Development and validation of a chemostat gut model to study both planktonic and biofilm modes of growth of Clostridium difficile and human microbiota

Copyright: 2014 Crowther et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.The human gastrointestinal tract harbours a complex microbial community which exist in planktonic and sessile form. The degree to which composition and function of faecal and mucosal microbiota differ remains unclear. We describe the development and characterisation of an in vitro human gut model, which can be used to facilitate the formation and longitudinal analysis of mature mixed species biofilms. This enables the investigation of the role of biofilms in Clostridium difficile infection (CDI). A well established and validated human gut model of simulated CDI was adapted to incorporate glass rods that create a solid-gaseous-liquid interface for biofilm formation. The continuous chemostat model was inoculated with a pooled human faecal emulsion and controlled to mimic colonic conditions in vivo. Planktonic and sessile bacterial populations were enumerated for up to 46 days. Biofilm consistently formed macroscopic structures on all glass rods over extended periods of time, providing a framework to sample and analyse biofilm structures independently. Whilst variation in biofilm biomass is evident between rods, populations of sessile bacterial groups (log10 cfu/g of biofilm) remain relatively consistent between rods at each sampling point. All bacterial groups enumerated within the planktonic communities were also present within biofilm structures. The planktonic mode of growth of C. difficile and gut microbiota closely reflected observations within the original gut model. However, distinct differences were observed in the behaviour of sessile and planktonic C. difficile populations, with C. difficile spores preferentially persisting within biofilm structures. The redesigned biofilm chemostat model has been validated for reproducible and consistent formation of mixed species intestinal biofilms. This model can be utilised for the analysis of sessile mixed species communities longitudinally, potentially providing information of the role of biofilms in CDI.Peer reviewe

Graphene matrices as carriers for metal ions against antibiotic susceptible and resistant bacterial pathogens

Due to the ever-increasing burden of antimicrobial-resistant (AMR) bacteria, the development of novel antimicrobial agents and biomaterials to act as carriers and/or potentiate antimicrobial activity is essential. This study assessed the antimicrobial efficacy of the following ionic metals, silver, gold, palladium, platinum, zinc, and gallium alone and in combination with graphene matrices (which were coated via a drop casting coating method). The graphene foam was utilized as a carrier for the ionic metals against both, antibiotic susceptible and resistant bacterial strains of Acinetobac-ter baumannii, Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa. Ionic gold, palladium and platinum demonstrated the greatest antimicrobial activity against the susceptible and resistant strains. Scanning electron microscopy (SEM) visualized cellular ultrastructure damage, when the bacteria were incubated upon the graphene foam alone. This study suggests that specific metal ions applied in combination with graphene foam could present a potential therapeutic option to treat AMR bacterial infections. The application of the graphene foam as a potential carrier could promote antimicrobial activity, provide a sustained release approach and reduce possible resistance acquisition. In light of this study, the graphene foam and ionic metal combinations could potentially be further developed as part of a wound dressing

Association of Fidaxomicin with C. difficile spores: Effects of Persistence on Subsequent Spore Recovery, Outgrowth and Toxin Production.

Background: We have previously shown that fidaxomicin instillation prevents spore recovery in an in-vitro gut model, whereas vancomycin does not. The reasons for this are unclear. Here, we have investigated persistence of fidaxomicin and vancomycin on C. difficile spores, and examined post-antibiotic exposure spore recovery, outgrowth and toxin production. Methods: Prevalent UK C. difficile ribotypes (n=10) were incubated with 200mg/L fidaxomicin, vancomycin or a non-antimicrobial containing control for 1 h in faecal filtrate or Phosphate Buffered Saline. Spores were washed three times with faecal filtrate or phosphate buffered saline, and residual spore-associated antimicrobial activity was determined by bioassay. For three ribotypes (027, 078, 015), antimicrobial-exposed, faecal filtrate-washed spores and controls were inoculated into broth. Viable vegetative and spore counts were enumerated on CCEYL agar. Percentage phase bright spores, phase dark spores and vegetative cells were enumerated by phase contrast microscopy at 0, 3, 6, 24 and 48 h post-inoculation. Toxin levels (24 and 48h) were determined by cell cytotoxicity assay. Results: Fidaxomicin, but not vancomycin persisted on spores of all ribotypes following washing in saline (mean=10.1mg/L; range= 4.0-14mg/L) and faecal filtrate (mean =17.4mg/L; 8.4-22.1mg/L). Outgrowth and proliferation rates of vancomycin-exposed spores were similar to controls, whereas fidaxomicin-exposed spores showed no vegetative cell growth after 24 and 48 h. At 48h, toxin levels averaged 3.7 and 3.3 relative units (RU) in control and vancomycin-exposed samples, respectively, but were undetectable in fidaxomicin-exposed samples. Conclusion: Fidaxomicin persists on C. difficile spores, whereas vancomycin does not. This persistence prevents subsequent growth and toxin production in vitro. This may have implications on spore viability, thereby impacting CDI recurrence and transmission rates

Iliotibial band release as an adjunct to the surgical management of patellar stress fracture in the athlete: a case report and review of the literature

Stress fracture of the patella is rare. In this report, a case of patellar stress fracture occurring in an amateur athlete is presented, and an operative adjunct to the surgical management of this condition is proposed

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

X-Shooting ULLYSES: Massive stars at low metallicity: I. Project description

Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational wave events involving spectacular black hole mergers indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity (Z). The Hubble Space Telescope has devoted 500 orbits to observing ∼250 massive stars at low Z in the ultraviolet (UV) with the COS and STIS spectrographs under the ULLYSES programme. The complementary X-Shooting ULLYSES (XShootU) project provides an enhanced legacy value with high-quality optical and near-infrared spectra obtained with the wide-wavelength coverage X-shooter spectrograph at ESOa's Very Large Telescope. We present an overview of the XShootU project, showing that combining ULLYSES UV and XShootU optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity, luminosity, and abundances, as well as wind properties such as mass-loss rates as a function of Z. As uncertainties in stellar and wind parameters percolate into many adjacent areas of astrophysics, the data and modelling of the XShootU project is expected to be a game changer for our physical understanding of massive stars at low Z. To be able to confidently interpret James Webb Space Telescope spectra of the first stellar generations, the individual spectra of low-Z stars need to be understood, which is exactly where XShootU can deliver

Cross-cutting principles for planetary health education

Since the 2015 launch of the Rockefeller Foundation Lancet Commission on planetary health,1 an enormous groundswell of interest in planetary health education has emerged across many disciplines, institutions, and geographical regions. Advancing these global efforts in planetary health education will equip the next generation of scholars to address crucial questions in this emerging field and support the development of a community of practice. To provide a foundation for the growing interest and efforts in this field, the Planetary Health Alliance has facilitated the first attempt to create a set of principles for planetary health education that intersect education at all levels, across all scales, and in all regions of the world—ie, a set of cross-cutting principles

Exploring the views of being a proxy from the perspective of unpaid carers and paid carers: developing a proxy version of the Adult Social Care Outcomes Toolkit (ASCOT)

Background: Outcomes-based policy and administration of public services present a compelling argument for the value of outcomes data. However, there are a number of challenges inherent in collecting these data from people who are unable to complete a paper-based survey or interview due to cognitive or communication impairments. In this paper, we explore the views of being a proxy from the perspective of unpaid carers and paid carers who may be asked to act as a proxy on behalf of the person(s) they care for. We consider the key issues that need to be addressed when adapting an instrument designed to measure social care outcomes, the Adult Social Care Outcomes Tool (ASCOT), into a proxy-report tool. Methods: Participants took part in either a focus group (35 paid carers in eight focus groups), or a one-to-one interview (eight unpaid carers). All participants were recruited via carer organisations and care providers. Transcripts, field notes and audio data collected during focus groups and interviews were analysed using a thematic framework approach. Results: Participants agreed that any person acting as a proxy would need to be very familiar with the care recipient, as well as their needs and care provision. A number of provisions for proxy respondents were proposed to improve face validity and acceptability of completing a questionnaire by proxy, and to ensure that any potential bias is reduced in the design of the questionnaire. These included: providing two sets of response options for each proxy perspective (the proxy themselves and the proxy view of how they think the care recipient would respond); a comments box to help people explain why they have selected a given response option (especially where these indicate unmet need); and providing clear guidance for the proxy respondent on how they should complete the questionnaire. Conclusions: This study has shown some of the challenges involved in assessing outcomes by proxy and explored some potential ways these can be mitigated. The findings highlight the benefits of developing and testing proxy measures in a robust way to widen participation in social care research

Adapting the adult social care outcomes toolkit (ASCOT) for use in care home quality monitoring: conceptual development and testing

Background: Alongside an increased policy and practice emphasis on outcomes in social care, English local authorities are now obliged to review quality at a service level to help in their new role of ensuring the development of diverse and high-quality care markets to meet the needs of all local people, including self-funders. The Adult Social Care Outcomes Toolkit (ASCOT) has been developed to measure the outcomes of social care for individuals in a variety of care settings. Local authorities have expressed an interest in exploring how the toolkit might be used for their own purposes, including quality monitoring. This study aimed to explore how the care homes version of the ASCOT toolkit might be adapted for use as a care home quality indicator and carry out some preliminary testing in two care homes for older adults. Methods: Consultations were carried out with professional and lay stakeholders, with an interest in using the tool or the ratings it would produce. These explored demand and potential uses for the measure and fed into the conceptual development. A draft toolkit and method for collecting the data was developed and the feasibility of using it for quality monitoring was tested with one local authority quality monitoring team in two homes for older adults. Results: Stakeholders expressed an interest in care home quality ratings based on residents’ outcomes but there were tensions around who might collect the data and how it might be shared. Feasibility testing suggested the measure had potential for use in quality monitoring but highlighted the importance of training in observational techniques and interviewing skills. The quality monitoring officers involved in the piloting recommended that relatives’ views be collected in advance of visits, through surveys not interviews. Conclusions: Following interest from another local authority, a larger evaluation of the measure for use in routine quality monitoring is planned. As part of this, the ratings made using this measure will be validated against the outcomes of individual residents and compared with the quality ratings of the regulator, the Care Quality Commission

Evaluation of antimicrobial activity of ceftaroline against Clostridium difficile and propensity to induce C. difficile infection in an in vitro human gut model

OBJECTIVES: To examine the effects of exposure to ceftaroline or ceftriaxone on the epidemic Clostridium difficile strain PCR ribotype 027 and the indigenous gut microflora in an in vitro human gut model. Additionally, the MICs of ceftriaxone and ceftaroline for 60 C. difficile isolates were determined. METHODS: Two triple-stage chemostat gut models were primed with human faeces and exposed to ceftaroline (10 mg/L, twice daily, 7 days) or ceftriaxone (150 mg/L, once daily, 7 days). Populations of indigenous gut microorganisms, C. difficile total viable counts, spore counts, cytotoxin titres and antimicrobial concentrations were monitored throughout. MICs were determined by a standard agar incorporation method. RESULTS: In the gut model, both ceftaroline and ceftriaxone induced C. difficile spore germination, proliferation and toxin production, although germination occurred 5 days later in the ceftaroline-exposed model. Toxin detection was sustained until the end of the experimental period in both models. No active antimicrobial was detected in vessel 3 of either model, although inhibitory effects on microflora populations were observed. Ceftaroline was ∼8-fold more active against C. difficile than ceftriaxone (geometric mean MICs, 3.38 versus 28.18 mg/L; MIC90s, 4 versus 64 mg/L; and MIC ranges, 0.125-16 versus 8-128 mg/L). CONCLUSIONS: Ceftaroline, like ceftriaxone, can induce simulated C. difficile infection in a human gut model. However, low in vivo gut concentrations of ceftaroline and increased activity against C. difficile in comparison with ceftriaxone mean that the true propensity of this novel cephalosporin to induce C. difficile infection remains unclear.Peer reviewe