Nontuberculous Mycobacteria in Saudi Arabia and Gulf Countries: A Review

K. pneumoniae and M. smegmatis infect epithelial cells via different strategies

Background

As the first line of defense, epithelial cells play a vital role in the initiation and control of both innate and adaptive immunity, which participate in the development of disease. Despite its therapeutic significance, little is understood about the specific interaction between pathogenic microorganisms and lung epithelial cells.

Methods

In this study, we performed a head-to-head comparison of the virulence and infection mechanisms of Klebsiella pneumoniae (K. pneumoniae) and Mycobacterium smegmatis (M. smegmatis), which represent Gram-negative/positive respiratory pathogens, respectively, in lung epithelial cell models for the first time.

Results

Through scanning electron microscopy combined with bacterial infection experiments, we confirmed the ability of K. pneumoniae and M. smegmatis strains to form biofilm and cord factor out of the cell wall. M. smegmatis has stronger adhesion and intracellular retention ability, while K. pneumoniae is more likely to induce acute infection. These pathogens could stay and proliferate in lung epithelial cells and stimulate the secretion of specific cytokines and chemokines through a gene transcription regulator. M. smegmatis infection can promote crosstalk among epithelial cells and other immune cells in the lung from a very early stage by prompting the secretion of pro-inflammatory cytokines. Meanwhile, there were significant correlations between K. pneumonia infection and higher levels of interleukin-15 (IL-15), interleukin-1Rα (IL-1Rα), fibroblast growth factor (FGF) basic, and granulocyte colony-stimulating factor (G-CSF). At the same time, K. pneumonia infection also led to changes in the expression of cytoskeletal proteins in epithelial cells.

Conclusions

Our results emphasized the immunoprotection and immunomodulation of lung epithelial cells against exogenous pathogenic microorganisms, indicating that different pathogens damaged the host through different strategies and induced varying innate immune responses. At the same time, they provided important clues and key immune factors for dealing with complicated pulmonary infections.

Mycobacterium simiae Isolates Subtypes and Molecular Drug Susceptibility in Iran

Background: Despite the clinical and epidemiological importance of Mycobacterium simiae worldwide, including in Iran, there is no clear and effective treatment regimen for M. simiae and its different subtypes. Objectives: Concerning the superiority of molecular approaches, this study aims to identify the common M. simiae subtypes submitted to the National Reference Tuberculosis (TB) Laboratory of Iran and study the presence of drug resistance by molecular detection methods. Methods: We included sputum samples with M. simiae confirmation submitted to the National Reference TB Laboratory of Iran from May 2014 to May 2016. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was used for drug susceptibility testing (DST). Results: Among 7200 TB suspected patients, a total of 60 M. simiae cases belonging to subtype I were identified. All the included clinical isolates met the American Thoracic Society (ATS) and Infectious Diseases Society of America (IDSA) diagnostic criteria and were considered the disease’s causative pathogen. Males (58.33%), elderly (68.54%), and patients with a history of TB (51.42%) were shown to be more prone to infection with the disease. All clinical isolates of M. simiae were resistant to rifampin (RIF) and isoniazid (INH). Amikacin/kanamycin (AMK/KAN) and ciprofloxacin (CIP) susceptibility was found to be 91.66% and 88.33%, respectively. Conclusions: Subtype I was exclusively identified among M. simiae patients in Iran. Molecular detection of drug resistance suggests that amikacin/kanamycin and ciprofloxacin could be used to treat patients infected with M. simiae subtype I.

Clinical characteristics and imaging features of patients with nontuberculous mycobacteria in a tertiary care center

Background

Non-tuberculous mycobacteria (NTM) are ubiquitous organisms that occasionally causes invasive diseases in humans, but they are under-reported in Saudi Arabia. We aimed to describe NTM infections and apply the American Thoracic Society/Infectious Diseases Society of America ATS/IDSA criteria.

Method

Positive laboratory reports for NTM between January 2006 and December 2017 were retrospectively reviewed, and then classified into respiratory and non-respiratory specimens. ATS/IDSA criteria were applied to all respiratory specimens. Host status, clinical presentation, species identification, imaging, treatment, and outcome data were collected using a standardized form and analyzed. Cases with duplication or incomplete data were excluded.

Results

183 unique patients with positive NTM culture were included. Median age was 52 years and males represented 59%. Majority of cases were in the respiratory specimens group (n = 146), of which only 15 cases have met the ATS/IDSA criteria. Overall, cases were primarily known to have non-immunocompromising condition but 27% had either an active malignancy (n = 35), HIV (n = 13), or primary immunodeficiency (n = 8). 68.3% of cases presented with respiratory symptoms with or without fever. Among the identified NTM species (51.9%), slowly growing NTM were predominant. Anti-NTM therapy was provided in only 22.4% of this cohort. Death was documented only in 5 cases; all were in the respiratory group and were not treated.

Conclusion

Though uncommon to isolate, only one in every ten respiratory NTM isolates was found potentially true pathogen in a single center in Saudi Arabia. Future studies on NTM prevalence in Saudi Arabia are recommended.

Pulmonary non-tuberculous mycobacterial infections: current state and future management

Currently, there is a trend of increasing incidence in pulmonary non-tuberculous mycobacterial infections (PNTM) together with a decrease in tuberculosis (TB) incidence, particularly in developed countries. The prevalence of PNTM in underdeveloped and developing countries remains unclear as there is still a lack of detection methods that could clearly diagnose PNTM applicable in these low-resource settings. Since non-tuberculous mycobacteria (NTM) are environmental pathogens, the vicinity favouring host-pathogen interactions is known as important predisposing factor for PNTM. The ongoing changes in world population, as well as socio-political and economic factors, are linked to the rise in the incidence of PNTM. Development is an important factor for the improvement of population well-being, but it has also been linked, in general, to detrimental environmental consequences, including the rise of emergent (usually neglected) infectious diseases, such as PNTM. The rise of neglected PNTM infections requires the expansion of the current efforts on the development of diagnostics, therapies and vaccines for mycobacterial diseases, which at present, are mainly focused on TB. This review discuss the current situation of PNTM and its predisposing factors, as well as the efforts and challenges for their control.

TBAJ-876, a 3,5-Dialkoxypyridine Analogue of Bedaquiline, Is Active against Mycobacterium abscessus

Lung disease caused by Mycobacterium abscessus is very difficult to cure, and treatment failure rates are high. The antituberculosis drug bedaquiline (BDQ) is used as salvage therapy against this dreadful disease. However, BDQ is highly lipophilic, displays a long terminal half-life, and presents a cardiotoxicity liability associated with QT interval prolongation. Recent medicinal chemistry campaigns resulted in the discovery of 3,5-dialkoxypyridine analogues of BDQ which are less lipophilic, have higher clearance, and display lower cardiotoxic potential.

Lung disease caused by Mycobacterium abscessus is very difficult to cure, and treatment failure rates are high. The antituberculosis drug bedaquiline (BDQ) is used as salvage therapy against this dreadful disease. However, BDQ is highly lipophilic, displays a long terminal half-life, and presents a cardiotoxicity liability associated with QT interval prolongation. Recent medicinal chemistry campaigns resulted in the discovery of 3,5-dialkoxypyridine analogues of BDQ which are less lipophilic, have higher clearance, and display lower cardiotoxic potential. TBAJ-876, a clinical development candidate of this series, shows attractive in vitro antitubercular activity and efficacy in a murine tuberculosis model. Here, we asked whether TBAJ-876 is active against M. abscessus. TBAJ-876 displayed submicromolar in vitro activity against reference strains representing the three subspecies of M. abscessus and against a collection of clinical isolates. Drug-drug potency interaction studies with commonly used anti-M. abscessus antibiotics showed no antagonistic effects, suggesting that TBAJ-876 could be coadministered with currently used drugs. Efficacy studies, employing a mouse model of M. abscessus infection, demonstrated potent activity in vivo. In summary, we demonstrate that TBAJ-876 shows attractive in vitro and in vivo activities against M. abscessus, similar to its BDQ parent. This suggests that next-generation BDQ, with improved tolerability and pharmacological profiles, may be useful for the treatment of M. abscessus lung disease in addition to the treatment of tuberculosis.

Mycobacterium smegmatis causing a granulomatous cardiomediastinal mass

Non-tuberculous mycobacterial species are uncommon human pathogens. They are divided into slow and rapid growing mycobacteria (RGM) with Mycobacterium smegmatis group as an uncommon pathogen among the RGM.

A 19 years old male presented with a 1 month history of dyspnea, orthopnea, unintentional weight loss, palpitation, flu-like symptoms and dry cough. Physical examination revealed tachycardia, distended superficial chest veins with a decrease in breath sounds at the right lower lung with fine crepitations. CT of the chest showed a large anterior mediastinal mass infiltrating the pericardium and three chambers of the myocardium that was confirmed using echocardiography. Despite negative workup for tuberculosis, the patient was treated successfully using first-line anti-TB treatment, which was begun before the tissue culture grew M. smegmatis.

To our knowledge, this is the first case in the literature of M. smegmatis infection mimicking cardiomediastinal tuberculoma, and RGM should be suspected in similar presentations with negative TB workup, even in an immunocompetent patient. This is also the first patient to be treated using only first-line anti-tuberculous treatment successfully in the literature.

Phytochemical analysis and evaluation of antioxidant and antimycobacterial activity of Colletia paradoxa from Brazil

Colletia paradoxa (Spreng.) Esc. (Rhamnaceae, Colletieae) is a medicinal plant, threatened with extinction in Brazil, presenting great morphological variability. Our objective is to investigate the phytochemical components, antioxidant capacity and antimycobacterial activity of different morphotypes of C. paradoxa in different environments. For this, the crude extract of the leaves and branches of the individuals sampled was used. The elimination capacity of the free radicals was determined by the DPPH method, the antimycobacterial activity by the broth microdilution method and the phenolic content by the spectrophotometric method using the Folin-Ciocalteu reagent and by HPLC. The extracts of C. paradoxa and its morphotypes showed significant amounts of phenolic compounds, including quercetin, quercitrin and rutin, besides considerable antioxidant and antimycobacterial activity No connection was detected between the phytochemical composition and different morphotypes of C. paradoxa.

Carbonic Anhydrase Inhibitors as Novel Drugs against Mycobacterial β-Carbonic Anhydrases: An Update on In Vitro and In Vivo Studies

Mycobacteria cause a variety of diseases, such as tuberculosis, leprosy, and opportunistic diseases in immunocompromised people. The treatment of these diseases is problematic, necessitating the development of novel treatment strategies. Recently, β-carbonic anhydrases (β-CAs) have emerged as potential drug targets in mycobacteria. The genomes of mycobacteria encode for three β-CAs that have been cloned and characterized from Mycobacterium tuberculosis (Mtb) and the crystal structures of two of the enzymes have been determined. Different classes of inhibitor molecules against Mtb β-CAs have subsequently been designed and have been shown to inhibit these mycobacterial enzymes in vitro. The inhibition of these centrally important mycobacterial enzymes leads to reduced growth of mycobacteria, lower virulence, and impaired biofilm formation. Thus, the inhibition of β-CAs could be a novel approach for developing drugs against the severe diseases caused by pathogenic mycobacteria. In the present article, we review the data related to in vitro and in vivo inhibition studies in the field.

Sulfamethoxazole derivatives complexed with metals: a new alternative against biofilms of rapidly growing mycobacteria

Biofilms are considered important sources of infections on biomedical surfaces, and most infections involving biofilm formation are associated with medical device implants. Therefore, there is an urgent need for new antimicrobial compounds that can combat microbial resistance associated with biofilm formation. In this context, this work aimed to evaluate the antibiofilm action of sulfamethoxazole complexed with Au, Cd, Cu, Ni and Hg on rapidly growing mycobacteria (RGM), as well as to evaluate their safety through cytotoxic assays. The results demonstrate potentiation of the novel compounds in antibiofilm activity, mainly in the complex with Au, which was able to completely inhibit biofilm formation and had the capacity to destroy the biofilm at all the concentrations tested. All cytotoxic data suggest that the majority of sulfamethoxazole metallic derivatives are antimicrobial alternatives, as well as safe molecules, which could be used as potential therapeutic agents for bacterial and biofilm elimination.

Global Environmental Nontuberculous Mycobacteria and Their Contemporaneous Man-Made and Natural Niches

Seminal microbiological work of environmental nontuberculous mycobacteria (NTM) includes the discovery that NTM inhabit water distribution systems and soil, and that the species of NTM found are geographically diverse. It is likely that patients acquire their infections from repeated exposures to their environments, based on the well-accepted paradigm that water and soil bioaerosols - enriched for NTM - can be inhaled into the lungs. Support comes from reports demonstrating NTM isolated from the lungs of patients are genetically identical to NTM found in their environment. Well documented sources of NTM include peat-rich soils, natural waters, drinking water, hot water heaters, refrigerator taps, catheters, and environmental amoeba. However, NTM have also been recovered in biofilms from ice machines, heated nebulizers, and heater-cooler units, as well as seat dust from theaters, vacuum cleaners, and cobwebs. New studies on the horizon aim to significantly expand the current knowledge of environmental NTM niches in order to improve our current understanding of the specific ecological factors driving the emergence of NTM lung disease. Specifically, the Hawaiian Island environment is currently being studied as a model to identify other point sources of exposure as it is the U.S. state with the highest number of NTM lung disease cases. Because of its geographic isolation and unique ecosystem, the Hawaiian environment is being probed for correlative factors that may promote environmental NTM colonization.