Treatment with a macrolide-containing regimen for Mycobacterium kansasii pulmonary disease

Treatment of the Less Common Nontuberculous Mycobacterial Pulmonary Disease

Nontuberculous mycobacterial pulmonary disease caused by the less common nontuberculous mycobacteria have distinct features depending on the species. Diagnostic evaluation follows the established criteria for all nontuberculous mycobacteria, but with certain qualifications given species-specific and regional differences in pathogenicity. Clinicians should first institute nonpharmacologic management and evaluate clinical, radiologic, and microbiologic factors in the decision regarding antimycobacterial therapy. Treatment is challenging, and evidence-based recommendations are limited for most species. Drug susceptibility testing is used to help with regimen selection; however, this approach is imperfect given the uncertain correlation between in vitro activity and clinical response for most drugs.

Treatment of non-tuberculosis mycobacteria skin infections

Non-tuberculosis mycobacteria (NTM) skin infections have become increasingly prevalent in recent years, presenting a unique challenge in clinical management. This review explored the complexities of NTM infections localized to the superficial tissues and provided valuable insights into the optimal therapeutic strategies. The antibiotic selection should base on NTM species and their susceptibility profiles. It is recommended to adopt a comprehensive approach that considers the unique characteristics of superficial tissues to improve treatment effectiveness and reduce the incidence of adverse reactions, infection recurrence, and treatment failure. Infection control measures, patient education, and close monitoring should complement the treatment strategies to achieve favorable outcomes in managing NTM skin infections. Further efforts are warranted to elucidate factors and mechanisms contributing to treatment resistance and relapse. Future research should focus on exploring novel treatment options, innovative drug development/delivery platforms, and precise methodologies for determining therapeutic duration. Longitudinal studies are also needed to assess the long-term safety profiles of the integrated approaches.

Repurposing β-Lactams for the Treatment of Mycobacterium kansasii Infections: An In Vitro Study

Mycobacterium kansasii (Mkn) causes tuberculosis-like lung infection in both immunocompetent and immunocompromised patients. Current standard therapy against Mkn infection is lengthy and difficult to adhere to. Although β-lactams are the most important class of antibiotics, representing 65% of the global antibiotic market, they have been traditionally dismissed for the treatment of mycobacterial infections, as they were considered inactive against mycobacteria. A renewed interest in β-lactams as antimycobacterial agents has shown their activity against several mycobacterial species, including M. tuberculosis, M. ulcerans or M. abscessus; however, information against Mkn is lacking. In this study, we determined the in vitro activity of several β-lactams against Mkn. A selection of 32 agents including all β-lactam chemical classes (penicillins, cephalosporins, carbapenems and monobactams) with three β-lactamase inhibitors (clavulanate, tazobactam and avibactam) were evaluated against 22 Mkn strains by MIC assays. Penicillins plus clavulanate and first- and third-generation cephalosporins were the most active β-lactams against Mkn. Combinatorial time-kill assays revealed favorable interactions of amoxicillin-clavulanate and cefadroxil with first-line Mkn treatment. Amoxicillin-clavulanate and cefadroxil are oral medications that are readily available, and well tolerated with an excellent safety and pharmacokinetic profile that could constitute a promising alternative option for Mkn therapy.

The Other Nontuberculous Mycobacteria: Clinical Aspects of Lung Disease Caused by Less Common Slowly Growing Nontuberculous Mycobacteria Species

Slowly growing nontuberculous mycobacteria (NTM) comprise a diverse group of environmental organisms, many of which are important human pathogens. The most common and well-known member of this group is Mycobacterium avium, the leading cause of nontuberculous mycobacterial pulmonary disease (NTM-PD) globally. This review focuses on the less common, but notable, species of slowly growing NTM with respect to lung disease. To prepare this article, literature searches were performed using each species name as the key word. Society guidelines were consulted, and relevant articles also were identified through the reference lists of key articles. The specific organisms highlighted include Mycobacterium kansasii, Mycobacterium xenopi, Mycobacterium malmoense, Mycobacterium simiae, and Mycobacterium szulgai. Although these organisms are closely related, they have distinct epidemiologic features and behavior as pathogens. Therefore, the diagnosis and management of NTM-PD require a nuanced approach that takes into consideration the unique characteristics of each species. There is limited evidence to inform the optimal treatment of NTM-PD. Antimicrobial therapy is often challenging because of the presence of drug resistance and few antibiotic options. Regimen selection should generally be guided by drug susceptibility testing, although the correlation between clinical outcomes and in vitro susceptibility thresholds has not been defined for most species.

Isolation and Antimicrobial Susceptibility of Nontuberculous Mycobacteria in a Tertiary Hospital in Korea, 2016 to 2020

BACKGROUND

There is a global increase in isolation of nontuberculous mycobacteria (NTM). The aim of the study was to analyze longitudinal trends of NTM identification and pattern of antimicrobial susceptibility testing.

METHODS

NTM recovery rates, distribution of NTM species identification, and antimicrobial susceptibility pattern of NTM at Pusan National University Yangsan Hospital between January 2016 and December 2020 were retrospectively analyzed.

RESULTS

A total of 52,456 specimens from 21,264 patients were submitted for mycobacterial culture, of which 2,521 from 1,410 patients were NTM positive over five years (January 2016 to December 2020). NTM isolation showed an increasing trend from 2016 to 2020 (p<0.001, test for trend) mainly caused by Mycobacterium avium complex. The vast majority of M. avium complex were susceptible to key agents clarithromycin and amikacin. For Mycobacterium kansasii, resistance to rifampin and clarithromycin is rare. Amikacin was the most effective drug against Mycobacterium abscessus subspecies abscessus and Mycobacterium subspecies massiliense. Most of M. subspecies massiliense were susceptible to clarithromycin, while the majority of M. abscessus subspecies abscessus were resistant to clarithromycin (p<0.001).

CONCLUSION

There was an increasing trend of NTM isolation in our hospital. Resistance to key drugs was uncommon for most NTM species except for M. abscessus subspecies abscessus against clarithromycin.

Atypical mycobacterial infections - management and when to treat

PURPOSE OF REVIEW

Infections caused by nontuberculous mycobacteria (NTM) are increasing for several reasons, including diagnostic advances, increased awareness and a larger at-risk population. NTM pulmonary disease is surpassing tuberculosis (TB) in some low incidence areas. This review summarizes the latest literature and guidelines and aims to be a concise source outlining treatment and management of NTM lung infections, integrating established treatment paradigms with novel pharmacological interventions.

RECENT FINDINGS

Recent additions to NTM treatment are inhaled liposomal amikacin and the anti-TB drug bedaquiline. Several other new or repurposed treatments are being explored in vitro, in animal models and in clinical trials, including novel beta-lactamase inhibitor/lactam combinations, dual-lactam combinations, efflux pump inhibitors, novel antimicrobials, inhaled clofazimine suspension and bacteriophages.

SUMMARY

Patients with NTM pulmonary disease are mainly female and older with significant delay between diagnosis and treatment being common. Treatment varies according to causative organism, drug susceptibilities, radiological type and disease severity. Underlying chronic conditions, drug intolerances and interactions require careful consideration. In all cases, at least three drugs should be used to minimize acquisition of drug resistance, and all patients should receive a minimum of 12 months of treatment. Expert advice should be taken. NTM treatment is longer than TB treatment, more likely to fail and more likely to cause toxicity. The relatively small numbers of patients affected by each NTM species has limited research. Novel treatments hold promise; nevertheless, it is likely that new solutions for NTM management will stem from the TB pipeline for the foreseeable future.

Treatment of pulmonary disease caused by Mycobacterium kansasii

As a cause of lung disease (LD), Mycobacterium kansasii is regarded as a highly virulent species among nontuberculous mycobacteria (NTM). Both the frequency of M. kansasii isolates and global prevalence of M. kansasii-LD have increased gradually over recent decades. Treatment of M. kansasii-LD is recommended because of the disease's poor prognosis and fatal outcome. The decision on the optimal time point for treatment initiation should be based on both the benefits and risks posed by multiple antimicrobial agents. For treatment-naïve patients with M. kansasii-LD, rifampin-containing multiple antimicrobial regimens for ≥12 months after culture negative conversion are effective. However, some challenges remain, such as determining the precise length of treatment duration as well as addressing intolerable adverse effects, the uncertain effectiveness of isoniazid and ethambutol in treatment, the uncertain correlation between in vitro drug susceptibility testing and clinical outcomes, and the increasing prevalence of clarithromycin-resistant M. kansasii isolates. Short-course and effective therapies must be developed. New candidate drugs, such as tedizoid and clofazimine, exhibit excellent antimycobacterial activity against M. kansasii in vitro, but in vivo studies of their clinical applications are lacking. This paper reviews the treatment, outcomes and future directions in patients with M. kansasii-LD.

B Cell-Based Vaccine Transduced With ESAT6-Expressing Vaccinia Virus and Presenting α-Galactosylceramide Is a Novel Vaccine Candidate Against ESAT6-Expressing Mycobacterial Diseases

Early secretory antigenic target-6 (ESAT6) is a potent immunogenic antigen expressed in Mycobacterium tuberculosis as well as in some non-tuberculous mycobacteria (NTM), such as M. kansasii. M. kansasii is one of the most clinically relevant species of NTM that causes mycobacterial lung disease, which is clinically indistinguishable from tuberculosis. In the current study, we designed a novel cell-based vaccine using B cells that were transduced with vaccinia virus expressing ESAT6 (vacESAT6), and presenting α-galactosylceramide (αGC), a ligand of invariant NKT cells. We found that B cells loaded with αGC had increased levels of CD80 and CD86 after in vitro stimulation with NKT cells. Immunization of mice with B/αGC/vacESAT6 induced CD4⁺ T cells producing TNF-α and IFN-γ in response to heat-killed M. tuberculosis. Immunization of mice with B/αGC/vacESAT6 ameliorated severe lung inflammation caused by M. kansasii infection. We also confirmed that immunization with B/αGC/vacESAT6 reduced M. kansasii bacterial burden in the lungs. In addition, therapeutic administration of B/αGC/vacESAT6 increased IFN-γ⁺ CD4⁺ T cells and inhibited the progression of lung pathology caused by M. kansasii infection. Thus, B/αGC/vacESAT6 could be a potent vaccine candidate for the prevention and treatment of ESAT6-expressing mycobacterial infection caused by M. kansasii.

Managing antibiotic resistance in nontuberculous mycobacterial pulmonary disease: challenges and new approaches

Introduction: The incidence and prevalence rates of nontuberculous mycobacterial (NTM) pulmonary disease have been continuously increasing worldwide. However, the rate of successful treatment of this disease greatly needs improving, particularly when intrinsic (natural) drug resistance and acquired drug resistance in NTM pulmonary disease are associated with poor outcomes for patients. Areas covered: This review covers the major pathogens that cause NTM pulmonary disease caused by Mycobacterium avium complex, Mycobacterium abscessus, and Mycobacterium kansasii; the key drugs and recommended regimens used in the treatment of NTM pulmonary disease; the factors that contribute to resistance to the key drugs, including genetic factors and monotherapy; and the treatment strategies, including revised antibiotic regimens and surgery, that can be used to treat drug-resistant NTM pulmonary disease. Expert opinion: To avoid and overcome drug resistance in NTM pulmonary disease, the appropriate guideline-based treatments are essential, and clinical studies to evaluate new or repurposed drugs are urgently needed.