Predator-prey interactions in aerobic granulation systems

Predation by protozoa can impact bacterial communities by controlling their biomass and alter the community species composition. Bacterial communities are essential for the functioning of most ecosystems including engineered systems such as activated floccular sludge, where bacteria are responsible for biological nutrient removal and flocculation. Activated floccular sludge is often utilized to cultivate aerobic granules over long periods of time. Although the formation of granules has been optimized by controlling physical factors, the instability of aerobic granules remains a challenge for its implementation in full-scale wastewater treatment systems. While it has been hypothesised that protozoa are important in the formation of granules, no studies have characterized the abundance and diversity of protozoa during aerobic granulation. In this study, the impact of protozoa on microbial communities was monitored. Sessile ciliates were reported to be the most abundant protozoa that colonized the surfaces of granules. These ciliates consume suspended bacteria and are also hypothesized to act as a form of substratum for bacteria; colonization. Here, four bioreactors seeded with activated floccular sludge were operated for aerobic granulation for 11 weeks to better understand the roles of protozoa during the formation of aerobic granules. The abundance and diversity of protozoa decreased initially due to reduction in settling time. Upon the formation of granules, sessile ciliates became the dominant group of protozoa with gradual increase in abundance. However, microbial community analysis and correlation studies demonstrated that protozoa did not have a significant role in granule formation. In contrast, bacteria, particularly Candidatus Accumulibacter, were suggested to have a greater role in the formation of granules. The role of predation by protozoa on the formation of granules was further explored through the inhibition of protozoa in floccular sludge performed to investigate if aerobic granulation would be affected without protozoa. The absence of protozoa did not significantly affect the formation of granules from floccular sludge. Similar to the experiments following the changes in the community composition, it was also observed that Candidatus Accumulibacter was highly dominant when granules were formed in the treated sludge. In addition, inhibition of protozoa, including sessile ciliates on the surface of pre-formed granules, also did not result in disintegration of granules. Granules with and without sessile ciliates continued to maintain their granular appearance and size. Overall, the data suggested that protozoa did not play a dominant role in granulation and it was the change in sludge morphology that selected for the dominance of sessile ciliates in granules. Aerobic granules and activated floccular sludge comprised of high species diversity. Therefore, to better define the mechanisms that drive the interaction between microbial communities and predators, a mixed species biofilm system composed of Pseudomonas aeruginosa, Klebsiella pneumoniae and Pseudomonas protegens was subjected to protozoan grazing by the model ciliate, Tetrahymena pyriformis. It was found that grazing sensitive strains, K. pneumoniae and P. protogens, gained associational resistance from the grazing resistant P. aeruginosa. This resistance was partly due to the production of rhamnolipids, however results showed that there were other unidentified factors that provide P. aeruginosa resistance to predation.Doctor of Philosophy (IGS

A randomized controlled trial examining the effectiveness of a STOMA psychosocial intervention programme on the outcomes of colorectal patients with a stoma: Study protocol

10.1111/jan.12595Journal of Advanced Nursing7161310-132

A randomized controlled trial examining the effectiveness of a STOMA psychosocial intervention programme on the outcomes of colorectal patients with a stoma: study protocol

Aims: To report a study protocol that evaluates the effects of a psychosocial intervention on patients with a newly formed stoma. Background: With the loss of a significant body function and distorted body image, stoma patients experience physical, psychological and social challenges. Nurses have an important role in helping patients' make a smooth transition to living with their stoma. Limited studies have examined the effects of psychosocial interventions on improving stoma-related health outcomes. Design: A randomized controlled trial is planned. Methods: Eighty-four patients with newly formed stoma in a tertiary hospital in Singapore (Research Ethics Committee approval obtained in January 2013) will be recruited. Participants will be randomly assigned to either a control group who receive routine care or an intervention group who receive STOMA psychosocial intervention besides routine care. Outcome variables include stoma care self-efficacy, days to stoma proficiency, length of hospital stay, acceptance of stoma, anxiety and depression and quality of life. Data will be collected at four time points: before randomization and intervention (baseline), on the day of discharge (mid-intervention), at 4\ua0weeks after discharge (postintervention 1) and at 4\ua0months after discharge (postintervention 2). Discussion: This study will develop a psychosocial intervention programme, which may improve patients' stoma-related outcomes. The findings will provide direction to health professionals about education and the type of support that could be offered to patients concerning stoma care in the hospital setting, which will eventually improve their quality of life

Lipid-Polymer Hybrid Nanoparticles Enhance the Potency of Ampicillin against Enterococcus faecalis in a Protozoa Infection Model

[Image: see text] Enterococcus faecalis (E. faecalis) biofilms are implicated in endocarditis, urinary tract infections, and biliary tract infections. Coupled with E. faecalis internalization into host cells, this opportunistic pathogen poses great challenges to conventional antibiotic therapy. The inability of ampicillin (Amp) to eradicate bacteria hidden in biofilms and intracellular niches greatly reduces its efficacy against complicated E. faecalis infections. To enhance the potency of Amp against different forms of E. faecalis infections, Amp was loaded into Lipid-Polymer hybrid Nanoparticles (LPNs), a highly efficient nano delivery platform consisting of a unique combination of DOTAP lipid shell and PLGA polymeric core. The antibacterial activity of these nanoparticles (Amp-LPNs) was investigated in a protozoa infection model, achieving a much higher multiplicity of infection (MOI) compared with studies using animal phagocytes. A significant reduction of total E. faecalis was observed in all groups receiving 250 μg/mL Amp-LPNs compared with groups receiving the same concentration of free Amp during three different interventions, simulating acute and chronic infections and prophylaxis. In early intervention, no viable E. faecalis was observed after 3 h LPNs treatment whereas free Amp did not clear E. faecalis after 24 h treatment. Amp-LPNs also greatly enhanced the antibacterial activity of Amp at late intervention and boosted the survival rate of protozoa approaching 400%, where no viable protozoa were identified in the free Amp groups at the 40 h postinfection treatment time point. Prophylactic effectiveness with Amp-LPNs at a concentration of 250 μg/mL was exhibited in both bacteria elimination and protozoa survival toward subsequent infections. Using protozoa as a surrogate model for animal phagocytes to study high MOI infections, this study suggests that LPN-formulated antibiotics hold the potential to significantly improve the therapeutic outcome in highly complicated bacterial infections

Associational resistance to predation by protists in a mixed species biofilm

Mixed species biofilms exhibit increased tolerance to numerous stresses compared to single species biofilms. The aim of this study was to examine the effect of grazing by the heterotrophic protist, Tetrahymena pyriformis, on a mixed species biofilm consisting of Pseudomonas aeruginosa, Pseudomonas protegens, and Klebsiella pneumoniae. Protozoan grazing significantly reduced the single species K. pneumoniae biofilm, and the single species P. protegens biofilm was also sensitive to grazing. In contrast, P. aeruginosa biofilms were resistant to predation. This resistance protected the otherwise sensitive members of the mixed species biofilm consortium. Rhamnolipids produced by P. aeruginosa were shown to be the primary toxic factor for T. pyriformis. However, a rhamnolipid-deficient mutant of P. aeruginosa (P. aeruginosa ΔrhlAB) maintained grazing resistance in the biofilm, suggesting the presence of at least one additional protective mechanism. P. aeruginosa with a deleted gene encoding the type III secretion system also resisted grazing. A transposon library was generated in the ΔrhlAB mutant to identify the additional factor involved in community biofilm protection. Results indicated that the Pseudomonas Quinolone Signal (PQS), a quorum sensing signaling molecule, was likely responsible for this effect. We confirmed this observation by showing that double mutants of ΔrhlAB and genes in the PQS biosynthetic operon lost grazing protection. We also showed that PQS was directly toxic to T. pyriformis. This study demonstrates that residing in a mixed species biofilm can be an advantageous strategy for grazing sensitive bacterial species, as P. aeruginosa confers community protection from protozoan grazing through multiple mechanisms. IMPORTANCE: Biofilms have been shown to protect bacterial cells from predation by protists. Biofilm studies have traditionally used single species systems, which have provided information on the mechanisms and regulation of biofilm formation and dispersal, and the effects of predation on these biofilms. However, biofilms in nature are comprised of multiple species. To better understand how multispecies biofilms are impacted by predation, a model mixed-species biofilm was here exposed to protozoan predation. We show that the grazing sensitive strains K. pneumonia and P. protogens gained associational resistance from the grazing resistant P. aeruginosa. Resistance was due to the secretion of rhamnolipids and quorum sensing molecule PQS. This work highlights the importance of using mixed species systems.Ministry of Education (MOE)Nanyang Technological UniversityNational Research Foundation (NRF)Published versionWe acknowledge the financial support from National Research Foundation and Ministry of Education Singapore under its Research Centre of Excellence Program. This work was also supported by a grant from the Singapore Ministry of Education (MOE2019-T2-1-050) and Australian Research Council Discovery Project DP170100453. Siew Herng Chan and Yu Fen Goh were supported by the Interdisciplinary Graduate School in conjunction with the Singapore Centre for Environmental Life Sciences Engineering. We also wish to thank the ESCMID Study Group for Biofilms–ESGB for supporting Henriette Lyng Røders participation in Eurobiofilms 2015 with a travel grant

Effects of once-weekly exenatide on cardiovascular outcomes in type 2 diabetes

BACKGROUND: The cardiovascular effects of adding once-weekly treatment with exenatide to usual care in patients with type 2 diabetes are unknown. METHODS: We randomly assigned patients with type 2 diabetes, with or without previous cardiovascular disease, to receive subcutaneous injections of extended-release exenatide at a dose of 2 mg or matching placebo once weekly. The primary composite outcome was the first occurrence of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke. The coprimary hypotheses were that exenatide, administered once weekly, would be noninferior to placebo with respect to safety and superior to placebo with respect to efficacy. RESULTS: In all, 14,752 patients (of whom 10,782 [73.1%] had previous cardiovascular disease) were followed for a median of 3.2 years (interquartile range, 2.2 to 4.4). A primary composite outcome event occurred in 839 of 7356 patients (11.4%; 3.7 events per 100 person-years) in the exenatide group and in 905 of 7396 patients (12.2%; 4.0 events per 100 person-years) in the placebo group (hazard ratio, 0.91; 95% confidence interval [CI], 0.83 to 1.00), with the intention-to-treat analysis indicating that exenatide, administered once weekly, was noninferior to placebo with respect to safety (P<0.001 for noninferiority) but was not superior to placebo with respect to efficacy (P=0.06 for superiority). The rates of death from cardiovascular causes, fatal or nonfatal myocardial infarction, fatal or nonfatal stroke, hospitalization for heart failure, and hospitalization for acute coronary syndrome, and the incidence of acute pancreatitis, pancreatic cancer, medullary thyroid carcinoma, and serious adverse events did not differ significantly between the two groups. CONCLUSIONS: Among patients with type 2 diabetes with or without previous cardiovascular disease, the incidence of major adverse cardiovascular events did not differ significantly between patients who received exenatide and those who received placebo