Accelerated multiple-quantum-filtered sodium magnetic resonance imaging using compressed sensing at 7 T.

PURPOSE: Multiple-quantum-filtered (MQF) sodium magnetic resonance imaging (MRI), such as enhanced single-quantum and triple-quantum-filtered imaging of 23Na (eSISTINA), enables images to be weighted towards restricted sodium, a promising biomarker in clinical practice, but often suffers from clinically infeasible acquisition times and low image quality. This study aims to mitigate the above limitation by implementing a novel eSISTINA sequence at 7 T with the application of compressed sensing (CS) to accelerate eSISTINA acquisitions without a noticeable loss of information. METHODS: A novel eSISTINA sequence with a 3D spiral-based sampling scheme was implemented at 7 T for the application of CS. Fully sampled datasets were obtained from one phantom and ten healthy subjects, and were then retrospectively undersampled by various undersampling factors. CS undersampled reconstructions were compared to fully sampled and undersampled nonuniform fast Fourier transform (NUFFT) reconstructions. Reconstruction performance was evaluated based on structural similarity (SSIM), signal-to-noise ratio (SNR), weightings towards total and compartmental sodium, and in vivo quantitative estimates. RESULTS: CS-based phantom and in vivo images have less noise and better structural delineation while maintaining the weightings towards total, non-restricted (predominantly extracellular), and restricted (primarily intracellular) sodium. CS generally outperforms NUFFT with a higher SNR and a better SSIM, except for the SSIM in TQ brain images, which is likely due to substantial noise contamination. CS enables in vivo quantitative estimates with <15% errors at an undersampling factor of up to two. CONCLUSIONS: Successful implementation of an eSISTINA sequence with an incoherent sampling scheme at 7 T was demonstrated. CS can accelerate eSISTINA by up to twofold at 7 T with reduced noise levels compared to NUFFT, while maintaining major structural information, reasonable weightings towards total and compartmental sodium, and relatively reliable in vivo quantification. The associated reduction in acquisition time has the potential to facilitate the clinical applicability of MQF sodium MRI.

A single-center observational study on long-term neurodevelopmental outcomes in children with tuberous sclerosis complex.

BACKGROUND: Tuberous sclerosis complex (TSC) is a rare multisystem disorder caused by mutations in the TSC1 or TSC2 gene. More than 90% of patients with TSC develop neurological and/or neuropsychiatric manifestations. The aim of the present study was to determine the developmental and cognitive long-term outcomes of pediatric TSC patients. METHODS: This cross-sectional, monocenter study included pediatric TSC patients who received multidisciplinary long-term care with a last visit between 2005 and 2019. Neurological manifestations and cognitive development (BSID, K-ABC) were analyzed in relation to age and type of mutation. RESULTS: Thirty-five patients aged 13.5 ± 7.8 years were included in the study. Diagnosis was confirmed genetically in 65.7% of patients (TSC1, 26.1%; TSC2, 65.2%; NMI, 8.7%). Mean age at diagnosis was 1.3 ± 3.5 years; 74.3% of the patients had been diagnosed within the first year of life due to seizures (62.9%) or/and cardiac rhabdomyomas (28.6%). The most common TSC manifestations included structural brain lesions (cortical tubers, 91.4%; subependymal nodules, 82.9%), epilepsy (85.7%), and cardiac rhabdomyomas (62.9%). Mean age at seizure onset was 1.5 ± 2.3 years, with onset in 80.0% of patients within the first two years of life. Infantile spasms, which were the first seizure type in 23.3% of the patients, developed earlier (0.6 ± 0.4 years) than focal seizures (1.8 ± 2.5 years). Refractory epilepsy was present in 21 (70.0%) patients, mild or severe intellectual impairment in 66.6%, and autism spectrum disorders in 11.4%. Severe cognitive impairment (33.3%) was significantly associated with epilepsy type and age at seizure onset (p < 0.05). CONCLUSIONS: The results emphasized the phenotypic variability of pediatric-onset TSC and the high rate of neurological and neuropsychiatric morbidity. Early-onset refractory epilepsy was associated with impaired cognitive development. Children of all ages with TSC require multidisciplinary long-term care and individual early-intervention programs.

Two Decades of Brain Tumour Imaging with O-(2-[18F]fluoroethyl)-L-tyrosine PET: The Forschungszentrum Jülich Experience.

O-(2-[18F]fluoroethyl)-L-tyrosine (FET) is a widely used amino acid tracer for positron emission tomography (PET) imaging of brain tumours. This retrospective study and survey aimed to analyse our extensive database regarding the development of FET PET investigations, indications, and the referring physicians' rating concerning the role of FET PET in the clinical decision-making process. Between 2006 and 2019, we performed 6534 FET PET scans on 3928 different patients against a backdrop of growing demand for FET PET. In 2019, indications for the use of FET PET were as follows: suspected recurrent glioma (46%), unclear brain lesions (20%), treatment monitoring (19%), and suspected recurrent brain metastasis (13%). The referring physicians were neurosurgeons (60%), neurologists (19%), radiation oncologists (11%), general oncologists (3%), and other physicians (7%). Most patients travelled 50 to 75 km, but 9% travelled more than 200 km. The role of FET PET in decision-making in clinical practice was evaluated by a questionnaire consisting of 30 questions, which was filled out by 23 referring physicians with long experience in FET PET. Fifty to seventy per cent rated FET PET as being important for different aspects of the assessment of newly diagnosed gliomas, including differential diagnosis, delineation of tumour extent for biopsy guidance, and treatment planning such as surgery or radiotherapy, 95% for the diagnosis of recurrent glioma, and 68% for the diagnosis of recurrent brain metastases. Approximately 50% of the referring physicians rated FET PET as necessary for treatment monitoring in patients with glioma or brain metastases. All referring physicians stated that the availability of FET PET is essential and that it should be approved for routine use. Although the present analysis is limited by the fact that only physicians who frequently referred patients for FET PET participated in the survey, the results confirm the high relevance of FET PET in the clinical diagnosis of brain tumours and support the need for its approval for routine use.

Compressed Sensing in Sodium Magnetic Resonance Imaging: Techniques, Applications, and Future Prospects.

Sodium (23 Na) yields the second strongest nuclear magnetic resonance (NMR) signal in biological tissues and plays a vital role in cell physiology. Sodium magnetic resonance imaging (MRI) can provide insights into cell integrity and tissue viability relative to pathologies without significant anatomical alternations, and thus it is considered to be a potential surrogate biomarker that provides complementary information for standard hydrogen (1 H) MRI in a noninvasive and quantitative manner. However, sodium MRI suffers from a relatively low signal-to-noise ratio and long acquisition times due to its relatively low NMR sensitivity. Compressed sensing-based (CS-based) methods have been shown to accelerate sodium imaging and/or improve sodium image quality significantly. In this manuscript, the basic concepts of CS and how CS might be applied to improve sodium MRI are described, and the historical milestones of CS-based sodium MRI are briefly presented. Representative advanced techniques and evaluation methods are discussed in detail, followed by an expose of clinical applications in multiple anatomical regions and diseases as well as thoughts and suggestions on potential future research prospects of CS in sodium MRI. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 1.

Putaminal y-Aminobutyric Acid Modulates Motor Response to Dopaminergic Therapy in Parkinson's Disease.

BACKGROUND: Motor response to dopaminergic therapy is a characteristic of patients with Parkinson's disease (PD). Whether nondopaminergic neurotransmitters contribute to treatment response is uncertain. OBJECTIVES: The aim of this study is to determine whether putaminal y-aminobutyric acid (GABA) levels are associated with dopaminergic motor response. METHODS: We assessed putaminal GABA levels in 19 PD patients and 13 healthy controls (HCs) utilizing ultra-high field proton magnetic resonance spectroscopy. Motor performance was evaluated using the Movement Disorder Society-Unified Parkinson's Disease Rating Scale, Part III, in the ON and OFF states. Statistical analysis comprised group comparisons, correlation analysis, and multiple linear regression. RESULTS: In PD, GABA levels were significantly higher compared to HCs (1.50 ± 0.26 mM vs. 1.26 ± 0.31 mM, P = 0.022). Furthermore, GABA levels were independent predictors of absolute and relative dopaminergic treatment response. CONCLUSIONS: Our findings indicate that elevated putaminal GABA levels are associated with worse dopaminergic response in PD, emphasizing the essential role of nondopaminergic neurotransmitters in motor response. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Iterative Restoration of the Fringe Phase (REFRASE) for QSM.

In quantitative susceptibility mapping (QSM), reconstructed results can be critically biased by misinterpreted or missing phase data near the edges of the brain support originating from the non-local relationship between field and susceptibility. These data either have to be excluded or corrected before further processing can take place. To address this, our iterative restoration of the fringe phase (REFRASE) approach simultaneously enhances the accuracy of multi-echo phase data QSM maps and the extent of the area available for evaluation. Data loss caused by strong local phase gradients near the surface of the brain support is recovered within the original phase data using harmonic and dipole-based fields extrapolated from a robust support region toward an extended brain mask. Over several iterations, phase data are rectified prior to the application of further QSM processing steps. The concept is successfully validated on numerical phantoms and brain scans from a cohort of volunteers. The increased extent of the mask and improved numerical stability within the segmented globus pallidus confirm the efficacy of the presented method in comparison to traditional evaluation.

Relaxometry and quantification in sodium MRI of cerebral gliomas: A FET-PET and MRI small-scale study.

Sodium MRI is a promising method for assessing the metabolic properties of brain tumours. In a recent study, a strong relationship between semi-quantitative abnormalities in sodium MRI and the mutational status of the isocitrate dehydrogenase enzyme (IDH) with untreated cerebral gliomas was observed. Here, sodium relaxometry in brain tumour tissue was investigated in relation to molecular markers in order to reveal quantitative sodium tissue parameters and the differences between healthy tissue and brain tumour. The previous semi-quantitative approach is extended by use of suitable relaxometry methods accompanied by numerical simulation to achieve detailed quantitative analysis of intra- and extracellular sodium concentration using an enhanced SISTINA sequence at 4 T. Using optimised techniques, biexponential sodium relaxation times in tumour (T*2f , T*2s ) and in healthy contralateral brain tissue (T*2f,CL , T*2s,CL ) were estimated in 10 patients, along with intracellular sodium molar fractions (χ, χCL ), volume fractions (η, ηCL ) and concentrations (ρin , ρin,CL ). The total sodium tissue concentrations (ρT , ρT,CL ) were also estimated. The ratios T*2f /T*2f,CL (P = .05), η/ηCL (P = .02) and χ/χCL (P = .02) were significantly lower in IDH mutated than in IDH wildtype gliomas (n = 4 and n = 5 patients, respectively). The Wilcoxon rank-sum test was used to compare sodium MRI parameters in patients with and without IDH mutation. Thus, quantitative analysis of relaxation rates, intra- and extracellular sodium concentrations, intracellular molar and volume fractions based on enhanced SISTINA confirmed a relationship between abnormalities in sodium parameters and the IDH mutational status in cerebral gliomas, hence catering for the potential to provide further insights into the status of the disease.

An in vivo multimodal feasibility study in a rat brain tumour model using flexible multinuclear MR and PET systems.

BACKGROUND: In addition to the structural information afforded by 1H MRI, the use of X-nuclei, such as sodium-23 (23Na) or phosphorus-31 (31P), offers important complementary information concerning physiological and biochemical parameters. By then combining this technique with PET, which provides valuable insight into a wide range of metabolic and molecular processes by using of a variety of radioactive tracers, the scope of medical imaging and diagnostics can be significantly increased. While the use of multimodal imaging is undoubtedly advantageous, identifying the optimal combination of these parameters to diagnose a specific dysfunction is very important and is advanced by the use of sophisticated imaging techniques in specific animal models. METHODS: In this pilot study, rats with intracerebral 9L gliosarcomas were used to explore a combination of sequential multinuclear MRI using a sophisticated switchable coil set in a small animal 9.4 T MRI scanner and, subsequently, a small animal PET with the tumour tracer O-(2-[18F]-fluoroethyl)-L-tyrosine ([18F]FET). This made it possible for in vivo multinuclear MR-PET experiments to be conducted without compromising the performance of either multinuclear MR or PET. RESULTS: High-quality in vivo images and spectra including high-resolution 1H imaging, 23Na-weighted imaging, detection of 31P metabolites and [18F]FET uptake were obtained, allowing the characterisation of tumour tissues in comparison to a healthy brain. It has been reported in the literature that these parameters are useful in the identification of the genetic profile of gliomas, particularly concerning the mutation of the isocitrate hydrogenase gene, which is highly relevant for treatment strategy. CONCLUSIONS: The combination of multinuclear MR and PET in, for example, brain tumour models with specific genetic mutations will enable the physiological background of signal alterations to be explored and the identification of the optimal combination of imaging parameters for the non-invasive characterisation of the molecular profile of tumours.

Comparison of [18F]Fluoroethyltyrosine PET and Sodium MRI in Cerebral Gliomas: a Pilot Study.

PURPOSE: Positron emission tomography (PET) using O-(2-[18F]fluoroethyl)-L-tyrosine ([18F]FET) improves the diagnostics of cerebral gliomas compared with conventional magnetic resonance imaging (MRI). Sodium MRI is an evolving method to assess tumor metabolism. In this pilot study, we explored the relationship of [18F]FET-PET and sodium MRI in patients with cerebral gliomas in relation to the mutational status of the enzyme isocitrate dehydrogenase (IDH). PROCEDURES: Ten patients with untreated cerebral gliomas and one patient with a recurrent glioblastoma (GBM) were investigated by dynamic [18F]FET-PET and sodium MRI using an enhanced simultaneous single-quantum- and triple-quantum-filtered imaging of 23Na (SISTINA) sequence to estimate total (NaT), weighted non-restricted (NaNR, mainly extracellular), and restricted (NaR, mainly intracellular) sodium in tumors and normal brain tissue. [18F]FET uptake and sodium parameters in tumors with a different IDH mutational status were compared. After biopsy or resection, histology and the IDH mutational status were determined neuropathologically. RESULTS: NaT (p = 0.05), tumor-to-brain ratios (TBR) of NaT (p = 0.02), NaNR (p = 0.003), and the ratio of NaT/NaR (p < 0.001) were significantly higher in IDH-mutated than in IDH-wild-type gliomas (n = 5 patients each) while NaR was significantly lower in IDH-mutated gliomas (p = 0.01). [18F]FET parameters (TBR, time-to-peak) were not predictive of IDH status in this small cohort of patients. There was no obvious relationship between sodium distribution and [18F]FET uptake. The patient with a recurrent GBM exhibited an additional radiation injury with strong abnormalities in sodium MRI. CONCLUSIONS: Sodium MRI appears to be more strongly related to the IDH mutational status than are [18F]FET-PET parameters. A further evaluation of the combination of the two methods in a larger group of high- and low-grade gliomas seems promising.

Correlation of quantitative conductivity mapping and total tissue sodium concentration at 3T/4T.

PURPOSE: To investigate the correlation between electrical conductivity and sodium concentration, both measured in vivo, in the human brain. METHODS: Conductivity measurements were performed on samples with different sodium (Na+ ) and agarose concentrations using a dielectric probe, and the correlation between conductivity and Na+ content was evaluated. Subsequently, brain conductivity and total Na+ content maps were measured in 8 healthy subjects using phase-based MREPT and sodium MRI, respectively. After co-registration and spatial normalization to the 1 mm 152 MNI brain atlas, the relationship between conductivity and tissue sodium concentration (TSC) was examined within different brain regions. RESULTS: The conductivities of agarose gels increased linearly with NaCl concentration, while remaining almost independent of agarose content. When measured in healthy subjects, conductivities showed positive correlation with total tissue sodium concentration (R = 0.39, P < 0.005). The same trend was found in gray matter (R = 0.36, P < 0.005) and in white matter (R = 0.28, P < 0.05). CONCLUSION: Tissue conductivity shows a positive correlation with total sodium concentration. Conductivity might serve as a novel technique to visualize the total tissue electrolyte concentration, although refinements in the consideration of e.g., tissue water content, would be necessary to improve the quantitative value.

Relaxometry and quantification in simultaneously acquired single and triple quantum filtered sodium MRI.

PURPOSE: Sodium imaging delivers valuable information about in vivo metabolism and pathophysiology. Image quantification can benefit the diagnosis and characterization of existing pathologies and the clinical course of a disease. An enhanced SISTINA sequence is proposed for sodium imaging and for the estimation of sodium tissue parameters for a 2-compartment model of the brain, such as relaxation times in intracellular space and tissue, intracellular volume fraction, and intracellular molar fraction. The aim of the research is to demonstrate how a 2-compartment model can be parameterized to sufficiently describe tissue sodium concentrations and dynamics by performing relaxometry with such a sequence. METHODS: Multiple quantum filtered sodium signals were detected using an enhanced SISTINA sequence (consisting of 3 consecutive RF pulses) by placing a readout train between the first and second RF pulse, and 1 after the third pulse. Semiautomatic segmentation using singular value decomposition and manual segmentation was applied to the images. RESULTS: Analysis was performed on 40 healthy volunteers in a 4T scanner, yielding bi-exponential relaxation times of brain tissue, intracellular sodium molar and volume fraction, intracellular sodium concentration, as well as sodium tissue concentration in the scope of a considered model. Two models with either purely mono-exponential or bi-exponential relaxing extracellular sodium were used with and without a potential contribution of triple quantum-filtered signal from extracellular space. CONCLUSION: An estimation of relaxation properties and concentrations limited to the assumed model is possible from a single sequence. The achieved results agree well with those reported in literature.

Design and use of a folded four-ring double-tuned birdcage coil for rat brain sodium imaging at 9.4 T.

A folded four-ring quadrature birdcage coil was designed and constructed with a double-tune configuration of an outer high-pass coil for 1H (400 MHz) and inner low-pass coil for 23Na (105.72 MHz at 9.4 T). The coil was evaluated on the bench and in the scanner, comparing its performance with that of single-tuned coils and a large four-ring coil. All coils were tuned and matched and the isolation between two quadrature ports was found to be better than -13.7 dB for 1H and -27 dB for 23Na. Signal-to-noise ratios (SNRs) were calculated and 23Na flip angle maps were acquired. 23Na SNR of the folded four-ring reached ∼93% of that obtained with the single-tuned coil. A set of in vivo1H and 23Na axial images to cover the whole rat brain were obtained. The performance of the folded four-ring coil and its benefit for 23Na imaging experiments have been demonstrated. This proposed four-ring coil could avoid length restrictions, e.g. the shoulders, by folding the outer rings vertically. This facilitates the construction of double-tuned four-ring birdcage coils just to fit the head, leading to higher filling factors and better SNR.

Imaging of sodium in the brain: a brief review.

Sodium-based MRI plays a vital role in the study of metabolism and can unveil valuable information about emerging and existing pathology--in particular in the human brain. Sodium is the second most abundant MR active nucleus in living tissue and, due to its quadrupolar nature, has magnetic properties not common to conventional proton MRI, which can reveal further insights, such as information on the compartmental distribution of intra- and extracellular sodium. Nevertheless, the use of sodium nuclei for imaging comes at the expense of a lower sensitivity and significantly reduced relaxation times, making in vivo sodium studies feasible only at high magnetic field strength and by the use of dedicated pulse sequences. Hybrid imaging combining sodium MRI and positron emission tomography (PET) simultaneously is a novel and promising approach to access information on dynamic metabolism with much increased, PET-derived specificity. Application of this new methodology is demonstrated herein using examples from tumour imaging.

Systematic review: microbial dysbiosis and nonalcoholic fatty liver disease.

BACKGROUND: The human intestinal microbiota is a key regulator of host metabolic and immune functions and alterations in the microbiome ('dysbiosis') have been implicated in several human diseases. Because of the anatomical links between the intestines and the liver, dysbiosis may also disrupt hepatic function and thereby contribute to the pathogenesis of nonalcoholic fatty liver disease (NAFLD). AIM: To perform a comprehensive review of the medical literature investigating associations between intestinal dysbiosis and NAFLD, with a particular emphasis on studies that characterise the microbiome in NAFLD. METHODS: We conducted a search of PubMed, Embase, and Web of Science using multiple search terms including: 'NAFLD, NASH, fatty liver, steatohepatitis' combined with 'metagenome, microbiom*, microbiota*, fecal flora, intestinal flora, gut bacteria'. Results were manually reviewed and studies selected based on relevance to intestinal microbiota and NAFLD. We also included studies that addressed potential mechanistic models of pathways linking the dysbiosis to NAFLD. RESULTS: Nine studies (five human and four animal models) were identified in our search that assessed associations between specific intestinal microbiota composition and NAFLD. We reviewed and summarised the results of additional investigations that more broadly addressed the mechanisms by which the microbiome may impact NAFLD pathogenesis. CONCLUSIONS: Investigations in humans and animals demonstrate associations between intestinal dysbiosis and NAFLD; however, causality has not been proven and mechanistic links require further delineation. As the field of microbiome research matures in techniques and study design, more detailed insights into NAFLD pathogenesis and its associations with the intestinal microbiota will be elucidated.

Evidence for the light hole in GaAs/AlGaAs quantum wells from optically-pumped NMR and Hanle curve measurements.

Optically-pumped (69)Ga NMR (OPNMR) and optically-detected measurements of polarized photoluminescence (Hanle curves) show a characteristic feature at the light hole-to-conduction band transition in a GaAs/AlxGa1-xAs multiple quantum well sample. OPNMR data are often depicted as a "profile" of the OPNMR integrated signal intensity plotted versus optical pumping photon energy. What is notable is the inversion of the sign of the measured (69)Ga OPNMR signals when optically pumping this light hole-to-conduction band energy in OPNMR profiles at multiple external magnetic fields (B0=4.7T and 3T) for both σ(+) and σ(-) irradiation. Measurements of Hanle curves at B0=0.5T of the same sample exhibit similar phase inversion behavior of the Hanle curves at the photon energy for light hole excitation. The zero-field value of the light-hole state in the quantum well can be predicted for the quantum well structure using the positions of each of these signal-inversion features, and the spin splitting term in the equation for the transition energy yields consistent values at 3 magnetic fields for the excitonic g-factor (g(ex)). This study demonstrates the application of OPNMR and optical measurements of the photoluminescence to detect the light hole transition in semiconductors.

Behavior of poly(glycerol sebacate) plugs in chronic tympanic membrane perforations.

The tympanic membrane (TM), separating the external and middle ear, consists of fibrous connective tissue sandwiched between epithelial layers. To treat chronic ear infections, tympanostomy drainage tubes are placed in surgically created holes in TMs which can become chronic perforations upon extrusion. Perforations are repaired using a variety of techniques, but are limited by morbidity, unsatisfactory closure rates, or minimal regeneration of the connective tissue. A more effective, minimally-invasive therapy is necessary to enhance the perforation closure rate. Current research utilizing decellularized or alignate materials moderately enhance closure but the native TM architecture is not restored. Poly(glycerol sebacate) (PGS) is a biocompatible elastomer which supports cell migration and enzymatically degrades in contact with vascularized tissue. PGS spool-shaped plugs were manufactured using a novel process. Using minimally invasive procedures, these elastomeric plugs were inserted into chronic chinchilla TM perforations. As previously reported, effective perforation closure occurred as both flange surfaces were covered by confluent cell layers; >90% of perforations were closed at 6-week postimplantation. This unique in vivo environment has little vascularized tissue. Consequently, PGS degradation was minimal over 16-week implantation, hindering regeneration of the TM fibrous connective tissue. PGS degradation must be enhanced to promote complete TM regeneration.

The potential for hydrocarbon biodegradation and production of extracellular polymeric substances by aerobic bacteria isolated from a Brazilian petroleum reservoir.

Extracellular polymeric substances (EPS) can contribute to the cellular degradation of hydrocarbons and have a huge potential for application in biotechnological processes, such as bioremediation and microbial enhanced oil recovery (MEOR). Four bacterial strains from a Brazilian petroleum reservoir were investigated for EPS production, emulsification ability and biodegradation activity when hydrocarbons were supplied as substrates for microbial growth. Two strains of Bacillus species had the highest EPS production when phenanthrene and n-octadecane were offered as carbon sources, either individually or in a mixture. While Pseudomonas sp. and Dietzia sp., the other two evaluated strains, had the highest hydrocarbon biodegradation indices, EPS production was not detected. Low EPS production may not necessarily be indicative of an absence of emulsifier activity, as indicated by the results of a surface tension reduction assay and emulsification indices for the strain of Dietzia sp. The combined results gathered in this work suggest that a microbial consortium consisting of bacteria with interdependent metabolisms could thrive in petroleum reservoirs, thus overcoming the limitations imposed on each individual species by the harsh conditions found in such environments.

Proposal to elevate Mycobacterium avium complex ITS sequevar MAC-Q to Mycobacterium vulneris sp. nov.

The Mycobacterium avium complex (MAC) consists of four recognized species, Mycobacterium avium, Mycobacterium colombiense, Mycobacterium intracellulare and Mycobacterium chimaera, and a variety of other strains that may be members of undescribed taxa. We report on two isolates of a scotochromogenic, slowly growing, non-tuberculous Mycobacterium species within the M. avium complex from a lymph node and an infected wound after a dogbite of separate patients in The Netherlands. The extrapulmonary infections in immunocompetent patients suggested a high level of virulence. These isolates were characterized by a unique nucleotide sequence in the 16S rRNA gene, 99% similar to Mycobacterium colombiense, and the MAC-Q 16S-23S internal transcribed spacer (ITS) sequence. Sequence analyses of the hsp65 gene revealed 97% similarity to M. avium. The rpoB gene sequence was 98% similar to M. colombiense. Phenotypically, the scotochromogenicity, positive semi-quantitative catalase and heat-stable catalase tests, negative tellurite reductase and urease tests and susceptibility to hydroxylamine and oleic acid set these isolates apart from related species. High-performance liquid chromatography analysis of cell-wall mycolic acid content revealed a unique pattern, related to that of M. avium and M. colombiense. Together, these findings supported a separate species status within the Mycobacterium avium complex. We propose elevation of scotochromogenic M. avium complex strains sharing this 16S gene and MAC-Q ITS sequence to separate species status, for which the name Mycobacterium vulneris sp. nov. is proposed. The type strain is NLA000700772T (=DSM 45247T=CIP 109859T).

Carbon pools and isotopic trends in a hypersaline cyanobacterial mat.

The fine-scale depth distribution of major carbon pools and their stable carbon isotopic signatures (delta(13)C) were determined in a cyanobacterial mat (Salin-de-Giraud, Camargue, France) to study early diagenetic alterations and the carbon preservation potential in hypersaline mat ecosystems. Particular emphasis was placed on the geochemical role of extracellular polymeric substances (EPS). Total carbon (C(tot)), organic carbon (C(org)), total nitrogen (N(tot)), total hydrolysable amino acids (THAA), carbohydrates, cyanobacteria-derived hydrocarbons (8-methylhexadecane, n-heptadec-5-ene, n-heptadecane) and EPS showed highest concentrations in the top millimetre of the mat and decreased with depth. The hydrocarbons attributed to cyanobacteria showed the strongest decrease in concentration with depth. This correlated well with the depth profiles of oxygenic photosynthesis and oxygen, which were detected in the top 0.6 and 1.05 mm, respectively, at a high down-welling irradiance (1441 micromol photons m(-2) s(-1)). At depths beneath the surface layer, the C(org) was composed mainly of amino acids and carbohydrates. A resistance towards microbial degradation could have resulted from interactions with diverse functional groups present in biopolymers (EPS) and with minerals deposited in the mat. A (13)C enrichment with depth for the total carbon pool (C(tot)) was observed, with delta(13)C values ranging from -16.3 per thousand at the surface to -11.3 per thousand at 9-10 mm depth. Total lipids depicted a delta(13)C value of -17.2 per thousand in the top millimetre and then became depleted in (13)C with depth (-21.7 to -23.3 per thousand). The delta(13)C value of EPS varied only slightly with depth (-16.1 to -17.3 per thousand) and closely followed the delta(13)C value of C(org) at depths beneath 4 mm. The EPS represents an organic carbon pool of preservation potential during early stages of diagenesis in recent cyanobacterial mats as a result of a variety of possible interactions. Their analyses might improve our understanding of fossilized microbial remains from mat ecosystems.

An overview of the integration of ozone systems in biological treatment steps.

Despite the well-known potential and performance of combined biological and ozonation processes for wastewater treatment, only few full-scale applications are published. Beside the synergistic effects of such process combination, which lead to oxidation of recalcitrant and inhibitory compounds or intermediates by enhancement of their biodegradability, the key for raising applicability is the improvement of the ozonation efficiency. An overview about the history and progress of full-scale applications, which deals with combined ozonation and biological treatment is given. Recently more than 40 applications exist, but many of them are not published. Therefore, a couple of selected not yet published applications have been mentioned in this paper. Landfill leachate and industrial wastewater treatment were mostly applicated, while treatment of municial wastewater treatment plant (WWTP) effluents are of increasing interest due to several advantages such as disinfection, decolourisation and removal of persistent dissolved organic carbon (DOC) for water re-use and groundwater recharge.