVES

Mycobacterium avium complex pulmonary disease (MAC-PD) can be serologically diagnosed according to the presence of anti-glycopeptidolipid (GPL)-core IgA antibodies. However, few studies have examined the association between serum anti-GPL-core IgA antibody titers and the clinical characteristics of patients with MAC-PD.

METHODS

From April 2014 to June 2019, the levels of anti-GPL-core IgA antibodies in 489 MAC-PD patients were determined at the current institute. Of them, 89 patients fulfilled the criteria of the American Thoracic Society and the Infectious Diseases Society of America statement on the diagnosis, treatment, and prevention of nontuberculous mycobacterial diseases. Patients were categorized into the antibody strong-positive (n = 27), weak-positive (n = 32), and negative (n = 30) groups according to their serum anti-GPL-core IgA antibody results. Their clinical characteristics were retrospectively compared.

RESULTS

Disease progression requiring treatment and extensive radiological findings were significantly abundant in the strong-positive group compared with the weak-positive group. Clinical characteristics of the antibody weak-positive and negative groups did not significantly differ.

CONCLUSIONS

The findings revealed that serum anti-GPL-core IgA antibody titers are useful for diagnosing MAC-PD and also for predicting the risk of exacerbation.

Difference in drug susceptibility distribution and clinical characteristics between Mycobacterium avium and Mycobacterium intracellulare lung diseases in Shanghai, China

Introduction. Mycobacterium avium complex (MAC) has been reported as the most common aetiology of lung disease involving nontuberculous mycobacteria.Hypothesis. Antimicrobial susceptibility and clinical characteristics may differ between Mycobacterium avium and Mycobacterium intracellulare.Aim. We aimed to evaluate the differences in antimicrobial susceptibility profiles between two major MAC species (Mycobacterium avium and Mycobacterium intracellulare) from patients with pulmonary infections and to provide epidemiologic data with minimum inhibitory concentration (MIC) distributions.Methodology. Between January 2019 and May 2020, 45 M. avium and 242 M. intracellulare isolates were obtained from Shanghai Pulmonary Hospital. The demographic and clinical characteristics of patients were obtained from their medical records. The MICs of 13 antimicrobials were determined for the MAC isolates using commercial Sensititre SLOWMYCO MIC plates and the broth microdilution method, as recommended by the Clinical and Laboratory Standards Institute (CLSI; Standards M24-A2). MIC₅₀ and MIC₉₀ values were derived from the MIC distributions.Results. M. intracellulare had higher resistance rates than M. avium for most tested antimicrobials except clarithromycin, ethambutol, and ciprofloxacin. Clarithromycin was the most effective antimicrobial against both the M. avium (88.89 %) and M. intracellulare (91.32 %) isolates, with no significant difference between the species (P=0.601). The MIC₉₀ of clarithromycin was higher for M. avium (32 µg ml^-1) than M. intracellulare (8 µg ml^-1). The MIC₅₀ of rifabutin was more than four times higher for M. intracellulare (1 µg ml^-1) than M. avium (≤0.25 µg ml^-1). The percentages of patients aged >60 years and patients with sputum, cough, and cavitary lesions were significantly higher than among patients with M. intracellulare infection than M. avium infections.Conclusions. The pulmonary disease caused by distinct MAC species had different antimicrobial susceptibility, symptoms, and radiographic findings.

Exacerbating factors in elderly patients with Mycobacterium avium complex pulmonary disease

No previous studies have examined Mycobacterium avium complex pulmonary disease (MAC-PD) in only elderly patients ⩾75 years old. Here, we investigated the exacerbating factors of MAC-PD in elderly patients and clarified cases that can be followed up without MAC medication. From April 2011 to March 2019, 126 advanced aged patients at our institute were newly diagnosed with MAC-PD, and could be observed based on radiological findings for over a year. Their medical records were retrospectively examined for clinical and radiological findings at the time of diagnosis and 1 year later. To identify the predictors of exacerbation, clinical characteristics of 109 treatment-naïve patients were compared between exacerbated and unchanged groups. Additionally, the unchanged group was followed for one more year. In the current study, positive acid-fast bacilli smears from the sputum test, the presence of cavitary lesions and extensive radiological findings, particularly abnormal shadows in ⩾3 lobes, were predictive of exacerbation among treatment-naïve elderly MAC-PD patients. In the unchanged group, <10% showed exacerbation of radiological findings within the subsequent year. In conclusion, if the sputum smear is negative, no cavitary lesions are present, and abnormal shadows are restricted to ⩽2 lobes, elderly patients with MAC-PD may remain untreated for a few years.

Cavity formation and its predictors in noncavitary nodular bronchiectatic Mycobacterium avium complex pulmonary disease

INTRODUCTION

The temporal dynamics of cavity formation in patients with the noncavitary nodular bronchiectatic (NC-NB) form of Mycobacterium avium complex pulmonary disease (MAC-PD) have not yet been well described. We aimed to investigate the development of new cavities in the NC-NB form of MAC-PD.

METHODS

Of the patients diagnosed with NC-NB-type MAC-PD between 2002 and 2013 and followed-up until July 2018 at a tertiary referral center in South Korea, we identified 589 patients who underwent follow-up chest computed tomography at least once after the diagnosis and retrospectively analysed their medical records.

RESULTS

The patients' mean age was 62.0 years, 64.7% were women. During the median follow-up of 3.8 years (interquartile range [IQR] 1.7-5.9), new cavity formation was noted in 51 (8.7%) patients. The median interval between the diagnosis of NC-NB MAC-PD and cavity formation was 3.7 years (IQR 1.8-5.4), with a constant occurrence over time. The Cox regression analysis showed that a history of pulmonary tuberculosis (adjusted hazard ratio [HR] 1.85; 95% confidence interval [CI] 1.06-3.23; P = 0.030) and M. intracellulare as the causative organism (adjusted HR 2.03; 95% CI 1.15-3.59; P = 0.014) were independently associated with new cavity formation.

CONCLUSIONS

New cavity formation was noted in 8.7% of the patients with NC-NB MAC-PD in approximately 4 years after diagnosis, particular in those infected with M. intracellulare and those with a previous history of tuberculosis.

Aspergillus isolation in nontuberculous mycobacterial pulmonary disease: Associated with antimycobacterial treatment initiation but not response

PURPOSE

Chronic pulmonary aspergillosis is a serious complication of nontuberculous mycobacterial pulmonary disease (NTM-PD), and diagnosis remains challenging. The present study examined associations between the respiratory isolation of Aspergillus and the clinical characteristics and treatment outcomes of patients with NTM-PD.

METHODS

All patients meeting NTM-PD criteria as defined by the ATS/IDSA statement, with at least one respiratory sample cultured for fungi, were included in this retrospective cohort analysis. Patients with at least one respiratory sample isolating Aspergillus were compared to patients who did not isolate Aspergillus. The primary outcomes were culture conversion and radiologic evolution 12 months after NTM-PD treatment initiation.

RESULTS

During a 12 year period, 497 patients meeting the inclusion criteria were seen in our tertiary care center, of whom 130 grew Aspergillus. Median follow up after NTM-PD diagnosis was 46 months. Inhaled corticosteroid use, a nodular-bronchiectatic CT pattern and NTM-PD treatment initiation were more frequent in patients who isolated Aspergillus compared to those who did not (p-value respectively 0.01, 0.03 and < 0.001). Rates of culture conversion (63.0% vs. 62.2%, respectively; p-value 1) and radiologic evolution (improvement or stability in 69.7% vs. 77.2%, respectively; p-value 0.25) were not significantly different between treatment groups. Likewise, culture reversion rate and 5-year mortality were not significantly different. Additionally, A. fumigatus and repeated detection of Aspergillus were not associated with treatment outcomes.

CONCLUSION

There was no association between respiratory isolation of Aspergillus and NTM-PD treatment outcomes in this cohort. However, treatment for NTM-PD was initiated more frequently in patients who isolated Aspergillus.

Development of an in vivo-mimic silkworm infection model with Mycobacterium avium complex

In vivo-mimic silkworm infection models with Mycobacterium avium and Mycobacterium intracellulare were newly established to evaluate the therapeutic effects of anti-M. avium complex (MAC) antibiotics. Silkworms raised at 37°C died within 72 hours of an injection of M. avium or M.intracellulare (2.5 × 10⁷ colony-forming unit (CFU)/larva·g) into the hemolymph. Clinical anti-mycobacterial (tuberculosis) antibiotics were evaluated under these conditions. Clarithromycin, kanamycin, streptomycin, amikacin, and ciprofloxacin exerted therapeutic effects in a dose-dependent manner, which was consistent with those in the mouse model. Furthermore, three effective actinomycete culture broths were selected in the screening program of our microbial broth library using the silkworm model, and four active metabolites, ohmyungsamycins A and B (1 and 2), chartreusin (3), and griseoviridin (4), were identified. Among these compounds, 1 showed the lowest 50% effective dose (ED₅₀) value (8.5 µg/larva·g), while 3 had the best ED₅₀/minimum inhibitory concentration (MIC) ratio (7.4). These results indicate that silkworm models are a useful tool for identifying anti-MAC antibiotics candidates with veritable therapeutic effects.

First line treatment selection modifies disease course and long-term clinical outcomes in Mycobacterium avium complex pulmonary disease

The combination of rifamycin (RFP), ethambutol (EB), and macrolides is currently the standard regimen for treatment of Mycobacterium avium complex pulmonary disease (MAC-PD). However, poor adherence to the standardized regimens recommended by current guidelines have been reported. We undertook a single-centred retrospective cohort study to evaluate the long-term outcomes in 295 patients with MAC-PD following first line treatment with standard (RFP, EB, clarithromycin [CAM]) or alternative (EB and CAM with or without fluoroquinolones (FQs) or RFP, CAM, and FQs) regimens. In this cohort, 80.7% were treated with standard regimens and 19.3% were treated with alternative regimens. After heterogeneity was statistically corrected using propensity scores, outcomes were superior in patients treated with standard regimens. Furthermore, alternative regimens were significantly and independently associated with sputum non-conversion, treatment failure and emergence of CAM resistance. Multivariate cox regression analysis revealed that older age, male, old tuberculosis, diabetes mellitus, higher C-reactive protein, and cavity were positively associated with mortality, while higher body mass index and M. avium infection were negatively associated with mortality. These data suggest that, although different combination regimens are not associated with mortality, first line administration of a standard RFP + EB + macrolide regimen offers the best chance of preventing disease progression in MAC-PD patients.

Methods for Detecting Mycobacterial Mixed Strain Infections-A Systematic Review

Mixed strain infection (MSI) refers to the concurrent infection of a susceptible host with multiple strains of a single pathogenic species. Known to occur in humans and animals, MSIs deserve special consideration when studying transmission dynamics, evolution, and treatment of mycobacterial diseases, notably tuberculosis in humans and paratuberculosis (or Johne's disease) in ruminants. Therefore, a systematic review was conducted to examine how MSIs are defined in the literature, how widespread the phenomenon is across the host species spectrum, and to document common methods used to detect such infections. Our search strategy identified 121 articles reporting MSIs in both humans and animals, the majority (78.5%) of which involved members of the Mycobacterium tuberculosis complex, while only a few (21.5%) examined non-tuberculous mycobacteria (NTM). In addition, MSIs exist across various host species, but most reports focused on humans due to the extensive amount of work done on tuberculosis. We reviewed the strain typing methods that allowed for MSI detection and found a few that were commonly employed but were associated with specific challenges. Our review notes the need for standardization, as some highly discriminatory methods are not adapted to distinguish between microevolution of one strain and concurrent infection with multiple strains. Further research is also warranted to examine the prevalence of NTM MSIs in both humans and animals. In addition, it is envisioned that the accurate identification and a better understanding of the distribution of MSIs in the future will lead to important information on the epidemiology and pathophysiology of mycobacterial diseases.

General Overview of Nontuberculous Mycobacteria Opportunistic Pathogens: Mycobacterium avium and Mycobacterium abscessus

Nontuberculous mycobacteria (NTM) are emerging human pathogens, causing a wide range of clinical diseases affecting individuals who are immunocompromised and who have underlying health conditions. NTM are ubiquitous in the environment, with certain species causing opportunistic infection in humans, including Mycobacterium avium and Mycobacterium abscessus. The incidence and prevalence of NTM infections are rising globally, especially in developed countries with declining incidence rates of M. tuberculosis infection. Mycobacterium avium, a slow-growing mycobacterium, is associated with Mycobacterium avium complex (MAC) infections that can cause chronic pulmonary disease, disseminated disease, as well as lymphadenitis. M. abscessus infections are considered one of the most antibiotic-resistant mycobacteria and are associated with pulmonary disease, especially cystic fibrosis, as well as contaminated traumatic skin wounds, postsurgical soft tissue infections, and healthcare-associated infections (HAI). Clinical manifestations of diseases depend on the interaction of the host's immune response and the specific mycobacterial species. This review will give a general overview of the general characteristics, vulnerable populations most at risk, pathogenesis, treatment, and prevention for infections caused by Mycobacterium avium, in the context of MAC, and M. abscessus.

Predictors of radiological aggravations of pulmonary MAC disease

Background and objectives

The number of patients with pulmonary Mycobacterium avium complex (MAC) disease is increasing worldwide, especially among middle-aged women and never-smokers.

However, little is known about the factors causing exacerbations of pulmonary MAC disease in untreated patients. The aim of the present study was to identify the predictors of radiological aggravations of pulmonary MAC disease.

Methods

From April 2011 to December 2018, 238 MAC patients at our institute were newly diagnosed with pulmonary MAC disease according to the 2007 American Thoracic Society/Infectious Disease Society guideline. Their medical records were examined retrospectively for their clinical findings. The radiological findings at the time of the diagnosis and 1 year later were evaluated. To identify the predictors of radiological aggravation, multivariable analysis was performed with the data of 167 treatment-naïve patients.

Results

Female, never-smoker, and nodular/bronchiectatic (NB) type were predominant in patients with pulmonary MAC disease. Univariate analysis of data from treatment-naïve subjects showed that no lung diseases other than MAC, extensive radiological findings, and a positive acid-fast bacilli (AFB) smear were significantly associated with radiological aggravations. On multivariate analysis, the radiological factor (larger affected area) and absence of other lung disease were significantly associated with radiological aggravations. In particular, the presence of abnormal shadows in more than 3 lobes was significantly associated with radiological aggravations.

Conclusions

In this study, the presence of extensive radiological findings and the absence of lung diseases other than MAC were predictors of radiological aggravations of treatment-naïve pulmonary MAC disease. In particular, the presence of abnormal shadows in more than 3 lobes was significantly associated with radiological aggravations.

Clinical significance of anti-glycopeptidolipid-core IgA antibodies in patients newly diagnosed with Mycobacterium avium complex lung disease

BACKGROUND

Although recent studies have identified anti-glycopeptidolipid (GPL)-core IgA antibodies as a serodiagnostic test for Mycobacterium avium complex lung disease (MAC-LD), this test shows insufficient sensitivity. This study aimed to determine the clinical utility of these antibodies in assessing disease progression and the clinical characteristics of MAC-LD patients with negative antibody results.

METHODS

We retrospectively reviewed the medical records of consecutive newly diagnosed, untreated MAC-LD patients in two referral hospitals. We evaluated the association of anti-GPL-core IgA antibody results with disease progression requiring treatment and the factors associated with negative antibody results.

RESULTS

In total, 229 patients (161 females; median age, 71 years; 185 with nodular/bronchiectatic disease phenotype; 69 with cavitary lesions) were enrolled; 146 patients (64%) were anti-GPL-core IgA antibody-positive. Radiological severity scores were associated with anti-GPL-core IgA antibody titers. During the median 364-day follow-up, 114 patients (49.8%) required treatment. Multivariate Cox proportional hazards analysis showed that positive anti-GPL-core IgA antibody results, a younger age, the absence of malignancy, and the presence of cavitary lesions were associated with disease progression requiring treatment. Multivariate logistic analysis revealed that significant factors related to the negative antibody results included underlying pulmonary disease, lower radiological scores, chronic sinusitis, and macrolide monotherapy.

CONCLUSION

In addition to cavitary lesions, anti-GPL-core IgA antibody positivity was associated with disease progression requiring treatment. Physicians should carefully use anti-GPL-core IgA antibody results for the diagnosis of patients with underlying pulmonary disease, chronic sinusitis, macrolide monotherapy, and lower radiological severity.

Extensive Lung Resection for Nontuberculous Mycobacterial Lung Disease With Multilobar Lesions

BACKGROUND

Nontuberculous mycobacterial lung disease often spreads to multiple lobes, and extensive lung resection (ELR) is sometimes required to control the disease. The safety and feasibility of ELR for nontuberculous mycobacterial lung disease remain unclear, however.

METHODS

This retrospective study included patients with nontuberculous mycobacterial lung disease who underwent adjuvant lung resection. Characteristics were compared between patients who underwent ELR and those who underwent simple anatomic lung resection (SALR). The outcome data were analyzed by a Cox regression analysis.

RESULTS

A total of 146 patients underwent ELR (n = 54) or SALR (n = 92). ELR was associated with a longer operative time (306 vs 237 minutes; P < .001) and higher incidence of prolonged air leak (17% vs 3.3%; P = .016) than SALR. Rates of mortality, sputum culture conversion (positive to negative), and microbiological recurrence did not differ markedly between the groups. In the multivariate analysis, ELR was not a significant risk factor for an unfavorable outcome after nontuberculous mycobacterial lung disease surgery (hazard ratio, 2.23; 95% confidence interval, 0.82-6.03; P= .11).

CONCLUSIONS

ELR for nontuberculous mycobacterial lung disease has some drawbacks compared with SALR but seems as safe and feasible as SALR. ELR may provide improved disease control in some cases of nontuberculous mycobacterial lung disease with multilobar lesions.

Serum Krebs von den Lungen-6 level in the disease progression and treatment of Mycobacterium avium complex lung disease

BACKGROUND AND OBJECTIVE

The lack of useful biomarkers reflecting the disease state limits the management of Mycobacterium avium complex lung disease (MAC-LD). We clarified the associations between serum KL-6 level, disease progression and treatment response.

METHODS

Resected lung tissues from MAC-LD patients were immunostained for KL-6. We compared serum KL-6 levels between MAC-LD and healthy control or bronchiectasis patients without nontuberculous mycobacterial lung disease (NTM-LD). Serum KL-6 level was assessed in a prospective observational study at Keio University Hospital between May 2012 and May 2016. We investigated associations between serum KL-6 level and disease progression and treatment response in patients untreated for MAC-LD on registration (n = 187).

RESULTS

The KL-6⁺ alveolar type 2 cell population in the lung and serum KL-6 level were significantly higher in MAC-LD patients than in controls. Serum KL-6 level in bronchiectasis patients without NTM-LD showed no significant increase. Of the 187 patients who did not receive treatment on registration, 53 experienced disease progression requiring treatment. Multivariable Cox analysis revealed that the serum KL-6 level (aHR: 1.18, P = 0.005), positive acid-fast bacilli smear (aHR: 2.64, P = 0.001) and cavitary lesions (aHR: 3.01, P < 0.001) were significantly associated with disease progression. The change in serum KL-6 (ΔKL-6) was significantly higher in the disease progression group; it decreased post-treatment, reflecting the negative sputum culture conversion.

CONCLUSION

Serum KL-6 level is associated with disease progression and treatment response. Longitudinal assessment combined with AFB smear status and presence of cavitary lesions may aid MAC-LD management.

Clinical relevance and diagnosis of nontuberculous mycobacterial pulmonary disease in populations at risk

The lungs are the most common disease site of nontuberculous mycobacteria (NTM). However, the isolation of NTM in a respiratory specimen does not indicate lung disease (LD). Differentiation between NTM colonization and NTM-LD remains challenging. In this brief review, we summarize the clinical impact of NTM-LD on morbidity and mortality in high-risk populations. The diagnosis criteria for NTM-LD-including clinical features, radiological presentations, and microbiological evidence-are also reviewed, according to the latest American Thoracic Society (ATS)/Infectious Disease Society of America (IDSA) guideline and the British Thoracic Society (BTS) guideline. However, the diagnosis of NTM-LD does not necessitate the initiation of anti-NTM treatment. Both environmental, host, and bacterial factors should be considered to identify patients that require NTM-LD treatment.