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 Synergistic Effects of Omadacycline with Other Antimicrobial Agents against Mycobacterium abscessus.

The clinical importance of Mycobacterium abscessus species (MABS) infections has been increasing. However, the standard treatment regimens recommended in the current guidelines often result in unfavorable outcomes. Therefore, we investigated the in vitro activity of omadacycline (OMC), a novel tetracycline, against MABS to explore its potential as a novel therapeutic option. The drug susceptibilities of 40 Mycobacterium abscessus subsp. abscessus (Mab) clinical strains obtained from the sputum of 40 patients from January 2005 to May 2014 were investigated. The MIC results for OMC, amikacin (AMK), clarithromycin (CLR), clofazimine (CLO), imipenem (IPM), rifabutin (RFB), and tedizolid (TZD) alone and their combined effects (with OMC) were examined using the checkerboard method. Additionally, we studied the differences in the effectiveness of the antibiotic combinations based on the colony morphotype of Mab. The MIC50 and MIC90 of OMC alone were 2 and 4 µg/mL, respectively. The combinations of OMC with AMK, CLR, CLO, IPM, RFB, and TZD showed synergy against 17.5%, 75.8%, 25.0%, 21.1%, 76.9%, and 34.4% of the strains, respectively. Additionally, OMC combined with CLO (47.1% versus 9.5%, P = 0.023) or TZD (60.0% versus 12.5%, P = 0.009) showed significantly higher synergy against strains with rough morphotypes than those with smooth morphotypes. In conclusion, the checkerboard analyses revealed that the synergistic effects of OMC were observed most frequently with RFB, followed by CLR, TZD, CLO, IPM, and AMK. Furthermore, OMC tended to be more effective against rough-morphotype Mab strains.

A case of primary multidrug-resistant pulmonary tuberculosis with high minimum inhibitory concentration value for bedaquiline.

Bedaquiline is a new ATP synthesis inhibitor developed as an anti-tuberculosis agent. It has resistance-associated variants (RAV), regardless of preceding bedaquiline exposure. Herein, we describe the case of a patient with multidrug-resistant tuberculosis (MDR-TB) who had no history of bedaquiline therapy but presented a relatively high minimum inhibitory concentration (MIC) of bedaquiline (1 µg/mL). Whole genome sequencing revealed a mutation in the resistance-associated gene Rv0678. The patient was first treated with a five-drug regimen (bedaquiline, delamanid, levofloxacin, cycloserine, and amikacin), which induced negative sputum culture conversion. Despite the successful treatment outcome, several questions remain regarding the efficacy of bedaquiline in this patient. Bedaquiline is an indispensable drug for MDR-TB treatment, but its clinical efficiency in the presence of Rv0678 mutations remains unclear. Therefore, evaluating the MIC of bedaquiline even in patients without a history of bedaquiline use is important for therapeutic regimen selection and may emphasize the importance of therapeutic drug monitoring in cases of bedaquiline RAV.

Multidrug Resistant Tuberculosis With Simultaneously Acquired Drug Resistance to Bedaquiline and Delamanid.

This study is the first to report a clinical case of simultaneously acquired resistance to bedaquiline (BDQ) and delamanid (DLM). Whole genome sequencing revealed 2 nucleotide insertions (Rv0678 and fbiC) in the Mycobacterium tuberculosis isolate. The minimum inhibitory concentrations for BDQ and DLM were 0.25 µg/mL and >2.0 µg/mL, respectively.

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

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

Mycobacterium europaeum lung disease in an immunocompetent patient without underlying lung disease.

Mycobacterium europaeum (M. europaeum) was recently identified as a nontuberculous mycobacterium belonging to the Mycobacterium simiae complex. There have been only a few reported cases of M. europaeum lung disease, all of which occurred in patients with immunodeficiency or prior lung disease. We herein report a case of M. europaeum lung disease in an otherwise healthy Japanese individual. A 70-year-old woman who had no apparent immunodeficiency or medical history was diagnosed with M. europaeum lung disease by multiple positive sputum cultures. The patient was successfully treated with clarithromycin, rifampin, ethambutol, and amikacin. This report is the first case of M. europaeum lung disease occurring in an individual without predisposing risk factors.

Peritoneal dialysis-associated peritonitis caused by Mycobacteroides massiliense: the first case and review of the literature.

BACKGROUND: Peritoneal dialysis (PD)-associated peritonitis caused by nontuberculous Mycobacterium is rare; however, the number of cases has increased over the past decades. Mycobacteroides massiliense is a subspecies of the Mycobacteroides abscessus complex. It has different clinical characteristics compared to the other subspecies of the complex. Previous case reports of PD-associated peritonitis caused by Mycobacteroides abscessus complex have not distinguished the subspecies in detail. CASE PRESENTATION: A 40-year-old man presented with an exit-site and tunnel infection refractory to antibiotic therapy. Peritonitis occurred after simultaneous catheter removal and reinsertion. The Mycobacteroides abscessus complex was detected in the culture of the dialysis effluent. Removal of the PD catheter combined with antibiotics, including macrolides, resulted in a good clinical course. Further analysis of multiplex PCR and the hsp65 gene sequence identified the bacterium as Mycobacteroides massiliense. CONCLUSIONS: The Mycobacteroides abscessus complex is classified into three subspecies; Mycobacteroides abscessus, Mycobacteroides massiliense, and Mycobacteroides bolletii. These have different characteristics, particularly antibiotic susceptibility. Therefore, clear identification of the subspecies of the Mycobacteroides abscessus complex is necessary for definitive treatment.

A Multimethod, Multicountry Evaluation of Breakpoints for Bedaquiline Resistance Determination.

Criteria defining bedaquiline resistance for tuberculosis have been proposed addressing an emerging concern. We evaluated bedaquiline phenotypic drug susceptibility testing (pDST) criteria using drug-resistant tuberculosis clinical isolates tested at five reference laboratories. Isolates were tested at the proposed bedaquiline MGIT960 and 7H11 agar proportion (AP) critical concentrations and also at higher dilutions. The epidemiological cutoff value for the broth microdilution (BMD) plates (frozen and dry) was investigated. Sanger sequencing was performed (atpE and Rv0678 genes) for any isolate testing resistant. The composite reference standard (CRS) defined susceptibility or resistance as is if all pDST methods agreed. If the pDST result was discordant, sequencing results were used for final classification. Geographically diverse and bedaquiline-unexposed isolates were tested (n = 495). The epidemiological cutoff value for BMD was confirmed to be 0.12 µg/ml. The majority of isolates were determined to be susceptible by all methods (467/495; 94.3%), and 28 were determined to be resistant by at least one method; 4 of these were determined to be resistant by all methods. Of the 28 resistant isolates, 12 harbored Rv0678 mutations exclusively. Isolates with insertions/deletions were more likely to be determined to be resistant by more than one method (5/7) compared to isolates with a single nucleotide polymorphism (1/5). Applying the CRS to 24 discordant pDST, BMD dry correctly detected most (15/24; 63%), followed by MGIT960 and BMD frozen (13/24; 61%) and lastly AP (12/24; 50%). Applying the CRS, the prevalence of bedaquiline resistance was 2.2% and ranged from 1.4 to 3.4%, depending on the method used. All methods performed well for bedaquiline susceptibility determination; however, resistance detected should be investigated by a second, alternative method.

Validation of Bedaquiline Phenotypic Drug Susceptibility Testing Methods and Breakpoints: a Multilaboratory, Multicountry Study.

Drug-resistant tuberculosis persists as a major public health concern. Alongside efficacious treatments, validated and standardized drug susceptibility testing (DST) is required to improve patient care. This multicountry, multilaboratory external quality assessment (EQA) study aimed to validate the sensitivity, specificity, and reproducibility of provisional bedaquiline MIC breakpoints and World Health Organization interim critical concentrations (CCs) for categorizing clinical Mycobacterium tuberculosis isolates as susceptible/resistant to the drug. Three methods were used: Middlebrook 7H11 agar proportion (AP) assay, broth microdilution (BMD) assay, and mycobacterial growth indicator tube (MGIT) assay. Each of the five laboratories tested the 40-isolate (20 unique isolates, duplicated) EQA panel at three time points. The study validated the sensitivity and specificity of a bedaquiline MIC susceptibility breakpoint of 0.12 µg/ml for the BMD method and WHO interim CCs of 1 µg/ml for MGIT and 0.25 µg/ml for the 7H11 AP methods. Categorical agreements between observed and expected results and sensitivities/specificities for correctly identifying an isolate as susceptible/resistant were highest at the 0.25, 0.12, and 1 µg/ml bedaquiline concentrations for the AP method, BMD (frozen or dry plates), and MGIT960, respectively. At these concentrations, the very major error rates for erroneously categorizing an isolate as susceptible when it was resistant were the lowest and within CLSI guidelines. The most highly reproducible bedaquiline DST methods were MGIT960 and BMD using dry plates. These findings validate the use of standardized DST methodologies and interpretative criteria to facilitate routine phenotypic bedaquiline DST and to monitor the emergence of bedaquiline resistance.

Antimicrobial susceptibility testing of Mycobacteroides (Mycobacterium) abscessus complex, Mycolicibacterium (Mycobacterium) fortuitum, and Mycobacteroides (Mycobacterium) chelonae.

The drug susceptibility of rapidly growing mycobacteria (RGM) varies among isolates. Treatment strategies similarly differ depending on the isolate, and for some, no clear strategy has been identified. This complicates clinical management of RGM. Following Clinical and Laboratory Standards Institute standard M24-A2, we assessed the susceptibility of 140 RGM isolates to 14 different antimicrobial drugs by measuring their minimal inhibitory concentrations (MICs). We also investigated the correlation of clarithromycin (CAM) MICs with the erm(41) and rrl gene mutations in the Mycobacteroides (Mycobacterium) abscessus complex, the rrl mutation in Mycobacteroides (Mycobacterium) chelonae, and the erm(39) mutation in Mycolicibacterium (Mycobacterium) fortuitum to determine the contribution of these mutations to CAM susceptibility. The five species and subspecies examined included 48 M. abscessus subsp. abscessus isolates (34.3%), 35 (25.0%) being M. abscessus subsp. massiliense, and two (1.4%) being M. abscessus subsp. bolletii. The M. abscessus complex accounted for 85 isolates (60.7%) in total, whereas 43 isolates (30.7%) were M. fortuitum, and 12 (8.6%) were M. chelonae. Our results demonstrated species-specific susceptibility to antimicrobials. In most cases, susceptibility to CAM could be predicted based on genetic pattern, but since one isolate did not fit that pattern, MIC values needed to be measured. Some isolates also exhibited rates of resistance to other drugs that differed from those previously reported in other locations, indicating that accurate identification of the bacterial isolate and use of the correct method for determining MIC are both important for the diagnosis of RGM.

A case of Mycobacterium tuberculosis laboratory cross-contamination.

SETTING: A laboratory cross-contamination event was suspected because Mycobacterium tuberculosis was unexpectedly detected at a high incidence in the cultures of several clinical specimens at the National Hospital Organization, Tokyo National Hospital, Japan. OBJECTIVE: To describe a case of Mycobacterium tuberculosis laboratory cross-contamination. DESIGN: We reviewed the medical records of 20 patients whose clinical specimens were suspected to have been contaminated by Mycobacterium tuberculosis. Variable number of tandem repeat analysis with 15 loci, the Japan Anti-Tuberculosis Association-12, and three additional hyper-variable loci, was performed to identify the cross-contamination event. RESULTS: The clinical, laboratory, and variable number of tandem repeat data revealed that the cross-contamination had possibly originated from one strongly positive specimen, resulting in false-positive results in 11 other specimens, including a case treated with anti-tuberculosis drugs. CONCLUSION: Clinical and laboratory data must be re-evaluated when cross-contamination is suspected and variable number of tandem repeat analysis should be used to confirm cross-contamination. Furthermore, original isolates should be stored appropriately, without sub-culturing and genotyping should be performed at the earliest possible for better utilization of variable number of tandem repeat for the identification of cross-contamination.

Prediction of Local Transmission of Mycobacterium tuberculosis Isolates of a Predominantly Beijing Lineage by Use of a Variable-Number Tandem-Repeat Typing Method Incorporating a Consensus Set of Hypervariable Loci.

Strain genotyping based on the variable-number tandem repeat (VNTR) is widely applied for identifying the transmission of Mycobacterium tuberculosis A consensus set of four hypervariable loci (1982, 3232, 3820, and 4120) has been proposed to improve the discrimination of Beijing lineage strains. Herein, we evaluated the utility of these four hypervariable loci for tracing local tuberculosis transmission in 981 cases over a 14-month period in Japan (2010 to 2011). We used six different VNTR systems, with or without the four hypervariable loci. Patient ages and weighted standard distances (a measure of the dispersion of genotype-clustered cases) were used as proxies for estimating local tuberculosis transmission. The highest levels of isolate discrimination were achieved with VNTR systems that incorporated the four hypervariable loci (i.e., the Japan Anti-Tuberculosis Association [JATA]18-VNTR, mycobacterial interspersed repetitive unit [MIRU]28-VNTR, and 24Beijing-VNTR). The clustering rates by JATA12-VNTR, MIRU15-VNTR, JATA15-VNTR, JATA18-VNTR, MIRU28-VNTR, and 24Beijing-VNTR systems were 52.2%, 51.0%, 39.0%, 24.1%, 23.1%, and 22.0%, respectively. As the discriminative power increased, the median weighted standard distances of the clusters tended to decrease (from 311 to 80 km, P < 0.001, Jonckheere-Terpstra trend test). Concurrently, the median ages of patients in the clusters tended to decrease (from 68 to 60 years, P < 0.001, Jonckheere-Terpstra trend test). These findings suggest that strain typing using the four hypervariable loci improves the prediction of active local tuberculosis transmission. The four-locus set can therefore contribute to the targeted control of tuberculosis in settings with high prevalence of Beijing lineage strains.

Mycobacterium abscessus and massiliense lung infection during macrolide treatment for bronchiolitis obliterans after allogeneic hematopoietic stem cell transplantation.

In patients undergoing allogeneic hematopoietic stem cell transplantation (allo-SCT), post-transplant lung infection is critical for their prognosis. Mycobacterium abscessus complex is not fully recognized as a nontuberculous mycobacteria (NTM) pathogen of post-SCT lung infection. Here, we present three post-allogeneic SCT patients who developed pulmonary infection caused by M. abscessus complex including M. abscessus and M. massiliense. In all three cases, macrolide antibiotics had been administered for bronchiolitis obliterans syndrome (BOS) before the confirmation of their infection, and macrolide resistance was noted in the M. abscessus isolates, one of which resulted in an unfavorable treatment outcome. It is important to consider M. abscessus lung infection as well as other NTM in patients receiving allo-SCT, particularly those receiving macrolide therapy for BOS.

COBAS® TaqMan® MTB, smear positivity grade and MGIT culture; correlation analyses of three methods for bacillary quantification.

We investigated the correlation between the cycle threshold (Ct) value of the COBAS(®) TaqMan(®) MTB (TaqMan MTB), the mycobacterial smear positivity grade, and the time to detection (TTD) in the Mycobacteria Growth Indicator Tube (MGIT) for quantification of Mycobacterium tuberculosis (MTB). For 57 sputum samples, significant correlations were observed between the Ct value, the smear positivity grade, and the MGIT TTD (Spearman's rank correlation coefficient: r(s) = -0.940, P < 0.001 and Pearson's correlation coefficient: r(p) = 0.737, P < 0.001). In addition, a correlation was observed between the number of bacteria estimated based on the smear positivity grade and the number of MTB bacilli calculated by the Ct value (r(s) = 0.930, P < 0.001). This study has demonstrated the possible estimation of the smear positivity grade and MGIT TTD using the Ct value of TaqMan MTB, which is based on a real-time PCR system, for diagnostic samples.

[SPECIFICITY EVALUATION OF TRCReady® MTB AND TRCReady® MAC FOR IDENTIFYING MYCOBACTERIUM TUBERCULOSIS COMPLEX, MYCOBACTERIUM AVIUM AND MYCOBACTERIUM INTRACELLULARE].

[Objective] To evaluate the specificity of TRC- Ready® MTB and TRCReady® MAC (Tosoh Bioscience, Japan) for identifying M.tubercidosis complex (MTC), M.avium and M. intracellulare. [Method] We tested TRCReady® MTB and TRCReady® MAC using TRCReady®-80 (Tosoh Bioscience, Japan), which is an automated nucleic amplification test instrument, with 151 Mycobacterium species (4 MTC and 147 Non-tuberculosis Mycobacterium (NTM) type strains). [Results] The specificity of TRCReady® MTB was 100%, however, TkCReady® MAC misidentified a total of six NTMs, M.arosiense, M.chimaera, M.colombiense, M.marseillense, M. vulneris and M.yongonense, as M. intracellulare. Then, the specificity for TRCReady® MAC was 96.0% (145/151). [Discussion] TRCReady® MTB and TRCReady® MAC are highly specific for identifying MTC, M.avium and M. intracellulare. Six NTM species which have been rarely isolated in Japan showed false-positive results as M.intra- celludare. However, when a sample was identified as M.in- tracellulare, the phenotypic characteristics like colony mor- phology would be carefully examined.

[EXTERNAL QUALITY ASSESSMENT OF ANTI-TUBERCULOSIS DRUG SUSCEPTIBILITY TESTING FOR DIAGNOSING EXTENSIVELY DRUG-RESISTANT MYCOBACTERIUM TUBERCULOSIS].

[Objective] The infectious disease control law has been amended in May 2015, and the category definition of Mycobacterium tuberculosis as infectious pathogen has been changed, following the definition of extensively drug-resistant M.tuberculosis (XDR-TB) by World Health Organization. To assess the diagnostic capacity of XDR-TB, we conducted an external quality assessment (EQA) for the anti-tuberculosis drug susceptibility testing (DST). [Method] A total of 10 M.tuberculosis strains with known drug susceptibility were sent to each participating laboratory. The drugs assessed were isoniazid (INH), rifampicin (RFP), streptomycin (SM), ethambutol (EB), levofloxacin (LVFX), and kanamycin (KM). DST was performed using each routine method(s), and the results were compared with the judicial diagnoses. The sensitivity, specificity, overall agreement (effi- ciency) and kappa coefficient were calculated for each drug tested. In addition, the diagnostic accuracy of multidrug-resis- tant M. tuberculosis (MDR-TB) and XDR-TB was assessed. [Results] A total of 88 institutes including 67 hospitals, 16 commercial laboratories, and 5 public health laboratories par- ticipated in the EQA. With 2 laboratories submitting 2 sets of results, a total of 90 independent data sets were analyzed. As for INH, RFP and LVFX, the efficiency was over 95%, but we found two strains each for SM, EB and KM with the efficiency less than 95%. Especially, strain 1 and strain 2 showed efficiency of 72.2% and 71.1% to SM, respectively. This error was mainly found in a certain test kit. If we consider the passing score as showing ≥95 % sensitivity and specificity both to INH and RFP, the diagnostic accuracy of MDR-TB was 92.2% (83/90) in this study. With the same criteria to INH, RFP, LVFX and KM, that of XDR-TB was 79.7% (63/79). [Discussion] The diagnostic capacity of XDR-TB was not sufficient in the current study. Good case management and pathogen control requires higher accuracy. The government may need to conduct a constant EQA and relevant remedial actions.

Association between pncA gene mutations, pyrazinamidase activity, and pyrazinamide susceptibility testing in Mycobacterium tuberculosis.

We determined MICs for, confirmed the presence of pncA mutations in, and performed pyrazinamidase testing on colonies (subclones) obtained from seven isolates that exhibited differential pyrazinamide (PZA) susceptibility. Six of the seven strains were found to exhibit characteristics resulting from the mixture of strains possessing different properties. In addition, our analysis revealed large pncA-spanning deletions (1,565 bp, 4,475 bp, and 6,258 bp) in three strains that showed high PZA resistance.

Comparative evaluation of three immunochromatographic identification tests for culture confirmation of Mycobacterium tuberculosis complex.

BACKGROUND: The rapid identification of acid-fast bacilli recovered from patient specimens as Mycobacterium tuberculosis complex (MTC) is critically important for accurate diagnosis and treatment. A thin-layer immunochromatographic (TLC) assay using anti-MPB64 or anti-MPT64 monoclonal antibodies was developed to discriminate between MTC and non-tuberculosis mycobacteria (NTM). Capilia TB-Neo, which is the improved version of Capilia TB, is recently developed and needs to be evaluated. METHODS: Capilia TB-Neo was evaluated by using reference strains including 96 Mycobacterium species (4 MTC and 92 NTM) and 3 other bacterial genera, and clinical isolates (500 MTC and 90 NTM isolates). M. tuberculosis isolates tested negative by Capilia TB-Neo were sequenced for mpt64 gene. RESULTS: Capilia TB-Neo showed 100% agreement to a subset of reference strains. Non-specific reaction to M. marinum was not observed. The sensitivity and specificity of Capilia TB-Neo to the clinical isolates were 99.4% (99.6% for M. tuberculosis, excluding M. bovis BCG) for clinical MTC isolates and 100% for NTM isolates tested, respectively. Two M. tuberculosis isolates tested negative by Capilia TB-Neo: one harbored a 63-bp deletion in the mpt64 gene and the other possessed a 3,659-bp deletion from Rv1977 to Rv1981c, a region including the entire mpt64 gene. CONCLUSIONS: Capilia TB-Neo is a simple, rapid and highly sensitive test for identifying MTC, and showed better specificity than Capilia TB. However, Capilia TB-Neo still showed false-negative results with mpt64 mutations. The limitation should be recognized for clinical use.

[Evaluation of the use of SPEED-OLIGO Mycobacteria for identification of Mycobacterium species].

OBJECTIVE: To evaluate the use of SPEED-OLIGO MYCOBACTERIA (Vircell, Spain) in identifying Mycobacterium species. METHOD: We examined 15 type or reference strains of mycobacteria (M. tuberculosis H37Rv and 14 non-tuberculosis mycobacteria), 48 clinical isolates, and 17 AFB-positive sputa by using SPEED-OLIGO MYCOBACTERIA, and compared the results with those obtained using other referral methods available for species identification. RESULT: SPEED-OLIGO MYCOBACTERIA yielded favorable results in 80.0%, 91.7%, and 88.2% of the cases of the tested type/reference strains, clinical isolates, and clinical samples, respectively. However, the type/reference strains M. celatum, M. fortuitum subsp. fortuitum, and M. marinum, and the clinical isolates M. intermedium, M. marinum, and M. szulgai were misidentified when SPEED-OLIGO MYCOBACTERIA was used. DISCUSSION: SPEED-OLIGO MYCOBACTERIA can facilitate the rapid identification of Mycobacterium species mainly because of its short turn-around time and simple procedures. However, the accuracy of this method remains unsatisfactory.

Clofazimine serum concentration and safety/efficacy in nontuberculous mycobacterial pulmonary disease treatment.

BACKGROUND: Clofazimine (CFZ) has shown promising effects against Mycobacterium avium-intracellulare complex pulmonary disease (MAC-PD) and Mycobacterium abscessus species pulmonary disease (MABS-PD). However, the optimal CFZ dose remains unknown. We aimed to explore the relationship between steady-state CFZ concentration and its safety and efficacy in MAC-PD and MABS-PD. METHODS: This prospective observational study focused on patients with MAC-PD and MABS-PD treated with CFZ (UMIN 000041053). To understand the safety and efficacy profile of CFZ and elucidate its optimal concentration, we analyzed CFZ-induced pigmentation grade, QTc interval, and culture conversion outcomes in relation to serum CFZ concentration using Student's t-test, a concentration-QTc model, and multivariable logistic regression analysis, respectively. In total, 64 patients (34 with MAC-PD; 30 with MABS-PD) were included. RESULTS: The steady-state concentration of CFZ was higher in the moderate-to-severe pigmentation group than in the none-to-light pigmentation group (P < 0.001). At a CFZ concentration of 1 mg/L, the QTc interval was prolonged by 17.3 ms (95 % confidence interval [CI], 3.9-25.4) from baseline. Culture conversion was achieved in 33 (51.6 %) patients. The only significant predictor of culture conversion was surgery (adjusted odds ratio, 5.4; 95 % CI, 1.3-38.0). CFZ concentration and MIC of CFZ less than 0.25 mg/L were not associated with culture conversion in this study. CONCLUSION: CFZ-induced pigmentation and QT interval prolongation are associated with serum CFZ concentrations. CFZ dosage may be optimized by monitoring serum CFZ concentration.