Mycobacterium Avium Complex Infection Research Articles

Exploring Benzo[h]chromene Derivatives as Agents against Protozoal and Mycobacterial Infections

Background/Objectives: In this study, the efficacy of benzo[h]chromene derivatives as antiprotozoal and antimycobacterial agents was explored. Methods: A total of twenty compounds, including benzo[h]chromene alkyl diesters and benzo[h]chromene-triazole derivatives, were synthesized and tested against Trypanosoma cruzi, Leishmania braziliensis, L. infantum, and strains of Mycobacterium abscessus and Mycobacterium intracellulare LIID-01. Notably, compounds 1a, 1b, 2a, and 3f exhibited superior activity against Trypanosoma cruzi, with IC50 values of 19.2, 37.3, 68.7, and 24.7 µM, respectively, outperforming the reference drug benznidazole (IC50: 54.7 µM). Results: Compounds 1b and 3f showed excellent selectivity indices against Leishmania braziliensis, with SI values of 19 and 18, respectively, suggesting they could be potential alternatives to the commonly used, but more selective, miltefosine (IC50: 64.0 µM, SI: 43.0). Additionally, compounds 1a, 1b, and 3f were most effective against Leishmania infantum, with IC50 values of 24.9, 30.5, and 46.6 µM, respectively. Compounds 3f and 3h were particularly potent against various Mycobacterium abscessus strains, highlighting their significance given the inherent resistance of these bacteria to standard antimicrobials. Conclusions: The sensitivity of Mycobacterium intracellulare LIID-01 to these compounds also underscored their potential in managing infections by the Mycobacterium avium–intracellulare complex.

Assays for Assessing Mycobacterium avium Immunity and Evaluating the Effects of Therapeutics.

In Europe and North America, the prevalence of pulmonary nontuberculous mycobacteria (NTM) is increasing. Most pulmonary NTM infections are caused by the Mycobacterium avium complex (MAC). Sadly, the treatment of pulmonary MAC is suboptimal with failure rates ranging from 37% to 58%. Therefore, there is a need to develop new therapeutics. Developing new immunotherapies and studying their interaction with standard or new drugs requires reliable assays. Four different assays including CFSE-based flow cytometry, in vitro protection assays, IFN-γ ELISPOT, and murine infection models were optimized using a reference strain of MAC (ATCC 700898) to help with the development of immunotherapies for MAC. Expansion of proliferating and IFN-γ producing human T cells is optimal after 7 days of stimulation with MAC at a multiplicity of infection (MOI) of 0.1, achieving a stimulation index of 26.5 ± 11.6 (mean ± SE). The in vitro protection assay for MAC works best by co-culturing T cells expanded for 7 days with MAC (MOI 1)-infected autologous macrophages. Aerosol MAC infection of mice allows measurement of the effects of the BCG vaccine and clarithromycin. IFN-γ ELISPOT assays with live MAC (MOI 3) stimulation of splenocytes from mice immunized with BCG help identify differences between unimmunized mice and mice immunized with BCG. In conclusion, multiple assays are available for use to identify MAC-specific effector T cells, which will help in the development of new therapeutics or vaccines against pulmonary MAC.

Facial cutaneous tuberculosis infected by non-tuberculous mycobacteria

BackgroundCutaneous infections caused by non-tuberculous mycobacteria (NTM) are extremely rare, particularly when they are localized to the facial area. This condition presents significant diagnostic challenges due to its unusual presentation and the need for precise microbiological identification.Case PresentationA two-year-old male patient presented with a progressively enlarging reddish-brown mass on the left side of his face. Despite the absence of systemic symptoms, the lesion’s growth warranted investigation due to its growth. Ultrasonography showed a hypoechoic mass in the dermis, indicating an underlying abscess. The subsequent aspiration resulted in pale yellow pus, which upon testing and culture, confirmed the presence of Mycobacterium avium complex infection, a species of NTM. This case exemplifies the synergy between imaging modalities and microbiological analysis, highlighting the crucial role of both in achieving favorable clinical outcomes in patients with suspected cutaneous NTM infections. Ultrasound can expedite diagnosis, improve treatment planning, and enhance patient care by enabling targeted interventions and monitoring response to therapy in these scenarios. However, it is the combination of pathogen-specific diagnostics that ensures accurate etiological attribution and appropriate antimicrobial stewardship.ConclusionAlthough rare, facial cutaneous infections caused by NTM still deserve thorough investigation to determine the exact cause. Ultrasound is used to identify cutaneous lesions, measure their extent, and guide surgical procedures. The ultimate diagnosis is based on microbiological confirmation.

Diagnostic Value of Targeted Next-generation Sequencing in Pulmonary Mycobacterial Infections.

This study aimed to explore the diagnostic value of novel technique-targeted next-generation sequencing (tNGS) of bronchoalveolar lavage fluid (BALF) in pulmonary mycobacterial infections. This retrospective study was conducted on patients who underwent bronchoscopy and tNGS, smear microscopy, and mycobacterial culture of BALF. Patients with positive Mycobacterium tuberculosis (MTB) culture or GeneXpert results were classified into the tuberculosis case group. Those diagnosed with nontuberculous mycobacteria (NTM)-pulmonary disease (NTM-PD) composed the case group of NTM-PD patients. The control group comprised patients without tuberculosis or NTM-PD. Sensitivity, specificity, and receiver operating characteristic (ROC) curves were used to evaluate the diagnostic performance. For tuberculosis patients with positive mycobacterial culture results, the areas under the ROC curves (AUCs) for tNGS, GeneXpert, and smear microscopy were 0.975 (95% CI: 0.935, 1.000), 0.925 (95% CI: 0.859, 0.991), and 0.675 (95% CI: 0.563, 0.787), respectively. For tuberculosis patients with positive GeneXpert results, the AUCs of tNGS, culture, and smear microscopy were 0.970 (95% CI: 0.931, 1.000), 0.850 (95% CI: 0.770, 0.930), and 0.680 (95% CI: 0.579, 0.781), respectively. For NTM-PD, the AUCs of tNGS, culture, and smear-positive but GeneXpert-negative results were 0.987 (95% CI: 0.967, 1.000), 0.750 (95% CI: 0.622, 0.878), and 0.615 (95% CI: 0.479, 0.752), respectively. The sensitivity and specificity of tNGS in NTM-PD patients were 100% and 97.5%, respectively. tNGS demonstrated superior diagnostic efficacy in mycobacterial infection, indicating its potential for clinical application.

7660 Navigating Hypercalcemia: MAC Treatment Hurdles and the Unforeseen Impact of Vitamin D Supplementation

Abstract Disclosure: S. Noguchi: None. S. Lai: None. A. Rajpal: None. Introduction: Hypercalcemia is a recognized complication in granulomatous disorders such as sarcoidosis and tuberculosis, resulting from increased 1 alpha-hydroxylase activity in macrophages leading to excessive conversion to 1,25(OH)2 vitamin D (calcitriol). Mycobacterium avium complex (MAC) is an infectious granulomatous disease often suspected in immunocompromised individuals, including those with human immunodeficiency virus (HIV). Additionally, vitamin D deficiency is prevalent in the general population, prompting supplementation. We hereby present a patient with advanced HIV and disseminated MAC who developed severe calcitriol-induced hypercalcemia in the setting of high dose vitamin D supplementation. Case description: A 48-year-old male with advanced HIV (CD4 count <20 cells/mm^3) presented for evaluation of abdominal pain and constipation, and was found to have severe hypercalcemia of 14.8 mg/dL. Five months prior, he had restarted anti-retroviral therapy (ART) after having been out of care for over a year and was diagnosed with disseminated MAC for which he was on azithromycin and ethambutol. Cultures drawn during this admission were negative for MAC. Hypercalcemia was possibly due to paradoxical immune reconstitution inflammatory syndrome (IRIS) and with appropriate management his calcium level rapidly normalized to 9.7 mg/dL and remained stable until the recent admission. He represented one year later with a calcium level of 13.8 mg/dL with suppressed parathyroid hormone levels, which was refractory to bisphosphonate therapy, therefore was empirically initiated on dexamethasone. By day 4, his calcium levels improved significantly and was discharged on a taper regimen. Cultures collected this admission later revealed ongoing MAC infection, which raised concern for treatment failure and calcitriol-induced hypercalcemia. Calcitriol levels were elevated at 105 pg/mL, which further supported this hypothesis. Additionally, prior to admission he had been prescribed ergocalciferol 50,000 units weekly for 8 weeks, after which he was transitioned to 2,000 units daily. This likely exacerbated the calcitriol-induced hypercalcemia by providing sudden availability of substrate, 25-OH vitamin D, for the activated macrophages. Conclusion: ART has reduced the incidence of opportunistic infections such as MAC, however mortality remains high. Vigilant monitoring for complications, particularly life-threatening calcitriol-induced hypercalcemia and timely use of corticosteroids, is crucial. This case also highlights the need for careful oversight in high-dose vitamin D supplementation for individuals with granulomatous disease and vitamin D dysregulation. Presentation: 6/2/2024

Total syntheses of mavintramycin A and its structural analog, cytosaminomycin C, and evaluation of their antibacterial activities against Mycobacterium avium and Mycobacterium intracellulare

Mavintramycin A is a new aminohexopyranose nucleoside antibiotic with potent anti-Mycobacterium avium complex (MAC) activity against M. avium and M. intracellulare. Herein, we report the total syntheses of mavintramycin A and its structural analog cytosaminomycin C, which is a known anticoccidial antibiotic. Furthermore, the anti-MAC activities of mavintramycin A, cytosaminomycin C, and their corresponding p-methoxybenzyl-protected analogs were evaluated. Notably, the developed synthetic route enables ready access to various analogs of mavintramycin A for structure-activity relationship studies.

Neglected Pulmonary Infection Caused by Exophiala dermatitidis Misidentified as Rhodotorula spp.

Exophiala dermatitidis is an emerging black fungus that causes pulmonary infections that may be underestimated by conventional culture methods. We encountered one case that initially appeared to be yeast and was misidentified as Rhodotorula spp. using a commercial identification kit. Thus, genetic identification and clinical background investigations were conducted on 46 strains of Rhodotorula spp. The sequences of the internal transcribed spacer and large-subunit RNA genes (D1/D2 regions) of 43 isolates, excluding two environmental isolates and one difficult-to-culture isolate, were determined and genetically identified. Notably, 22 isolates were identified as E. dermatitidis and misidentified as Rhodotorula spp. using the conventional method. Based on the exclusion criteria, the clinical information of 11 patients was retrospectively reviewed. Five cases (definite) had definite exacerbation of pulmonary infections due to E. dermatitidis, and six cases (possible) had undeniable infections. Of the 11 cases of pulmonary infection suggested to be caused by E. dermatitidis, comorbidities included two cases of chronic pulmonary aspergillosis (CPA), three cases of pulmonary non-tuberculous mycobacterial (NTM) infection and one case of pulmonary nocardiosis, suggesting a trend towards simultaneous detection of chronic pulmonary infections. Steroid and immunosuppressive drug use was observed in five cases, and β-D-glucan elevation was observed in three of five definite cases of pulmonary infections due to E. dermatitidis. The possibility of E. dermatitidis infection should be considered when Rhodotorula spp. are isolated from cultures of airway-derived specimens, and, in addition to CPA and NTM, identification of E. dermatitidis may be important in chronic pulmonary infections.

The use of dual β-lactams to restore susceptibility of Mycobacterium avium complex.

The Mycobacterium avium complex (MAC) are non-tuberculous mycobacteria responsible for chronic and debilitating conditions. Guideline-recommended therapy for MAC is a combination of clarithromycin/azithromycin, ethambutol and a rifamycin. However, culture conversion rates with this regimen are 67%. Alternative treatment options are needed. Recent findings of β-lactam combinations in the treatment of other mycobacterial diseases have been promising. The proposed mechanism is an additive inhibition of multiple enzymes in the peptidoglycan synthesis pathway by the β-lactam combinations. Given the similarity in cell wall structures of MAC and M. abscessus, we hypothesize that using dual β-lactams will result in interruption of peptidoglycan synthesis in MAC and reduction of MIC. In this study, we sought to determine the MIC of meropenem in combination with ceftaroline, cefdinir and cefuroxime in MAC. A total of 31 clinical MAC isolates were used for susceptibility testing using broth microdilution method. MICs were tested for meropenem, ceftaroline, cefdinir and cefuroxime, alone, as well as combinations of meropenem plus ceftaroline, cefdinir, or cefuroxime. In vitro MAC susceptibility to meropenem was significantly enhanced with the addition of ceftaroline, cefdinir, and cefuroxime. This effect was most significant with addition of ceftaroline and cefdinir, with a change of meropenem MIC50/MIC90 from 16/32 to 0.125/0.5 and 0.125/4 mg/L, respectively (P value ≤0.0001, Wilcoxon signed-rank test). This study demonstrates that the susceptibility of MAC to meropenem is restored with the addition of ceftaroline and cefdinir. These findings underscore the potential effectiveness of combining β-lactams as an alternative therapeutic strategy for MAC infections.

Clinical outcomes of lung transplant recipients with pre-transplant Mycobacterium avium complex infection.

Lung transplant recipients (LTRs) are at risk for Mycobacterium avium complex (MAC) infections, in part due to the presence of structural lung disease pre-transplant and relatively higher levels of immunosuppression post-transplant. There is a lack of data regarding outcomes of LTR with MAC infections pre-transplant. This is a single-center retrospective analysis of patients who received lung transplants (LTs) from 2013 to 2020 with 1) evidence of MAC on culture or polymerase chain reaction before or at the time of transplant or 2) granulomas on explant pathology and positive acid-fast bacillus stains with no other mycobacteria identified. Patients were deemed to have MAC pulmonary disease (MAC-PD) if they met the American Thoracic Society/Infectious Disease Society of America criteria. Fourteen patients (14/882, 2%) met inclusion criteria. Seven patients (7/14, 50%) had pre-transplant MAC-PD, four of whom had cavitary disease. None of the 14 patients had smear-positive cultures at the time of transplant. Two patients in our cohort received treatment for MAC before transplant. Thirteen patients were bilateral LTR (13/14, 93%). One single LTR was the sole patient to receive MAC treatment post-transplant. No patients developed MAC-PD after transplant. The bilateral LTR in our cohort did not develop MAC-PD despite not receiving MAC treatment post-transplant. It is possible source control was achieved with native lung explantation. Our observations suggest patients may not uniformly require pre- or post-transplant MAC treatment if they are smear-negative and undergo bilateral LT.

The Canadian Bronchiectasis and Nontuberculous Mycobacteria Registry: A Study Protocol

BackgroundBronchiectasis is a complex, chronic disease with geographic and ethnic diversity. While the most substantial cohort studies have been conducted in Europe and the USA, Canada also faces considerable challenges. The Comprehensive Canadian Bronchiectasis and Nontuberculous Mycobacterial Infection Registry aims to: (1) outline the clinical characteristics and natural history of bronchiectasis in Canada; (2) identify risk factors contributing to disease progression within Canadians; (3) integrate comprehensive clinical information to better understand the phenotypes of bronchiectasis; (4) support the development of large-scale, randomized controlled trials in Canada.MethodsThe Canadian Bronchiectasis and Nontuberculous Mycobacterial Infection Registry is an ongoing prospective, longitudinal, multi-center, observational cohort study. It aims to enroll at least 2000 participants to collect data such as medical history, etiological assessments, lung function tests, microbiological profiles, radiographic evaluations, comorbidities and quality of life (QoL) metrics. Participants will undergo annual follow-ups to gather longitudinal information regarding outcomes, treatments and changes in QoL. The inclusion criteria are a diagnosis of bronchiectasis by clinical history and computed tomography and/or pulmonary nontuberculous mycobacterial (NTM) infection as defined by ATS/IDSA guidelines. The study's protocol received ethical approval from the lead site, the University of Calgary, with future additional approval from local ethics committees at all participating centers.DiscussionThe outcomes of the registry will be instrumental in uncovering the clinical traits and natural history of bronchiectasis. This longitudinal study will be used for analysis to form evidence-based clinical practices and serve as a resource in Canada to inform future studies in NTM and bronchiectasis.

Disseminated Mycobacterium avium Complex Infection Following CD3/CD20 Bispecific Antibody Therapy in a Patient With Follicular Lymphoma.

Infections remain a major concern following bispecific antibody therapy but are not well described in pivotal trials. We present the first well-documented case of a classic but rare opportunistic infection, disseminated Mycobacterium avium complex, in a patient receiving bispecific antibody therapy.

Antibacterial action of penicillin against Mycobacterium avium complex.

β-lactam antibiotics are promising treatments for Mycobacterium avium complex (MAC) lung disease. We hypothesized that benzylpenicillin has efficacy against MAC. Benzylpenicillin lung concentration-time profiles of seven doses in three dosing schedules were administered for 28 days using the hollow fiber system model of intracellular MAC (HFS-MAC). Data were analyzed using the inhibitory sigmoid maximal effect (Emax) model for each sampling day, while two ordinary differential equations (ODEs) were used for the wild-type and penicillin-resistant mutants. Benzylpenicillin killed >2.1 log10 colony-forming unit (CFU)/mL below Day 0, better than azithromycin, ethambutol, and rifabutin. Efficacy was terminated by acquired resistance. Sigmoid Emax parameter estimates significantly differed between sampling days and were a poor fit. However, ODE model parameter estimates vs. exposure were a better fit. The exposure mediating Emax was 84.6% (95% CI 76.91-82.98) of time concentration exceeded the minimum inhibitory concentration (MIC). In Monte Carlo experiments, 24 million international units of benzylpenicillin continuous infusion achieved the target exposure in lungs of >90% of 10,000 subjects until an MIC of 64 mg/L, designated the susceptibility breakpoint. Benzylpenicillin demonstrated a better bactericidal effect against MAC than guideline-recommended drugs before the development of resistance. Its role in combination therapy with other drugs with better efficacy than guideline-recommended drugs should be explored.

New genetic biomarkers from transcriptome RNA-sequencing for Mycobacterium tuberculosis complex and Mycobacterium avium complex infections by bioinformatics analysis

The study aims to accurately identify differentially expressed genes (DEGs) and biological pathways in mycobacterial infections through bioinformatics for deeper disease understanding. Differentially expressed genes (DEGs) was explored by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Unique DEGs were submitted on least absolute shrinkage and selection operator (LASSO) regression analysis. 1,057 DEGs from two GSE datasets were identified, which were closely connected with NTM/ latent TB infection (LTBI)/active TB disease (ATB). It was demonstrated that these DEGs are mainly associated with detoxification processes, and virus and bacterial infections. Moreover, the METTL7B gene was the most informative marker for distinguishing LTBI and ATB with an area under the curve (AUC) of 0.983 (95%CI: 0.964 to 1). The significantly upregulated HBA1/2 genes were the most informative marker for distinguishing between individuals of IGRA-HC/NTM and LTBI (P < 0.001). Moreover, the upregulated HBD gene was also differ between IGRA-HC/NTM and ATB (P < 0.001). We have identified gene signatures associated with Mycobacterium infection in whole blood, which could be significant for understanding the molecular mechanisms and diagnosis of NTM, LTBI, or ATB.

Pharmacokinetics of anti-Mycobacterium avium-intracellulare disease drugs in silkworms

Pulmonary Mycobacterium avium-intracellulare complex (MAC) disease is a typical non-tuberculous mycobacterial infection. The incidence of pulmonary MAC is increasing worldwide. This study aimed to clarify the pharmacokinetic parameters of anti-pulmonary MAC disease drugs in silkworms. The pharmacokinetic parameters investigated included maximum concentration, area under the concentration–time curve, total clearance, and volume of distribution at steady-state. In addition, protein-binding rates, fat body transferability, and drug-drug interactions were examined. Antibiotic concentrations were measured using a validated high-performance liquid chromatography-mass spectrometry method. Among the antibiotics investigated, amikacin was not eliminated from silkworms during the 48-h observation period. In contrast, dose-proportional pharmacokinetics were observed in silkworms for all antibiotics tested, except for amikacin. Protein-binding rates in hemolymph for clarithromycin, azithromycin, rifampicin, ethambutol, and amikacin were 39.6 ± 3.0%, 39.5 ± 4.3%, 76.3 ± 3.2%, 20.9 ± 4.2%, and 73.1 ± 4.7%, respectively (mean ± standard deviation). The distribution of antibiotics in the fat bodies of silkworms was related to drug lipophilicity. No drug-drug interactions were observed in the silkworms. The pharmacokinetics of these drugs in silkworms differed significantly from those in humans. Therefore, while it is challenging to predict the pharmacokinetics of these drugs in humans based on silkworm data, the silkworm infection model has facilitated a comprehensive assessment of the relationship between antibiotic exposure and efficacy.

Clinical and genomic features of Mycobacterium avium complex: a multi-national European study

BackgroundThe Mycobacterium avium complex (MAC) comprises the most frequent non-tuberculous mycobacteria (NTM) in Central Europe and currently includes twelve species. M. avium (MAV), M. intracellulare subsp. intracellulare (MINT), and M. intracellulare subsp. chimaera (MCH) are clinically most relevant. However, the population structure and genomic landscape of MAC linked with potential pathobiological differences remain little investigated.MethodsWhole genome sequencing (WGS) was performed on a multi-national set of MAC isolates from Germany, France, and Switzerland. Phylogenetic analysis was conducted, as well as plasmids, resistance, and virulence genes predicted from WGS data. Data was set into a global context with publicly available sequences. Finally, detailed clinical characteristics were associated with genomic data in a subset of the cohort.ResultsOverall, 610 isolates from 465 patients were included. The majority could be assigned to MAV (n = 386), MCH (n = 111), and MINT (n = 77). We demonstrate clustering with less than 12 SNPs distance of isolates obtained from different patients in all major MAC species and the identification of trans-European or even trans-continental clusters when set into relation with 1307 public sequences. However, none of our MCH isolates clustered closely with the heater-cooler unit outbreak strain Zuerich-1. Known plasmids were detected in MAV (325/1076, 30.2%), MINT (62/327, 19.0%), and almost all MCH-isolates (457/463, 98.7%). Predicted resistance to aminoglycosides or macrolides was rare. Overall, there was no direct link between phylogenomic grouping and clinical manifestations, but MCH and MINT were rarely found in patients with extra-pulmonary disease (OR 0.12 95% CI 0.04–0.28, p < 0.001 and OR 0.11 95% CI 0.02–0.4, p = 0.004, respectively) and MCH was negatively associated with fulfillment of the ATS criteria when isolated from respiratory samples (OR 0.28 95% CI 0.09-0.7, p = 0.011). With 14 out of 43 patients with available serial isolates, co-infections or co-colonizations with different strains or even species of the MAC were frequent (32.6%).ConclusionsThis study demonstrates clustering and the presence of plasmids in a large proportion of MAC isolates in Europe and in a global context. Future studies need to urgently define potential ways of transmission of MAC isolates and the potential involvement of plasmids in virulence.

Identification of Nontuberculous Mycobacterium Species by Polymerase Chain Reaction - Restriction Enzyme Analysis (PCR-REA) of rpoB gene in Clinical Isolates.

Nontuberculous mycobacteria (NTM) infections are an emerging global health concern with increasing incidence. Conventional identification methods for NTM species in clinical settings are prone to errors. This study evaluates a newer method, polymerase chain reaction-restriction enzyme analysis (PCR-REA) of the rpoB gene, for NTM species identification. The study identified NTM species in clinical samples using conventional biochemical techniques and compared the results with PCR-REA of the rpoB gene. This cross-sectional study was conducted at a tertiary health-care center in North India over 18 months, analyzing both pulmonary and extrapulmonary samples. Two hundred and forty-seven NTM isolates were identified using phenotypic and biochemical methods. The same isolates were subjected to rpoB gene amplification by PCR followed by REA using Msp I and Hae III enzymes. Conventional methods identified 12 different NTM species (153 slow-growing and 94 rapid-growing), whereas PCR-REA identified 16 species (140 slow-growing, 107 rapid-growing). The Mycobacterium avium intracellulare complex was the most common species isolated. PCR-REA demonstrated higher resolution in species identification, particularly in differentiating within species complexes. PCR-REA of the rpoB gene proves to be a simple, rapid, and more discriminative tool for NTM species identification compared to conventional methods. This technique could significantly improve the diagnosis and management of emerging NTM infections in clinical settings.

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

BackgroundClofazimine (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. MethodsThis 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. ResultsThe 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. ConclusionCFZ-induced pigmentation and QT interval prolongation are associated with serum CFZ concentrations. CFZ dosage may be optimized by monitoring serum CFZ concentration.

Understanding the bacteria in Mycobacterium avium complex (MAC) from a bioinformatic perspective – a review

Mycobacterium avium complex (MAC) houses a group of non-tuberculous mycobacteria causing pulmonary and disseminated infections. They are accountable for nodular bronchiectatic and fibrocavitary lung diseases in humans, Johne’s disease in ruminants, and respiratory diseases in birds. MAC infections pose challenges, owing to antibiotic resistance, prolonged therapy with antibiotic combinations, side effects, and risk of reinfections. Our objective was to summarize the outcome of computational research on the bacteria in MAC. This aimed to advance our understanding of characteristics, pathogenicity, and transmission dynamics to control infections. We incorporated information from the research on genomes, microbiomes, phylogeny, transcriptomes, proteomes, antibiotic resistance, and vaccine/drug target development to enhance our knowledge. It illuminated the significance of computational studies in distinguishing MAC species/subspecies and recognizing: virulence factors, lineage-specific markers, and transmission clusters. Moreover, it assisted in understanding: genomic diversity, resistance patterns, impact of polymorphisms in disease susceptibility, and taxa-induced dysbiosis in microbiomes. Additionally, this work highlighted the outcome of bioinformatic studies in predicting suitable vaccine epitopes, and novel drug targets to combat MAC infections. Bioinformatic research on bacteria within MAC has contributed to a deeper insight into the pathogens. These would facilitate better diagnosis, improved: therapeutic strategies, patient-specific surveillance, and community-level awareness.

Ertapenem's therapeutic potential for Mycobacterium avium lung disease in the hollow fibre model

IntroductionGuideline-based therapy for Mycobacterium avium complex (MAC) pulmonary disease achieves sustained sputum conversion rates in only 43–53% of patients. Repurposing of β-lactam antibiotics such as ertapenem could expedite design of more efficacious regimens, compared to developing new drugs. MethodsWe performed an ertapenem exposure-response study in the hollow fibre system model of intracellular MAC (HFS-MAC). We recapitulated human-like intrapulmonary concentration-time profiles of eight once-daily intravenous doses of ertapenem over 28 days and performed repetitive sampling for drug concentration-time profiles and MAC burden. The % of time concentration persisted above MIC (%TMIC) mediating either 50% or 80% of maximal effect (E50, EC80) were identified. The EC80 was used as target exposure in a 10 000 subject Monte Carlo experiments for ertapenem doses of 1G, 2G, or 4G administered once versus twice daily. ResultsThe ertapenem MIC ranged from 0.5 to 2 mg/L on three occasions. Ertapenem achieved a half-life of 4.04 ± 0.80 h in the HFS-MAC and killed a maximum of 2.17 log10 CFU/mL below day 0. The EC50 was %TMIC of 75.9% (95% confidence interval: 68.43%–86.54%) and the EC80 was %TMIC of 100%. Target attainment probability was >90% for 1G twice daily up to an MIC of 2 mg/L, while for 2G twice daily the susceptibility MIC breakpoint was 4–8 mg/L. ConclusionsErtapenem microbial kill below day 0 burden was better than guideline-based therapy drugs in the HFS-MAC in the past. Ertapenem is a promising drug for novel combination therapies for MAC lung disease.

Increased susceptibility to Mycobacterium avium complex infection in miniature Schnauzer dogs caused by a codon deletion in CARD9

Mammals are generally resistant to Mycobacterium avium complex (MAC) infections. We report here on a primary immunodeficiency disorder causing increased susceptibility to MAC infections in a canine breed. Adult Miniature Schnauzers developing progressive systemic MAC infections were related to a common founder, and pedigree analysis was consistent with an autosomal recessive trait. A genome-wide association study and homozygosity mapping using 8 infected, 9 non-infected relatives, and 160 control Miniature Schnauzers detected an associated region on chromosome 9. Whole genome sequencing of 2 MAC-infected dogs identified a codon deletion in the CARD9 gene (c.493_495del; p.Lys165del). Genotyping of Miniature Schnauzers revealed the presence of this mutant CARD9 allele worldwide, and all tested MAC-infected dogs were homozygous mutants. Peripheral blood mononuclear cells from a dog homozygous for the CARD9 variant exhibited a dysfunctional CARD9 protein with impaired TNF-α production upon stimulation with the fungal polysaccharide β-glucan that activates the CARD9-coupled C-type lectin receptor, Dectin-1. While CARD9-deficient knockout mice are susceptible to experimental challenges by fungi and mycobacteria, Miniature Schnauzer dogs with systemic MAC susceptibility represent the first spontaneous animal model of CARD9 deficiency, which will help to further elucidate host defense mechanisms against mycobacteria and fungi and assess potential therapies for animals and humans.