Nontuberculous Mycobacterial Infections

Common Features of Environmental Mycobacterium chelonae from Colorado Using Partial and Whole Genomic Sequence Analyses

Nontuberculous mycobacteria (NTM) are environmentally acquired opportunistic pathogens that cause chronic lung disease in susceptible individuals. While presumed to be ubiquitous in built and natural environments, NTM environmental studies are limited. While environmental sampling campaigns have been performed in geographic areas of high NTM disease burden, NTM species diversity is less defined among areas of lower disease burden like Colorado. In Colorado, metals such as molybdenum have been correlated with increased risk for NTM infection, yet environmental NTM species diversity has not yet been widely studied. Based on prior regression modeling, three areas of predicted high, moderate, and low NTM risk were identified for environmental sampling in Colorado. Ice, plumbing biofilms, and sink tap water samples were collected from publicly accessible freshwater sources. All samples were microbiologically cultured and NTM were identified using partial rpoB gene sequencing. From these samples, areas of moderate risk were more likely to be NTM positive. NTM recovery from ice was more common than recovery from plumbing biofilms or tap water. Overall, nine different NTM species were identified, including clinically important Mycobacterium chelonae. MinION technology was used to whole genome sequence and compare mutational differences between six M. chelonae genomes, representing three environmental isolates from this study and three other M. chelonae isolates from other sources. Drug resistance genes and prophages were common findings among environmentally derived M. chelonae, promoting the need for expanded environmental sampling campaigns to improve our current understanding of NTM species abundance while opening new avenues for improved targeted drug therapies.

Nontuberculous mycobacterial (NTM) infections in bronchiectasis patients: A retrospective US registry cohort study

RATIONALE

Longitudinal epidemiological and clinical data are needed to improve the management of patients with bronchiectasis developing nontuberculous mycobacterial (NTM) pulmonary disease.

OBJECTIVES

To describe the epidemiology, patient management, and treatment outcomes of NTM infections in patients with bronchiectasis enrolled in the United States Bronchiectasis and NTM Research Registry (US BRR).

METHODS

This was a retrospective cohort study of patients with bronchiectasis and NTM infections enrolled with follow-up in the US BRR in 2008-2019. The study included patients with ≥1 positive NTM respiratory culture in the 24-month baseline period (baseline NTM cohort) and/or during the annual follow-up visits (incident NTM cohort). Incidence, prevalence, baseline patient characteristics, treatment exposure, treatment outcomes, and respiratory clinical outcomes were described in the baseline NTM cohort, incident NTM cohort, and both cohorts combined (prevalent NTM cohort).

RESULTS

Between 2008 and 2019, 37.9% (1457/3840) of patients with bronchiectasis in the US BRR met the inclusion criteria for this study and were reported to have Mycobacterium avium complex (MAC) and/or Mycobacterium abscessus complex (MABSC) infections. MAC prevalence increased steadily in the US BRR during 2009-2019; incidence was relatively stable, except for a peak in 2011 followed by a slow decrease. MABSC and mixed MAC/MABSC infections were rare. Most patients with bronchiectasis and NTM infections in the registry were female, White, and aged >65 years. The antibiotics administered most commonly reflected current guidelines. In the prevalent cohort, 44.9% of MAC infections and 37.1% of MABSC infections remained untreated during follow-up, and MAC treatment was initiated with delay (>90 days after positive NTM respiratory culture) twice as frequently as promptly (≤90 days after positive NTM respiratory culture) (68.6% vs 31.4%, respectively). The median time from diagnosis to treatment was shorter for MABSC versus MAC infections (194.0 days [interquartile range (IQR) 8.0, 380.0] vs 296.0 days [IQR 35.0, 705.0], respectively). Among patients with MAC infections who completed treatment, 27.6% were classified as cured and 29.6% as treatment failure during the annual follow-up visit window. For MABSC, these proportions were 25.0% and 28.0%, respectively.

CONCLUSIONS

A considerable proportion of MAC and MABSC infections were untreated or treated after initial delay/observation. MABSC infections were more likely to be treated and start treatment sooner than MAC infections. Further longitudinal studies are warranted to evaluate the monitor-with-delay approach and inform clinical guidelines.

Mycobacterial contamination in tap and shower waters in Thailand

Waterborne disease is increasingly becoming associated with opportunistic premise plumbing pathogens (OPPPs), which can resist residual chlorination, regrow throughout drinking water distribution systems, and colonize premise plumbing. Nontuberculous mycobacteria (NTM) include clinically important species and exert a high burden on healthcare systems. We briefly report a qPCR-based survey of Mycobacterium spp. numbers in tap, POU-treated, and shower waters from Bangkok, Thailand. Non-stagnant tap waters and non-stagnant shower waters had mean numbers of 1.3 × 103 and 2.4 × 103 copies/mL, respectively. Water stagnation resulted in mean numbers higher by up to 1.0 log. The lowest number, 25 copies/mL, was obtained from a POU-treated sample, while the highest number, 2.0 × 104 copies/mL, came from a stagnant tap. Comparing with international data, mean numbers in this study were greater than those in nine out of 11 (82%) comparable studies, and the maximum numbers in this study were also high. Our samples of Bangkok waters exhibited relatively high Mycobacterium spp. numbers, suggesting the need for appropriate POU treatment systems where NTM infection is a health concern. This survey data can be used to set inactivation performance targets in POU water disinfection system design and may also lead to quantitative microbial risk assessment (QMRA) studies.

Inactivation kinetics of 280 nm UV-LEDs against Mycobacterium abscessus in water

Nontuberculous mycobacteria (NTM) are opportunistic premise plumbing pathogens (OPPPs) that cause a burdensome waterborne respiratory disease. Due to their resistance to chemical disinfectants and regrowth in biofilms in drinking water distribution systems, treatment can be better performed using small ultraviolet disinfection units at the point-of-use (POU), such as at a tap or showerhead. Ultraviolet light-emitting diodes (UV-LEDs) are well suited for such applications, but fluence-response data are not available for one of the most important NTM, Mycobacterium abscessus. In this study, a bench-scale 280 nm UV-LED apparatus was used to irradiate M. abscessus in a water matrix. The fluence-response profile was sigmoidal, exhibiting both shoulder and tailing phenomena. Simple linear regression and the Geeraerd's inactivation kinetics model yielded k values of 0.36 and 0.37 cm²/mJ, respectively, revealing that M. abscessus is more resistant to UV than Pseudomonas aeruginosa and Legionella pneumophila, which suggests that NTM are among the most UV-resistant OPPPs. Results of this study suggest that 280 nm UV-LED irradiation can be an effective and practical option to inactivate M. abscessus at the POU. Disinfection units that can deliver a fluence of 10 mJ/cm² are expected to achieve nearly 2 log (99%) inactivation of M. abscessus.

A nontuberculous mycobacterium could solve the mystery of the lady from the Franciscan church in Basel, Switzerland

BACKGROUND

In 1975, the mummified body of a female has been found in the Franciscan church in Basel, Switzerland. Molecular and genealogic analyses unveiled her identity as Anna Catharina Bischoff (ACB), a member of the upper class of post-reformed Basel, who died at the age of 68 years, in 1787. The reason behind her death is still a mystery, especially that toxicological analyses revealed high levels of mercury, a common treatment against infections at that time, in different body organs. The computed tomography (CT) and histological analysis showed bone lesions in the femurs, the rib cage, and the skull, which refers to a potential syphilis case.

RESULTS

Although we could not detect any molecular signs of the syphilis-causing pathogen Treponema pallidum subsp. pallidum, we realized high prevalence of a nontuberculous mycobacterium (NTM) species in brain tissue sample. The genome analysis of this NTM displayed richness of virulence genes and toxins, and similarity to other infectious NTM, known to infect immunocompromised patients. In addition, it displayed potential resistance to mercury compounds, which might indicate a selective advantage against the applied treatment. This suggests that ACB might have suffered from an atypical mycobacteriosis during her life, which could explain the mummy's bone lesion and high mercury concentrations.

CONCLUSIONS

The study of this mummy exemplifies the importance of employing differential diagnostic approaches in paleopathological analysis, by combining classical anthropological, radiological, histological, and toxicological observations with molecular analysis. It represents a proof-of-concept for the discovery of not-yet-described ancient pathogens in well-preserved specimens, using de novo metagenomic assembly.

Mucosal exposure to non-tuberculous mycobacteria elicits B cell-mediated immunity against pulmonary tuberculosis

Bacille Calmette-Guerin (BCG) is the only licensed vaccine against Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB) disease. However, BCG has limited efficacy, necessitating the development of better vaccines. Non-tuberculous mycobacteria (NTMs) are opportunistic pathogens present ubiquitously in the environment. TB endemic countries experience higher exposure to NTMs, but previous studies have not elucidated the relationship between NTM exposure and BCG efficacy against TB. Therefore, we develop a mouse model (BCG + NTM) to simulate human BCG immunization regime and continuous NTM exposure. BCG + NTM mice exhibit superior and prolonged protection against pulmonary TB, with increased B cell influx and anti-Mtb antibodies in serum and airways, compared with BCG alone. Notably, spatial transcriptomics and immunohistochemistry reveal that BCG + NTM mice formed B cell aggregates with features of germinal center development, which correlate with reduced Mtb burden. Our studies suggest a direct relationship between NTM exposure and TB protection, with B cells playing a crucial role.

New design of multilocus sequence analysis of rpoB, ssrA, tuf, atpE, ku, and dnaK for identification of Mycobacterium species

BACKGROUND

Differentiating Mycobacterium tuberculosis (MTB) from nontuberculous mycobacteria (NTM) is very important in the treatment process of patients. According to the American Thoracic Society guideline (ATS), NTM clinical isolates should be identified at the species level proper treatment and patient management. This study aimed to identify NTM clinical isolates by evaluationg rpoB, ssrA, tuf, atpE, ku, and dnaK genes, and use multilocus sequence analysis (MLSA) to concatenate the six genes.

METHODS

Ninety-six Mycobacterium isolates, including 86 NTM and 10 MTB isolates, from all the patients referred to the certain TB Reference Centres were included. All isolates were evaluated by PCR amplification of rpoB, ssrA, tuf, ku, atpE, and dnaK genes and MLSA.

RESULTS

Out of 96 isolates, 91 (94.8%), 87 (90.6%), 72 (75%), 84 (87.5%) and 79 (82.3%) were differentiated to the species level by rpoB, tuf, ssrA, dnaK and atpE genes, respectively. The ku gene was able to identify 69 (80.2%) isolates of the 86 NTM isolates to the species level. We could identify 100% of the isolates to the species level by MLSA.

CONCLUSIONS

None of the PCR targets used in this study were able to completely differentiate all species. The MLSA technique used to concatenate the six genes could increase the identification of clinical Mycobacterium isolates and all 16 species were well-differentiated.

Adaptive Immune Response to Mycobacterium abscessus Complex (MABSC) in Cystic Fibrosis and the Implications of Cross-Reactivity

Background

We aimed to characterise the adaptive immune response to Mycobacterium abscessus complex (MABSC) and its cross-reactivity with Mycobacterium avium complex (MAC) and Mycobacterium bovis (Bacille Calmette-Guérin, BCG) in cystic fibrosis (CF) patients and non-CF controls in terms of lymphocyte proliferation and immunophenotyping, cytokine production and anti-MABSC IgG plasma levels.

Methods

In this cross-sectional analysis, peripheral blood mononuclear cells (PBMC) from CF patients with MABSC (CF/MABSC, n=12), MAC infection history (CF/MAC, n=5), no NTM history (CF/NTM-, n=15), BCG-vaccinated (C/BCG+, n=9) and non-vaccinated controls (C/BCG-, n=8) were cultured for four days under stimulation with an in-house MABSC lysate and we used flow cytometry to assess lymphocyte proliferation (given by lymphoblast formation) and immunophenotypes. Cytokine production was assessed after overnight whole blood stimulation with the same lysate, and anti-MABSC IgG levels were measured in plasma from non-stimulated blood.

Results

All CF/MABSC patients had increased CD3+ and CD19+ lymphoblast formation upon PBMC stimulation with MABSC lysate. There was a higher rate of CD3+ than CD19+ lymphoblasts, predominance of CD4+ over CD8+ lymphoblasts, IFN-γ, TNF-α and IL-2 production, low production of the Th17-associated IL-17, and discrete or no production of Th2/B cell-associated cytokines soluble CD40 ligand (CD40L), IL-4 and IL-5, indicating a Th1-dominated phenotype and infection restricted to the lungs. A similar pattern was seen in C/BCG+ controls, and CF/MAC patients, pointing to cross-reactivity. MABSC-IgG levels were higher in CF/MABSC patients than in both control groups, but not CF/NTM- patients, most of whom also had CD3+ and/or CD19+ lymphoblast formation upon PBMC stimulation, indicating previous exposure, subclinical or latent infection with MABSC or other NTM.

Conclusion

The anti-MABSC immune response is Th1-skewed and underlines the cross-reactivity in the anti-mycobacterial immune response. The results, together with published clinical observations, indicate that BCG vaccination may cross-react against NTM in CF patients, and this should be investigated. Due to cross-reactivity, it would also be interesting to investigate whether a combination of MABSC-induced cytokine production by blood cells and anti-MABSC IgG measurement can be useful for identifying latent or subclinical infection both with MABSC and other NTM in CF patients.