Surrogate Adiposity Markers and Mortality

Importance

Body mass index (BMI) is an easily obtained adiposity surrogate. However, there is variability in body composition and adipose tissue distribution between individuals with the same BMI, and there is controversy regarding the BMI associated with the lowest mortality risk.

Objective

To evaluate which of BMI, fat mass index (FMI), and waist-to-hip (WHR) has the strongest and most consistent association with mortality.

Design, Setting, and Participant

This cohort study used incident deaths from the UK Biobank (UKB; 2006-2022), which includes data from 22 clinical assessment centers across the United Kingdom. UKB British participants of British White ancestry (N = 387 672) were partitioned into a discovery cohort (n = 337 078) and validation cohort (n = 50 594), with the latter consisting of 25 297 deaths and 25 297 controls. The discovery cohort was used to derive genetically determined adiposity measures while the validation cohort was used for analyses. Exposure-outcome associations were analyzed through observational and mendelian randomization (MR) analyses.

Exposures

BMI, FMI, and WHR.

Main Outcomes and Measures

All-cause and cause-specific (cancer, cardiovascular disease [CVD], respiratory disease, or other causes) mortality.

Results

There were 387 672 and 50 594 participants in our observational (mean [SD] age, 56.9 [8.0] years; 177 340 [45.9%] male, 210 332 [54.2%], female), and MR (mean [SD] age, 61.6 [6.2] years; 30 031 [59.3%] male, 20 563 [40.6%], female) analyses, respectively. Associations between measured BMI and FMI with all-cause mortality were J-shaped, whereas the association of WHR with all-cause mortality was linear using the hazard ratio (HR) scale (HR per SD increase of WHR, 1.41 [95% CI, 1.38-1.43]). Genetically determined WHR had a stronger association with all-cause mortality than BMI (odds ratio [OR] per SD increase of WHR, 1.51 [95% CI, 1.32-1.72]; OR per SD increase of BMI, 1.29 [95% CI, 1.20-1.38]; P for heterogeneity = .02). This association was stronger in male than female participants (OR, 1.89 [95% CI, 1.54-2.32]; P for heterogeneity = .01). Unlike BMI or FMI, the genetically determined WHR-all-cause mortality association was consistent irrespective of observed BMI.

Conclusions and Relevance

In this cohort study, WHR had the strongest and most consistent association with mortality irrespective of BMI. Clinical recommendations should consider focusing on adiposity distribution compared with mass.

A versatile, fast and unbiased method for estimation of gene-by-environment interaction effects on biobank-scale datasets

Identification of gene-by-environment interactions (GxE) is crucial to understand the interplay of environmental effects on complex traits. However, current methods evaluating GxE on biobank-scale datasets have limitations. We introduce MonsterLM, a multiple linear regression method that does not rely on model specification and provides unbiased estimates of variance explained by GxE. We demonstrate robustness of MonsterLM through comprehensive genome-wide simulations using real genetic data from 325,989 individuals. We estimate GxE using waist-to-hip-ratio, smoking, and exercise as the environmental variables on 13 outcomes (N = 297,529-325,989) in the UK Biobank. GxE variance is significant for 8 environment-outcome pairs, ranging from 0.009 - 0.071. The majority of GxE variance involves SNPs without strong marginal or interaction associations. We observe modest improvements in polygenic score prediction when incorporating GxE. Our results imply a significant contribution of GxE to complex trait variance and we show MonsterLM to be well-purposed to handle this with biobank-scale data.

Mitochondrial DNA Copy Number as a Marker and Mediator of Stroke Prognosis: Observational and Mendelian Randomization Analyses

BACKGROUND AND OBJECTIVES

Low buffy coat mitochondrial DNA copy number (mtDNA-CN) is associated with incident risk of stroke and poststroke mortality; however, its prognostic utility has not been extensively explored. Our goal was to investigate whether low buffy coat mtDNA-CN is a marker and causal determinant of poststroke outcomes using epidemiologic and genetic studies.

METHODS

First, we performed association testing between baseline buffy coat mtDNA-CN measurements and 1-month poststroke outcomes in 3,498 cases of acute, first stroke from 25 countries from the international, multicenter case-control study Importance of Conventional and Emerging Risk Factors of Stroke in Different Regions and Ethnic Groups of the World (INTERSTROKE). Then, we performed 2-sample mendelian randomization analyses to evaluate potential causative effects of low mtDNA-CN on 3-month modified Rankin Scale (mRS) score. Genetic variants associated with mtDNA-CN levels were derived from the UK Biobank study (N = 383,476), and corresponding effects on 3-month mRS score were ascertained from the Genetics of Ischemic Stroke Functional Outcome (GISCOME; N = 6,021) study.

RESULTS

A 1-SD lower mtDNA-CN at baseline was associated with stroke severity (baseline mRS score: odds ratio [OR] 1.27, 95% confidence interval [CI] 1.19-1.36; p = 4.7 × 10^-12). Independently of baseline stroke severity, lower mtDNA-CN was associated with increased odds of greater 1-month disability (ordinal mRS score: OR 1.16, 95% CI 1.08-1.24; p = 4.4 × 10^-5), poor functional outcome status (mRS score 3-6 vs 0-2: OR 1.21, 95% CI 1.08-1.34; p = 6.9 × 10^-4), and mortality (OR 1.35, 95% CI 1.14-1.59; p = 3.9 × 10^-4). Subgroup analyses demonstrated consistent effects across stroke type, sex, age, country income level, and education level. In addition, mtDNA-CN significantly improved reclassification of poor functional outcome status (net reclassification index [NRI] score 0.16, 95% CI 0.08-0.23; p = 3.6 × 10^-5) and mortality (NRI score 0.31, 95% CI 0.19-0.43; p = 1.7 × 10^-7) beyond known prognosticators. With the use of independent datasets, mendelian randomization revealed that a 1-SD decrease in genetically determined mtDNA-CN was associated with increased odds of greater 3-month disability quantified by ordinal mRS score (OR 2.35, 95% CI 1.13-4.90; p = 0.02) and poor functional outcome status (OR 2.68, 95% CI 1.05-6.86; p = 0.04).

DISCUSSION

Buffy coat mtDNA-CN is a novel and robust marker of poststroke prognosis that may also be a causal determinant of poststroke outcomes.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that low buffy coat mtDNA-CN (>1 SD) was associated with worse baseline severity and 1-month outcomes in patients with ischemic or hemorrhagic stroke.

GWAS and ExWAS of blood Mitochondrial DNA copy number identifies 71 loci and highlights a potential causal role in dementia

Background:

Mitochondrial DNA copy number (mtDNA-CN) is an accessible blood-based measurement believed to capture underlying mitochondrial (MT) function. The specific biological processes underpinning its regulation, and whether those processes are causative for disease, is an area of active investigation.

Methods:

We developed a novel method for array-based mtDNA-CN estimation suitable for biobank-scale studies, called ‘automatic mitochondrial copy (AutoMitoC).’ We applied AutoMitoC to 395,781 UKBiobank study participants and performed genome- and exome-wide association studies, identifying novel common and rare genetic determinants. Finally, we performed two-sample Mendelian randomization to assess whether genetically low mtDNA-CN influenced select MT phenotypes.

Results:

Overall, genetic analyses identified 71 loci for mtDNA-CN, which implicated several genes involved in rare mtDNA depletion disorders, deoxynucleoside triphosphate (dNTP) metabolism, and the MT central dogma. Rare variant analysis identified SAMHD1 mutation carriers as having higher mtDNA-CN (beta = 0.23 SDs; 95% CI, 0.18–0.29; p=2.6 × 10^-19), a potential therapeutic target for patients with mtDNA depletion disorders, but at increased risk of breast cancer (OR = 1.91; 95% CI, 1.52–2.40; p=2.7 × 10^-8). Finally, Mendelian randomization analyses suggest a causal effect of low mtDNA-CN on dementia risk (OR = 1.94 per 1 SD decrease in mtDNA-CN; 95% CI, 1.55–2.32; p=7.5 × 10^-4).

Conclusions:

Altogether, our genetic findings indicate that mtDNA-CN is a complex biomarker reflecting specific MT processes related to mtDNA regulation, and that these processes are causally related to human diseases.

Funding:

No funds supported this specific investigation. Awards and positions supporting authors include: Canadian Institutes of Health Research (CIHR) Frederick Banting and Charles Best Canada Graduate Scholarships Doctoral Award (MC, PM); CIHR Post-Doctoral Fellowship Award (RM); Wellcome Trust Grant number: 099313/B/12/A; Crasnow Travel Scholarship; Bongani Mayosi UCT-PHRI Scholarship 2019/2020 (TM); Wellcome Trust Health Research Board Irish Clinical Academic Training (ICAT) Programme Grant Number: 203930/B/16/Z (CJ); European Research Council COSIP Grant Number: 640580 (MO); E.J. Moran Campbell Internal Career Research Award (MP); CISCO Professorship in Integrated Health Systems and Canada Research Chair in Genetic and Molecular Epidemiology (GP)

Our cells are powered by small internal compartments known as mitochondria, which host several copies of their own ‘mitochondrial’ genome. Defects in these semi-autonomous structures are associated with a range of severe, and sometimes fatal conditions: easily checking the health of mitochondria through cheap, quick and non-invasive methods can therefore help to improve human health.

Measuring the concentration of mitochondrial DNA molecules in our blood cells can help to estimate the number of mitochondrial genome copies per cell, which in turn act as a proxy for the health of the compartment. In fact, having lower or higher concentration of mitochondrial DNA molecules is associated with diseases such as cancer, stroke, or cardiac conditions. However, current approaches to assess this biomarker are time and resource-intensive; they also do not work well across people with different ancestries, who have slightly different versions of mitochondrial genomes.

In response, Chong et al. developed a new method for estimating mitochondrial DNA concentration in blood samples. Called AutoMitoC, the automated pipeline is fast, easy to use, and can be used across ethnicities. Applying this method to nearly 400,000 individuals highlighted 71 genetic regions for which slight sequence differences were associated with changes in mitochondrial DNA concentration. Further investigation revealed that these regions contained genes that help to build, maintain, and organize mitochondrial DNA. In addition, the analyses yield preliminary evidence showing that lower concentration of mitochondrial DNA may be linked to a higher risk of dementia.

Overall, the work by Chong et al. demonstrates that AutoMitoC can be used to investigate how mitochondria are linked to health and disease in populations across the world, potentially paving the way for new therapeutic approaches.

Impact of analysis technique on our understanding of the natural history of labour: a simulation study

OBJECTIVE

To evaluate the discrepancy between historical and more recent descriptions of the first stage of labour by testing whether the statistical techniques used recently (repeated-measures polynomial and interval-censored regression) were appropriate for detection of periods of rapid acceleration of cervical dilatation as might occur at the time of transition from a latent to an active phase of labour.

DESIGN AND SETTING

A simulation study using regression techniques.

SAMPLE

We created a simulated data set for 500 000 labours with clearly defined latent and active phases using the parameters described by Friedman. Additionally, we created a data set comprising 500 000 labours with a progressively increasing rate of cervical dilatation.

METHODS

Repeated-measures polynomial regression was used to create summary labour curves based on simulated cervical examinations. Interval-censored regression was used to create centimetre-by-centimetre estimates of rates of cervical dilatation and their 95th centiles.

MAIN OUTCOME MEASURES

Labour summary curves and rates of cervical dilatation.

RESULTS

Repeated-measures polynomial regression did not detect the rapid acceleration in cervical dilatation (i.e. acceleration phase) and overestimated lengths of labour, especially at smaller cervical dilatations. There was a two-fold overestimation in the mean rate of cervical dilatation from 4 to 6 cm. Interval-censored regression overestimated median transit times, at 4- to 5-cm cervical dilatation or when cervical examinations occurred less frequently than 0.5- to 1.5-hourly.

CONCLUSION

Repeated-measures polynomial regression and interval-censored regression should not be routinely used to define labour progress because they do not accurately reflect the underlying data.

TWEETABLE ABSTRACT

Repeated-measures polynomial and interval-censored regression techniques are not appropriate to model first stage of labour.

PL3.6 Targeting GSK-3 activity promotes mitotic catastrophe via centrosome destabilisation and enhances the effect of radiotherapy in glioma models

BACKGROUND

Targeting kinases as regulators of cellular processes that drive cancer progression is a promising approach to improve patient outcome in GBM management. The glycogen synthase kinase 3 (GSK-3) plays a role in cancer progression and is known for its pro-proliferative activity in gliomas. The anti-proliferative and cytotoxic effects of the GSK-3 inhibitor AZD2858 were assessed in relevant in vitro and in vivo glioma models to confirm GSK-3 as a suitable target for improved single agent or combination treatments.

MATERIAL AND METHODS

The immortalised cell line U251 and the patient derived cell lines GBM1 and GBM4 were used in in vitro studies including MTT, clonogenic survival, live cell imaging, immunofluorescence microscopy and flow cytometry to assess the cytotoxic and anti-proliferative effects of AZD2858. Observed anti-proliferative effects were investigated by microarray technology for the identification of target genes with known roles in cell proliferation. Clinical relevance of targeting GSK-3 with the inhibitor either for single agent or combination treatment strategies was determined by subcutaneous and orthotopic in vivo modelling. Whole mount mass spectroscopy was used to confirm drug penetration in orthotopic tumour models.

RESULTS

AZD2858 was cytotoxic at low micromolar concentrations and at sub-micromolar concentrations (0.01 - 1.0 μM) induced mitotic defects in all cell lines examined. Prolonged mitosis, centrosome disruption/duplication and cytokinetic failure leading to cell death featured prominently among the cell lines concomitant with an observed S-phase arrest. No cytotoxic or anti-proliferative effect was observed in normal human astrocytes. Analysis of the RNA microarray screen of AZD2858 treated glioma cells revealed the dysregulation of mitosis-associated genes including ASPM and PRC1, encoding proteins with known roles in cytokinesis. The anti-proliferative and cytotoxic effect of AZD2858 was also confirmed in both subcutaneous and orthotopic in vivo models. In addition, combination treatment with AZD2858 enhanced clinically relevant radiation doses leading to reduced tumour volume and improved survival in orthotopic in vivo models.

CONCLUSION

GSK-3 inhibition with the small molecule inhibitor AZD2858 led to cell death in glioma stem cells preventing normal centrosome function and promoting mitotic failure. Normal human astrocytes were not affected by treatment with the inhibitor at submicromolar concentrations. Drug penetration was observed alongside an enhanced effect of clinical radiotherapy doses in vivo. The reported aberrant centrosomal duplication may be a direct consequence of failed cytokinesis suggesting a role of GSK-3 in regulation of mitosis in glioma. GSK-3 is a promising target for combination treatment with radiation in GBM management and plays a role in mitosis-associated events in glioma biology.

Successful treatment of clozapine-nonresponsive refractory hallucinations and delusions with pimavanserin, a serotonin 5HT-2A receptor inverse agonist

BACKGROUND

Clozapine was the widely accepted gold standard treatment for treatment resistant psychotic symptoms. Clozapine has efficacy of about 50% and some responding patients have to discontinue it due to serious adverse effects. The search for novel agents to use for clozapine-non-responders continues. One such possible agent is the non-dopaminergic antipsychotic pimavanserin, an inverse agonist of serotonin 5-HT2A receptors which was recently approved for the hallucinations and delusions of Parkinson's Disease Psychosis. We report here the successful results of using pimavanserin in patients with refractory hallucinations and delusions who failed to respond to clozapine. We also report similar results in refractory psychosis patients who did not receive clozapine.

METHODS

We present ten cases of patients with schizophrenia and schizoaffective disorder with refractory hallucinations and delusions who received a trial of pimavanserin when clozapine or multiple antipsychotics failed. Six of ten patients had not responded to a clozapine trial. The subjects' ages ranged between 21 and 77 years and were followed up for several months.

RESULTS

All 10 patients with refractory hallucinations and delusions showed marked response to pimavanserin 34 mg/day within 4-8 weeks, with continuation of the response for several months of follow-up. Improvements in negative symptoms and social functioning were also observed in several patients.

DISCUSSION

This series of 10 cases of patients with refractory psychosis who responded to pimavanserin is an important new finding that has never been reported before. Controlled studies comparing clozapine and pimavanserin in refractory schizophrenia are warranted to confirm these clinical observations.

The influence of zero-hours contracts on care worker well-being

Background

Care workers have an important social role which is set to expand with the increasing age of the UK population. However, the majority of care workers are employed on zero-hours contracts.

Aims

Firstly, to investigate the relationship between working conditions and employee outcomes such as engagement and general mental well-being in a sample of UK care workers and management. Secondly, to assess whether the use of zero-hours contracts affects employee well-being.

Methods

A cross-sectional survey of domiciliary care and care home employees, undertaken using the Management Standards Indicator Tool (MSIT), Utrecht Work Engagement Scale (UWES) and General Health Questionnaire (GHQ). T-tests and multivariate linear regression evaluated the differences in scoring between those with differing contractual conditions and job roles, and associations of MSIT scores with UWES and GHQ factors.

Results

Employee understanding of their role and job control were found to be priority areas for improvement in the sample. Similarly, care workers reported greater occupational demands and lower levels of control than management. However, while zero-hours contracts did not significantly influence employee well-being, these employees had greater levels of engagement in their jobs. Despite this, a greater proportion of individuals with zero-hours contracts had scores above accepted mental health cut-offs.

Conclusions

Individual understanding of their role as care workers appears to play an important part in determining engagement and general mental well-being. However, more research is needed on the influence of zero-hours contracts on well-being, particularly in groups with increased likelihood of developing mental health disorders.

Economic analysis of the breast cancer screening program used by the UK NHS: should the program be maintained?

Introduction

One key tool thought to combat the spiraling costs of late-stage breast cancer diagnosis is the use of breast cancer screening. However, over recent years, more effective treatments and questions being raised over the safety implications of using mammography have led to the cost-effectiveness of breast cancer screening to be highlighted as an important issue to investigate.

Methods

A cost–utility analysis was conducted to appraise the breast cancer screening program. The analysis considered the breast cancer screening program and its utility over a 20-year period, accounting for the typical breast cancer screening period taking place between the ages of 50 and 70 years. Analysis was conducted from the perspective of the UK National Health Service (NHS). This accepted NHS threshold was utilized for analysis of £20,000/quality-adjusted life year (QALY)–£30,000/QALY gain. A systematic literature review was conducted to obtain relevant financial, health, and probability outcomes pertaining to the breast cancer screening program.

Results

The mean incremental cost-effectiveness ratio (ICER) calculated was at a value of £11,546.11 with subsequent sensitivity analysis conducted around this value. Three sensitivity analyses were undertaken to evaluate ICERs of a range of scenarios which could occur as the following: 1) maximum costs at each node – £17,254/QALY; 2) all costs are fixed costs: screening center costs, and staff are paid for regardless of use – £14,172/QALY; and 3) combination of (1) and (2) to produce a worst case scenario £20,823/QALY.

Discussion and conclusion

The majority of calculations suggested that breast cancer screening is cost-effective. However, in our worst case scenario, the ICER fell near the bottom ceiling ratio. This makes it unclear whether the program should be available in the future, as more evidence becomes available over the risks of screening and as some currently expensive chemotherapy drugs begin to lose patents.

Hopanoids play a role in stress tolerance and nutrient storage in the cyanobacterium Nostoc punctiforme

Hopanes are abundant in ancient sedimentary rocks at discrete intervals in Earth history, yet interpreting their significance in the geologic record is complicated by our incomplete knowledge of what their progenitors, hopanoids, do in modern cells. To date, few studies have addressed the breadth of diversity of physiological functions of these lipids and whether those functions are conserved across the hopanoid-producing bacterial phyla. Here, we generated mutants in the filamentous cyanobacterium, Nostoc punctiforme, that are unable to make all hopanoids (shc) or 2-methylhopanoids (hpnP). While the absence of hopanoids impedes growth of vegetative cells at high temperature, the shc mutant grows faster at low temperature. This finding is consistent with hopanoids acting as membrane rigidifiers, a function shared by other hopanoid-producing phyla. Apart from impacting fitness under temperature stress, hopanoids are dispensable for vegetative cells under other stress conditions. However, hopanoids are required for stress tolerance in akinetes, a resting survival cell type. While 2-methylated hopanoids do not appear to contribute to any stress phenotype, total hopanoids and to a lesser extent 2-methylhopanoids were found to promote the formation of cyanophycin granules in akinetes. Finally, although hopanoids support symbiotic interactions between Alphaproteobacteria and plants, they do not appear to facilitate symbiosis between N. punctiforme and the hornwort Anthoceros punctatus. Collectively, these findings support interpreting hopanes as general environmental stress biomarkers. If hopanoid-mediated enhancement of nitrogen-rich storage products turns out to be a conserved phenomenon in other organisms, a better understanding of this relationship may help us parse the enrichment of 2-methylhopanes in the rock record during episodes of disrupted nutrient cycling.

On the optimal control of stationary diffusion processes with inaccessible boundaries and no discounting

Because there are no boundary conditions, extra properties are required in order to identify the correct potential cost function. A solution of the Dynamic Programming equation for one-dimensional processes leads to an optimal solution within a wide class of alternatives (Theorem 1), and is completely optimal if certain conditions are satisfied (Theorem 2). Necessary conditions are also given. Several examples are solved, and some extension to the multidimensional case is shown.

On the optimal control of a deterministic epidemic

A control scheme for the immunisation of susceptibles in the Kermack-McKendrick epidemic model for a closed population is proposed. The bounded control appears linearly in both dynamics and integral cost functionals and any optimal policies are of the “bang-bang” type. The approach uses Dynamic Programming and Pontryagin's Maximum Principle and allows one, for certain values of the cost and removal rates, to apply necessary and sufficient conditions for optimality and show that a one-switch candidate is the optimal control. In the remaining cases we are still able to show that an optimal control, if it exists, has at most one switch.

Enteral Feeding with Human Milk Decreases Time to Discharge in Infants following Gastroschisis Repair

OBJECTIVE

To assess the effect of enteral feeding with human milk on the time from initiation of feeds to discharge after gastroschisis repair through review of a multi-institutional database.

STUDY DESIGN

Infants who underwent gastroschisis repair between 1997 and 2012 with data recorded in the Pediatrix Medical Group Clinical Data Warehouse were categorized into 4 groups based on the percentage of days fed human milk out of the number of days fed enterally. Cox proportional hazards regression modeling was performed to determine the adjusted effect of human milk on the time from initiation of feeds to discharge.

RESULTS

Among 3082 infants, 659 (21%) were fed human milk on 0% of enteral feeding days, 766 (25%) were fed human milk on 1%-50% of enteral feeding days, 725 (24%) were fed human milk on 51%-99% of enteral feeding days, and 932 (30%) were fed human milk on 100% of enteral feeding days. Following adjustment, being fed human milk on 0% of enteral feeding days was associated with a significantly increased time to discharge compared with being fed human milk on 100% of enteral feeding days (hazard ratio [HR] for discharge per day, 0.46; 95% CI, 0.40-0.52). The same was found for infants fed human milk on 1%-50% of enteral feeding days (HR, 0.37; 95% CI, 0.32-0.41) and for infants fed human milk on 51%-99% of enteral feeding days (HR, 0.51; 95% CI, 0.46-0.57).

CONCLUSION

The use of human milk for enteral feeding of infants following repair of gastroschisis significantly reduces the time to discharge from initiation of feeds.

Examining the family-centred approach to genetic testing and counselling among UK Pakistanis: a community perspective

WHO advice suggests a family-centred approach for managing the elevated risk of recessively inherited disorders in consanguineous communities, whilst emerging policy recommends community engagement as an integral component of genetic service development. This paper explores the feasibility of the family-centred approach in the UK Pakistani origin community. The study took place within a context of debate in the media, professional and lay circles about cousin marriage causing disability in children. Using qualitative methods, a total of six single-sex focus group discussions (n = 50) were conducted in three UK cities with a high settlement of people of Pakistani origin. Tape-recorded transcripts were analysed using framework analysis. Kinship networks within Pakistani origin communities are being sustained and marriage between close blood relatives continues to take place alongside other marriage options. Study participants were critical of what was perceived as a prevalent notion that cousin marriage causes disability in children. They were willing to discuss cousin marriage and disability, share genetic information and engage with genetic issues. A desire for accurate information and a public informed about genetic issues was articulated whilst ineffective communication of genetic risk information undermined professionals in their support role. This study suggests a community that is embracing change, one in which kinship networks are still active and genetic information exchange is taking place. At the community level, these are conditions supportive of the family-centred approach to genetic testing and counselling.

Radiation protection in fixed PET/CT facilities--design and operation

We describe the design of a fixed positron emission tomography (PET)/CT facility and the use of a simulated instantaneous dose-rate plot to visually highlight areas of potentially high radiation exposure. We also illustrate the practical implementation of basic radiation protection principles based on the use of distance and shielding and the minimisation of time spent in hot areas. Staff whole body doses for 4 years are presented with results of an optimisation study analysing the dose arising from the different phases within each study using direct reading dosemeters. The total whole body dose for all staff for each patient fell from 9.5 μSv in the first full year of operation to 4.8 µSv in 2008. The maximum dose to an individual member of staff per patient decreased over the same period from 3.2 to 0.9 µSv. The optimisation study showed that the highest dose was recorded during the injection phase.

Impact of a clonal outbreak of extended-spectrum β-lactamase-producing Klebsiella pneumoniae in the development and evolution of bloodstream infections by K. pneumoniae and Escherichia coli: an 11 year experience in Oxfordshire, UK

OBJECTIVES

The objectives of this study were: (i) to describe an outbreak of multidrug-resistant Klebsiella pneumoniae in our population; (ii) to identify the potential source of this outbreak by examining antibiotic resistance trends in urocultures; (iii) to evaluate the contribution of this outbreak to resistance patterns over time in the two commonest Gram-negative blood culture isolates, namely K. pneumoniae and Escherichia coli; and (iv) to assess risk factors for multidrug resistance and the impact of this resistance on mortality and length of stay.

METHODS

We searched Microbiology and Patient Administration Service databases retrospectively and describe resistance trends in E. coli and K. pneumoniae bloodstream infections (BSIs) in Oxfordshire, UK, over an 11 year period.

RESULTS

An outbreak of a multidrug-resistant, CTX-M-15 extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae clone was identified and shown by multilocus sequence typing to belong to a novel sequence type designated ST490. This was associated with a sporadic change in resistance rates in K. pneumoniae BSIs with rates of multidrug resistance (defined as resistance to three or more antibiotic classes) reaching 40%. A case-control study showed prior antibiotic exposure as a risk factor for infection with this organism. During the same time period, rates of ESBL-producing Klebsiella spp. isolated from urocultures increased from 0.5% to almost 6%. By contrast, the rate of multidrug resistance in E. coli rose more steadily from 0% in 2000 to 10% in 2010.

CONCLUSIONS

Changes in resistance rates may be associated with outbreaks of resistant clones in K. pneumoniae. Changing resistance patterns may affect important health economic issues such as length of stay.

Characterization of natural ventilation in wastewater collection systems

The purpose of the study was to characterize natural ventilation in full-scale gravity collection system components while measuring other parameters related to ventilation. Experiments were completed at four different locations in the wastewater collection systems of Los Angeles County Sanitation Districts, Los Angeles, California, and the King County Wastewater Treatment District, Seattle, Washington. The subject components were concrete gravity pipes ranging in diameter from 0.8 to 2.4 m (33 to 96 in.). Air velocity was measured in each pipe using a carbon-monoxide pulse tracer method. Air velocity was measured entering or exiting the components at vents using a standpipe and hotwire anemometer arrangement. Ambient wind speed, temperature, and relative humidity; headspace temperature and relative humidity; and wastewater flow and temperature were measured. The field experiments resulted in a large database of measured ventilation and related parameters characterizing ventilation in full-scale gravity sewers. Measured ventilation rates ranged from 23 to 840 L/s. The experimental data was used to evaluate existing ventilation models. Three models that were based upon empirical extrapolation, computational fluid dynamics, and thermodynamics, respectively, were evaluated based on predictive accuracy compared to the measured data. Strengths and weaknesses in each model were found and these observations were used to propose a concept for an improved ventilation model.