Mitral Annular Disjunction in Idiopathic Ventricular Fibrillation Patients: Just a Bystander or a Potential Cause?

AIMS

Previously, we demonstrated that inferolateral mitral annular disjunction (MAD) is more prevalent in patients with idiopathic ventricular fibrillation (IVF) than in healthy controls. In the present study, we advanced the insights into the prevalence and ventricular arrhythmogenicity by inferolateral MAD in an even larger IVF cohort.

METHODS AND RESULTS

This retrospective multicentre study included 185 IVF patients (median age 39 [27, 52] years, 40% female). Cardiac magnetic resonance images were analysed for mitral valve and annular abnormalities and late gadolinium enhancement. Clinical characteristics were compared between patients with and without MAD. MAD in any of the 4 locations was present in 112 (61%) IVF patients and inferolateral MAD was identified in 24 (13%) IVF patients. Mitral valve prolapse (MVP) was found in 13 (7%) IVF patients. MVP was more prevalent in patients with inferolateral MAD compared with patients without inferolateral MAD(42% vs. 2%, p < 0.001). Proarrhythmic characteristics in terms of a high burden of premature ventricular complexes (PVC) and non-sustained ventricular tachycardia (VT) were more prevalent in patients with inferolateral MAD compared to patients without inferolateral MAD (67% vs. 23%, p < 0.001 and 63% vs 41%, p = 0.046, respectively). Appropriate implantable cardioverter defibrillator therapy during follow-up was comparable for IVF patients with or without inferolateral MAD (13% vs. 18%, p = 0.579).

CONCLUSION

A high prevalence of inferolateral MAD and MVP is a consistent finding in this large IVF cohort. The presence of inferolateral MAD is associated with a higher PVC burden and non-sustained VTs. Further research is needed to explain this potential interplay.

Post-infarct VT substrate ablation based on evoked delayed potential elimination as well-defined target: results from a prospective multicenter study

Background

In patients with VT after myocardial infarction (MI), substrate-based ablation is superior to approaches that target clinical and tolerated VTs only. Different substrate modification strategies have been reported. However, proposed ablation targets are prone to operator interpretation (e.g. abnormal electrograms). Accordingly, ablation results can also be operator dependent. Evoked delayed potentials (EDP) are a well-defined target. Elimination of EDP has been effective to prevent VT recurrence in a retrospective, single center cohort.

Aim

(1)To evaluate the outcome of EDP ablation in a prospective cohort of patients included on an intention-to-treat principle and (2)to assess the outcome of EDP ablation following one uniform protocol when performed in centers without prior experience with this strategy.

Methods

Consecutive patients referred for post-MI VT ablation were prospectively enrolled in one center with extensive experience in EDP ablation and 5 centers with no prior experience. Substrate mapping focused on EDP identification followed a uniform protocol across all centers. In brief, all electrograms located within the infarct area were analyzed during sinus rhythm, RV pacing at a fixed rate and during the application of one short-coupled RV extra-stimulus (S2). Sites showing low-voltage, nearfield electrograms with &gt;10ms delay or block in response to S2 were categorized as EDP and targeted for ablation. After ablation, re-mapping to confirm EDP elimination and a complete stimulation protocol (up to 4 extra's from RV and LV) were performed. Patients were followed for VT recurrence and mortality.

Results

130 patients (69±10 years, 87% men, 42% anterior MI, LVEF 34% (IQR 24–43), 71% NYHA II–III, 42% on amiodarone, 52% ≥1 ICD shock, 22% with electrical storm or incessant VT) were included. The extra-stimulation protocol was systematically conducted in 127 (98%) patients and in 121 (93%), EDPs were identified. EDPs were successfully eliminated in 117/121 (97%) patients. After 23 (IQR 14–35) min of RF, 102 (78%) patients were rendered non-inducible. Median procedural duration was 212 (IQR 179–262) min. During follow-up of 14 (IQR 8–18) months, 36 (28%) patients had VT recurrence and 13 (10%) died or received a LVAD. VT-free survival was 79% (95% CI: 72–86) and 72% (95% CI: 63–80) at 6 and 12 months follow-up. Of note, VT-free survival at 12 month was not significantly different between patients undergoing the procedure in centers with and without prior experience in EDP ablation (76% (95% CI: 61–90) vs. 70% (95% CI: 59–81); P=0.269).

Conclusion

In a large prospective cohort of patients with post-MI VT, substrate ablation based on EDP elimination resulted in excellent long-term outcome. Of importance, procedural outcomes were similar in centers with or without experience in EDP ablation, indicating that this approach can be easily reproduced by operators previously not familiar with the technique.

Funding Acknowledgement

Type of funding sources: None.

Post-infarct VT substrate ablation based on evoked delayed potential elimination as well-defined target : results from a prospective multicenter study

Funding Acknowledgements

Type of funding sources: None.

Background

Substrate ablation is superior to approaches that target clinical and tolerated VTs in patients with post-myocardial infarction (MI) VT. Different substrate modification strategies have been reported. However, proposed ablation targets are prone to operator interpretation (e.g. abnormal electrograms). Accordingly, ablation results can also be operator dependent. Evoked delayed potentials (EDP) are a well-defined target. Elimination of EDP has been effective to prevent VT recurrence in a retrospective, single center cohort.

Aim

(1)To evaluate the outcome of EDP ablation in a prospective cohort of patients included on an intention-to-treat principle and (2)to assess the outcome of EDP ablation following one uniform protocol when performed in centers without prior experience with this strategy.

Methods

Consecutive patients referred for post-MI VT ablation were prospectively enrolled in one center with extensive experience in EDP ablation and 5 centers with no prior experience. Substrate mapping focused on EDP identification followed a uniform protocol across all centers. In brief, all electrograms located within the infarct area were analyzed during sinus rhythm, RV pacing at a fixed rate and during the application of one short-coupled RV extra (S2). Sites showing low-voltage, nearfield electrograms with &gt;10ms delay or block in response to S2 were categorized as EDP and targeted for ablation. After ablation, re-mapping to confirm EDP elimination and a complete stimulation protocol (up to 4 extra’s from RV and LV) were performed.

Results

131 patients (69±10 years, 87% men, 42% anterior MI, LVEF 33±11%, 70% NYHA II-III, 43% on amiodarone, 52% ≥1 ICD shock, 34% with electrical storm or incessant VT) were included. Multipolar catheters or catheters with micro-electrodes in the tip were used in 53%. The extra-stimulation protocol was systematically conducted in 127 (97% ) patients and in 121 (92%), EDPs were identified. EDPs were successfully eliminated in 117/121 (97%) patients. After 23 (IQR 14-35) min of RF, 101 (77%) patients were rendered non-inducible. Median procedural duration was 213 (IQR 180-267) min. During follow-up of 14 (IQR 8-19) months, 36 (27%) patients had VT recurrence and 14 (11%) died or received a LVAD. VT-free survival was 78% (CI95% 71-85) and 71% (CI95% 63-80) at 6 and 12 months follow-up. Of note, VT-free survival at 12 month was not significantly different between patients undergoing the procedure in centers with and without prior experience in EDP ablation (76% (CI95% 62-90) vs. 69% (CI95% 59-80); P=0.269).

Conclusion

In a large prospective cohort of patients with post-MI VT, substrate ablation based on EDP elimination resulted in excellent long-term outcome. Of importance, procedural outcomes were similar in centers with or without experience in EDP ablation, indicating that this approach can be easily reproduced by operators previously not familiar with the technique.

Initial experience with a novel pulsed field ablation catheter for ablation of atrial fibrillation: procedural findings and acute safety

Funding Acknowledgements

Type of funding sources: None.

Background

Currently employed catheters for treatment of symptomatic atrial fibrillation (AF) leverage thermal energy to ablate the myocardium. Despite excellent acute success rates, the non-selective nature of thermal injury has been associated with frequent AF recurrences and complications such as pulmonary vein stenosis and thermal damage to adjacent structures. Recently, a novel, non-thermal ablative modality has been introduced for the treatment of AF: pulsed field ablation (PFA). The selective nature of PFA translates in the ability to perform full transmural lesions whilst sparing adjacent tissues and structures, making PFA an attractive solution to limitations faced with thermal energy sources. Although several pre-clinical studies investigated the safety and feasibility of PFA, limited reports have been published so far describing the clinical application of this novel catheter technology.

Purpose

In this study we present our initial experience with a pulsed field ablation catheter and describe procedural findings and acute safety of the first 68 patients treated at our center.

Methods

We investigated the first 68 patients treated for symptomatic AF at our center using pulsed field ablation between July 2021 and January 2022. Procedural findings at the time of ablation are presented. Procedure-related complications are reported. Qualitative analysis of electrograms and electrophysiological maps before and after ablation are also provided. Lastly, learning curves of operators who performed more than 10 procedures are described.

Results

Mean age of patients was 63.1±9.2 years, and most were men (57.4%). Most patients suffered from paroxysmal AF (79.4%). The median CHA2DS2-VASc score was 2.0 (1.0; 3.0) and mean left-atrium (LA) volume index was 33.0±8.3 ml/m2. All procedures were performed using conscious sedation. In 63/68 patients ablation of the PVI was performed and in 5/68 patients additional ablation of the left atrial posterior wall was performed. 3D electroanatomic mapping was performed during 10/68 procedures which lasted on average 107.3±15.5 min. Procedures where no mapping was performed lasted on average 48.5±20.7 min. Mean LA time was 39.9±19.0 min. Mean number of applications per pulmonary vein (PV) were 8.6±1.1. In all patients (100%) PVs were confirmed to be isolated. Four different operators performed the ablations: operator 1 performed 25/58 procedures (36.8%), operator 2 28/58 (41.2%), operator 3 9/58 (13.2%), and operator 4 6/58 (8.8%). The learning curves of both operator 1 and operator 2 showed negligible variation of performance over time (R2: Operator 1 = 0.181; Operator 2 = 0.078). The only complications reported were two cases of bleeding at the percutaneous access site of the femoral vein.

Conclusions

Our initial experience with a PFA catheter in 68 patients shows that PFA is a safe, quick, easy-to-learn, and effective ablation technique for the treatment of symptomatic AF.

Heart rate increase and inappropriate sinus tachycardia after cryoballoon pulmonary vein isolation for atrial fibrillation

BACKGROUND

Cryoballoon pulmonary vein isolation (PVI) is a common therapy for atrial fibrillation (AF). While moderately increased sinus rhythm heart rate (HR) after PVI has been observed, inappropriate sinus tachycardia (IST) is a rare phenomenon. We aimed to investigate the prevalence and natural history of an abnormal sinus HR response after cryoballoon PVI.

METHODS

We included 169/646 (26.2%) patients with AF undergoing PVI with available Holter recordings before and 3, 6 and 12 months after the procedure. Patients with AF on Holter monitoring were excluded. Mean HR increase ≥ 20 bpm or an IST-like pattern (mean HR > 90 bpm or > 80 bpm when beta-blocking agents were used) following PVI was categorised as abnormal sinus HR response.

RESULTS

Following PVI, mean HR ± standard deviation increased in the entire group from 63.5 ± 8.4 to 69.1 ± 9.9 bpm at 3 months (p < 0.001), and to 71.9 ± 9.4 bpm at 6 months (p < 0.001). At 12 months, mean HR was 71.2 ± 10.1 bpm (p < 0.001). Only 7/169 patients (4.1%) met criteria for abnormal sinus HR response: mean HR was 61.9 ± 10.6 bpm (pre-ablation), 84.6 ± 9.8 bpm (3 months), 80.1 ± 6.5 bpm (6 months) and 76.3 ± 10.1 bpm (12 months). Even at 12 months, mean HR was significantly different from that pre-ablation in this group (p = 0.033). However, in patients meeting IST-like pattern criteria, mean HR at 12 months was no longer significantly different from that pre-ablation.

CONCLUSION

Few patients had an abnormal sinus HR response after PVI. Peak HR was observed 3 months after PVI, but HR was still significantly increased 12 months post-ablation compared with pre-ablation. An IST-like pattern was rarely observed. In these patients, HR decreased to pre-ablation values within a year.

Gradually increasing impedance in patients with pacemakers and implantable defibrillators: a watchful waiting strategy

Funding Acknowledgements

Type of funding sources: None.

Introduction

Pacing impedance measurements are important in the surveillance of pacemaker and implantable cardioverter/defibrillator (ICD) devices. Whereas sudden changes in impedances can reflect lead fracture or isolation defects, gradually increasing impedances are thought to occur because of calcifications at the endomyocardial interface. In many cases, these leads are replaced prophylactically but this has not been studied systematically.

Purpose

We aimed to identify the outcome of right ventricular (RV) electrodes with high impedances that were left active in this single center study.

Methods

All patients in the electronic patient database were screened for impedances &gt;1200Ohms. 41,201 individual recordings led to 207 individual patients. 161 patients were excluded from the analysis due to sudden impedance increase, temporarily high impedances or wrong entry. Of the remaining 46 patients, baseline characteristics as well as pacing impedance, sensing values, pacing thresholds, and shock impedance in case of ICDs were recorded.

Results

There were 17 pacemaker and 29 ICD patients, 68 ± 15 years old, 70% were male. Glomerular filtration rate at baseline was 81 ± 22 ml/min/1.73m2. Baseline RV impedance was 597 ± 123Ohms. During follow-up impedances increased to 1875 ± 682Ohms (p &lt; 0,001). Pacing thresholds increased from 0,6 ± 0,4V to 3,0 ± 1,9V (p &lt; 0,001). Sensing remained stable. The median time from implant to  impedance rise &gt;1000Ohms was 5,5 (3,4-7)years and median follow-up thereafter 2,4 years (1,2-4,2). During follow-up, no intervention was performed for 33 leads (72%). No events occurred. 13 leads (28%) were replaced , 9 prophylactically (mostly because of ICD advisory leads), 3 because of high pacing thresholds and high percentage pacing and one lead because of noise oversensing, probably unrelated as it occurred 7 years after impedance increase.

Conclusions

A watchful waiting strategy appears to be a safe option for patients with ICDs and pacemakers with low percentage pacing. As impedance increase cannot be used for surveillance for imminent lead fracture, other means such as short interval counts and non-sustained oversensing have to be employed and should be combined with remote monitoring.

Complex clinical scenarios with the use of direct oral anticoagulants in patients with atrial fibrillation: a multidisciplinary expert advisory board

The risk of developing atrial fibrillation (AF) and the risk of stroke both increase with advancing age. As such, many individuals have, or will develop, an indication for oral anticoagulation to reduce the risk of stroke. Currently, a large number of anticoagulants are available, including vitamin K antagonists, direct thrombin or factor Xa inhibitors (the last two also referred to as direct oral anticoagulants or DOACs), and different dosages are available. Of the DOACs, rivaroxaban can be obtained in the most different doses: 2.5 mg, 5 mg, 15 mg and 20 mg. Many patients develop co-morbidities and/or undergo procedures that may require the temporary combination of anticoagulation with antiplatelet therapy. In daily practice, clinicians encounter complex scenarios that are not always described in the treatment guidelines, and clear recommendations are lacking. Here, we report the outcomes of a multidisciplinary advisory board meeting, held in Utrecht (The Netherlands) on 3 June 2019, on decision making in complex clinical situations regarding the use of DOACs. The advisory board consisted of Dutch cardiovascular specialists: (interventional) cardiologist, internist, neurologist, vascular surgeon and general practitioners invited according to personal title and specific field of expertise.

Antibiotic use during pregnancy and asthma in preschool children: the influence of confounding

BACKGROUND

A recent study suggested that early-life intestinal microbiota may play an important role in the development of childhood asthma, indicating that antibiotics taken during early life or in late pregnancy may be associated with childhood asthma.

OBJECTIVE

This study aims to assess the association between prenatal antibiotic use and asthma in preschool children using data from the prescription database IADB.nl. To assess the influence of potential confounding, we conducted both a case-sibling and a case-control study and compared the results.

METHODS

We conducted a case-sibling study in which 1228 children with asthma were compared to 1228 siblings without asthma, using data from the prescription database IADB.nl. In addition, a case-control study was conducted. Asthma in preschool children was defined as ≥ 3 prescriptions for anti-asthma medication within a year before the fifth birthday. Conditional logistic regression was used to estimate crude and adjusted odds ratios (aORs).

RESULTS

In both the case-sibling and case-control analysis, the use of antibiotics in the third trimester of pregnancy was associated with an increased risk of asthma in preschool children (aOR 1.37; 95% CI 1.02-1.83 and aOR 1.40; 95% CI 1.15-1.47). Time-trend analyses showed that results were not influenced by a time trend in antibiotic exposure. A significant association between exposure to antibiotics in any trimester of pregnancy and the development of asthma in preschool children was observed in the case-control analysis only (aOR 1.46; 95% CI 1.34-1.59).

CONCLUSION

Antibiotic use in the third trimester of pregnancy was associated with a small increased risk of asthma in preschool children. This association was robust to time-invariant confounding or exposure time trends, further supporting the important role for early-life intestinal microbiota in the development of childhood asthma.

Identification of Dutch children diagnosed with atopic diseases using prescription data: a validation study

Purpose

The aim of this study is to validate medication proxies for the identification of children diagnosed with atopic disorders that can be applied in various types of epidemiological research.

Methods

Records of 7439 children, aged between 0 and 10 years, in the period 2001 until 2010, were retrieved from the Registration Network Groningen database, a general practitioners database in the north-eastern part of the Netherlands. The sensitivity and positive predictive value (PPV) of 22 medication proxies for the identification of children diagnosed with atopic disorders (asthma, atopic dermatitis, and allergic rhinitis) were computed using the registered diagnoses as gold standards. In addition, different capture periods (1 year, half year, and length of study period) for the detection of prescriptions were tested for all the medication proxies.

Results

The highest PPV (0.84, 95 % CI 0.81–0.87) in combination with a sufficient sensitivity value (0.54, 95 % CI 0.50–0.57) for the identification of children diagnosed with asthma was yielded for the medication proxy, ≥2 prescriptions for anti-asthma medication within 1 year, including 1 inhaled steroid. PPV and sensitivity were even higher in the age group 6–10 years. The proxies designed for the identification of children diagnosed with atopic dermatitis and allergic rhinitis yielded only high PPVs (≥0.75) in combination with low sensitivity values (≤0.22). Altering the capture period for the detection of prescriptions to half a year or the length of the study period only affected sensitivity values.

Conclusion

Children diagnosed with asthma can be identified reliably with a range of medication proxies. The use of prescription data for the identification of children diagnosed with atopic dermatitis and allergic rhinitis is questionable.

Prenatal exposure to acid-suppressive drugs and the risk of allergic diseases in the offspring: a cohort study

BACKGROUND

Recent studies reported increased risks for the development of asthma in children after prenatal exposure to acid-suppressive drugs. As a result of common pathogenesis, associations could also be present for other allergic diseases.

METHODS

Using the prescription database IADB.nl, we conducted a cohort study amongst 33 536 children in the Netherlands, with a maximum follow-up of 8 years. Maternal exposure was defined as ≥1 dispensed prescription for proton pump inhibitors (PPIs) and/or Histamine 2-antagonists (H2As) during pregnancy. Children were considered to have a drug-treated allergic disease if they received either ≥2 prescriptions for dermal (atopic dermatitis), inhaled (asthma) or nasal (allergic rhinitis) steroids within a 12-month period. Clustered Cox proportional hazard regression was used to estimate crude and adjusted hazard ratios (aHR) with 95% confidence intervals (95% CI).

RESULTS

The aHR for the development of any allergic disease was 1.37 (95% CI: 1.14-1.66) for children exposed to PPIs or H2As. Prenatal exposure to PPIs and/or H2As was associated with atopic dermatitis, asthma and allergic rhinitis with aHRs of 1.32 (95% CI 1.06-1.64), 1.57 (95% CI 1.20-2.05) and 2.40 (95% CI 1.42-4.04), respectively. The aHR for the development of two or more (aHR 2.13 95% CI: 1.43-3.19) and three allergic diseases (aHR 5.18 95% CI: 2.16-12.42) were even more elevated after prenatal exposure to PPIs or H2As.

CONCLUSION

Prenatal exposure to PPIs and H2As appeared associated with an increased risk for the development of atopic dermatitis, asthma and allergic rhinitis in the offspring, especially with the development of multiple allergic diseases. Because our study has limitations inherent to observational studies, prospective studies are now warranted to confirm our findings.

Simultaneous increase of Cryptosporidium infections in the Netherlands, the United Kingdom and Germany in late summer season, 2012

Binary file ES_Abstracts_Final_ECDC.txt matches

Simultaneous increase of Cryptosporidium infections in the Netherlands, the United Kingdom and Germany in late summer season, 2012

Starting August 2012, an increase in Cryptosporidium infections was reported in the Netherlands, the United Kingdom and Germany. It represented a 1.8 to 4.9-fold increase compared to previous years. Most samples were C. hominis IbA10G2. A case–control study was performed in the Netherlands but did not identify an endemic source. A case–case study in the north of England found travel abroad to be the most common risk factor.

Xpert MTB/RIF®, a novel automated polymerase chain reaction-based tool for the diagnosis of tuberculosis

There is an urgent need for new point of care tests for tuberculosis (TB). Xpert MTB/RIF® is a real-time polymerase chain reaction-based system that detects Mycobacterium tuberculosis DNA and rifampicin (RMP) resistance modulating mutations directly from clinical samples in 2 h. The sensitivity for detecting M. tuberculosis in culture-positive samples was 93.8% (60/64) and exceeded smear microscopy (40/64, 62.5%). The specificity for detecting M. tuberculosis was 92.0% (23/25) and for RMP resistance it was 100% (8/8). The test is simple to conduct and requires basic sputum handling facilities only. These characteristics render it a promising close-to-patient test for TB in various settings.

Cerebrovascular accidents in adult patients with congenital heart disease

OBJECTIVE

To investigate the prevalence and characteristics of cerebrovascular accidents (CVA) in a large population of adults with congenital heart disease (CHD).

METHODS AND RESULTS

In a retrospective analysis of aggregated European and Canadian databases a total population of 23 153 patients with CHD was followed up to the age of 16-91 years (mean 36.4 years). Among them, 458 patients (2.0%) had one or more CVA, with an estimated event rate of 0.05% per patient-year. Permanent neurological sequelae were noted in 116 patients (25.3%). The prevalence of CVA in selected diagnostic categories was as follows: open atrial septal defect 93/2351 (4.0%); closed atrial or ventricular septal defect 57/4035 (1.4%); corrected tetralogy of Fallot 52/2196 (2.4%); Eisenmenger physiology 24/467 (5.1%); other cyanotic 50/215 (23.3%); mechanical prostheses (29/882 (3.3%). Associated conditions in patients with CVA were absence of sinus rhythm (25%), transvenous pacemakers (7%), endocarditis (2%), cardiac surgery (11%) and catheter intervention (2%), but with the exception of absent sinus rhythm these were not significantly more prevalent in patients with CVA.

CONCLUSION

CVA are a major contributor to morbidity in this young population despite absence of classical cardiovascular risk factors. Although the prevalence of CVA in patients with CHD appears low, it is 10-100 times higher than expected in control populations of comparable age. Residua occur in a strong minority of patients. The subjects at highest risk are those patients with CHD with cyanotic lesions, in whom the prevalence is over 10-fold above the average.

Non-specific interactions are sufficient to explain the position of heterochromatic chromocenters and nucleoli in interphase nuclei

The organization of the eukaryote nucleus into functional compartments arises by self-organization both through specific protein-protein and protein-DNA interactions and non-specific interactions that lead to entropic effects, such as e.g. depletion attraction. While many specific interactions have so far been demonstrated, the contributions of non-specific interactions are still unclear. We used coarse-grained molecular dynamics simulations of previously published models for Arabidopsis thaliana chromatin organization to show that non-specific interactions can explain the in vivo localization of nucleoli and chromocenters. Also, we quantitatively demonstrate that chromatin looping contributes to the formation of chromosome territories. Our results are consistent with the previously published Rosette model for Arabidopsis chromatin organization and suggest that chromocenter-associated loops play a role in suppressing chromocenter clustering.

Molecular and epidemiological investigations of cryptosporidiosis in Cuban children

Molecular and epidemiological studies of Cryptosporidium infections amongst 28 Cuban children (aged 2-8 years) with diarrhoea are described. As few of the younger infected children but most of the older infected children had been breastfed, short-term protection from maternal antibodies passed to infants during breastfeeding may result in a lack of cryptosporidial infection in infancy. This protection of breastfeeding children may, however, result in such children developing less anti-Cryptosporidium immunity of their own (than their bottle-fed counterparts), so that, by school age, the children who had been breastfed are those most likely to be found infected. In the present study, in contrast with the observations made during a previous study of cryptosporidiosis in Cuban children, vomiting was rare (7%) whereas abdominal pain was common (57%). These differences in expression of symptoms between studies may be age-related. As seen in other studies from similar countries, including those of the Caribbean and Latin America, C. hominis was found to predominate, the results of the successful molecular analyses revealing 10 C. hominis infections but no C. parvum. Subgenotyping (at the gp60 locus) indicated that the C. hominis infections included a wide range of subtypes, with isolates from three subtype families (Ia, Ib and Id) being detected.

Giardia infections in Cuban children: the genotypes circulating in a rural population

Stool samples containing Giardia duodenalis cysts were collected from 95 primary-school children in central Cuba, and preserved by storing at -20 degrees C in 70% ethanol. Clinical data were collected for each child. Although 57% of the children were asymptomatic, the remaining 43% each reported between one and three symptoms. Following cyst quantification and isolation, molecular analyses were attempted on all cyst isolates, with the focus on the parasite's beta-giardin and glutamate-dehydrogenase (gdh) genes. Unfortunately, the cyst-preservation procedure appeared to have a deleterious effect on the cysts, since genotyping data could only be obtained for 20 of the 95 isolates. These data indicated, however, an approximately equal distribution between assemblage A (nine isolates) and assemblage B (11 isolates). Children found to be excreting relatively large numbers of cysts were more likely to be symptomatic than children who were excreting fewer cysts, and children with Giardia isolates from assemblage B were more likely to have symptomatic infections than children with isolates from assemblage A. Although considerable sequence variability was seen in the assemblage-B isolates, the assemblage-A isolates were relatively genetically homogeneous. This is the first publication from the Caribbean in which the Giardia genotypes circulating within the population have been identified, the first from the Americas providing information on associations between clinical presentation and the assemblage of the infecting Giardia, and the first to indicate that levels of cyst excretion may have clinical significance.

Aetiology and presentation of HIV/AIDS-associated pulmonary infections in patients presenting for bronchoscopy at a referral hospital in northern Tanzania

OBJECTIVES

To determine the aetiological agents of pulmonary infections in HIV-infected Tanzanians and to correlate the causative agents with clinical, radiographic features, and mortality.

DESIGN

A prospective study.

SETTING

Kilimanjaro Christian Medical Centre (KCMC), Tanzania.

SUBJECTS

Bronchoalveolar lavage fluid (BAL) were obtained from 120 HIV infected patients with pulmonary infections. BAL for causative agents was analysed and correlated with clinical and radiographic features, and one-month outcome.

RESULTS

Causative agents were identified in 71 (59.2%) patients and in 16 of these patients, multiple agents were found. Common bacteria were identified in 35 (29.2%) patients, Mycobacterium tuberculosis in 28 (23.3%), Human Herpes Virus 8 (HHV8) in 12 (10%), Pneumocystis jiroveci in nine (7.5%) and fungi in five (4.2%) patients. Median CD4 T cell count of the patients with identified causes was 47 cells/microl (IQR 14-91) and in the 49 patients with undetermined aetiology was 100 cells/ microl (IQR 36-188; p = 0.01). Micronodular chest radiographic lesions were associated with presence of M. tuberculosis (p = 0.002). The one-month mortality was 20 (16.7%). The highest mortality was associated with HHV8 (41.7%) and M. tuberculosis (32.1%). Mortality in patients with undetermined aetiology was 11.3%. No death occurred in patients with PCP.

CONCLUSION

In this population of severely immunosuppressed HIV-infected patients with pulmonary infection a variety of causative agents was identified. Micronodular radiographic lesions were indicative of TB. High mortality was associated with M. tuberculosis or HHV8. No death occurred in patients with P. jiroveci infection.

Sphere size distributions from finite thickness sections: a forward approach employing a genetic algorithm

We formulate, implement and test a robust method of determining sphere size distributions from finite thickness planar sections. The method uses a forward approach in which populations of proposed distributions are tested against the input data and refined using a genetic algorithm. This method is then applied to a real-world data set concerning endo- and exocytotic vesicles in the apical region of tip growing pollen tubes of Arabidopsis thaliana.

Rapid drug susceptibility testing of mycobacteria by culture on a highly porous ceramic support

BACKGROUND

Phenotypic, culture-based methods for drug susceptibility testing (DST) of Mycobacterium tuberculosis are relatively simple and may be particularly appropriate for resource-limited settings where tuberculosis (TB) is most prevalent. However, these methods can be slow and generate significant amounts of infectious waste. Low-cost digital imaging and a unique porous ceramic support for cell culture (Anopore) may offer opportunities to improve this situation.

OBJECTIVE

To test a rapid DST method based on fluorescence microscopy of mycobacteria grown for a few generations on Anopore.

DESIGN

Mycobacteria were cultured with and without drugs, and the resulting microcolonies were heat-killed and stained with the fluorogenic dye Syto16. Microscopy, image-capture with a charge-coupled device camera and digital processing were used to quantify the inhibition of growth by drugs. Rapid DST for rifampicin and isoniazid was performed for clinical isolates.

RESULTS

Mycobacteria could be cultured, killed, stained and imaged on Anopore. For DST, the Anopore method gave an accurate result in 3 days.

CONCLUSION

This is an unprecedented speed for culture-based DST for this group of organisms and results in minimal infectious waste (<20,000 colony forming units). Analysis of mycobacteria by fluorescence and electron microscopy on Anopore also opens up research possibilities.

Prevalence, characterisation and clinical profiles of Shiga toxin-producing Escherichia coli in The Netherlands

Detection of Shiga toxin-producing Escherichia coli (STEC) in The Netherlands is traditionally limited to serogroup O157. To assess the relative importance of STEC, including non-O157 serogroups, stool samples submitted nationwide for investigation of enteric pathogens or diarrhoea were screened with real-time PCR for the presence of the Shiga toxin genes. Patients were selected if their stool contained blood upon macroscopic examination, if they had a history of bloody diarrhoea, were diagnosed with haemolytic uraemic syndrome, or were aged <6 years (irrespective of the bloody aspect of the stool). PCR-positive stools were forwarded to a central laboratory for STEC isolation and typing. In total, 4069 stools were examined, with 68 (1.7%) positive PCR results. The highest prevalence was for stools containing macroscopic blood (3.5%), followed by stools from patients with a history of bloody diarrhoea (2.4%). Among young children, the prevalence (1.0%) was not significantly higher than among random, non-bloody, stool samples from diarrhoeal patients (1.4%). STEC strains were isolated from 25 (38%) PCR-positive stools. Eleven O-serogroups were detected, including five STEC O157 strains. As serogroup O157 represented only 20% of the STEC isolates, laboratories should be encouraged to use techniques enabling them to detect non-O157 serogroups, in parallel with culture, for isolation and subsequent characterisation of STEC strains for public health surveillance and detection of outbreaks.

Plasmodium falciparum transmission blocking immunity under conditions of low and high endemicity in Cameroon

Transmission blocking immunity (TBI) was studied in relation to age, gametocyte density and transmission intensity. subjects with high gametocytaemias were selected in a hypo-endemic urban district and a hyper-endemic rural area in South Cameroon. TBI was determined in blood from gametocyte carriers in a bioassay (Direct Membrane Feeding Assay), with either autologous plasma (OWN) or control serum (AB). Mosquito infection rates (IR) were compared. infection rates correlated positively with gametocyte and oocyst densities. Three TBI indicators were analysed: the proportion of transmission reducers (IRAB > IROWN, P < 0.01), the mean intensity of TBI (IRAB - IROWN), and the contribution of TBI to total inhibition [(IRAB-IROWN)/(100-IROWN)]. we could not discriminate between areas with regard to either the proportion of transmission reducers (urban 15% and rural 29%) or the mean levels of TBI (urban 10% and rural 9%), or contribution of TBI to total inhibition (urban 10% and rural 13%). there was no relationship between TBI indicators and age, but a trend of increasing values was observed with rising gametocytaemia, which was considered as a confusing factor. a multivariable analysis showed that the probability of being a reducer was 4.6 fold higher in the rural area than in the urban district.

Origin of Plasmodium falciparum malaria is traced by mitochondrial DNA

The origin and geographical spread of Plasmodium falciparum is here determined by analysis of mitochondrial DNA sequence polymorphism and divergence from its most closely related species P. reichenowi (a rare parasite of chimpanzees). The complete 6 kb mitochondrial genome was sequenced from the single known isolate of P. reichenowi and from four different cultured isolates of P. falciparum, and aligned with the two previously derived P. falciparum sequences. The extremely low synonymous nucleotide polymorphism in P. falciparum (pi=0.0004) contrasts with the divergence at such sites between the two species (kappa=0.1201), and supports a hypothesis that P. falciparum has recently emerged from a single ancestral population. To survey the geographical distribution of mitochondrial haplotypes in P. falciparum, 104 isolates from several endemic areas were typed for each of the identified single nucleotide polymorphisms. The haplotypes show a radiation out of Africa, with unique types in Southeast Asia and South America being related to African types by single nucleotide changes. This indicates that P. falciparum originated in Africa and colonised Southeast Asia and South America separately.

Hard-sphere solids near close packing: testing theories for crystallization

The freezing transition of hard spheres has been well described by various versions of density-functional theory (DFT). These theories should possess the close-packed crystal as a special limit, which represents an extreme testing ground for the quality of such liquid-state based theories. We therefore study the predictions of DFT for the structure and thermodynamics of the hard-sphere crystal in this limit. We examine the Ramakrishnan-Yussouff (RY) approximation and two variants of the fundamental-measure theory (FMT) developed by Rosenfeld and co-workers. We allow for general shapes of the density peaks, going beyond the common Gaussian approximation. In all cases we find that upon approaching close packing, the peak width vanishes proportionally to the free distance a between the particles and the free energy depends logarithmically on a. However, different peak shapes and next-to-leading contributions to the free energy result from the different approximate functionals. For the RY theory, within the Gaussian approximation, we establish that the crystalline solutions form a closed loop with a stable and an unstable branch both connected to the close-packing point at a=0, consistent with the absence of a liquid-solid spinodal. That version of FMT that has previously been applied to freezing, predicts asymptotically steplike density profiles confined to the cells of self-consistent cell theory. But a recently suggested improved version which employs tensor weighted densities yields wider and almost Gaussian peaks that are shown to be in very good agreement with computer simulations.

Computer-controlled flow resistance

A computer-controlled flow resistance (CCR), to be used in a computer-controlled lung model, is presented. Flow is forced through a slit between a cylinder and a sleeve around the cylinder. The resulting flow resistance depends on the width, circumferences and the variable length of the slit. The variation in the length is computer-controlled by the position of the sleeve with respect to the cylinder. The total flow resistance also depends on inlet and outlet resistance at both sides of the slit and on flow. The dependence on flow is primarily due to the shape of the inlet of the slit. The resistance of the slit itself is almost independent of flow. The resistance is calculated during a calibration phase at different positions of the sleeve, for flow values from 0.05 to 1.0 litre.s-1 (inflow) and from -0.05 to -1.0 litre.s-1 (outflow). To simulate a required resistance pattern, as, for instance, will occur during breathing, at each moment the set position of the sleeve is calculated by means of an interpolation from the relationship between flow resistance and position of the sleeve. The internal diameter of the sleeve is fixed. To tune the resistance range for a specific simulation, the cylinder is changed for one with different diameter, changing the width of the slit.

Plasmodium falciparum: membrane feeding assays and competition ELISAs for the measurement of transmission reduction in sera from Cameroon

The effect of natural malaria transmission-blocking factors in the blood of Plasmodium falciparum gametocyte carriers was assessed in two types of functional bioassays. In the direct membrane feeding assay (DMFA), a comparison is made between the infectivity of gametocytes from a naturally infected gametocyte carrier in the presence of autologous plasma and the infectivity in the presence of replacement plasma from nonimmune donors. In the standard membrane feeder assay (SMFA), cultured NF54 gametocytes are used to measure the capacity of endemic sera to block transmission. In the DMFA, 18 out of 48 sera (37.5%) from Cameroonian gametocyte carriers reduced transmission significantly, while in the SMFA 22 out of 48 sera (45.8%) produced transmission reduction. There was a positive correlation between both assays (r + 0.41, P < 0.05). Antibodies against epitopes of transmission-blocking target antigens Pfs48/45 and Pfs230 were measured in competition ELISAs and compared with the results of DMFA and SMFA. Serological reactivity in competition ELISAs against three epitopes of Pfs48/45 was significantly higher in the group of transmission-reducing sera in both the DMFA and the SMFA, especially for epitope III. No significant difference was found for Pfs230 antibodies (epitope I). Sensitivity of the serological assays was approximately 60%, with a specificity of around 70%. Serological tests cannot replace the functional bioassay in field situations as yet, but can contribute in the selection of sera for SMFA evaluation.

Why all crystals need not be bcc: symmetry breaking at the liquid-solid transition revisited

Alexander and McTague [Phys.Rev. Lett. 41, 702 (1978)] argued that if there is a spinodal point associated with the liquid-solid transition in a fluid of spherically symmetric particles, the bcc phase will be uniquely favored as the only accessible symmetry breaking structure that forms a regular three-dimensional lattice. By reconsidering their analysis in the framework of density-functional theory, we show that at a liquid-solid spinodal in fact many other solid stuctures also are simultaneously accessible, among them the fcc structure. Nevertheless, the bcc structure is still shown to be special, as, independent of the details of the interaction, the free energy of the unstable bcc phase close to the spinodal is always lower than that of the other solidlike structures. We illustrate our general results by explicit calculations on a toy model, the "Onsager solid." This simple model also indicates that the ultimately stable crystal phase, which, as usual for sufficiently steep repulsive forces, turns out to be fcc, is dictated by properties of the free energy that cannot be obtained perturbatively starting from the spinodal point.

DNA recognition properties of the N-terminal DNA binding domain within the large subunit of replication factor C

Replication Factor C (RFC) is a five-subunit protein complex required for eukaryotic DNA replication and repair. The large subunit within this complex contains a C-terminal DNA binding domain which provides specificity for PCNA loading at a primer-template and a second, N-terminal DNA binding domain of unknown function. We isolated the N-terminal DNA binding domain from Drosophila melanogaster and defined the region within this polypeptide required for DNA binding. The DNA determinants most efficiently recognized by both the Drosophila minimal DNA binding domain and the N-terminal half of the human large subunit consist of a double-stranded DNA containing a recessed 5' phosphate. DNA containing a recessed 5' phosphate was preferred 5-fold over hairpined DNA containing a recessed 3' hydroxyl. Combined with existing data, these DNA binding properties suggest a role for the N-terminal DNA binding domain in the recognition of phosphorylated DNA ends.