Active degradation-nitrification microbial assemblages in the hypoxic zone in a subtropical estuary.

In 2017 summer, we observed widespread bottom hypoxia at the lower estuary of the Pearl River estuary (PRE). Our previous study noticed that AOA and bacteria were highly abundant and clustered within the hypoxia zone. Moreover, nitrification and respiration rates were also evidently higher in these hypoxic waters. These observations prompt us to investigate whether these two oxygen-consuming microorganisms have symbiotic relationships and whether specific groups consistently coexist and form ecological-meaningful associations. In this study, we use network analysis to investigate the presence and active communities (DNA-RNA) based on bacterial and AOA communities sequencing (inferred from the 16S rRNA and amoA gene, respectively) to gain more insight into ecological-meaningful associations. We observed a highly diverse and active bacterial community in the hypoxia zone. The RNA networks were more modulized than the corresponding DNA networks, indicating that the active communities were better parsed into functional microbial assemblages. The network topology revealed that Gammaproteobacteria, Bacteroidetes (Flavobacteriales), Alphaproteobacteria (Rhodobacterales and Rhodospirillales), Marinimicrobia, Cyanobacteria (Synechococcales), and AOA sublineages were module hubs and connectors, indicating that they were the keystone taxa of the microbial communities. The hub-subnetwork further showed robust co-occurrence between Gammaproteobacteria, Bacteroidetes (Flavobacteriales), Alphaproteobacteria (Rhodobacterales and Rhodospirillales), Marinimicrobia with AOA sublineages, and Nitrospinae (presumably NOB) reflecting the formation of Degradation-Nitrification (sequential oxidation of Organic matter degradation to ammonia, then nitrate) microbial assemblage in the hypoxia zone. The subnetworks revealed AOA ecotype-specific modularization and niche partitioning of different AOA sublineages. Interestingly, the recurring co-occurrence of nitrifiers assemblage in the RNA subnetworks (SCM1-like-II (AOA) and Nitrospinae OTUs (NOB) suggests an active interaction via nitrite exchange. The Degradation-Nitrification microbial assemblage may contribute substantially to the oxygen consumption in the hypoxia formation in PRE. Our results provide new insight into the functional microbial assemblages, which is worth further investigation on their ecological implication in estuarine waters.

Discovery of Euryhaline Phycoerythrobilin-Containing Synechococcus and Its Mechanisms for Adaptation to Estuarine Environments.

Synechococcus are among the most abundant and widely distributed picocyanobacteria on earth. Cluster 5 phycoerythrobilin-containing (PEB-containing) Synechococcus, the major marine Synechococcus, were considered to prefer high salinity, and they are absent in estuarine ecosystems. However, we have detected PEB-containing Synechococcus in some low-salinity (<15-ppt) areas of the Pearl River estuary at an abundance up to 1.0 × 105 cells ml-1 Two PEB-containing Synechococcus strains (HK01 and LTW-R) were isolated, and tests on them revealed their ability to cope with variations in the salinity (from 14 to 44 ppt). Phylogenetic analysis showed that HK01 belonged to a novel Synechococcus clade (HK1), whereas LTW-R was clustered with S5.2 strains. Whole-genome analysis revealed that a membrane channel protein with glycine zipper motifs is unique to euryhaline Synechococcus The upregulation of this protein, the osmotic sensors, and the heat shock protein HSP20 and the downregulation of the osmolyte biosynthesis enable euryhaline Synechococcus to well adapt to the low and fluctuating salinity in the estuarine environment. In addition, decreasing the salinity in LTW-R strongly downregulated several important metabolic pathways, including photosynthesis, and the Calvin-Benson cycle, whereas its growth was not significantly affected. Moreover, obtaining PEB genes from horizontal gene transfer expands the light niche significantly for euryhaline Synechococcus These results provided new insights into the life strategies and ecological function of marine PEB-containing Synechococcus under the unique environmental condition of estuarine waters, particularly in response to salinity variations.IMPORTANCE Understanding the strategies developed by different microbial groups to adapt to specific niches is critical. Through genome and transcriptome analyses of two newly isolated novel euryhaline Synechococcus strains, this study revealed that cluster 5 phycoerythrobilin-containing Synechococcus, which are thought to be strictly marine strains, could be abundant in low-salinity waters of the Pearl River estuary (salinity <15 ppt) and explained the molecular mechanisms that enabled them to adapt the low and fluctuating salinity in the estuarine environment. This study expands current understanding on mechanisms involved in niche separation of marine Synechococcus lineages.

Comparison of the seasonal variations of Synechococcus assemblage structures in estuarine waters and coastal waters of Hong Kong.

Seasonal variation in the phylogenetic composition of Synechococcus assemblages in estuarine and coastal waters of Hong Kong was examined through pyrosequencing of the rpoC1 gene. Sixteen samples were collected in 2009 from two stations representing estuarine and ocean-influenced coastal waters, respectively. Synechococcus abundance in coastal waters gradually increased from 3.6 × 10(3) cells ml(-1) in March, reaching a peak value of 5.7 × 10(5) cells ml(-1) in July, and then gradually decreased to 9.3 × 10(3) cells ml(-1) in December. The changes in Synechococcus abundance in estuarine waters followed a pattern similar to that in coastal waters, whereas its composition shifted from being dominated by phycoerythrin-rich (PE-type) strains in winter to phycocyanin-only (PC-type) strains in summer owing to the increase in freshwater discharge from the Pearl River and higher water temperature. The high abundance of PC-type Synechococcus was composed of subcluster 5.2 marine Synechococcus, freshwater Synechococcus (F-PC), and Cyanobium. The Synechococcus assemblage in the coastal waters, on the other hand, was dominated by marine PE-type Synechococcus, with subcluster 5.1 clades II and VI as the major lineages from April to September, when the summer monsoon prevailed. Besides these two clades, clade III cooccurred with clade V at relatively high abundance in summer. During winter, the Synechococcus assemblage compositions at the two sites were similar and were dominated by subcluster 5.1 clades II and IX and an undescribed clade (represented by Synechococcus sp. strain miyav). Clade IX Synechococcus was a relatively ubiquitous PE-type Synechococcus found at both sites, and our study demonstrates that some strains of the clade have the ability to deal with large variation of salinity in subtropical estuarine environments. Our study suggests that changes in seawater temperature and salinity caused by the seasonal variation of monsoonal forcing are two major determinants of the community composition and abundance of Synechococcus assemblages in Hong Kong waters.

Aspirin resistance and adverse clinical events in patients with coronary artery disease.

PURPOSE: We sought to determine the clinical significance of aspirin resistance measured by a point-of-care assay in stable patients with coronary artery disease (CAD). METHODS: We used the VerifyNow Aspirin (Accumetrics Inc, San Diego, Calif) to determine aspirin responsiveness of 468 stable CAD patients on aspirin 80 to 325 mg daily for > or =4 weeks. Aspirin resistance was defined as an Aspirin Reaction Unit > or =550. The primary outcome was the composite of cardiovascular death, myocardial infarction (MI), unstable angina requiring hospitalization, stroke, and transient ischemic attack. RESULTS: Aspirin resistance was noted in 128 (27.4%) patients. After a mean follow-up of 379+/-200 days, patients with aspirin resistance were at increased risk of the composite outcome compared to patients who were aspirin-sensitive (15.6% vs 5.3%, hazard ratio [HR] 3.12, 95% confidence intervals [CI], 1.65-5.91, P < .001). Cox proportional hazard regression modeling identified aspirin resistance, diabetes, prior MI, and a low hemoglobin to be independently associated with major adverse long-term outcomes (HR for aspirin resistance 2.46, 95% CI, 1.27-4.76, P = .007). CONCLUSIONS: Aspirin resistance, defined by an aggregation-based rapid platelet function assay, is associated with an increased risk of adverse clinical outcomes in stable patients with CAD.

Incidence and predictors of upper gastrointestinal bleeding in patients receiving low-dose aspirin for secondary prevention of cardiovascular events in patients with coronary artery disease.

AIM: The use of low-dose aspirin to prevent cardiovascular disease events is well established. However, the incidence and predictors of upper gastrointestinal bleeding (UGIB) with its use are unknown. We studied prospectively the incidence and outcome of peptic ulceration in low-dose aspirin users. METHODS: A total of 991 patients with coronary artery disease (CAD) on low-dose aspirin were prospectively followed-up for two years for the occurrence and clinical features of first hospitalized episode of UGIB. RESULTS: UGIB had a bimodal presentation with 45% occurring within four months of aspirin initiation and had an overall prevalence of 1.5% per year. There was no UGIB-related death. Hypertension (OR = 4.6, 95%CI 1.5-14.7, P = 0.009), history of peptic ulceration (OR = 3.1, 95%CI 1.1-9.0, P = 0.039), tertiary education (OR = 3.08, 95%CI 1.1-9.0, P = 0.039) and higher lean body mass (P = 0.016) were independent factors associated with UGIB. Use of nitrate did not reduce UGIB. CONCLUSION: The incidence of UGIB in patients with CAD on long-term low-dose aspirin is low, but is accompanied with significant morbidity. With prolonged use of aspirin, UGIB continues to be a problem for those with risk factors and especially in patients with a history of peptic ulcers, in which UGIB tends to occur early after aspirin therapy.

Prediction of aortic augmentation index using radial pulse transmission-wave analysis.

OBJECTIVE: Current arterial transfer functions have low capability in predicting aortic augmentation index (AIx) from radial pulse contour (RPC), because of the difficulty in accurately identifying the merging point (inflection point) in the derived aortic pulse contour (APC). We hypothesize that the formation time between each characteristic wave in APC is about one-third of ejection duration (ED/3). We sought to assess the accuracy of ED/3 in identifying the merging point in APC as compared to the conventional differential method. In addition, we sought to derive the AIx from RPC based on an arterial transfer function and the ED/3 method. METHODS: APC and RPC sequences were measured digitally and simultaneously in 60 subjects (37 males; aged 60 +/- 10 years). An ensemble-averaged RPC-to-APC transfer function was determined from 30 randomly selected subjects and was used to derive APC sequences in the 30 additional subjects. The accuracy of AIx predicted from RPC was determined. RESULTS: In patients with a clearly identifiable merging point in APC, the ED/3 method identified the merging point of measured APC within 1.97 +/- 0.60 ms of that identified by the conventional differential method, with identical AIx. The AIx and merging point of derived APC using the ED/3 method were also within 0.22 +/- 1.01% and 1.81 +/- 1.64 ms, respectively, of those of the measured APC using the conventional differential method. The accuracy of the predicted AIx was independent of age, sex, body-mass index and presence of hypertension. CONCLUSION: In a quiet resting state, the ED/3 is an alternative method for identifying the merging point in APC. In conjunction with transfer-function technique, AIx can be derived accurately from RPC.

A randomized, double-blind, placebo-controlled trial of abciximab for prevention of in-stent restenosis in diabetic patients after coronary stenting: results of the ASIAD (Abciximab in Stenting Inhibits restenosis Among Diabetics) Trial.

OBJECTIVES: Coronary stenting is associated with a high incidence of restenosis in patients with diabetes mellitus. Recent data suggest that diabetic patients treated with abciximab have a lower rate of target vessel revascularization (TVR). We sought to investigate whether abciximab can reduce in-stent restenosis after coronary stenting in diabetic patients. METHODS: In this prospective double-blind trial, we randomly assigned 254 patients with type 2 diabetes mellitus undergoing nonurgent coronary stenting to receive abciximab with an initial heparin bolus of 50 U/kg (n = 128) or placebo with an initial heparin bolus of 70 U/kg (n = 126). All patients received aspirin and clopidogrel before the procedure. The primary endpoint was angiographic restenosis by quantitative coronary angiography at 6 months. The secondary endpoint was death, myocardial infarction (MI), or target lesion revascularization (TLR) at 6 months. RESULTS: The clinical, angiographic, and procedural characteristics were matched between the 2 groups. Angiographic follow-up was completed in 226 patients (90%). Angiographic restenosis occurred in 29.1% of the abciximab group, and 24% of the placebo group (p = 0.30). The rates of the secondary endpoint were similar between the 2 groups (23.4% in the abciximab group versus 22.2% in the placebo group; p = 0.88). TLR was performed on 36 (18.4%) lesions in 29 (23.4%) patients of the abciximab group, and 26 (13.6%) lesions in 23 (18.3%) patients of the placebo groups, respectively (p = 0.21 and 0.35, respectively). CONCLUSIONS: Abciximab does not reduce angiographic restenosis or TLR in type 2 diabetic patients undergoing nonurgent coronary stenting.

Relation of aspirin resistance to coronary flow reserve in patients undergoing elective percutaneous coronary intervention.

Previous studies have shown that more complete platelet inhibition improves the coronary flow reserve (CFR), a measure of microvascular integrity, in patients undergoing percutaneous coronary intervention (PCI). We hypothesized that patients with aspirin resistance would have impaired CFR after elective PCI. We used VerifyNow Aspirin to determine the response to aspirin in 117 consecutive patients who underwent elective single-lesion PCI. The assay results are expressed quantitatively in Aspirin Reaction Units based on the degree of platelet aggregation. All patients received a 300-mg loading dose of clopidogrel >12 hours before and a 75-mg maintenance dose the morning of PCI. CFR was estimated using the Thrombolysis In Myocardial Infarction frame count method. Of the 117 patients, 22 (18.8%) were aspirin resistant. The clinical, angiographic, and procedural characteristics of the aspirin-sensitive and -resistant patients were balanced. All patients underwent successful PCI with <50% residual diameter stenosis and Thrombolysis In Myocardial Infarction grade 3 flow after PCI. Aspirin-resistant patients had a lower CFR than the aspirin-sensitive patients (1.42 +/- 0.35 vs 1.80 +/- 0.64, p = 0.018). Univariate correlates of CFR included the Aspirin Reaction Unit (r = -0.227, p = 0.014) and post-PCI creatine kinase-MB elevation (p = 0.048). Multivariate linear regression analysis revealed the Aspirin Reaction Unit to be the only independent determinant of CFR after PCI (r2 = 0.051, p = 0.014). Thus, aspirin resistance was associated with impaired CFR in patients who underwent elective PCI, implicating insufficient aspirin-induced platelet inhibition as a cause of microvascular dysfunction by distal atherothrombotic embolization and/or spasm.

Low-dose aspirin increases aspirin resistance in patients with coronary artery disease.

PURPOSE: We sought to investigate the association of aspirin dose and aspirin resistance in stable coronary artery disease patients measured by a point-of-care assay. METHODS: We studied 468 consecutive stable coronary artery disease patients in a referral cardiac center who were taking aspirin 80 to 325 mg daily for > or =4 weeks. The VerifyNow Aspirin (Ultegra RPFA-ASA, Accumetrics Inc, San Diego, Calif) was used to determine aspirin responsiveness. An aspirin reaction unit (ARU) > or =550 indicates the absence of aspirin-induced platelet dysfunction, based on correlation with epinephrine-induced light transmission aggregometry. Demographic and clinical data were collected to analyze the predictors of aspirin resistance. RESULTS: Aspirin resistance was noted in 128 (27.4%) patients. Univariate predictors of aspirin resistance include elderly (P = 0.002), women (P <0.001), anemia (P <0.001), renal insufficiency (P = 0.009) and aspirin dose < or =100 mg (P = 0.004). Multivariate analysis revealed hemoglobin (odds ratio [OR] 0.6; 95% confidence interval [CI] 0.51 to 0.69; P <0.001) and aspirin dose < or =100 mg (OR 2.23; 95% CI 1.12 to 4.44; P = 0.022) to be independent predictors of aspirin resistance. Daily aspirin dose < or = 100 mg was associated with increased prevalence of aspirin resistance compared with 150 mg and 300 mg daily (30.2% vs 16.7% vs 0%, P = 0.0062). CONCLUSION: A 100 mg or less daily dose of aspirin, which may have lower side effects, is associated with a higher incidence of aspirin resistance in patients with coronary artery disease. Prospective randomized studies are warranted to elucidate the optimal aspirin dosage for preventing ischemic complications of atherothrombotic disease.

Concomitant coronary and subclavian steal caused by ipsilateral subclavian artery stenosis and arteriovenous fistula in a hemodialysis patient.

Patients with chronic renal failure, because of concomitant conventional cardiovascular and uremia-associated risk factors, are at risk of developing diffuse and accelerated atherosclerosis involving both the coronary and peripheral territories. We report an end-stage renal failure patient with a history of coronary artery bypass surgery who developed both angina and dizziness during hemodialysis via a left forearm arteriovenous fistula. Magnetic resonance imaging diagnosed the presence of significant subclavian artery stenosis. The patient then underwent successful percutaneous stenting of the left subclavian artery. His angina and dizziness symptoms resolved subsequently.

Aspirin resistance is associated with a high incidence of myonecrosis after non-urgent percutaneous coronary intervention despite clopidogrel pretreatment.

OBJECTIVES: We sought to investigate the effect of aspirin resistance on the incidence of myonecrosis after non-urgent percutaneous coronary intervention (PCI) among patients pretreated with clopidogrel. BACKGROUND: Oral antiplatelet therapy using aspirin and a thienopyridine is the standard of care for preventing thrombotic complications of PCI. The effect of aspirin resistance on the outcomes of patients undergoing PCI is unknown. METHODS: We used the Ultegra Rapid Platelet Function Assay-ASA (Accumetrics Inc., San Diego, California) to determine aspirin responsiveness of 151 patients scheduled for non-urgent PCI. All patients received a 300-mg loading dose of clopidogrel >12 h before and a 75-mg maintenance dose in the morning of the PCI. The incidence of myonecrosis was measured by creatine kinase-myocardial band (CK-MB) and by troponin I (TnI) elevations after PCI. RESULTS: A total of 29 (19.2%) patients were noted to be aspirin-resistant. There was a significantly higher incidence of female subjects in the aspirin-resistant versus aspirin-sensitive groups. The incidence of any CK-MB elevation was 51.7% in aspirin-resistant patients and 24.6% in aspirin-sensitive patients (p = 0.006). Elevation of TnI was observed in 65.5% of aspirin-resistant patients and 38.5% of aspirin-sensitive patients (p = 0.012). Multivariate analysis revealed aspirin resistance (odds ratio [OR] 2.9; 95% confidence interval [CI] 1.2 to 6.9; p = 0.015) and bifurcation lesion (OR 2.8; 95% CI 1.3 to 6.0; p = 0.007) to be independent predictors of CK-MB elevation after PCI. CONCLUSIONS: Despite adequate pretreatment with clopidogrel, patients with aspirin resistance as measured by a point-of-care assay have an increased risk of myonecrosis following non-urgent PCI.

Safety and feasibility of the use of a distal filter protection device in percutaneous revascularization of small coronary arteries.

The FilterWire EX is one of the filter protection devices developed as alternatives to balloon occlusion system for percutaneous coronary intervention. Its use has been recommended in vessels between 3.5 and 5.5 mm in diameter and no data are available on its use in smaller vessels. We evaluated the safety and feasibility of using FilterWire EX in native coronary arteries smaller than 3.5 mm. We successfully deployed and retrieved the FilterWire EX in 49 coronary arteries with a mean vessel diameter of 2.62 +/- 0.45 mm at device deployment. Reversible vasospasm was observed in 24 (50%) vessels, coronary flow was temporarily reduced in 22 (44.9%), and distal embolization was noted in 2 (4%). There was no vessel dissection induced by the device. These data suggest that it is safe and feasible to use the FilterWire EX in small coronary arteries.

Percutaneous recanalization of chronic subclavian artery occlusion using optical coherence reflectometry-guided radiofrequency ablation guidewire.

Subclavian artery lesion that is associated with low complication rate could be treated by percutaneous intervention effectively. However, the success of endovascular therapy for occlusive lesion may be limited by failure to cross with a guidewire. We describe the use of a system using optical coherence reflectometry for navigation and radiofrequency ablation to enable wire passage through subclavian artery occlusion that could not be crossed by conventional guidewires.

Initial experience and safety in the treatment of chronic total coronary occlusions with a new optical coherent reflectometry-guided radiofrequency ablation guidewire.

The Safe-Cross wire system, which has optical coherence reflectometry technology for navigating and radiofrequency energy provided at its tip for crossing chronic total occlusions (CTOs), provides a promising means to treat hard, organized CTOs. Using this system, we report on a 60% success rate in patients who had long-standing coronary CTOs that had > or =1 failed attempt using conventional percutaneous coronary intervention.

Recanalization of chronic and long occlusive in-stent restenosis using optical coherence reflectometry-guided radiofrequency ablation guidewire.

Chronic total occlusions remain a challenge to interventionalists due to failure of crossing or perforation by strong wires. We describe the use of a system using optical coherence reflectometry for navigation and radiofrequency ablation to enable wire passage through occlusions that could not be crossed by conventional guidewires.

Stable and optimal anticoagulation is achieved with a single dose of intravenous enoxaparin in patients undergoing percutaneous coronary intervention.

This study assessed the pharmacokinetics, safety and efficacy of intravenous enoxaparin in patients undergoing percutaneous coronary intervention (PCI). Sixty consecutive patients [(age, 62 11 years; female, 16%; diabetes, 18%; hypertension, 53%; prior myocardial infarction (MI), 43%] undergoing PCI (stable angina, 89%; stent, 92%; two-vessel disease, 23%; B2/C lesions, 45%) were administered intravenous enoxaparin 1 mg/kg for procedural anticoagulation. Blood samples for anti-Xa level and activated partial thromboplastin time (aPTT) were assayed from the first 20 patients before and after enoxaparin administration at the following intervals: 5, 30, 60, 90, 120, 150, 180, 210, 240, 360 and 480 minutes. Activated clotting time was assessed 5 minutes after enoxaparin administration. Bleeding complications were classified according to Thrombolysis In Myocardial Infarction (TIMI) criteria. All patients were monitored for adverse clinical events at clinic visit 4 8 weeks after hospital discharge. No TIMI major or minor bleedings occurred during hospitalization for the PCI (median stay post-PCI = 1 day). One patient (2%) developed a non-Q wave MI after the PCI and before hospital discharge. There was no death or urgent revascularization up to clinical follow-up. The peak anti-Xa level was 1.30 0.18 IU/ml (range, 1.03 1.69 IU/ml). The minimum anti-Xa level was 0.55 IU/ml 4 hours after enoxaparin. Thus, the use of intravenous enoxaparin in patients undergoing PCI is associated with a low incidence of ischemic and bleeding complications. A stable therapeutic anticoagulant effect is provided without the need for monitoring within 4 hours of enoxaparin administration.