Nontuberculous Mycobacteria Species Research Articles

Rational Exploration of 2,4-Diaminopyrimidines as DHFR Inhibitors Active against Mycobacterium abscessus and Mycobacterium avium, Two Emerging Human Pathogens.

Nontuberculous mycobacteria (NTM) are emerging human pathogens linked to severe pulmonary diseases. Current treatments involve the prolonged use of multiple drugs and are often ineffective. Bacterial dihydrofolate reductase (DHFR) is a key enzyme targeted by antibiotics in Gram-negative bacterial infections. However, existing DHFR inhibitors designed for Gram-negative bacteria often fail against mycobacterial DHFRs. Here, we detail the rational design of NTM DHFR inhibitors based on P218, a malarial DHFR inhibitor. We identified compound 8, a 2,4-diaminopyrimidine exhibiting improved pharmacological properties and activity against purified DHFR, and whole cell cultures of two predominant NTM species: Mycobacterium avium and Mycobacterium abscessus. This study underscores the potential of compound 8 as a promising candidate for the in vivo validation of DHFR as an effective treatment against NTM infections.

Challenges in diagnosing bovine tuberculosis through surveillance and characterization of Mycobacterium species in slaughtered cattle in Kolkata

BackgroundTuberculosis in cattle is caused by Mycobacterium tuberculosis complex (MTBC) species. Apart from MTBC, different Nontuberculous Mycobacteria (NTM) species have also been isolated from cattle. The presence of NTM infection in bovines makes the diagnosis of bovine tuberculosis (bTB) a cumbersome task. Therefore, a cross sectional study was conducted to isolate and characterize different Mycobacterium spp. from a slaughterhouse situated in Kolkata, a city in the eastern part of India.ResultsOut of 258 morbid samples, 98 isolates were found to be positive for bacterial growth, and 35% (n = 34) were positive for Mycobacterium. 94% of Mycobacterial cultural isolates were NTM (n = 32), and the rest (n = 2) were found to be MTBC. Species-level identification of the isolates by hsp65 sequencing revealed that out of 32 isolates, 24 were M. fortuitum, three were M. abscessus, two each were M. chelonae and M. parascrofulaceum, and one was M. novocastrense. A phylogenetic tree with partial hsp65 gene sequences was also constructed to determine the relatedness of the unknown isolates to the reference strains.ConclusionBoth NTM species and MTBCs were identified from TB-like lesions in cattle that were slaughtered at the Kolkata abattoir. This discovery may indicate that NTM contributes to the development of lesions in cattle. Also, we recommend implication of more specific diagnostic tests for bTB.

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.

Genomic Epidemiology of Extrapulmonary Nontuberculous Mycobacteria Isolates at Emerging Infections Program Sites - United States, 2019-2020.

Nontuberculous mycobacteria (NTM) cause pulmonary and extrapulmonary infections. Although isolation of NTM from clinical specimens has increased nationally, few studies delineated the molecular characteristics of extrapulmonary NTM. Extrapulmonary isolates were collected by four Emerging Infections Program sites from October 2019 to March 2020 and underwent laboratory characterization, including matrix-assisted laser desorption ionization-time of flight mass spectrometry, Sanger DNA sequencing, and whole genome sequencing. Bioinformatics analyses were employed to identify species, sequence types (STs), antimicrobial resistance (AR), and virulence genes; isolates were further characterized by phylogenetic analyses. Among 45 isolates, the predominant species were Mycobacterium avium (n=20, 44%), Mycobacterium chelonae (n=7, 16%), and Mycobacterium fortuitum (n=6, 13%). The collection represented 31 STs across 10 species; the most common ST was ST11 (M. avium, n=7). Mycobacterium fortuitum and Mycobacterium abscessus isolates harbored multiple genes conferring resistance to aminoglycosides, beta-lactams, and macrolides. No known AR mutations were detected in rpoB, 16S, or 23S rRNAs. Slow-growing NTM species harbored multiple virulence genes including type-VII secretion components, adhesion factors, and phospholipase C. Continued active laboratory- and population-based surveillance will further inform the prevalence of NTM species and STs, monitor emerging clones, and allow AR characterization.

Managing Complicated Nontuberculous Mycobacteria Infections in Plastic Surgery.

Nontuberculous mycobacteria (NTM) infections after cosmetic surgery have become an increasing concern. These infections are often initially misdiagnosed and treated with standard antibiotic regimens, which fail to resolve the underlying infection, leading to prolonged patient suffering. In this case study, we describe a chronic wound infection caused by Mycobacterium abscessus subsp. bolletii after a muscle-repair abdominoplasty. This case illustrates the diagnostic and therapeutic challenges plastic surgeons face in successfully treating such infections. Initial obstacles included the isolation of co-contaminating bacteria that masked the NTM infection, the use of antibiotics ineffective against the specific NTM species, and the failure to identify the infection source. In this instance, contaminated skin marker ink used to mark the rectus muscle, combined with a nonabsorbable (permanent) suture for muscle repair, led to the development of a biofilm that acted as a persistent reservoir for the infection, resistant to antibiotic treatments. Complete resolution was achieved only after evaluation by a plastic surgeon experienced in treating NTM infections and the subsequent removal of the permanent suture. The delayed suture removal contributed to a 15-month recovery period. This case underscores the importance of early recognition of NTM infections after cosmetic procedures. By sharing this case, we aim to raise awareness of NTM infections and help prevent future cases of misdiagnosis and prolonged antibiotic treatments. Key points regarding the diagnosis, sources of infection, and treatment options for NTM infections are highlighted in this article using "text boxes" to emphasize the most important information and provide concise summaries of critical insights.

The Intriguing Pattern of Nontuberculous Mycobacteria in Bulgaria and Description of Mycobacterium bulgaricum sp. nov.

We investigated the rise of nontuberculous mycobacteria (NTM) infections in Bulgaria, focusing on species identification and distribution from 2018 to 2022. Utilizing advanced diagnostic tools, including the Hain Mycobacterium CM/AS method, Myco-biochip assay, and whole-genome sequencing, the study identifies and characterizes a diverse range of Mycobacterium species from clinical samples. While M. avium, M. gordonae, M. fortuitum, and M. chelonae were dominating, a number of rare species were also found. They include such species as M. marseillense and M. celatum. Moreover, the noticeable prevalence of M. terrae complex species missed by conventional testing was observed. We identified a rare species, highly homologous to previously described strains from Japan; based on genome-genome distance data, we propose its reannotation as a new species. Further, a novel species was identified, which is significantly distinct from its closest neighbor, M. iranicum, with ANI = 87.18%. Based on the SeqCode procedure, we propose to name this new species Mycobacterium bulgaricum sp. nov. Dynamic changes in NTM species prevalence in Bulgaria observed from 2011 to 2022 highlight the emergence of new species and variations tied to environmental and demographic factors. This underscores the importance of accurate species identification and genotyping for understanding NTM epidemiology, informing public health strategies, and enhancing diagnostic accuracy and treatment protocols.

Distribution of nontuberculous mycobacteria in dental unit waterlines: A potential health hazard in the dental office

BackgroundIt is essential to control the microbiology of dental unit water lines (DUWs) to prevent the spread of nontuberculous mycobacteria (NTM) and associated oral diseases. Therefore, the objective of this study was to quantify the presence of NTM in the water of 112 DUWs from dental centers and 57 DUWs from individual dental offices in Tehran, Iran. MethodsA total of 169 water samples were collected from DUWs. After filtration through a 0.45 μm membrane, the samples were decontaminated with 0.005 % cetylpyridinium chloride and then cultured on two Lowenstein-Jensen media, incubated at 25 °C and 37 °C for 8 weeks. Positive cultures for mycobacteria were analyzed using phenotypic tests, and the NTM species were identified through 16S rDNA, rpoB, and hsp65 genes analysis. Drug resistance was also assessed. ResultsOf the total isolates, 38 (34.5 %) were classified as slow-growing mycobacteria (SGM), while 72 (65.5 %) were categorized as rapid-growing mycobacteria (RGM). NTM isolates were identified using molecular tests, including M. chelonae, M. abscessus, M. lentiflavum, M. mucogenicum, M. fortuitum, M. kansasii, M. simiae, M. gordonae, M. conceptionense, M. phocaicum, M. porcinum, and M. aurum. The NTM counts ranged from 50 to >500 CFU/500 mL across these 188 samples, with a median of 350 CFU/500 mL. Additionally, we reported two cases of intraoral infection caused by M. abscessus and M. chelonae, where the source of infection was traced to NTM-contaminated DUWs. ConclusionsThe study found that most DUWs contained water contaminated with NTM, posing a potential health risk to humans. This research underscores the necessity of stringent quality control and certification of DUW water, with particular emphasis on ensuring the absence of NTM.

Increasing trends of non-tuberculous mycobacteria clinical isolates in Guangzhou, China

Non-tuberculous mycobacteria (NTM) are one of major public health concern. The current study aimed to find the prevalence trends of NTM in Guangzhou, China from January 2018 to December 2023. A total of 26,716 positive mycobacterial cultures were collected. Thirty-six specimens with incomplete personal information were excluded. The remaining 26,680 specimens were identified using a gene chip method. 16,709 isolates were Mycobacterium tuberculosis (MTB) (62.63 %), and 9,971 were NTM (37.37 %). 43.43 % (4,330/9,971) of NTM isolates were male, and 56.57 % (5,641/9,971) were female (χ2 = 24.36, P < 0.05), a male to female ratio of approximately 1:1.30. Infections in individuals with aged 40 years and above was higher (77.63 %) than below 40 years (22.37 %) (χ2 = 4.94, P = 0.026). The annual NTM isolation rates from 2018 to 2023 were 32.03 %, 34.00 %, 36.27 %, 38.58 %, 38.99 %, and 43.24 %, respectively, showing an increasing trend (χ2 for trend = 0.097, P < 0.05) (R = 0.097, P < 0.05). Out of 9,971 NTM isolates, 8,881 cases include only five common NTM species (MAC, M. abscessus/M. chelonae, M. kansasii, M. fortuitum, and M. gordonae). The overall NTM isolation rate was 37.37 %. The NTM isolation rate was significantly higher than the national average, showing an increasing trend over the last six years.

Evaluating the ability of non-tuberculous mycobacteria to induce non-specific reactions in bovine tuberculosis diagnostic tests in guinea pigs and cattle

Limitations in diagnostic test performance are one of the major challenges hampering the eradication of bovine tuberculosis (bTB). Non-tuberculous mycobacteria (NTM) are considered one of the main causes of non-specific reactions in the intradermal tuberculin test, the most widely used bTB diagnostic test. To determine the role of NTMs in bTB misdiagnosis in Spain, an experimental study including the NTM species most commonly found in bTB-positive animals from bTB-free farms in the country (M. avium subsp. avium (Maa), “Mycobacterium avium subsp. hominissuis” (Mah), M. bourgelatii, M. intermedium, M. kansasii and M. nonchromogenicum) was carried out on guinea pigs and cattle. First, guinea pigs were sensitized with the selected NTMs, and six weeks post-sensitization four antigen mixtures (bovine-PPD, avian-PPD, P22 and ESAT6-CFP10) were inoculated intradermally and their effect was measured 24- and 48-h post-inoculation. Larger erythematous reactions were observed in guinea pigs sensitized with Mah, M. kansasii, and Maa, with significant differences in the reactions measured at the bovine-PPD inoculation site for the two first bacteria compared with other NTMs. The sensitization process was repeated in cattle, and five months post-sensitization the same antigen mixtures were inoculated in the cervical region and responses were measured at 48- and 72-h post-inoculation. A significantly higher increase in the skinfold thickness measured at the bovine-PPD inoculation site was observed in calves sensitized with Mah, Maa, M. intermedium and M. kansasii. These results demonstrate that certain NTM species may play a more significant role in bTB diagnostic interferences and show that results obtained in guinea pig and bovine models do not always coincide.

Rapid lateral flow test for Mycobacterium tuberculosis complex and non-tuberculous mycobacteria differentiation

The diagnosis of mycobacterial infections, including both the Mycobacterium tuberculosis complex (MTBC) and non-tuberculous mycobacteria (NTM), poses a significant global medical challenge. This study proposes a novel approach using immunochromatographic (IC) strip tests for the simultaneous detection of MTBC and NTM. Traditional methods for identifying mycobacteria, such as culture techniques, are hindered by delays in distinguishing between MTBC and NTM, which can affect patient care and disease control. Molecular methods, while sensitive, are resource-intensive and unable to differentiate between live and dead bacteria. In this research, we developed unique monoclonal antibodies (mAbs) against Ag85B, a mycobacterial secretory protein, and successfully implemented IC strip tests named 8B and 9B. These strips demonstrated high concordance rates with conventional methods for detecting MTBC, with positivity rates of 93.9% and 85.9%, respectively. For NTM detection, the IC strip tests achieved a 63.2% detection rate compared to culture methods, considering variations in growth rates among different NTM species. Furthermore, this study highlights a significant finding regarding the potential of MPT64 and Ag85B proteins as markers for MTBC detection. In conclusion, our breakthrough method enables rapid and accurate detection of both MTBC and NTM bacteria within the BACTEC MGIT system. This approach represents a valuable tool in clinical settings for distinguishing between MTBC and NTM infections, thereby enhancing the management and control of mycobacterial diseases.Key points• Panel of mAbs for differentiating MTB versus NTM• IC strips for diagnosing MTBC and NTM after the BACTEC MGIT• Combined detection of MTP64 and Ag85B enhances diagnostic accuracy

Development of the novel gene chip and restriction fragment length polymorphism (RFLP) methods for rapid detection of Mycobacterium tuberculosis complex in broth culture

BackgroundTuberculosis (TB) is a major global public health issue. Prompt and accurate TB diagnosis is crucial for starting appropriate treatments and preventing the disease's spread. Current diagnostic techniques are either slow or expensive. This study aimed to create and evaluate a new, fast, highly reliable, and cost-effective TB detection method using a gene chip and Restriction Fragment Length Polymorphism (RFLP) analysis on Mycobacteria Growth Indicator Tubes (MGIT) specimens. MethodsWe assessed the effectiveness of a novel gene chip and RFLP methods targeting the 16S rRNA gene of Mycobacterium tuberculosis in 2000 MGIT culture-positive specimens. RFLP analysis identified the AfeI restriction site within the M. tuberculosis complex (MTBC) genome. Discrepancies were investigated through extensive sequencing and Cobas TaqMan PCR analysis, along with reviewing patient profiles. ResultsBoth methods showed high efficacy in detecting MTBC in broth cultures, with the gene chip method achieving a sensitivity of 99.27 %, specificity of 98.35 %, and the RFLP method showing a sensitivity of 98.18 %, specificity of 99.31 %. False negatives in two isolates were due to a mutation in the AfeI site. Additionally, five cases showed MTBC presence when nontuberculous Mycobacterium species grew in cultures. ConclusionOur novel gene chip and RFLP methods are effective for rapid highly-reliable and cost-effective M. tuberculosis detection in MGIT specimens. Both gene chip and RFLP methods are suitable for resource-limited settings, offering an economical advantage. These methods have significant potential to improve clinical TB diagnosis.

The Drug Susceptibility of Non-Tuberculous Mycobacteria (NTM) in a Referral Hospital in Rome from 2018 to 2023.

Background: The treatment of non-tuberculous mycobacterial (NTM) infections is challenging because of the difficulty in obtaining phenotypic (pDST) and/or molecular (mDST) drug susceptibility testing and the need of a multi-drug regimen. Objectives: The objective was to describe the in vitro susceptibility patterns of various NTM species through an analysis of susceptibility results obtained on isolates collected between 2018 and 2023. Methods: Species identification and mutations in rrs or rrl genes (mDST) were identified by a line probe assay, while the pDST was performed by broth microdilution and interpreted according to CLSI criteria. Results: We analysed 337 isolates of NTM belonging to 15 species/subspecies. The Mycobacterium avium complex (MAC) was the most common (62%); other species identified included M. gordonae (11%), M. kansasii (5%), the M. abscessus complex (8%), M. chelonae (6%), and M. fortuitum (2%). The results of pDST (claritromycin and amikacin) and mDST (rrl and rrs genes) on 66 NTM strains showed that while wild-type rrl and rrs occurred in 86.3% and 94% strains, respectively, the pDST showed 88% sensitivity for clarithromycin and 57.5% for amikacin. The main incongruity was observed for macrolides. Conclusions: Most NTM are likely to be susceptible to macrolides and aminoglycosides. The molecular identification of resistant genotypes is accurate and strongly recommended for optimal patient management.

Source-to-tap investigation of the occurrence of nontuberculous mycobacteria in a full-scale chloraminated drinking water system.

Nontuberculous mycobacteria (NTM) in drinking water are a significant public health concern. However, an incomplete understanding of the factors that influence the occurrence of NTM in drinking water limits our ability to characterize risk and prevent infection. This study sought to evaluate the influence of season and water treatment, distribution, and stagnation on NTM in drinking water. Samples were collected source-to-tap in a full-scale, chloraminated drinking water system approximately monthly from December 2019 to November 2020. NTM were characterized using culture-dependent (plate culture with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry [MALDI-TOF MS] isolate analysis) and culture-independent methods (quantitative PCR and genome-resolved metagenomics). Sampling locations included source waters, three locations within the treatment plant, and five buildings receiving water from the distribution system. Building plumbing samples consisted of first draw, 5-min flush, and full flush cold-water samples. As the study took place during the COVID-19 pandemic, the influence of reduced water usage in three of the five buildings was also investigated. The highest NTM densities source-to-tap were found in the summer first draw building water samples (107 gene copies/L), which also had the lowest monochloramine concentrations. Flushing was found to be effective for reducing NTM and restoring disinfectant residuals, though flush times necessary to improve water quality varied by building. Clinically relevant NTM species, including Mycobacterium avium, were recovered via plate culture, with increased occurrence observed in buildings with higher water age. Four of five NTM metagenome-assembled genomes were identified to the species level and matched identified isolates.IMPORTANCENTM infections are increasing in prevalence, difficult to treat, and associated with high morbidity and mortality rates. Our lack of understanding of the factors that influence NTM occurrence in drinking water limits our ability to prevent infections, accurately characterize risk, and focus remediation efforts. In this study, we comprehensively evaluated NTM in a full-scale drinking water system, showing that various steps in treatment and distribution influence NTM presence. Stagnant building water contained the highest NTM densities source-to-tap and was associated with low disinfectant residuals. We illustrated the differences in NTM detection and characterization obtained from culture-based and culture-independent methods, highlighting the complementarity between these approaches. We demonstrated that focusing NTM mitigation efforts in building plumbing systems, which have the highest NTM densities source-to-tap, has potential for immediate positive effects. We also identified steps during treatment that increase NTM levels, which provides beneficial information for utilities seeking to reduce NTM in finished water.

Immunogenicity and vaccine potential of clinical isolate Mycobacterium kansasii strain against Mycobacterium tuberculosis infection.

Mycobacterium kansasii is a bacterium included in non-tuberculous mycobacteria (NTM) that can cause lung disease. It shares a significant number of antigens with Mycobacterium tuberculosis (Mtb), suggesting that it has the potential to be used as a tuberculosis (TB) vaccine. Therefore, we subcutaneously vaccinated mice with reference strain, M. kansasii-ATCC12478 [M. kansasii-American Type Culture Collection (ATCC)], and clinically isolated strain, M. kansasii-SM-1 to evaluate potential as a TB vaccine by comparing with bacille Calmette-Guerin (BCG) vaccine. Ten weeks after vaccination, we evaluated immunogenicity of M. kansasii-ATCC and M. kansasii-SM-1, and M. kansasii-SM-1 immunization induces potent Mtb antigen-specific IFN-γ-producing CD4+ T cells than M. kansasii-ATCC. Upon Mtb infection, M. kansasii-SM-1 provided better protection than M. kansasii-ATCC, which was comparable to the efficacy of BCG. These results showed that the clinical strain M. kansasii-SM-1, which exhibits an enhanced Mtb antigen-specific Th1 response, shows greater vaccine efficacy compared to M. kansasii-ATCC. In this study, we demonstrated that vaccine efficacy can vary depending on the strain of M. kansasii and that its efficacy can be comparable to BCG. This suggests that M. kansasii has the potential to be a live TB vaccine candidate.IMPORTANCEMycobacterium kansasii, a non-tuberculous mycobacteria (NTM) species causing lung disease, shares key antigens with Mycobacterium tuberculosis (Mtb), indicating its potential for TB vaccine development. Subcutaneous vaccination of mice with M. kansasii strains reference strain M. kansasii-ATCC12478 [(M. kansasii-American Type Culture Collection (ATCC)] and clinically isolated strain M. kansasii-SM-1 revealed differences in immunogenicity. M. kansasii-SM-1 induced a robust Mtb antigen-specific IFN-γ-producing CD4+ T cell response compared to M. kansasii-ATCC. Additionally, M. kansasii-SM-1 conferred better protection against Mtb infection than M. kansasii-ATCC, which is comparable to bacille Calmette-Guerin (BCG). These findings underscore the variable vaccine efficacy among M. kansasii strains, with M. kansasii-SM-1 exhibiting promising potential as a live TB vaccine candidate, suggesting its comparative effectiveness to BCG.

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.

Prevalence and predictors of NTM in presumed/confirmed drug-resistant TB.

Non-tuberculous mycobacteria (NTM) are increasingly isolated in individuals with presumed/confirmed pulmonary TB. We aimed to estimate the prevalence and species distribution of NTM among presumed/confirmed drug-resistant TB (DR-TB) individuals and determine NTM isolation predictors. Sputum samples collected for DR-TB diagnosis and follow-up from 2012 to 2021 in Ghana were retrospectively analysed. Samples were subjected to sputum smear microscopy (SSM) and mycobacterial culture. The MPT64 assay was performed on positive cultures to distinguish between Mycobacterium tuberculosis complex MTBc and NTM. NTM isolates were re-cultured for species identification using GenoType® Mycobacterium CM/AS line-probe assay, polymerase chain reaction, and Sanger sequencing targeting 16S rRNA and rpoB genes. MTBc isolates identified by GenoType underwent spoligotyping. A logistic regression model was used to identify the predictors of NTM isolation. Of the 2,492 samples, 839 (33.7%) tested culture-positive for mycobacteria, with 257 (30.6%) presumed to be NTM. Of these, 53 (23.6%) were identified at the species level, with a predominance of M. intracellulare (66.0%). MPT64 testing missed 18 (3%) MTBc isolates. Logistic regression showed increased odds of NTM isolation in follow-up samples (aOR 2.41, 95% CI 1.46-3.99). NTM species were isolated from 46 patients, with four classified as NTM pulmonary disease. Enhancing our understanding of local NTM epidemiology and improving local diagnostic capabilities can optimise patient management strategies and outcomes.

Prevalence and antimicrobial susceptibility pattern of Mycobacterium abscessus complex isolates in Chongqing, Southwest China

ObjectivesTo investigate the prevalence of Mycobacterium abscessus complex (MABC), drug resistance characteristics, and the relationship between clarithromycin (CLA) susceptibility and MABC genotype in Chongqing, China. MethodsA total of 434 NTM patient isolates were collected between October 2018 and October 2019. Isolates confirmed to be non-tuberculous mycobacteria (NTM) were tested for minimal inhibitory concentrations of antimicrobial agents. In addition, rrl and erm(41) gene sequences were used to analyze the acquired macrolide resistance and inducible macrolide resistance. ResultsOverall, 17 different NTM species were detected, of which M. abscessus (22.6 %, 91/403) was most prevalent. Amikacin, CLA, azithromycin and cefoxitin exhibited potent activities against MABC organisms, but no significant differences were observed in drug resistance rates between M. abscessus and M. massiliense (P > 0.05). On day 3 of culture, the acquired resistance rate against CLA was 7.4 % (9/121). Of 41 MABC isolates with inducible CLA resistant, 95.1 % (39/41) isolates belonged to the erm(41) T28 sequevar, while the remaining 4.9 % (2/41) possessed the M. massiliense genotype. All erm(41) C28 sequevar isolates were sensitive to CLA on day3 and day 14 of culture. Meanwhile, of the 5 erm(41) T28 isolates with acquired resistance, all possessed rrl 2058/2059 mutations, including 3 isolates with A2058C mutation and 2 isolates with A2059G mutation. While 2 of the 4 M. massiliense isolates with acquired resistance possessed the A2059G mutation, and one isolate possessed the A2058G mutation. ConclusionErm(41) and rrl gene could serve as useful markers for predicting macrolide susceptibility of MABC complex isolates.

A Rapid PCR-Based Diagnostic Method for Skin Infection with Mycobacterium marinum.

The increasing incidence of chronic skin infections caused by Mycobacterium marinum, coupled with the time-consuming and low detection rates nature of traditional culture and histological-based diagnostic methods, underscores the need for an expedited approach. The study aims to develop a rapid and efficient method for detecting M. marinum with PCR technology. We designed four pairs of primers based on DNA sequences from GeneBank and prior studies, we utilized both PCR and Real-time PCR to identify M. marinum. Specificity and sensitivity assessments were conducted in vitro by DNAs extracted from M. marinum and other bacterial or fungal cultures. Further validation was performed through the implementation of a mouse skin infection model to optimize and confirm the efficacy of the detection method in both fresh and paraffin-embedded skin tissues. The same PCR testing system was further confirmed with paraffin-embedded skin tissues samples from patients as well. The results of the study indicate promising outcomes for the four-pair primers system. It demonstrated 100% sensitivity in detecting M. marinum from purified cultures, including typical strains and nine clinical isolates, while achieving a specificity of 100%. This specificity was evidenced by the absence of PCR products from 12 bacterial species, 12 fungi species, and six other non-tuberculous mycobacterium (NTM) species. In the animal model, the PCR assay exhibited high detection efficacy for both infected fresh tissues and paraffin-embedded tissues, with a slight superiority observed in fresh tissues. However, the PCR assay exhibited high detection efficacy for clinical paraffin-embedded tissues. These findings collectively underscore the robust detection capabilities of our four-pair primers in both in vitro and in vivo settings. A sensitive and highly specific rapid detection system has been successfully developed that can be used to detect M. marinum in both infected fresh tissues and paraffin-embedded tissues.

Growing from common ground: nontuberculous mycobacteria and bronchiectasis.

Bronchiectasis and nontuberculous mycobacteria (NTM) are intricately intertwined, with NTM capable of being both a cause and consequence of bronchiectatic disease. This narrative review focuses on the common ground of bronchiectasis and NTM pulmonary disease (NTM-PD) in terms of diagnostic approach, underlying risk factors and treatment strategies. NTM-PD diagnosis relies on a combination of clinical, radiological and microbiological criteria. Although their epidemiology is complicated by detection and reporting biases, the prevalence and pathogenicity of NTM species vary geographically, with Mycobacterium avium complex and Mycobacterium abscessus subspecies most frequently isolated in bronchiectasis-associated NTM-PD. Diagnosis of nodular bronchiectatic NTM-PD should prompt investigation of host factors, including disorders of mucociliary clearance, connective tissue diseases and immunodeficiencies, either genetic or acquired. Treatment of NTM-PD in bronchiectasis involves a multidisciplinary approach and considers the (sub)species involved, disease severity and comorbidities. Current guideline-based antimicrobial treatment of NTM-PD is considered long, cumbersome and unsatisfying in terms of outcomes. Novel treatment regimens and strategies are being explored, including rifampicin-free regimens and inclusion of clofazimine and inhaled antibiotics. Host-directed therapies, such as immunomodulators and cytokine-based therapies, might enhance antimycobacterial immune responses. Optimising supportive care, as well as pathogen- and host-directed strategies, is crucial, highlighting the need for personalised approaches tailored to individual patient needs. Further research is warranted to elucidate the complex interplay between host and mycobacterial factors, informing more effective management strategies.

Long-term Outcomes of Adjunctive Lung Resection for Nontuberculous Mycobacteria Pulmonary Disease.

Adjunctive lung resection is recommended for select patients with nontuberculous mycobacteria (NTM) pulmonary disease (PD). However, data are limited on long-term recurrence rates in patients infected with major pathogens, including Mycobacterium avium complex (MAC) and Mycobacterium abscessus (MABC). In this prospective observational study, we retrospectively analyzed data from 125 patients with MAC-PD (n = 90) or MABC-PD (n = 35) who underwent adjunctive lung resection. We evaluated microbiological response, postoperative complications, recurrence, and all-cause mortality over a median 80-month follow-up. Persistent culture positivity (64%) was the most common indication for surgery, followed by hemoptysis, recurrent pneumonia, or radiologic deterioration. Postoperative complications occurred in 18 (14%) patients, with no surgery-related deaths. Treatment outcomes did not significantly differ between the MAC- and MABC-PD groups. Cure with culture conversion was achieved in 112 (90%) patients. Recurrence occurred in 37 (33%) of 112 patients, of which 18 (49%) cases were attributed to reinfection by different NTM species or subspecies. The MAC group had higher recurrence rates than the MABC group (Kaplan-Meier curve, log-rank test, P = .043) and was significantly associated with recurrence in the multivariable analysis (adjusted hazard ratio, 2.71; 95% CI, 1.23-5.99). However, mortality was higher in the MABC-PD group than the MAC-PD group (7/35 vs 4/90, P = .006). Adjunctive lung resection with antibiotics helps to reduce bacterial burden and manage symptoms in patients with NTM-PD. However, it does not prevent recurrence, which is mostly caused by reinfection.