Nontuberculous Mycobacteria in Portugal: Trends from the last decade

Incorporating direct molecular diagnostics in management algorithms for nontuberculous mycobacteria: Is it high time?

Nontuberculous mycobacteria (NTM) are a group of acid-fast mycobacteria other than Mycobacterium tuberculosis complex (MTBC) that cause pulmonary disease that is similar to the disease caused by MTBC. International guidelines for the diagnosis of pulmonary NTM disease are rigid and have remained unchanged for nearly 2 decades. In this opinion piece, we provide a new perspective on the traditional criteria by suggesting a diagnostic algorithm that incorporates direct molecular identification of NTM performed on raw sputum specimens (using Sanger or targeted deep sequencing approaches, among others) paired with traditional culture methods. Our approach ensures a more rapid diagnosis of pulmonary NTM disease, thus, facilitating timeous clinical diagnosis, and prompt treatment initiation, where indicated, and leverages recent advances in novel molecular techniques into routine NTM identification practice.

Species identification and drug susceptibility testing of non-tuberculous mycobacteria by Line Probe Assay in Lambaréné, Gabon-a cross-sectional study

BACKGROUND

Non-tuberculous mycobacteria (NTM) are a group of bacteria that cause rare lung infections and are increasingly recognized as causative agents of opportunistic and device-associated infections in humans. In Gabon, there is a lack of data on NTM species identification and drug susceptibility. The aim of this study was to identify the frequency of NTM species and their genotypic susceptibility pattern to commonly used antibiotics for NTM infections in Gabon.

METHODS

A cross-sectional study was conducted at the CERMEL TB laboratory from January 2020 to December 2022, NTM subspecies identification and drug susceptibility testing to macrolides and aminoglycosides were performed using the genotype NTM-DR kit.

RESULTS

The study found that out of 524 culture-positive specimens, 146 (28%) were NTM, with the predominant group being Mycobacterium avium complex (MAC) and Mycobacterium abscessus complex (MABC). All MAC isolates were fully susceptible to macrolides and aminoglycosides, while five MABC isolates carried mutations indicative of reduced susceptibility to macrolide and aminoglycoside drugs.

CONCLUSIONS

These findings suggest that clinicians may use macrolides and aminoglycosides to manage NTM infections caused by MAC, but further investigation is required to determine MABC drug susceptibility.

Serum proteomics analysis for differentiation among Mycobacterium tuberculosis infection categories

Inhalation of Mycobacterium tuberculosis (Mtb) bacilli can lead to a range of TB categories including early clearance (EC), latent TB infection (LTBI) and active TB (ATB). There are few biomarkers available to differentiate among these TB categories: effective new biomarkers are badly needed. Here, we analyzed the serum proteins from 26 ATB cases, 20 LTBI cases, 34 EC cases and 38 healthy controls (HC) using label-free LC-MS/MS. The results were analyzed using MaxQuant software and matched to three different bacterial proteomics databases, including Mtb, Mycobacterium spp. and normal lung flora. PCA of protein candidates using the three proteomics databases revealed 44.5% differentiation power to differentiate among four TB categories. There were 289 proteins that showed potential for distinguishing between each pair of groups among TB categories. There were 50 candidate protein markers specifically found in ATB and LTBI but not in HC and EC groups. Decision trees using the top five candidate biomarkers (A0A1A2RWZ9, A0A1A3FMY8, A0A1A3KIY2, A0A5C7MJH5 and A0A1X0XYR3) had 92.31% accuracy to differentiate among TB categories and the accuracy was increased to 100% when using 10 candidate biomarkers. Our study shows that proteins expressed from Mycobacterium spp. have the potential to be used to differentiate among TB categories.

Epidemiology of non-tuberculous mycobacterial diseases in Slovakia during the years 2016-2021

Nontuberculous mycobacteria (NTM) are opportunistic human pathogens found worldwide, primarily in the environment. They predominantly affect the lungs, especially in individuals with compromised immune systems. Recent studies suggest an increasing incidence of NTM disease; however, their actual clinical impact in Slovakia remains uncertain. In this study, we conducted a retrospective analysis using a representative collection of NTM cases in the country. We searched the national database for patients with positive NTM cultures between January 2016 and December 2021. A total of 1355 NTM-positive cultures were identified in Slovakia, with no significant increase observed during the study period. Among these, 358 cases (26.4%) were confirmed as NTM disease. The incidence of the disease was notably higher in individuals over 55 years old (p<0.0001). Moreover, women diagnosed with NTM disease exhibited a significantly higher average age than men (p=0.0005). The majority of NTM disease cases were attributed to Mycobacterium (M.) intracellulare (39.9%) and M. avium (38.5%). Geographically, the highest incidence of NTM disease was observed in the Bratislava region (10.69 per 100,000 population).

Microevolution of a Mycobacteroides abscessus subsp. bolletii strain in a clinical persistent infection

Mycobacteroides abscessus complex (MAB), a fast-growing nontuberculous mycobacterium, is emerging as a significant infectious disease threat, due to both intrinsic and acquired resistance mechanisms to antibiotics and disinfectants and the need for extensive and multidrug regimens for treatment. Despite the prolonged regimens, outcomes are poor and persistence cases have been reported. Here, we describe clinical, microbiologic and genomic features of a M. abscessus subsp. bolletii (M. bolletii) strain consecutively isolated from a patient within an eight-year infection period. From April 2014 to September 2021, the National Reference Laboratory for Mycobacteria received eight strains isolated from a male patient. Species identification, molecular resistance profile and phenotypic drug susceptibility were determined. Five of these isolates were recovered for further in-depth genomic analysis. Genomic analysis confirmed the multidrug resistant pattern of the strain and also other genetic changes associated with adaptation to environment and defence mechanisms. We highlight the identification of new mutations in locus MAB_1881c and in locus MAB_4099c (mps1 gene), already described as associated with macrolides resistance and morphotype switching, respectively. Additionally, we also observed the emergence and fixation of a mutation in locus MAB_0364c that appeared at a frequency of 36% for the 2014 isolate, 57% for the 2015 isolate and 100% for the 2017 and 2021 isolates, clearly illustrating a fixation process underlying a microevolution of the MAB strain within the patient. Altogether these results suggest that the observed genetic alterations are a reflection of the bacterial population's continuous adaptation and survival to the host environment during infection, contributing to persistence and treatment failure.

Antimicrobial Effect of Oxazolidinones and Its Synergistic Effect with Bedaquiline Against Mycobacterium abscessus Complex

Purpose

Unsatisfactory efficacies of currently recommended anti-Mycobacterium abscessus complex (MABC) treatment regimens have led to development of novel drugs to combat MABC infections. In this study, we evaluated in vitro antimicrobial activities of bedaquiline (BDQ) and four oxazolidinones against MABC isolates.

Methods

The resazurin microplate assay was performed to determine minimum inhibitory concentrations (MICs) of BDQ and four oxazolidinones, including tedizolid (TZD), sutezolid (SZD), delpazolid (DZD), and linezolid (LZD), against 65 MABC isolates. A checkerboard method was used to investigate efficacies of various antimicrobial drug combinations.

Results

BDQ MICs for MABC isolates ranged from <0.031 to 1 µg/mL, while MIC₅₀ and MIC₉₀ values were 0.125 µg/mL and 0.25 µg/mL, respectively. TZD MIC₅₀ and MIC₉₀ values for MABC isolates were 1 µg/mL and 4 µg/mL, respectively, which were fourfold lower than corresponding LZD values (P < 0.001). DZD MIC₉₀ values for MABC isolates was 8 µg/mL, which were 0.5-fold lower than corresponding LZD values (P < 0.01). MICs of BDQ, SZD, and LZD for M. abscessus subspecies massiliense isolates were significantly lower than corresponding MICs for M. abscessus subspecies abscessus isolates (P < 0.05). Notably, use of oxazolidinones (DZD, SZD, LZD, or TZD) with BDQ against MABC isolates led to reduction of the oxazolidinone median MIC range from 4 to 0.125 µg/mL to 1-0.031 µg/mL.

Conclusion

These results demonstrated excellent BDQ inhibitory activity against MABC isolates. TZD exhibited stronger antimicrobial efficacy against MABC isolates as compared to efficacies of DZD, SZD, and LZD. Importantly, MICs of oxazolidinones were markedly decreased when they were combined with BDQ, thus suggesting that combinations of BDQ and oxazolidinones may be effective treatments for MABC infections.