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

Patient with Adult T-cell Leukemia and Lung Infection Caused by Mycobacterium abscessus: Successful Treatment with Intensive Chemotherapy Followed by Haploidentical Hematopoietic Stem Cell Transplantation

A 63-year-old woman with adult T-cell leukemia (ATL) lymphomatous type developed a mild dry cough. Computed tomography revealed lung lesions with a tree-in-bud appearance during intensive chemotherapy. Antibodies against Mycobacterium avium complex were positive. Bronchoalveolar lavage culture showed growth of M. abscessus complex. Finally, M. abscessus subsp. massiliense was also identified. Sequential use of antimicrobials, including macrolides, was introduced during intensive chemotherapy, and the patient successfully underwent allogeneic hematopoietic stem cell transplantation (AHSCT). This is the first case report of a patient with ATL complicated by M. massiliense lung infection, who was successfully treated with haploidentical AHSCT using various combinations of antimicrobials.

Clinical Characteristics and Treatment Outcomes of Pulmonary Diseases Caused by Coinfections With Multiple Nontuberculous Mycobacterial Species

BACKGROUND

Coinfections with multiple nontuberculous mycobacterial (NTM) species have not been widely studied. We aimed to evaluate the clinical characteristics and treatment outcomes in patients with NTM-pulmonary disease (PD) caused by coinfection with multiple NTM species.

METHODS

We retrospectively reviewed patients with NTM-PD at a tertiary referral hospital in Korea between March 2012 and December 2018. Coinfection was defined as two or more species of NTM pathogens isolated from the same respiratory specimen or different specimens within three months.

RESULTS

Among 1,009 patients with NTM-PD, 147 (14.6%) NTM coinfections were observed (average age 64.7 years, 69.4% women). NTM species were identified more frequently (median 6 vs. 3 times, P < 0.001) in the coinfection group than in the single species group, and follow-up duration was also longer in the coinfection group (median 44.9 vs. 27.1 months, P < 0.001). Mycobacterium avium complex (MAC) and M. abscessus and M. massiliense (MAB) were the dominant combinations (n = 71, 48.3%). For patients treated for over six months in the MAC plus MAB group (n = 31), sputum culture conversion and microbiological cure were achieved in 67.7% and 41.9% of patients, respectively. We divided the MAC plus MAB coinfection group into three subgroups according to the target mycobacteria; however, no statistical differences were found in the treatment outcomes.

CONCLUSION

In NTM-PD cases, a significant number of multiple NTM species coinfections occurred. Proper identification of all cultured NTM species through follow-up is necessary to detect multispecies coinfections. Further research is needed to understand the nature of NTM-PD in such cases.

Risk Factors for and Outcomes Following Early Acquisition of Mycobacterium abscessus Complex After Lung Transplantation

Background

Lung transplant recipients are at increased risk of Mycobacterium abscessus complex (MABC) acquisition and invasive infection. We analyzed risk factors and outcomes of early post-lung transplant MABC acquisition.

Methods

We conducted a retrospective matched case-control study of patients who underwent lung transplant from 1/1/2012 to 12/31/2021 at a single large tertiary care facility. Cases had de novo MABC isolation within 90 days post-transplant. Controls had no positive MABC cultures and were matched 3:1 with cases based on age and transplant date. Recipient demographics and pre-/peri-operative characteristics were analyzed, and a regression model was used to determine independent risk factors for MABC acquisition. We also assessed 1-year post-transplant outcomes, including mortality.

Results

Among 1145 lung transplants, we identified 79 cases and 237 matched controls. Post-transplant mechanical ventilation for >48 hours was independently associated with MABC acquisition (adjusted odds ratio, 2.46; 95% CI, 1.29-4.72; P = .007). Compared with controls, cases required more days of hospitalization after the MABC index date (28 vs 12 days; P = .01) and had decreased 1-year post-transplant survival (78% vs 89%; log-rank P = .02). One-year mortality appeared highest for cases who acquired M. abscessus subsp. abscessus (31% mortality) or had extrapulmonary infections (43% mortality).

Conclusions

In this large case-control study, prolonged post-transplant ventilator duration was associated with early post-lung transplant MABC acquisition, which in turn was associated with increased hospital-days and mortality. Further studies are needed to determine the best strategies for MABC prevention, surveillance, and management.

Rates and Risk Factors of Progression in Patients With Nontuberculous Mycobacterial Pulmonary Disease: Secondary Analysis of a Prospective Cohort Study

BACKGROUND

The clinical course of nontuberculous mycobacterial pulmonary disease (NTM-PD) is varied, and a watchful waiting management strategy is appropriate for a subset of patients. Understanding disease progression and risk factors for progression is essential for deciding on an appropriate follow-up strategy.

RESEARCH QUESTION

What is the rate of NTM-PD progression, and what are the predictors of progression?

STUDY DESIGN AND METHODS

Patients with NTM-PD who were enrolled in a prospective observational cohort study between July 1, 2011, and December 31, 2022, were included in this analysis. Clinical, bacterial, laboratory, and radiographic data were collected at enrollment and then regularly during follow-up. NTM-PD progression was defined as either the initiation of treatment or the clinician's intention to treat. The rate of progression was calculated and the predictors for progression were analyzed.

RESULTS

Of the 477 patients enrolled, NTM-PD progressed in 192 patients over a median follow-up of 5.4 years. The incidence of NTM-PD progression was 11.0 cases per 100 person-years (95% CI, 9.5-12.7 cases per 100 person-years). The proportion of patients experiencing disease progression was 21.4% at 1 year, 33.8% at 3 years, and 43.3% at 5 years. The final multivariable analysis model identified female sex (adjusted hazard ratio [aHR], 1.69; 95% CI, 1.19-2.39), elevated erythrocyte sedimentation rate (aHR, 1.79; 95% CI, 1.31-2.43), FEV1 % predicted (aHR, 0.89; 95% CI, 0.82-0.96), and the presence of a cavity (aHR, 2.78; 95% CI, 2.03-3.80) as predictors of progression.

INTERPRETATION

About half of patients with NTM-PD experienced progression during an observation period of > 5 years. Patients with risk factors for progression should be observed closely.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01616745; URL: www.

CLINICALTRIALS

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Nontuberculous Mycobacterial Infections in Pediatric Solid Organ Transplant and Hematopoietic Cell Transplant Recipients

The diagnosis of nontuberculous mycobacterial infections is challenging in pediatric solid organ transplant and hematopoietic cell transplant recipients due to the absence of specific clinical manifestations, limitations of sampling, prolonged times for culture and identification, and difficulty discerning colonization from clinical disease. Treatment is dependent on the nontuberculous mycobacterial species, disease type, and pattern of drug resistance. Treatment of nontuberculous mycobacterial infections involves prolonged durations of therapy using multiple medications, which are limited by toxicities and drug-drug interactions.

Microbiological persistence in patients with Mycobacterium abscessus complex lung disease: The prevalence, predictors, and the impact on progression

OBJECTIVES

Persistent growth of Mycobacterium abscessus complex (MABC) in the respiratory system is not uncommon and may indicate continuous infection of MABC lung disease (MABC-LD), but its prevalence, risk factors, and clinical impact have not been investigated.

METHODS

The present study was conducted in two medical centers in northern Taiwan. We enrolled patients with MABC-LD and investigated the prevalence and predictors of persistent culture positivity (MABC-PP). Furthermore, we analyzed the association between MABC-PP and radiographic or clinical progression.

RESULTS

Among 189 patients with MABC-LD, 58 were in the MABC-PP group. Independent predictors for MABC-PP included an increasing radiographic score and highest acid-fast stain (AFS) of strong positivity (3-4+) at initial diagnosis (compared with negative AFS). MABC-PP and highest AFS were independently associated with MABC-LD progression by the multivariable analysis model. The adjusted hazard ratio increased to 3.56 when the two independent factors existed.

CONCLUSIONS

MABC-PP accounted for 30.7% and was predicted by initial AFS grade and radiographic score. Patients with MABC-PP, and highest AFS grade might have disease progression.

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.

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

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

The Clinical Implications of Serum Carbohydrate Antigen 19-9 Levels in Patients with Nontuberculous Mycobacteria Pulmonary Disease

Serum carbohydrate antigen 19-9 (CA19-9) levels can increase in nontuberculous mycobacteria pulmonary disease (NTM-PD), and the levels correlate with disease activity. We compared the clinical characteristics of NTM-PD patients with and without elevated CA19-9 levels and evaluated its association with antibiotic response in a retrospective study of NTM-PD patients diagnosed between January 1994 and December 2020. We analyzed 1112 patients who had serum CA19-9 measured: 322 with elevated CA19-9 and 790 with normal CA19-9. The erythrocyte sedimentation rate and C-reactive protein levels were significantly higher in the elevated CA19-9 group (p < 0.001 and p = 0.029, respectively). The 1-year culture conversion rate after antibiotics did not differ between the elevated (n = 206) and normal (n = 377) CA19-9 groups (80% vs. 72%, p = 0.055). Analysis of a subset of 434 patients revealed that current smoking, bronchiectasis, acid-fast bacilli smear positivity, and the M. abscessus strain significantly reduced microbiological cure rates. Serum CA 19-9 levels did not have a significant association with microbiological cure in a multivariate analysis. These findings suggest that the role of serum CA19-9 in predicting antibiotic treatment outcomes is limited, and that elevated CA19-9 does not necessarily indicate a poor outcome.

Application of FT-IR Spectroscopy for Mycobacterium abscessus complex subspecies differentiation

Mycobacterium abscessus complex (MABSC) subspecies differentiation improves patients' therapy and outcome. Fourier-Transform-Infrared Spectroscopy (FT-IRS) was applied for subspecies discrimination of 15 strains on different media: Löwenstein-Jensen showed the best resolution power; Linear Discriminant Analysis model differentiated M. abscessus susbsp. abscessus from M. abscessus subsp. massiliense. FT-IRS has a potential role in rapidly MABSC subspecies identification.

Mycobacterium abscessus VapC5 toxin potentiates evasion of antibiotic killing by ribosome overproduction and activation of multiple resistance pathways

Mycobacterium abscessus (Mab) infections are inexplicably intractable to clearing after aggressive and lengthy treatment regimens. Here we discovered that acquisition of a single toxin-antitoxin system enables Mab to activate a phenotypic switch that enhances survival upon treatment with current first-line antibiotics. This switch is tripped when the VapC5 toxin inactivates tRNASerCGA by cleavage at only one site within its anticodon, leading to growth arrest. Concomitant tRNASerCGA depletion then reprograms the transcriptome to favor synthesis of proteins naturally low in the cognate Ser UCG codon including the transcription factor WhiB7 and members of its regulon as well as the ribosomal protein family. This programmed stockpiling of ribosomes is predicted to override the efficacy of ribosome-targeting antibiotics while the growth arrest phenotype attenuates antibiotics targeting cell wall synthesis. In agreement, VapC5 increases Mab persister formation upon exposure to amikacin and the next-generation oxazolidinone tedizolid (both target ribosomes) or cefoxitin (inhibits cell wall synthesis). These findings expand the repertoire of genetic adaptations harnessed by Mab to survive assaults intended to eradicate it, as well as provide a much-needed framework for selection of shorter and more efficacious alternate treatment options for Mab infections using currently available antimicrobials whose targets are not confounded by VapC5.

Mycobacteria in Organ Transplant Recipients

This review describes the epidemiology and risk factors of tuberculosis (TB) in solid organ transplant recipients. We discuss the pre-transplant screening for risk of TB and management of latent TB in this population. We also discuss the challenges of management of TB and other difficult to treat mycobacteria such as Mycobacterium abscessus and Mycobacterium avium complex. The drugs for the management of these infections include rifamycins which have significant drug interactions with immunosuppressants and must be monitored closely.

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.

Disseminated nontuberculous mycobacteria infection in an immunocompetent host: A case report

RATIONALE

Disseminated nontuberculous mycobacterial (NTM) infections are rare and occur primarily in immunocompromised hosts. Mycobacterium abscessus complex (MABC), including M abscessus subsp. massiliense (hereafter M massiliense) is a complex of rapidly growing mycobacterial (RGM) species of NTM. Here, we present a rare case of disseminated NTM infection with RGM bacteremia caused by M massiliense in an immunocompetent host.

PATIENT CONCERNS

A 64-year-old woman with a recent history of spine fracture and septic pneumonia was transferred to our emergency room for dyspnea and fever. A peripherally inserted central catheter (PICC) had been placed over 6 months prior.

DIAGNOSES

Chest computed tomography (CT) showed multifocal patchy consolidations and ground-glass opacity in both lungs. NTM suspected of RGM was isolated from the blood cultures. During hospitalization, multiple erythematous and hemorrhagic crusted nodules developed on the patient's upper and lower extremities, which were confirmed as disseminated NTM infection on skin biopsy.

INTERVENTIONS

After NTM suspected of RGM was isolated from the blood cultures, the patient was empirically treated with antibiotics used for NTM infection, and the PICC was removed. Thereafter, the subspecies of NTM was reported as M massiliense and she was treated according to the antibiotic susceptibility testing results.

OUTCOME

Although skin lesions and inflammatory markers improved gradually during antibiotic treatment over 10 weeks, NTM could still be isolated from the blood culture.

LESSONS

Disseminated NTM infections with RGM bacteremia in an immunocompetent host have rarely been reported. In this case, PICC placement for more than 6 months was suspected to be an important risk factor for RGM bacteremia in an immunocompetent patient. To date, there are only insufficient case reports, moreover no clear guidelines regarding the optimal choice of antibiotics or length of treatment for disseminated NTM infection. Therefore, it is necessary to establish treatment guidelines for patients with disseminated NTM infection and bacteremia.

Impaired cough-related quality of life in patients with nontuberculous mycobacteriosis

BACKGROUND

Cough and sputum are the significant symptoms of nontuberculous mycobacteriosis (NTM) and impair quality of life (QOL). However, the relationship between these symptoms and clinical features is not fully understood. This study aimed to investigate cough-related QOL in NTM patients.

METHODS

The study subjects included 78 patients with NTM at our hospital from October to December 2015. They completed the Leicester Cough Questionnaire (LCQ) and the Cough and Sputum Assessment Questionnaire (CASA-Q) (both questionnaires: the higher, the better); the Frequency Scale for the Symptoms of gastroesophageal reflux disease (GERD) (FSSG), a validated Japanese questionnaire for GERD (the higher, the worse), was also assessed. The FSSG consists of 12 items, including the reflux-related symptoms and dysmotility symptoms domains, each of which is quantified on a scale of 0-4 points, and the cut-off score for GERD is set at 8 points. Associations between these scores and clinical parameters were assessed.

RESULTS

The total LCQ score was reduced-the physical domain was dominant. The total LCQ and CASA-Q scores were reduced, with dominance in the physical and symptoms domains, respectively. The reflux-related symptoms score was higher than the dysmotility symptoms score. A multivariate linear regression analysis revealed that the mean total LCQ score was independently associated with current smoking, fibrocavitary type, bilateral cavitary lesion, and FSSG total score.

CONCLUSIONS

Cough-related QOL was impaired in NTM patients who currently smoked, had radiological characteristics, and had GERD.

Fragment-Based Drug Discovery against Mycobacteria: The Success and Challenges

The emergence of drug-resistant mycobacteria, including Mycobacterium tuberculosis (Mtb) and non-tuberculous mycobacteria (NTM), poses an increasing global threat that urgently demands the development of new potent anti-mycobacterial drugs. One of the approaches toward the identification of new drugs is fragment-based drug discovery (FBDD), which is the most ingenious among other drug discovery models, such as structure-based drug design (SBDD) and high-throughput screening. Specialized techniques, such as X-ray crystallography, nuclear magnetic resonance spectroscopy, and many others, are part of the drug discovery approach to combat the Mtb and NTM global menaces. Moreover, the primary drawbacks of traditional methods, such as the limited measurement of biomolecular toxicity and uncertain bioavailability evaluation, are successfully overcome by the FBDD approach. The current review focuses on the recognition of fragment-based drug discovery as a popular approach using virtual, computational, and biophysical methods to identify potent fragment molecules. FBDD focuses on designing optimal inhibitors against potential therapeutic targets of NTM and Mtb (PurC, ArgB, MmpL3, and TrmD). Additionally, we have elaborated on the challenges associated with the FBDD approach in the identification and development of novel compounds. Insights into the applications and overcoming the challenges of FBDD approaches will aid in the identification of potential therapeutic compounds to treat drug-sensitive and drug-resistant NTMs and Mtb infections.

Mycobacterium abscessus: It’s Complex

Mycobacterium abscessus (M. abscessus) is an opportunistic pathogen usually colonizing abnormal lung airways and is often seen in patients with cystic fibrosis. Currently, there is no vaccine available for M. abscessus in clinical development. The treatment of M. abscessus-related pulmonary diseases is peculiar due to intrinsic resistance to several commonly used antibiotics. The development of either prophylactic or therapeutic interventions for M. abscessus pulmonary infections is hindered by the absence of an adequate experimental animal model. In this review, we outline the critical elements related to M. abscessus virulence mechanisms, host–pathogen interactions, and treatment challenges associated with M. abscessus pulmonary infections. The challenges of effectively combating this pathogen include developing appropriate preclinical animal models of infection, developing proper diagnostics, and designing novel strategies for treating drug-resistant M. abscessus.

Antibiotic Therapy for Difficult-to-Treat Infections in Lung Transplant Recipients: A Practical Approach

Lung transplant recipients are at higher risk to develop infectious diseases due to multi-drug resistant pathogens, which often chronically colonize the respiratory tract before transplantation. The emergence of these difficult-to-treat infections is a therapeutic challenge, and it may represent a contraindication to lung transplantation. New antibiotic options are currently available, but data on their efficacy and safety in the transplant population are limited, and clinical evidence for choosing the most appropriate antibiotic therapy is often lacking. In this review, we provide a summary of the best evidence available in terms of choice of antibiotic and duration of therapy for MDR/XDR P. aeruginosa, Burkholderia cepacia complex, Mycobacterium abscessus complex and Nocardia spp. infections in lung transplant candidates and recipients.

Surgical Treatment of Nontuberculous Mycobacterial Pulmonary Disease and a Combination of Nontuberculous Mycobacterium Pulmonary Disease and Pulmonary Tuberculosis

OBJECTIVES

Nontuberculous mycobacterial pulmonary disease (NTMPD) is an important health system problem worldwide. Surgical treatment experience is limited, and the safety of such operations is still unclarified. Therefore, improving our knowledge of NTMPD is important.

DESIGN

In this retrospective observational study, we analyzed the medical records of 2,432 patients operated on from January 2011 through December 2017 in our hospital. There were 20 patients with NTMPD in group 1 and 23 patients with combined NTMPD and pulmonary tuberculosis in group 2. Patients received antibiotic treatment before and after surgery as per Russian Federal clinical guidelines and individual drug susceptibility.

RESULTS

Postoperative complications occurred in 2 (10%) cases in group 1 and 4 (17.4%) in group 2, and intraoperative complications occurred in 2 (8.7%) cases in group 2. There was no 30-day mortality in both groups. After 1 year, all 40 traced patients had neither bacterial excretion nor cavities in the lungs. After 3 years and 5 years, the efficacy among 32 and 13 traced patients was 100%, respectively.

CONCLUSIONS

Modern surgery for small NTMPD forms is safe - helping improve outcomes for ineffective antibiotic treatment. Combined surgery and antibiotic treatment are acceptable in both the short and long term.

Polycationic Glycopolymer Demonstrates Activity Against Persisters and Biofilms of Non-tuberculosis Mycobacteria Cystic Fibrosis Clinical Isolates in vitro

Non-tuberculosis Mycobacterium (NTM) is a group of opportunistic pathogens associated with pulmonary infections that are difficult to diagnose and treat. Standard treatment typically consists of prolonged combination antibiotic therapy. Antibiotic resistance and the role of biofilms in pathogen communities, such as NTM persister cells, is an important unmet challenge that leads to increased toxicity, frequent relapse, poor clinical management, and an extended treatment period. Infection recurrence and relapse are not uncommon among individuals with cystic fibrosis (CF) or chronic obstructive pulmonary disease (COPD), where thick mucus supports bacterial biofilm production and impairs mucociliary clearance. The study evaluates a membrane-active cationic glycopolymer [poly (acetyl, arginyl) glucosamine (PAAG)] being developed to support the safe and effective treatment of NTM biofilm infections. PAAG shows antibacterial activity against a wide range of pathogenic bacteria at concentrations non-toxic to human epithelial cells. Time-kill curves demonstrated PAAG’s rapid bactericidal potential at concentrations as low as 1X MIC against all NTM strains tested and compared to the standard of care. PAAG treatment prevents persister formation and eradicates antibiotic-induced persister cells in planktonic NTM cultures below the limit of detection (10 colony-forming unit (CFU)/ml). Further, PAAG showed the ability to penetrate and disperse NTM biofilms formed by both rapidly and slowly growing strains, significantly reducing the biofilm biomass (p < 0.0001) compared to the untreated NTM biofilms. Microscopical examination confirmed PAAG’s ability to disrupt and disperse mycobacterial biofilms. A single PAAG treatment resulted in up to a 25-fold reduction in live-labeled NTM and a 78% reduction in biofilm thickness. Similar to other polycationic molecules, PAAG’s bactericidal and antibiofilm activities employ rapid permeabilization of the outer membrane of the NTM strains, and subsequently, reduce the membrane potential even at concentrations as low as 50 μg/ml (p < 0.001). The outcomes of these in vitro analyses suggest the importance of this polycationic glycopolymer, PAAG, as a potential therapeutic agent for opportunistic NTM infections.

Disease progression in patients with nontuberculous mycobacterial lung disease of nodular bronchiectatic (NB) pattern: the role of cavitary NB and soluble programmed death protein-1

BACKGROUND

In patients with nodular bronchiectatic (NB) nontuberculous mycobacterial-lung disease (NTM-LD), risk factors for disease progression have not been clearly investigated. The roles of cavitary NB and soluble programmed death protein-1 (sPD-1), an immune-related biomarker, in the disease course of NB NTM-LD remain unknown.

METHODS

Patients with NB NTM-LD were enrolled from two medical centers in 2014-2020. We identified cavitary NB, measured sPD-1 levels, and analyzed factors associated with cavitary NB and predictors for disease progression of NB NTM-LD.

RESULTS

Of 120 cases of NB NTM-LD, 87 (72.5%) were caused by Mycobacterium avium complex. sPD-1 levels were lower in 13 (10.8%) patients with cavitary NB than in non-cavitary patients (P = 0.020). Over 1.41 ± 1.43 years of follow-up, 12 (92.3%) patients in the cavitary and 66 (61.7%) in the non-cavitary group developed disease progression (P = 0.032). In multivariate analysis, body mass index (BMI) (Kg/m 2, adjusted hazard ratio [aHR], 0.895 [95% CI, 0.811-0.988]), sputum smear grade (aHR, 1.247 [1.014-1.534), cavitary NB (aHR, 2.008 [1.052-3.834]) and sPD-1 (per 10-pg/mL increase, aHR, 0.889 [0.816-0.967]) were predictive for disease progression. Notably, sPD-1 showed a dose-dependent association with disease progression (sPD-1 ≤ 23.5 pg/ml; aHR, 3.306 [1.664-6.567], and sPD-1: 23.6-53.7 pg/ml; aHR, 2.496 [1.390-4.483]) compared with the reference (sPD-1 > 53.7 pg/ml).

CONCLUSIONS

Patients with NB NTM-LD and low sPD-1, low BMI, high smear grade and cavitary NB were at high risk for disease progression. sPD-1 was low in patients with cavitary NB phenotype and dose-responsively associated with disease progression.

A first case report of nasopharyngeal Mycobacterium abscessus subspecies massiliense infection

BACKGROUND

Mycobacterium abscessus subspecies massiliense is a non-tuberculous mycobacteriosis and was subdivided from Mycobacterium abscessus in 2006. This article is the first report on nasopharyngitis caused by Mycobacterium abscessus subspecies massiliense.

CASE PRESENTATION

A 45-year-old woman had an 18-month history of recurrent nasopharyngitis and presented with pain in the throat. Mycobacterial tissue culture and polymerase chain reaction testing revealed the presence of Mycobacterium abscessus subspecies massiliense in the nasopharyngeal tissue. This patient underwent surgery, followed by multiple rounds of chemotherapy with oral and intravenous antibiotic agents for 16 weeks. She has had no recurrence during the 56 weeks since treatment.

CONCLUSION

It is difficult to detect the presence of Mycobacterium abscessus subspecies massiliense in a culture from the swabbing sample. The tissue culture from a biopsy specimen is mandatory for the identification of the species. Currently, no definite treatment policy is available and only empirical treatment is applied. This case is an important for the diagnosis and treatment of this bacterial infection on nasopharynx.

Current Molecular Therapeutic Agents and Drug Candidates for Mycobacterium abscessus

Mycobacterium abscessus has been recognised as a dreadful respiratory pathogen among the non-tuberculous mycobacteria (NTM) because of misdiagnosis, prolonged therapy with poor treatment outcomes and a high cost. This pathogen also shows extremely high antimicrobial resistance against current antibiotics, including the anti-tuberculosis agents. Therefore, current chemotherapies require a long curative period and the clinical outcomes are not satisfactory. Thus, there is an urgent need for discovering and developing novel, more effective anti-M. abscessus drugs. In this review, we sum the effectiveness of the current anti-M. abscessus drugs and drug candidates. Furthermore, we describe the shortcomings and difficulties associated with M. abscessus drug discovery and development.

Combination treatment with antibiotics and surgical lung resection for Mycobacterium abscessus pulmonary infection in a breast cancer patient

A 51-year-old woman was admitted to our hospital because of pneumonia after chemotherapy with doxorubicin and cyclophosphamide for left breast cancer. The patient was diagnosed with Mycobacterium abscessus pulmonary infection by the detection of M. abscessus complex (MABC) in sputum cultures. However, MABC is intrinsically resistant to most of the antibacterial agents, and MABC pulmonary disease outcomes with modern antibiotic treatment are currently the worst among all mycobacterial species. We herein report the successful treatment of M. abscessus pulmonary infection by a combination treatment with antibiotics and surgical lung resection.

Radiographic severity and treatment outcome of Mycobacterium abscessus complex pulmonary disease

INTRODUCTION

The lack of reliable predictors for the treatment response complicates decisions to initiate treatment in patients with Mycobacterium abscessus complex pulmonary disease (MABC-PD). We aimed to investigate whether baseline radiographic disease severity is associated with treatment outcome in MABC-PD.

METHOD

We retrospectively analyzed 101 patients with MABC-PD (54 with M. abscessus-PD and 47 with M. massiliense-PD) treated in a tertiary referral hospital between January 2006 and December 2019. Using chest computed tomography images, baseline radiographic disease severity was quantitatively scored according to five categories of radiographic lesions (bronchiectasis, bronchiolitis, cavities, nodules, and consolidation).

RESULTS

Treatment success was achieved in 53.7% of patients with M. abscessus-PD and 85.1% of patients with M. massiliense-PD. Higher overall scores for baseline radiographic disease severity were associated with treatment failure in patients with M. massiliense-PD (aOR 1.35, 95% CI 1.02-1.79 for each 1-point increase in severity score), as well as in patients with M. abscessus-PD (aOR 1.15, 95% CI 1.00-1.33). This was particularly prominent in patients with overall severity score of ≥14 (aOR 31.16, 95% CI 1.12-868.95 for M. massiliense-PD and aOR 3.55, 95% CI 1.01-12.45 for M. abscessus-PD). Among variable radiographic abnormalities, the score for cavitary lesion severity was associated with treatment failure in patients with M. abscessus-PD (aOR 1.26, 95% CI 1.01-1.56), but not in patients with M. massiliense-PD.

CONCLUSIONS

Given the association between baseline radiographic disease severity and treatment outcome, initiating treatment should be actively considered before significant progression of radiographic lesions in patients with MABC-PD.

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.

Mortality and Prognostic Factors of Nontuberculous Mycobacterial Infection in Korea: A Population-based Comparative Study

BACKGROUND

Population-based studies on the mortality burden of nontuberculous mycobacteria (NTM) infection are lacking. We compared the long-term mortality of NTM-infected patients with tuberculosis (TB)-patients and the general population, and investigated mortality-associated factors.

METHODS

We analyzed nationwide-data from the Korean National Health Insurance and Korea-Statistical Office between 2002 and 2017. NTM infection was identified using the International Classification of Disease, Tenth Revision code, with one-to-one matching to TB patients and general population controls.

RESULTS

A total of 530 401 individuals were analyzed, including 183 267 with NTM infections; 166 666 with TB; and 180 468 controls. The overall 6-, 10-, and 14-year cumulative survival probabilities in the NTM group were 86.3%, 80.8%, and 77.1%, respectively, which were significantly lower than those of the TB or control groups (log-rank P < .0001). In cases of NTM and TB coinfection, the overall 6-, 10-, and 14-year cumulative survival probabilities were 75.1%, 65.4%, and 57.0%, respectively. Multivariable analysis indicated that old age, male gender, province, and various respiratory or nonrespiratory comorbidities were significantly associated with mortality of NTM infection. The use of a macrolide (more than 1 year) negatively correlated with mortality of NTM infection (adjusted hazard ratio [aHR] 0.61, 95% confidence interval [CI] .53-.71), regardless of azithromycin (aHR 0.60, 95% CI .43-.85) or clarithromycin use (aHR 0.63, 95% CI .53-.75).

CONCLUSIONS

NTM-infected patients had poor prognosis when compared to TB patients or the general population, especially for NTM and TB coinfection. NTM mortality was associated with certain demographic characteristics, but long-term use of macrolides may provide survival benefits.

Impact of Susceptibility to Injectable Antibiotics on the Treatment Outcomes of Mycobacterium abscessus Pulmonary Disease

Background

Current guidelines recommend a susceptibility-based regimen for Mycobacterium abscessus subspecies abscessus pulmonary disease (MAB-PD), but the evidence is weak. We aimed to investigate the association between treatment outcomes and in vitro drug susceptibility to injectable antibiotics in MAB-PD patients.

Methods

We enrolled MAB-PD patients treated with intravenous amikacin and beta-lactams for ≥4 weeks at 4 referral hospitals in Seoul, South Korea. Culture conversion and microbiological cure at 1 year were evaluated based on susceptibility to injectable antibiotics among patients treated with those antibiotics for ≥2 weeks.

Results

A total of 82 patients were analyzed. The mean age was 58.7 years, and 65.9% were women. Sputum culture conversion and microbiological cure were achieved in 52.4% and 41.5% of patients, respectively. Amikacin was the most common agent to which the M. abscessus subspecies abscessus isolates were susceptible (81.7%); 9.8% and 24.0% of the isolates were resistant to cefoxitin and imipenem, respectively. The clarithromycin-inducible resistance (IR) group (n = 65) had a lower microbiological cure rate than the clarithromycin-susceptible group (35.4% vs 64.7%). The treatment outcomes appeared to be similar regardless of in vitro susceptibility results with regard to intravenous amikacin, cefoxitin, imipenem, and moxifloxacin. In the subgroup analysis of the clarithromycin-IR group, the treatment outcomes did not differ according to antibiotic susceptibility.

Conclusions

We did not find evidence supporting the use of susceptibility-based treatment with intravenous amikacin and beta-lactams in patients with MAB-PD. Further research is required.

Antimicrobial susceptibility profiles of Mycobacterium abscessus complex isolates from respiratory specimens in Shanghai, China

OBJECTIVES

The aim of this study was to compare the antibiotic susceptibility profiles of Mycobacterium abscessus complex (MABC) isolates and to investigate the relationship between susceptibility profiles and genetic mechanisms of macrolide resistance.

METHODS

More than 200 isolates collected from respiratory specimens between 2014 and 2018 were randomly analysed in this study. Minimum inhibitory concentrations (Mics) of ten potential antimicrobial agents were determined by the microplate alamarBlue assay.

RESULTS

We identified 43 MABC isolates, including 32 M. abscessus subsp. abscessus (M. abscessus) (6 from immunocompromised patients) and 11 M. abscessus subsp. massiliense (M. massiliense). The majority of MABC isolates were susceptible to amikacin (96.9% and 100.0% for M. abscessus and M. massiliense, respectively), linezolid (96.9% and 100.0%, respectively), cefoxitin (100.0% and 100.0%, respectively), imipenem (90.6% and 72.7%, respectively) and tobramycin (90.6% and 72.7%, respectively). The resistance rates to clarithromycin and doxycycline in isolates of M. abscessus (68.8% and 100.0%) were significantly higher than those in isolates of M. massiliense (18.2% and 63.6%) (P < 0.05), whereas the percentage of tobramycin-resistant isolates among M. abscessus (9.4%) was significantly lower than among M. massiliense (27.3%) (P = 0.007). Sequencing analyses showed significant differences between erm(41) of M. abscessus and M. massiliense.

CONCLUSION

Mycobacterium abscessus is the dominant pathogen of pulmonary MABC infections in our hospital. Aminoglycosides (amikacin and tobramycin), β-lactams (cefoxitin and imipenem) and linezolid exhibited potent inhibitory activity against MABC in vitro. The erm(41) gene may be a promising marker to predict macrolide susceptibility for M. abscessus.

Clinical Implications of Size of Cavities in Patients With Nontuberculous Mycobacterial Pulmonary Disease: A Single-Center Cohort Study

Background

The presence of cavities is associated with unfavorable prognosis in patients with nontuberculous mycobacterial pulmonary disease (NTM-PD). However, little is known about the characteristics of such cavities and their impact on clinical outcomes. The aim of this study was to investigate the size of cavities and their implications on treatment outcomes and mortality in patients with NTM-PD.

Methods

We included patients diagnosed with NTM-PD at Seoul National University Hospital between January 1, 2007, and December 31, 2018. We measured the size of cavities on chest computed tomography scans performed at the time of diagnosis and used multivariable logistic regression and Cox proportional hazards regression analysis to investigate the impact of these measurements on treatment outcomes and mortality.

Results

The study cohort comprised 421 patients (noncavitary, n = 329; cavitary, n = 92) with NTM-PD. During a median follow-up period of 49 months, 118 (35.9%) of the 329 patients with noncavitary and 64 (69.6%) of the 92 patients with cavitary NTM-PD received antibiotic treatment. Cavities >2 cm were associated with worse treatment outcomes (adjusted odds ratio, 0.41; 95% CI, 0.17–0.96) and higher mortality (adjusted hazard ratio, 2.52; 95% CI, 1.09–5.84), while there was no difference in treatment outcomes or mortality between patients with cavities ≤2 cm and patients with noncavitary NTM-PD.

Conclusions

Clinical outcomes are different according to the size of cavities in patients with cavitary NTM-PD; thus, the measurement of the size of cavities could help in making clinical decisions.

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.

Comparison of drug-susceptibility patterns and gene sequences associated with clarithromycin and azithromycin resistance in Mycobacterium abscessus complex isolates and evaluation of the accumulation of intrinsic macrolide resistance

Introduction. Mycobacterium abscessus complex (MABC) is an infectious agent associated with macrolide resistance and treatment failure.Hypothesis/Gap Statement. Despite drug-susceptibility testing for MABC isolates including clarithromycin (CAM), long-term treatment with azithromycin (AZM) for MABC disease is recommended.Aim. We compared phenotypic and genotypic resistance to AZM and CAM in clinical isolates and evaluated the accumulation of intrinsic macrolide resistance (AIM) and morphological changes by macrolides exposure.Methodology. Forty-nine isolates were characterized regarding erm(41) sequevars. Sequencing data were compared to the nucleotide sequence of rrl and whiB7. The AIM MIC was performed in three reference strains and 15 isolates were randomized [each set of five isolates with M. abscessus subsp. abscessus (MAA) T28, MAA C28 and subsp. massiliense (MAM)].Results. The 49 isolates were distributed as 24 MAA T28, 5 MAA C28 and 20 MAM. The MIC₅₀ values to CAM at day 3 in MAA T28, C28 and MAM were 1, 0.12 and 0.12 µg ml^-1, while those at day 14 were 32, 0.5 and 0.12 µg ml^-1, respectively. The AZM-MIC₅₀ values at day 3 of the above isolates were 4, 0.25 and 0.5 µg ml^-1, while those at day 14 were >64, 0.5 and 0.5 µg ml^-1, respectively. Neither mutations in rrl of MAA T28 with acquired resistance nor deletions in whiB7 of MAA T28 without inducible resistance were observed . For AIM MIC, MAA T28 showed that the time-to-detection of AZM resistance was significantly faster over that of CAM (P<0.05). Morphological changes were not determined in all isolates.Conclusion. Our findings did not support the suggestion for the preferential use of AZM for, at least, MAA T28 disease due to the high-level MIC value and the increased AIM. The long duration of AZM-based treatment eventually may favour the emergence of isolates with a high-level of intrinsic resistance.

BACES Score for Predicting Mortality in Nontuberculous Mycobacterial Pulmonary Disease

Rationale: Because the prognosis of nontuberculous mycobacterial pulmonary disease varies, a scoring system predicting mortality is needed.Objectives: We aimed to develop a novel scoring system to predict mortality among patients with nontuberculous mycobacterial pulmonary disease.Methods: We included patients age ≥20 years with newly diagnosed nontuberculous mycobacterial pulmonary disease, with Mycobacterium avium, M. intracellulare, M. abscessus subsp. abscessus, or M. abscessus subsp. massiliense. Cox proportional hazards models were used to identify predictors of mortality in a derivation cohort, and a scoring system was developed. It was validated in an independent prospective cohort.Measurements and Main Results: A total 1,181 and 377 patients were included in the derivation and validation cohorts, respectively. In the final model, body mass index <18.5 kg/m² (1 point), age ≥65 years (1 point), presence of cavity (1 point), elevated erythrocyte sedimentation rate (1 point), and male sex (1 point) were selected as predictors for mortality. We named this novel scoring system BACES (body mass index, age, cavity, erythrocyte sedimentation rate, and sex). Harrell's C-index for the BACES score was 0.812 (95% confidence interval, 0.786-0.837) in the derivation cohort and 0.854 (95% confidence interval, 0.797-0.911) in the validation cohort, indicating excellent discrimination performance. The estimated 5-year risk of mortality was 1.2% with BACES score 0 and 82.9% with BACES score 5.Conclusions: We developed the BACES score, which could accurately predict mortality among patients with nontuberculous mycobacterial pulmonary disease caused by M. avium, M. intracellulare, M. abscessus subsp. abscessus, or M. abscessus subsp. massiliense.

Clinical risk factors related to treatment failure in Mycobacterium abscessus lung disease

The clinical importance of Mycobacterium abscessus subsp. abscessus (M. abscessus) lung disease has been increasing, but few studies have assessed the clinical characteristics associated with the treatment outcome. We retrospectively analyzed 75 consecutive patients with M. abscessus lung disease diagnosed at a tertiary hospital from January 2004 to April 2018. Among 52 patients with sufficient clinical data, 19 patients (42.2%) achieved treatment success. Compared with 26 (57.8%) patients in the treatment failure group, body mass index (BMI) (19.8 vs 17.5 kg/m2, P = 0.022), previous nontuberculous mycobacterial (NTM) lung disease (26.3% vs 61.5%, P = 0.034), the presence of cavitary lesions (31.6% vs 69.2%, P = 0.017), and the bronchiectasis score (3.0 vs 5.0, P = 0.003) were significantly different in the treatment success group. Multivariate analysis showed that age (adjusted hazard ratio (aHR), 0.94; 95% confidence interval (CI), 0.90 to 0.99; P = 0.010), the presence of cavitary lesions (aHR, 0.34; 95% CI, 0.12 to 0.94; P = 0.039), and previous NTM lung disease (aHR, 0.28; 95% CI, 0.09 to 0.86; P = 0.026) were negatively associated with treatment success. This is the first study to show that previous NTM lung disease might be a clinically important factor related to unfavorable treatment outcomes in M. abscessus lung disease patients. To increase our understanding the characteristics of M. abscessus lung disease, this factor should be independently analyzed in future research.

GenSeizer: a Multiplex PCR-Based Targeted Gene Sequencing Platform for Rapid and Accurate Identification of Major Mycobacterium Species

Mycobacterium tuberculosis and nontuberculous mycobacterium (NTM) infections often exhibit similar clinical symptoms. Timely and effective treatment relies on the rapid and accurate identification of species and resistance genotypes. In this study, a new platform (GenSeizer), which combines bioinformatics analysis of a large data set and multiplex PCR-based targeted gene sequencing, was developed to identify 10 major Mycobacterium species that cause pulmonary, as well as extrapulmonary, human diseases. The simultaneous detection of certain erm(41) and rrl resistance genotypes in M. abscessus was also feasible. This platform was specific and sensitive and exhibited no cross-reactivity among reference strains and a detection limit of 5 DNA copies or 50 CFU Mycobacterium/ml. In a blind comparison, GenSeizer and multigene sequencing showed 100% agreement in the ability to identify 88 clinical Mycobacterium isolates. The resistance genotypes, confirmed by whole-genome sequencing of 30 M. abscessus strains, were also correctly identified by GenSeizer 100% of the time. These results indicate that GenSeizer is an efficient, reliable platform for detecting major pathogenic Mycobacterium species.

A novel DNA chromatography method to discriminate Mycobacterium abscessus subspecies and macrolide susceptibility

Background

The clinical impact of infection with Mycobacterium (M.) abscessus complex (MABC), a group of emerging non-tuberculosis mycobacteria (NTM), is increasing. M. abscessus subsp. abscessus/bolletii frequently shows natural resistance to macrolide antibiotics, whereas M. abscessus subsp. massiliense is generally susceptible. Therefore, rapid and accurate discrimination of macrolide-susceptible MABC subgroups is required for effective clinical decisions about macrolide treatments for MABC infection. We aimed to develop a simple and rapid diagnostic that can identify MABC isolates showing macrolide susceptibility.

Methods

Whole genome sequencing (WGS) was performed for 148 clinical or environmental MABC isolates from Japan to identify genetic markers that can discriminate three MABC subspecies and the macrolide-susceptible erm(41) T28C sequevar. Using the identified genetic markers, we established PCR based- or DNA chromatography-based assays. Validation testing was performed using MABC isolates from Taiwan.

Finding

We identified unique sequence regions that could be used to differentiate the three subspecies. Our WGS-based phylogenetic analysis indicated that M. abscessus carrying the macrolide-susceptible erm(41) T28C sequevar were tightly clustered, and identified 11 genes that were significantly associated with the lineage for use as genetic markers. To detect these genetic markers and the erm(41) locus, we developed a DNA chromatography method that identified three subspecies, the erm(41) T28C sequevar and intact erm(41) for MABC in a single assay within one hour. The agreement rate between the DNA chromatography-based and WGS-based identification was 99·7%.

Interpretation

We developed a novel, rapid and simple DNA chromatography method for identification of MABC macrolide susceptibility with high accuracy.

Funding

AMED, JSPS KAKENHI

Parotitis caused by Mycobacteroides abscessus subspecies abscessus

Rapidly growing mycobacteria rarely causes parotitis. We report a rare case of Mycobacteroides abscessus subspecies abscessus (MAB) parotitis in a previously healthy 26-year-old woman. She presented to the previous hospital with a swelling over the right parotid region, and a computed tomography scan revealed multiple abscesses in the swollen parotid gland. Histopathology showed granulomatous inflammation with acid-fast bacilli; however, a subsequent culture failed to isolate mycobacterium. Despite repeated antibiotic therapy and multiple surgical interventions including partial incision and drainage of the abscesses, the parotitis did not resolved. At six months after presentation, she was referred to our institute. We performed enlarged resection of the necrotic tissue and abscesses, and the sample cultivated after homogenization was positive for mycobacterium. The isolate was finally identified as MAB. She underwent long-term postoperative antibiotic therapy for MAB, with a favorable outcome. To the best of our knowledge, this is the first case of MAB parotitis where the subspecies has been identified. MAB is much more intractable than the other subspecies. We highlight the importance of the correct identification of MAB, which leads to the appropriate treatment.

Antimicrobial Susceptibility and Phylogenetic Relations in a German Cohort Infected with Mycobacterium abscessus

Mycobacterium abscessus is a highly antibiotic-resistant opportunistic pathogen causing clinically challenging infections in patients with preexisting lung diseases or under immunosuppression. Hence, reliable antibiotic susceptibility data are required for effective treatment. Aims of this study were to investigate (i) the congruence of genotypic and phenotypic antimicrobial susceptibility testing, (ii) the relationship between resistance profile and clinical course, and (iii) the phylogenetic relations of M. abscessus in a German patient cohort. A total of 39 isolates from 29 patients infected or colonized with M. abscessus underwent genotypic and phenotypic drug susceptibility testing. Clinical data were correlated with susceptibility data. Phylogenetic analysis was performed by means of whole-genome sequencing (WGS) and single-nucleotide polymorphism (SNP) analysis. Macrolide resistance was mainly mediated by functional Erm(41) methyltransferases (T28 sequevars) in M. abscessus subsp. abscessus (n = 25) and M. abscessus subsp. bolletii (n = 2). It was significantly associated with impaired culture conversion (P = 0.02). According to the core SNP phylogeny, we identified three clusters of closely related isolates with SNP distances below 25. Representatives of all circulating global clones (Absc. 1, Absc. 2, and Mass. 1) were identified in our cohort. However, we could not determine evidence for in-hospital interhuman transmission from clinical data. In our patient cohort, we identified three M. abscessus clusters with closely related isolates and representatives of the previously described international clusters but no human-to-human in-hospital transmission. Macrolide and aminoglycoside susceptibility data are critical for therapeutic decision-making in M. abscessus infections.

Immune defects in patients with pulmonary Mycobacterium abscessus disease without cystic fibrosis

The prevalence of Mycobacterium abscessus infections in non-cystic fibrosis (CF) patients has increased in recent years. In this study, we investigate whether immune defects explain the apparent susceptibility to this opportunistic infection in non-CF patients.

We performed stimulations of peripheral blood mononuclear cells and whole blood from 13 patients with M. abscessus pulmonary disease and 13 healthy controls to investigate their cytokine production after 24 h and 7 days.

Patients were predominantly women (54%) with a mean age of 59 years; 62% had nodular bronchiectatic disease. Many patients had predisposing pulmonary diseases, such as COPD (46%), and asthma (23%). Patients with COPD showed an impaired interleukin (IL)-6 response to M. abscessus and a reduced IL-17 response to Candida, together with a M. abscessus-specific enhanced IL-22 production. Patients without COPD showed higher levels of interleukin-1 receptor antagonist (IL-1Ra), an anti-inflammatory molecule. Within the non-COPD patients, those with bronchiectasis showed defective interferon (IFN)-γ production in response to Candida albicans.

In conclusion, susceptibility to M. abscessus is likely determined by a combination of immunological defects and predisposing pulmonary disease. The main defect in the innate immune response was a shift of the ratio of IL-1β to IL-1Ra, which decreased the bioactivity of this pathway in the adaptive immune response. In the adaptive immune response there was defective IL-17 and IFN-γ production. Patients with COPD and bronchiectasis showed different cytokine defects. It is therefore crucial to interpret the immunological results within the clinical background of the patients tested.

Measurement of defects in both the innate and adaptive immune responses in patients with M. abscessus pulmonary disease show that susceptibility to M. abscessus is determined by a combination of immunological defects and predisposing pulmonary diseasehttps://bit.ly/2DtbycY

New-onset nontuberculous mycobacterial pulmonary disease in bronchiectasis: tracking the clinical and radiographic changes

Background

The close association between bronchiectasis and nontuberculous mycobacterial pulmonary disease (NTM-PD) is well-known. However, the clinical impact of subsequent new-onset NTM-PD in bronchiectasis patients has not been elucidated. The aim of this study is to investigate the clinical courses and radiographic changes of patients with bronchiectasis in whom NTM-PD subsequently developed.

Methods

A total of 221 patients with bronchiectasis who had participated in a non-NTM bronchiectasis cohort between July 1st 2011 and August 31st 2019 at Seoul National University Hospital were included in this study. The data of patients in whom NTM-PD developed during this observation period were analyzed; specifically, changes in the Bronchiectasis Severity Index (BSI) and lesions on computerized tomography (CT) scan of the chest arising during the observation period.

Results

During the observation period, NTM was isolated from 35 patients. A total of 31 patients (14.0%) satisfied the diagnostic criteria of NTM-PD. The median time from enrollment in the cohort to the development of subsequent NTM-PD was 37 months (Interquartile range [IQR], 18–78 months). Mycobacterium avium complex was the most common pathogen (80.6%). Twelve patients underwent antibiotic treatment for NTM-PD with a median interval of 20 months (IQR, 13–30) from the time of NTM-PD diagnosis. When NTM-PD developed, the severity and extent of bronchiectasis, cellular bronchiolitis, and the extent of nodules worsened on CT scans, while BSI did not change.

Conclusions

NTM-PD can develop in previously negative bronchiectasis patients. It is associated with worsening radiographic lesions. Active screening of non-NTM bronchiectasis patients for new-onset NTM infection should be considered, especially if radiographic findings worsen. The BSI is not a reliable predictor of new-onset NTM-PD.

Trial registration

This study was performed at Seoul National University Hospital (NCT01616745).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-020-01331-3.

MmpL3 Inhibition: A New Approach to Treat Nontuberculous Mycobacterial Infections

Outside of Mycobacterium tuberculosis and Mycobacterium leprae, nontuberculous mycobacteria (NTM) are environmental mycobacteria (>190 species) and are classified as slow- or rapid-growing mycobacteria. Infections caused by NTM show an increased incidence in immunocompromised patients and patients with underlying structural lung disease. The true global prevalence of NTM infections remains unknown because many countries do not require mandatory reporting of the infection. This is coupled with a challenging diagnosis and identification of the species. Current therapies for treatment of NTM infections require multidrug regimens for a minimum of 18 months and are associated with serious adverse reactions, infection relapse, and high reinfection rates, necessitating discovery of novel antimycobacterial agents. Robust drug discovery processes have discovered inhibitors targeting mycobacterial membrane protein large 3 (MmpL3), a protein responsible for translocating mycolic acids from the inner membrane to periplasm in the biosynthesis of the mycobacterial cell membrane. This review focuses on promising new chemical scaffolds that inhibit MmpL3 function and represent interesting and promising putative drug candidates for the treatment of NTM infections. Additionally, agents (FS-1, SMARt-420, C10) that promote reversion of drug resistance are also reviewed.

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.

Minimal Inhibitory Concentration of Clofazimine Among Clinical Isolates of Nontuberculous Mycobacteria and Its Impact on Treatment Outcome

BACKGROUND

Clofazimine has been regarded as a promising agent for the treatment of nontuberculous mycobacteria pulmonary disease (NTM-PD). However, its overall effectiveness in vitro and in the clinic remains unknown.

RESEARCH QUESTION

What is the minimal inhibitory concentration (MIC) of clofazimine in clinical isolates and the association between MICs and treatment outcome?

STUDY DESIGN AND METHODS

MICs for clofazimine were measured in clinical isolates from NTM-PD patients who participated in a prospective study at Seoul National University Hospital. The MIC was determined by using the broth microdilution concentration method. Correlation between MIC and conversion to negative of sputum culture with clofazimine was determined.

RESULTS

Of a total 189 isolates, 133 strains were Mycobacterium avium complex (MAC) and 40 strains were M abscessus. Although the clofazimine MICs for MAC ranged from 0.031 mg/L to 8 mg/L, the values obtained for M abscessus ranged from 0.031 mg/L to 16 mg/L. Of 20 patients who were treated with a regimen including clofazimine, eight achieved negative conversion of sputum culture. All patients with isolates exhibiting clofazimine MIC values ≤ 0.25 mg/L achieved culture conversion. The likelihood of culture conversion in patients with MIC value ≤ 0.25 mg/L was much higher than that of patients with MIC value > 0.5 mg/L (OR, 39.3; P = .021).

INTERPRETATION

The MICs of clofazimine varied widely in clinical isolates from patients with NTM-PD. Negative conversion of sputum culture with clofazimine use was associated with a lower MIC value. Clofazimine use could be considered in patients with NTM-PD when the MIC value is ≤ 0.25 mg/L.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01616745; URL: www.clinicaltrials.gov.

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.

Antimicrobial Susceptibility of Mycobacterium abscessus Complex Clinical Isolates from a Chinese Tertiary Hospital

Introduction

Mycobacterium abscessus complex (MABC) is a group of important infectious agents that are highly associated with drug resistance, and antibiotic treatment is usually ineffective. This study investigated the characteristics of antimicrobial susceptibility of MABC isolates and the synergy between certain β-lactam combinations against MABC infection.

Methods

We collected 129 MABC isolates from patients with lower respiratory tract infections and categorized them into three subspecies. The minimum inhibitory concentrations (MICs) of 15 antimicrobials for the MABC isolates were determined using commercial Sensititre RAPMYCOI MIC plates and the broth microdilution method, as recommended in the CLSI (M24-A2). In addition, the MICs of imipenem, alone and with ceftazidime and/or avibactam, were assessed in vitro for all isolates. The erm(41) and rrl genes were also sequenced.

Results

The MABC isolates exhibited >80% resistance to 11 of the 15 antimicrobials. Regarding the remaining four antimicrobials, the isolates were least resistant to tigecycline (12.4%) and amikacin (3.9%), and only partially resistant to two cefoxitin (39.5%) and imipenem (40.3%). Compared with M. massiliense isolates, M. abscessus and M. bolletii isolates were more resistant to amikacin and imipenem, whereas M. abscessus was significantly less resistant to tigecycline relative to M. massiliense and M. bolletii isolates. The clarithromycin inducible resistance rate was 68.4% and 74.3% among M. bolletii and M. abscessus isolates. Furthermore, 88.7% of the M. abscessus isolates carried a T at position 28 of erm(41), which is associated with inducible clarithromycin resistance. In addition, compared to imipenem with avibactam only, the MIC₅₀ and MIC₉₀values of imipenem after adding ceftazidime plus avibactam were decreased fourfold.

Conclusion

The antimicrobial resistance rates and the characteristics of the erm(41) gene associated with inducible clarithromycin resistance were different among the three MABC subspecies. There was also synergy between imipenem and 100μg/mL ceftazidime against MABC isolates.

In vitro efficacy of combinations of eight antimicrobial agents against Mycobacteroides abscessus complex

OBJECTIVES

A standard treatment regimen against Mycobacteroides abscessus complex (MABC) infections has not yet been established, making MABC difficult to treat successfully. In this study, we sought to develop an active ingredient for the clinical treatment of MABC infections.

METHODS

We screened 102 MABC strains isolated from clinical specimens using DNA sequence analysis with the housekeeping genes hsp65 and rpoB. Drug susceptibility testing was performed against two subspecies-Mycobacteroides abscessus subsp. abscessus (M. abscessus) and Mycobacteroides abscessus subsp. massiliense (M. massiliense)-using eight antimicrobial agents (clarithromycin, amikacin, doxycycline, imipenem, linezolid, moxifloxacin, faropenem, and rifampicin). The combined efficacy of the antimicrobial agents was investigated using a checkerboard method.

RESULTS

We identified 51 isolates as M. abscessus, 46 as M. massiliense, and five as others. Most of the M. abscessus isolates (83.0 %) exhibited inducible resistance to clarithromycin via the expression of the erm(41) gene. Combinations of imipenem with linezolid, moxifloxacin, and rifampicin exhibited additive effects against 81.0 %, 40.7 %, and 26.9 % of M. abscessus, respectively, and against 54.5 %, 69.2 %, and 30.8 % of M. massiliense, respectively.

CONCLUSIONS

These results demonstrated the potential efficacy of a regimen containing imipenem against M. abscessus and M. massiliense infections.

Treatment for Mycobacterium abscessus complex-lung disease

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