Nitric oxide-releasing prodrug for the treatment of complex Mycobacterium abscessus infections.

Non-tuberculosis mycobacteria (NTM) can cause severe respiratory infection in patients with underlying pulmonary conditions, and these infections are extremely difficult to treat. In this report, we evaluate a nitric oxide (NO)-releasing prodrug [methyl tris diazeniumdiolate (MD3)] against a panel of NTM clinical isolates and as a treatment for acute and chronic NTM infections in vivo. Its efficacy in inhibiting growth or killing mycobacteria was explored in vitro alongside evaluation of the impact to primary human airway epithelial tissue. Airway epithelial tissues remained viable after exposure at concentrations of MD3 needed to kill mycobacteria, with no inherent toxic effect from drug scaffold after NO liberation. Resistance studies conducted via serial passage with representative Mycobacterium abscessus isolates demonstrated no resistance to MD3. When administered directly into the lung via intra-tracheal administration in mice, MD3 demonstrated significant reduction in M. abscessus bacterial load in both acute and chronic models of M. abscessus lung infection. In summary, MD3 is a promising treatment for complex NTM pulmonary infection, specifically those caused by M. abscessus, and warrants further exploration as a therapeutic.

Treatable traits and challenges in the clinical management of non-tuberculous mycobacteria lung disease in people with cystic fibrosis.

INTRODUCTION: Over the last ten years an increasing prevalence and incidence of non-tuberculous mycobacteria (NTM) has been reported among patients with cystic fibrosis (CF) Viviani (J Cyst Fibros, 15(5):619-623, 2016). NTM pulmonary disease has been associated with negative clinical outcomes and often requires pharmacological treatment. Although specific guidelines help clinicians in the process of diagnosis and clinical management, the focus on the multidimensional assessment of concomitant problems is still scarce. MAIN BODY: This review aims to identify the treatable traits of NTM pulmonary disease in people with CF and discuss the importance of a multidisciplinary approach in order to detect and manage all the clinical and behavioral aspects of the disease. The multidisciplinary complexity of NTM pulmonary disease in CF requires careful management of respiratory and extra-respiratory, including control of comorbidities, drug interactions and behavioral factors as adherence to therapies. CONCLUSIONS: The treatable trait strategy can help to optimize clinical management through systematic assessment of all the aspects of the disease, providing a holistic treatment for such a multi-systemic and complex condition.

River Sediments Downstream of Villages in a Karstic Watershed Exhibited Increased Numbers and Higher Diversity of Nontuberculous Mycobacteria.

The impact of residential villages on the nontuberculous mycobacteria (NTM) in streams flowing through them has not been studied in detail. Water and sediments of streams are highly susceptible to anthropogenic inputs such as surface water flows. This study investigated the impact of seven residential villages in a karst watershed on the prevalence and species spectrum of NTM in water and sediments. Higher NTM species diversity (i.e., 19 out of 28 detected) was recorded downstream of the villages and wastewater treatment plants (WWTPs) compared to sampling sites upstream (i.e., 5). Significantly, higher Zn and lower silicon concentrations were detected in sediments inside the village and downstream of the WWTP's effluents. Higher phosphorus concentration in sediment was downstream of WWTPs compared to other sampling sites. The effluent from the WWTPs had a substantial impact on water quality parameters with significant increases in total phosphorus, anions (Cl-and N-NH3-), and cations (Na+ and K+). The results provide insights into NTM numbers and species diversity distribution in a karst watershed and the impact of urban areas. Although in this report the focus is on the NTM, it is likely that other water and sediment microbes will be influenced as well.

Rapid Mycobacterium abscessus antimicrobial susceptibility testing based on antibiotic treatment response mapping via Raman Microspectroscopy.

OBJECTIVES: Antimicrobial susceptibility tests (ASTs) are pivotal tools for detecting and combating infections caused by multidrug-resistant rapidly growing mycobacteria (RGM) but are time-consuming and labor-intensive. DESIGN: We used a Mycobacterium abscessus-based RGM model to develop a rapid (24-h) AST from the beginning of the strain culture, the Clinical Antimicrobials Susceptibility Test Ramanometry for RGM (CAST-R-RGM). The ASTs obtained for 21 clarithromycin (CLA)-treated and 18 linezolid (LZD)-treated RGM isolates. RESULTS: CAST-R-RGM employs D2O-probed Raman microspectroscopy to monitor RGM metabolic activity, while also revealing bacterial antimicrobial drug resistance mechanisms. The results of clarithromycin (CLA)-treated and linezolid (LZD)-treated RGM isolates exhibited 90% and 83% categorical agreement, respectively, with conventional AST results of the same isolates. Furthermore, comparisons of time- and concentration-dependent Raman results between CLA- and LZD-treated RGM strains revealed distinct metabolic profiles after 48-h and 72-h drug treatments, despite similar profiles obtained for both drugs after 24-h treatments. CONCLUSIONS: Ultimately, the rapid, accurate, and low-cost CAST-R-RGM assay offers advantages over conventional culture-based ASTs that warrant its use as a tool for improving patient treatment outcomes and revealing bacterial drug resistance mechanisms.

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.

Addressing antimicrobial resistance with the IDentif.AI platform: Rapidly optimizing clinically actionable combination therapy regimens against nontuberculous mycobacteria.

Background: Current standard of care (SOC) regimens against nontuberculous mycobacteria (NTM) usually result in unsatisfactory therapeutic responses, primarily due to multi-drug resistance and antibiotic susceptibility-guided therapies. In the midst of rising incidences in NTM infections, strategies to develop NTM-specific treatments have been explored and validated. Methods: To provide an alternative approach to address NTM-specific treatment, IDentif.AI was harnessed to rapidly optimize and design effective combination therapy regimens against Mycobacterium abscessus (M. abscessus), the highly resistant and rapid growth species of NTM. IDentif.AI interrogated the drug interaction space from a pool of 6 antibiotics, and pinpointed multiple clinically actionable drug combinations. IDentif.AI-pinpointed actionable combinations were experimentally validated and their interactions were assessed using Bliss independence model and diagonal measurement of n-way drug interactions. Results: Notably, IDentfi.AI-designed 3- and 4-drug combinations demonstrated greater %Inhibition efficacy than the SOC regimens. The platform also pinpointed two unique drug interactions (Levofloxacin (LVX)/Rifabutin (RFB) and LVX/Meropenem (MEM)) that may serve as the backbone of potential 3- and 4-drug combinations like LVX/MEM/RFB, which exhibited 58.33±4.99 %Inhibition efficacy against M. abscessus. Further analysis of LVX/RFB via Bliss independence model pointed to dose-dependent synergistic interactions in clinically actionable concentrations. Conclusions: IDentif.AI-designed combinations may provide alternative regimen options to current SOC combinations that are often administered with Amikacin, which has been known to induce ototoxicity in patients. Furthermore, IDentif.AI pinpointed 2-drug interactions may also serve as the backbone for the development of other effective 3- and 4-drug combination therapies. The findings in this study suggest that this platform may contribute to NTM-specific drug development.

Comorbidities of nontuberculous mycobacteria infection in Korean adults: results from the National Health Insurance Service-National Sample Cohort (NHIS-NSC) database.

BACKGROUND: The global prevalence and incidence of nontuberculous mycobacteria (NTM) infection are increasing. However, the prevalence of NTM infection-associated comorbidities remains understudied. Thus, we investigated the comorbidities associated with NTM infection using the National Health Insurance Service-National Sample Cohort (NHIS-NSC) 2.0 database of the National Health Insurance Service (NHIS). METHODS: In this case-control study, patients with NTM infection and controls aged 20-89 years of age were matched 1:4 by sex, age, region, and income. A total of 26 comorbidities were selected based on previous reports and claims data analysis. The distribution of comorbidities was compared between patients with NTM infection and controls by sex and age using logistic regression analysis. RESULTS: In total, 893 patients (379 men and 514 women) with NTM infection (mean age, 56.1 years) and 3,572 controls (mean age, 55.6 years) were included. The odds ratio for prevalence of respiratory diseases, metabolic diseases, musculoskeletal disorders, gastrointestinal diseases, skin diseases, mental diseases, and neoplasms was significantly higher in patients with NTM infection than in the control group. Among comorbid diseases, the odds ratios (ORs) for the prevalence of the respiratory diseases such as bronchiectasis (OR [95% confidence interval (CI)]: 26.79 [19.69-36.45]) and interstitial pneumonitis (OR [95% CI]: 15.10 [7.15-31.89]) were the highest. No significant differences were observed in NTM infection-related comorbidities between men and women. In the younger age group (20-39 years old), the prevalence of respiratory and systemic diseases such as hypertension and diabetes was higher in the patient group than in the control group. CONCLUSIONS: NTM infection is associated with several respiratory and systemic diseases that should be considered when providing medical care to patients with NTM infection.

Investigation of drug regimens and treatment outcome in patients with Mycobacterium Simiae: a systematic review.

INTRODUCTION: Mycobacterium simiae (M.simiae), a non-tuberculous mycobacterium (NTM), rare causes infection including localized pulmonary to disseminated disease in immunocompromised patients. An optimal pharmacological management practice has not yet been defined for this infection. This study investigates drug regimens and treatment outcomes in patients with M. simiae to describe different drug regimen with the therapeutic response. AREAS COVERED: The three databases PubMed, Scopus, and Web of science were systematically searched from June 1994 to June 2021 to retrieve relevant articles. The inclusion criterion included studies, which reported treatment outcomes in patients with M. simiae infections. Treatment success was defined as the achievement of culture conversion, and the improvement of the symptoms and radiologic signs among the patients. EXPERT OPINION: Data of 223 patients were retrieved from 40 studies. Duration of the treatment regimens used in different studies ranged from 2 to 12 months. The most common treatment regimens administered for M. simiae infection were as follows: clarithromycin, rifampin, ethambutol, moxifloxacin, or ciprofloxacin and amikacin plus cotrimoxazole or pyrazinamide in some regimens. Macrolides, such as clarithromycin, combined with quinolones (such as moxifloxacin) and TMP/SMX, which are used in combination, had the most significant effect on eliminating the pulmonary signs of M. simiae.

Importance of asking a social history: atypical pulmonary infections and occupational hazards.

Non-tuberculous mycobacteria (NTM) are ubiquitous in the environment, but NTM infection is limited to individuals with risk factors. We present a case of a 62-year-old man who presented with a 1 year history of cough and shortness of breath. History was notable for significant tobacco use and work as a sandblaster without the use of personal protective equipment. His chest X-ray showed bilateral upper lobe cavitary lesions, which were redemonstrated on chest CT. A sputum Gram stain was positive for acid-fast bacilli, but his tuberculosis QuantiFERON was negative. He was started on empiric tuberculosis treatment. Sputum cultures ultimately returned for Mycobacterium avium intracellulare complex, and treatment was narrowed to azithromycin, rifampin and ethambutol. The case highlights risk factors for NTM infection, notably for this patient, occupational exposures that likely lead to the development of pneumoconiosis. Healthcare providers should ask about occupational history and counsel patients about protection from occupational hazards.

Minimal Inhibitory Concentration of Clofazimine Among Clinical Isolates of Nontuberculous Mycobacteria and Its Impact on Treatment Outcome.

BACKGROUND: Clofazimine has been regarded as a promising agent for the treatment of nontuberculous mycobacteria pulmonary disease (NTM-PD). However, its overall effectiveness in vitro and in the clinic remains unknown. RESEARCH QUESTION: What is the minimal inhibitory concentration (MIC) of clofazimine in clinical isolates and the association between MICs and treatment outcome? STUDY DESIGN AND METHODS: MICs for clofazimine were measured in clinical isolates from NTM-PD patients who participated in a prospective study at Seoul National University Hospital. The MIC was determined by using the broth microdilution concentration method. Correlation between MIC and conversion to negative of sputum culture with clofazimine was determined. RESULTS: Of a total 189 isolates, 133 strains were Mycobacterium avium complex (MAC) and 40 strains were M abscessus. Although the clofazimine MICs for MAC ranged from 0.031 mg/L to 8 mg/L, the values obtained for M abscessus ranged from 0.031 mg/L to 16 mg/L. Of 20 patients who were treated with a regimen including clofazimine, eight achieved negative conversion of sputum culture. All patients with isolates exhibiting clofazimine MIC values ≤ 0.25 mg/L achieved culture conversion. The likelihood of culture conversion in patients with MIC value ≤ 0.25 mg/L was much higher than that of patients with MIC value > 0.5 mg/L (OR, 39.3; P = .021). INTERPRETATION: The MICs of clofazimine varied widely in clinical isolates from patients with NTM-PD. Negative conversion of sputum culture with clofazimine use was associated with a lower MIC value. Clofazimine use could be considered in patients with NTM-PD when the MIC value is ≤ 0.25 mg/L. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT01616745; URL: www.clinicaltrials.gov.

Epidemiology, diagnosis & treatment of non-tuberculous mycobacterial diseases.

Non-tuberculous mycobacteria (NTM) are ubiquitously present in the environment, but NTM diseases occur infrequently. NTM are generally considered to be less virulent than Mycobacterium tuberculosis, however, these organisms can cause diseases in both immunocompromised and immunocompetent hosts. As compared to tuberculosis, person-to-person transmission does not occur except with M. abscessus NTM species among cystic fibrosis patients. Lung is the most commonly involved organ, and the NTM-pulmonary disease (NTM-PD) occurs frequently in patients with pre-existing lung disease. NTM may also present as localized disease involving extrapulmonary sites such as lymph nodes, skin and soft tissues and rarely bones. Disseminated NTM disease is rare and occurs in individuals with congenital or acquired immune defects such as HIV/AIDS. Rapid molecular tests are now available for confirmation of NTM diagnosis at species and subspecies level. Drug susceptibility testing (DST) is not routinely done except in non-responsive disease due to slowly growing mycobacteria ( M. avium complex, M. kansasii) or infection due to rapidly growing mycobacteria, especially M. abscessus. While the decision to treat the patients with NTM-PD is made carefully, the treatment is given for 12 months after sputum culture conversion. Additional measures include pulmonary rehabilitation and correction of malnutrition. Treatment response in NTM-PD is variable and depends on isolated NTM species and severity of the underlying PD. Surgery is reserved for patients with localized disease with good pulmonary functions. Future research should focus on the development and validation of non-culture-based rapid diagnostic tests for early diagnosis and discovery of newer drugs with greater efficacy and lesser toxicity than the available ones.

Cutaneous infection by Mycobacterium lentiflavum after subcutaneous injection of lipolytic formula

Abstract The incidence of nontuberculous mycobacterial infections is increasing worldwide; by 2017, more than 190 species and subspecies have been documented. Although classically associated with immunosuppression, the recognition of these etiological agents in diseases affecting immunocompetent individuals and in healthcare-associated infections, such as after surgical and cosmetic procedures, makes the study of the epidemiology and pathogenesis of these microorganisms relevant in medical practice. Mycobacterium lentiflavum is slow-growing and rarely affects the skin. A case of cutaneous mycobacteriosis caused by M. lentiflavum is reported in an immunocompetent patient after subcutaneous injection of a lipolytic compound, treated with clarithromycin and levofloxacin.

Cutaneous infection by Mycobacterium lentiflavum after subcutaneous injection of lipolytic formula.

The incidence of nontuberculous mycobacterial infections is increasing worldwide; by 2017, more than 190 species and subspecies have been documented. Although classically associated with immunosuppression, the recognition of these etiological agents in diseases affecting immunocompetent individuals and in healthcare-associated infections, such as after surgical and cosmetic procedures, makes the study of the epidemiology and pathogenesis of these microorganisms relevant in medical practice. Mycobacterium lentiflavum is slow-growing and rarely affects the skin. A case of cutaneous mycobacteriosis caused by M. lentiflavum is reported in an immunocompetent patient after subcutaneous injection of a lipolytic compound, treated with clarithromycin and levofloxacin.

Incidence, Clinical Manifestation, Treatment Outcome, and Drug Susceptibility Pattern of Nontuberculous Mycobacteria in HIV Patients in Tehran, Iran.

BACKGROUND: Nontuberculous mycobacterial (NTM) infections have radically increased worldwide due to the increase in HIV infections. The disease activity increases with progressive immunodeficiency. METHODS: A total of 216 HIV seropositive patients suspected of having mycobacterial infection were recruited for this study. Clinical samples were collected from each patient and cultured on Lowenstein-Jensen media. Detection and species identification were simultaneously done using Reverse Blot Hybridization Assay System. Also, the minimum inhibitory concentrations (MIC) for each isolate were determined in 7H9 broth media for 10 antibiotics. RESULTS: In this study, 4 rapid and 4 slow-growing NTM species were isolated and identified. Mycobacterium fortuitum was the most common NTM species, 3/8 (37.5%), followed by Mycobacterium kansasii, 2/8 (25%). The cases were identified as pulmonary disease, 5/8 (62.5 %), disseminated infection, 2/8 (25%), and skin abscess, 1/8 (12.5%). M. chelonae and Mycobacterium avium were isolated from patients diagnosed with disseminated infection with treatment failure. The skin abscess was caused by infection with M. simiae. The results of the MIC testing were as follows: M. kansasii and M. fortuitum were susceptible to amikacin (AMK); M. avium to clarithromycin (CLA); M. fortuitum 2/3 (67%) to ciprofloxacin (CIP); 1/2 (50%) of M. kansasii isolates to CLA, and M. chelonae to rifampin (RIF), linezolid (LIN), AMK, and CIP at medium and high concentrations. CONCLUSION: AMK showed incredible in vitro activity against M. kansasii and M. fortuitum. Also, M. avium was susceptible to CLA, whereas M. simiae and M. chelonae were resistant to the tested drugs in this study.

State-of-the-art treatment strategies for nontuberculous mycobacteria infections.

INTRODUCTION: Non-tuberculous Mycobacteria (NTM) are a group of organisms whose importance in medicine seems to be increasing in recent times. The increasing number of patients susceptible to these diseases make it necessary to expand our knowledge of therapeutic options and to explore future possibilities for the development of a therapeutic arsenal. AREAS COVERED: In this review, the authors provide a brief introduction about the present importance of NTM and describe the present recommendations of the available guidelines for their treatment. They include a description of the future options for the management of these patients, especially focusing on new antibiotics. The authors also look at possibilities for future therapeutic options, such as antibiofilm strategies. EXPERT OPINION: No actual changes have been made to the current recommendations for the management of most NTM infections (except perhaps the availability of nebulized amikacin). However, it is also true that we have increased the number of available antibiotic treatment options with good in vitro activity against NTM. The use of these drugs in selected cases could increase the therapeutic possibilities. However, some problems are still present, such as the knowledge of the actual meaning of a NTM isolate, and will probably be a key part of future research.

Is there a role for tedizolid in the treatment of non-tuberculous mycobacterial disease?

BACKGROUND: Pulmonary infections caused by non-tuberculous mycobacteria (NTM) are hard to treat and have low cure rates despite intensive multidrug therapy. OBJECTIVES: To assess the feasibility of tedizolid, a new oxazolidinone, for the treatment of Mycobacterium avium and Mycobacterium abscessus. METHODS: We determined MICs of tedizolid for 113 isolates of NTM. Synergy with key antimycobacterial drugs was assessed using the chequerboard method and calculation of the FIC index (FICI). We performed time-kill kinetics assays of tedizolid alone and combined with amikacin for M. abscessus and with ethambutol for M. avium. Human macrophages were infected with M. abscessus and M. avium and subsequently treated with tedizolid; intracellular and extracellular cfu were quantified over time. RESULTS: NTM isolates generally had a lower MIC of tedizolid than of linezolid. FICIs were lowest between tedizolid and amikacin for M. abscessus (FICI = 0.75) and between tedizolid and ethambutol for M. avium (FICI = 0.72). Clarithromycin and tedizolid showed initial synergy, which was abrogated by erm(41)-induced macrolide resistance (FICI = 0.53). Tedizolid had a weak bacteriostatic effect on M. abscessus and combination with amikacin slightly prolonged its effect. Tedizolid had concentration-dependent activity against M. avium and its efficacy was enhanced by ethambutol. Both combinations had a concentration-dependent synergistic effect. Tedizolid could inhibit the intracellular bacterial population of both M. avium and M. abscessus. CONCLUSIONS: Tedizolid should be further investigated in pharmacodynamic studies and clinical trials for M. avium complex pulmonary disease. It is less active against M. abscessus, but still promising.

Postoperative Mycobacteroides abscessus subsp. abscessus endophthalmitis: Clinical analysis of 12 clustered adults and a proposed therapeutic algorithm.

PURPOSE: Postoperative endophthalmitis caused by nontuberculous mycobacterium is a rare but devastating complication after intraocular surgery. However, optimal treatment strategies remain undetermined in view of its rarity. METHODS: We investigated the cases of culture-proven postoperative Mycobacteroides abscessus subsp. abscessus endophthalmitis in southern Taiwan, focusing on clinical manifestations and microbiological study, and aimed to describe clinical staging and to propose a therapeutic modality for this disease. RESULTS: Twelve cases, including two published cases, were treated in two medical centers in southern Taiwan between Aug. 2011 and Dec. 2016, and all ever received cataract surgery at one clinic. Their disease courses could be categorized into four distinct stages, i.e., the initial, quiescent, recurrent, and end stage, and some cases experienced 1-4 cycles of quiescent-recurrent stages. Although all eyes ended up with phthisis or were eviscerated, the affected eyes receiving pars plana vitrectomy (PPV) tended to become quiescent and survived longer than those without PPV (adjusted hazard ratio: 13.9, p < 0.05). Eight isolates of eight patients were available for microbiological study. All isolates were susceptible to amikacin, and inducible clarithromycin resistance was observed in 100% of isolates. CONCLUSION: Despite the preservation of vision in postoperative M.abscessus endophthalmitis remained a challenge, a stage-based approach is proposed, which may facilitate decision-makings for the future study.

Trypethelone and phenalenone derivatives isolated from the mycobiont culture of Trypethelium eluteriae Spreng. and their anti-mycobacterial properties.

The metabolites of the mycobiont culture of the lichen Trypethelium eluteriae were isolated by column chromatography and preparative TLC. Nine compounds (1-9) including two new trypethelones, 8-methoxytrypethelone (6) and 5'-hydroxy-8-ethoxytrypethelone (9), together with four known trypethelones (3-4, 7-8), and two known phenalenones (1-2) were characterized. It is the first report of 8-methoxytrypethelone methyl ether (5) purification as a racemic mixture in T. eluteriae. Earlier, 7-hydroxyl-8-methoxyltrypethelone (10) was reported as new compound with erroneous spectroscopic data. This compound was identified later as 8-hydroxytrypethelone methyl ether (4). X-ray crystallographic structures of compounds 5-7 were elucidated for the first time. Phenalenones (1-2) and trypethelones (5-6 and 9) were the additional compounds discovered in the cultured mycobiont of T. eluteriae. Six compounds (1-2, 5-8) were screened against Mycobacterium tuberculosis H37Rv and two compounds (7-8) against non-tuberculosis mycobacteria and other human pathogenic bacteria. Compound (7) inhibited M. tuberculosis H37Rv strain with an MIC of 12.5 µg/mL.

Decrypting the environmental sources of Mycobacterium canettii by high-throughput biochemical profiling.

Mycobacterium canettii is a smooth bacillus related to the Mycobacterium tuberculosis complex. It causes lymph nodes and pulmonary tuberculosis in patients living in countries of the Horn of Africa, including Djibouti. The environmental reservoirs of M. canettii are still unknown. We aimed to further decrypt these potential reservoirs by using an original approach of High-Throughput Carbon and Azote Substrate Profiling. The Biolog Phenotype profiling was performed on six clinical strains of M. canettii and one M. tuberculosis strain was used as a positive control. The experiments were duplicated and authenticated by negative controls. While M. tuberculosis metabolized 22/190 (11%) carbon substrates and 3/95 (3%) nitrogen substrates, 17/190 (8.9%) carbon substrates and three nitrogen substrates were metabolized by the six M. canettii strains forming the so-called corebiologome. A total at 16 carbon substrates and three nitrogen substrates were metabolized in common by M. tuberculosis and the six M. canettii strains. Moreover, at least one M. canettii strain metabolized 36/190 (19%) carbon substrates and 3/95 (3%) nitrogen substrates for a total of 39/285 (13%) substrates. Classifying these carbon and nitrogen substrates into ten potential environmental sources (plants, fruits and vegetables, bacteria, algae, fungi, nematodes, mollusks, mammals, insects and inanimate environment) significantly associated carbon and nitrogen substrates metabolized by at least one M. canettii strain with plants (p = 0.006). These results suggest that some plants endemic in the Horn of Africa may serve as ecological niches for M. canettii. Further ethnobotanical studies will indicate plant usages by local populations, then guiding field microbiological investigations in order to prove the definite environmental reservoirs of this opportunistic tuberculous pathogen.