Clinical Factors and Outcomes When Real-World Heart Teams Overruled STS Risk Scores in TAVR Cases.

Objectives: This study was conducted to determine why heart teams recommended transcatheter aortic valve replacement (TAVR) versus surgical AVR (SAVR) for patients at low predicted risk of mortality (PROM) and describe outcomes of these cases. Background: Historically, referral to TAVR was based predominately on the Society of Thoracic Surgeons (STS) risk model's PROM >3%. In selected cases, heart teams had latitude to overrule these scores. The clinical reasons and outcomes for these cases are unclear. Methods: Retrospective data were gathered for all TAVR and SAVR cases conducted by 9 hospitals between 2013 and 2017. Results: Cases included TAVR patients with STS PROM >3% (n = 2,711) and ≤3% (n = 415) and SAVR with STS PROM ≤3% (n = 1,438). Leading reasons for recommending TAVR in the PROM ≤3% group were frailty (57%), hostile chest (22%), severe lung disease (16%), and morbid obesity (13%), and 44% of cases had multiple reasons. Most postoperative and 30-day outcomes were similar between TAVR groups, but the STS PROM ≤3% group had a one-day shorter length of stay (2.5 ± 3.4 vs. 3.5 ± 4.7 days; p ≤ 0.001) and higher one-year survival (91.6% vs. 86.0%, p=0.002). In patients with STS PROM ≤3%, 30-day mortality was higher for TAVR versus SAVR (2.0% vs. 0.6%; p < 0.001). Conclusions: Heart teams recommended TAVR in patients with STS PROM ≤3% primarily due to frailty, hostile chest, severe lung disease, and/or morbid obesity. Similar postoperative outcomes between these patients and those with STS PROM >3% suggest that decisions to overrule STS PROM ≤3% were merited and may have reduced SAVR 30-day mortality rate.

Intrathoracic complications associated with trans-femoral transcatheter aortic valve replacement: Implications for emergency surgical preparedness.

BACKGROUND: Intrathoracic complications (ITC) requiring emergency surgical intervention occur during transcatheter aortic valve replacement (TAVR). OBJECTIVES: Characterize the incidence, outcomes and predictors of ITC in a large cohort of transfemoral (TF) TAVR cases over a 5 year period. METHODS: Retrospective registry and chart review of all nonclinical trial TF-TAVR patients from seven centers within one hospital system from 2012-2016. ITC were defined as cardiac perforation, new or worsening pericardial effusion/tamponade, annular rupture, thoracic aortic injury, aortic valve dislodgement, and coronary artery occlusion. Procedural and 30-day outcomes and 1-year mortality were compared between ITC and no ITC patients. Multivariable logistic regression was used to identify predictors of ITC. RESULTS: Over the study period, 1,581 patients had TF-TAVR and 68 ITC occurred in 46 patients (2.9%). The most common ITCs were pericardial effusion/tamponade (59%), cardiac perforation (33%), and valve dislodgement (33%). ITC rate did not decline over time (rate (95% confidence interval) for 2012 = 0% (0-8.8%), 2013 = 1.3% (0-7.2%), 2014 = 4.4% (2.2-8.0%), 2015 = 3.5% (2.0-5.6%), and 2016 = 2.4% (1.5-3.8%)). ITC patients had worse 1-year survival (ITC: 60.7% (45.1-73.1%), no ITC: 88.7% (87.0-90.3%); p < .001). The majority of ITC patient deaths occurred within the first 30 days. Multivariable models to predict ITC were not successful. CONCLUSIONS: ITC did not decline over time in our cohort. Predictors of ITC could not be identified. While these events are rare, they are associated with worse procedural outcomes and mortality. Heart teams should continue to be prepared for emergency intervention.

A Phase 2, randomized, partially blinded, active-controlled study assessing the efficacy and safety of variable anticoagulation reversal using the REG1 system in patients with acute coronary syndromes: results of the RADAR trial.

AIMS: We sought to determine the degree of anticoagulation reversal required to mitigate bleeding, and assess the feasibility of using pegnivacogin to prevent ischaemic events in acute coronary syndrome (ACS) patients managed with an early invasive approach. REG1 consists of pegnivacogin, an RNA aptamer selective factor IXa inhibitor, and its complementary controlling agent, anivamersen. REG1 has not been studied in invasively managed patients with ACS nor has an optimal level of reversal allowing safe sheath removal been defined. METHODS AND RESULTS: Non-ST-elevation ACS patients (n = 640) with planned early cardiac catheterization via femoral access were randomized 2:1:1:2:2 to pegnivacogin with 25, 50, 75, or 100% anivamersen reversal or heparin. The primary endpoint was total ACUITY bleeding through 30 days. Secondary endpoints included major bleeding and the composite of death, myocardial infarction, urgent target vessel revascularization, or recurrent ischaemia. Enrolment in the 25% reversal arm was suspended after 41 patients. Enrolment was stopped after three patients experienced allergic-like reactions. Bleeding occurred in 65, 34, 35, 30, and 31% of REG1 patients with 25, 50, 75, and 100% reversal and heparin. Major bleeding occurred in 20, 11, 8, 7, and 10% of patients. Ischaemic events occurred in 3.0 and 5.7% of REG1 and heparin patients, respectively. CONCLUSION: At least 50% reversal is required to allow safe sheath removal after cardiac catheterization. REG1 appears a safe strategy to anticoagulate ACS patients managed invasively and warrants further investigation in adequately powered clinical trials of patients who require short-term high-intensity anticoagulation.

Turning the operating room into a mixed-reality environment: a prospective clinical investigation for cerebral aneurysm clipping.

OBJECTIVE: The overall aim of this study was to demonstrate the potential benefit of a novel mixed-reality-head-mounted display (MR-HMD) on the spatial orientation of surgeons. METHODS: In a prospective clinical investigation, the authors applied for the first time a new multicamera navigation technology in an operating room setting that allowed them to directly compare MR-HMD navigation to standard monitor navigation. In the study, which included 14 patients with nonruptured middle cerebral artery aneurysms, the authors investigated how intuitively and effectively surgical instruments could be guided in 5 different visual navigation conditions. RESULTS: The authors demonstrate that multicamera tracking can be reliably integrated in a clinical setting (usability score 1.12 ± 0.31). Moreover, the technology captures large volumes of the operating room, allowing the team to track and integrate different devices and instruments, including MR-HMDs. Directly comparing mixed-reality navigation to standard monitor navigation revealed a significantly improved intuition in mixed reality, leading to navigation times that were twice as fast (2.1×, p ≤ 0.01). Despite the enhanced speed, the same targeting accuracy (approximately 2.5 mm, freehand tool use) in comparison to monitor navigation could be observed. Intraoperative planning strategies with mixed reality clearly outperformed classic preoperative planning: surgeons scored the mixed-reality plan as the best trajectory in 63% of the cases (chance level 33%). CONCLUSIONS: The incorporation of mixed reality in neurosurgical operations marks a significant advancement in the field. The use of mixed reality in brain surgery enhances the spatial awareness of surgeons, enabling more instinctive and precise surgical interventions. This technological integration promises to refine the execution of complex procedures without compromising accuracy.

Sustained effects for training of smooth pursuit plasticity.

Maintaining orientation in space is a multisensory process, with the vestibular, visual, auditory and somatosensory systems as inputs. Since the input from each individual system changes, for example due to aging, the central nervous system must continuously adapt to these changes to maintain proper system performance. Changes can also be elicited by targeted modifications of the inputs, or by controlled training of sensory systems. While the effects of adaptation on eye movements elicited by the vestibulo-ocular reflex are well established, modifications of the efficacy of smooth pursuit eye movements are less well understood. We have investigated whether two 6-min training sessions on three subsequent days can induce lasting changes in the open- and closed-loop smooth pursuit performance of healthy, adult subjects. Ten subjects practiced making pursuit eye movements by tracking a target cross which moved quasi-randomly on a computer screen. Smooth pursuit performance was tested with a step-ramp paradigm immediately before and after the training, as well as 5 days after the last training session. Our results show that even such short training sessions can induce significant, lasting improvements in closed-loop smooth pursuit performance if the pursuit system of the subjects is challenged sufficiently during training. Control experiments on ten additional adult subjects who had their pursuit performance tested before and after a 20 min break without visual training confirmed that the pursuit enhancement is due to the visual training and not due to perceptual learning.

Government Regulation and Percutaneous Coronary Intervention Volume, Access and Outcomes: Insights From the Washington State Cardiac Care Outcomes Assessment Program.

Background It is unclear how to geographically distribute percutaneous coronary intervention (PCI) programs to optimize patient outcomes. The Washington State Certificate of Need program seeks to balance hospital volume and patient access through regulation of elective PCI. Methods and Results We performed a retrospective cohort study of all non-Veterans Affairs hospitals with PCI programs in Washington State from 2009 to 2018. Hospitals were classified as having (1) full PCI services and surgical backup (legacy hospitals, n=17); (2) full services without surgical backup (new certificate of need [CON] hospitals, n=9); or (3) only nonelective PCI without surgical backup (myocardial infarction [MI] access hospitals, n=9). Annual median hospital-level volumes were highest at legacy hospitals (605, interquartile range, 466-780), followed by new CON, (243, interquartile range, 146-287) and MI access, (61, interquartile range, 23-145). Compared with MI access hospitals, risk-adjusted mortality for nonelective patients was lower for legacy (odds ratio [OR], 0.59 [95% CI, 0.48-0.72]) and new-CON hospitals (OR, 0.55 [95% CI, 0.45-0.65]). Legacy hospitals provided access within 60 minutes for 90% of the population; addition of new CON and MI access hospitals resulted in only an additional 1.5% of the population having access within 60 minutes. Conclusions Many PCI programs in Washington State do not meet minimum volume standards despite regulation designed to consolidate elective PCI procedures. This CON strategy has resulted in a tiered system that includes low-volume centers treating high-risk patients with poor outcomes, without significant increase in geographic access. CON policies should re-evaluate the number and distribution of PCI programs.

Comparison of 26-mm Evolut and 23-mm Sapien 3 Valves in TAVR for Small Aortic Annulus.

BACKGROUND: Patients with small aortic annuli (SAA) are prone to higher post-transcatheter aortic valve replacement (TAVR) transvalvular gradients and development of prosthesis-patient mismatch (PPM). In many patients with SAA, the choice of TAVR valve commonly involves choosing between the 26-mm Medtronic Evolut 2 (ME26) or the 23-mm Edwards Sapien 3 valve (ES23). We compared echocardiographic and clinical outcomes in patients with SAA undergoing TAVR with either valve. METHODS: We queried the Providence St. Joseph Health Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapy Registry database for patients undergoing TAVR with either the ES23 or ME26 between July 2015 and December 2018 at 11 hospitals. Post-TAVR echocardiographic and clinical results in-hospital, at 1 month, and at 1 year were examined. High gradient (HG) was defined as mean gradient (MG) ≥20 mm Hg. RESULTS: We identified 1162 patients with SAA undergoing TAVR with either the ME26 (n = 233) or ES23 valve (n = 929). Baseline characteristics between groups were similar. At 1 month, the ME26 was associated with a lower MG than the ES23 (7.7 ± 4.7 mm Hg vs 13.1 ± 4.9 mm Hg; P<.001) and moderate or severe PPM (11% and 3% vs 27% and 13%; P<.001). Occurrence of HG at 1 year was lower with the ME26 valve vs the ES23 valve (0% vs 15%; P<.001). In-hospital and follow-up clinical outcomes to 1 year were similar for both groups. CONCLUSION: TAVR in SAA with the ME26 is associated with lower incidence of HG or PPM compared with the ES23. While clinical outcomes at 1 year were similar, the long-term implications of these findings remain unknown.

Intraosseous transcutaneous amputation prosthesis (ITAP) for limb salvage in 4 dogs.

OBJECTIVE: To report clinical application of intraosseous transcutaneous amputation prosthesis (ITAP) for limb salvage. STUDY DESIGN: Retrospective case series. SAMPLE POPULATION: Client owned dogs with malignant neoplasia of the distal aspect of the limb. METHOD: Distal limb amputation allowed press-fit insertion of the ITAP into the radius (n = 3) or tibia (1). Remaining soft tissues including skin were attached directly to the ITAP. Limb stump and ITAP were protected by bandaging (1) or external skeletal fixation (3) for 5-6 weeks before exoprosthesis attachment. Measures of outcome included subjective assessments of limb function by owners and veterinarians, radiographic (4) and histologic (1) examination. RESULTS: Dermal integration with the ITAP was achieved by 3 weeks and dogs were walking in a pain-free manner by 8 weeks. One dog was administered adjunctive carboplatin chemotherapy. No evidence of local tumor recurrence occurred. In 1 dog, ITAP fracture occurred at 10 weeks and was successfully managed by ITAP replacement. Three dogs were euthanatized because of confirmed or assumed metastatic disease at 8, 12, and 17 months. Histologic examination of the ITAP-limb interface at 1 year documented osseous and dermal integration. CONCLUSION: Implantation of ITAP to the distal limb of dogs is feasible and can result in favorable functional outcomes. Biological integration of osseous and dermal tissues with ITAP is reliable and robust.

Propofol as a Drug of Diversion: Changing Disposal Practices to Reduce Risk.

BACKGROUND: Propofol is a drug of diversion because of its high-volume use, lack of prescribed control mechanisms, and accessibility. As a result, intensive care unit nurses and other health care professionals are placed at unnecessary risk. Decreasing the risk of drug diversion can save lives, licenses, and livelihoods. LOCAL PROBLEM: Objectives were to reduce the risk of drug diversion and diminish the environmental impact of medication discarded down the sink. Disposing of residual propofol into activated carbon pouches was successful and sustainable in operating rooms at the study institution. Literature findings supported this intervention because of propofol's potential for abuse, ongoing diversion events, ease of access, poor control mechanisms, lack of standardization, excessive waste, and ecological impact. METHODS: The intensive care unit with the highest propofol use was selected to replicate the propofol disposal process used in the operating rooms. Activated carbon pouches and bottle cap removal tools were located in each intensive care unit room at the nurses' workstation for ease of use. Audits of unsecured waste bins and staff surveys of institutional policy awareness, disposal processes, barriers, and concerns were completed before and after the intervention. RESULTS: Survey results determined significant concern for drug diversion risk. The pilot project displayed success: 44.1% of propofol bottles in waste bins were full before the intervention and 0% were full afterward. CONCLUSION: Following institutional approval, this propofol disposal process was replicated in all intensive care units and the emergency department in the study institution.

Lipid body formation plays a central role in cell fate determination during developmental differentiation of Myxococcus xanthus.

Cell differentiation is widespread during the development of multicellular organisms, but rarely observed in prokaryotes. One example of prokaryotic differentiation is the gram-negative bacterium Myxococcus xanthus. In response to starvation, this gliding bacterium initiates a complex developmental programme that results in the formation of spore-filled fruiting bodies. How the cells metabolically support the necessary complex cellular differentiation from rod-shaped vegetative cells into spherical spores is unknown. Here, we present evidence that intracellular lipid bodies provide the necessary metabolic fuel for the development of spores. Formed at the onset of starvation, these lipid bodies gradually disappear until they are completely used up by the time the cells have become mature spores. Moreover, it appears that lipid body formation in M. xanthus is an important initial step indicating cell fate during differentiation. Upon starvation, two subpopulations of cells occur: cells that form lipid bodies invariably develop into spores, while cells that do not form lipid bodies end up becoming peripheral rods, which are cells that lack signs of morphological differentiation and stay in a vegetative-like state. These data indicate that lipid bodies not only fuel cellular differentiation but that their formation represents the first known morphological sign indicating cell fate during differentiation.

Evaluation of tacrolimus abbreviated area-under-the-curve monitoring in renal transplant patients who are potentially at risk for adverse events.

In a cohort of 32 renal transplant patients who are potentially at risk for adverse events, we compared tacrolimus (TAC) abbreviated AUC values calculated by a method developed in Asians (AUCw) with those derived for Caucasians (AUCa). The relationships between TAC trough (C0), abbreviated AUC, and biopsy results were also assessed. Forty-eight AUCs and 15 associated biopsies were evaluated. For AUCs obtained only from Caucasian patients, median AUCw value was lower than that of AUCa (104 vs. 115 ng×h/mL, n=29, p<0.0001). AUCs obtained from the two methods for all patients correlated with C0 (rs>0.72, n=48, p<0.0001). Median AUCw (72.9 vs. 174 ng×h/mL, p=0.043) and AUCa (81.0 vs. 203 ng×h/mL, p=0.043) were lower in patients experiencing biopsy-proven acute rejection (AR) than those with normal histology. C0 tended to be lower in biopsies showing AR>6 months post-transplant (5.80 vs. 11.0 ng/mL, p=0.110). Thus, lower abbreviated AUCs were obtained for Caucasians using a method developed in Asians. C0 correlated well with abbreviated AUCs. Lower C0 and AUC appeared to be associated with biopsy-proven AR>6 months post-transplant. Further prospective evaluation of TAC AUC and C0 monitoring in a larger cohort of patients is warranted.

Combat Wound Initiative program.

The Combat Wound Initiative (CWI) program is a collaborative, multidisciplinary, and interservice public-private partnership that provides personalized, state-of-the-art, and complex wound care via targeted clinical and translational research. The CWI uses a bench-to-bedside approach to translational research, including the rapid development of a human extracorporeal shock wave therapy (ESWT) study in complex wounds after establishing the potential efficacy, biologic mechanisms, and safety of this treatment modality in a murine model. Additional clinical trials include the prospective use of clinical data, serum and wound biomarkers, and wound gene expression profiles to predict wound healing/failure and additional clinical patient outcomes following combat-related trauma. These clinical research data are analyzed using machine-based learning algorithms to develop predictive treatment models to guide clinical decision-making. Future CWI directions include additional clinical trials and study centers and the refinement and deployment of our genetically driven, personalized medicine initiative to provide patient-specific care across multiple medical disciplines, with an emphasis on combat casualty care.

Effects of three intravitreal injections of aflibercept on the ocular circulation in eyes with age-related maculopathy.

AIMS: To investigate changes in ocular perfusion following three consecutive intravitreal injections with aflibercept for treatment of neovascular age-related macular degeneration (nAMD). METHODS: The study included 20 eyes from 20 Caucasian patients with unilateral nAMD and 20 fellow eyes. All nAMD eyes were treated with standard intravitreal injection of aflibercept (IVA; 2 mg). Measurements of ocular perfusion at the optic nerve head (ONH) and the choroid were performed with laser speckle flowgraphy (LSFG). Measurements were conducted at baseline, 1 week after the first injection, at the time point of the second and third injection as well as 1 month after the third injection. RESULTS: In treated eyes, mean blur rate (the main output parameter of LSFG) in the ONH microvasculature and in the choroid was significantly reduced 1 week after the first IVA treatment. The effect persisted throughout the entire follow-up period (p<0.001). No change in ocular perfusion was observed in fellow eyes. CONCLUSIONS: IVA for treatment of nAMD leads to a reduction in perfusion of the ONH and the choroid in the treated eye with no apparent effect on the fellow eye.

Patterns of morphologic alteration correlate with vision in diabetic macular oedema: a cross-sectional evaluation of patients using the SAVE II protocol.

PURPOSE: We sought to describe and evaluate patients with clinically significant diabetic macular oedema (CSME) according to the improved SAVE II protocol and correlate findings with visual acuity and systemic parameters in the outpatient clinic for DR (diabetic retinopathy) management. METHODS: This was a cross-sectional case series study of patients with CSME, regardless of prior treatment. Visual acuity testing was performed according to the Early Treatment of Diabetic Retinopathy Study (ETDRS) protocol. Optical coherence tomography (OCT) and fluorescence angiography (FA) were performed. All imaging data were evaluated according to an improved version of the SAVE grading protocol for CSME (SAVE II). The main outcome measures were SAVE II oedema types and best-corrected visual acuity. Additional parameters of a blood sample (fasting glucose, haemoglobin A1c, serum creatinine, triglycerides, cholesterol, low-density lipoproteins, and high-density lipoproteins) were taken. RESULTS: In total, 66 eyes of 66 patients were included. The mean age of the patients was 64.9 ± 8.2 years. Two eyes were classified as SAVE oedema type 1, 19 eyes as SAVE oedema type 2, 28 eyes as SAVE oedema type 3, and 28 eyes as SAVE oedema type 4, respectively. Central retinal thickness and laboratory parameters were not significantly different between the groups. There was a statistically significant difference in ETDRS visual acuity between the SAVE groups 2 and 4 (p < 0.001) with lower vision in group 4. There was no statistically significant difference between oedema types 2 and 3 (p = 0.065) and oedema types 3 and 4 (p = 0.13). CONCLUSION: There was a significant correlation between the four defined oedema types and visual acuity. Morphologic findings did not correlate with any of the evaluated blood parameters.

Aqueous humour cytokine changes during a loading phase of intravitreal ranibizumab or dexamethasone implant in diabetic macular oedema.

PURPOSE: To determine the effect of intravitreal ranibizumab and a dexamethasone implant on aqueous humour cytokine, protein and enzyme levels and to correlate findings to morphologic and functional changes. METHODS: In a prospective, randomized, controlled, double-blind study, patients with clinically significant diabetic macular oedema (CSME) were randomly allocated to receive either monthly intravitreal injections of ranibizumab (Lucentis, Novartis Pharma) or a single dexamethasone implant (Ozurdex, Pharm-Allergan) at baseline (BL). Aqueous humour samples were collected at BL and weeks 2, 8 and 20. RESULTS: The study included 18 eyes of 18 patients. In the dexamethasone implant group, soluble intercellular adhesion molecule 1 (sICAM-1) (weeks 2 and 8), CXCL9/monokine induced by gamma interferon (MIG) (weeks 2 and 8), soluble vascular cell adhesion protein 1 (sVCAM-1) (weeks 2 and 8) and monocyte chemo-attractant protein 1 (MCP-1) (week 2) levels were significantly decreased compared with baseline. In the ranibizumab group, placental growth factor (PIGF) (week 2) and vascular endothelial growth factor (VEGF) (week 2 and 8) levels were significantly decreased compared with baseline. No significant changes in central retinal thickness (CRT) or Early Treatment Diabetic Retinopathy Study (ETDRS) best corrected visual acuity (BCVA) were observed in the Ozurdex group at any time-points. ETDRS scores significantly increased at week 20 (84.88 ± 8.88 letters) compared with baseline (74.78 ± 14.85 letters), and the CRT decreased significantly at week 4 (381.00 ± 114.64 µm) compared with baseline (440 ± 144 µm) in the Lucentis group. CONCLUSION: The dexamethasone implant affected the aqueous cytokines and proteins MCP-1, sICAM-1, sVCAM-1 and MIG, whereas ranibizumab treatments reduced VEGF and PIGF levels. Morphological changes may diverge from cytokine changes. Results may indicate a rationale for a combination therapy for CSME using both agents, the dexamethasone implant and repeatedly administered ranibizumab injections.

Temporal Trends in Percutaneous Coronary Intervention and Coronary Artery Bypass Grafting: Insights From the Washington Cardiac Care Outcomes Assessment Program.

Background Patient selection and outcomes for percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) have changed over the past decade. However, there is limited information on outcomes for both revascularization strategies in the same population. The study evaluated temporal changes in risk profile, procedural characteristics, and clinical outcomes for PCI- and CABG-treated patients. Methods and Results We analyzed all PCI and isolated CABG between 2005 and 2017 in nonfederal hospitals in Washington State. Descriptive analysis was performed to evaluate temporal changes in risk profile and, risk-adjusted in-hospital mortality. Over the study period, 178 474 PCI and 36 592 CABG procedures were performed. PCI and CABG volume decreased by 2.9% and 22.6%, respectively. Compared with 2005-2009, patients receiving either form of revascularization between 2014 and 2017 had a higher prevalence of comorbidities including diabetes mellitus and hypertension and dialysis. Presentation with ST-segment-elevation myocardial infarction (17% versus 20%) and cardiogenic shock (2.4% versus 3.4%) increased for patients with PCI compared with CABG. Conversely, clinical acuity decreased for patients receiving CABG over the study period. From 2005 to 2017, mean National Cardiovascular Data Registry CathPCI mortality score increased for patients treated with PCI (20.1 versus 22.4, P<0.0001) and decreased for patients treated with CABG (18.8 versus 17.8, P<0.0001). Adjusted observed/expected in-hospital mortality ratio increased for PCI (0.98 versus 1.19, P<0.0001) but decreased for CABG (1.21 versus 0.74, P<0.0001) over the study period. Conclusions Clinical acuity increased for patients treated with PCI rather than CABG. This resulted in an increase in adjusted observed/expected mortality ratio for patients undergoing PCI and a decrease for CABG. These shifts may reflect an increased use of PCI instead of CABG for patients considered to be at high surgical risk.

Isoprenoids are essential for fruiting body formation in Myxococcus xanthus.

It was recently shown that Myxococcus xanthus harbors an alternative and reversible biosynthetic pathway to isovaleryl coenzyme A (CoA) branching from 3-hydroxy-3-methylglutaryl-CoA. Analyses of various mutants in these pathways for fatty acid profiles and fruiting body formation revealed for the first time the importance of isoprenoids for myxobacterial development.

Staphylococcus aureus ClpC ATPase is a late growth phase effector of metabolism and persistence.

Staphylococcus aureus Clp ATPases (molecular chaperones) alter normal physiological functions including an aconitase-mediated effect on post-stationary growth, acetate catabolism, and entry into death phase (Chatterjee et al., J. Bacteriol. 2005, 187, 4488-4496). In the present study, the global function of ClpC in physiology, metabolism, and late-stationary phase survival was examined using DNA microarrays and 2-D PAGE followed by MALDI-TOF MS. The results suggest that ClpC is involved in regulating the expression of genes and/or proteins of gluconeogenesis, the pentose-phosphate pathway, pyruvate metabolism, the electron transport chain, nucleotide metabolism, oxidative stress, metal ion homeostasis, stringent response, and programmed cell death. Thus, one major function of ClpC is balancing late growth phase carbon metabolism. Furthermore, these changes in carbon metabolism result in alterations of the intracellular concentration of free NADH, the amount of cell-associated iron, and fatty acid metabolism. This study provides strong evidence for ClpC as a critical factor in staphylococcal energy metabolism, stress regulation, and late-stationary phase survival; therefore, these data provide important insight into the adaptation of S. aureus toward a persister state in chronic infections.

Biosynthesis of 2-hydroxy and iso-even fatty acids is connected to sphingolipid formation in myxobacteria.

2-Hydroxy fatty acids can be found in several different organisms, including bacteria. In this study, we have studied the biosynthesis of 2-hydroxy fatty acids in the myxobacteria Myxococcus xanthus and Stigmatella aurantiaca, resulting in the identification of a family of stereospecific fatty acid alpha-hydroxylases. Although the stereospecificities of the hydroxylases differ between these two species, they share a common function in supporting fatty acid alpha-oxidation; that is, the oxidative shortening of fatty acids. Whereas in S. aurantiaca this process takes place during normal vegetative growth, in M. xanthus it takes place only under developmental conditions. We were also able to identify serine palmitoyltransferase encoding genes involved in sphingolipid biosynthesis as well as sphingolipids themselves in both types of myxobacteria, and were able to show that the alpha-hydroxylation reaction is in fact dependent on the presence of fatty acids bound to sphingolipids.

Identification of additional players in the alternative biosynthesis pathway to isovaleryl-CoA in the myxobacterium Myxococcus xanthus.

Isovaleryl-CoA (IV-CoA) is usually derived from the degradation of leucine by using the Bkd (branched-chain keto acid dehydrogenase) complex. We have previously identified an alternative pathway for IV-CoA formation in myxobacteria that branches from the well-known mevalonate-dependent isoprenoid biosynthesis pathway. We identified 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase (MvaS) to be involved in this pathway in Myxococcus xanthus, which is induced in mutants with impaired leucine degradation (e.g., bkd(-)) or during myxobacterial fruiting-body formation. Here, we show that the proteins required for leucine degradation are also involved in the alternative IV-CoA biosynthesis pathway through the efficient catalysis of the reverse reactions. Moreover, we conducted a global gene-expression experiment and compared vegetative wild-type cells with bkd mutants, and identified a five-gene operon that is highly up-regulated in bkd mutants and contains mvaS and other genes that are directly involved in the alternative pathway. Based on our experiments, we assigned roles to the genes required for the formation of IV-CoA from HMG-CoA. Additionally, several genes involved in outer-membrane biosynthesis and a plethora of genes encoding regulatory proteins were decreased in expression levels in the bkd(-) mutant; this explains the complex phenotype of bkd mutants including a lack of adhesion in developmental submerse culture.