Decoding Microbial Responses to Ammonia Shock Loads in Biogas Reactors through Metagenomics and Metatranscriptomics.

The presence of elevated ammonia levels is widely recognized as a significant contributor to process inhibition in biogas production, posing a common challenge for biogas plant operators. The present study employed a combination of biochemical, genome-centric metagenomic and metatranscriptomic data to investigate the response of the biogas microbiome to two shock loads induced by single pulses of elevated ammonia concentrations (i.e., 1.5 g NH4+/LR and 5 g NH4+/LR). The analysis revealed a microbial community of high complexity consisting of 364 Metagenome Assembled Genomes (MAGs). The hydrogenotrophic pathway was the primary route for methane production during the entire experiment, confirming its efficiency even at high ammonia concentrations. Additionally, metatranscriptomic analysis uncovered a metabolic shift in the methanogens Methanothrix sp. MA6 and Methanosarcina flavescens MX5, which switched their metabolism from the acetoclastic to the CO2 reduction route during the second shock. Furthermore, multiple genes associated with mechanisms for maintaining osmotic balance in the cell were upregulated, emphasizing the critical role of osmoprotection in the rapid response to the presence of ammonia. Finally, this study offers insights into the transcriptional response of an anaerobic digestion community, specifically focusing on the mechanisms involved in recovering from ammonia-induced stress.

Magnetite Alters the Metabolic Interaction between Methanogens and Sulfate-Reducing Bacteria.

It is known that the presence of sulfate decreases the methane yield in the anaerobic digestion systems. Sulfate-reducing bacteria can convert sulfate to hydrogen sulfide competing with methanogens for substrates such as H2 and acetate. The present work aims to elucidate the microbial interactions in biogas production and assess the effectiveness of electron-conductive materials in restoring methane production after exposure to high sulfate concentrations. The addition of magnetite led to a higher methane content in the biogas and a sharp decrease in the level of hydrogen sulfide, indicating its beneficial effects. Furthermore, the rate of volatile fatty acid consumption increased, especially for butyrate, propionate, and acetate. Genome-centric metagenomics was performed to explore the main microbial interactions. The interaction between methanogens and sulfate-reducing bacteria was found to be both competitive and cooperative, depending on the methanogenic class. Microbial species assigned to the Methanosarcina genus increased in relative abundance after magnetite addition together with the butyrate oxidizing syntrophic partners, in particular belonging to the Syntrophomonas genus. Additionally, Ruminococcus sp. DTU98 and other species assigned to the Chloroflexi phylum were positively correlated to the presence of sulfate-reducing bacteria, suggesting DIET-based interactions. In conclusion, this study provides new insights into the application of magnetite to enhance the anaerobic digestion performance by removing hydrogen sulfide, fostering DIET-based syntrophic microbial interactions, and unraveling the intricate interplay of competitive and cooperative interactions between methanogens and sulfate-reducing bacteria, influenced by the specific methanogenic group.

Gender, racial and ethnic disparities in index hospitalization operations for symptomatic carotid stenosis in Texas hospitals.

BACKGROUND: Recent literature and societal recommendations support early revascularization of symptomatic carotid patients over the traditional six-week period. Nonetheless, the timing of these interventions can vary widely among populations. The goal of this study is to identify any factors influencing carotid revascularization during the index hospitalization for patients with symptomatic disease. METHODS: The Texas Department of State Health Services database was queried to identify all patients > 45 years old admitted to nonfederal Texas Hospitals between 2009 to 2013 with an admission diagnosis of carotid artery stenosis and either transient ischemic attack (TIA), cerebrovascular accident (CVA), or amaurosis fugax. Diagnoses codes and demographic data were also used to adjust for clinical, social, and demographic factors (including area of residence and treatment). Descriptive statistics and multivariable logistic regression were used to identify significant factors for index admission revascularization. RESULTS: A total of 29,046 symptomatic patients were identified among the 153,484 patients who had an eligible admission diagnosis. This included 16,244 (55.9%) males and 12,802 (44.1%) females. Only 4,594 (15.8%) patients were revascularized during the index hospitalization. The majority of these patients presented with amaurosis (OR 5.58; 95% CI 4.84-6.44) instead of CVAs (OR 0.48; 95% CI 0.45-0.51) or TIAs . Adjusting for hospital volume, insurance coverage, residence, and other clinical factors, rates of index admission carotid intervention remained significantly lower for women (OR 0.85; 95% CI 0.79-0.91), persons categorized as black (OR 0.60; 95% CI 0.53-0.69), and persons categorized as Hispanic (OR 0.77; 95% CI 0.70-0.86). CONCLUSIONS: Gender, race and ethnicity appear to correlate with rates of carotid intervention at index hospitalization despite thorough risk adjustment for clinical, social and demographic factors. Efforts should be directed towards reducing these disparities.

Thermophilic anaerobic digestion of olive mill wastewater in an upflow packed bed reactor: Evaluation of 16S rRNA amplicon sequencing for microbial analysis.

Olive mill wastewater, a by-product of olive oil production after the operation of three-phase decanters, was used in a thermophilic anaerobic digester targeting efficient bioconversion of its organic load into biogas. An active anaerobic inoculum originating from a mesophilic reactor, was acclimatized under thermophilic conditions and was filled into a high-rate upflow packed bed reactor. Its performance was tested towards the treatment efficacy of olive mill wastewater under thermophilic conditions reaching the minimum hydraulic retention time of 4.2 d with promising results. As analysis of the microbial communities is considered to be the key for the development of anaerobic digestion optimization techniques, the present work focused on characterizing the microbial community and its variation during the reactor's runs, via 16S rRNA amplicon sequencing. Identification of new microbial species and taxonomic groups determination is of paramount importance as these representatives determine the bioprocess outcome. The current study results may contribute to further olive mill wastewater exploitation as a potential source for efficient biogas production.

Patient information sources when facing repair of abdominal aortic aneurysm.

OBJECTIVE: Shared medical decision making is most important when there are competing options for repair such as in treatment of abdominal aortic aneurysm (AAA). We sought to understand the sources of patients' pre-existing knowledge about AAA to better inform treating physicians about patients' needs for preoperative counseling. METHODS: We performed a multicenter survey of patients facing AAA repair at 20 Veterans Affairs hospitals across the United States as part of the Preferences for Open Versus Endovascular Repair of AAA study. A validated survey instrument was administered to examine the sources of information available and commonly used by patients to learn about their repair options. The survey was administered by study personnel before the patient had any interaction with the vascular surgeon because survey data were collected before the vascular clinic visit. RESULTS: Preliminary analysis of data from 99 patients showed that our cohort was primarily male (99%) and elderly (mean age 73 years). Patients commonly had a history of hypertension (86%), prior myocardial infarction (32%), diabetes (32%), and were overweight (58%). Patients arrived at their surgeon's office appointment with limited information. A majority of patients (52%) reported that they had not talked to their primary care physician at all about their options for AAA repair, and one-half (50%) reported that their view of the different surgical options had not been influenced by anyone. Slightly less than one-half of patients reported that they did not receive any information about open surgical aneurysm repair and endovascular aortic aneurysm repair (41% and 37%, respectively). Few patients indicated using the internet as their main source of information about open surgical aneurysm repair and endovascular aortic aneurysm repair (10% and 11%, respectively). CONCLUSIONS: Patients are commonly referred for AAA repair having little to no information regarding AAA pathology or repair options. Fewer than one in five patients searched the internet or had accessed other sources of information on their own. Most vascular surgeons should assume that patients will present to their first vascular surgery appointment with minimal understanding of the treatment options available to them.

Metagenomic insights into bioaugmentation and biovalorization of oily industrial wastes by lipolytic oleaginous yeast Yarrowia lipolytica during successive batch fermentation.

The lipolytic oleaginous yeast Yarrowia lipolytica was used in the bioaugmentation and biovalorization of oily industrial wastes during successive-batch fermentation. Five cycles of nonsterile successive batch fermentation with 70% medium replacement achieved the highest oil removal of 68.1 ± 5.60% and produced biomass and lipid yields of 0.213 ± 0.07 g/g-COD and 146.2 ± 46.5 mg/g-COD, respectively. The cell-bound lipase activity observed in the system was 170.74 ± 32 U/L. The auto-flocculation efficiency of the biomass was >90% within 60 Min. The microbial community changes between Y. lipolytica and indigenous microorganisms were monitored by metagenomic next-generation sequencing of internal transcribed spacer rDNA regions for yeasts and 16S rRNA gene for bacteria. Ylipolytica lipolytica was retained in the consortium together with other indigenous strains until the fifth cycle. Other minor oleaginous yeasts such as Kodamaea ohmeri and Candida tropicalis as well as polyhydroxyalkanoate-accumulating bacteria were found and are likely to have participated in lipid production. This study has shown the robustness of Y. lipolytica in nonsterile successive batch fermentation and its use could contribute greatly to the practical valorization of industrial wastes for lipids and lipases.

Outcome Comparison between Open and Endovascular Management of TASC II D Aortoiliac Occlusive Disease.

BACKGROUND: Endovascular management of complex aortoiliac occlusive disease (AIOD) has been described as a viable alternative to open surgical reconstruction. To date, few studies have directly compared the 2 techniques. We therefore, evaluated short and mid- term outcomes of open and endovascular therapy in TASC II D AIOD patients. METHODS: TASC II D patients undergoing treatment between January 2009 and December 2016 were retrospectively reviewed. Patient demographics, clinical data, and outcomes (complications [technical and systemic] and graft patency) were collected. The primary outcome of this study was primary graft patency. Patients were compared according to treatment group (open versus endovascular). Kaplan-Meier curves were used to analyze follow up results. RESULTS: A total of 75 consecutive patients (open: 30; endovascular: 45) were included in this analysis. In the endovascular group, 25 (55.6%) patients were managed using a hybrid approach with 100% technical success. Critical limb ischemia was the indication for intervention in 16.0% of this cohort (open, 13.3% vs. endovascular, 17.8%, P = 0.397). Overall, there were no significant differences in gender (male: open, 50.0% vs. endovascular, 55.6%, P = 0.637) or age (54.5 ± 5.9 years vs. 57.0 ± 8.7 years, P = 0.171). No in hospital deaths occurred in this cohort. The overall complication rate was significantly higher in the open group (43.3% vs. 17.8%, OR 3.5, 95% CI [1.2-10.1], P = 0.016) with peri-operative systemic complications being more likely in the open cohort (40.0% vs. 6.7%, OR 9.3, 95% CI [2.3-37.3], P < 0.001) while technical complications did not differ between the 2 groups (6.7% vs. 11.1%, OR 0.6, 95% CI [0.1-3.1], P = 0.517). Follow up data was available for 68 patients (90.7%), for a mean of 21.3 ± 17.1 months (range: 1-72 months). Re-intervention rates were significantly higher in the endovascular group (3.3% vs. 20.0%, OR 7.2, 95% CI [1.1-14.3], P = 0.038). The overall primary patency at 2 years was significantly higher in the open group (96.7% vs. 80.0%, OR 7.2, 95% CI [1.2-60.5], P = 0.038). Cox regression analysis revealed separation of the primary outcome for open therapy relative to endovascular repair (log rank, P = 0.320). CONCLUSIONS: In this comparison of open and endovascular therapy for complex AIOD, endovascular therapy was associated with high initial technical success and fewer in-hospital systemic complications but also high re-intervention rates when compared to open repair. Further prospective studies aimed at reduction of complications, optimization of patency, and patient selection for such procedures is warranted.

Spatial Distribution and Diverse Metabolic Functions of Lignocellulose-Degrading Uncultured Bacteria as Revealed by Genome-Centric Metagenomics.

The mechanisms by which specific anaerobic microorganisms remain firmly attached to lignocellulosic material, allowing them to efficiently decompose organic matter, have yet to be elucidated. To circumvent this issue, microbiomes collected from anaerobic digesters treating pig manure and meadow grass were fractionated to separate the planktonic microbes from those adhered to lignocellulosic substrate. Assembly of shotgun reads, followed by a binning process, recovered 151 population genomes, 80 out of which were completely new and were not previously deposited in any database. Genome coverage allowed the identification of microbial spatial distribution in the engineered ecosystem. Moreover, a composite bioinformatic analysis using multiple databases for functional annotation revealed that uncultured members of the Bacteroidetes and Firmicutes follow diverse metabolic strategies for polysaccharide degradation. The structure of cellulosome in Firmicutes species can differ depending on the number and functional roles of carbohydrate-binding modules. In contrast, members of the Bacteroidetes are able to adhere to and degrade lignocellulose due to the presence of multiple carbohydrate-binding family 6 modules in beta-xylosidase and endoglucanase proteins or S-layer homology modules in unknown proteins. This study combines the concept of variability in spatial distribution with genome-centric metagenomics, allowing a functional and taxonomical exploration of the biogas microbiome.IMPORTANCE This work contributes new knowledge about lignocellulose degradation in engineered ecosystems. Specifically, the combination of the spatial distribution of uncultured microbes with genome-centric metagenomics provides novel insights into the metabolic properties of planktonic and firmly attached to plant biomass bacteria. Moreover, the knowledge obtained in this study enabled us to understand the diverse metabolic strategies for polysaccharide degradation in different species of Bacteroidetes and Clostridiales Even though structural elements of cellulosome were restricted to Clostridiales species, our study identified a putative mechanism in Bacteroidetes species for biomass decomposition, which is based on a gene cluster responsible for cellulose degradation, disaccharide cleavage to glucose, and transport to cytoplasm.

Variation in postacute care utilization after complex surgery.

BACKGROUND: Variation in use of postacute care (PAC), including skilled nursing facilities and inpatient rehabilitation, accounts for 73% of regional variation in Medicare spending. Studies of hospital variation in PAC use have typically focused on nonsurgical patients or have been limited to Medicare data. Consequently, there is no nationally representative data on how rates of postoperative discharge to PAC differ between hospitals. The purpose of this study was to explore hospital-level variation in PAC utilization after cardiovascular and abdominal surgery. MATERIALS AND METHODS: We evaluated 3,487,365 patients from the Nationwide Inpatient Sample and 60,666 from the Veterans Affairs health system, who had colorectal surgery, hepatectomy, pancreatectomy, coronary bypass, aortic aneurysm repair, and peripheral vascular bypass from 2008 to 2011. For each hospital, we calculated unadjusted and risk-adjusted observed-to-expected ratios for discharge to PAC facilities (skilled nursing or inpatient rehabilitation). RESULTS: A total of 631,199 (18%) non-veterans and 4744 (8%) veterans were discharged to PAC facilities. For veterans, 32% were ≥70 y old, and 98% were men. For non-veterans, 39% were ≥70, and 60% were men. Hospital rates of discharge to PAC facilities varied from 1% to 36% for veterans hospitals and from 1% to 59% for non-veteran hospitals. Risk-adjusted observed-to-expected ratios ranged from 0.10 to 4.15 for veterans and from 0.11 to 4.3 for non-veteran hospitals. CONCLUSIONS: There is substantial variation in PAC utilization and rates of home discharge after abdominal and cardiovascular surgery. To reduce variation, further research is needed to understand health systems factors that influence PAC utilization.

Variation and Impact of Multiple Complications on Failure to Rescue After Inpatient Surgery.

OBJECTIVE: To examine the extent to which multiple, sequential complications impacts variation in institutional postoperative mortality rates. BACKGROUND: Failure to rescue (FTR) has been proposed as an underlying factor in hospital variation in surgical mortality. However, little is currently known about hospital variation in FTR after multiple complications or the contribution of sequential complications to variation. METHODS: Retrospective cohort study of 266,101 patients within the Veterans Affairs Surgical Quality Improvement Program (2000-2014) who underwent a subset of high-mortality inpatient general, vascular, or thoracic procedures. The association between number of postoperative complications (0, 1, 2, or ≥3) and 30-day mortality across quintiles of hospital risk-adjusted mortality was evaluated with multivariable, multilevel mixed-effects models. RESULTS: Among patients who had a complication, over half (60.9%) had 1, but those with more than 1 accounted for the majority of the deaths (63.1%). Across hospital quintiles, there were no differences in complications (23.5% very low mortality vs 23.6% very high mortality; trend test P = 0.15). FTR increased significantly (12.0% vs 18.1%; trend test P < 0.001) with an incremental impact as complications accrued (6.7% 1 complication vs 26.1% ≥3, lowest quintile; 11.7% 1 complication vs 33.0% ≥3, highest quintile). However, the risk of FTR associated with increasing complications remained relatively constant across hospital quintiles and was not explained by differences in patients presenting with multiple complications on the index complicated day. CONCLUSIONS: FTR occurs predominantly among patients who have more than 1 complication with a dose-response relationship as complications accrue. As this dose-response relationship is observed across hospitals, surgical quality improvement efforts may benefit by shifting focus to broader interventions designed to prevent subsequent complications at all hospitals.

Microbial community changes in methanogenic granules during the transition from mesophilic to thermophilic conditions.

Upflow anaerobic sludge blanket (UASB) reactor is one of the most applied technologies for various high-strength wastewater treatments. The present study analysed the microbial community changes in UASB granules during the transition from mesophilic to thermophilic conditions. Dynamicity of microbial community in granules was analysed using high-throughput sequencing of 16S ribosomal RNA gene amplicons, and the results showed that the temperature strictly determines the diversity of the microbial consortium. It was demonstrated that most of the microbes which were present in the initial mesophilic community were not found in the granules after the transition to thermophilic conditions. More specifically, only members from family Anaerolinaceae managed to tolerate the temperature change and contributed in maintaining the physical integrity of granular structure. On the contrary, new hydrolytic and fermentative bacteria were quickly replacing the old members in the community. A direct result from this abrupt change in the microbial diversity was the accumulation of volatile fatty acids and the concomitant pH drop in the reactor inhibiting the overall anaerobic digestion process. Nevertheless, by maintaining deliberately the pH levels at values higher than 6.5, a methanogen belonging to Methanoculleus genus emerged in the community enhancing the methane production.

Characterization of the planktonic microbiome in upflow anaerobic sludge blanket reactors during adaptation of mesophilic methanogenic granules to thermophilic operational conditions.

Upflow anaerobic sludge blanket (UASB) technology refers to reactor technology where granules, i.e. self-immobilised microbial associations, are the biological catalysts involved in the anaerobic digestion process. During the start-up period, UASB reactors operate at relatively long HRT and therefore the liquid phase of the reactor becomes a favourable environment for microbial growth. The current study aimed to elucidate the dynamicity of the suspended microbial community in UASB reactors, during the transition from mesophilic to thermophilic conditions. High throughput 16S rRNA amplicon sequencing was used to characterize the taxonomic composition of the microbiome. The results showed that the microbial community was mainly composed by hydrolytic and fermentative bacteria. Results revealed relevant shifts in the microbial community composition, which is mainly determined by the operational conditions and the reactor performance. Finally, shared OTUs between the microbial consortia of the suspended and the granular sludge showed that planktonic microbiota is significantly influencing the granule microbial community composition.

A novel archaeal species belonging to Methanoculleus genus identified via de-novo assembly and metagenomic binning process in biogas reactors.

Recently, a first comprehensive catalogue of microbial genomes populating biogas reactors treating manure and agro-industrial residues was determined by sequencing samples collected from 22 biogas reactors including laboratory and full scale. Among the archaeal community, one of the most abundant methanogens belongs to Methanoculleus genus and for this reason it was provisionally named Methanoculleus sp. DTU006. Its full length 16S rRNA sequence is 97% similar to Methanoculleus marisnigri JR1 and to Methanoculleus palmolei DSM 4273. Despite the high similarity of the 16S gene sequence, Average Nucleotide Identity calculation (ANI) calculated on all protein encoding genes indicated that the two most similar species, Methanoculleus bourgensis MS2T and Methanoculleus sp. MAB1, are divergent enough to define Methanoculleus sp. DTU006 as new archaeal species. Its genome (2.15 Mbp) has an estimated completeness around 93%. Analysis of the metabolic pathways using KEGG confirmed that it is a hydrogenotrophic methanogen and therefore it is proposed the Candidatus status by naming it as "Candidatus Methanoculleus thermohydrogenotrophicum".

Percutaneous intervention for carotid in-stent restenosis does not improve outcomes compared with nonoperative management.

BACKGROUND: The appropriateness of percutaneous intervention for moderate to severe carotid in-stent restenosis (C-ISR) is unclear. We therefore sought to compare stroke/death/myocardial infarction (MI) rates between percutaneous interventions and nonoperative management for ≥50% C-ISR. METHODS: We performed a single-center retrospective review of consecutive patients presenting with ≥50% C-ISR to the vascular surgery service. Demographics, comorbidities, and intraoperative and postoperative variables were obtained. The degree of stenosis was verified by review of digital subtraction or computed tomography angiograms. The primary outcome was stroke/death/MI after the diagnosis of ≥50% C-ISR. χ2, Kruskal-Wallis, and Kaplan-Meier analysis was used to quantify outcomes of the patients treated percutaneously vs nonoperatively. RESULTS: During a 13-year period, 59 patients (75 C-ISRs) presented with ≥50% C-ISRs (n = 58 male [98%]; n = 57 C-ISRs asymptomatic [76%]) with a median age of 67.5 years (62.8-74.6). The initial pathologic process underlying the original stent was atherosclerosis in 33 (70%), radiation induced in 10 (21%), prior carotid endarterectomy in 4 (9%), and unknown in 28 (37%). Forty C-ISRs underwent a percutaneous intervention (19 percutaneous angioplasty only [48%]; 21 repeated stent and percutaneous angioplasty [52%]). Median follow-up for the entire cohort was 948 days (283-2322) and similar between the intervention and nonintervention arms. There were no significant differences between the arms with respect to age (P = .16), medical comorbidities (P > .05), original stent type (P = .46), or clopidogrel use (P = .74). At 30 days, there was one stroke and subsequent death in the intervention arm and none in the nonintervention arm. During the follow-up period, a median of 1.0 procedure was required to maintain patency. By Kaplan-Meier analysis, there were no statistically significant differences between the intervention and nonintervention arms with respect to stroke/death/MI as a composite or any of the individual components at last follow-up (P = .82). Kaplan-Meier estimated patency was not significantly superior in the intervention vs the nonintervention arm (8.0 years ± 1.1 vs 5.3 years ± 0.7; P = .14). CONCLUSIONS: Over 13 years, percutaneous interventions for ≥50% C-ISR were safe and durable. However, interventions fail to improve long-term stroke/death/MI or patency rates relative to nonintervention. Intervention for C-ISR may not be necessary, although future appropriately powered, prospective trials will be necessary to confirm these findings and to determine the appropriateness of interventions for C-ISR.

Untangling the Effect of Fatty Acid Addition at Species Level Revealed Different Transcriptional Responses of the Biogas Microbial Community Members.

In the present study, RNA-sequencing was used to elucidate the change of anaerobic digestion metatranscriptome after long chain fatty acids (oleate) exposure. To explore the general transcriptional behavior of the microbiome, the analysis was first performed on shotgun reads without considering a reference metagenome. As a second step, RNA reads were aligned on the genes encoded by the microbial community, revealing the expression of more than 51 000 different transcripts. The present study is the first research which was able to dissect the transcriptional behavior at a single species level by considering the 106 microbial genomes previously identified. The exploration of the metabolic pathways confirmed the importance of Syntrophomonas species in fatty acids degradation, and also highlighted the presence of protective mechanisms toward the long chain fatty acid effects in bacteria belonging to Clostridiales, Rykenellaceae, and in species of the genera Halothermothrix and Anaerobaculum. Additionally, an interesting transcriptional activation of the chemotaxis genes was evidenced in seven species belonging to Clostridia, Halothermothrix, and Tepidanaerobacter. Surprisingly, methanogens revealed a very versatile behavior different from each other, even among similar species of the Methanoculleus genus, while a strong increase of the expression level in Methanosarcina sp. was evidenced after oleate addition.

Progression to stage 3 and 4 chronic kidney disease and risk factor stratification following endovascular aortic aneurysm repair.

BACKGROUND: Risk of progression to various stages of chronic kidney disease (CKD) after endovascular aortic aneurysm repair (EVAR) is unknown. This study estimates progression rates to stage 3 and 4 CKD after EVAR and identifies potential predictors for progression. METHODS: EVAR cases (2006-2012) were retrospectively reviewed. Freedom of progression to CKD was estimated using Kaplan-Meier analysis, and predictors for progression were identified using Cox proportional hazards model. RESULTS: Two hundred and twelve consecutive patients at a single academic institution underwent EVAR for infrarenal aneurysms. Estimated freedom from progression to stage 3 CKD was 80%, 76%, and 63% at 6, 12, and 18 months, respectively, and for stage 4, 97%, 96%, and 93% at 6, 12, and 18 months, respectively. Stage 3 CKD predictors of progression included age (odds ratio (OR): 1.106, p = 0.001), diabetes (OR: 3.052, p = 0.04), perioperative use of angiotensin converting enzyme inhibitors or angiotensin receptor blockers (OR: 3.249, p = 0.02), and operative blood loss (OR: 1.002, p < 0.01). Stage 4 predictors included preoperative hemoglobin (OR: 0.473, p = 0.04) and baseline renal function (OR: 0.928, p = 0.001). Intraoperative contrast administration did not impact CKD development. CONCLUSIONS: Progression to stage 3 CKD after EVAR occurs more frequently and at a higher rate compared with progression to stage 4. Different risk factors are associated with progression to each of those stages of CKD.

Long-term comparison of endovascular and open repair of abdominal aortic aneurysm.

BACKGROUND: Whether elective endovascular repair of abdominal aortic aneurysm reduces long-term morbidity and mortality, as compared with traditional open repair, remains uncertain. METHODS: We randomly assigned 881 patients with asymptomatic abdominal aortic aneurysms who were candidates for both procedures to either endovascular repair (444) or open repair (437) and followed them for up to 9 years (mean, 5.2). Patients were selected from 42 Veterans Affairs medical centers and were 49 years of age or older at the time of registration. RESULTS: More than 95% of the patients underwent the assigned repair. For the primary outcome of all-cause mortality, 146 deaths occurred in each group (hazard ratio with endovascular repair versus open repair, 0.97; 95% confidence interval [CI], 0.77 to 1.22; P=0.81). The previously reported reduction in perioperative mortality with endovascular repair was sustained at 2 years (hazard ratio, 0.63; 95% CI, 0.40 to 0.98; P=0.04) and at 3 years (hazard ratio, 0.72; 95% CI, 0.51 to 1.00; P=0.05) but not thereafter. There were 10 aneurysm-related deaths in the endovascular-repair group (2.3%) versus 16 in the open-repair group (3.7%) (P=0.22). Six aneurysm ruptures were confirmed in the endovascular-repair group versus none in the open-repair group (P=0.03). A significant interaction was observed between age and type of treatment (P=0.006); survival was increased among patients under 70 years of age in the endovascular-repair group but tended to be better among those 70 years of age or older in the open-repair group. CONCLUSIONS: Endovascular repair and open repair resulted in similar long-term survival. The perioperative survival advantage with endovascular repair was sustained for several years, but rupture after repair remained a concern. Endovascular repair led to increased long-term survival among younger patients but not among older patients, for whom a greater benefit from the endovascular approach had been expected. (Funded by the Department of Veterans Affairs Office of Research and Development; OVER ClinicalTrials.gov number, NCT00094575.).

Common carotid artery peak systolic velocity ratio predicts high-grade common carotid stenosis.

OBJECTIVE: Screening for common carotid artery (CCA) stenosis with duplex ultrasound (DUS) velocity criteria alone can be limited by within-patient and between-patients hemodynamic variability. This study aimed to evaluate inter-CCA velocity ratio criteria to predict high-grade CCA stenosis. METHODS: This was a retrospective review of consecutive patients who underwent computed tomography angiography and DUS peak systolic velocity (PSV) measurements of bilateral CCAs, independently recorded, between 2008 and 2014. Patients with dampened CCA waveforms on DUS composed group B. The remainder without dampened waveforms constituted group A. Inter-CCA PSV ratios were calculated by dividing the higher CCA PSV by the lower one of the other side, so the ratios would always be ≥1. Ratios were subsequently paired with each respective unilateral CCA diameter stenosis and differential bilateral CCA diameter stenosis. A quadratic regression model was fitted to predict unilateral and differential stenosis. Receiver operating characteristic curve was used to determine optimal ratios for ≥50% and ≥80% CCA stenosis. The study excluded patients with carotid artery occlusion. RESULTS: From a total of 201 patients, 193 patients were included in group A and 8 in group B. Within group A, 31 patients had ≥50% unilateral stenosis and 17 had ≥50% differential stenosis. All stenoses ≥50% were identified on the same side with the higher PSV. Inter-CCA PSV ratio predicted ≥50% unilateral (r(2) = 0.536; P < .001) and differential stenosis (r(2) = 0.581; P < .001). In group B, all patients had ≥60% stenosis that was near or involved the vessel origin. An increasing inter-CCA PSV ratio showed a trend toward contralateral high-grade stenosis (r(2) = 0.596; P = .1). Receiver operating characteristic curves showed an optimal threshold CCA ratio ≥2.16 for ≥50% unilateral stenosis with 92% accuracy, 62% sensitivity, and 98% specificity (area under curve = 0.854; 95% confidence interval, 0.759-0.948) and a ratio ≥2.62 for ≥50% differential stenosis with 97% accuracy, 83% sensitivity, and 98% specificity (area under curve = 0.94; 95% confidence interval, 0.835-1). CONCLUSIONS: DUS-based CCA PSV ratio can accurately predict unilateral and differential high-grade CCA stenosis. Also, in patients with unilateral dampened waveforms, it implied contralateral severe proximal stenosis. This parameter should be further validated in prospective studies and may serve as an adjunct screening tool to detect high-grade CCA stenosis.

Biogas Upgrading via Hydrogenotrophic Methanogenesis in Two-Stage Continuous Stirred Tank Reactors at Mesophilic and Thermophilic Conditions.

This study proposes an innovative setup composed by two stage reactors to achieve biogas upgrading coupling the CO2 in the biogas with external H2 and subsequent conversion into CH4 by hydrogenotrophic methanogenesis. In this configuration, the biogas produced in the first reactor was transferred to the second one, where H2 was injected. This configuration was tested at both mesophilic and thermophilic conditions. After H2 addition, the produced biogas was upgraded to average CH4 content of 89% in the mesophilic reactor and 85% in the thermophilic. At thermophilic conditions, a higher efficiency of CH4 production and CO2 conversion was recorded. The consequent increase of pH did not inhibit the process indicating adaptation of microorganisms to higher pH levels. The effects of H2 on the microbial community were studied using high-throughput Illumina random sequences and full-length 16S rRNA genes extracted from the total sequences. The relative abundance of archaeal community markedly increased upon H2 addition with Methanoculleus as dominant genus. The increase of hydrogenotrophic methanogens and syntrophic Desulfovibrio and the decrease of aceticlastic methanogens indicate a H2-mediated shift toward the hydrogenotrophic pathway enhancing biogas upgrading. Moreover, Thermoanaerobacteraceae were likely involved in syntrophic acetate oxidation with hydrogenotrophic methanogens in absence of aceticlastic methanogenesis.

The use of cryopreserved aortoiliac allograft for aortic reconstruction in the United States.

BACKGROUND: Aortic infections, even with treatment, have a high mortality and risk of recurrent infection and limb loss. Cryopreserved aortoiliac allograft (CAA) has been proposed for aortic reconstruction to improve outcomes in this high-risk population. METHODS: A multicenter study using a standardized database was performed at 14 of the 20 highest volume institutions that used CAA for aortic reconstruction in the setting of infection or those at high risk for prosthetic graft infection. RESULTS: Two hundred twenty patients (mean age, 65; male:female, 1.6/1) were treated since 2002 for culture positive aortic graft infection (60%), culture negative aortic graft infection (16%), enteric fistula/erosion (15%), infected pseudoaneurysm adjacent to the aortic graft (4%), and other (4%). Intraop cultures indicated infection in 66%. Distal anastomosis was to the femoral artery and iliac. Mean hospital length of stay was 24 days, and 30-day mortality was 9%. Complications occurred in 24% and included persistent sepsis (n = 17), CAA thrombosis (n = 9), CAA rupture (n = 8), recurrent CAA/aortic infection (n = 8), CAA pseudoaneurysm (n = 6), recurrence of aortoenteric fistula (n = 4), and compartment syndrome (n = 1). Patients with full graft excision had significantly better outcomes. Ten (5%) patients required allograft explant. Mean follow-up was 30 ± 3 months. Freedom from graft-related complications, graft explant, and limb loss was 80%, 88%, and 97%, respectively, at 5 years. Primary graft patency was 97% at 5 years, and patient survival was 75% at 1 year and 51% at 5 years. CONCLUSIONS: This largest study of CAA indicates that CAA allows aortic reconstruction in the setting of infection or those at high risk for infection with lower early and long-term morbidity and mortality than other previously reported treatment options. Repair with CAA is associated with low rates of aneurysm formation, recurrent infection, aortic blowout, and limb loss. We believe that CAA should be considered a first line treatment of aortic infections.