Potential Cross-Transmission of Mycobacterium abscessus among Non-Cystic Fibrosis Patients at a Tertiary Hospital in Japan

Unveiling significant regrowth and potential risk of nontuberculous mycobacteria in hospital water supply system

The health burden of waterborne nontuberculous mycobacteria (NTM) is a rising concern. While the water supply systems can serve as a potential reservoir for NTM, their abundance, diversity, and transmission pathways remain unknown. This study aimed to characterize the prevalence and regrowth of NTM in building water supply system in a hospital where many M. abscessus were isolated from patients. The depletion of residual chlorine after stagnation and supply of warm water at the point of use promoted significant microbial regrowth, including NTM, in the hospital. The absolute abundance of Mycobacterium spp. 16S rRNA genes in tap water and shower water samples increased to approximately 104 copies/mL, while it was below the quantification limit in the finished water from a drinking water treatment plant. Amplicon sequencing of NTM-specific hsp65 genes revealed that M. abscessus was prevalent in all samples, while the dominant NTM species varied depending on locations even in the same building. The presence of M. abscessus in water suggested the possibility of waterborne transmission in the hospital. M. abscessus was frequently isolated from tap water, shower water, and shower biofilms. These isolates demonstrated high clonality and were closely affiliated with the ABS-GL4 cluster of M. abscessus subsp. abscessus. Even though the automatic mixing equipment at the point of use was replaced with new one, the settlement and growth of NTM were reproducibly observed, suggesting mixing equipment as a hotspot for NTM proliferation. Additional interventions including water quality control are required as the hospital water supply system is a hot spot for NTM regrowth.

Preclinical model of Mycobacteroides abscessus lung disease by nose-only exposure of mice to bacterial powder aerosol

The limitations of existing mouse models of lung infection with Mycobacteroides abscessus impede drug discovery and development. In contrast to current animal models that introduce NTM intravenously or by intranasal/intra-tracheal instillation or via bronchoscopy-guided insufflation, we developed a dry powder inhalation (DPI) of M. abscessus ATCC 19977 that generated paucibacillary lung infection and histopathology in immunocompetent mice. Swiss outbred mice receiving ∼1000 (3-log) colony forming units (CFU) of M. abscessus/gram lung tissue via the DPI administered by nose-only inhalation for 90 s showed peak bacterial burden of ∼3.35-log CFU/g in the lungs after 28 days. This was maintained at ∼2-log/g from Day 35 through 56 in the lungs, but not in the spleen. Histopathology indicated increasing severity of inflammation, fibrosis and lung consolidation. Bacteria were rarely recovered from spleen, and histopathological examination indicated partial resolution in the spleen between Days 49-56. The DPI, prepared by freeze-drying log-phase liquid culture with cryoprotectants was formulated to possess aerosol characteristics suitable for alveolar deposition. Aerosol exposure to inoculum mimics natural airborne infection. Non-invasive aerosol infection is convenient, inexpensive, does not require special equipment or extensive training and mitigates stress to animals, but biosafety level 3 containment is recommended to mitigate risk to experimenters.

Genomic Epidemiology of Mycobacterium abscessus on the Island of Montréal Is Not Suggestive of Health Care-Associated Person-to-Person Transmission

BACKGROUND

Mycobacterium abscessus complex (MABC), an opportunistic nontuberculous mycobacteria, can lead to poor clinical outcomes in pulmonary infections. Conflicting data exist on person-to-person transmission of MABC within and across health care facilities. To investigate further, a comprehensive retrospective study across 5 health care institutions on the Island of Montréal was undertaken.

METHODS

We analyzed the genomes of 221 MABC isolates obtained from 115 individuals (2010-2018) to identify possible links. Genetic similarity, defined as ≤25 single-nucleotide polymorphisms (SNPs), was investigated through a blinded epidemiological inquiry.

RESULTS

Bioinformatics analyses identified 28 sequence types, including globally observed dominant circulating clones (DCCs). Further analysis revealed 210 isolate pairs within the SNP threshold. Among these pairs, there was 1 possible laboratory contamination where isolates from different patients processed in the same laboratory differed by only 2 SNPs. There were 37 isolate pairs from patients who had provided specimens from the same hospital; however, epidemiological analysis found no evidence of health care-associated person-to-person transmission between these patients. Additionally, pangenome analysis showed higher discriminatory power than core genome analysis for examining genomic similarity.

CONCLUSIONS

Genomics alone is insufficient to establish MABC transmission, particularly considering the genetic similarity and wide distribution of DCCs, although pangenome analysis has the potential to add further insight. Our findings indicate that MABC infections in Montréal are unlikely attributable to health care-associated person-to-person transmission.

Identifying healthcare transmission routes of nontuberculous mycobacteria with whole genome sequencing: a systematic review

OBJECTIVE

To enumerate and describe the effect of whole genome sequencing (WGS) on epidemiological investigations of healthcare-associated transmission of nontuberculous mycobacteria (NTM).

DESIGN

Systematic review.

METHODS

We performed a literature search using targeted search terms to identify articles meeting inclusion criteria. Data extraction of study characteristics and outcomes was performed by two independent researchers. The primary outcome was the author interpretation of WGS utility in the investigation of suspected healthcare-associated transmission of NTM. The secondary outcome was whether a transmission route was identified through WGS.

RESULTS

Thirty-one studies were included in the final analysis with 28 (90%) concluding that WGS was helpful in transmission investigations and in 19 of these 28 (68%) WGS aided in identifying a transmission route. The most common identified transmission routes were water-borne point sources (10), heater-cooler units (6), patient-to-patient (4), and a healthcare worker (1).

CONCLUSION

WGS is an informative tool in investigating healthcare transmission of NTM.

High rate of macrolide resistance and closely genetically related Mycobacterium abscessus complex strains identified among both cystic fibrosis and non-cystic fibrosis patients within two countries

Mycobacterium abscessus is an emerging opportunistic pathogen affecting patients with chronic lung diseases, primarily cystic fibrosis (CF), or those under immunosuppression. Hence, investigations into the epidemiology and transmission of M. abscessus and accurate antibiotic susceptibility data are essential for the effective treatment of infections caused by this pathogen. This retrospective nationwide study included all clinical M. abscessus isolates (n = 59) from 29 patients diagnosed in the Czech Republic and Slovakia between 2018 and 2023. Whole genome sequencing (WGS) was performed to identify clusters and classify isolates into predominant circulating clones (DCC). Subspecies identification of unique isolates showed subspecies abscessus as the most prevalent (69.0%). The results of drug-susceptibility testing showed that 65.5% of all isolates were resistant to at least three antibiotics tested. CF patients under 24 years of age were the most at-risk group for M. abscessus infection. WGS identified seven clusters (including two cross-border) comprising CF and non-CF patients with a total clustering rate of 48.3%. One cluster involved patients infected with subspecies massiliense strains differing by 0 single nucleotide polymorphisms hospitalized in the same center. Furthermore, we identified representatives of all major DCCs. This study revealed predominant Mycobacterium abscessus complex clones circulating in the Czech Republic and Slovakia. The results show the high discriminatory power of WGS in the molecular epidemiology of M. abscessus and provide supporting evidence of direct or indirect cross-transmission of subspecies massiliense among both CF and non-CF patients.

IMPORTANCE

This study highlights the importance of understanding Mycobacterium abscessus transmission because it poses a growing threat to vulnerable populations, especially young cystic fibrosis patients. Investigating how it spreads and which antibiotics work best is crucial for effective treatment. This research used whole genome sequencing to track M. abscessus and found evidence of potential transmission between patients, including across borders. The findings suggest that dominant strains are circulating and some patients may be infected through direct or indirect contact. This knowledge can inform infection control and treatment strategies.

Pan-lineage Mycobacterium tuberculosis reference genome for enhanced molecular diagnosis

In Mycobacterium tuberculosis (MTB) control, whole genome sequencing-based molecular drug susceptibility testing (molDST-WGS) has emerged as a pivotal tool. However, the current reliance on a single-strain reference limits molDST-WGS's true potential. To address this, we introduce a new pan-lineage reference genome, 'MtbRf'. We assembled 'unmapped' reads from 3,614 MTB genomes (751 L1; 881 L2; 1,700 L3; and 282 L4) into 35 shared, annotated contigs (54 coding sequences [CDSs]). We constructed MtbRf through: (1) searching for contig homologues among genome database that precipitate results uniquely within Mycobacteria genus; (2) comparing genomes with H37Rv ('lift-over') to define 18 insertions; and (3) filling gaps in H37Rv with insertions. MtbRf adds 1.18% sequences to H37rv, salvaging >60% of previously unmapped reads. Transcriptomics confirmed gene expression of new CDSs. The new variants provided a moderate DST predictive value (AUROC 0.60-0.75). MtbRf thus unveils previously hidden genomic information and lays the foundation for lineage-specific molDST-WGS.

Beyond Symptoms: Radiologic identification of asymptomatic Mycobacterium avium complex pulmonary infections

BACKGROUND

Although international nontuberculous mycobacterial pulmonary disease (NTM-PD) guidelines highlight symptom presence at diagnosis, the clinical characteristics of asymptomatic Mycobacterium avium complex pulmonary infection (MAC-PI) patients remain understudied. We clarified the clinical characteristics and course of asymptomatic MAC-PI patients.

METHODS

We retrospectively analyzed 200 consecutive patients with MAC-PIs and adequate available data who newly met the microbiological and radiological criteria for NTM-PD at Fukujuji Hospital from January 2018 to June 2020. We compared the clinical characteristics and course of asymptomatic patients with symptomatic patients and evaluated factors influencing treatment initiation through multivariate analysis.

RESULTS

111 patients were symptomatic and 89 were asymptomatic at diagnosis. While the proportion was significantly lower than that in the symptomatic group (28.8 %), 15.7 % of asymptomatic group patients had cavitary lesions (P = 0.042). In the asymptomatic group, treatments were initiated in 38 (42.7 %) patients, and cavitary lesions, a positive acid-fast bacilli smear, and younger age were independent risk factors for treatment initiation. Among 22 (57.9 %) patients who experienced disease progression necessitating treatment during follow-up, 13 (34.2 %) displayed radiological progression without any worsening of symptoms. Agents used for treatment were consistent across the groups, with no significant differences in culture conversion, microbiological recurrence rates, or spontaneous culture conversion rates.

CONCLUSION

Routine health checkups and radiological examinations can detect clinically important MAC-PIs even in the absence of symptoms. Considering that the clinical course of asymptomatic MAC-PI patients is largely similar to that of symptomatic patients, timely and appropriate management and intervention are essential for all MAC-PI patients.

Non-Tuberculous Mycobacterial isolates from Panama: A retrospective 5-year analysis (2017-2021)

BACKGROUND

The genus Mycobacterium includes well-known bacteria such as M. tuberculosis causing tuberculosis and M. leprae causing leprosy. Additionally, various species collectively termed non-tuberculous mycobacteria (NTM) can cause infections in humans and animals, affecting individuals across all age groups and health conditions. However, information on NTM infection prevalence in Panama is limited.

METHODS

This study conducted a retrospective analysis of clinical records from 2017 to 2021, specifically focusing on patients with NTM isolates. Data were categorized by variables like sex, age, HIV status, and sample source.

RESULTS

Among the 4430 clinical records analyzed, 698 were linked to patients with NTM isolates. Of these patients, 397 were male, and 301 were female. Most female patients with NTM isolates (n = 190) were aged >45 to 85 years, while most male patients (n = 334) fell in the >25 to 75 years age group. A noteworthy proportion of male patients (n = 65) were aged 25-35 years. A significant age difference between male (median [min-max] = 53 years [3-90]) and female (median [61 years [6-94]) patients was observed (p < 0.001). Regarding HIV status, 77 positive individuals were male, and 19 were female (p < 0.001). Most samples (n = 566) were sputum samples, with additional pulmonary-associated samples such as broncho-alveolar lavage, tracheal secretions, and pleural fluid samples. Among extrapulmonary isolates (n = 48), sources included catheter secretions, intracellular fluids, peritoneal fluid, blood cultures, cerebrospinal fluid, bone marrow samples, and capillary transplant lesions. Specifically, the analysis identified the pathogenic microorganisms responsible for mycobacteriosis in Panama during the specific period 2017-2021, as M. fortuitum (34.4%), M. intracellulare (20.06%), and M. abscessus (13.75%), respectively.

CONCLUSIONS

This study highlights the growing public health concern of NTM infections in Panama. The research provides valuable insights into the prevalence and distribution of NTM species in the country, offering a foundation for the development and implementation of effective prevention and control strategies for NTM infections in Panama.

Employing Multicolor Melting Curve Analysis to Rapidly Identify Non-Tuberculous Mycobacteria in Patients with Bronchiectasis: A Study from a Pulmonary Hospital in the Fuzhou District of China, 2018-2022

Non-tuberculous mycobacteria (NTM) infection is common in bronchiectasis, with rising incidence globally. However, investigation into NTM in bronchiectasis patients in China remains relatively limited. This work aimed to identify and understand the features of NTM in bronchiectasis patient in Fuzhou district of China. The pulmonary samples were collected from 281 bronchiectasis patients with suspected NTM infection in Fuzhou, 2018-2022. MPB64 antigen detection was employed for the preliminary evaluation of NTM. Further NTM identification was realized using gene chip and gene sequencing. Among 281 patients, 172 (61.21%) patients were NTM-positive (58.72%) according to MPB64 antigen detection, with females (58.72%) outnumbering males (41.28%) and the highest prevalence in the age group of 46-65 years. In total, 47 NTM single infections and 3 mixed infections (1 Mycobacterium tuberculosis complex-M. intracellulare, 1 M. avium-M. intracellulare, and 1 M. abscessus-M. intracellulare) were identified through multicolor melting curve analysis (MMCA), which was compared with gene sequencing results. Both methods suggested Mycobacterium (M.) intracellulare, M. abscessus, and M. avium as the primary NTM species affecting bronchiectasis patients. M. intracellulare and M. abscessus were more frequent in females than males with the highest prevalence in the age group of 46-65 years according to MMCA. This research provides novel insights into the epidemiological and clinical features of NTM in bronchiectasis patients in Southeastern China. Significantly, M. intracellulare, M. abscessus, and M. avium were identified as the major NTM species, contributing to a better understanding and management of bronchiectasis accompanied by NTM infection.

Environmental Sources and Transmission of Nontuberculous Mycobacteria

The field of environmental nontuberculous mycobacteria (NTM) is benefiting from a new era of genomics that has catapulted our understanding of preferred niches, transmission, and outbreak investigations. The ability to forecast environmental features that promote or reduce environmental NTM prevalence will greatly improve with coordinated environmental sampling and by elevating the necessity for uniform disease notifications. Studies that synergize environmental biology, isolate notifications, and comparative genomics in prospective, longitudinal studies, particularly during climate changes and weather events, will be useful to solve longstanding NTM public health quandaries.

In Vitro Synergistic Effects of Omadacycline with Other Antimicrobial Agents against Mycobacterium abscessus

The clinical importance of Mycobacterium abscessus species (MABS) infections has been increasing. However, the standard treatment regimens recommended in the current guidelines often result in unfavorable outcomes. Therefore, we investigated the in vitro activity of omadacycline (OMC), a novel tetracycline, against MABS to explore its potential as a novel therapeutic option. The drug susceptibilities of 40 Mycobacterium abscessus subsp. abscessus (Mab) clinical strains obtained from the sputum of 40 patients from January 2005 to May 2014 were investigated. The MIC results for OMC, amikacin (AMK), clarithromycin (CLR), clofazimine (CLO), imipenem (IPM), rifabutin (RFB), and tedizolid (TZD) alone and their combined effects (with OMC) were examined using the checkerboard method. Additionally, we studied the differences in the effectiveness of the antibiotic combinations based on the colony morphotype of Mab. The MIC50 and MIC90 of OMC alone were 2 and 4 μg/mL, respectively. The combinations of OMC with AMK, CLR, CLO, IPM, RFB, and TZD showed synergy against 17.5%, 75.8%, 25.0%, 21.1%, 76.9%, and 34.4% of the strains, respectively. Additionally, OMC combined with CLO (47.1% versus 9.5%, P = 0.023) or TZD (60.0% versus 12.5%, P = 0.009) showed significantly higher synergy against strains with rough morphotypes than those with smooth morphotypes. In conclusion, the checkerboard analyses revealed that the synergistic effects of OMC were observed most frequently with RFB, followed by CLR, TZD, CLO, IPM, and AMK. Furthermore, OMC tended to be more effective against rough-morphotype Mab strains.

Phylogenomics of nontuberculous mycobacteria respiratory infections in people with cystic fibrosis

Nontuberculous mycobacteria (NTM) can cause severe pulmonary disease in people with cystic fibrosis (pwCF). These infections present unique challenges for diagnosis and treatment, prompting a recent interest in understanding NTM transmission and pathogenesis during chronic infection. Major gaps remain in our knowledge regarding basic pathogenesis, immune evasion strategies, population dynamics, recombination potential, and the evolutionary implications of host and antibiotic pressures of long-term NTM infections in pwCF. Phylogenomic techniques have emerged as an important tool for tracking global patterns of transmission and are beginning to be used to ask fundamental biological questions about adaptation to the host during pathogenesis. In this review, we discuss the burden of NTM lung disease (NTM-LD), highlight the use of phylogenomics in NTM research, and address the clinical implications associated with these studies.

Mycobacterium abscessus Cluster in Cardiac Surgery Patients Potentially Attributable to a Commercial Water Purification System

BACKGROUND

Nontuberculous mycobacteria are water-avid pathogens that are associated with nosocomial infections.

OBJECTIVE

To describe the analysis and mitigation of a cluster of Mycobacterium abscessus infections in cardiac surgery patients.

DESIGN

Descriptive study.

SETTING

Brigham and Women's Hospital, Boston, Massachusetts.

PARTICIPANTS

Four cardiac surgery patients.

INTERVENTION

Commonalities among cases were sought, potential sources were cultured, patient and environmental specimens were sequenced, and possible sources were abated.

MEASUREMENTS

Description of the cluster, investigation, and mitigation.

RESULTS

Whole-genome sequencing confirmed homology among clinical isolates. Patients were admitted during different periods to different rooms but on the same floor. There were no common operating rooms, ventilators, heater-cooler devices, or dialysis machines. Environmental cultures were notable for heavy mycobacterial growth in ice and water machines on the cluster unit but little or no growth in ice and water machines in the hospital's other 2 inpatient towers or in shower and sink faucet water in any of the hospital's 3 inpatient towers. Whole-genome sequencing confirmed the presence of a genetically identical element in ice and water machine and patient specimens. Investigation of the plumbing system revealed a commercial water purifier with charcoal filters and an ultraviolet irradiation unit leading to the ice and water machines in the cluster tower but not the hospital's other inpatient towers. Chlorine was present at normal levels in municipal source water but was undetectable downstream from the purification unit. There were no further cases after high-risk patients were switched to sterile and distilled water, ice and water machine maintenance was intensified, and the commercial purification system was decommissioned.

LIMITATION

Transmission pathways were not clearly characterized.

CONCLUSION

Well-intentioned efforts to modify water management systems may inadvertently increase infection risk for vulnerable patients.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Genomic epidemiology of Mycobacterium abscessus in a Canadian cystic fibrosis centre

The Mycobacterium abscessus complex causes significant morbidity and mortality among patients with Cystic Fibrosis (CF). It has been hypothesized that these organisms are transmitted from patient to patient based on genomics. However, few studies incorporate epidemiologic data to confirm this hypothesis. We longitudinally sampled 27 CF and 7 non-CF patients attending a metropolitan hospital in Ontario, Canada from 2013 to 2018. Whole genome sequencing along with epidemiological data was used to evaluate the likelihood of transmission. Overall, the genetic diversity of M. abscessus was large, with a median pairwise distance (IQR) of 1,279 (143-134) SNVs between all Ontario M. abscessus isolates and 2,908 (21-3,204) single nucleotide variants (SNVs) between M. massiliense isolates. This reflects the global diversity of this pathogen, with Ontario isolates widely dispersed throughout global phylogenetic trees of each subspecies. Using a maximum distance of 25 SNVs as a threshold to identify possible transmission, we identified 23 (of 276 total) pairs of closely-related isolates. However, transmission was probable for only one pair based on both genomic and epidemiological data. This suggests that person-to-person transmission of M. abscessus among CF patients is indeed rare and reinforces the critical importance of epidemiological data for inferences of transmission.