Causative species of nontuberculous mycobacterial lung disease and comparative investigation on clinical features of Mycobacterium abscessus complex disease: A retrospective analysis for two major hospitals in a subtropical region of Japan

The epidemiology of pulmonary Mycobacterium abscessus species in Japanese population

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Global Epidemiology of Nontuberculous Mycobacterial Pulmonary Disease: A Review

Nontuberculous mycobacterial (NTM) isolation and pulmonary disease (NTM-PD) have continued to increase in most regions of the world, driven mainly by Mycobacterium avium. Single-center studies also support increasing trends as well as a persistent burden of undiagnosed NTM among persons suspected of having tuberculosis (TB), in countries with moderate-to-high TB prevalence. Cumulative exposure to water and soil presents an increased risk to susceptible hosts, and trace metals in water supply are recently recognized risk factors. Establishing standard case definitions for subnational and national surveillance systems with mandatory notification of NTM-PD are needed to allow comparisons within and across countries and regions.

Risk Factors for Nontuberculous Mycobacterial Pulmonary Disease: A Systematic Literature Review and Meta-Analysis

BACKGROUND

Nontuberculous mycobacterial pulmonary disease (NTM-PD) is widely underdiagnosed, and certain patient groups, such as those with underlying respiratory diseases, are at increased risk of developing the disease. Understanding patients at risk is essential to allow for prompt testing and diagnosis and appropriate management to prevent disease progression.

RESEARCH QUESTION

What are the risk factors for NTM-PD that should prompt a physician to consider NTM testing and diagnosis?

STUDY DESIGN AND METHODS

Electronic searches of PubMed and EMBASE were conducted in July 2021 for the period 2011-2021. Inclusion criteria were studies of patients with NTM-PD with associated risk factors. Data were extracted and assessed using the Newcastle-Ottawa Scale. Data analysis was conducted using the R-based "meta" package. Only studies that reported association outcomes for cases with NTM-PD compared with control participants (healthy populations or participants without NTM-PD) were considered for the meta-analysis.

RESULTS

Of the 9,530 searched publications, 99 met the criteria for the study. Of these, 24 formally reported an association between possible risk factors and the presence of NTM-PD against a control population and were included in the meta-analysis. Comorbid respiratory disease was associated with a significant increase in the OR for NTM-PD (bronchiectasis [OR, 21.43; 95% CI, 5.90-77.82], history of TB [OR, 12.69; 95% CI, 2.39-67.26], interstitial lung disease [OR, 6.39; 95% CI, 2.65-15.37], COPD [OR, 6.63; 95% CI, 4.57-9.63], and asthma [OR, 4.15; 95% CI, 2.81-6.14]). Other factors noted to be associated with an increased risk of NTM-PD were the use of inhaled corticosteroids (OR 4.46; 95% CI, 2.13-9.35), solid tumors (OR, 4.66; 95% CI, 1.04-20.94) and the presence of pneumonia (OR, 5.54; 95% CI, 2.72-11.26).

INTERPRETATION

The greatest risk for NTM-PD is conferred by comorbid respiratory diseases such as bronchiectasis. These findings could help with identification of patient populations at risk for NTM-PD to drive prompt testing and appropriate initiation of therapy.

Epidemiology of Mycobacterium abscessus

BACKGROUND

Nontuberculous mycobacteria (NTM) are highly abundant in soil, dust, and water sources, making human-pathogen contact frequent and recurrent. NTM represents over 200 species/subspecies; some are considered strict or opportunistic pathogens. Mycobacterium abscessus, often regarded as one of the most antibiotic-resistant mycobacteria, is the second most frequent NTM pulmonary disease pathogen.

OBJECTIVES

To describe the epidemiology of M. abscessus through a literature review focusing on clinical aspects.

SOURCES

We conducted searches on PubMed and Web of Knowledge for articles published from 2010 to the present using the keywords 'Mycobacterium abscessus', 'Nontuberculous mycobacteria', and 'epidemiology'. Our search prioritized original reports on the occurrence of NTM and M. abscessus infection/disease.

CONTENT

Advanced molecular and genetic diagnostic techniques have refined the M. abscessus complex (MABC) microbiological classification over the last few decades. MABC can adhere to surfaces and form a biofilm. This characteristic and its resistance to common disinfectants allow these microorganisms to persist in the water distribution systems, becoming a constant reservoir. The frequency and manifestation of NTM species vary geographically because of environmental conditions and population susceptibility differences. MABC lung disease, the most frequent site of NTM infection in humans, is often seen in patients with underlying lung diseases such as bronchiectasis, whereas MABC disseminated disease is related to immunosuppression. Skin and soft tissue infections are associated with surgical or injection procedures. Epidemiological evidence suggests an overall increase in MABC infection and disease in the last decade.

IMPLICATIONS

Establishing the burden of this disease is challenging because of varying measures of incidence and prevalence, referral bias, and differences in medical practices and reporting. Furthermore, environmental and structural determinants, infection routes, and MABC pulmonary disease mechanisms require additional investigation. This review contributes to a better understanding of the epidemiology of MABC, which could inform clinical practice and future research.

Prevalence of systemic and local risk factors for pulmonary non-tuberculous mycobacterial disease in Japan: a single-institution study

Objective: To identify the prevalence of risk factors for pulmonary non-tuberculous mycobacterial (NTM) disease in a Japanese population. Patients and Methods: We reviewed 337 consecutive Japanese patients (210 women) with pulmonary NTM disease, including 225 patients with Mycobacterium avium complex (MAC) disease (95.8%) at our hospital during 2006-2017. We calculated the prevalence of risk factors reported in Western countries among mycobacterial species. Results: Pulmonary MAC disease cases comprised 78.2% of pulmonary NTM patients in their 40s, increasing to 100% at age ≥80 years. Body mass index (BMI) was <18.5 in approximately 40% of patients, which was significantly higher than the prevalence of underweight in the Japanese population. The percentage of male heavy smokers (Brinkman index ≥600) was 58.2% of pulmonary NTM disease and was high for all mycobacterial species. In pulmonary MAC disease, systemic factors were observed in the order of malignant tumors (other than lung cancer), diabetes, rheumatoid arthritis, and tuberculosis. Local factors were observed in the order of bronchiectasis, chronic obstructive pulmonary disease, lung cancer, and bronchial asthma. Conclusion: The risk factors reported in Western countries were relatively highly prevalent among Japanese pulmonary NTM disease patients. This observation may help elucidate disease onset mechanisms.

The synergetic effect of sitafloxacin-arbekacin combination in the Mycobacterium abscessus species

Mycobacterium abscessus species (MABS) is the most commonly isolated rapidly growing mycobacteria (RGM) and is one of the most antibiotic-resistant RGM with rapid progression, therefore, treatment of MABS is still challenging. We here presented a new combination treatment with sitafloxacin that targeted rough morphotypes of MABS, causing aggressive infections. Thirty-four clinical strains of MABS were isolated from various clinical samples at the Juntendo university hospital from 2011 to 2020. The susceptibility to a combination of sitafloxacin and antimicrobial agents was compared to that of the antimicrobial agents alone. Out of 34 MABS, 8 strains treated with sitafloxacin-amikacin combination, 9 of sitafloxacin-imipenem combination, 19 of sitafloxacin-arbekacin combination, and 9 of sitafloxacin-clarithromycin combination showed synergistic effects, respectively. Sitafloxacin-arbekacin combination also exhibited the synergistic effects against 10 of 22 Mycobacterium abscessus subspecies massiliense (Mma) strains and 8 of 11 Mycobacterium abscessus subspecies abscessus (Mab) strains, a highly resistant subspecies of MABS. The sitafloxacin-arbekacin combination revealed more synergistic effects in rough morphotypes of MABS (p = 0.008). We demonstrated the synergistic effect of the sitafloxacin-arbekacin combination against MABS. Further, this combination regimen might be more effective against Mab or rough morphotypes of MABS.

Genomic Analysis of Mycobacterium abscessus Complex Isolates from Patients with Pulmonary Infection in China

Members of the Mycobacterium abscessus complex (MABC) are multidrug-resistant nontuberculous mycobacteria and increasingly cause opportunistic pulmonary infections. However, the genetic typing of MABC isolates remains largely unclear in China. Genomic analyses were conducted for 69 MABC clinical isolates obtained from patients with lower respiratory tract infections in Shanghai Pulmonary Hospital between 2014 and 2016. The draft genomes of the 69 clinical strains were assembled, with a total length of 4.5 to 5.6 Mb, a percent GC content (GC%) ranging from 63.9 to 68.1%, and 4,492 to 5,404 genes per genome. Susceptibility test shows that most isolates are resistant to many antimicrobials, including clarithromycin, but susceptible to tigecycline. Analyses revealed the presence of genes conferring resistance to antibiotics, including macrolides, aminoglycosides, rifampicin, and tetracyclines. Furthermore, 80 to 114 virulence genes were identified per genome, including those related to the invasion of macrophages, iron incorporation, and avoidance of immune clearance. Mobile genetic elements, including insertion sequences, transposons, and genomic islands, were discovered in the genomes. Phylogenetic analyses of all MABC isolates with another 41 complete MABC genomes identified three clades; 46 isolates were clustered in clade I, corresponding to M. abscessus subsp. abscessus, and 25 strains belonged to existing clonal complexes. Overall, this is the first comparative genomic analysis of MABC clinical isolates in China. These results show significant intraspecies variations in genetic determinants encoding antimicrobial resistance, virulence, and mobile elements and controversial subspecies classification using current marker gene combinations. This information will be useful in understanding the evolution, antimicrobial resistance, and pathogenesis of MABC strains and facilitating future vaccine development and drug design. IMPORTANCE Over the past decade, infections by Mycobacterium abscessus complex (MABC) isolates have been increasingly reported worldwide. MABC strains often show a high incidence in cystic fibrosis (CF) patients, whereas in Asia, these strains are frequently recovered from non-CF patients with significant genomic diversity. The present work involves analyses of the antimicrobial resistance, virulence, and phylogeny of 69 selected MABC isolates from non-CF pulmonary patients in Shanghai Pulmonary Hospital by whole-genome sequencing; it represents the first comprehensive investigation of MABC strains in China at the genomic level. These findings highlight the diversity of this group of nontuberculous mycobacteria and provide a mechanistic understanding of evolution and pathogenesis, which is valuable for the development of novel and effective antimicrobial therapies for deadly MABC infections in China.

Radiological findings in nontuberculous mycobacterial pulmonary diseases: A comparison between the Mycobacterium avium complex and the Mycobacterium abscessus complex

The Mycobacterium abscessus complex (MABC) comprises rapidly growing mycobacteria and has received increasing attention recently, with an increasing number of associated infections reported worldwide. However, the clinical features of MABC pulmonary disease (MABC-PD), especially in terms of the chest computed tomography (CT) findings, are not fully understood. Thus, this retrospective, cross-sectional study aimed to evaluate the clinical background and chest high-resolution CT (HRCT) findings of MABC-PD in comparison with those of Mycobacterium avium complex PD (MAC-PD). Accordingly, 36 patients with MABC-PD and 65 patients with MAC-PD (defined according to the American Thoracic Society criteria), who were newly diagnosed at four major hospitals in Okinawa (Japan) between January 2012 and December 2017, were analyzed. With respect to their clinical background, only cardiovascular diseases were significantly more common in patients with MABC-PD than in those with MAC-PD (38.9% vs. 18.5%, p = 0.0245). HRCT revealed a significantly higher incidence of low attenuation in patients with MABC-PD than in those with MAC-PD (63.9% vs. 10.8%, p<0.0001). On analyzing only never-smokers (20 and 47 patients with MABC-PD and MAC-PD, respectively), this significant difference remained (65.0% vs. 8.5%, p<0.0001), suggesting MABC infection itself caused low attenuation. In terms of the distribution of abnormal shadows, the involvement of the right lower, left upper, and left lower lobes was more common in patients with MABC-PD than in those with MAC-PD. Furthermore, the mean number of involved lung lobes was significantly higher in patients with MABC-PD than in those with MAC-PD (5.6 vs. 4.7, p<0.001). Although further studies are needed, we assume that the aforementioned radiological features of MABC-PD are due to the high virulence of MABC.

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.

Exploring Potential COPD Immunosuppression Pathways Causing Increased Susceptibility for MAC Infections among COPD Patients

Although there has been a drastic decline in the cases of Tuberculosis in the United States, the prevalence of infections caused by Mycobacterium avium Complex (MAC) has steadily increased in the past decades. Mycobacterium avium (M. avium) is one of the most abundant microorganisms in the MAC species. The mycobacterium genus is divided into two major groups: tuberculosis causing mycobacteria and non-tuberculous mycobacteria. MAC is most prominent among the non-tuberculous mycobacteria. MAC is an opportunistic pathogen that is present in soil, water, and droplets in the air. MAC infections can result in respiratory disease and can disseminate in affected patients. MAC infections are especially prevalent in patients with preexisting respiratory conditions such as Chronic Obstructive Pulmonary Disease (COPD). COPD is one of the most common lung conditions in the world with the primary cause being smoking in developed countries. COPD involves chronic inflammation of lung tissue resulting in increased susceptibility to infection. There is a lack of research regarding the pathophysiology that leads COPD patients to be susceptible to MAC infection. Our review paper therefore aims to investigate how the pathogenicity of MAC bacteria and immune decline seen in COPD patients leads to a greater susceptibility to MAC infection among COPD patients.

Longitudinal non-cystic fibrosis trends of pulmonary Mycobacterium abscessus disease from 2010 to 2017: spread of the "globally successful clone" in Asia

BACKGROUND

Mycobacterium abscessus (MAB) has emerged as the predominant pulmonary non-tuberculous mycobacterial pathogen in parts of Asia, including Taiwan. The reasons for the significant increase in MAB infections in the non-cystic fibrosis (CF) populations are poorly understood. The study aimed to elucidate whether this increase is related to the spread of the globally successful clone of MAB.

METHODS

We performed multilocus sequence typing of 371 nonduplicated MAB pulmonary isolates from 371 patients sampled between 2010-2017 at seven hospitals across Taiwan.

RESULTS

In total, 183 (49.3%) isolates were M. abscessus subsp. abscessus (MAB-a), 187 (50.4%) were M. abscessus subsp. massiliense (MAB-m), and 1 (0.3%) was M. abscessus subsp. bolletii (MAB-b). MAB-a sequence type (ST)1 (23.7%) and ST127 (3.8%), followed by MAB-m ST48 (16.2%), ST117 (15.1%), ST23 (8.6%) were most common overall. Of MAB-a strains, 50 (27.3%) belonged to novel STs and 38 (10.2%) were singleton strains, while of MAB-m strains, only 10 (5.3%) were novel and 8 (2.2%) were singletons. From 2010 to 2017, the frequency of the historically dominant ST1 declined from 28.6% to 22.5%, whereas the recently emerged globally successful clonal cluster 3, ST23 and ST48, increased from 14.3% to 40.0%.

CONCLUSIONS

The dominance of ST1 particularly in the last 2 years of this study appears to be declining, while ST23, reported in outbreaks among CF and post-surgical cohorts across the Americas and Europe, alongside the closely related ST48, is present among non-CF populations in Taiwan. These trends need to be confirmed with further ongoing studies to track the molecular epidemiology of clinical MAB isolates worldwide.

Species identification and antimicrobial susceptibility testing of non-tuberculous mycobacteria isolated in Chongqing, Southwest China

With the rapid rise in the prevalence of non-tuberculous mycobacteria (NTM) diseases across the world, the microbiological diagnosis of NTM isolates is becoming increasingly important for the diagnosis and treatment of NTM disease. In this study, the clinical presentation, species distribution and drug susceptibility of patients with NTM disease visiting the Chongqing Public Health Medical Centre during March 2016-April 2019 were retrospectively analysed. Among the 146 patients with NTM disease, eight NTM species (complex) were identified. The predominant NTM species in these patients were identified to be Mycobacterium abscessus complex (53, 36.3%), M. intracellulare (38, 26%) and M. fortuitum (17, 11.7%). In addition, two or more species were isolated from 7.5% of the patients. Pulmonary NTM disease (142, 97.3%) showed the highest prevalence among the patients. It was observed that 40.1% of the patients with pulmonary NTM disease had chronic pulmonary obstructive disease and bronchiectasis, while 22.5% had prior tuberculosis. Male patients showed more association with the conditions of cough and haemoptysis than the female patients. In an in vitro antimicrobial susceptibility testing, most of the species showed susceptibility to linezolid, amikacin and clarithromycin, while M. fortuitum exhibited low susceptibility to tobramycin. In conclusion, the prevalence of NTM disease, especially that of the pulmonary NTM disease, is common in Southwest China. Species identification and drug susceptibility testing are thus extremely important to ensure appropriate treatment regimens for patient care and management.

Improvement of multiple intraperitoneal nodules resembling peritoneal cancer that developed after peritoneal dialysis-related peritonitis caused by Mycobacterium abscessus with literature review: granuloma or carcinoma

Introduction

Peritonitis is a crucial complication that leads to hospitalization or even death in patients who are undergoing peritoneal dialysis (PD). The incidence of PD-related peritonitis associated with nontuberculous mycobacteria has increased in recent years. However, a well-established treatment for peritonitis is lacking, particularly in peritonitis caused by Mycobacterium abscessus which is a difficult to treat disease due to its inherent resistance to majority of available antibiotics. To the best of our knowledge, this case is the first to report on intraperitoneal multiple nodules that developed due to PD-related peritonitis caused by M. abscessus.

Case presentation

This case reported a case of a 40-year-old female patient who was undergoing PD and who showed multiple intraperitoneal nodules that resembled peritoneal cancer on computed tomography (CT) and that developed after PD-related peritonitis and catheter removal. After multiantibiotic therapy, multiple nodules were found to have disappeared on CT. The nodules continued to disappear and the patient did not show signs of recurrent peritonitis, although there was a possibility of recurrence.

Conclusion

To the best of our knowledge, this case is the first to report on nodules that resembled peritoneal cancer and that developed in the abdominal cavity due to PD-related peritonitis caused by M. abscessus. Positron emission tomography–CT was not useful in distinguishing peritoneal cancer from nodules caused by M. abscessus.

Single Cell Analysis of Drug Susceptibility of Mycobacterium Abscessus During Macrophage Infection

Mycobacterium abscessus is an emerging health risk to immunocompromised individuals and to people with pre-existing pulmonary conditions. As M. abscessus possesses multiple mechanisms of drug resistance, treatments of M. abscessus are of poor efficacy. Therefore, there is an urgent need for new therapeutic strategies targeting M. abscessus. We describe an experimental system for screening of compounds for their antimicrobial activity against intracellular M. abscessus using flow cytometry and imaging flow cytometry. The assay allows simultaneous analysis of multiple parameters, such as proportion of infected host cells, bacterial load per host cell from the infected population, and host cell viability. We verified the suitability of this method using two antibiotics with known activity against M. abscessus: clarithromycin and amikacin. Our analysis revealed a high degree of infection heterogeneity, which correlated with host cell size. A higher proportion of the larger host cells is infected with M. abscessus as compared to smaller host cells, and infected larger cells have higher intracellular bacterial burden than infected smaller cells. Clarithromycin treatment has a more pronounced effect on smaller host cells than on bigger host cells, suggesting that heterogeneity within the host cell population has an effect on antibiotic susceptibility of intracellular bacteria.

THP-1 and Dictyostelium Infection Models for Screening and Characterization of Anti-Mycobacterium abscessus Hit Compounds

!!NCR1!! presents a great challenge to antimycobacterial therapy due to its innate resistance against most antibiotics. M. abscessus is able to grow intracellularly in human macrophages, suggesting that intracellular models can facilitate drug discovery. Thus, we have developed two host cell models: human macrophages for use in a new high-content screening method for M. abscessus growth and a Dictyostelium discoideum infection model with the potential to simplify downstream genetic analysis of host cell factors. A screen of 568 antibiotics for activity against intracellular M. abscessus led to the identification of two hit compounds with distinct growth inhibition. A collection of 317 human kinase inhibitors was analyzed, with the results yielding three compounds with an inhibitory effect on mycobacterial growth, strengthening the notion that host-directed therapy can be applied for M. abscessus.

Thiostrepton: A Novel Therapeutic Drug Candidate for Mycobacterium abscessus Infection

Mycobacterium abscessus is a rapid-growing, multidrug-resistant, non-tuberculous mycobacterial species responsible for a variety of human infections, such as cutaneous and pulmonary infections. M. abscessus infections are very difficult to eradicate due to the natural and acquired multidrug resistance profiles of M. abscessus. Thus, there is an urgent need for the development of effective drugs or regimens against M. abscessus infections. Here, we report the activity of a US Food and Drug Administration approved drug, thiostrepton, against M. abscessus. We found that thiostrepton significantly inhibited the growth of M. abscessus wild-type strains, subspecies, clinical isolates, and drug-resistant mutants in vitro and in macrophages. In addition, treatment of macrophages with thiostrepton significantly decreased proinflammatory cytokine production in a dose-dependent manner, suggesting an inhibitory effect of thiostrepton on inflammation induced during M. abscessus infection. We further showed that thiostrepton exhibits antimicrobial effects in vivo using a zebrafish model of M. abscessus infection.

Mycobacterium shimoidei, a rare non-tuberculous mycobacteria pathogen identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Non-tuberculous mycobacteria (NTM) cause several infectious diseases in humans. This study reports on Mycobacterium shimoidei infection in an immunosuppressed 61-year-old male with a background of emphysema. His chief complaint was haemoptysis. Chest computed tomography showed a large, thin-walled cavitary lesion in the upper right lobe. Although NTM were identified in two separate expectorated sputum samples, DNA-DNA hybridization (DDH) failed to identify the species. M. shimoidei was finally identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Following antimicrobial agent susceptibility tests, treatment with clarithromycin, levofloxacin, and ethambutol commenced. Six months post-treatment, acid-fast sputum culture was negative and repeat imaging demonstrated improvement of the radiographic abnormalities. This study aimed to assess the utility of MALDI-TOF MS for successful identification of rare NTM species that are not identifiable by DDH. It is the first report of M. shimoidei from Okinawa, which is the only prefecture in Japan categorized as subtropical.

Clinical and microbiological characteristics of non-tuberculous mycobacteria diseases in Singapore with a focus on pulmonary disease, 2012-2016

Background

Information on non-tuberculosis mycobacterial (NTM) diseases remains limited in Singapore and other Southeast Asian countries. This study aimed to delineate epidemiological and clinical features of pulmonary NTM disease.

Methods

A retrospective review was performed on all NTM isolates identified in Singapore General Hospital from 2012 to 2016 using the 2007 ATS/IDSA diagnostic criteria.

Results

A total of 2026 NTM isolates from 852 patients were identified. M. abscessus-chelonae group (1010, 49.9%) was the most commonly isolated and implicated in pulmonary NTM disease. Pulmonary cases (352, 76%) had the highest prevalence among patients diagnosed with NTM diseases (465/852, 54.6%) with no gender difference. Male patients were older (68.5 years, P = 0.014) with a higher incidence of chronic obstructive pulmonary disease (COPD) (23.6%, P < 0.001) and recurrent cough with phlegm production (51.6%, P = 0.035). In contrast, more female patients had bronchiectasis (50%, P < 0.001) and haemoptysis (37.6%, P = 0.042). Age and COPD were associated with multiple NTM species isolation per patient.

Conclusions

M. abscessus-chelonae group was the commonest NTM species isolated in Singapore. Pulmonary NTM infection has the highest frequency with male and female patients associated with a higher incidence of COPD and bronchiectasis respectively. Age and COPD were associated with multiple NTM species isolation per patient.

In Vitro and Intracellular Activity of Imipenem Combined with Tedizolid, Rifabutin, and Avibactam against Mycobacterium abscessus

Mycobacterium abscessus infections are difficult to treat because of their resistance to many antibiotics. In vitro, tedizolid combined with imipenem displayed a moderate synergistic effect (fractional inhibitory concentration index, 0.41) but no bactericidal activity. Intracellularly, tedizolid 2 μg/ml (half of the MIC), corresponding to the peak serum concentration, increased the efficacy of imipenem at 8 and 32 μg/ml. Addition of avibactam and rifabutin, alone or in combination, improved the activity of the imipenem-tedizolid combination.

Pulmonary Mycobacterium abscessus Infection with Reactive AA Amyloidosis: A Case Report and Brief Review of the Literature

We herein report a case involving a 64-year-old Japanese woman with a pulmonary Mycobacterium abscessus infection complicated by reactive AA amyloidosis, which, to our knowledge, has not been reported to date. The patient underwent gastrointestinal endoscopy for diarrhea during the treatment of pulmonary M. abscessus infection and was diagnosed with AA amyloidosis according to the histopathological findings from the endoscopic specimen. She died four months later. The prognosis of AA amyloidosis associated with pulmonary M. abscessus infection may be very poor, and physicians should pay attention to this rare condition when difficult-to-treat diarrhea occurs in patients with pulmonary M. abscessus infection.

Mycobacterium abscessus: Shapeshifter of the Mycobacterial World

In this review we will focus on unique aspects of Mycobacterium abscessus (MABS) which we feel earn it the designation of "shapeshifter of the mycobacterial world." We will review its emergence as a distinct species, the recognition and description of MABS subspecies which are only now being clearly defined in terms of pathogenicity, its ability to exist in different forms favoring a saprophytic lifestyle or one more suitable to invasion of mammalian hosts, as well as current challenges in terms of antimicrobial therapy and future directions for research. One can see in the various phases of MABS, a species transitioning from a free living saprophyte to a host-adapted pathogen.

Non-Tuberculous Mycobacteria multispecies biofilms in cystic fibrosis: development of an in vitro Mycobacterium abscessus and Pseudomonas aeruginosa dual species biofilm model

Lung disease in cystic fibrosis (CF) is characterized by the progressive colonization of the respiratory tract by different bacteria, which develop polymicrobial biofilms. In the past decades, there has been an increase in the number of CF patients infected with Non-Tuberculous Mycobacteria (NTM). Although Mycobacterium abscessus is the main NTM isolated globally, little is known about M. abscessus multispecies biofilm formation. In the present study we developed an in vitro model to study the phenotypic characteristics of biofilms formed by M. abscessus and Pseudomonas aeruginosa, a major pathogen in CF. For that purpose, dual species biofilms were grown on polycarbonate membranes with a fixed concentration of P. aeruginosa and different inoculums of M. abscessus. The biofilms were sampled at 24, 48, and 72 h and bacteria were quantified in specific media. The results revealed that the increasing initial concentration of M. abscessus in dual species biofilms had an effect on its population only at 24 and 48 h, whereas P. aeruginosa was not affected by the different concentrations used of M. abscessus. Time elapsed increased biofilm formation of both species, specially between 24 and 48 h. According to the results, the conditions to produce a mature dual species biofilm in which the relative species distribution remained stable were 72 h growth of the mixed microbial culture at a 1:1 ratio. A significant decrease in mycobacterial population in dual compared to single species biofilms was found, suggesting that P. aeruginosa has a negative influence on M. abscessus. Finally, in a proof of concept experiment, young and mature dual species biofilms were exposed to clarithromycin.