Safety and feasibility of early discharge after transcatheter aortic valve implantation with ACURATE Neo-the POLESTAR trial

BACKGROUND

Transcatheter aortic valve implantation (TAVI) serves a growing range of patients with severe aortic stenosis (AS). TAVI has evolved to a streamlined procedure minimizing length of hospital stay.

AIMS

To evaluate the safety and efficacy of an early discharge (ED) strategy after TAVI.

METHODS

We performed an international, multi-center, prospective observational single-arm study in AS patients undergoing TAVI with the ACURATE valve platform. Eligibility for ED was assessed prior to TAVI and based on prespecified selection criteria. Discharge ≤ 48 h was defined as ED. Primary Valve Academic Research Consortium (VARC)-3-defined 30-day safety and efficacy composite endpoints were landmarked at 48 h and compared between ED and non-ED groups.

RESULTS

A total of 252 patients were included. The median age was 82 [25th-75th percentile, 78-85] years and the median Society of Thoracic Surgeons Predicted Risk of Mortality (STS-PROM) score was 2.2% [25th-75th percentile, 1.6-3.3]. ED and non-ED were achieved in 173 (69%) and 79 (31%) patients respectively. Monitoring for conduction disturbances was the principal reason for non-ED (33%). Overall, at 30 days, all-cause mortality was 1%, new permanent pacemaker rate was 4%, and valve- or procedure-related rehospitalization was 4%. There was no difference in the primary safety and efficacy endpoint between the ED and non-ED cohorts (OR 0.84 [25th-75th percentile, 0.31-2.26], p = 0.73, and OR 0.97 [25th-75th percentile, 0.46-2.06], p = 0.94). The need for rehospitalization was similarly low for ED and non-ED groups.

CONCLUSION

Early discharge after TAVI with the ACURATE valve is safe and feasible in selected patients. Rhythm monitoring and extended clinical observation protracted hospital stay.

Development of an atrial transseptal puncture procedure in horses to access the left heart: An ultrasound-guided jugular vein and transhepatic approach

BACKGROUND

Radiofrequency ablation has been successfully applied to treat right atrial arrhythmias in horses. Ablation of left-sided arrhythmias requires a retrograde transarterial approach which is complicated. In human medicine, the left atrium is accessed through transseptal puncture (TSP) of the fossa ovalis (FO) using a caudal approach via the femoral vein.

OBJECTIVES

To develop a zero fluoroscopy TSP technique for horses using a jugular vein (cranial) and transhepatic (caudal) approach.

STUDY DESIGN

In vivo experimental study.

METHODS

Transseptal puncture was performed in 18 horses admitted for euthanasia and donated for scientific research under general anaesthesia: using a jugular vein approach (10 horses), a transhepatic approach (2 horses) or both (6 horses). Radiofrequency energy was applied on a guidewire to perforate the FO and allow sheath advancement under intracardiac and transthoracic echocardiographic guidance. Puncture lesions were inspected post-mortem.

RESULTS

Transseptal puncture was successful in 17/18 horses, of which 15/16 jugular vein approaches and 5/8 transhepatic approaches. Failure was due to technical malfunction, inability to advance the guidewire toward the heart and inability to advance the sheath through the FO. Intracardiac echocardiography was essential to safely guide the puncture process. Atrial arrhythmias caused by the TSP occurred in 13/18 horses. Puncture lesions were found in the right atrium in the FO region, and left atrium ventral to pulmonary vein ostium III.

MAIN LIMITATIONS

Because in several horses two approaches were tested consecutively, it cannot be excluded that the second TSP was performed at the previous puncture site. Due to the developmental nature of the study the approaches were not randomised and did not allow comparison.

CONCLUSION

Transseptal puncture is feasible in horses using ultrasound guidance and allows for electrophysiological exploration of the left heart. Further studies are needed to evaluate post-operative follow-up.

Enhancing Transcatheter Aortic Valve Implantation (TAVI) outcomes through virtual proctoring: a case series analysis

Transcatheter Aortic Valve Implantation (TAVI) represents a pivotal advancement in the management of severe aortic stenosis, offering a minimally invasive alternative to surgical valve replacement. Despite its widespread adoption, the complexity of TAVI procedures, especially in high-risk anatomical scenarios such as valve-in-valve interventions, necessitates ongoing educational support for operators. This article explores the implementation of a virtual proctoring system for complex TAVI procedures, evaluating its feasibility, educational value, and impact on procedural success and safety.

A systematic algorithm for large-bore arterial access closure after TAVI: the TAVI-MultiCLOSE study

BACKGROUND

Despite transcatheter aortic valve implantation (TAVI) having become a routine procedure, access site bleeding and vascular complications are still a concern which contribute to procedure-related morbidity and mortality.

AIMS

The TAVI-MultiCLOSE study aimed to assess the safety and efficacy of a new vascular closure algorithm for percutaneous large-bore arterial access closure following transfemoral (TF)-TAVI.

METHODS

All consecutive TF-TAVI cases in which the MultiCLOSE vascular closure algorithm was used were prospectively included in a multicentre, observational study. This stepwise algorithm entails the reinsertion of a 6-8 Fr sheath (primary access) following the initial preclosure with one or two suture-based vascular closure devices (VCDs). This provides the operator with the opportunity to perform a quick and easy angiographic control and tailor the final vascular closure with either an additional suture- or plug-based VCD, or neither of these.

RESULTS

Among 630 patients who underwent TF-TAVI utilising the MultiCLOSE algorithm, complete arterial haemostasis was achieved in 616 patients (98%). VCD failure occurred in 14 patients (2%), treated with either balloon inflation (N=1), covered stent (N=12) or surgical repair (N=1). Overall, this vascular closure approach resulted in a minor and major vascular complication rate of 2.2% and 0.6%, respectively. At 30 days, only one new minor vascular complication (0.2%) was noted. In-hospital and 30-day all-cause mortality rates were 0.2% and 1.0%, respectively.

CONCLUSIONS

Use of the MultiCLOSE vascular closure algorithm was demonstrated to contribute to an easy, safe, efficacious and durable vascular closure after TF-TAVI, resulting in a major vascular complication rate of less than 1%.

Transcatheter aortic valve implantation versus surgical aortic valve replacement in severe aortic stenosis patients at low surgical mortality risk: a cost-effectiveness analysis in Belgium

BACKGROUND

Transcatheter aortic valve implantation (TAVI) with the SAPIEN 3 device has recently shown significant clinical benefits, compared to surgical aortic valve replacement (SAVR), in patients at low risk for surgical mortality (PARTNER 3 trial, NCT02675114). Currently in Belgium, TAVI use is restricted to high-risk or inoperable patients with severe symptomatic aortic stenosis (sSAS). This cost-utility analysis aimed to assess whether TAVI with SAPIEN 3 could lead to potential cost-savings compared with SAVR, in the low-risk sSAS population in Belgium.

METHODS

A previously published, two-stage, Markov-based cost-utility model was used. Clinical outcomes were captured using data from PARTNER 3 and the model was adapted for the Belgian context using cost data from the perspective of the Belgian National Healthcare System, indexed to 2022. A lifetime horizon was chosen. The model outputs included changes in direct healthcare costs, survival and health-related quality of life using TAVI versus SAVR.

RESULTS

TAVI with SAPIEN 3 provides meaningful clinical and cost benefits over SAVR, in terms of an increase in quality-adjusted life years (QALYs) of 0.94 and cost-saving of €3 013 per patient. While initial procedure costs were higher for TAVI compared with SAVR, costs related to rehabilitation, disabling stroke, treated atrial fibrillation, and rehospitalization were lower. The cost-effectiveness of TAVI over SAVR remained robust in sensitivity analyses.

CONCLUSION

TAVI with SAPIEN 3 may offer a meaningful alternative intervention to SAVR in Belgian low-risk patients with sSAS, showing both clinical benefits and cost savings associated with post-procedure patient management.

Impact of routine use of a cerebral protection device on the TAVR procedure and its short-term outcomes: a single-centre experience

BACKGROUND

Stroke is a major concern in transcatheter aortic valve replacement (TAVR). The introduction of a cerebral protection devices may counteract the evolution towards minimally invasive TAVR. At this time, there is insufficient data to support the routine use of these devices.

METHODS

We aimed to evaluate the outcome of the routine use of the Sentinel Cerebral protection system^® (CPS) in patients undergoing TAVR, after completing a CT-based screening process for feasibility of Sentinel implantation. We report our initial experience with the routine implementation of the Sentinel CPS in all anatomically suitable patients undergoing TAVR. We retrospectively compared the procedural characteristics and outcomes between all TAVR patients treated with (n = 78) and without (n = 79) intended Sentinel.

RESULTS

The Sentinel CPS could successfully be deployed in 99% of intended cases after CT feasibility screening. TAVR procedures with Sentinel CPS were not longer than procedures without Sentinel use (89 ± 20 versus 120 ± 50 min, p = 0.007). Sentinel CPS use was not associated with an increased risk of procedural complications. Stroke was observed in none (0%) of the Sentinel CPS patients, and in 6.3% of the non-Sentinel CPS patients (p = 0.05). The finding of stroke was associated with a high risk of early postprocedural mortality: 60% of stroke patients died within 3 months.

CONCLUSION

Routine use of the Sentinel CPS in CT-screened TAVR patients is feasible with high procedural success, without significant adverse events and without counteracting the evolution towards minimally invasive TAVR. Clinically relevant stroke was observed in none of the Sentinel CPS patients.

Rationale and design of the Project to look for early discharge in patients undergoing TAVR with ACURATE (POLESTAR Trial)

BACKGROUND

Transcatheter aortic valve replacement (TAVR) is now an established treatment strategy for elderly patients with symptomatic aortic stenosis (AS) across the entire operative risk spectrum. Streamlined TAVR protocols along with reduced procedure time and expedited ambulation promote early hospital discharge. Selection of patients suitable for safe early discharge after TAVR might improve healthcare efficiency.

STUDY DESIGN

The POLESTAR trial is an international, multi-center, prospective, observational study which aims to evaluate the safety of early discharge in selected patients who undergo TAVR with the supra-annular functioning self-expanding ACURATE Neo transcatheter heart valve (THV). A total of 250 patients will be included based on a set of baseline criteria indicating potential early discharge (within 48 h post-TAVR). Primary study endpoints include Valve Academic Research Consortium (VARC)-3 defined safety at 30 days and VARC-3 defined efficacy at 30 days and 1 year. Endpoints will be compared between early discharge and non-early discharge cohorts with a distinct landmark analysis at 48 h post-TAVR. Secondary endpoints include quality of life assessed using EQ5D-5L and Kansas City Cardiomyopathy Questionnaire (KCCQ) questionnaires and resource costs compared between discharge groups.

SUMMARY

The POLESTAR trial prospectively evaluates safety and feasibility of an early discharge protocol for TAVR using the ACURATE Neo THV.

SPECT-CCTA: guiding treatment in ischaemic heart disease

Combining myocardial perfusion single photon emission computed tomography (SPECT-MPI) and coronary computed tomography angiography (CCTA) is an interesting hybrid imaging option in modern cardiovascular medicine. The integrated hybrid technique has a number of advantages compared to visual side-by-side analysis of the separate modalities. CT attenuation map can correct for attenuation artefacts and thus improve the diagnostic accuracy of SPECT-MPI. Moreover, the anatomical information of the CCTA and the perfusion map of SPECT-MPI allow for vessel-based correlation and culprit vessel identification. Combining SPECT-MPI with CCTA is an appealing tool in the work-up of complex ischaemic heart disease and might help determine the optimal treatment strategy. This case series illustrates the role of SPECT-CCTA in decision-making of revascularization strategy in complex ischaemic heart disease.

The evolution of the CTO-PCI landscape in Belgium and Luxembourg: a four-year appraisal

BACKGROUND

To chart the evolution of the CTO-PCI landscape in Belgium and Luxembourg, the Belgian Working Group on Chronic Total Occlusions (BWGCTO) was established in 2016.

METHODS

Between May 2016 and December 2019, patients undergoing a CTO-PCI treatment were prospectively and consecutively enrolled. Twenty-one centres in Belgium and one in Luxembourg participated. Individual operators had mixed levels of expertise in treating CTO lesions. Demographic, angiographic, procedural parameters and incidence of major adverse cardiac and cerebrovascular events (MACCE) were systematically registered.

RESULTS

Over a four-year enrolment period, 1832 procedures were performed in 1733 patients achieving technical success in 1474 cases (80%), with an in-hospital MACCE rate of 2.3%. Fifty-nine (3%) cases were re-attempt procedures of which 41 (69%) were successful. High-volume centres treated more complex lesions (mean J-CTO score: 2.15 ± 1.21) as compared to intermediate (mean J-CTO score: 1.72 ± 1.23; p < 0.001) and low-volume centres (mean J-CTO score: 0.99 ± 1.21; p = 0.002). Despite this, success rates did not differ between centres (p = 0.461). Overall success rates did not differ over time (p = 0.810). High-volume centres progressively tackled more complex CTOs while keeping success rates stable. In all centres, the most applied strategy was antegrade wire escalation (83%). High-volume centres more often successfully applied antegrade dissection and re-entry and retrograde techniques in lesions with higher complexity.

CONCLUSION

With variable experience levels, operators treated CTOs with high success and relatively few complications. Although AWE remains the most used technique, it is paramount for operators to be skilled in all contemporary techniques in order to be successful in more complex CTOs.

A plethora of manifestations following a Mycoplasma pneumoniae infection: a case report

Mycoplasma pneumoniae infection can present with a plethora of symptoms and result in a systemic vasculitis by activating a cascade of autoimmune reactions. In this case report, a young man without relevant past medical history was admitted to the hospital with diarrhea, abdominal pain and spiking fever. A CT-scan showed terminal ileitis. A 5-day broad spectrum antibiotic treatment (ciprofloxacin/clindamycin) did not result in any clinical improvement. On the contrary, the patient developed a cholestatic hepatitis, bilateral anterior uveitis and a dry cough. Extensive serological testing finally led to the diagnosis of a M. pneumoniae infection by paired serology (≥4-fold rise in IgG titer). In the diagnostic work-up, a PET-CT was performed and showed increased tracer uptake in the carotids and vertebral arteries, suggesting the diagnosis of vasculitis. After start of azithromycin and low-dose corticosteroids (0.5 mg/kg/day), a gradual clinical and biochemical improvement was observed. But subsequently, the patients relapsed and presented with an acute coronary syndrome. Coronary angiography revealed aneurysmatic deformation of the three coronary arteries, leading to the assumption of coronary vasculitis. Clinical improvement was achieved with high-dose corticosteroids (1 mg/kg/day). This case shows that M. pneumoniae is not merely a pulmonary infection, but that its primary symptoms can be diverse and misleading. All clinicians should be aware of its extrapulmonary manifestations.

Transcatheter left atrial appendage occlusion for stroke prevention in patients with atrial fibrillation: results from the Belgian registry

AIMS

This study aimed to assess the safety and efficacy at midterm follow-up of left atrial appendage occlusion (LAAO) using different devices, in real life in Belgium.

METHODS AND RESULTS

Between June 2009 and November 2016, 457 consecutive patients (63% male, 75±12 yrs, CHA2DS2-VASc 4±0.6, HAS-BLED 3.5±0.7) undergoing LAAO were included. Technical success was 97.1%. There were 19 periprocedural major adverse events (4.1%) including three deaths (0.6%), nine tamponades (1.9%), four major bleedings (0.8%) and two device embolisations (0.4%). Among patients successfully implanted having a complete follow-up (672 patient-years, median follow-up 370 days), the actual annual stroke rate was 1.2%, lower than the expected stroke risk of 4% (70% reduction). The observed bleeding rate was 2%, while the calculated risk was 3.7% (46% reduction). Kaplan-Meier analysis showed a similar overall survival (93±2% and 87±3% versus 91±3% and 87±4%; p=0.35) and event-free survival (92±2% and 84±3% versus 88±3% and 80±5%; p=0.17) at one and two years, for the ACP/Amulet versus the WATCHMAN groups of patients, respectively.

CONCLUSIONS

The data from the Belgian left atrial appendage occlusion registry suggest that the procedure is effective and relatively safe in a real-world setting, using either the WATCHMAN or the ACP/Amulet device.

Assessing the landscape of percutaneous coronary chronic total occlusion treatment in Belgium and Luxembourg: the Belgian Working Group on Chronic Total Occlusions (BWGCTO) registry

Background: Important developments in materials, devices, and techniques have improved outcomes of chronic total occlusion (CTO) percutaneous coronary intervention (PCI), and resulted in a growing interest in CTO-PCI. The Belgian Working Group on Chronic Total Occlusions (BWGCTO) working group aims to assess the evolution within the CTO-PCI landscape over the next years. Methods: From May 2016 onwards, patients undergoing CTO-PCI were included in the BWGCTO registry by 15 centres in Belgium and Luxemburg. Baseline, angiographic, and procedural data were collected. Here, we report on the one-year in-hospital outcomes. Results: Over the course of one year, 411 procedures in 388 patients were included with a mean age of 64 ± 11 years. The majority were male (81%). Relatively complex CTOs were treated (Japanese CTO score =2.2 ± 1.2) with a high procedure success rate (82%). Patient- and lesion-wise success rates were 83 and 85%, respectively. Major adverse in-hospital events were acceptably low (3.4%). Antegrade wire escalation technique was applied most frequently (82%). On the other hand, antegrade dissection and re-entry and retrograde strategies were more frequently applied in higher volume centres and successful for lesions with higher complexity. Conclusion: Satisfactory procedural outcomes and a low rate of adverse events were obtained in a complex CTO population, treated by operators with variable experience levels. Antegrade wire escalation was the preferred strategy, regardless of operator volume.

The SABRE Trial (Sirolimus Angioplasty Balloon for Coronary In-Stent Restenosis): Angiographic Results and 1-Year Clinical Outcomes

OBJECTIVES

The aim of this first-in-human study was to assess the safety and effectiveness of the Virtue sirolimus-eluting balloon in a cohort of patients with in-stent restenosis (ISR).

BACKGROUND

Angioplasty balloons coated with the cytotoxic drug paclitaxel have been widely used for ISR treatment. The Virtue angioplasty balloon (Caliber Therapeutics, New Hope, Pennsylvania) delivers sirolimus in a nanoencapsulated liquid formulation. This clinical trial is the first to examine a sirolimus-eluting balloon for ISR.

METHODS

In this prospective, single-arm feasibility study at 9 European centers, 50 ISR patients were treated with the Virtue balloon. Angiographic measurements at 6 months are reported, along with 12-month clinical follow-up.

RESULTS

Procedural success in the intention-to-treat population was 100%. The primary safety endpoint was target lesion failure (TLF) (cardiac death, target vessel myocardial infarction, and clinically driven target lesion revascularization) assessed at 30 days (0%, n = 50). The primary performance endpoint was in-segment late lumen loss (LLL) at 6 months (0.31 ± 0.52 mm; n = 47). Secondary 6-month endpoints include binary restenosis (19.1%), diameter stenosis (30.3 ± 19.9%), and major adverse cardiac events (MACE) (10.2%, n = 49). In the 36-patient per-protocol population (excluding major protocol violations and previously stented ISR), LLL was 0.12 ± 0.33 mm at 6 months. Clinical outcomes at 1 year for the intention-to-treat group were 12.2% TLF and 14.3% MACE and for the per-protocol population were 2.8% TLF and 2.8% MACE.

CONCLUSIONS

This first-in-human study showed excellent procedural success for the Virtue sirolimus-eluting angioplasty balloon, 6-month LLL rates in line with current stent-free ISR treatment options, and clinical outcomes that warrant further evaluation in dedicated randomized studies.

Impact of gender difference in hospital outcomes following percutaneous coronary intervention. Results of the Belgian Working Group on Interventional Cardiology (BWGIC) registry

AIMS

To determine whether there are gender-based differences in in-hospital outcomes among patients undergoing percutaneous coronary intervention (PCI).

METHODS AND RESULTS

We studied a large cohort using clinical data from a registry of 130,985 PCI procedures in Belgium, from January 2006 to February 2011. Compared to males, females were significantly older (70.3 vs. 64.8 years), and were more frequently diabetic or hypertensive. Men smoked more and more frequently had previous myocardial infarction (MI), previous PCI or previous coronary artery bypass graft (CABG) surgery. Coronary artery disease (CAD) was less severe in women, and PCI to the left anterior descending artery was more common in female patients. Unadjusted in-hospital mortality rates were higher in females versus males (2.5% for women and 1.6% for men, p<0.0001). After multivariable analysis, female gender remained an independent predictor of mortality (odds ratio 1.35, 95% CI: 1.22-1.49, p<0.0001).

CONCLUSIONS

Gender-based differences in hospital mortality rates after PCI were observed in this large registry. Female sex remained an independent predictor of mortality after multivariable adjustment.

Alcohol septal ablation to overcome shock

A 69-year-old man, known with hypertrophic obstructive cardiomyopathy (HOCM), was referred to our hospital because of progressive hypoxaemia and sepsis after admission for respiratory infection. Once at the emergency department, cardiopulmonary resuscitation, intubation and mechanical ventilation were necessary. Despite vasopressors and colloids the patient remained haemodynamically unstable. Because of the conviction that the distributive shock, caused by sepsis, was worsened by an associated obstructive shock related to the HOCM, an alcohol septal ablation (ASA) was attempted in these acute circumstances. Immediately after the ASA the gradient over the left ventricular outflow tract disappeared and the mean arterial pressure and oxygenation increased. Despite his cardiovascular recuperation the patient died a couple of days later. Nevertheless we achieved an improvement of the haemodynamic situation of this patient with HOCM by performing an urgent ASA.

Comparison of assessment of native coronary arteries by standard versus three-dimensional coronary angiography

Vessel foreshortening is a major limitation of standard coronary angiography due to the 2-dimensional representation of 3-dimensional structures. Three-dimensional models may overcome it. The aim of this study was to compare measurements of coronary segments from quantitative coronary angiography (QCA) in an operator-selected "working view" of standard 2-dimensional coronary angiography with those from 3-dimensional coronary angiography (3D-CA) reconstruction models, which are automatically generated from software applied to rotational coronary angiographic acquisitions. Patients who underwent percutaneous coronary intervention were considered. Two or 3 segments of the artery needing treatment were prespecified, using bifurcations as edges. The operator selected a working view from standard angiography as the view best representing each segment. Rotational angiography was performed, allowing 3-dimensional reconstruction of the selected segments. Additionally a marker guidewire (with 4 markers 10 mm away from one another at the distal tip) was used to further measure segment length, and it was considered the "gold standard" reference. In 36 patients, 81 segments from 12 left anterior descending, 12 circumflex, and 12 right coronary arteries were evaluated. Three-dimensional coronary angiography was always feasible. Although reference vessel diameter was not different between 3D-CA and QCA (p >0.05), segment length measurements were on average 2.3 +/- 2.5 mm longer with 3D-CA than with QCA (p <0.001) and 0.4 +/- 1.8 mm longer than with marker guidewire measurement (p = 0.047). Marker guidewire measurements were 1.9 +/- 2.8 mm longer than QCA measurements (p <0.001). According to Bland-Altman plots, 3D-CA and marker guidewire measurements had the best agreement. In conclusion, 3-dimensional coronary modeling is highly feasible and yields more accurate assessments of the lengths of coronary segments than standard QCA.

"Virtual" in-vivo bench test for bifurcation stenting with "StentBoost"

"StentBoost" is a new angiographic technique that allows improved angiographic visualization of stents deployed in coronary arteries, by enhancing the X-ray focus of the region where the stent is placed. Using this technique we were able to assess the deformation and the expansion of a stent deployed to treat a bifurcation lesion between the mid-left anterior descending (LAD) artery and a big second diagonal branch, during sequential inflations of: (1) the stent per se in the LAD, (2) the ostium of the diagonal branch through the stent struts, (3) the stent again with a non compliant balloon, and (4) both branches with the kissing balloon technique. "StentBoost" guided our clinical and angiographic decision-making process and allowed us to create a "virtual" bench test of the stent deployed at the level of the bifurcation treated.

An AFLP-based genome-wide mapping strategy

To efficiently determine the chromosomal location of phenotypic mutants, we designed a genome-wide mapping strategy that can be used in any crop for which a dense AFLP (Amplified Fragment Length Polymorphism) map is available or can be made. The AFLP technique is particularly suitable to initiate map-based cloning projects because it detects many markers per reaction. First a standard set of AFLP primer combinations that results in a framework of AFLP markers well dispersed over the genome is selected. These primer combinations are applied to a limited number of mutant individuals from a segregating population to register linkage and non-linkage of the AFLP markers to the gene-of-interest. Further delineation of the area of interest is accomplished by analyzing the remaining recombinants and additional mutant individuals with AFLP markers that lie within the identified region. We illustrate the usefulness of the method by mapping three rotunda ( ron) leaf-form mutant loci of Arabidopsis thaliana and show that in the initial phase of map-based cloning projects a 400-600 kb interval can be identified for the average mutant locus within a few weeks. Once such an area is identified and before initiating the more time-consuming fine-mapping procedure, it is essential to examine publicly available databases for candidate genes and known mutants in the identified region. The 390-kb interval on chromosome 4 that harbors the ron2 mutation, also carries a known flower mutant, leunig ( lug); upon crossing, the two mutants appeared to be allelic. When no such candidates are found, the mapping procedure should be continued. We present a strategy to efficiently select recombinants that can be used for fine mapping.

The att locus of Rhodococcus fascians strain D188 is essential for full virulence on tobacco through the production of an autoregulatory compound

The ability of Rhodococcus fascians strain D188 to provoke leafy gall formation on a variety of plant species is correlated with the linear plasmid pFiD188, on which different pathogenicity loci were identified. The att locus affects the severity of symptom development on tobacco, whereas the fas locus is essential for virulence. To gain insight into the function of the att locus, sequence and expression analyses were performed. The att locus contains nine open reading frames homologous to arginine and beta-lactam biosynthetic genes. att gene expression is transcriptionally induced by leafy gall extracts, but not by extracts of uninfected plants, and depends on the attR gene that encodes a LysR-type transcriptional regulator. The att locus proves to be essential for the formation of inducing factors (IFs) that are present in gall extracts. Because the induction of the fas locus also requires the presence of IFs in gall extracts, the att locus is proposed to play an important role in regulating the expression of the virulence loci of R. fascians.

The plant pathogen Rhodococcus fascians colonizes the exterior and interior of the aerial parts of plants

Rhodococcus fascians is a plant-pathogenic bacterium that causes malformations on aerial plant parts, whereby leafy galls occur at axillary meristems. The colonization behavior on Nicotiana tabacum and Arabidopsis thaliana plants was examined. Independent of the infection methods, R. fascians extensively colonized the plant surface where the bacteria were surrounded by a slime layer. R. fascians caused the collapse of epidermal cells and penetrated intercellularly into the plant tissues. The onset of symptom development preceded the extensive colonization of the interior. The meristematic regions induced by pathogenic strain D188 were surrounded by bacteria. The nonpathogenic strain, D188-5, colonized the exterior of the plant equally well, but the linear plasmid (pFiD188) seemed to be involved in the penetration efficiency and colonization of tobacco tissues.

Degradation of starchy endosperm cell walls in nongerminating sterilized barley by fungi

Strains of fungi from different origins, including isolates of the natural microflora of barley, were screened for their ability to modify barley starchy endosperm cell walls in situ. In an initial step, fungi were selected that degrade the major component of the cell walls, that is, (1-->3),(1-->4)-beta-D-glucan, in vitro on artificial media. Nongerminating, sterilized barley, obtained by gamma-irradiation, was inoculated with such fungi and subjected to solid state fermentation under conditions resembling those of a traditional malting process. For some strains of fungi, a clear correlation between the production of endo-beta-glucanase and the friability of the treated kernels was found. Image analysis of Calcofluor stained longitudinal sections of barley kernels fermented with the endo-beta-glucanase producing strains showed that starchy endosperm cell walls were modified. As malt quality is inversely related to its (1-->3),(1-->4)-beta-D-glucan content, the selected strains have high potential to be used as starter cultures during malt production, contributing to the processing quality of the final product.

Kinetic analysis and modelling of combined high-pressure-temperature inactivation of the yeast Zygosaccharomyces bailii

Eight foodborne yeasts were screened for sensitivity to high-pressure (HP) inactivation under a limited number of pressure-temperature combinations. The most resistant strains were Zygoascus hellenicus and Zygosaccharomyces bailii. The latter was taken for a detailed study of inactivation kinetics over a wide range of pressures (120-320 MPa) and temperatures (-5 to 45 degrees C). Isobaric and isothermal inactivation experiments were conducted in Tris-HCl buffer pH 6.5 for 48 different combinations of pressure and temperature. Inactivation was biphasic, with a first phase encompassing four to six decades and being described by first-order kinetics, followed by a tailing phase. Decimal reduction times (D) were calculated for the first-order inactivation phase and their temperature and pressure dependence was described. At constant temperature, D decreased with increasing pressure as expected. At constant pressure, D showed a maximum at around 20 degrees C, and decreased both at lower and at higher temperatures. A mathematical expression was developed to describe accurately the inactivation of Z. bailii as a function of pressure and temperature under the experimental conditions employed. A limited number of experiments in buffer at low pH (3-6) suggest that the model is, in principle, applicable at low pH. In apple and orange juice however, higher inactivation than predicted by the model was achieved.

Escherichia coli mutants resistant to inactivation by high hydrostatic pressure

Alternating cycles of exposure to high pressure and outgrowth of surviving populations were used to select for highly pressure-resistant mutants of Escherichia coli MG1655. Three barotolerant mutants (LMM1010, LMM1020, and LMM1030) were isolated independently by using outgrowth temperatures of 30, 37, and 42 degrees C, respectively. Survival of these mutants after pressure treatment for 15 min at ambient temperature was 40 to 85% at 220 MPa and 0.5 to 1.5% at 800 MPa, while survival of the parent strain, MG1655, decreased from 15% at 220 MPa to 2 x 10(-8)% at 700 MPa. Heat resistance of mutants LMM1020 and LMM1030 was also altered, as evident by higher D values at 58 and 60 degrees C and reduced z values compared to those for the parent strain. D and z values for mutant LMM1010 were not significantly different from those for the parent strain. Pressure sensitivity of the mutants increased from 10 to 50 degrees C, as opposed to the parent strain, which showed a minimum around 40 degrees C. The ability of the mutants to grow at moderately elevated pressure (50 MPa) was reduced at temperatures above 37 degrees C, indicating that resistance to pressure inactivation is unrelated to barotolerant growth. The development of high levels of barotolerance as demonstrated in this work should cause concern about the safety of high-pressure food processing.