Mycobacterium Avium Complex Strains Research Articles

Minimum inhibitory concentrations of azithromycin in clinical isolates of Mycobacterium avium complex in Japan.

The latest guidelines include azithromycin as a preferred regimen for treating Mycobacterium avium complex (MAC) pulmonary disease. However, serially collected susceptibility data on clinical MAC isolates are limited, and no breakpoints have been determined. We investigated the minimum inhibitory concentrations (MICs) of azithromycin and clarithromycin for all MAC strains isolated in 2021 from a single center in Japan, excluding duplicates. The MICs were determined using a panel based on the microbroth dilution method, according to the latest Clinical and Laboratory Standards Institute recommendations. The MICs were determined for 318 MAC strains. Although there was a significant positive correlation between the MICs of azithromycin and clarithromycin, the MICs of azithromycin tended to be higher than those of clarithromycin. Among the cases in which the strains were isolated, 18 patients initiated treatment, including azithromycin treatment, after sample collection. Some patients infected with stains with relatively high azithromycin MICs achieved a microbiological cure with azithromycin-containing regimens. This study revealed a higher MIC distribution for azithromycin than clarithromycin, raising questions about the current practice of estimating azithromycin susceptibility based on the clarithromycin susceptibility test result. However, this was a single-center study that included only a limited number of cases treated with azithromycin. Therefore, further multicenter studies that include a greater number of cases treated with azithromycin are warranted to verify the distribution of azithromycin MICs and examine the correlation between azithromycin MICs and treatment effectiveness.IMPORTANCEThe macrolides serve as key drugs in the treatment of pulmonary Mycobacterium avium complex infection, and the administration of macrolide should be guided by susceptibility test results. Azithromycin is recommended as a preferred choice among macrolides, surpassing clarithromycin; however, drug susceptibility testing is often not conducted, and clarithromycin susceptibility is used as a surrogate. This study represents the first investigation into the minimum inhibitory concentration of azithromycin on a scale of several hundred clinical isolates, revealing an overall tendency for higher minimum inhibitory concentrations compared with clarithromycin. The results raise questions about the appropriateness of using clarithromycin susceptibility test outcomes for determining the administration of azithromycin. This study highlights the need for future discussions on the clinical breakpoints of azithromycin, based on large-scale clinical research correlating azithromycin susceptibility with treatment outcomes.

Biofilm prevention concentration of clarithromycin against clinically relevant species of nontuberculous mycobacteria.

Mycobacterium avium complex (MAC) and Mycobacterium abscessus are a group of nontuberculous mycobacteria (NTM) that have been described as human pathogens. Their ability to develop biofilms in tissues and medical devices is one of the most important pathogenicity factors, with important implications in diagnosis and treatment. Macrolides are usually considered one of the bases of this treatment. Here we have studied the biofilm prevention concentration (BPC) of 16 strains (n=16) with clarithromycin to avoid the biofilm development by these NTM. In this study, all M. abscessus strains have similar BPC, while MAC strains showed different values. For MAC the concentrations ranged between 1-16 mg/L, while for M. abscessus the concentration was 32 mg/L for all strains except one that was 64 mg/L. These results open the possibility of using macrolides for the prevention of biofilm development in patients with a risk of developing NTM disease.

Comparing minimum inhibitory concentrations of amikacin for pulmonary Mycobacterium avium complex disease: An analysis of culture media differences

Mycobacterium avium complex (MAC) is considered a paramount microbe, especially in East Asia, including Japan. The commonly used commercial Minimum Inhibitory Concentrations (MIC) assay using Middlebrook 7H9 (7H9) medium deviates from the latest Clinical and Laboratory Standards Institute (CLSI) guidelines. Alternatively, measurement with cation-adjusted Mueller-Hinton broth (CAMHB) that conforms to CLSI standards is not yet widely available. Following the approval and commercialization of amikacin liposome inhalation suspension (ALIS) in 2021, a more precise evaluation of amikacin (AMK) susceptibility in MAC is necessary for treatment decisions. In the present study, 33 sputum samples were extracted from 27 patients, and MICs of AMK were compared between the frequently used 7H9 and the recommended CAMHB of the isolated MAC strains. The history of exposure to aminoglycosides for each sample was also added as clinical information. The findings indicated that there was only an 18% concordance rate in MIC between the two media, with 19 samples (58%) indicating lower MICs in 7H9 relative to CAMHB. The 17 samples had a history of exposure to aminoglycosides for periods ranging from 1.5 to 28 months. Specifically, 10 samples were exposed to amikacin by inhalation and intravenous injection, and the remaining seven samples had a history of ALIS inhalation. Samples with a prior utilization of aminoglycosides were significantly predisposed to developing resistance to ALIS compared to those without such a history (P = 0.046). Physicians are encouraged to scrutinize the findings of susceptibility testing utilizing CLSI-endorsed MIC assay using CAMHB medium to ascertain the optimal therapeutic approach.

In vitro and intracellular activities of novel thiopeptide derivatives against macrolide-susceptible and macrolide-resistant Mycobacterium avium complex.

Unsatisfactory outcomes following long-term multidrug treatment in patients with Mycobacterium avium complex (MAC) pulmonary disease have urged us to develop novel antibiotics. Thiopeptides, a class of peptide antibiotics derived from natural products, have potential as drug candidates that target bacterial ribosomes, but drug development has been hampered due to their extremely poor solubility. Here, we evaluated three new compounds (AJ-037, AJ-039, and AJ-206) derived from the thiopeptide micrococcin P2 with enhanced aqueous solubility; the derivatives were generated based on structure-activity relationship analysis. We conducted in vitro drug susceptibility and intracellular antimycobacterial activity testing of the three thiopeptide derivatives against various MAC strains, including macrolide-resistant MAC clinical isolates. These compounds showed low MICs against MAC, similar to that of clarithromycin (CLR). In particular, two compounds, AJ-037 and AJ-206, had intracellular antimycobacterial activities, along with synergistic effects with CLR, and inhibited the growth of MAC inside macrophages. Moreover, these two compounds showed in vitro and intracellular anti-MAC activities against macrolide-resistant MAC strains without showing cross-resistance with CLR. Taken together, the results of the current study suggest that AJ-037 and AJ-206 can be promising anti-MAC agents for the treatment of MAC infection, including for macrolide-resistant MAC strains. IMPORTANCE Novel antibiotics for the treatment of MAC infection are urgently needed because the treatment outcomes using the standard regimen for Mycobacterium avium complex (MAC) pulmonary disease remain unsatisfactory. Here, we evaluated three novel thiopeptide derivatives (AJ-037, AJ-039, and AJ-206) derived from the thiopeptide micrococcin P2, and they were confirmed to be effective against macrolide-susceptible and macrolide-resistant MAC. Our thiopeptide derivatives have enhanced aqueous solubility through structural modifications of poorly soluble thiopeptides. The thiopeptide derivatives showed minimal inhibitory concentrations against MAC that were comparable to clarithromycin (CLR). Notably, two compounds, AJ-037 and AJ-206, exhibited intracellular antimycobacterial activities and acted synergistically with CLR to hinder the growth of MAC within macrophages. Additionally, these compounds demonstrated in vitro and intracellular anti-MAC activities against macrolide-resistant MAC strains without showing any cross-resistance with CLR. We believe that AJ-037 and AJ-206 can be promising anti-MAC agents for the treatment of MAC infections, including macrolide-resistant MAC strains.

A Rapid Screening Assay for Clarithromycin-Resistant Mycobacterium avium Complex Using Melting Curve Analysis with Nonfluorescent Labeled Probes.

Mycobacterium avium complex (MAC) thrives in various environments and mainly causes lung disease in humans. Because macrolide antibiotics such as clarithromycin or azithromycin are key drugs for MAC lung disease, the emergence of macrolide-resistant strains prevents the treatment of MAC. More than 95% of macrolide-resistant MAC strains are reported to have a point mutation in 23S rRNA domain V. This study successfully developed a melting curve assay using nonfluorescent labeled probes to detect the MAC mutation at positions 2058 to 2059 of the 23S rRNA gene (AA genotype, clarithromycin susceptible; TA, GA, AG, CA, AC, and AT genotypes, clarithromycin resistant). In the AA-specific probe assay, the melting peak of the DNA fragment of the AA genotype was higher than that of DNA fragments of other genotypes. Melting temperature (Tm) values of the AA genotype and the other genotypes were about 80°C and 77°C, respectively. DNA fragments of each genotype were identified correctly in six other genotype-specific probes (TA, GA, AG, CA, AC, and AT) assays. Using genomic DNA from six genotype strains of M. avium and four genotype strains of M. intracellulare, we confirmed that all genomic DNAs could be correctly identified as individual genotypes according to the highest Tm values among the same probe assays. These results indicate that this melting curve-based assay is able to determine MAC genotypes at positions 2058 to 2059 of the 23S rRNA gene. This simple method could contribute to the rapid detection of clarithromycin-resistant MAC strains and help to provide accurate drug therapy for MAC lung disease. IMPORTANCE Since macrolide antibiotics such as clarithromycin or azithromycin are key drugs in multidrug therapy for Mycobacterium avium complex (MAC) lung diseases, the rapid detection of macrolide-resistant MAC strains has important implications for the treatment of MAC. Previous studies have reported a correlation between drug susceptibility testing and the mutation of macrolide resistance genes. In this study, we developed a novel melting curve-based assay using nonfluorescent labeled probes to identify both clarithromycin-resistant M. avium and M. intracellulare with mutations in the 23S rRNA gene, which is the clarithromycin or azithromycin resistance gene. This assay contributed to not only the detection of MAC mutations but also the determination of all genotypes at positions 2058 to 2059 of the 23S rRNA gene. Furthermore, because nonfluorescent labeled probes are used, this assay is more easily and more immediately available than other methods.

1712. In Vitro Activity of Epetraborole, a Novel Bacterial Leucyl-tRNA Synthetase Inhibitor, in Drug Combinations Against Nontuberculous Mycobacteria Including Resistance Frequency and MIC Characterization of Mycobacterium avium ATCC 700898 Epetraborole-resistant Mutants

Abstract Background Epetraborole (EBO) is a boron-containing, oral inhibitor of bacterial leucyl-tRNA synthetase, an essential enzyme in protein synthesis; EBO demonstrates potent activity against nontuberculous mycobacteria (NTM). The standard of care therapy for Mycobacterium avium complex (MAC) lung disease consists of a combination of a macrolide, ethambutol (EMB) and a rifamycin. A total of 5 strains of MAC, M. abscessus ATCC 19977 and M. peregrinum ATCC 700686 were tested in checkerboard assays to evaluate the effects of combining EBO with other agents. The spontaneous resistance frequency (RF) was determined for EBO singly and in combination against M. avium ATCC 700898. Methods The effects of combining EBO with clarithromycin (CLR), rifabutin (RBT), EMB, amikacin (AMK) or bedaquiline (BDQ) were evaluated in 7 strains of NTM. Synergy, additive effects, indifference or antagonism was characterized in the checkerboard assay using EUCAST criteria. The RF of M. avium ATCC 700898 at 2x, 4x and 8x the MIC (8 mg/L) of EBO was determined, as was the RF of EBO combined with CLR, RBT, AMK or EMB. MICs of selected EBO mutants were determined against AMK, BDQ, CLR, RBT, EMB, and clofazimine (CFZ) and the mutants were further characterized. Results The RF of EBO ranged from 1.58x10-7 to 8.48x10-9 when selected on 2 - 8x agar MIC. The MIC for EBO increased 32- > 256-fold for the resistant mutants; however, the MICs for the other drugs tested against EBO-resistant strains did not change significantly. The activity of EBO was not antagonized, and was mainly indifferent to the addition of CLR, RBT, AMK, or BDQ for all the NTM strains tested. Synergy with EMB was observed with 2 strains and additivity with 2 additional strains of MAC. The addition of EMB (24 mg/L), CLR (32 mg/L), RFB (2 mg/L) or AMK (128 mg/L) to agar plates containing 2x MIC of EBO lowered the RF to at least < 2.13x10-10 (Table 1). Table 1.In Vitro Resistance Frequency for the Components of SOC with and without EBO in Mycobacterium avium ATCC 700898 Conclusion In the checkerboard studies, no evidence of antagonism was observed with any strain or EBO combination; interactions were largely indifferent. EBO combined with EMB in MAC resulted in synergy or additive effects in the checkerboard assay. The addition of EMB, CLR, RFB or AMK to EBO led to a > 700-fold reduction in RF. Activity of other drugs was not impacted by EBO resistance suggesting that cross-resistance did not occur. Disclosures Michelle S. DeStefano, n/a, AN2 Therapeutics: Grant/Research Support Carolyn M. Shoen, PhD, AN2 Therapeutics: Grant/Research Support MRK Alley, PhD, ABBOTT LABS: Stocks/Bonds|ABBVIE: Stocks/Bonds|AN2 Therapeutics: Author on epetraborole patent|AN2 Therapeutics: Salary|AN2 Therapeutics: Ownership Interest|AVANOS MED INC: Stocks/Bonds|NABRIVA THERAPEUTICS PLC: Stocks/Bonds|NOVARTIS AG: Stocks/Bonds Michael H. Cynamon, MD, AN2: Grant/Research Support|AN2: Grant/Research Support.

Antimicrobial susceptibility and minimum inhibitory concentration distribution of common clinically relevant non-tuberculous mycobacterial isolates from the respiratory tract

Objective: To determine the minimum inhibitory concentration (MIC) distribution of antibacterial drugs and the susceptibility of non-tuberculous mycobacterial (NTM) isolates to provide a reference basis for the clinical selection of an effective starting regimen. Methods: The common clinical isolates of NTM in the respiratory tract, which met the standards of the American Thoracic Society for NTM lung disease, were collected. The MICs of 81 isolates were determined using the microbroth dilution method (Thermo Fisher Scientific, USA), as recommended by the Clinical and Laboratory Standards Institute, USA. Results: Included were 43 Mycobacterium avium complex (MAC) strains, 24 M. abscessus complex (MAB) strains, and 14 M. kansasii strains. The sensitivity rates of MAC to clarithromycin and amikacin were 81.4% and 79.1%, respectively, while the sensitivity rates to linezolid and moxifloxacin were only 20.9% and 9.3%; the MIC of rifabutin was the lowest (MIC50% was just 2 μg/mL). After incubation for 3–5 days, the sensitivity rate of MAB to clarithromycin was 87.5%; this decreased to 50% after 14 days’ incubation. Most of them were susceptible to amikacin (91.6%), and most were resistant to moxifloxacin (95.8%), ciprofloxacin (95.8%), imipenem (95.8%), amoxicillin/clavulanate (95.8%), tobramycin (79.1%), doxycycline (95.8%) and trimethoprim/sulfamethoxazole (95.8%). intermediate (83.3%) and resistant (16.7%) to cefoxitin. The susceptibility to linezolid was only 33.3%. The sensitivity and resistance breakpoints of tigecycline were set to ≤0.5 and ≥8 μg/mL, respectively, and the sensitivity and resistance rates were 50% and 0%, respectively. M. kansasii was susceptible to clarithromycin, amikacin, linezolid, moxifloxacin, rifampicin and rifabutin (100%). Discussion: In Wenzhou, clarithromycin, amikacin and rifabutin have good antibacterial activity against MAC, while linezolid and moxifloxacin have high resistance. Amikacin and tigecycline have strong antibacterial activity against MAB, while most other antibacterial drugs are resistant to varying degrees. Most antibacterial drugs are susceptible to M. kansasii and have good antibacterial activity. Conclusion: The identification of NTM species and the detection of their MICs have certain guiding values for the treatment of NTM lung disease. Key Message The three most common respiratory non-tuberculous mycobacterial (NTM) isolates with clinical significance in the Wenzhou area were tested for drug susceptibility. The broth microdilution method was used to determine the minimum inhibitory concentration distribution of antibacterial drugs and the susceptibility of NTM isolates to provide a reference basis for the clinical selection of an effective starting regimen.

Comparative study of in vitro activity of tedizolid and linezolid against Mycobacterium avium complex.

ObjectivesThe aim of this study is to compare the in vitro activity and minimal inhibitory concentration (MIC) distributions of tedizolid and linezolid against Mycobacterium avium complex (MAC) strains using a reference broth microdilution assay and a macrodilution assay with the Bactec-MGIT-960. MethodsA total of 37 clinical isolates of MAC were included in the study. Reference broth microdilution was performed according to CLSI guidelines in a range of concentrations from 64 to 0.064 mg/L. Macrodilution was performed with the Bactec-MGIT-960 system. The cut-off points defined by CLSI for linezolid (resistant: > 16 mg/L, intermediate: 16 mg/L, susceptible: <16 mg/L) were used to define clinical categories of this drug. Essential agreement for both linezolid and tedizolid and categorical agreement for linezolid were defined following FDA criteria. ResultsThe MIC50 (16mg/L) and MIC90 (32mg/L) values for linezolid were identical with both methods. However, the MIC50 and MIC90 of tedizolid by microdilution (4 mg/L and 8 mg/L, respectively) were one twofold dilution higher than by macrodilution (2 mg/L and 4 mg/L, respectively). Ninety-four percent and 2.7% of the strains had MICs of tedizolid ≤4 mg/L and ≤ 0.5 mg/L, respectively, by the reference method. The linezolid macrodilution assay showed a categorical agreement of 40.5%, a minor error rate of 56.7% and a major error rate of 2.7% with respect to the reference method. ConclusionsTedizolid showed higher in vitro activity than linezolid against the tested MAC isolates. Macrodilution using the BD Bactec-MGIT-960 system is a practical approach to determine the susceptibility of MAC strains to tedizolid.

In vitro assessment of 17 antimicrobial agents against clinical Mycobacterium avium complex isolates

BackgroundRecently, Mycobacterium avium complex (MAC) infections have been increasing, especially in immunocompromised and older adults. The rapid increase has triggered a global health concern due to limited therapeutic strategies and adverse effects caused by long-term medication. To provide more evidence for the treatment of MAC, we studied the in vitro inhibitory activities of 17 antimicrobial agents against clinical MAC isolates.ResultsA total of 111 clinical MAC isolates were enrolled in the study and they were identified as M. intracellulare, M. avium, M. marseillense, M. colombiense, M. yongonense, and two isolates could not be identified at the species level. MAC strains had relatively low (0–21.6%) resistance to clarithromycin, amikacin, bedaquiline, rifabutin, streptomycin, and clofazimine, and the resistant rates to isoniazid, rifampin, linezolid, doxycycline, and ethionamide were very high (72.1–100%). In addition, M. avium had a significantly higher resistance rate than that of M. intracellulare for ethambutol (92.3% vs 40.7%, P < 0.001), amikacin (15.4% vs 1.2%, P = 0.049), and cycloserine (69.2% vs 25.9%, P = 0.004).ConclusionsOur results supported the current usage of macrolides, rifabutin, and aminoglycosides in the regimens for MAC infection, and also demonstrated the low resistance rate against new drugs, such as clofazimine, tedizolid, and bedaquiline, suggesting the possible implementation of these drugs in MAC treatment.

Omadacycline efficacy in the hollow fibre system model of pulmonary Mycobacterium avium complex and potency at clinically attainable doses.

ObjectivesThe standard of care (SOC) for the treatment of pulmonary Mycobacterium avium complex (MAC) disease (clarithromycin, rifabutin, and ethambutol) achieves sustained sputum conversion rates of only 54%. Thus, new treatments should be prioritized.MethodsWe identified the omadacycline MIC against one laboratory MAC strain and calculated drug half life in solution, which we compared with measured MAC doubling times. Next, we performed an omadacycline hollow fibre system model of intracellular MAC (HFS-MAC) exposure–effect study, as well as the three-drug SOC, using pharmacokinetics achieved in patient lung lesions. Data was analysed using bacterial kill slopes (γ-slopes) and inhibitory sigmoid Emax bacterial burden versus exposure analyses. Monte Carlo experiments (MCE) were used to identify the optimal omadacycline clinical dose.ResultsOmadacycline concentration declined in solution with a half-life of 27.7 h versus a MAC doubling time of 16.3 h, leading to artefactually high MICs. Exposures mediating 80% of maximal effect changed up to 8-fold depending on sampling day with bacterial burden versus exposure analyses, while γ-slope-based analyses gave a single robust estimate. The highest omadacycline monotherapy γ-slope was −0.114 (95% CI: −0.141 to −0.087) (r2 = 0.98) versus −0.114 (95% CI: −0.133 to −0.094) (r2 = 0.99) with the SOC. MCEs demonstrated that 450 mg of omadacycline given orally on the first 2 days followed by 300 mg daily would achieve the AUC0-24 target of 39.67 mg·h/L.ConclusionsOmadacycline may be a potential treatment option for pulmonary MAC, possibly as a back-bone treatment for a new MAC regimen and warrants future study in treatment of this disease.

Population Genomics and Inference of Mycobacterium avium Complex Clusters in Cystic Fibrosis Care Centers, United States.

Mycobacterium avium complex (MAC) species constitute most mycobacteria infections in persons with cystic fibrosis (CF) in the United States, but little is known about their genomic diversity or transmission. During 2016–2020, we performed whole-genome sequencing on 364 MAC isolates from 186 persons with CF from 42 cystic fibrosis care centers (CFCCs) across 23 states. We compared isolate genomes to identify instances of shared strains between persons with CF. Among persons with multiple isolates sequenced, 15/56 (27%) had >1 MAC strain type. Genomic comparisons revealed 18 clusters of highly similar isolates; 8 of these clusters had patients who shared CFCCs, which included 27/186 (15%) persons with CF. We provide genomic evidence of highly similar MAC strains shared among patients at the same CFCCs. Polyclonal infections and high genetic similarity between MAC isolates are consistent with multiple modes of acquisition for persons with CF to acquire MAC infections.

In vitro activity of bedaquiline against Mycobacterium avium complex.

Introduction. Nontuberculous mycobacteria (NTM) are widespread in the environment and can cause various diseases in humans, especially immunocompromised patients.Hypothesis. Treatment of diseases caused by NTM is a complicated issue, mainly due to the resistance of the pathogen to most antimicrobial agents. Bedaquiline (Bdq) is now widely used for the treatment of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB).Aim. The main goal of our study was to evaluate the activity of Bdq against Mycobacterium avium complex (MAC), the most common species among NTM.Methodology. A total of 166 MAC cultures (124 Mycobacterium avium and 42 Mycobacterium intracellulare) were studied. The minimum inhibitory concentrations (MICs) of Bdq for M. avium and M. intracellulare were obtained by twofold serial dilutions in the Middlebrook 7H9 medium. MIC ranges were determined and the MIC50, MIC90 and ECOFF values were obtained.Results. The MICs in respect of M. avium ranged from 0.003 to 1.0 µg ml-1; those for M. intracellulare ranged from 0.003 to 0.5 µg ml-1. The Bdq MIC50 and MIC90 values were found to be 0.015 and 0.12 µg ml-1 , respectively, for M. avium and 0.007 and 0.06 µg ml-1, respectively, for M. intracellulare. The tentative ECOFF values for M. avium and M. intracellulare were 0.12 and 0.06 µg ml-1, respectively.Conclusion. The main bedaquiline susceptibility parameters for MAC strains isolated in the Moscow region were determined.

Comparative Genomics of Mycobacterium avium Complex Reveals Signatures of Environment-Specific Adaptation and Community Acquisition.

ABSTRACTNontuberculous mycobacteria, including those in the Mycobacterium avium complex (MAC), constitute an increasingly urgent threat to global public health. Ubiquitous in soil and water worldwide, MAC members cause a diverse array of infections in humans and animals that are often multidrug resistant, intractable, and deadly. MAC lung disease is of particular concern and is now more prevalent than tuberculosis in many countries, including the United States. Although the clinical importance of these microorganisms continues to expand, our understanding of their genomic diversity is limited, hampering basic and translational studies alike. Here, we leveraged a unique collection of genomes to characterize MAC population structure, gene content, and within-host strain dynamics in unprecedented detail. We found that different MAC species encode distinct suites of biomedically relevant genes, including antibiotic resistance genes and virulence factors, which may influence their distinct clinical manifestations. We observed that M. avium isolates from different sources—human pulmonary infections, human disseminated infections, animals, and natural environments—are readily distinguished by their core and accessory genomes, by their patterns of horizontal gene transfer, and by numerous specific genes, including virulence factors. We identified highly similar MAC strains from distinct patients within and across two geographically distinct clinical cohorts, providing important insights into the reservoirs which seed community acquisition. We also discovered a novel MAC genomospecies in one of these cohorts. Collectively, our results provide key genomic context for these emerging pathogens and will facilitate future exploration of MAC ecology, evolution, and pathogenesis.IMPORTANCE Members of the Mycobacterium avium complex (MAC), a group of mycobacteria encompassing M. avium and its closest relatives, are omnipresent in natural environments and emerging pathogens of humans and animals. MAC infections are difficult to treat, sometimes fatal, and increasingly common. Here, we used comparative genomics to illuminate key aspects of MAC biology. We found that different MAC species and M. avium isolates from different sources encode distinct suites of clinically relevant genes, including those for virulence and antibiotic resistance. We identified highly similar MAC strains in patients from different states and decades, suggesting community acquisition from dispersed and stable reservoirs, and we discovered a novel MAC species. Our work provides valuable insight into the genomic features underlying these versatile pathogens.

Treatment of Mycobacterium avium–intracellulare complex lung disease in the real world: a retrospective big data analysis

The chemotherapeutic regimen recommended by guidelines to prevent the development of a drug-resistant strain of Mycobacterium avium complex (MAC) consists of a combination of clarithromycin, rifampicin, and ethambutol. In severe cases, it is desirable to use either kanamycin or streptomycin in addition to these three drugs. However, it is unclear whether treatment is administered in accordance with the guidelines in real-world clinical settings. This study aimed to determine the chemotherapy patterns among patients treated for MAC lung disease in medical facilities in Japan. We investigated treatment patterns regarding patients treated for MAC lung disease between 2007 and 2017, in relation to the latest Japanese guidelines for the treatment of MAC lung disease, using insurance claims data of 378 patients. The basic triple-agent regimen of clarithromycin, ethambutol, and rifampicin was received by 238 (63%) of the 378 patients. Of these, 115 (48.3%) received the regimen for the recommended period of > 1 year. Therefore, widely publicizing the need for application of standard treatment for at least 2 years is necessary, as is the need to develop methods to overcome adverse effects. Many patients with MAC lung disease do not complete a full course of treatment over the standard treatment period. Therefore, it is important to develop methods to overcome adverse effects or to develop an alternative treatment regimen for MAC lung disease.

Mycobacterium avium Infection in a C3HeB/FeJ Mouse Model.

Infections caused by Mycobacterium avium complex (MAC) species are increasing worldwide, resulting in a serious public health problem. Patients with MAC lung disease face an arduous journey of a prolonged multidrug regimen that is often poorly tolerated and associated with relatively poor outcome. Identification of new animal models that demonstrate a similar pulmonary pathology as humans infected with MAC has the potential to significantly advance our understanding of nontuberculosis mycobacteria (NTM) pathogenesis as well as provide a tractable model for screening candidate compounds for therapy. One new mouse model is the C3HeB/FeJ which is similar to MAC patients in that these mice can form foci of necrosis in granulomas. In this study, we evaluated the ability of C3HeB/FeJ mice exposure to an aerosol infection of a rough strain of MAC 2285 to produce a progressive infection resulting in small necrotic foci during granuloma formation. C3HeB/FeJ mice were infected with MAC and demonstrated a progressive lung infection resulting in an increase in bacterial burden peaking around day 40, developed micronecrosis in granulomas and was associated with increased influx of CD4+ Th1, Th17, and Treg lymphocytes into the lungs. However, during chronic infection around day 50, the bacterial burden plateaued and was associated with the reduced influx of CD4+ Th1, Th17 cells, and increased numbers of Treg lymphocytes and necrotic foci during granuloma formation. These results suggest the C3HeB/FeJ MAC infection mouse model will be an important model to evaluate immune pathogenesis and compound efficacy.

Genetic Variation/Evolution and Differential Host Responses Resulting from In-Patient Adaptation of Mycobacterium avium.

Members of the Mycobacterium avium complex (MAC) are characterized as nontuberculosis mycobacteria and are pathogenic mainly in immunocompromised individuals. MAC strains show a wide genetic variability, and there is growing evidence suggesting that genetic differences may contribute to a varied immune response that may impact the infection outcome. The current study aimed to characterize the genomic changes within M.avium isolates collected from single patients over time and test the host immune responses to these clinical isolates. Pulsed-field gel electrophoresis and whole-genome sequencing were performed on 40 MAC isolates isolated from 15 patients at the Department of Medical Microbiology at St. Olavs Hospital in Trondheim, Norway. Isolates from patients (patients 4, 9, and 13) for whom more than two isolates were available were selected for further analysis. These isolates exhibited extensive sequence variation in the form of single-nucleotide polymorphisms (SNPs), suggesting that M. avium accumulates mutations at higher rates during persistent infections than other mycobacteria. Infection of murine macrophages and mice with sequential isolates from patients showed a tendency toward increased persistence and the downregulation of inflammatory cytokines by host-adapted M. avium strains. The study revealed the rapid genetic evolution of M. avium in chronically infected patients, accompanied by changes in the virulence properties of the sequential mycobacterial isolates.

Mycobacterium avium complex pulmonary disease in multidrug-resistant tuberculosis-suspected patients in Mali

Background The incidence of nontuberculous mycobacteria is increasing, among them Mycobacterium avium complex (MAC) strains are the most frequently isolated. In countries endemic for tuberculosis, these infections pose a differential diagnosis challenge due to their clinical similarities. Patients and methods The main goal of this study was to describe the epidemiological, clinical aspects, and outcome of patients infected with MAC who met the American thoracic society (ATS) 2007 criteria for MTN disease’s definition. We conducted a 4-year retrospective evaluation from January 2009 to December 2012 at the Pneumophtisiology Department of the Point G University Teaching Hospital in Bamako. Results A total of 17 patients met the criteria for MAC disease, 16 men and one woman with a mean age of 50.4 years. All patients had at least two antituberculosis treatment courses without success. The signs and symptoms were a febrile alteration of physical condition in 41.7% (seven cases), chronic cough in 94.1% (16 cases), dyspnea in 68.7% (11 cases), and hemoptysis in 11.7% (two cases). The sputum smear was positive in 94.1% (16 cases) and the chest radiography showed constant cavitary images associated with nodular lesions in 52.9% (nine cases) or pleurisy in 11.7% (two cases). The evolution was marked by six deaths occurred within an average of 10 months and 10 were loss to follow-up. Conclusion The occurrence of MAC pulmonary disease poses diagnosis and treatment problems with less favorable outcome. Availability of early diagnosis with sputum culture will allow an accurate treatment regimen, which will improve patient outcomes.

Lady Windermere syndrome in Castile and León

IntroductionLady Windermere syndrome (LWS) is a pulmonary disease caused by Mycobacterium avium complex (MAC). The objective of this study is to ascertain its frequency and characteristics in the northern area of the autonomous community of Castile and León. MethodsA retrospective study of patients with MAC isolates in respiratory samples from five public hospitals in the autonomous community over a 6-year period, following the ATS/IDSA criteria. The MAC strains were identified by GenoType Mycobacterium reverse hybridisation probes or PCR-RFLP analysis of the hsp65 gene. ResultsOf 183 cases of MAC identified, only five women (2.7%) aged 68.8±10.7 years met LWS criteria. In three cases, MAC was isolated jointly and intermittently with other pathogens. Only one patient was treated according to ATS/IDSA criteria. DiscussionLWS remains underestimated, with affected patients representing a significant burden on healthcare resources over long periods of time. As a result, greater microbiological and therapeutic knowledge of the syndrome is needed.

Síndrome de Lady Windermere en Castilla y León

IntroductionLady Windermere syndrome (LWS) is a pulmonary disease caused by Mycobacterium avium complex (MAC). The objective of this study is to ascertain its frequency and characteristics in the northern area of the autonomous community of Castile and León. MethodsA retrospective study of patients with MAC isolates in respiratory samples from five public hospitals in the autonomous community over a six-year period, following the ATS/IDSA criteria. The MAC strains were identified by GenoType Mycobacterium reverse hybridisation probes or PCR-RFLP analysis of the hsp65 gene. ResultsOf 183 cases of MAC identified, only five women (2.7%) aged 68.8±10.7years met LWS criteria. In three cases, MAC was isolated jointly and intermittently with other pathogens. Only one patient was treated according to ATS/IDSA criteria. DiscussionLWS remains underestimated, with affected patients representing a significant burden on healthcare resources over long periods of time. As a result, greater microbiological and therapeutic knowledge of the syndrome is needed.

Relapse versus Reinfection of Mycobacterium avium Complex Pulmonary Disease. Patient Characteristics and Macrolide Susceptibility.

Clinical recurrence of Mycobacterium avium complex (MAC) pulmonary disease occurs in 10 to 40% of patients treated for this disease process. Episodes of clinical recurrence may represent true relapse from the same MAC strain or reinfection with a new strain. The purpose of this study was to investigate the clinical implications of separating patients into these two groups. This retrospective study evaluated patients with a clinical recurrence of MAC pulmonary disease at our institution from 2000 to 2012. Isolates were genotyped using pulsed-field gel electrophoresis to differentiate relapse versus reinfection. Change in macrolide susceptibility was also analyzed. In our cohort, 25% of patients suffered a clinical recurrence. Of the 46 included patients, 25 (54%) suffered a true relapse and 21 (46%) had a reinfection. Median time between completion of therapy and clinical recurrence was significantly lower in the relapse group compared with the reinfection group (210 d vs. 671 d; P = 0.004). The measured convalescent macrolide minimum inhibitory concentrations were significantly more likely to increase in the relapse group compared with the reinfection group (80 vs. 33%; P = 0.002). No differences in clinical outcomes were observed between the two groups at conclusion of the study. Our findings suggest that patients with true relapse of MAC pulmonary disease present earlier than those with reinfection. Routine use of pulsed-field gel electrophoresis in the management of clinical recurrences may be beneficial, as those suffering a relapse are more likely to have increasing macrolide minimum inhibitory concentrations than those with reinfection.