The structure of water: A historical perspective.

Attempts to understand the molecular structure of water were first made well over a century ago. Looking back at the various attempts, it is illuminating to see how these were conditioned by the state of knowledge of chemistry and physics at the time and the experimental and theoretical tools then available. Progress in the intervening years has been facilitated by not only conceptual and theoretical advances in physics and chemistry but also the development of experimental techniques and instrumentation. Exploitation of powerful computational methods in interpreting what at first sight may seem impenetrable experimental data has led us to the consistent and detailed picture we have today of not only the structure of liquid water itself and how it changes with temperature and pressure but also its interactions with other molecules, in particular those relevant to water's role in important chemical and biological processes. Much remains to be done in the latter areas, but the experimental and computational techniques that now enable us to do what might reasonably be termed "liquid state crystallography" have opened the door to make possible further advances. Consequently, we now have the tools to explore further the role of water in those processes that underpin life itself-the very prospect that inspired Bernal to develop his ideas on the structure of liquids in general and of water in particular.

Detailed crystallographic analysis of the ice V to ice XIII hydrogen-ordering phase transition.

Ice V is a structurally highly complex material with 28 water molecules in its monoclinic unit cell. It is classified as a hydrogen-disordered phase of ice. Yet, some of its hydrogen-bonded water molecules display significant orientational order. Upon cooling pure ice V, additional orientational ordering cannot be achieved on the experimental time scale. Doping with hydrochloric acid has been shown to be most effective in enabling the phase transition of ice V to its hydrogen-ordered counterpart ice XIII. Here, we present a detailed crystallographic study of this phase transition investigating the effects of hydrochloric and hydrofluoric acid as well as lithium and potassium hydroxide doping. The magnitudes of the stepwise changes in the lattice constants during the phase transition are found to be more sensitive indicators for the extent of hydrogen order in ice XIII than the appearance of new Bragg peaks. Hydrofluoric acid and lithium hydroxide doping enable similar ordering processes as hydrochloric acid but with slower kinetics. The various possible space groups and ordered configurations of ice XIII are examined systematically, and the previously determined P21/a structure is confirmed. Interestingly, the partial hydrogen order already present in ice V is found to perpetuate into ice XIII, and these ordering processes are found to be independent of pressure. Overall, the hydrogen ordering goes along with a small increase in volume, which appears to be the origin of the slower hydrogen-ordering kinetics under pressure. Heating pressure-quenched samples at ambient pressure revealed low-temperature "transient ordering" features in both diffraction and calorimetry.

Mortality risks associated with emergency admissions during weekends and public holidays: an analysis of electronic health records.

BACKGROUND: Weekend hospital admission is associated with increased mortality, but the contributions of varying illness severity and admission time to this weekend effect remain unexplored. METHODS: We analysed unselected emergency admissions to four Oxford University National Health Service hospitals in the UK from Jan 1, 2006, to Dec 31, 2014. The primary outcome was death within 30 days of admission (in or out of hospital), analysed using Cox models measuring time from admission. The primary exposure was day of the week of admission. We adjusted for multiple confounders including demographics, comorbidities, and admission characteristics, incorporating non-linearity and interactions. Models then considered the effect of adjusting for 15 common haematology and biochemistry test results or proxies for hospital workload. FINDINGS: 257 596 individuals underwent 503 938 emergency admissions. 18 313 (4·7%) patients admitted as weekday energency admissions and 6070 (5·1%) patients admitted as weekend emergency admissions died within 30 days (p<0·0001). 9347 individuals underwent 9707 emergency admissions on public holidays. 559 (5·8%) died within 30 days (p<0·0001 vs weekday). 15 routine haematology and biochemistry test results were highly prognostic for mortality. In 271 465 (53·9%) admissions with complete data, adjustment for test results explained 33% (95% CI 21 to 70) of the excess mortality associated with emergency admission on Saturdays compared with Wednesdays, 52% (lower 95% CI 34) on Sundays, and 87% (lower 95% CI 45) on public holidays after adjustment for standard patient characteristics. Excess mortality was predominantly restricted to admissions between 1100 h and 1500 h (pinteraction=0·04). No hospital workload measure was independently associated with mortality (all p values >0·06). INTERPRETATION: Adjustment for routine test results substantially reduced excess mortality associated with emergency admission at weekends and public holidays. Adjustment for patient-level factors not available in our study might further reduce the residual excess mortality, particularly as this clustered around midday at weekends. Hospital workload was not associated with mortality. Together, these findings suggest that the weekend effect arises from patient-level differences at admission rather than reduced hospital staffing or services. FUNDING: NIHR Oxford Biomedical Research Centre.

Predictive validity of a quality measure for intensive substance use disorder treatment.

BACKGROUND: Measures of substance use disorder (SUD) treatment quality are essential tools for performance improvement. The Veterans Health Administration (VHA) developed a measure of access to and engagement in intensive outpatient programs (IOPs) for SUD. However, predictive validity, or associations between this measure and treatment outcomes, has not been examined. METHODS: Data on veterans with SUD came from 3 samples: the Outcomes Monitoring Project (N = 5436), a national evaluation of VHA mental health services (N = 339,887), and patients receiving detoxification services (N = 23,572). Propensity score-weighted mixed-effects regressions modeled associations between receiving at least 1 week of IOP treatment and patient outcomes, controlling for facility-level performance and a random effect for facility. RESULTS: Propensity score weighting reduced or eliminated observable baseline differences between patient groups. Patients who accessed IOPs versus those who did not reported significantly reduced alcohol- and drug-related symptom severity, with significantly fewer past-month days drinking alcohol (b = 1.83, P < .001) and fewer past-month days intoxicated (b = 1.55, P < .001). Patients who received IOP after detoxification services had higher 6-month utilization of SUD outpatient visits (b = 2.09, P < .001), more subsequent detoxification episodes (b = 0.25, P < .001), and lower odds of 2-year mortality (odds ratio [OR] = 0.68, 95% confidence interval [CI]: 0.61-0.75; P < .001). CONCLUSIONS: Receiving at least 1 week of SUD treatment in an IOP was associated with higher follow-up utilization, improved health outcomes, and reduced mortality. These associations lend support to the predictive validity of VHA's IOP quality measure. Future research should focus on measure feasibility and validity outside of VHA, and whether predictive validity is maintained once this quality measure is tied to performance incentives.

Diverse sources of C. difficile infection identified on whole-genome sequencing.

BACKGROUND: It has been thought that Clostridium difficile infection is transmitted predominantly within health care settings. However, endemic spread has hampered identification of precise sources of infection and the assessment of the efficacy of interventions. METHODS: From September 2007 through March 2011, we performed whole-genome sequencing on isolates obtained from all symptomatic patients with C. difficile infection identified in health care settings or in the community in Oxfordshire, United Kingdom. We compared single-nucleotide variants (SNVs) between the isolates, using C. difficile evolution rates estimated on the basis of the first and last samples obtained from each of 145 patients, with 0 to 2 SNVs expected between transmitted isolates obtained less than 124 days apart, on the basis of a 95% prediction interval. We then identified plausible epidemiologic links among genetically related cases from data on hospital admissions and community location. RESULTS: Of 1250 C. difficile cases that were evaluated, 1223 (98%) were successfully sequenced. In a comparison of 957 samples obtained from April 2008 through March 2011 with those obtained from September 2007 onward, a total of 333 isolates (35%) had no more than 2 SNVs from at least 1 earlier case, and 428 isolates (45%) had more than 10 SNVs from all previous cases. Reductions in incidence over time were similar in the two groups, a finding that suggests an effect of interventions targeting the transition from exposure to disease. Of the 333 patients with no more than 2 SNVs (consistent with transmission), 126 patients (38%) had close hospital contact with another patient, and 120 patients (36%) had no hospital or community contact with another patient. Distinct subtypes of infection continued to be identified throughout the study, which suggests a considerable reservoir of C. difficile. CONCLUSIONS: Over a 3-year period, 45% of C. difficile cases in Oxfordshire were genetically distinct from all previous cases. Genetically diverse sources, in addition to symptomatic patients, play a major part in C. difficile transmission. (Funded by the U.K. Clinical Research Collaboration Translational Infection Research Initiative and others.).

Increasing burden of community-acquired pneumonia leading to hospitalisation, 1998-2014.

BACKGROUND: Community-acquired pneumonia (CAP) is a major cause of mortality and morbidity in many countries but few recent large-scale studies have examined trends in its incidence. METHODS: Incidence of CAP leading to hospitalisation in one UK region (Oxfordshire) was calculated over calendar time using routinely collected diagnostic codes, and modelled using piecewise-linear Poisson regression. Further models considered other related diagnoses, typical administrative outcomes, and blood and microbiology test results at admission to determine whether CAP trends could be explained by changes in case-mix, coding practices or admission procedures. RESULTS: CAP increased by 4.2%/year (95% CI 3.6 to 4.8) from 1998 to 2008, and subsequently much faster at 8.8%/year (95% CI 7.8 to 9.7) from 2009 to 2014. Pneumonia-related conditions also increased significantly over this period. Length of stay and 30-day mortality decreased slightly in later years, but the proportions with abnormal neutrophils, urea and C reactive protein (CRP) did not change (p>0.2). The proportion with severely abnormal CRP (>100 mg/L) decreased slightly in later years. Trends were similar in all age groups. Streptococcus pneumoniae was the most common causative organism found; however other organisms, particularly Enterobacteriaceae, increased in incidence over the study period (p<0.001). CONCLUSIONS: Hospitalisations for CAP have been increasing rapidly in Oxfordshire, particularly since 2008. There is little evidence that this is due only to changes in pneumonia coding, an ageing population or patients with substantially less severe disease being admitted more frequently. Healthcare planning to address potential further increases in admissions and consequent antibiotic prescribing should be a priority.

Excellent Patient Care Processes in Poor Hospitals? Why Hospital-Level and Patient-Level Care Quality-Outcome Relationships Can Differ.

Studies finding weak or nonexistent relationships between hospital performance on providing recommended care and hospital-level clinical outcomes raise questions about the value and validity of process of care performance measures. Such findings may cause clinicians to question the effectiveness of the care process presumably captured by the performance measure. However, one cannot infer from hospital-level results whether patients who received the specified care had comparable, worse or superior outcomes relative to patients not receiving that care. To make such an inference has been labeled the "ecological fallacy," an error that is well known among epidemiologists and sociologists, but less so among health care researchers and policy makers. We discuss such inappropriate inferences in the health care performance measurement field and illustrate how and why process measure-outcome relationships can differ at the patient and hospital levels. We also offer recommendations for appropriate multilevel analyses to evaluate process measure-outcome relationships at the patient and hospital levels and for a more effective role for performance measure bodies and research funding organizations in encouraging such multilevel analyses.

Detailed crystallographic analysis of the ice VI to ice XV hydrogen ordering phase transition.

The D2O ice VI to ice XV hydrogen ordering phase transition at ambient pressure is investigated in detail with neutron diffraction. The lattice constants are found to be sensitive indicators for hydrogen ordering. The a and b lattice constants contract whereas a pronounced expansion in c is found upon hydrogen ordering. Overall, the hydrogen ordering transition goes along with a small increase in volume, which explains why the phase transition is more difficult to observe upon cooling under pressure. Slow-cooling ice VI at 1.4 GPa gives essentially fully hydrogen-disordered ice VI. Consistent with earlier studies, the ice XV obtained after slow-cooling at ambient pressure is best described with P-1 space group symmetry. Using a new modelling approach, we achieve the atomistic reconstruction of a supercell structure that is consistent with the average partially ordered structure derived from Rietveld refinements. This shows that C-type networks are most prevalent in ice XV, but other structural motifs outside of the classifications of the fully hydrogen-ordered networks are identified as well. The recently proposed Pmmn structural model for ice XV is found to be incompatible with our diffraction data, and we argue that only structural models that are capable of describing full hydrogen order should be used.

Recommendations for the Design and Analysis of Treatment Trials for Alcohol Use Disorders.

BACKGROUND: Over the past 60 years, the view that "alcoholism" is a disease for which the only acceptable goal of treatment is abstinence has given way to the recognition that alcohol use disorders (AUDs) occur on a continuum of severity, for which a variety of treatment options are appropriate. However, because the available treatments for AUDs are not effective for everyone, more research is needed to develop novel and more efficacious treatments to address the range of AUD severity in diverse populations. Here we offer recommendations for the design and analysis of alcohol treatment trials, with a specific focus on the careful conduct of randomized clinical trials of medications and nonpharmacological interventions for AUDs. METHODS: This paper provides a narrative review of the quality of published clinical trials and recommendations for the optimal design and analysis of treatment trials for AUDs. RESULTS: Despite considerable improvements in the design of alcohol clinical trials over the past 2 decades, many studies of AUD treatments have used faulty design features and statistical methods that are known to produce biased estimates of treatment efficacy. CONCLUSIONS: The published statistical and methodological literatures provide clear guidance on methods to improve clinical trial design and analysis. Consistent use of state-of-the-art design features and analytic approaches will enhance the internal and external validity of treatment trials for AUDs across the spectrum of severity. The ultimate result of this attention to methodological rigor is that better treatment options will be identified for patients with an AUD.

Guidelines for the Reporting of Treatment Trials for Alcohol Use Disorders.

BACKGROUND: The primary goals in conducting clinical trials of treatments for alcohol use disorders (AUDs) are to identify efficacious treatments and determine which treatments are most efficacious for which patients. Accurate reporting of study design features and results is imperative to enable readers of research reports to evaluate to what extent a study has achieved these goals. Guidance on quality of clinical trial reporting has evolved substantially over the past 2 decades, primarily through the publication and widespread adoption of the Consolidated Standards of Reporting Trials statement. However, there is room to improve the adoption of those standards in reporting the design and findings of treatment trials for AUD. METHODS: This paper provides a narrative review of guidance on reporting quality in AUD treatment trials. RESULTS: Despite improvements in the reporting of results of treatment trials for AUD over the past 2 decades, many published reports provide insufficient information on design or methods. CONCLUSIONS: The reporting of alcohol treatment trial design, analysis, and results requires improvement in 4 primary areas: (i) trial registration, (ii) procedures for recruitment and retention, (iii) procedures for randomization and intervention design considerations, and (iv) statistical methods used to assess treatment efficacy. Improvements in these areas and the adoption of reporting standards by authors, reviewers, and editors are critical to an accurate assessment of the reliability and validity of treatment effects. Continued developments in this area are needed to move AUD treatment research forward via systematic reviews and meta-analyses that maximize the utility of completed studies.

Toward cost-effective staffing mixes for Veterans Affairs substance use disorder treatment programs.

BACKGROUND: In fiscal year (FY) 2008, 133,658 patients were provided services within substance use disorders treatment programs (SUDTPs) in the U.S. Department of Veterans Affairs (VA) health care system. To improve the effectiveness and cost-effectiveness of SUDTPs, we analyze the impacts of staffing mix on the benefits and costs of specialty SUD services. This study demonstrates how cost-effective staffing mixes for each type of VA SUDTPs can be defined empirically. METHODS: We used a stepwise method to derive prediction functions for benefits and costs based on patients' treatment outcomes at VA SUDTPs nationally from 2001 to 2003, and used them to formulate optimization problems to determine recommended staffing mixes that maximize net benefits per patient for four types of SUDTPs by using the solver function with the Generalized Reduced Gradient algorithm in Microsoft Excel 2010 while conforming to limits of current practice. We conducted sensitivity analyses by varying the baseline severity of addiction problems between lower (2.5 %) and higher (97.5 %) values derived from bootstrapping. RESULTS AND CONCLUSIONS: Compared to the actual staffing mixes in FY01-FY03, the recommended staffing mixes would lower treatment costs while improving patients' outcomes, and improved net benefits are estimated from $1472 to $17,743 per patient.

A meta-analysis of topiramate's effects for individuals with alcohol use disorders.

BACKGROUND: Influenced by several trials and reviews highlighting positive outcomes, topiramate is increasingly prescribed as a treatment for alcohol use disorders (AUDs). The only previously published meta-analysis of topiramate for AUDs was limited by a sample of only 3 randomized, placebo-controlled trials (RCTs). METHODS: A systematic search identified 7 RCTs (including a total of 1,125 participants) that compared topiramate to placebo for the treatment for AUDs. This meta-analysis estimated the overall effects of topiramate on abstinence, heavy drinking, craving, and γ-glutamyltranspeptidase (GGT) outcomes and included several sensitivity analyses to account for the small sample of studies. RESULTS: Overall, the small to moderate effects favored topiramate, although the effect on craving was not quite significantly different from 0. The largest effect was found on abstinence (g = 0.468, p < 0.01), followed by heavy drinking (g = 0.406, p < 0.01), GGT (g = 0.324, p = 0.02), and craving (g = 0.312, p = 0.07) outcomes. Sensitivity analyses did not change the magnitude or direction of the results, and tests did not indicate significant publication bias. The small sample size did not allow for examination of specific moderators of the effects of topiramate. CONCLUSIONS: Topiramate can be a useful tool in the treatment of AUDs. Its efficacy, based on the current sample of studies, seems to be of somewhat greater magnitude than that of the most commonly prescribed medications for AUDs (naltrexone and acamprosate). Further research will help to identify the contexts in which topiramate is most beneficial (e.g., dose, concurrent psychotherapy, patient characteristics).

Small-angle neutron scattering study of micropore collapse in amorphous solid water.

Vapor-deposited amorphous solid water (ASW) is the most abundant solid molecular material in space, where it plays a direct role in both the formation of more complex chemical species and the aggregation of icy materials in the earliest stages of planet formation. Nevertheless, some of its low temperature physics such as the collapse of the micropore network upon heating are still far from being understood. Here we characterize the nature of the micropores and their collapse using neutron scattering of gram-quantities of D2O-ASW of internal surface areas up to 230 ± 10 m(2) g(-1) prepared at 77 K. The model-free interpretation of the small-angle scattering data suggests micropores, which remain stable up to 120-140 K and then experience a sudden collapse. The exact onset temperature to pore collapse depends on the type of flow conditions employed in the preparation of ASW and, thus, the specific surface area of the initial deposit, whereas the onset of crystallization to cubic ice is unaffected by the flow conditions. Analysis of the small-angle neutron scattering signal using the Guinier-Porod model suggests that a sudden transition from three-dimensional cylindrical pores with 15 Å radius of gyration to two-dimensional lamellae is the mechanism underlying the pore collapse. The rather high temperature of about 120-140 K of micropore collapse and the 3D-to-2D type of the transition unraveled in this study have implications for our understanding of the processing and evolution of ices in various astrophysical environments.

Relationship between bacterial strain type, host biomarkers, and mortality in Clostridium difficile infection.

BACKGROUND: Despite substantial interest in biomarkers, their impact on clinical outcomes and variation with bacterial strain has rarely been explored using integrated databases. METHODS: From September 2006 to May 2011, strains isolated from Clostridium difficile toxin enzyme immunoassay (EIA)-positive fecal samples from Oxfordshire, United Kingdom (approximately 600,000 people) underwent multilocus sequence typing. Fourteen-day mortality and levels of 15 baseline biomarkers were compared between consecutive C. difficile infections (CDIs) from different clades/sequence types (STs) and EIA-negative controls using Cox and normal regression adjusted for demographic/clinical factors. RESULTS: Fourteen-day mortality was 13% in 2222 adults with 2745 EIA-positive samples (median, 78 years) vs 5% in 20,722 adults with 27,550 EIA-negative samples (median, 74 years) (absolute attributable mortality, 7.7%; 95% CI, 6.4%-9.0%). Mortality was highest in clade 5 CDIs (25% [16 of 63]; polymerase chain reaction (PCR) ribotype 078/ST 11), then clade 2 (20% [111 of 560]; 99% PCR ribotype 027/ST 1) versus clade 1 (12% [137 of 1168]; adjusted P < .0001). Within clade 1, 14-day mortality was only 4% (3 of 84) in ST 44 (PCR ribotype 015) (adjusted P = .05 vs other clade 1). Mean baseline neutrophil counts also varied significantly by genotype: 12.4, 11.6, and 9.5 × 10(9) neutrophils/L for clades 5, 2 and 1, respectively, vs 7.0 × 10(9) neutrophils/L in EIA-negative controls (P < .0001) and 7.9 × 10(9) neutrophils/L in ST 44 (P = .08). There were strong associations between C. difficile-type-specific effects on mortality and neutrophil/white cell counts (rho = 0.48), C-reactive-protein (rho = 0.43), eosinophil counts (rho = -0.45), and serum albumin (rho = -0.47). Biomarkers predicted 30%-40% of clade-specific mortality differences. CONCLUSIONS: C. difficile genotype predicts mortality, and excess mortality correlates with genotype-specific changes in biomarkers, strongly implicating inflammatory pathways as a major influence on poor outcome after CDI. PCR ribotype 078/ST 11 (clade 5) leads to severe CDI; thus ongoing surveillance remains essential.

Placebo group improvement in trials of pharmacotherapies for alcohol use disorders: a multivariate meta-analysis examining change over time.

OBJECTIVE: Placebo group improvement in pharmacotherapy trials has been increasing over time across several pharmacological treatment areas. However, it is unknown to what degree increasing improvement has occurred in pharmacotherapy trials for alcohol use disorders or what factors may account for placebo group improvement. This meta-analysis of 47 alcohol pharmacotherapy trials evaluated (1) the magnitude of placebo group improvement, (2) the extent to which placebo group improvement has been increasing over time, and (3) several potential moderators that might account for variation in placebo group improvement. METHOD: Random-effects univariate and multivariate analyses were conducted that examined the magnitude of placebo group improvement in the 47 studies and several potential moderators of improvement: (a) publication year, (b) country in which the study was conducted, (c) outcome data source/type, (d) number of placebo administrations, (e) overall severity of study participants, and (f) additional psychosocial treatment. RESULTS: Substantial placebo group improvement was found overall and improvement was larger in more recent studies. Greater improvement was found on moderately subjective outcomes, with more frequent administrations of the placebo, and in studies with greater participant severity of illness. However, even after controlling for these moderators, placebo group improvement remained significant, as did placebo group improvement over time. CONCLUSIONS: Similar to previous pharmacotherapy placebo research, substantial pretest to posttest placebo group improvement has occurred in alcohol pharmacotherapy trials, an effect that has been increasing over time. However, several plausible moderator variables were not able to explain why placebo group improvement has been increasing over time.

The declining efficacy of naltrexone pharmacotherapy for alcohol use disorders over time: a multivariate meta-analysis.

BACKGROUND: Oral naltrexone is an FDA-approved medication for treating alcohol use disorders. Although its efficacy has been supported in multiple clinical trials, an earlier review found that its effect sizes (ESs) on relapse to heavy drinking and, to a lesser extent, percent days drinking were smaller in more recent trials and in multicenter than in single-site studies. We examined whether these findings held when studies from 2004 to 2009 were taken into account, and whether single-site versus multicenter trials, the use of placebo run-in periods, and placebo group improvement accounted for variation in naltrexone effects and decreasing effects over time. METHODS: A multivariate meta-analysis of naltrexone pharmacotherapy trials for alcohol use disorders was conducted. All analyses simultaneously modeled ESs on outcomes of percent days abstinent and relapse to heavy drinking. Potential moderators of medication effects that were examined included publication year, multicenter design (vs. single site), placebo run-in period, and placebo group improvement. RESULTS: Statistically significant between-group differences on percent days abstinent (the inverse of percent days drinking) and relapse to heavy drinking favored naltrexone over placebo. Year of publication was a significant moderator for both outcomes, with more recent trials having smaller ESs. Neither multi- versus single-site study, the interaction between multi- versus single-site study and year of publication, nor placebo run-in period was a significant moderator of naltrexone effects. Although placebo group improvement was modestly associated with smaller between-group naltrexone versus placebo ESs, only 21 studies provided usable information on placebo group improvement. Within those studies, there was no relationship between naltrexone ESs and time, so placebo group improvement was not examined as a moderator of that relationship. CONCLUSIONS: Naltrexone ESs have attenuated over time. Moderators that explain why effects have been decreasing remain to be determined.

Predictors of first recurrence of Clostridium difficile infection: implications for initial management.

Symptomatic recurrence of Clostridium difficile infection (CDI) occurs in approximately 20% of patients and is challenging to treat. Identifying those at high risk could allow targeted initial management and improve outcomes. Adult toxin enzyme immunoassay-positive CDI cases in a population of approximately 600,000 persons from September 2006 through December 2010 were combined with epidemiological/clinical data. The cumulative incidence of recurrence ≥ 14 days after the diagnosis and/or onset of first-ever CDI was estimated, treating death without recurrence as a competing risk, and predictors were identified from cause-specific proportional hazards regression models. A total of 1678 adults alive 14 days after their first CDI were included; median age was 77 years, and 1191 (78%) were inpatients. Of these, 363 (22%) experienced a recurrence ≥ 14 days after their first CDI, and 594 (35%) died without recurrence through March 2011. Recurrence risk was independently and significantly higher among patients admitted as emergencies, with previous gastrointestinal ward admission(s), last discharged 4-12 weeks before first diagnosis, and with CDI diagnosed at admission. Recurrence risk also increased with increasing age, previous total hours admitted, and C-reactive protein level at first CDI (all P < .05). The 4-month recurrence risk increased by approximately 5% (absolute) for every 1-point increase in a risk score based on these factors. Risk factors, including increasing age, initial disease severity, and hospital exposure, predict CDI recurrence and identify patients likely to benefit from enhanced initial CDI treatment.

Surveillance of infection severity: a registry study of laboratory diagnosed Clostridium difficile.

BACKGROUND: Changing clinical impact, as virulent clones replace less virulent ones, is a feature of many pathogenic bacterial species and can be difficult to detect. Consequently, innovative techniques monitoring infection severity are of potential clinical value. METHODS AND FINDINGS: We studied 5,551 toxin-positive and 20,098 persistently toxin-negative patients tested for Clostridium difficile infection between February 1998 and July 2009 in a group of hospitals based in Oxford, UK, and investigated 28-day mortality and biomarkers of inflammation (blood neutrophil count, urea, and creatinine concentrations) collected at diagnosis using iterative sequential regression (ISR), a novel joinpoint-based regression technique suitable for serial monitoring of continuous or dichotomous outcomes. Among C. difficile toxin-positive patients in the Oxford hospitals, mean neutrophil counts on diagnosis increased from 2003, peaked in 2006-2007, and then declined; 28-day mortality increased from early 2006, peaked in late 2006-2007, and then declined. Molecular typing confirmed these changes were likely due to the ingress of the globally distributed severe C. difficile strain, ST1. We assessed the generalizability of ISR-based severity monitoring in three ways. First, we assessed and found strong (p<0.0001) associations between isolation of the ST1 severe strain and higher neutrophil counts at diagnosis in two unrelated large multi-centre studies, suggesting the technique described might be useful elsewhere. Second, we assessed and found similar trends in a second group of hospitals in Birmingham, UK, from which 5,399 cases were analysed. Third, we used simulation to assess the performance of this surveillance system given the ingress of future severe strains under a variety of assumptions. ISR-based severity monitoring allowed the detection of the severity change years earlier than mortality monitoring. CONCLUSIONS: Automated electronic systems providing early warning of the changing severity of infectious conditions can be established using routinely collected laboratory hospital data. In the settings studied here these systems have higher performance than those monitoring mortality, at least in C. difficile infection. Such systems could have wider applicability for monitoring infections presenting in hospital.

Characterisation of Clostridium difficile hospital ward-based transmission using extensive epidemiological data and molecular typing.

BACKGROUND: Clostridium difficile infection (CDI) is a leading cause of antibiotic-associated diarrhoea and is endemic in hospitals, hindering the identification of sources and routes of transmission based on shared time and space alone. This may compromise rational control despite costly prevention strategies. This study aimed to investigate ward-based transmission of C. difficile, by subdividing outbreaks into distinct lineages defined by multi-locus sequence typing (MLST). METHODS AND FINDINGS: All C. difficile toxin enzyme-immunoassay-positive and culture-positive samples over 2.5 y from a geographically defined population of ~600,000 persons underwent MLST. Sequence types (STs) were combined with admission and ward movement data from an integrated comprehensive healthcare system incorporating three hospitals (1,700 beds) providing all acute care for the defined geographical population. Networks of cases and potential transmission events were constructed for each ST. Potential infection sources for each case and transmission timescales were defined by prior ward-based contact with other cases sharing the same ST. From 1 September 2007 to 31 March 2010, there were means of 102 tests and 9.4 CDIs per 10,000 overnight stays in inpatients, and 238 tests and 15.7 CDIs per month in outpatients/primary care. In total, 1,276 C. difficile isolates of 69 STs were studied. From MLST, no more than 25% of cases could be linked to a potential ward-based inpatient source, ranging from 37% in renal/transplant, 29% in haematology/oncology, and 28% in acute/elderly medicine to 6% in specialist surgery. Most of the putative transmissions identified occurred shortly (≤ 1 wk) after the onset of symptoms (141/218, 65%), with few >8 wk (21/218, 10%). Most incubation periods were ≤ 4 wk (132/218, 61%), with few >12 wk (28/218, 13%). Allowing for persistent ward contamination following ward discharge of a CDI case did not increase the proportion of linked cases after allowing for random meeting of matched controls. CONCLUSIONS: In an endemic setting with well-implemented infection control measures, ward-based contact with symptomatic enzyme-immunoassay-positive patients cannot account for most new CDI cases.