Mycobacterium Avium Complex Disease Research Articles

Rifabutin for infusion (BV100) for the treatment of severe carbapenem-resistant Acinetobacter baumannii infections

Rifamycin antibiotics were discovered during the 1950s, and their main representative, rifampicin, remains a cornerstone treatment for TB. The clinical use of rifamycin is restricted to mycobacteria and Gram-positive infections because of its poor ability to penetrate the Gram-negative outer membrane. Rifabutin, a rifamycin antibiotic approved for the prevention of Mycobacterium avium complex disease, makes an exception to this rule by hijacking the iron uptake system of Acinetobacter baumannii, resulting in potent activity against this important Gram-negative pathogen. Here, we describe recent findings on the specific activity of rifabutin and provide evidence of the need for the development of an intravenous formulation of rifabutin (BV100) for the treatment of difficult-to-treat carbapenem-resistant A.baumannii infections.

MYCOBACTERIUM AVIUM COMPLEX ASSOCIATED IMMUNE RECONSTITUTION INFLAMMATORY SYNDROME IN HIV- INFECTED PATIENT

The incidence of Mycobacterium avium Complex (MAC) Disease in HIV-infected individuals has significantly decreased in recent years due to the introduction of Highly Active Antiretroviral Therapy (HAART) and the initiation of Clarithromycin prophylaxis. We present the case of a patient with advanced AIDS, with generalized lymphadenopathy and digestive symptoms, diagnosed with disseminated MAC, a diagnosis which was based on the results obtained from axillary lymph node and intestinal biopsies. Considering the time of the MAC diagnosis in relation to the recent introduction of antiretroviral (ARV) therapy, we considered immune reconstitution inflammatory syndrome (IRIS) with good evolution under azithromycin, ethambutol and moxifloxacin treatment.

The Mycobacterium avium complex - an underestimated threat to humans and animals.

The Mycobacterium avium complex (MAC) is a group of acid-resistant bacteria within the Mycobacteriaceae. Their cell walls have a specific structure impervious to many disinfectants. Mycobacteria are widespread in the environment and can also be found in food. This aim of the article is to review the current state of knowledge about the sources of infection, symptoms and treatment of MAC diseases in humans and animals, and summarizes the available methods for identifying the bacteria. It pays a special attention to the zoonotic potential of MAC bacteria and possible routes of transmission between humans and animals, including possible food-borne routes. MAC bacterial infections occur both in immunocompetent people and those with functional predispositions and compromised immunity, particularly during HIV infection or immunosuppressive treatment. The incidence of MAC infections in humans is growing, with the most common form of infection being pulmonary disease (MTC-PD); however, there are conflicting reports on the role of Mycobacterium avium paratuberculosis (MAP) in the development of Crohn's disease. MAC bacteria can also attack livestock, household pets, and wild animals. Unfortunately, treatment is lengthy and often fails due to microbiological relapse; there is also increasing evidence of MAC bacteria are developing multi-drug resistance. Although new antibiotics are being created to inhibit the growth and division of Mycobacterium avium, there is clearly a need for further research into the virulence factors associated with MAC bacteria. Further studies should also examine the role of MAP in the etiopathogenesis of Crohn's disease.

Interferon-Gamma Release Assays Differentiate between Mycobacterium avium Complex and Tuberculous Lymphadenitis in Children

To assess the performance of interferon-gamma release assays (IGRAs) in the differential diagnosis between Mycobacterium avium complex (MAC) and tuberculosis (TB) in children affected with subacute/chronic submandibular/cervical lymphadenitis. Multicenter observational study comparing children with microbiologically confirmed MAC lymphadenitis from the European NontuberculouS MycoBacterial Lymphadenitis in childrEn study with children with TB lymphadenitis from the Spanish Network for the Study of Pediatric TB database. Overall, 78 patients with MAC and 34 with TB lymphadenitis were included. Among MAC cases, 44 out of 74 (59.5%) had positive tuberculin skin test (TST) results at the 5-mm cut-off, compared with 32 out of 33 (97%) TB cases (P<.001); at the 10-mm cut-off TST results were positive in 23 out of 74 (31.1%) vs 26 out of 31 (83.9%), respectively (P<.001). IGRA results were positive in only 1 out of 32 (3.1%) patients with MAC who had undergone IGRA testing, compared with 21 out of 23 (91.3%) TB cases (P<.001). Agreement between TST and IGRA results was poor in MAC (23.3%; κ=0.017), but good in TB cases (95.6%; κ=0.646). IGRAs had a specificity of 96.9% (95% CI 84.3%-99.8%), positive predictive value of 95.4% (95% CI 78.2%-99.8%), and negative predictive value of 93.9% (95% CI 80.4%-98.9%) for TB lymphadenitis. In contrast to TST, IGRAs have high specificity, negative predictive value, and positive predictive value for TB lymphadenitis in children with subacute/chronic lymphadenopathy, and consequently can help to discriminate between TB and MAC disease. Therefore, IGRAs are useful tools in the diagnostic work-up of children with lymphadenopathy, particularly when culture and polymerase chain reaction results are negative.

R-CHOP Chemotherapy for Disseminated Mycobacterium avium Complex Disease due to Anti-Interferon-Gamma Autoantibodies: A Case Report.

A 77-year-old Japanese man with disseminated Mycobacterium avium complex (MAC) disease due to anti-interferon-gamma autoantibodies received rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP) chemotherapy because of non-Hodgkin lymphoma complication. The hepatobiliary nodules due to MAC resolved with R-CHOP and multidrug antimycobacterial treatment. R-CHOP could serve as an alternative adjunctive therapy for patients with anti-interferon-gamma autoantibodies.

The Association of Long-term Macrolide Therapy and Nontuberculous Mycobacterial Culture Positivity in Patients With Bronchiectasis

The Association of Long-term Macrolide Therapy and Nontuberculous Mycobacterial Culture Positivity in Patients With Bronchiectasis

Genome-wide association study in patients with pulmonary Mycobacterium avium complex disease.

Nontuberculous mycobacteria (NTM) are environmental mycobacteria that can cause a chronic progressive lung disease. Although epidemiological data indicate potential genetic predisposition, its nature remains unclear. We aimed to identify host susceptibility loci for Mycobacterium avium complex (MAC), the most common NTM pathogen. This genome-wide association study (GWAS) was conducted in Japanese patients with pulmonary MAC and healthy controls, followed by genotyping of candidate single-nucleotide polymorphisms (SNPs) in another Japanese cohort. For verification by Korean and European ancestry, we performed SNP genotyping. The GWAS discovery set included 475 pulmonary MAC cases and 417 controls. Both GWAS and replication analysis of 591 pulmonary MAC cases and 718 controls revealed the strongest association with chromosome 16p21, particularly with rs109592 (p=1.64×10-13, OR 0.54), which is in an intronic region of the calcineurin-like EF-hand protein 2 (CHP2). Expression quantitative trait loci analysis demonstrated an association with lung CHP2 expression. CHP2 was expressed in the lung tissue in pulmonary MAC disease. This SNP was associated with the nodular bronchiectasis subtype. Additionally, this SNP was significantly associated with the disease in patients of Korean (p=2.18×10-12, OR 0.54) and European (p=5.12×10-03, OR 0.63) ancestry. We identified rs109592 in the CHP2 locus as a susceptibility marker for pulmonary MAC disease.

Pulmonary mycobacterium avium complex disease complicated by cancer: an 11-year survey at a single-center.

Objective: Pulmonary mycobacterium avium complex (MAC) disease is increasing significantly worldwide. Several studies have investigated the clinical features of pulmonary MAC disease in the setting of cancer. Here, we aimed to clarify the clinical characteristics of patients with cancer with recent onset of pulmonary MAC disease and the effect of cancer on the onset of this disease.Patients and Methods: Of the 323 consecutive Japanese patients newly diagnosed with pulmonary MAC disease at Jichi Medical University Hospital between and 2006–2017, we retrospectively reviewed 79 consecutive patients with cancer.Results: Seventeen patients had lung cancer (21.0%), while 62 had non-lung cancer. Of the 17 patients with lung cancer, 16 had adenocarcinoma of which 10 had stage I to III disease; 8 of the 10 patients had not received chemotherapy. Sixteen patients with lung cancer had a MAC infection in the ipsilateral lung. Notably, 9 of the 11 lung cancer patients who did not undergo surgery had a MAC infection in the affected lobe. Of the 39 patients with the most common types of non-lung cancer (14 had gastric cancer, 13 had colorectal cancer, and 12 had breast cancer), 22 had stage I to III disease, and 18 of these 22 had not received chemotherapy.Conclusion: Lung cancer may act as a local factor contributing to the onset of pulmonary MAC disease in the ipsilateral lung. However, the underlying mechanism by which a history of cancer might affect the onset of pulmonary MAC disease remains unclear. Further investigation into this mechanism is needed.

1654. Evaluation of a rapid detection method of clarithromycin resistance genes in Mycobacterium avium using the Amplification Refractory Mutation System-Loop-Mediated Isothermal Amplification method

BackgroundClarithromycin (CLR) is the key drug in multidrug therapy for Mycobacterium avium complex (MAC) diseases and the only drug for which drug susceptibility is correlated with a clinical response in these diseases. In the case of CLR-resistant MAC, a point mutation is present at either position 2058 or 2059 of the peptidyl transferase active center in the domain V region of 23S rRNA at the macrolide binding site. Using conventional investigation, we clarified the correlation between drug susceptibility testing and mutation of drug resistance genes. In this study, we adapted a rapid detection method using the amplification refractory mutation system (ARMS)-loop-mediated isothermal amplification (LAMP) to identify a mutation in the 23S rRNA gene in M. avium isolates (Figure 1). Furthermore, we evaluated the usefulness as point-of-care testing (POCT) technology using clinical isolates.Figure 1. The designs of CLR resistance A2058G mutant-type mismatch primers used for the ARMS-LAMP assay. a) A strand-displacing DNA polymerase extends the DNA from FIP while separating from the DNA chain. The primer F3 binds to its complementary region on the DNA to displace the newly synthesized DNA. An analogous reaction is performed by BIP and B3. α (α = A, wild type; G, A2058G) and β (β = A, wild type; C, A2058G) are indicated by the point mutation at position 2058 of the 23S rRNA gene. The bold area indicates the mismatched base C (cytosine). b) The synthesized DNA self-anneals because of the complementary region at both ends and forms ‘dumbbell’ structures. c) After repeated rounds, a complementary region on the same chain is amplified. MethodsPrimers for ARMS-LAMP were designed using PrimerExplorerV5 software based on the nucleotide sequence data for 23S rRNA in M. avium strain 104 (Figure 2). Using the minimum inhibitory concentration of CLR, drug susceptibility was determined for 18 clinical M. avium isolates. Of these, eight CLR-susceptible and 10 CLR-resistant strains were analyzed by sequencing the 23S rRNA gene and ARMS-LAMP.Figure 2. Alignment of the nucleotide sequences including the domain V region of 23S rRNA at the macrolide binding site. The constructed LAMP primer sets are shown in solid boxes (forward primers, F1-3) and dashed boxes (backward primers, B1-3). The bold area indicates the point mutation at position 2058 or 2059 of the 23S rRNA gene. ResultsSequence analysis revealed that all eight CLR-sensitive strains tested were wild type, whereas all 10 CLR-resistant strains were mutants. Using ARMS-LAMP, no amplification with the mutant-type mismatch primer sets (MTPS) was observed in the eight wild-type strains, but amplification was observed with MTPS in the 10 mutant strains (Table 1).Table 1. MICs of CLR and results of ARMS–LAMP using Mycobacterium avium isolates. ConclusionThe developed rapid detection method for the CLR resistance gene using ARMS-LAMP can determine drug resistance in a few hours without the need for special equipment. ARMS-LAMP may be a new clinically beneficial POCT technology for examination that is novel and extremely practical.Disclosures All Authors: No reported disclosures

Predictors of radiological aggravations of pulmonary MAC disease.

The number of patients with pulmonary Mycobacterium avium complex (MAC) disease is increasing worldwide, especially among middle-aged women and never-smokers. However, little is known about the factors causing exacerbations of pulmonary MAC disease in untreated patients. The aim of the present study was to identify the predictors of radiological aggravations of pulmonary MAC disease. From April 2011 to December 2018, 238 MAC patients at our institute were newly diagnosed with pulmonary MAC disease according to the 2007 American Thoracic Society/Infectious Disease Society guideline. Their medical records were examined retrospectively for their clinical findings. The radiological findings at the time of the diagnosis and 1 year later were evaluated. To identify the predictors of radiological aggravation, multivariable analysis was performed with the data of 167 treatment-naïve patients. Female, never-smoker, and nodular/bronchiectatic (NB) type were predominant in patients with pulmonary MAC disease. Univariate analysis of data from treatment-naïve subjects showed that no lung diseases other than MAC, extensive radiological findings, and a positive acid-fast bacilli (AFB) smear were significantly associated with radiological aggravations. On multivariate analysis, the radiological factor (larger affected area) and absence of other lung disease were significantly associated with radiological aggravations. In particular, the presence of abnormal shadows in more than 3 lobes was significantly associated with radiological aggravations. In this study, the presence of extensive radiological findings and the absence of lung diseases other than MAC were predictors of radiological aggravations of treatment-naïve pulmonary MAC disease. In particular, the presence of abnormal shadows in more than 3 lobes was significantly associated with radiological aggravations.

Efficacy and safety of fluoroquinolone-containing regimens in treating pulmonary Mycobacterium avium complex disease: A propensity score analysis.

BackgroundAlthough combination therapy using clarithromycin, rifampicin, and ethambutol is recommended for patients with pulmonary Mycobacterium avium complex (MAC) disease, some patients do not tolerate it because of adverse effects or underlying diseases. The efficacy and safety of fluoroquinolone-containing combination regimens as an alternative remain uncertain. This study aimed to compare the efficacy and safety of fluoroquinolone-containing regimens with those of the standard regimens for treating pulmonary MAC disease.MethodsWe retrospectively included consecutive MAC patients who were treated in our hospital between January 2011 and May 2019. Patients treated with fluoroquinolone-containing regimens who had relapsed after treatment with standard regimens were excluded. A propensity score analysis was conducted to reduce selection bias, and the proportions of clinical improvement, defined by chest imaging findings and sputum conversion, were compared between the fluoroquinolone-containing regimen and standard regimen groups.ResultsWe analyzed 28 patients who received fluoroquinolone-containing regimens and 46 who received the standard regimen. Fluoroquinolone-containing regimens were more likely selected for patients with cavitary lesions, diabetes mellitus, culture negativity, a low daily physical activity level, a decreased lymphocyte count and an increased CRP level. The propensity score was calculated using these variables (C-statistic of the area under the receiver operating characteristic curve of the propensity score: 0.807, p < 0.0001). The fluoroquinolone-containing regimens were significantly inferior to the standard regimen in clinical improvements (p = 0.002, Log-rank test) in the univariate analysis, but the significance was lost after adjusting for the propensity score (HR 0.553, 95% CI 0.285–1.074, p = 0.080). Six (21%) patients in the fluoroquinolone-containing regimen group and ten (22%) patients in the standard regimen group experienced low-grade adverse effects.ConclusionsThere was no significant difference in clinical improvement between these regimens after propensity score adjustment. A large-scale prospective study is required to validate these results.

Serum oxidative stress in patients with pulmonary Mycobacterium avium complex disease

BackgroundThe mechanism of progressive airway destruction in incurable chronic infection of the lung – termed pulmonary Mycobacterium avium complex (pMAC) disease – is currently unknown. The involvement of oxidative stress in a variety of progressive chronic respiratory diseases has been previously reported. It has been hypothesized that oxidative stress may be involved in the progression of airway destruction in pMAC disease. Patients and methodsThe study included 28 untreated patients with pMAC disease. The level of serum oxidative stress was quantitatively evaluated through the diacron reactive oxygen metabolites (d-ROMs) test, which indirectly measures the level of hydroperoxide in the serum. In addition, patients were divided into three groups based on the severity shown in the computed tomographic image. ResultsThe level of serum oxidative stress exceeded the normal range (250–300 U.Carr [Carratelli Units]) in all patients with pMAC disease (mean: 495.5 ± 102.6 U.Carr; minimum–maximum: 340–734 U.Carr). The level of serum oxidative stress in patients with severe disease was significantly higher compared with that observed in patients with mild disease (434.6 ± 30.2 vs. 583.4 ± 95.1, respectively, p = 0.009). ConclusionsIn patients with pMAC disease, an elevation was observed in the level of serum oxidative stress. This increase in oxidative stress was more pronounced in patients with severe disease.

1375. Laboratory Abnormalities Among Patients with Pulmonary Mycobacterium avium Complex Infections

BackgroundLimited data are available regarding laboratory abnormalities in patients with pulmonary Mycobacterium avium complex (MAC) disease.MethodsWe included patients without cystic fibrosis who had pulmonary MAC and met ATS/IDSA disease criteria from the Northwest NTM Biobank with a complete blood count (CBC) 6 months prior and up to 30 days after study enrollment. The biobank is a cohort of patients with Nontuberculous mycobacterium (NTM) infections identified through statewide laboratory surveillance and OHSU regional referral NTM clinic; a complete clinical history is collected by chart review at enrollment. We evaluated the proportion of pulmonary MAC patients with abnormal laboratory tests. We examined differences using a chi-square test between patients who were antimycobacterial treatment naïve, on therapy at enrollment or previously treated, in addition to cavitary and non-cavitary disease and those who also had previous sputum isolation of additional organisms (co-isolation).Results147 patients had CBCs available; 112 (76.2%) were female with a median age of 69 years (22–88 years). 64 (43.5%) were antimycobacterial treatment naïve, 65 (44.2%) were on therapy at enrollment and 18 (12.2%) were previously treated. Lymphocyte count was below normal in 105 (73.4%) patients; 70 (49.3%) had lymphocyte counts below 1500 cells/mL and 27 (18.9%) were lymphopenic. Elevated monocyte percent was seen in 54 (37.2%) patients. Lymphopenia was more common in those on therapy, P = 0.01. There were no predominant laboratory abnormalities in 108 patients with metabolic panels. 34 patients had a c-reactive protein (CRP) collected, which was elevated, after age and gender correction, in 31 patients (91.2%). There was no significant difference between treatment groups. Eleven patients had cavitary disease with no differences in laboratory values compared with those with non-cavitary disease. Patients with co-isolation were more likely to be anemic (P = 0.03), have thrombocytosis (P = 0.04) and were less likely to have a monocytosis (P = 0.03).ConclusionA large proportion of patients with pulmonary MAC disease have low lymphocyte counts, elevated monocyte percent and CRP. Further evaluation of the meaning of these abnormalities as well as changes during therapy is needed. Disclosures All authors: No reported disclosures.

Insufficient serum L-ficolin is associated with disease presence and extent of pulmonary Mycobacterium avium complex disease

BackgroundThe incidence of infectious disease caused by nontuberculous mycobacteria is increasing worldwide. Pulmonary Mycobacterium avium complex (MAC) disease is difficult to treat with chemotherapy, and its mechanism of infection, infection route, disease onset, and severity remain unknown. Ficolins are oligomeric defense lectins. L-ficolin plays an important role in innate immunity. This study’s aim was to identify L-ficolin’s role in patients with pulmonary MAC disease.MethodsBetween April 2011 and September 2017, 61 Japanese patients with pulmonary MAC disease were seen at our hospital. A control group, comprising 30 healthy individuals, without respiratory disease were enrolled in our study. The relationship between serum L-ficolin levels and disease severity was assessed, and L-ficolin’s antibacterial role was examined.ResultsSerum L-ficolin levels were significantly lower in patients with pulmonary MAC disease than in healthy subjects (1.69 ± 1.27 μg/ml vs. 3.96 ± 1.42 μg/ml; p < 0.001). The cut-off value, based on receiver operating characteristic (ROC) analysis results, was 2.48 μg/ml (area under the curve (AUC) 0.90, sensitivity and specificity 83.6 and 86.7%, respectively). Serum L-ficolin levels were significantly lower in the patients with nodular bronchiectatic type disease compared with the patients with fibrocavitary type disease and were lower in the high-resolution computed tomography high-scoring group compared with low-scoring group. An in vitro analysis showed that purified recombinant L-ficolin bound to M. avium and its major cell wall component, lipoarabinomannan, in a concentration-dependent manner. In addition, recombinant L-ficolin suppressed M. avium growth in a concentration-dependent manner.ConclusionsInsufficient serum L-ficolin is associated with disease progression in pulmonary MAC disease, and the level of serum L-ficolin is a possible biomarker.Trial registrationThis study is registered with UMIN (UMIN000022392).

Preliminary validation of the NTM Module: a patient-reported outcome measure for patients with pulmonary nontuberculous mycobacterial disease.

Nontuberculous mycobacteria (NTM) cause chronic, debilitating pulmonary disease. Patient-reported outcomes provide measures of symptoms, functioning and treatment response. Here we describe the preliminary validation of the recently developed NTM Module. The study population included Northwest NTM Biobank patients in whom Mycobacterium avium complex (MAC) was isolated and who had ever met the 2007 American Thoracic Society/Infectious Diseases Society of America pulmonary disease criteria. The NTM Module was administered at enrolment and 12 months; a subset also completed the Quality of Life Questionnaire-Bronchiectasis (QOL-B). The NTM Module generates four domain scores (0-100; higher scores indicate better functioning) reflecting NTM-specific symptoms (NTM Symptoms, Body Image, Digestive Symptoms and Eating Problems). We described patient characteristics and mean scores, and evaluated psychometric properties, including response to treatment at 12 months, for each domain. Overall, 203 patients with pulmonary MAC disease were included. Average enrolment scores ranged from 76 (NTM Symptoms) to 84 (Eating Problems). Ceiling effects were observed for Body Image (26% of participants) and Eating Problems (52%). Internal consistency (Cronbach's alpha) ranged from 0.67 (Digestive Symptoms) to 0.89 (Eating Problems). The intraclass correlation for test-retest reproducibility (n=27) ranged from 0.72 (Body Image) to 0.94 (Eating Problems). Patients starting treatment (n=35) had statistically significant increases in scores for NTM Symptoms (+5, p=0.04), Digestive Symptoms (+7, p=0.002), Body Image (+7, p=0.03) and QOL-B Respiratory Symptoms (n=25, +10, p=0.006). NTM Symptoms scores increased by 15 points (p=0.002) in the 16 patients with scores ≤80 at enrolment. The NTM Module generally performs well as a valid patient-reported outcome for pulmonary MAC disease and was responsive to MAC treatment.

Intersectoral Cost of Treating Pulmonary Non-Tuberculosis Mycobacterial Disease (NTM-PD) in Germany-A Change of Perspective in Disease Management.

Background: In line with its increasing prevalence, pulmonary Mycobacterium avium complex (MAC) disease (MAC-PD) gives rise to substantial healthcare costs. However, there is only limited information on the costs of intersectoral reimbursement. Objectives: Inpatient and outpatient costs for diagnosing and treating pulmonary MAC-PD in Germany in accordance with standard international guidelines were calculated and their potential effects on MAC disease management in Germany were determined. Methods: Hospitalization costs were calculated by using the German diagnosis related group (G-DRG) browser, with and without inclusion of the diseases most often associated with M. avium. Separated by drug macrolide susceptibility and severity of MAC-PD, the direct medical costs of suitable therapies in the outpatient setting were determined by Monte-Carlo simulation, including all conceivable options. Results: According to our simulation, the weighted mean cost of outpatient treatment over 14 or 18 months, in either case followed by a post-treatment monitoring over 12 months, amounts to €8675.22 (95% confidence interval [CI] €8616.17 to €8734.27). Of that amount, the revenue for outpatient doctors´ services, dependent on treatment duration, is low, ranging between €894.79 (10.3%) and €979.42 (11.3%), accordingly. Mean drug costs for MAC-PD patients amount to €6130.25 [95% CI €6073.52 to €6186.98], i.e., more than two third (70.7%) of the total outpatient costs. In contrast, the non-surgical reimbursement for a hospital stay of up to 14 days is €3321.64. Hospital reimbursement does not increase in cases of complications (a higher number and/or challenging type of associated diseases), but it is fully paid even in cases that require as few as 2 days of hospitalization. Conclusion: The imbalance between well-rewarded hospital care and the low reimbursement for long-term treatment of MAC-PD outpatients may induce inappropriate disease management. In order to arrive at properly integrated care of MAC-PD patients in Germany, measures such as better incentives for physicians in the outpatient setting and a targeted use of resources in hospitals are required. Reimbursed, periodic case conferences between outpatient physicians and experts in hospitals as well as preventive short-term checks of MAC-PD patients in specialty clinics may promote cross-sector cooperation and improve overall treatment quality. Nationwide pilot studies are required to gain evidence on the effectiveness of the new approach.

Moxifloxacin resistance and genotyping of Mycobacterium avium and Mycobacterium intracellulare isolates in Japan

BackgroundAlthough fluoroquinolones are considered as alternative therapies of pulmonary Mycobacterium avium complex (MAC) disease, the association between fluoroquinolone resistance and MAC genotypes in clinical isolates from individuals not previously treated for MAC infection is not fully clear. MethodsTotals of 154 M. avium isolates and 35 Mycobacterium intracellulare isolates were obtained from treatment-naïve patients with pulmonary MAC disease at the diagnosis of MAC infection at 8 hospitals in Japan. Their susceptibilities of moxifloxacin were determined by broth microdilution methods. Moxifloxacin-resistant isolates were examined for mutations of gyrA and gyrB. Variable numbers of tandem repeats (VNTR) assay was performed using 15 M. avium VNTR loci and 16 M. intracellulare VNTR loci. ResultsMoxifloxacin susceptibility was categorized as resistant and intermediate for 6.5% and 16.9%, respectively, of M. avium isolates and 8.6% and 17.1% of M. intracellulare isolates. Although the isolates of both species had amino acid substitutions of Thr 96 and Thr 522 at the sites corresponding to Ser 95 in the M. tuberculosis GyrA and Gly 520 in the M. tuberculosis GyrB, respectively, these substitutions were observed irrespective of susceptibility and did not confer resistance. The VNTR assays showed revealed three clusters among M. avium isolates and two clusters among M. intracellulare isolates. No significant differences in moxifloxacin resistance were observed among these clusters. ConclusionsAlthough resistance or intermediate resistance to moxifloxacin was observed in approximately one-fourth of M. avium and M. intracellulare isolates, this resistance was not associated with mutations in gyrA and gyrB or with VNTR genotypes.

Application of a commercial serodiagnostic kit that measures the serum anti-glycopeptidolipid core IgA antibody in Mycobacterium avium complex pulmonary disease.

The diagnosis of Mycobacterium avium complex (MAC) pulmonary disease is occasionally cumbersome and time-consuming because the MAC species is ubiquitous, and therefore its detection is not necessarily indicative of a definitive diagnosis. A serodiagnostic method specific for MAC pulmonary disease that measures the serum anti-glycopeptidolipid core antigen IgA has been developed and is commercially available. Meta-analysis revealed that the test showed a good diagnostic accuracy. The estimated sensitivity and specificity values were 69.6% (95% confidence interval 62.1-76.1) and 90.6% (95% confidence interval 83.6-95.1), respectively. As antibody levels may reflect the disease activity, their serial measurement can also be used in the management of MAC disease. To justify its routine use in clinical practice, further validation in various regions and studies addressing whether serodiagnosis combined with present diagnostic criteria facilitate more rapid accurate diagnosis of MAC pulmonary disease are necessary.

Minocycline treatment for pulmonary Mycobacterium avium complex disease based on pharmacokinetics/pharmacodynamics and Bayesian framework mathematical models.

Our aim was to identify the pharmacokinetic/pharmacodynamic parameters of minocycline in the hollow-fibre system (HFS) model of pulmonary Mycobacterium avium complex (MAC) and to identify the optimal clinical dose. Minocycline MICs for 55 MAC clinical isolates from the Netherlands were determined. We also co-incubated primary isolated macrophages infected with MAC with minocycline. Next, we performed a 28 day HFS-MAC model dose-response study in which we mimicked pulmonary concentration-time profiles achieved in patients. The HFS-MAC model was sampled at intervals to determine the minocycline pharmacokinetics and MAC burden. We identified the AUC0-24/MIC ratios associated with 1.0 log10 cfu/mL kill below day 0 (stasis), defined as a bactericidal effect. We then performed 10000 Monte Carlo experiments to identify the optimal dose for a bactericidal effect in patients. The MIC for 50% and 90% of cumulative clinical isolates was 8 and 64 mg/L, respectively. Minocycline decreased MAC bacterial burden below stasis in primary isolated macrophages. In the HFS-MAC model, minocycline achieved a microbial kill of 3.6 log10 cfu/mL below stasis. The AUC0-24/MIC exposure associated with a bactericidal effect was 59. Monte Carlo experiments identified a minocycline susceptibility MIC breakpoint of 16 mg/L. At this proposed breakpoint, the clinical dose of 200 mg/day achieved the bactericidal effect exposure target in ∼50% of patients, while 400 mg/day achieved this in 73.6% of patients, in Monte Carlo experiments. Minocycline at a dose of 400 mg/day is expected to be bactericidal. We propose a clinical trial for validation.

Investigating the antimicrobial efficacy of MSCs as a potential novel therapy for Mycobacterium avium pulmonary infection

Non-tuberculous mycobacterial pulmonary disease (NTM-PD) has rapidly increased in global prevalence over the last two decades. NTM-PD occurs mainly in patients with pre-existing structural lung disease and current treatment strategies are often ineffective and poorly tolerated. Outside of the cystic fibrosis population, the most common NTM isolates are from Mycobacterium avium complex (MAC). Mesenchymal stromal cells (MSCs) have potent antimicrobial and immunomodulatory properties including direct microbial killing and enhancement of phagocytic function. Their effect on MAC species is unknown. Human MSCs were infected with M. avium at a multiplicity of infection (MOI) of 2. Human monocyte-derived macrophages (MDMs) were also infected with a clinical isolate of M. avium at MOI of 2. After 4 h, MSCs were added at a ratio of 1 MSC:3 MDMs. After 24 and 74 h, colony counts were performed on supernatants and cell lysates. MSCs reduced total bacterial counts of M. avium by 24 % at 24 h (from 295×103/ml to 225×103/ml, P&lt;0.05) and 40 % at 72 h (from 403×103/ml to 243×103/ml, P&lt;0.05). MSCs reduced total bacterial counts of M. avium in infected MDMs by &gt;40 % (from 381×103/ml to 209×103/ml, P&lt;0.05) after 24 h and &gt;70 % after 72 h (from 1050×103/ml to 314×103/ml, P&lt;0.05). MSCs have modest direct antimicrobial effect against MAC, but potently enhance their killing by macrophages. Mechanistic studies are required to understand the mechanisms of the antimicrobial effect, with the aim of exploiting these therapeutically in pulmonary MAC disease.