Mycobacterium Avium Complex Infection Research Articles

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.

An Uncommon Cause of Elevated Liver Transaminases: Immune Reconstitution Inflammatory Syndrome from Unmasking of Occult Mycobacterium Avium Complex Infection in an HIV Infected Patient

Abnormal liver chemistry from the development of immune reconstitution inflammatory syndrome (IRIS) may reflect an unmasking of subclinical disease. We present the case of a 37-year-old female with a mixed pattern of liver injury from disseminated mycobacterium avium complex infection after starting antiretroviral therapy (ART). Presenting symptoms were fever, confusion, dysphagia, and abdominal discomfort for one week. Exam revealed a fever of 103.2°F, hypotension, encephalopathy, and abdominal tenderness. Lab work was significant for acute normocytic anemia, leukopenia, absolute CD4 count 28 cells/cmm, HIV viral load 276 viral copies/ml (vc/ml), ALT 267 U/L, AST 484 U/L, alkaline phosphatase 342 U/L, and normal total bilirubin. Imaging revealed hepatomegaly with steatosis and mesenteric and retroperitoneal lymphadenopathy. Percutaneous liver biopsy demonstrated noncaseating granulomas with AFB-positive organisms, with AFB blood cultures growing Mycobacterium avium complex (MAC), consistent with disseminated MAC infection. Clinicians must have a high index of suspicion for IRIS when determining the etiology of elevated liver transaminases in patients with HIV.

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

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

Transcriptome analysis of long non-coding RNAs in Mycobacterium avium complex-infected macrophages.

Mycobacterium avium complex (MAC) is a non-tuberculous mycobacterium widely distributed in the environment. Even though MAC infection is increasing in older women and immunocompromised patients, to our knowledge there has been no comprehensive analysis of the MAC-infected host-cell transcriptome-and particularly of long non-coding RNAs (lncRNAs). By using in vitro-cultured primary mouse bone-marrow-derived macrophages (BMDMs) and Cap analysis of gene expression, we analyzed the transcriptional and kinetic landscape of macrophage genes, with a focus on lncRNAs, during MAC infection. MAC infection of macrophages induced the expression of immune/inflammatory response genes and other genes similar to those involved in M1 macrophage activation, consistent with previous reports, although Nos2 (M1 activation) and Arg1 (M2 activation) had distinct expression profiles. We identified 31 upregulated and 30 downregulated lncRNA promoters corresponding respectively to 18 and 26 lncRNAs. Upregulated lncRNAs were clustered into two groups-early and late upregulated-predicted to be associated with immune activation and the immune response to infection, respectively. Furthermore, an Ingenuity Pathway Analysis revealed canonical pathways and upstream transcription regulators associated with differentially expressed lncRNAs. Several differentially expressed lncRNAs reported elsewhere underwent expressional changes upon M1 or M2 preactivation and subsequent MAC infection. Finally, we showed that expressional change of lncRNAs in MAC-infected BMDMs was mediated by toll-like receptor 2, although there may be other mechanisms that sense MAC infection. We identified differentially expressed lncRNAs in MAC-infected BMDMs, revealing diverse features that imply the distinct roles of these lncRNAs in MAC infection and macrophage polarization.

Epidemiological Characteristics of Nontuberculous Mycobacterial Pulmonary Disease in South Korea: A Meta-Analysis of Individual Participant Data.

Despite the global increase in nontuberculous mycobacterial pulmonary disease (NTM-PD), there are geographical variations in clinical characteristics. We investigated the clinical characteristics of patients with NTM-PD in South Korea. We systematically reviewed articles about patients with NTM-PD in South Korea until February 2022. Individual participant data, regardless of treatment, were collected using a standard case report form. The data of 6,489 patients from 11 hospitals between 2002 and 2019 were analyzed. The mean age was 61.5 ± 11.7 years, and 57.7% were women. Mycobacterium avium (41.4%) and Mycobacterium intracellulare (38.4%) comprised most of the causative species, followed by Mycobacterium abscessus subspecies abscessus (8.6%) and Mycobacterium abscessus subspecies massiliense (7.8%). Bronchiectasis (59.4%) was the most common pulmonary comorbidity. Reported cases of NTM-PD increased over the years, but the proportions of causative species and radiologic forms remained similar. Distinct clinical characteristics were observed according to age and sex. Men were older at the time of diagnosis (median 63.8 vs. 59.9 years, P<0.001) and had more cavitary lesions than women (38.8% vs. 21.0%, P<0.001). The older group (≥65 years) had a higher proportion of patients with body mass index <18.5 kg/m2 (27.4% vs. 18.6%, P<0.001) and cavitary lesions (29.9% vs. 27.6%, P=0.009) than the younger group. We performed a meta-analysis of the clinical characteristics of patients with NTM-PD in South Korea. We found age- and sex-related differences in disease-specific severity. Further investigation would enhance our comprehension of the disease's nature and inherited and acquired host factors.

Efficacy of SPR720 in murine models of non-tuberculous mycobacterial pulmonary infection.

Non-tuberculous mycobacterial pulmonary disease (NTM-PD) is increasing worldwide, with Mycobacterium avium complex (MAC) and Mycobacterium abscessus as the predominant pathogens. Current treatments are poorly tolerated and modestly effective, highlighting the need for new treatments. SPR719, the active moiety of the benzimidazole prodrug SPR720, inhibits the ATPase subunits of DNA gyrase B, a target not exploited by current antibiotics, and therefore, no cross-resistance is expected with standard-of-care (SOC) agents. To evaluate the in vitro activity of SPR719 against MAC and M. abscessus clinical isolates, including those resistant to SOC agents, and in vivo efficacy of SPR720 in murine non-tuberculous mycobacteria (NTM) pulmonary infection models. NTM isolates were tested for susceptibility to SPR719. Chronic C3HeB/FeJ and severe combined immunodeficient murine models of pulmonary infection were used to assess efficacy of SPR720 against MAC and M. abscessus, respectively. SPR719 was active against MAC (MIC90, 2 mg/L) and M. abscessus (MIC90, 4 mg/L) clinical isolates. Efficacy of SPR720 was demonstrated against MAC pulmonary infection, both as a monotherapy and in combination with SOC agents. SPR720 monotherapy exhibited dose-dependent reduction in bacterial burden, with the largest reduction observed when combined with clarithromycin and ethambutol. Efficacy of SPR720 was also demonstrated against M. abscessus pulmonary infection where monotherapy exhibited a dose-dependent reduction in bacterial burden with further reductions detected when combined with SOC agents. In vitro activity of SPR720 against common NTM pathogens and efficacy in murine infections warrant the continued clinical evaluation of SPR720 as a new oral option for the treatment of NTM-PD.

Hypercalcemia as a rare manifestation of immune reconstitution inflammatory syndrome (IRIS) in a person living with Human Immunodeficiency Virus (HIV) with disseminatednontuberculous mycobacteriosis.

Granulomatosis due to immune reconstitution inflammatory syndrome (IRIS) and disseminated Mycobacterium avium-intracellulare (M. avium) infection may trigger hypercalcemia. Here, we report a rare case of hypercalcemia and acute kidney damage related to IRIS in a person living with Human Immunodeficiency Virus (HIV). A 39-year-old male person living with HIV presented with muscle weakness and unwanted weight loss of 8kg within the last 2weeks. Laboratory findings included serum hypercalcemia of 3.27mmol/mL associated with elevated calcitriol and acute kidney damage. Since the first diagnosis of HIV and concomitant disseminated M. avium infection, the patient received antiretroviral therapy (ART), rifabutin, clarithromycin, and ethambutol. 18Fluoro-D-glucose positron emission computed tomography (18FDG-PET/CT) showed progressive multilocular lymphadenopathy. Biopsy specimen from the duodenum as well as retroperitoneal and mediastinal lymph nodes revealed granulomatous inflammation consistent with IRIS. Treatment with forced diuresis, bisphosphonates, and calcitonin normalized serum calcium and kidney function recovered. Hypercalcemia due to IRIS is a rare differential diagnosis in persons living with HIV and may lead to acute kidney damage, despite sufficient ART and antimycobacterial treatment.

Bigger problems from smaller colonies: emergence of antibiotic-tolerant small colony variants of Mycobacterium avium complex in MAC-pulmonary disease patients.

Mycobacterium avium complex (MAC) is a group of slow-growing mycobacteria that includes Mycobacterium avium and Mycobacterium intracellulare. MAC pulmonary disease (MAC-PD) poses a threat to immunocompromised individuals and those with structural pulmonary diseases worldwide. The standard treatment regimen for MAC-PD includes a macrolide in combination with rifampicin and ethambutol. However, the treatment failure and disease recurrence rates after successful treatment remain high. In the present study, we investigated the unique characteristics of small colony variants (SCVs) isolated from patients with MAC-PD. Furthermore, revertant (RVT) phenotype, emerged from the SCVs after prolonged incubation on 7H10 agar. We observed that SCVs exhibited slower growth rates than wild-type (WT) strains but had higher minimum inhibitory concentrations (MICs) against multiple antibiotics. However, some antibiotics showed low MICs for the WT, SCVs, and RVT phenotypes. Additionally, the genotypes were identical among SCVs, WT, and RVT. Based on the MIC data, we conducted time-kill kinetic experiments using various antibiotic combinations. The response to antibiotics varied among the phenotypes, with RVT being the most susceptible, WT showing intermediate susceptibility, and SCVs displaying the lowest susceptibility. In conclusion, the emergence of the SCVs phenotype represents a survival strategy adopted by MAC to adapt to hostile environments and persist during infection within the host. Additionally, combining the current drugs in the treatment regimen with additional drugs that promote the conversion of SCVs to RVT may offer a promising strategy to improve the clinical outcomes of patients with refractory MAC-PD.

Anticancer and Antibacterial Properties of Curcumin-Loaded Mannosylated Solid Lipid Nanoparticles for the Treatment of Lung Diseases.

Lung cancer and Mycobacterium avium complex infection are lung diseases associated with high incidence and mortality rates. Most conventional anticancer drugs and antibiotics have certain limitations, including high drug resistance rates and adverse effects. Herein, we aimed to synthesize mannose surface-modified solid lipid nanoparticles (SLNs) loaded with curcumin (Man-CUR SLN) for the effective treatment of lung disease. The synthesized Man-CUR SLNs were analyzed using various instrumental techniques for structural and physicochemical characterization. Loading curcumin into SLNs improved the encapsulation efficiency and drug release capacity, as demonstrated by high-performance liquid chromatography analysis. Furthermore, we characterized the anticancer effect of curcumin using the A549 lung cancer cell line. Cells treated with Man-CUR SLN exhibited an increased cellular uptake and cytotoxicity. Moreover, treatment with free CUR could more effectively reduce cancer migration than treatment with Man-CUR SLNs. Similarly, free curcumin elicited a stronger apoptosis-inducing effect than that of Man-CUR SLNs, as demonstrated by reverse transcription-quantitative PCR analysis. Finally, we examined the antibacterial effects of free curcumin and Man-CUR SLNs against Mycobacterium intracellulare (M.i.) and M.i.-infected macrophages, revealing that Man-CUR SLNs exerted the strongest antibacterial effect. Collectively, these findings indicate that mannose-receptor-targeted curcumin delivery using lipid nanoparticles could be effective in treating lung diseases. Accordingly, this drug delivery system can be used to target a variety of cancers and immune cells.

Mycobacterial spindle cell pseudotumor of the spinal cord: Case report and literature review

We report the first description of spinal cord mycobacterial spindle cell pseudotumor. A patient with newly diagnosed advanced HIV presented with recent-onset bilateral leg weakness and was found to have a hypermetabolic spinal cord mass on structural and molecular imaging. Biopsy and cultures from blood and cerebrospinal fluid confirmed spindle cell pseudotumor due to Mycobacterium avium-intracellulare. Despite control of HIV and initial reduction in pseudotumor volume on antiretrovirals and antimycobacterials (azithromycin, ethambutol, rifampin/rifabutin), he ultimately experienced progressive leg weakness due to pseudotumor re-expansion. Here, we review literature and discuss multidisciplinary diagnosis, monitoring and management challenges, including immune reconstitution inflammatory syndrome.

Synthesis and in vitro Metabolic Stability of Sterically Shielded Antimycobacterial Phenylalanine Amides.

Nα-aroyl-N-aryl-phenylalanine amides (AAPs) are RNA polymerase inhibitors with activity against Mycobacterium tuberculosis and non-tuberculous mycobacteria. We observed that AAPs rapidly degrade in microsomal suspensions, suggesting that avoiding hepatic metabolism is critical for their effectiveness in vivo. As both amide bonds are potential metabolic weak points of the molecule, we synthesized 16 novel AAP analogs in which the amide bonds are shielded by methyl or fluoro substituents in close proximity. Some derivatives show improved microsomal stability, while being plasma-stable and non-cytotoxic. In parallel with the metabolic stability studies, the antimycobacterial activity of the AAPs against Mycobacterium tuberculosis, Mycobacterium abscessus, Mycobacterium avium and Mycobacterium intracellulare was determined. The stability data are discussed in relation to the antimycobacterial activity of the panel of compounds and reveal that the concept of steric shielding of the anilide groups by a fluoro substituent has the potential to improve the stability and bioavailability of AAPs.

Mavintramycin A is a promising antibiotic for treating Mycobacterium avium complex infectious disease.

Mycobacterium avium complex (MAC) is a serious disease that is mainly caused by infection with the non-tuberculous mycobacteria (NTM), Mycobacterium avium and Mycobacterium intracellulare. Seven new compounds, designated mavintramycins A-G (1-7), were isolated along with structurally related compounds, including amicetin (9) and plicacetin (10), from the culture broth of Streptomyces sp. OPMA40551 as anti-MAC compounds that were active against M. avium and M. intracellulare. Among them, mavintramycin A showed the most potent and selective inhibition of M. avium and M. intracellulare. Furthermore, mavintramycin A was active against more than 40 clinically isolated M. avium, including multidrug-resistant strains, and inhibited the growth of M. avium in a persistent infection cell model using THP-1 macrophages. Mavintramycin A also exhibited in vivo efficacy in silkworm and mouse infection assays with NTM. An experiment to elucidate its mechanism of action revealed that mavintramycin A inhibits protein synthesis by binding to 23S ribosomal RNA in NTM. Mavintramycin A, with a different chemical structure from those of clinically used agents, is a promising drug candidate for the treatment of MAC infectious disease.

Survey of Mycobacterium spp. in Eurasian Badgers (Meles meles) in Central Italy.

A survey to determine the presence of Mycobacterium spp. in the Abruzzo and Molise regions was conducted by testing samples from 124 badgers found dead or road-killed during the 2013-2021 period. Head lymph nodes were collected from all carcasses, as well as mediastinal lymph nodes from 20 of them, for bacteriological and molecular tests; tissues were inoculated onto a set of solid egg-based Lowenstein-Jensen media and in a liquid culture system (BACTEC) and were analyzed by polymerase chain reactions (PCRs). Organs and lymph nodes from 31 carcasses were collected for histological tests. During post-mortem examinations, macroscopic lesions consistent with a Mycobacterium tuberculosis complex (MTBC) and with nontuberculous mycobacteria (NTM) infections were not detected. Mycobacteria were isolated from four animals (3.22%). M. avium subsp. avium was isolated by head lymph nodes from two badgers (1.61%), M. avium subsp. paratuberculosis (0.80%) from one, and Mycobacterium spp. from another (0.80%). The significance of nontuberculous mycobacteria (NTM) in wildlife hosts in the absence of clinical signs and gross pathology has yet to be assessed. The most critical aspect came from isolates belonging to the Mycobacterium avium complex infection in wildlife due to the possible interference with tuberculin skin tests in cattle.

Serum Cell-free DNA-based Detection of Mycobacterium Avium Complex Infection.

Mycobacterium avium complex (MAC) is the most common cause of nontuberculous mycobacterial pulmonary disease (NTM-PD), which exhibits increasing global incidence. Current microbiologic methods routinely used in clinical practice lack sensitivity and have long latencies, leading to delays in diagnosis and treatment initiation and evaluation. A CRISPR-based assay that measures MAC cell-free DNA (MAC-cfDNA) levels in serum could provide a rapid means to detect MAC infection and monitor response to antimicrobial treatment. To develop and optimize a CRISPR-MAC assay for MAC infection detection and to evaluate its diagnostic and prognostic performance in two MAC disease cohorts. MAC-cfDNA serum levels were measured in individuals diagnosed with MAC disease or who had bronchiectasis or COPD diagnoses without a history of NTM-PD or NTM-positive sputum cultures. Diagnostic performance was analyzed with pre-treatment serum from two cohorts. Serum MAC-cfDNA changes during MAC-PD treatment were evaluated in a subset of MAC-PD patients who received macrolide-based multi-drug regimens. CRISPR-MAC assay detected MAC-cfDNA in MAC-PD with 97.6% (91.6 - 99.7%) sensitivity and 97.6% (91.5 - 99.7%) specificity overall. Serum MAC-cfDNA levels markedly decreased after MAC-directed treatment initiation in MAC-PD patients that demonstrated MAC culture conversion. This study provides preliminary evidence for the utility of a serum-based CRISPR-MAC assay to rapidly detect MAC infection and monitor their response to treatment.

Combined Application of Juniperus communis Essential Oil and Amikacin, Clarithromycin and Rifampicin against Mycobacterium avium and Mycobacterium intracellulare

The group of nontuberculous mycobacteria (NTM) includes about 200 mycobacteria that are widespread in the natural environment as free-living saprophytic bacteria, commensals or symbionts. NTM, also referred to as atypical mycobacteria, are mostly apathogenic; nowadays, they are increasingly important environmental opportunistic pathogens. This study continues the work of previous studies which investigated the individual and synergistic effect of different essential oils (EOs) on NTM. The aim was to investigate the effect of the interaction of the common juniper (Juniperus communis) EO and the antimicrobials, amikacin, clarithromycin and rifampicin, against Mycobacterium avium and M. intracellulare using the checkerboard synergy method in an enriched Middlebrook 7H9 broth. Morphological changes of treated NTM cells were observed with a transmission electron microscope. The most synergistic combinations were found at subinhibitory concentrations of the common juniper EO and rifampicin against both tested NTM and this EO and clarithromycin against M. avium. A slightly smaller number of synergistic effects on both NTM were found using a combination of this EO and amikacin. Combinations of clarithromycin and the common juniper EO showed no synergism against M. intracellulare. The exposure of both NTM to synergistic combinations of this EO and antimicrobials caused significant morphological changes in mycobacterial cells. Synergism with the combined use of EOs and antimicrobials allows the use of low effective concentrations via the sustained antimicrobial effect of the tested substances, but with potentially reduced toxicity.

Acute exacerbation of bronchiectasis secondary to Achromobacter xylosoxidans in a patient with Mycobacterium-Avium Intracellulare infection

Acute exacerbation of bronchiectasis secondary to Achromobacter xylosoxidans in a patient with Mycobacterium-Avium Intracellulare infection

Effectiveness of Rifabutin-Based Regimens in Treating Helicobacter pylori Infections.

Helicobacter pylorihas been reported as a health problem worldwide, affecting a sizable portion of people. Peptic ulcers, gastric cancer, and various extra gastric conditions are associated with this bacterium. The rampant overprescribing of antibiotics has led to the emergence of H. pylori strains resistant to multiple antibiotics, causing a decline in the effectiveness of current treatments. Recently, there has been growing interest in researching alternative treatment options for H. pylori infections that do not respond to initial therapy. Rifabutin, a rifamycin derivative initially designed for tuberculosis treatment and preventing Mycobacterium avium complex infection, has gained attention as a potential rescue medication. It has shown efficacy against H. pylori and the potential to eradicate the bacterium when combined with other antibiotics. This systematic review article focuses on using rifabutin-based regimens as a treatment option after initial treatments have failed. The authorsscreened literature published in the last five years, between 2017 and 2022, across various search engines and closely examined relevant studies following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. The search covered a variety of electronic databases and focused on H. pylori gastritis, rifabutin-based treatment plans, and in vivo investigations in healthy individuals. The comprehensive review provides convincing evidence that rifabutin-based regimens are effective rescue treatments for H. pylori infections. Multiple studies in various areas consistently demonstrated high eradication rates, ranging from 70% to 90%, when rifabutin-containing regimens were used. The analysis found that only a tiny percentage of H. pylori strains (1%) were resistant to rifabutin therapy, further supporting the viability of Rifabutin as an alternative when other antibiotics failed to eradicate H. pylori. The cost of Rifabutin is a significant factor that may limit its accessibility, particularly in resource-constrained settings where H. pylori infection is common.Moreover, the potential side effects of Rifabutin, such as hematological problems, rashes, and digestive issues, need to be considered. However, these side effects are typically manageable and can be reduced by combining Rifabutin with other antibiotics. In conclusion, this systematic review provides evidence supporting the effectiveness of regimens derived from Rifabutin in eliminating H. pylori infections after initial therapy failure. Due to the observation that Rifabutin effectively eradicates resistant H. pylori infections, it can be considered a suitable choice for rescue therapy. Rifabutin-containing regimens should be reserved as fourth- or later-line therapy options, considering economic factors, the risk of microbial resistance, potential side effects, and the availability of alternative medications. Future research should focus on optimizing rifabutin-based regimens and investigating combination therapies that have betterH. pylori eradication rates while also addressing the problem of resistant strains.

Ceftriaxone efficacy for Mycobacterium avium complex lung disease in the hollow fiber and translation to sustained sputum culture conversion in patients.

Only 35.6%-50.8% of patients with Mycobacterium avium complex (MAC) pulmonary disease achieve sustained sputum culture conversion (SSCC) on treatment with the azithromycin-ethambutol-rifabutin standard of care (SOC). We tested the efficacy of ceftriaxone, a β-lactam with a lung penetration ratio of 12.18-fold. We mimicked lung concentration-time profiles of seven ceftriaxone once-daily doses for 28 days in the hollow fiber system model of intracellular MAC (HFS- MAC). Monte Carlo experiments were used for dose selection.We also compared the once-daily ceftriaxone monotherapy to three-drug SOC against five MAC clinical isolates in HFS-MAC using γ (kill)-slopes. Results were translated to SSCC rates. Ceftriaxone killed 1.02-3.82 log10 cfu/mL in dose-response studies. Ceftriaxone 2G once-daily was identified as the optimal dose. Ceftriaxone killed all five strains below day 0 versus 2/5 for SOC. The median γ (95% confidence interval) was 0.49(0.47-0.52) log10 cfu/mL/day for ceftriaxone and 0.38(0.34-0.43) log10 cfu/mL/day for SOC. In patients, the SOC was predicted to achieve SSCC rates of 39.3%(36%-42%) at 6 months (similar to meta-analyses results). The SOC SSCC was 50% at 8.18(3.64-27.66) months versus 3.58(2.20-7.23) months for ceftriaxone. Thus, ceftriaxone shortened time-to-SSCC 2.35-fold compared to SOC. Ceftriaxone is a promising agent for creation of short-course chemotherapy.

Intracellular and in vivo activities of oxazolidinone drugs against Mycobacterium avium complex infection

The prevalence of Mycobacterium avium complex-pulmonary disease (MAC-PD) has become a growing concern worldwide, and current treatments involving macrolides (clarithromycin [CLR] or azithromycin), ethambutol, and rifampicin have limited success, highlighting the need for better therapeutic strategies. Recently, oxazolidinone drugs have been identified as novel anti-tuberculosis drugs effective against drug-resistant M. tuberculosis. However, the effects of these drugs against MAC are still controversial due to limited data. Here, we first evaluated the intracellular anti-MAC activities of two oxazolidinone drugs, linezolid (LZD) and delpazolid (DZD), against 10 macrolide-susceptible MAC strains and one macrolide-resistant M. avium strain in murine bone marrow-derived macrophages (BMDMs) and found that both drugs demonstrated similar potential. The synergistic efficacies with CLR were then determined in a chronic progressive MAC-PD murine model by initiating a 4-week treatment at 8 weeks post-infection. Upon assessment of bacterial burdens and inflamed lesions, oxazolidinone drugs exhibited no anti-MAC effect, and there was no significant difference in the synergistic effect of CLR between LZD and DZD. These findings suggest that oxazolidinone drugs inhibit intracellular bacterial growth, even against macrolide-resistant MAC, but their clinical application requires further consideration.

Phenotypic drug-susceptibility profiles and genetic analysis based on whole-genome sequencing of Mycobacterium avium complex isolates in Thailand.

Mycobacterium avium complex (MAC) infections are a significant clinical challenge. Determining drug-susceptibility profiles and the genetic basis of drug resistance is crucial for guiding effective treatment strategies. This study aimed to determine the drug-susceptibility profiles of MAC clinical isolates and to investigate the genetic basis conferring drug resistance using whole-genome sequencing (WGS) analysis. Drug-susceptibility profiles based on minimum inhibitory concentration (MIC) assays were determined for 38 MAC clinical isolates (12 Mycobacterium avium and 26 Mycobacterium intracellulare). Mutations associated with drug resistance were identified through genome analysis of these isolates, and their phylogenetic relationships were also examined. Drug resistance, based on MIC values, was most commonly observed for moxifloxacin (81.6%), followed by linezolid (78.9%), clarithromycin (44.7%) and amikacin (36.8%). We identified specific mutations associated with resistance to amikacin. These include the rrs mutation at C464T in amikacin intermediate-resistance M. avium, and two mutations at T250A and G1453T in amikacin non-susceptible M. intracellulare. Mutations in rrl at A2058G, A2059C and A2059G were potentially linked to clarithromycin resistance. MAC clinical isolates not susceptible to linezolid exhibited mutations in rplC at G237C and C459T, as well as two rplD mutations at G443A and A489G. GyrB substitution Thr521Ala (T521A) was identified in moxifloxacin non-susceptible isolates, which may contribute to this resistance. A phylogeny of our MAC isolates revealed high levels of genetic diversity. Our findings suggest that the standard treatment regimen for MAC infections using moxifloxacin, linezolid, clarithromycin and amikacin may be driving development of resistance, potentially due to specific mutations. The combination of phenotypic and genotypic susceptibility testing can be valuable in guiding the clinical use of drugs for the treatment of MAC infections.