Resolving the Nutritional Requirements of the Bile Acid-Dehydroxylating Gut Bacterium Clostridium scindens

Compared to the other parts of the human body, the gastrointestinal tract harbors a complex microbiota. The impact of the indigenous microbiota on host physiology is most pronounced in the colon, where the primary bile acids chenodeoxycholic acid and cholic acid are converted, via 7α-dehydroxylation, to the toxic secondary bile acids lithocholic acid and deoxycholic acid, respectively, by Clostridium scindens, an obligate anaerobe. Interestingly, other than bile acid dehydroxylation, little is known about the basic physiology of C. scindens. Understanding the metabolism of C. scindens will hopefully provide much-needed information as to how this gut bacterium impacts human health and disease. The goals of our study were to determine the vitamin and amino acid requirements of C. scindens and also to determine if C. scindens can convert primary bile acid cholic acid to secondary bile acid deoxycholic acid via 7α-dehydroxylation under defined culture conditions. C. scindens VPI 12708 was routinely maintained in anaerobic BHI broth medium at 37°C. When C. scindens was transferred from the BHI medium to a defined medium (DM; 25 mM glucose, minerals, metals, bicarbonate, 100% CO2 gas phase, and cysteine), growth was negligible. Only when DM was supplemented with a vitamin mix (p-aminobenzoate, biotin, cyanocobalamin, folate, lipoate, nicotinate, pantothenate, pyridoxal, riboflavin, and thiamine) and an amino acid mix (alanine, arginine, asparagine, aspartate, cystine, glutamate, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine) was growth observed. The leave-one-out technique was subsequently used to determine the specific vitamin(s) and amino acid(s) required for growth. With this technique, two vitamins (riboflavin and pantothenate) and one amino acid (tryptophan) were found to be essential for the growth of C. scindens. Growth was also reduced, but not inhibited when pyridoxal or biotin was absent from OM. It was also observed that under defined culture conditions C. scindens was able to convert cholic acid to deoxycholic acid via 7α-dehydroxylation while producing two unknown products

In situ and ex situ bioremediation of heavy metals: the present scenario

Enhanced population growth, rapid industrialization, urbanization and hazardous industrial practices have resulted in the development of environmental pollution in the past few decades. Heavy metals are one of those pollutants that are related to environmental and public health concerns based on their toxicity. Effective bioremediation may be accomplished through “ex situ” and “in situ” processes, based on the type and concentration of pollutants, characteristics of the site but is not limited to cost. The recent developments in artificial neural network and microbial gene editing help to improve “in situ” bioremediation of heavy metals from the polluted sites. Multi-omics approaches are adopted for the effective removal of heavy metals by various indigenous microbes. This overview introspects two major bioremediation techniques, their principles, limitations and advantages, and the new aspects of nanobiotechnology, computational biology and DNA technology to improve the scenario

"I decide myself"- A qualitative exploration of end of life decision making processes of patients and caregivers through Advance Care Planning

Background The Singapore national Advance Care Planning (ACP) programme was launched in 2011 with the purpose of ensuring that healthcare professionals are fully aware of patients’ treatment preferences. There is little research assessing the performance of such programmes in ethnically diverse Asian countries; hence, the purpose of this study was to qualitatively examine patients and caregivers’ experiences with the ACP programme. Method We conducted interviews with 28 participants, thirteen of whom identified as proxy decision makers (PDMs) and the remainder as patients. Interviews focused on respondents’ experiences of chronic illness and of participating in the ACP programme. Textual data was analysed through a framework analysis approach. Results Participants’ narratives focused on four major themes with 12 subthemes: a) Engagement with Death, factors influencing respondents’ acceptance of ACP; b) Formation of Preferences, the set of concerns influencing respondents’ choice of care; c) Choice of PDM, considerations shaping respondents’ choice of nominated health spokesperson; and d) Legacy Solidification, how ACP is used to ensure the welfare of the family after the patient passes. These findings led to our development of the directive decision-making process framework, which delineates personal and sociocultural factors influencing participants’ decision-making processes. Respondents’ continual participation in the intervention were driven by their personal belief system that acted as a lens through which they interpreted religious doctrine and socio-cultural norms according to their particular needs. Conclusion The directive decision-making process framework indicated that ACP could be appropriate for the Asian context because participants displayed an awareness of the need for ACP and were able to develop a concrete treatment plan. Patients in this study made decisions based on their perceived long-term legacy for their family, who they hoped to provide with a solid financial and psychological foundation after their death

Stress Response Mechanisms of \u3ci\u3eListeria monocytogenes\u3c/i\u3e

Listeria monocytogenes is a Gram-positive, facultative intracellular food-borne pathogen that causes the disease listeriosis. In order to establish an infection, L. monocytogenes must survive multiple stressors encountered within the gastrointestinal tract, including alterations in pH, bile, salt, and oxygen availability. This dissertation focused on understanding the stress response of L. monocytogenes to bile. Bile acts as a bactericidal agent by disrupting the membrane integrity and causing instability to macromolecules like DNA. Thus, a bacterium must be able to maintain its membrane architecture, composition and integrity. Often times, bacteria will modulate their fatty acid composition in the membrane to cope with environmental changes. Our research through fatty acid methyl ester analyses showed that the fatty acid composition of the cell membrane of L. monocytogenes was altered after exposure to bile, suggesting that L. monocytogenes incorporates exogenous fatty acids from bile. Additionally, incorporation of exogenous fatty acids was subsequently found to increase bile survival in the bile sensitive strain HCC23 under aerobic conditions whereas improved the survival of the moderately bile resistant strain, 10403s under anaerobic conditions. Thus, suggesting oxygen availability plays a role in influencing survival. The incorporation of fatty acids was also found to increase the fluidity of the cell membrane following exposure to bile. Together, these data indicate that bile sensitive strains of L. monocytogenes may incorporate exogenous fatty acids from the host into their cell membrane as an attempt to survive membrane damage, such as that induced by bile but in turn lose intestinal fitness. It is known that bile causes oxidative damage to bacterial cells. However, it is not known if oxidative stress occurs under physiologically relevant anaerobic conditions. Our results showed that bile exposure alters the redox potential of L. monocytogenes by increasing the membrane potential for the bile resistant strain F2365 and by reducing the NADH:NAD+ in F2365 and 10403S under anaerobic conditions. Though the decrease in NADH:NAD+ may suggest an oxidative environment, no signs of oxidative stress were observed as there was lack of lipid and protein oxidation under anaerobic conditions. This data correlates with our previous proteomics data. Further research is needed to understand the kind of damage induced by bile in Listeria monocytogenes under anaerobic conditions. Bile is also known to cause DNA damage. We wanted to see if L. monocytogenes’ ability to repair bile induced DNA damage is what aids in bile resistance. Since recA is the inducer of SOS response, we analyzed the expression of various DNA repair and bile resistant genes in the L. monocytogenes strain, EGD-e and the mutant of EGDe lacking recA. We also analyzed the ability of EGD-e and the recA mutant to survive bile stress under aerobic and anaerobic conditions. Our research suggests that there may be a recA independent DNA repair mechanism involved in the bile induced DNA repair in L. monocytogenes strain EGD-e

Reciprocal dynamics of dignity in end-of-life care : a multiperspective systematic review of qualitative and mixed methods research

Background: Preserving terminally ill patients’ dignity and well-being through dignified and holistic care has become the overarching goal in palliative care services. However, dignity is a multifaceted concept with a wide range of interpretations under different cultural contexts. Aim: The aim of this review is to understand the variations in subjective interpretations and constitutions of dignity in palliative or end-of-life care via an integrative worldview. Design: This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline and used SPIDER tool to screen for appropriate and relevant articles for analysis. Data Sources: Four major databases were searched including CINAHL, ERIC, Medline, and PsycARTICLES between 2009 and 2018. Forty-eight qualitative studies that examined dignity from the perspectives of patients, family caregivers, and health-care professionals were selected for full text data analysis using thematic synthesis. Results: Analysis of the various concepts of dignity revealed 18 themes that were further categorized into 7 conceptual categories: (1) self-determination, (2) existential liberty, (3) relational connectedness, (4) caregiving revitalization, (5) mindful humanity, (6) patient–family care, and (7) sustainable culture. These 7 categories span across individual, familial, and institutional dimensions, forming a new Dynamic Reciprocity of Dignity model. Conclusions: The Dynamic Reciprocity of Dignity model highlights the importance of adopting a systemic lens to address dignity-related needs and concerns at the end of life, while providing insights on how compassionate care and self-compassion can serve as the foundation of dignified care, which in turn serve as a buffer against patients’ existential suffering as well as caregivers’ burnout and fatigue. Recommendations for clinical practice and future research directions are discussed.MOE (Min. of Education, S’pore)Accepted versio

Competing expectations: advance care planning from the perspectives of doctors and nurses in the South-East Asian context

This study qualitatively examines the perspectives of doctors and nurses on the implementation of the Advance Care Planning program in Singapore. Findings suggest that a combination of structural and conceptual factors hindered the performance of ACP. Themes on structural factors indicated that low awareness of ACP among senior staff resulted overall lack of buy-in and incorrect implementation of the program due to misconceptions. Conceptual factors pointed to lack of clarity on intended outcomes or roles. Consequently, participants drew meaning through the prism of their profession, resulting in competing expectations and tensions on possible outcomes of the program

Competing expectations: advance care planning from the perspectives of doctors and nurses in the South-East Asian context

This study qualitatively examines the perspectives of doctors and nurses on the implementation of the Advance Care Planning program in Singapore. Findings suggest that a combination of structural and conceptual factors hindered the performance of ACP. Themes on structural factors indicated that low awareness of ACP among senior staff resulted overall lack of buy-in and incorrect implementation of the program due to misconceptions. Conceptual factors pointed to lack of clarity on intended outcomes or roles. Consequently, participants drew meaning through the prism of their profession, resulting in competing expectations and tensions on possible outcomes of the program.Ministry of Health (MOH)This study was funded by the Agency for Integrated Care Singapore, which received public funding from the Ministry of Health of the Singaporean Government

Oxygen Deprivation Influences the Survival of \u3ci\u3eListeria monocytogenes\u3c/i\u3e in Gerbils

Listeria monocytogenes is a facultative anaerobic foodborne pathogen capable of surviving harsh environments. Recent work has indicated that anaerobic conditions increase the resistance capability of certain strains to environmental stressors. The goal of the study was to conduct a preliminary study to determine whether exposure to anaerobic conditions prior to infection increases the ability to survive in vivo. Gerbils were inoculated with one of five doses of the L. monocytogenes strain F2365 by oral gavage: phosphate-buffered saline (control), 5 × 106 colony forming units aerobic culture (low aerobic), 5 × 108 aerobic culture (high aerobic), 5 × 106 anaerobic culture (low anaerobic), or 5 × 108 anaerobic culture (high anaerobic) dose of F2365. Gerbils inoculated with a high aerobic or anaerobic dose exhibited significant weight loss. Gerbils administered either the low or high anaerobic dose had at least 3 log10 of L. monocytogenes present in fecal samples, which contrasted with gerbils that received the low aerobic dose. Animals that received the high anaerobic dose had a significant increase in bacterial loads within the liver. Histologic examination of the L. monocytogenes positive livers exhibited locally extensive areas of hepatocellular necrosis, though the extent of this damage differed between treatment groups. Microbial community analysis of the cecum from gerbils infected with L. monocytogenes indicated that the abundance of Bacteroidales and Clostridiales increased and there was a decrease in the abundance of Spirochaetales. This study suggests that anaerobic conditions alter the localization pattern of L. monocytogenes within the gastrointestinal tract. These findings could relate to how different populations are more susceptible to listeriosis, as oxygen availability may differ within the gastrointestinal tract