A198 THE LONG-TERM IMPACT OF ENVIRONMENTAL EXPOSURES ON HOST HEALTH AND THE RISK FACTORS OF CROHN'S DISEASE

Background

Several environmental factors are associated with Crohn’s disease (CD) in large case-control studies; however, it is not clear how these factors maybe be influenced by age of exposure and if they are related to alterations in pre-disease biological markers of CD risk.

Purpose

To investigate the association between environmental factors in different age groups with future risk of CD onset and assess their relation to other pre-disease biomarkers.

Method

We used an environmental risk assessment questionnaire (ERA) to collect information from healthy first-degree relatives(FDR) of CD enrolled in the CCC-GEM project. ERA was a multi-item questionnaire querying 69 questions under 7 section headings: background, cultural/ethnic, smoking history, medical history, family history, environmental history and pet history. For the environmental and pet sections, current and historical (<1, 2-4, 5-15 years old) data was captured at the time of recruitment. We used Cox proportional hazard models to identify exposures associated with future CD onset. Next, we used regression models to identify the relationship of exposures with biological factors associated with CD risk previously identified by our group i.e.: i) intestinal permeability using urinary fractional excretion of lactulose to mannitol ratio (LMR) with LMR≥0.025 defined as abnormal; ii) subclinical inflammation using fecal calprotectin (FCP) with FCP≥100µg/g; and iii) fecal microbiome composition and diversity using 16S rDNA sequencing. Two-sided p<0.05 (or false discovery rate corrected p<0.05) were considered significant.

Result(s)

A total of 4289 FDRs were recruited, 47% were male, median recruitment age was 17.0 years[6-35]. After a median follow-up of 5.6-years (IQR=3.42-8.67), 86 FDRs developed CD. Living with a dog between age 5-15 (Hazard Ratio (HR)=0.61; 95% confidence interval (CI)=0.39-0.95), and a large family size (>3) in the first year of life (HR=0.41; 95% CI=0.22-0.89) were protective against CD onset. Conversely, having a bird at time of survey (HR=2.84; CI=1.37-5.90), and having a sibling with CD (HR=2.07; 95% CI=1.18-3.63) were risk factors for CD onset. We found that owning a dog between age of 5-15 (Odd Ratio(OR)=0.77, 95% CI=0.65-0.90) was significantly associated with LMR, nine taxa bacterial and higher chao1 diversity index. Having a bird at time of survey was significantly associated with FCP (OR=2.04, 95% CI=1.33-3.11). There was no association between large family size and having a CD sibling with gut microbiome, FCP or LMR.

Conclusion(s)

The study identified four environmental factors associated with future development of CD. Among them, exposure to dogs during early life was protective against CD onset and might be explained by its association with normal gut permeability and microbiome. We also identified that having a bird at recruitment increased risk of CD onset which might be mediated by an increase in subclinical inflammation.

Submitted on behalf of the CCC-GEM consortium

Disclosure of Interest

None Declared

A39 HEALTHY FIRST-DEGREE RELATIVES FROM MULTIPLEX FAMILIES VERSUS SIMPLEX HARBOR A HIGHER RISK OF DEVELOPING CROHN'S DISEASE AND ARE ASSOCIATED WITH SUBCLINICAL INFLAMMATION AND ALTERED MICROBIOME COMPOSITION

Background

Healthy individuals within families with multiple affected members (multiplex families) with Crohn’s disease (CD) have a notably high risk of developing CD. No large prospective pre-disease cohort has assessed differences in preclinical intestinal inflammation, permeability, fecal microbiome, and genetics in healthy at-risk subjects from multiplex families.

Purpose

We aimed to assess differences in subclinical gut inflammation, genetic risk, gut barrier function, and fecal microbiota composition between first-degree relatives (FDRs) from families with 2 or more affected members (multiplex) and families with only one affected member (simplex). Also, we aimed to assess the risk of future CD onset in subjects from multiplex versus simplex families.

Method

We utilized the GEM Project cohort of healthy FDRs of CD patients. Subclinical gut inflammation was assessed using fecal calprotectin (FCP) at recruitment. Gut barrier function was assessed using the lactulose-to-mannitol ratio (LMR). For assessment of the CD-related genetic risk, CD-polygenic risk scores (CD-PRS) were calculated. Microbiome composition was assessed by sequencing fecal 16S ribosomal RNA. Generalized estimating equations logistic regression and LEfSe (PMID: 21702898) were used to assess the associations between multiplex status and different outcomes. A Cox proportional hazards model was used to assess time-related risk of future onset of CD.

Result(s)

4385 subjects were included. Median age was 17 [IQR 12-24] years, 52.9% were female, 69.4% were siblings and 30.6% were offspring. 4052 (92.4%) and 333 (7.6 %) were simplex and multiplex subjects, respectively. After adjusting for age, sex, family size, and relation to proband, multiplex status was significantly associated with higher baseline FCP (p=0.038), but was not associated with either baseline LMR or CD-PRS (p=0.19 and p=0.33, respectively).

We found no significant differences in alpha diversity (Shannon index) (p=0.57) between simplex and multiplex subjects. Beta diversity analysis assessed by the Bray-Curtis dissimilarity index did not reveal significant differences (R2=3e-04, p=0.607). The genera Eisenbergiella, Eggerthellaceae uncultured, and Morganella, were significantly more abundant in multiplex subjects, whereas Lachnospira, Sutterella, Lachnospiraceae_NK4A136_group, and Lachnospiraceae_UCG_004 less abundant.

The risk of CD onset was significantly higher in multiplex subjects. In multivariable analysis, multiplex status at recruitment was associated with increased risk of CD onset (adjusted HR 3.41, 95% CI 1.70-6.87, p=0.00055), after adjusting for demographics, FCP, LMR, and CD-PRS.

Conclusion(s)

Multiplex status compared to simplex is associated with a 3.4-fold increased risk of CD onset, a higher FCP, and fecal bacterial composition. A comprehensive assessment of environmental factors that increase CD risk in multiplex families remains to be elucidated in future studies.

Disclosure of Interest

None Declared

A218 ASSOCIATIONS BETWEEN ADHERENCE TO LITERATURE-DERIVED DIETARY INDICES AND PRE-DISEASE BIOMARKERS: IMPLICATIONS FOR CROHN’S DISEASE PREVENTION

Background

The incidence of Crohn’s disease (CD) is increasing globally, indicating a significant environmental influence such as diet. A plethora of dietary adherence (DA) patterns exist in the literature: the Mediterranean Diet (MD), Empirical Dietary Inflammatory Pattern (EDIP), Specific Carbohydrate Diet (SCD), and low Fermentable Oligosaccharide, Disaccharide, Monosaccharide, or Polyol diet (FODMAP) are all potential candidates to maintain a reduced level of inflammation, improving gastrointestinal function. Contrary, the Westernized diet (WD) is generally reported as a diet promoting inflammation in humans.

Purpose

To determine if DA to literature-derived dietary indices in a cohort of first-degree relatives (FDRs) of CD patients can modulate pre-disease biomarkers.

Method

We used food frequency questionnaire (FFQ) data from 2,696 healthy FDR subjects of the Crohn’s Colitis Canada- Genes, Environment, Microbial (CCC-GEM) project. We rederived each of the following scores using our FFQ data, utilizing originally described methods for the MD, EDIP, SCD, low FODMAP, and WD to obtain DA. Each diet was correlated pairwise via Kendall’s Tau.

We fit multivariable regression models to identify the association of DA (top quintile vs remaining) and: i) intestinal permeability using urinary fractional excretion of lactulose to mannitol ratio (LMR), LMR≥0.03 defined abnormal; ii) subclinical inflammation using fecal calprotectin (FCP) measured with BÜHLMANN fCAL® ELISA, FCP≥250µg/g defined inflammation; and iii) fecal microbiome richness and composition using 16S rRNA sequencing. Two-sided p<0.05 for primary and q<0.05 for secondary analysis defined significance.

Result(s)

There were positive correlations between the MD, SCD, and low FODMAP, these diets negatively correlated with the WD. The EDIP negatively correlated with the SCD and low FODMAP, did not correlate with the MD, and positively correlated with the WD. No diet was associated with abnormal LMR or FCP. Only the SCD was associated with increased microbial richness (q=0.03). All diets were associated with microbial genera: the MD (n=18 taxa, (2.0^-7<q-values< 0.04), EDIP (n=9, [2.8^-4-0.05]), SCD (n=13, [3.7^-11-0.05]), low FODMAP (n=14, [1.3^-7-0.05]), and WD (n=1, [0.03]).

Conclusion(s)

This study shows that literature-derived dietary indices correlate generally with each other, yet none were not associated with abnormal LMR or FCP. However, we found that diet can impact microbiome richness and composition. Thus, it is tempting to speculate that diet is a possible intervention capable of maintain microbiome homeostasis to reduce future risk of CD.

Submitted on behalf of the CCC-GEM consortium.

Funding

Crohn’s and Colitis Canada Genetics Environment Microbial (CCC-GEM) III

The Leona M. and Harry B. Helmsley Charitable Trust

Kenneth Croitoru is the recipient of the Canada Research Chair in Inflammatory Bowel Disease

Disclosure of Interest

None Declared

A238 BILE ACID COMPOSITION AND DIETARY FAT: IMPLICATIONS FOR CROHN’S DISEASE IN A COHORT OF HEALTHY FIRST-DEGREE RELATIVES

Background

Crohn’s disease (CD) is a chronic relapsing inflammatory disease of the gastrointestinal tract. The etiology of CD may arise from complex interactions including host genetics, diet, and the intestinal microbiome. Increased consumption of saturated fats, characteristic of the Western diet, is a known risk factor for CD. Dietary fat (DF) is absorbed by the host through the release of primary bile acids (PBAs) and bio-transformed by the microbiome into secondary bile acids (SBAs). Altogether, bile acids (BAs) can act as signaling molecules involved in host immune regulation and potentially in CD onset.

Purpose

To investigate the relationship between CD risk, BAs, and DF, and evaluate the predictive performance of CD onset of these factors by developing machine learning models.

Method

We used samples healthy first-degree relatives (FDRs) recruited as part of the Crohn’s Colitis Canada- Genes, Environment, Microbial (GEM) project. Those who developed CD (n=87) were matched 1:4 by age, sex, follow-up time, and geographic location with control FDRs remaining healthy (n=347).

Serum, urine, and stool BA were measured using ultrahigh Performance Liquid Chromatography-Tandem Mass Spectroscopy. DF types were derived from food frequency questionnaire data. We used conditional logistic regressions to identify associations between CD onset, BAs (n=93), and DFs (n=9). We further explored the relationships of significant CD-related BAs and DF via Generalized Estimation Equations. Finally, we used a tree-based machine-learning algorithm (XGBoost) with 5-fold cross-validation to assess the prediction performance of CD onset using BA from all sources as well as DF. Two-sided p<0.05 was considered significant.

Result(s)

In total, 10 of 93 BAs, and two of nine DFs were significantly associated with increased odds of CD onset (p<0.05). Additionally, five BAs were significantly associated with DF (p<0.05). Serum-derived BAs had the best predictive performance for CD, with a mean AUC of 0.70 [95% CI: 0.63;0.76], followed by stool derived BAs with a mean AUC= 0.65 [0.55;0.75], and followed by urine derived Bas with a mean AUC= 0.57 [0.48;0.66]. Lastly DF was not a predictive marker of CD onset with a mean AUC= 0.50 [0.41;0.60].

Conclusion(s)

This study suggests that BAs are associated with the pathogenesis of CD and the effects may be influenced by DF. Serum-derived BAs may be able to better predict the risk of CD than other stool or urine derived BA, while DF is not directly implicated in CD risk.

Submitted on behalf of the CCC-GEM consortium.

Funding

Crohn’s and Colitis Canada Genetics Environment Microbial (CCC-GEM) III

The Leona M. and Harry B. Helmsley Charitable Trust

Kenneth Croitoru is the recipient of the Canada Research Chair in Inflammatory Bowel Diseases

The International Organization for the Study of Inflammatory Bowel Diseases (IOIBD)

Jingcheng Shao is the recipient of a Data Science Institute Summer Undergraduate Data Science award

Disclosure of Interest

None Declared

Determining the gluonic gravitational form factors of the proton

The proton is one of the main building blocks of all visible matter in the Universe¹. Among its intrinsic properties are its electric charge, mass and spin². These properties emerge from the complex dynamics of its fundamental constituents-quarks and gluons-described by the theory of quantum chromodynamics^3-5. The electric charge and spin of protons, which are shared among the quarks, have been investigated previously using electron scattering². An example is the highly precise measurement of the electric charge radius of the proton⁶. By contrast, little is known about the inner mass density of the proton, which is dominated by the energy carried by gluons. Gluons are hard to access using electron scattering because they do not carry an electromagnetic charge. Here we investigated the gravitational density of gluons using a small colour dipole, through the threshold photoproduction of the J/ψ particle. We determined the gluonic gravitational form factors of the proton^7,8 from our measurement. We used a variety of models^9-11 and determined, in all cases, a mass radius that is notably smaller than the electric charge radius. In some, but not all cases, depending on the model, the determined radius agrees well with first-principle predictions from lattice quantum chromodynamics¹². This work paves the way for a deeper understanding of the salient role of gluons in providing gravitational mass to visible matter.

Determination of the ^{27}Al Neutron Distribution Radius from a Parity-Violating Electron Scattering Measurement

We report the first measurement of the parity-violating elastic electron scattering asymmetry on ^{27}Al. The ^{27}Al elastic asymmetry is A_{PV}=2.16±0.11(stat)±0.16(syst)  ppm, and was measured at ⟨Q^{2}⟩=0.02357±0.00010  GeV^{2}, ⟨θ_{lab}⟩=7.61°±0.02°, and ⟨E_{lab}⟩=1.157  GeV with the Q_{weak} apparatus at Jefferson Lab. Predictions using a simple Born approximation as well as more sophisticated distorted-wave calculations are in good agreement with this result. From this asymmetry the ^{27}Al neutron radius R_{n}=2.89±0.12  fm was determined using a many-models correlation technique. The corresponding neutron skin thickness R_{n}-R_{p}=-0.04±0.12  fm is small, as expected for a light nucleus with a neutron excess of only 1. This result thus serves as a successful benchmark for electroweak determinations of neutron radii on heavier nuclei. A tree-level approach was used to extract the ^{27}Al weak radius R_{w}=3.00±0.15  fm, and the weak skin thickness R_{wk}-R_{ch}=-0.04±0.15  fm. The weak form factor at this Q^{2} is F_{wk}=0.39±0.04.

Form Factors and Two-Photon Exchange in High-Energy Elastic Electron-Proton Scattering

We present new precision measurements of the elastic electron-proton scattering cross section for momentum transfer (Q^{2}) up to 15.75  (GeV/c)^{2}. Combined with existing data, these provide an improved extraction of the proton magnetic form factor at high Q^{2} and double the range over which a longitudinal or transverse separation of the cross section can be performed. The difference between our results and polarization data agrees with that observed at lower Q^{2} and attributed to hard two-photon exchange (TPE) effects, extending to 8  (GeV/c)^{2} the range of Q^{2} for which a discrepancy is established at >95% confidence. We use the discrepancy to quantify the size of TPE contributions needed to explain the cross section at high Q^{2}.

Where have the enteric viruses gone? - Differential effects on frequent causes of infectious diarrhoea by SARS-CoV-2 pandemic lockdown measures

Background

Measures of distancing, wearing face/medical masks and lockdown introduced in many countries to meet the challenges of the SARS-CoV-2 pandemic have led to gross changes in the epidemiology of important infections. The observation of decline of positive norovirus tests after introduction of lockdown in Germany led us to investigate changes in the detection of major causes of diarrhoea by comparing pre-pandemic quarters (PPQ: 1Q/17 through 1Q/20) since 2017 and pandemic quarters (PQ: 2Q/20 through 1Q/21).

Methods and setting

Bioscientia Laboratory Ingelheim is a large regional clinical pathology laboratory serving > 50 hospitals and > 5000 general practitioners and specialist outpatient practices located in the federal states Hesse, Rhineland-Palatinate and North Rhine-Westphalia, Germany. Antigen detection assays were used for detection of astrovirus, adenovirus, rotavirus, and Campylobacter antigen and Clostridium difficile Toxin A/B, while norovirus was detected by qualitative RT-PCR.

Findings

The mean positivity-ratios of norovirus, adenovirus and astrovirus assays were 3-20 fold lower in periods PQ (2Q/20 through 1Q/21) compared to PPQ (1Q/17 through 1Q/20) (p<.01). The mean positivity-ratio was lower in PQ compared to PPQ for rotavirus (p=.31), but failed to reach statistical significance, while for campylobacter antigen (p=.91) and C. difficile Toxin A/B (p=.17) the mean positivity-ratio was even higher in PQ compared to PPQ.

Conclusions

Apparently, hygienic measures used to contain the SARS-CoV-2 pandemic have differential effects on incidence of diarrhoea viruses as compared to bacterial gastrointestinal agents, particularly C. difficile, which may lead to re-evaluate measures implemented against this important cause of nosocomial diarrhoea.

Changing epidemiology of vancomycin-resistant Enterococcus faecium: Results of a genome-based study at a regional neurological acute hospital with intensive care and early rehabilitation treatment

Background

Vancomycin-resistant Enterococcus faecium (VREfm) are an emerging threat worldwide. In Germany, a VRE-belt with higher VREfm prevalences transversing its central east-west axis and including the state of Hesse was previously described. Recently, we detected a predominant VREfm clone in hospitals throughout the Rhine-Main metropolitan area of Hesse.

Aim

Here we expanded our study on VREfm to a regional neurological acute hospital outside of the metropolitan area with patient referrals from throughout Hesse and the neighboring federal state of Rhineland-Palatinate.

Material/Methods

VREfm isolates obtained between 2016-2018 from a regional neurological acute hospital with intensive care and early rehabilitation units were investigated (n=55). Patient data was collected and analyzed together with whole-genome sequencing data to investigate antibiotic resistance and virulence determinants of the VREfm. The population structure of VREfm was investigated using the Core genome-based multilocus sequence typing (cgMLST).

Findings

The average age of the patients was 67.1 years. For 96% of the patients, a previous hospital stay was reported. 64% of the patients were treated with antibiotics. All VREfm harbored the vanB vancomycin resistance gene. The multilocus sequence types (STs) detected changed abruptly from four different STs in 2016 to a predominant ST in 2017 and 2018 (ST117). Most of the ST117 isolates were members of the cgMLST type CT71.

Conclusion

The results indicate a sudden shift of the VREfm population structure from a semi-heterogeneous population to a pre-dominant clone within an interval of two years. Further investigations are warranted to understand the epidemiology and emergence of this clone.

Prevalence of SARS-CoV-2 IgG antibodies in a large prospective cohort study of elite football players in Germany (May-June 2020): implications for a testing protocol in asymptomatic individuals and estimation of the rate of undetected cases

OBJECTIVES

Elite professional football players and staff are a unique group that might give insight into the epidemiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Germany and thus can serve as a model for geographical distribution and an estimation of undetected infections.

METHODS

In this prospective cohort study seroprevalence was determined twice in May and June 2020 in players and staff from the German Bundesliga. As screening assays, a commercial ELISA (Euroimmun) and a chemiluminescent immunoassay (CLIA) (Roche) were used, and an in-house neutralization assay (NT) was used as reference standard. Participants were tested twice weekly using PCR from nasopharyngeal and/or oropharyngeal swabs.

RESULTS

Seroprevalence (NT used as confirmation) in 2164 samples from 1184 players and staff was rather similar in May (23/1157, 1.99%) and June (21/1007, 2.09%). All participants were PCR-negative during the study period. Significant regional differences in seroprevalence were not observed. When comparing seroprevalence with the cumulative incidence of infections derived from the German notification system (subgroup matching to cohort; men, age 20-69 years), IgG was found eight to ten times more frequently, pointing to a high rate of undetected infection. ELISA and CLIA correlated only moderately (κ 0.52).

CONCLUSIONS

Seroprevalence with a high-quality diagnostic in Germany seemed to be around 2%. The number of undetected infections seems to be eight to ten times higher than in notification data. The quality of antibody assays is rather variable, thus results should ideally be confirmed at least by a second assay to prove IgG positivity.

Ruling out Color Transparency in Quasielastic ^{12}C(e,e^{'}p) up to Q^{2} of 14.2 (GeV/c)^{2}

Quasielastic ^{12}C(e,e^{'}p) scattering was measured at spacelike 4-momentum transfer squared Q^{2}=8, 9.4, 11.4, and 14.2  (GeV/c)^{2}, the highest ever achieved to date. Nuclear transparency for this reaction was extracted by comparing the measured yield to that expected from a plane-wave impulse approximation calculation without any final state interactions. The measured transparency was consistent with no Q^{2} dependence, up to proton momenta of 8.5  GeV/c, ruling out the quantum chromodynamics effect of color transparency at the measured Q^{2} scales in exclusive (e,e^{'}p) reactions. These results impose strict constraints on models of color transparency for protons.

Successful return to professional men's football (soccer) competition after the COVID-19 shutdown: a cohort study in the German Bundesliga

OBJECTIVES

To evaluate the restart of the German Bundesliga (football (soccer)) during the COVID-19 pandemic from a medical perspective.

METHODS

Participants were male professional football players from the two highest German leagues and the officials working closely with them. Our report covers nine match days spread over 9 weeks (May to July 2020). Daily symptom monitoring, PCR testing for SARS-CoV-2 RNA twice weekly, and antibody tests (on two occasions-early during the phase in May 2020 and in the week of the last match) were conducted. Target variables were: (1) onset of typical COVID-19 symptoms, (2) positive PCR results, and (3) IgG seroconversion against SARS-CoV-2. All detected seroconversions were controlled by neutralisation tests.

FINDINGS

Suspicious symptoms were reported for one player; an immediate additional PCR test as well as all subsequent diagnostic and antibody tests proved negative for coronavirus. Of 1702 regularly tested individuals (1079 players, 623 officials members), 8 players and 4 officials tested positive during one of the first rounds of PCR testing prior to the onset of team training, 2 players during the third round. No further positive results occurred during the remainder of the season. 694 players and 291 officials provided two serum samples for antibody testing. Nine players converted from negative/borderline to positive (without symptoms); two players who initially tested positive tested negative at the end of the season. 22 players remained seropositive throughout the season. None of the seroconversions was confirmed in the neutralisation test.

CONCLUSION

Professional football training and matches can be carried out safely during the COVID-19 pandemic. This requires strict hygiene measures including regular PCR testing.

Contrasting effects of linezolid on healthy and dysfunctional human neutrophils: reducing C5a-induced injury

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of ventilator-associated pneumonia (VAP). Patients with VAP have poorly functioning neutrophils, related to increased levels of the complement fragment C5a. The antibiotic linezolid has been useful in controlling MRSA-related VAP infections; however clinical benefit does not always correlate with antimicrobial effect, suggesting the possibility of immunomodulatory properties. Here the effects of linezolid on healthy and dysfunctional neutrophils (modelled by C5a-induced injury) was investigated. Functional assays (killing, phagocytosis, transmigration, and respiratory burst) were used to assess the effects of pre-, co- and post-incubating linezolid (0.4-40 mg/L) with healthy neutrophils relative to those with C5a-induced injury. C5a decreased neutrophil killing, and phagocytosis of MRSA. Furthermore, C5a significantly decreased neutrophil transmigration to IL-8, but did not affect respiratory burst. Co-incubation of linezolid significantly improved killing of MRSA by dysfunctional neutrophils, which was supported by concomitant increases in phagocytosis. Conversely linezolid impaired killing responses in healthy neutrophils. Pre- or post-incubation of linezolid prior or following C5a induced injury had no effect on neutrophil function. This study suggests that linezolid has immunomodulatory properties that protect human neutrophils from injury and provides insight into its mode of action beyond a basic antibiotic.

Precision Measurement of the Beam-Normal Single-Spin Asymmetry in Forward-Angle Elastic Electron-Proton Scattering

A beam-normal single-spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable related to the imaginary part of the two-photon exchange process. We report a 2% precision measurement of the beam-normal single-spin asymmetry in elastic electron-proton scattering with a mean scattering angle of θ_{lab}=7.9° and a mean energy of 1.149 GeV. The asymmetry result is B_{n}=-5.194±0.067(stat)±0.082 (syst) ppm. This is the most precise measurement of this quantity available to date and therefore provides a stringent test of two-photon exchange models at far-forward scattering angles (θ_{lab}→0) where they should be most reliable.

A26 PEDIATRIC-ONSET INFLAMMATORY BOWEL DISEASE INCREASES THE RISK OF VENOUS THROMBOEMBOLISM: A CANGIEC POPULATION-BASED STUDY

Background

Inflammatory bowel disease (IBD) increases the risk of venous thromboembolism (VTE) in patients of all ages but the risk of VTE among Canadian children with IBD has not previously been investigated.

Aims

Report the incidence of VTE and subtypes pulmonary embolism (PE) and deep vein thrombosis (DVT) in children with and without IBD.

Methods

Children diagnosed with IBD &lt;16y were identified from health administrative data in Ontario (2002–2014), Alberta (2007–2015), and Nova Scotia (2002–2012) using validated algorithms and matched by age and sex to children without IBD (1:5 ratio). Validated ICD-10 codes identified hospitalizations for incident VTE (DVT, PE, and sinovenous thrombosis). Province-specific 5-year cumulative incidence per 1000 person-years (PY) of VTEs were pooled using fixed-effects generalized linear mixed models with a Freeman-Tukey double arcsine transformation. Incidence rate ratios (IRR) within 5 years of diagnosis were pooled using fixed-effects generalized linear mixed models to compare children with and without IBD, and children with Crohn’s disease (CD) and ulcerative colitis (UC).

Results

3127 children with IBD (1826 CD; 1045 UC) were matched to 15,635 children without IBD. The cumulative incidence of VTE within 5 years of IBD diagnosis was 2.8 (95% CI 2.1–3.8) per 1000 PYs compared to 0.13 (95% CI 0.07–0.24) per 1000 PYs in children without IBD (Table). The 5-year cumulative incidences of VTE, DVT, and PE were significantly higher in children with IBD than in children without IBD (VTE: IRR 21.44, 95% CI 10.73–42.82; DVT: IRR 25.15, 95% CI 11.12–56.89; PE: IRR 4.01, 95% CI 1.22–13.18). Compared to UC patients, children with CD were at lower risk of VTE (IRR 0.53, 95% CI 0.29–0.96) and numerically, but not statistically, lower risk of DVT (IRR 0.59, 95% CI 0.30–1.14).

Conclusions

Although VTEs are relatively rare among children with IBD, these children are at much greater risk than children without IBD. Gastroenterologists caring for these patients should be cognizant of VTE risk and provide appropriate prophylaxis to those at high risk of VTE.

Funding Agencies

CCC

A59 DECREASING HOSPITALIZATIONS AND SURGERIES IN CHILDREN WITH INFLAMMATORY BOWEL DISEASE: A POPULATION-BASED COHORT STUDY

Background

Health services use in inflammatory bowel disease (IBD) patients cost the Canadian healthcare system $1.3 billion per year, but recent changes to care in children with IBD may have altered trends in health services use. Characterization of these trends would aid health policy makers plan for the healthcare needs of IBD children.

Aims

To quantify time trends in IBD health services use in children and all-cause health services use in children with and without IBD using a population-based cohort.

Methods

Using the Ontario Crohn’s and Colitis Cohort, children &lt;18y with IBD diagnosed between 1994–2012 in Ontario were identified using validated algorithms from health administrative data, and matched on age, sex, rurality, and income to children without IBD. We evaluated trends in the number of IBD-specific and all-cause outpatient visits, emergency department (ED) visits, and hospitalizations using negative binomial regression. Cox proportional hazards regression models were used to describe changes in the hazard of intestinal resection (Crohn’s disease; CD) and colectomy (ulcerative colitis; UC) over time. Results are reported as annual percentage change (with 95%CI) for events within 5 years from the diagnosis/index date.

Results

IBD-specific hospitalization rates decreased by 2.5% (95%CI 1.8–3.2%) per year, but all-cause hospitalization rates in children without IBD decreased faster (APC, 95%CI: 4.3%, 3.5–5.1%, difference in rates p-value=0.0028). The hazard of intestinal resection for CD decreased by 6.0% (95%CI 4.6–7.3%) per year and the hazard of colectomy for UC decreased by 3.0% (95%CI 0.7–5.2%) per year. IBD-specific outpatient visit rates increased after 2005 by 4.0% (95%CI 3.1–4.9%) per year. Similar trends were not observed in children without IBD.

Conclusions

Decreasing hazards of intestinal resection and colectomy in children with IBD suggest changes in disease management, including more care being provided on an outpatient basis. Decreased hospitalization rates in IBD were mirrored by similar decreases in non-IBD children, indicating universal care changes. Understanding why these trends are occurring may help us better understand how to provide optimal care to children with IBD.

Funding Agencies

CIHRCanGIEC

First Measurement of Near-Threshold J/ψ Exclusive Photoproduction off the Proton

We report on the measurement of the γp→J/ψp cross section from E_{γ}=11.8  GeV down to the threshold at 8.2 GeV using a tagged photon beam with the GlueX experiment. We find that the total cross section falls toward the threshold less steeply than expected from two-gluon exchange models. The differential cross section dσ/dt has an exponential slope of 1.67±0.39  GeV^{-2} at 10.7 GeV average energy. The LHCb pentaquark candidates P_{c}^{+} can be produced in the s channel of this reaction. We see no evidence for them and set model-dependent upper limits on their branching fractions B(P_{c}^{+}→J/ψp) and cross sections σ(γp→P_{c}^{+})×B(P_{c}^{+}→J/ψp).

Evaluation of a novel immunochromatographic lateral flow assay for rapid detection of OXA-48, NDM, KPC and VIM carbapenemases in multidrug-resistant Enterobacteriaceae

PURPOSE

The global spread and increasing clinical impact of carbapenemase-producing bacteria are alarming. Rapid diagnostic techniques for carbapenemase detection are of the utmost importance to prevent delays in efficient antibiotic therapy and the control of spread in hospitals. Recently, multiplex immunochromatographic lateral flow tests (ICTs) for the fast detection of carbapenemase-producers have become commercially available. We evaluated a novel multiplex ICT for the rapid detection of OXA-48, KPC, NDM and VIM carbapenemases.

METHODOLOGY

One hundred well-characterized multidrug-resistant Enterobacteriaceae were analysed by RESIST-4 (Coris, BioConcept, Gembloux, Belgium). The reference standard included confirmation at the molecular level at the German National Reference Laboratory for multidrug-resistant Gram-negative bacteria (Ruhr-University Bochum, Germany).Results/Key findings. The tested ICT was highly reliable, showing 100 % sensitivity and 100 % specificity.

CONCLUSION

As it is fast, easy to perform and has few technical requirements, the ICT represents a good opportunity to improve turnaround times and patient care for the clinical microbiology laboratory.

Revealing Color Forces with Transverse Polarized Electron Scattering

The Spin Asymmetries of the Nucleon Experiment measured two double spin asymmetries using a polarized proton target and polarized electron beam at two beam energies, 4.7 and 5.9 GeV. A large-acceptance open-configuration detector package identified scattered electrons at 40° and covered a wide range in Bjorken x (0.3<x<0.8). Proportional to an average color Lorentz force, the twist-3 matrix element, d[over ˜]_{2}^{p}, was extracted from the measured asymmetries at Q^{2} values ranging from 2.0 to 6.0  GeV^{2}. The data display the opposite sign compared to most quark models, including the lattice QCD result, and an unexpected scale dependence. Furthermore, when combined with the neutron data in the same Q^{2} range the results suggest a flavor independent average color Lorentz force.

Disease-associated genotypes of the commensal skin bacterium Staphylococcus epidermidis

Some of the most common infectious diseases are caused by bacteria that naturally colonise humans asymptomatically. Combating these opportunistic pathogens requires an understanding of the traits that differentiate infecting strains from harmless relatives. Staphylococcus epidermidis is carried asymptomatically on the skin and mucous membranes of virtually all humans but is a major cause of nosocomial infection associated with invasive procedures. Here we address the underlying evolutionary mechanisms of opportunistic pathogenicity by combining pangenome-wide association studies and laboratory microbiology to compare S. epidermidis from bloodstream and wound infections and asymptomatic carriage. We identify 61 genes containing infection-associated genetic elements (k-mers) that correlate with in vitro variation in known pathogenicity traits (biofilm formation, cell toxicity, interleukin-8 production, methicillin resistance). Horizontal gene transfer spreads these elements, allowing divergent clones to cause infection. Finally, Random Forest model prediction of disease status (carriage vs. infection) identifies pathogenicity elements in 415 S. epidermidis isolates with 80% accuracy, demonstrating the potential for identifying risk genotypes pre-operatively.

Evaluation of the EntericBio CPE assay for the detection of carbapenemase-producing organisms

Carbapenemase-producing organisms (CPOs) represent an increasing threat in healthcare facilities and detection of these organisms in the diagnostic laboratory can be challenging. The EntericBio CPE (EBCPE) real-time PCR assay (Serosep Ltd) was evaluated for the detection of NDM, KPC, OXA-48-like, VIM, IMP and GES carbapenemase genes from a panel of 145 multidrug-resistant organisms (29 NDM, 35 OXA-48, 21 VIM, 4 OXA-23, 3 KPC, 5 NDM+OXA-48, 3 GES-5, 1 OXA-23+NDM, 1 IMI, 2 IMP-1 and 41 multidrug-resistant carbapenemase-negative isolates). The EBCPE assay performed well, with 100 % sensitivity and specificity for the detection of all genotypes included in the assay. Turnaround time and laboratory workflow were improved compared to culture-based assays. Users must remain aware of the limitations of molecular assays for CPO detection to ensure implementation of the most suitable CPO diagnostic pathways.

Comparison of two commercial carbapenemase gene confirmatory assays in multiresistant Enterobacteriaceae and Acinetobacter baumannii-complex

Multidrug-resistant Gram-negative bacilli (MDR-GNB) producing carbapenemases are increasing at an alarming speed. Rapid confirmation of carbapenemase type will be an important diagnostic step in clinical microbiology laboratories not only to reduce the risk of transmissions but also for optimising antibiotic therapy in the future. We compared diagnostic reliability of two commercially available molecular assays (Check-Direct CPE vs. AID line probe assay) for detection and typing of carbapenemase genes in 80 well-characterized isolates of MDR-GNB. Respective strains were isolated in various clinical specimens at our clinical microbiology laboratory. The reference standard included confirmation of carbapenemase-production at the molecular level at the German National Reference Laboratory for Multidrug-resistant Gram-negative bacteria (Ruhr-University Bochum, Germany). 53 Enterobacteriaceae and 27 members of the A. baumannii-complex were used in this study. The tested assays appeared highly reliable to confirm carbapenemase-producing Enterobacteriaceae (CPE) with respective sensitivities of 97.7%, but are currently unsuitable for analysis of members of the A. baumannii-complex. Both assays are easy to perform and rapid tools for confirmation and typing of the most common carbapenemase genes in Enterobacteriaceae. Implementation should be possible for any clinical microbiology laboratory with Check-Direct CPE being easier to handle and having less technological requirements.

Improving the detection of carbapenemase-producing organisms (CPO) in a low-prevalence setting: evaluation of four commercial methods and implementation of an algorithm of testing

PURPOSE

Carbapenemase-producing organisms (CPOs) can be resistant to almost all β-lactams and represent an increasing threat in healthcare facilities. Detection of these organisms in routine diagnostic laboratories is difficult; here we evaluate four commercially available CPO detection assays and assess their suitability for the clinical laboratory.

METHODOLOGY

A panel of 95 clinical multidrug-resistant organisms (22 NDM, 24 OXA-48, 19 VIM, 4 OXA-23, 3 KPC, 4 NDM+OXA-48, 1 OXA23+NDM, 1 IMI, 1 IMP-1, 9 ESBL, 3 derepressed AmpC and 4 inducible AmpC producers) were tested by the RESIST-3 O.K.N., RapidEC CarbaNP, Acuitas Resistome and Xpert Carba-R assays.Results/Key Findings. The commercial assays performed well, with high sensitivities (96.2-100 %) and specificities (all, 100 %). The RapidEC CarbaNP and Acuitas Resistome were able to detect the broadest range of carbapenemase genotypes. The RESIST-3 O.K.N. and Xpert CarbaR had the shortest turnaround times, whilst the RapidEC CarbaNP was the only assay included in this study that could detect previously undescribed genotypes.

CONCLUSION

Using an algorithm of the RapidEC CarbaNP, followed by either the RESIST-3 O.K.N. (Enterobacteriaceae) or the Xpert Carba-R (Pseudomonas aeruginosa and Acinetobacter spp.) on suspect CPOs allowed rapid in-house detection and genotyping of a high proportion of CPOs, reducing turnaround time by up to 7 days.

Rapid Identification of Staphylococci from Prosthetic Joint Infections Using MALDI-TOF Mass-Spectrometry

Hospital-acquired infections associated with implanted medical devices are most commonly caused by staphylococci. Current methods of species identification are slow, costly, and sometimes unreliable. We evaluated the ability of a Bruker Daltonics Microflex MALDI-TOF/MS in conjunction with MALDI Biotyper software to identify 158 characterized staphylococcal isolates from prosthetic joint infections, including 36 Staphylococcus aureus, 100 Staphylococcus epidermidis, 10 Staphylococcus capitis, 8 Staphylococcus lugdunensis, 2 Staphylococcus warneri, and 2 Staphylococcus haemolyticus isolates using the extraction method recommended by Bruker Daltonics. The suggested species identification by the MALDI Biotyper software was correct for all isolates, indicating reliable differentiation between S. aureus and coagulase-negative staphylococci. Applying the recommended criteria of the MALDI Biotyper software all 158 isolates gave scores ≥2.0, implying secure genus and probable species identification for all isolates. 34/36 S. aureus, 36/100 S. epidermidis, 5/10 S. capitis, 6/8 S. lugdunensis, 2/2 S. haemolyticus, 0/2 S. warneri displayed scores ≥2.3 implying highly probable species identification. For S. epidermidis 25/100 additional isolates had a score close to 2.3. It appears that additional clinically relevant staphylococcal isolates in the data base might aid in identification at scores implying highly probable species identification. The ability of the MALDI Biotyper software to recognize clonally-related strains within a species group (i.e. sub-typing) was investigated, and showed great potential. In conclusion, the MALDI-TOF/MS MALDI Biotyper system provides a promising rapid and reliable method of identifying clinical isolates from prosthetic joint infections to the species level, and has potential for sub-typing.

Disruption of Staphylococcus Epidermidis Biofilms by Medicinal Maggot Lucilia Sericata Excretions/Secretions

Chronic infections are commonly associated with biofilms formed by bacteria such as Staphylococcus epidermidis. With the increase in antibiotic resistant bacteria, maggot debridement therapy has been reintroduced for the treatment of chronic wounds. Studies have shown that the excretion/secretions (ES) of Lucilia sericata larvae (maggots) contain many bioactive compounds which may contribute to the efficacy of maggot therapy. The present study evaluates the effect of L. sericata ES on the formation and disruption of S. epidermidis 7457 and 5179-R1 biofilms. These strains employ either polysaccharide intercellular adhesin (PIA) or accumulation associated protein (Aap) for intercellular adhesion.

A semiquantitative biofilm assay was used to measure the formation/disruption of S. epidermidis 7457 and 5179-R1 biofilms by ES. ES activity was characterized according to concentration, incubation time and temperature, thermal stability, and size. Immunofluorescence microscopy was used to ascertain the effect of ES on PIA and Aap.

In the presence of ES, S. epidermidis 7457 and 5179-R1 nascent bio film formation was inhibited, and pre-formed biofilms disrupted. ES activity was temperature and time dependent, inactivated by heat treatment, and disruption depended on the mechanism of intercellular adhesion. The molecule(s) responsible was >10 kDa in size and appeared to have protease or glucosaminidase activity.

ES interferes with S. epidermidis biofilm formation, specifically degrading factors employed in biofilm accumulation, which would increase bacterial susceptibility to antibiotics and the host's immune system. In purified form, ES-factors may have general applicability for the treatment or prevention of chronic biofilm infections caused by staphylococci.

Regulation of Biofilm Formation by σB is a Common Mechanism in Staphylococcus Epidermidis and is not Mediated by Transcriptional Regulation of sarA

Biofilm formation is a major pathogenetic factor of Staphylococcus epidermidis. In S. epidermidis the alternative sigma factor σB was identified to regulate biofilm formation in S. epidermidis 1457. In S. aureus σB dependent regulation plays a minor role, whereas sarA (Staphylococcus accessory regulator) is an essential regulator. Therefore, we investigated the impact of σB on sarA transcription and biofilm formation in three independent S. epidermidis isolates. Mutants with dysfunctional σB displayed a strongly reduced biofilm formation, whereas in mutants with constitutive σB activity bio film formation was increased. Transcriptional analysis revealed that IcaA transcription was down-regulated in all σB negative mutants while icaR transcription was up-regulated. However, transcriptional differences varied between individual strains, indicating that additional σB-dependent regulators are involved in biofilm expression. Interestingly, despite the presence of a σB promoter beside two σA promoters no differences, or only minor ones, were observed in sarA transcription, indicating that σB-dependent sarA transcript has no influence on the phenotypic changes. The data observed in independent clinical S. epidermidis isolates suggests that, in contrast to S. aureus, regulation of biofilm formation by σB is a general feature in S. epidermidis. Additionally, we were able to demonstrate that the sarA- dependent regulation is not involved in this regulatory pathway.

Biofilm Formation is not Necessary for Development of Quinolone-Resistant “Persister” cells in an Attached Staphylococcus Epidermidis Population

Staphylococcus epidermidis is a common pathogen in device-associated infections which is able to attach onto polymeric surfaces and develop multilayered biofilms. Attached S. epidermidis displays reduced susceptibility to antimicrobial agents. In this study we investigated the influence of ciprofloxacin and the group IV quinolones gatifloxacin, gemifloxacin, and moxifloxacin with the minimal attachment killing (MAK) assay. MAK concentrations were determined for three biofilm-positive wild-type strains and their isogenic biofilm-negative mutants Depending on strain and investigated quinolone, it was possible to distinguish between a heterogeneous MAK (MAKhetero), and a homogeneous resistance (MAKhomo) which corresponds to the model of a few persisting cells under antibiotic treatment. A lower MAKhomo was detected for the biofilm-negative mutants as well as for the corresponding wild-types for some of the tested quinolones, which seems to be a result of higher bacterial inocula, whereas the MAKhetero concentrations were comparable for mutants and wild-types for nearly all of the tested antibiotics and strains. These data indicate that biofilm formation is not necessary for persistence of attached S. epidermidis cells under treatment with quinolones and could explain therapeutic failure in foreign body-associated infections due to biofilm-negative S. epidermidis isolates. The individual resistance phenotypes of investigated strains indicate that the determination of MAK concentrations might help to predict the therapy outcome of foreign body-associated infections with both biofilm-positive and biofilm-negative S. epidermidis. Thus, the relatively high activity displayed by group IV quinolones against individual attached staphylococcal isolates indicates a possible treatment option with the respective quinolones for foreign body-associated infections due to these isolates. (Int J Artif Organs 2008; 31: 752–60)

Limitations in the use of PSMγ, agr, RNAIII, and biofilm formation as biomarkers to define invasive Staphylococcus epidermidis from chronic biomedical device-associated infections

Staphylococcus epidermidis is a common cause of biomedical device-associated infections. Agr is the major quorum sensing system in staphylococci and regulates virulence factors. Four agr-specificity groups exist in S. epidermidis, and chronic S. epidermidis infections are hypothesised to select for agr-negative phenotypes. Therefore, we investigated S. epidermidis strains from prosthetic joint- and catheter-associated infections to establish i) whether an infection selects for an agr-negative phenotype; ii) the importance of PSMγ and iii) if the agr-specificity group is infection dependent. S. epidermidis nasal isolates from healthy volunteers were used as controls. The distribution of agr-specificity groups was significantly different between infection and control episodes, but did not distinguish between the infection types. PSMγ secretion was used to determine agr-activity and HPLC analysis showed that 44% of prosthetic and 32% of catheter-associated episodes produced no PSMγ in comparison to 8% of the control strains. However, PSMγ expression did not always correlate with RNAIII up-regulation, indicating that PSMγ synthesis is likely influenced by additional post-transcriptional control. The data suggests chronic S. epidermidis infections favour agr-specificity group 1 but the results suggest that they do not select for an agr-negative phenotype. Further studies are required to explore the mechanisms underlying the selection and survival of these S. epidermidis phenotypes isolated from biomedical device-associated infections.

Recombination-Mediated Host Adaptation by Avian Staphylococcus aureus

Staphylococcus aureus are globally disseminated among farmed chickens causing skeletal muscle infections, dermatitis, and septicaemia. The emergence of poultry-associated lineages has involved zoonotic transmission from humans to chickens but questions remain about the specific adaptations that promote proliferation of chicken pathogens. We characterized genetic variation in a population of genome-sequenced S. aureus isolates of poultry and human origin. Genealogical analysis identified a dominant poultry-associated sequence cluster within the CC5 clonal complex. Poultry and human CC5 isolates were significantly distinct from each other and more recombination events were detected in the poultry isolates. We identified 44 recombination events in 33 genes along the branch extending to the poultry-specific CC5 cluster, and 47 genes were found more often in CC5 poultry isolates compared with those from humans. Many of these gene sequences were common in chicken isolates from other clonal complexes suggesting horizontal gene transfer among poultry associated lineages. Consistent with functional predictions for putative poultry-associated genes, poultry isolates showed enhanced growth at 42 °C and greater erythrocyte lysis on chicken blood agar in comparison with human isolates. By combining phenotype information with evolutionary analyses of staphylococcal genomes, we provide evidence of adaptation, following a human-to-poultry host transition. This has important implications for the emergence and dissemination of new pathogenic clones associated with modern agriculture.

Complicated sea urchin-induced wound infection caused by Vibrioalginolyticus and Staphylococcus lugdunensis in a 14-year-old boy

INTRODUCTION

Wound infections with Vibrio alginolyticus, a Gram-negative bacterium found in all temperate oceans, are rarely reported. However, a rising incidence of wound infections caused by V. alginolyticus requires better knowledge about this infectious agent.

CASE PRESENTATION

We report the case of a 14-year-old boy suffering from a wound infection caused by V. alginolyticus and Staphylococcus lugdunensis after stepping on a sea urchin. Despite wound debridement and antibiotic therapy with cefaclor, the lesion did not heal over several weeks. After identification of the pathogens and antibiotic-susceptibility testing, antibiotic therapy was switched to ciprofloxacin, followed by trimethoprim/sulfamethoxazole. Two months after the accident the wound was re-epithelialized. Follow up after 6 months revealed a painful scar.

CONCLUSION

Non-cholera vibrios like V. alginolyticus should be considered as possible causative agents in seawater-contaminated wounds. S. lugdunensis is a relevant pathogen in mixed wound infections. Early microbiological diagnosis and antibiotic-susceptibility testing is crucial to prevent therapeutic failure.

Biofilm Morphotypes and Population Structure among Staphylococcus epidermidis from Commensal and Clinical Samples

Bacterial species comprise related genotypes that can display divergent phenotypes with important clinical implications. Staphylococcus epidermidis is a common cause of nosocomial infections and, critical to its pathogenesis, is its ability to adhere and form biofilms on surfaces, thereby moderating the effect of the host’s immune response and antibiotics. Commensal S. epidermidis populations are thought to differ from those associated with disease in factors involved in adhesion and biofilm accumulation. We quantified the differences in biofilm formation in 98 S. epidermidis isolates from various sources, and investigated population structure based on ribosomal multilocus typing (rMLST) and the presence/absence of genes involved in adhesion and biofilm formation. All isolates were able to adhere and form biofilms in in vitro growth assays and confocal microscopy allowed classification into 5 biofilm morphotypes based on their thickness, biovolume and roughness. Phylogenetic reconstruction grouped isolates into three separate clades, with the isolates in the main disease associated clade displaying diversity in morphotype. Of the biofilm morphology characteristics, only biofilm thickness had a significant association with clade distribution. The distribution of some known adhesion-associated genes (aap and sesE) among isolates showed a significant association with the species clonal frame. These data challenge the assumption that biofilm-associated genes, such as those on the ica operon, are genetic markers for less invasive S. epidermidis isolates, and suggest that phenotypic characteristics, such as adhesion and biofilm formation, are not fixed by clonal descent but are influenced by the presence of various genes that are mobile among lineages.

Polarization Transfer in Wide-Angle Compton Scattering and Single-Pion Photoproduction from the Proton

Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The wide-angle Compton scattering polarization transfer was analyzed at an incident photon energy of 3.7 GeV at a proton scattering angle of θ_{cm}^{p}=70°. The longitudinal transfer K_{LL}, measured to be 0.645±0.059±0.048, where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. However, the observed value is ~3 times larger than predicted by the generalized-parton-distribution-based calculations, which indicates a significant unknown contribution to the scattering amplitude.

Effects of polysaccharide intercellular adhesin (PIA) in an ex vivo model of whole blood killing and in prosthetic joint infection (PJI): A role for C5a

BACKGROUND

A major complication of using medical devices is the development of biofilm-associated infection caused by Staphylococcus epidermidis where polysaccharide intercellular adhesin (PIA) is a major mechanism of biofilm accumulation. PIA affects innate and humoral immunity in isolated cells and animal models. Few studies have examined these effects in prosthetic joint infection (PJI).

METHODS

This study used ex vivo whole blood modelling in controls together with matched-serum and staphylococcal isolates from patients with PJI.

RESULTS

Whole blood killing of PIA positive S. epidermidis and its isogenic negative mutant was identical. Differences were unmasked in immunosuppressed whole blood pre-treated with dexamethasone where PIA positive bacteria showed a more resistant phenotype. PIA expression was identified in three unique patterns associated with bacteria and leukocytes, implicating a soluble form of PIA. Purified PIA reduced whole blood killing while increasing C5a levels. In clinically relevant staphylococcal isolates and serum samples from PJI patients; firstly complement C5a was increased 3-fold compared to controls; secondly, the C5a levels were significantly higher in serum from PJI patients whose isolates preferentially formed PIA-associated biofilms.

CONCLUSIONS

These data demonstrate for the first time that the biological effects of PIA are mediated through C5a in patients with PJI.

Ecological Overlap and Horizontal Gene Transfer in Staphylococcus aureus and Staphylococcus epidermidis

The opportunistic pathogens Staphylococcus aureus and Staphylococcus epidermidis represent major causes of severe nosocomial infection, and are associated with high levels of mortality and morbidity worldwide. These species are both common commensals on the human skin and in the nasal pharynx, but are genetically distinct, differing at 24% average nucleotide divergence in 1,478 core genes. To better understand the genome dynamics of these ecologically similar staphylococcal species, we carried out a comparative analysis of 324 S. aureus and S. epidermidis genomes, including 83 novel S. epidermidis sequences. A reference pan-genome approach and whole genome multilocus-sequence typing revealed that around half of the genome was shared between the species. Based on a BratNextGen analysis, homologous recombination was found to have impacted on 40% of the core genes in S. epidermidis, but on only 24% of the core genes in S. aureus. Homologous recombination between the species is rare, with a maximum of nine gene alleles shared between any two S. epidermidis and S. aureus isolates. In contrast, there was considerable interspecies admixture of mobile elements, in particular genes associated with the SaPIn1 pathogenicity island, metal detoxification, and the methicillin-resistance island SCCmec. Our data and analysis provide a context for considering the nature of recombinational boundaries between S. aureus and S. epidermidis and, the selective forces that influence realized recombination between these species.

Structural basis of Staphylococcus epidermidis biofilm formation: mechanisms and molecular interactions

Staphylococcus epidermidis is a usually harmless commensal bacterium highly abundant on the human skin. Under defined predisposing conditions, most importantly implantation of a medical device, S. epidermidis, however, can switch from a colonizing to an invasive life style. The emergence of S. epidermidis as an opportunistic pathogen is closely linked to the biofilm forming capability of the species. During the past decades, tremendous advance regarding our understanding of molecular mechanisms contributing to surface colonization has been made, and detailed information is available for several factors active during the primary attachment, accumulative or dispersal phase of biofilm formation. A picture evolved in which distinct factors, though appearing to be redundantly organized, take over specific and exclusive functions during biofilm development. In this review, these mechanisms are described in molecular detail, with a highlight on recent insights into multi-functional S. epidermidis cell surface proteins contributing to surface adherence and intercellular adhesion. The integration of distinct biofilm-promoting factors into regulatory networks is summarized, with an emphasis on mechanism that could allow S. epidermidis to flexibly adapt to changing environmental conditions present during colonizing or invasive life-styles.

A high-dose preparation of lactobacilli and bifidobacteria in the prevention of antibiotic-associated and Clostridium difficile diarrhoea in older people admitted to hospital: a multicentre, randomised, double-blind, placebo-controlled, parallel arm trial (PLACIDE)

BACKGROUND

Antibiotic-associated diarrhoea (AAD) occurs most commonly in older people admitted to hospital and within 12 weeks of exposure to broad-spectrum antibiotics. Although usually a mild and self-limiting illness, the 15-39% of cases caused by Clostridium difficile infection [C. difficile diarrhoea (CDD)] may result in severe diarrhoea and death. Previous research has shown that probiotics, live microbial organisms that, when administered in adequate numbers, are beneficial to health, may be effective in preventing AAD and CDD.

OBJECTIVES

To determine the clinical effectiveness and cost-effectiveness of a high-dose, multistrain probiotic in the prevention of AAD and CDD in older people admitted to hospital.

DESIGN

A multicentre, randomised, double-blind, placebo-controlled, parallel-arm trial.

SETTING

Medical, surgical and elderly care inpatient wards in five NHS hospitals in the UK.

PARTICIPANTS

Eligible patients were aged ≥ 65 years, were exposed to one or more oral or parenteral antibiotics and were without pre-existing diarrhoeal disorders, recent CDD or at risk of probiotic adverse effects. Out of 17,420 patients screened, 2981 (17.1%) were recruited. Participants were allocated sequentially according to a computer-generated random allocation sequence; 1493 (50.1%) were allocated to the probiotic and 1488 (49.9%) to the placebo arm.

INTERVENTIONS

Vegetarian capsules containing two strains of lactobacilli and two strains of bifidobacteria (a total of 6 × 10(10) organisms per day) were taken daily for 21 days. The placebo was inert maltodextrin powder in identical capsules.

MAIN OUTCOME MEASURES

The occurrence of AAD within 8 weeks and CDD within 12 weeks of recruitment was determined by participant follow-up and checking hospital laboratory records by research nurses who were blind to arm allocation.

RESULTS

Analysis based on the treatment allocated included 2941 (98.7%) participants. Potential risk factors for AAD at baseline were similar in the two study arms. Frequency of AAD (including CDD) was similar in the probiotic (159/1470, 10.8%) and placebo arms [153/1471, 10.4%; relative risk (RR) 1.04; 95% confidence interval (CI) 0.84 to 1.28; p = 0.71]. CDD was an uncommon cause of AAD and occurred in 12/1470 (0.8%) participants in the probiotic and 17/1471 (1.2%) in the placebo arm (RR 0.71; 95% CI 0.34 to 1.47; p = 0.35). Duration and severity of diarrhoea, common gastrointestinal symptoms, serious adverse events and quality of life measures were also similar in the two arms. Total health-care costs per patient did not differ significantly between the probiotic (£8020; 95% CI £7620 to £8420) and placebo (£8010; 95% CI £7600 to £8420) arms.

CONCLUSION

We found no evidence that probiotic administration was effective in preventing AAD. Although there was a trend towards reduced CDD in the probiotic arm, on balance, the administration of this probiotic seems unlikely to benefit older patients exposed to antibiotics. A better understanding of the pathogenesis of AAD and CDD and the strain-specific effects of probiotics is needed before further clinical trials of specific microbial preparations are undertaken. Evaluation of the effectiveness of other probiotics will be difficult where other measures, such as antibiotic stewardship, have reduced CDD rates.

TRIAL REGISTRATION

This trial is registered as ISRCTN70017204.

FUNDING

This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 17, No. 57. See the NIHR Journals Library website for further project information.

The Yersinia pestis HmsCDE regulatory system is essential for blockage of the oriental rat flea (Xenopsylla cheopis), a classic plague vector

The second messenger molecule cyclic diguanylate is essential for Yersinia pestis biofilm formation that is important for blockage-dependent plague transmission from fleas to mammals. Two diguanylate cyclases (DGCs) HmsT and Y3730 (HmsD) are responsible for biofilm formation in vitro and biofilm-dependent blockage in the oriental rat flea Xenopsylla cheopis respectively. Here, we have identified a tripartite signalling system encoded by the y3729-y3731 operon that is responsible for regulation of biofilm formation in different environments. We present genetic evidence that a putative inner membrane-anchored protein with a large periplasmic domain Y3729 (HmsC) inhibits HmsD DGC activity in vitro while an outer membrane Pal-like putative lipoprotein Y3731 (HmsE) counteracts HmsC to activate HmsD in the gut of X. cheopis. We propose that HmsE is a critical element in the transduction of environmental signal(s) required for HmsD-dependent biofilm formation.

Dormant cells of Staphylococcus aureus are resuscitated by spent culture supernatant

We describe the first in vitro model of dormancy in Staphylococcus aureus, showing that cells are generated which can be resuscitated by addition of spent medium supernatant taken from cultures of the same organism. Over 30 days, culturable counts in dormant cultures of S. aureus SH1000 fell from 10(6)-10(7) cfu/ml to <10 cfu/ml as measured by the Most Probable Number method in liquid culture, while total counts as determined by microscopy, and supported by data from RT-qPCR, remained around 10(6)-10(7) cells/ml. Supplementing cultures with 25-50% spent medium resulted in a >600-fold increase in bacterial growth. Resuscitation was a specific effect, greatly reduced by boiling or addition of trypsin to the spent supernatant. Supernatant also effected a reduction in lag phase of dormant cultures. SEM demonstrated the presence of small coccoid cells in dormant cultures. The results are similar to those seen with resuscitation promoting factors (Rpfs) in actinobacteria. This is the first time resuscitation has been demonstrated in Staphylococcus aureus, which is an important human pathogen. A better understanding of control and reactivation of dormant cells could lead to major improvements in managing staphylococcal infections; resuscitation could be an important step in restoring susceptibility to antibiotic treatment.