Bacterial surface properties and transport behavior actively respond to an extracellular polymeric substance gradient in saturated porous media.

The transport and retention of bacteria in porous media, such as aquifer, are governed by the solid-liquid interface characteristics and bacterial mobility. The secretion of extracellular polymeric substance (EPS) by bacteria modifies their surface property, and thereby has effects on their adhesion to surface. The role of EPS in bacterial mobility within saturated quartz sand media is uncertain, as both promoting and inhibitory effects have been reported, and underlying mechanisms remain unclear. In this study, the effects of EPS on bacterial transport behavior and possible underlying mechanism were investigated at 4 concentrations (0 mg L-1, 50 mg L-1, 200 mg L-1 and 1000 mg L-1) using laboratory simulation experiments in conjunction with Extend Derjaguin-Landau-Verweu-Overbeek (XDLVO) modeling. The results showed that EPS facilitated bacterial mobility at all tested concentrations. It could be partially explained by the increased energy barrier between bacterial cells and quartz sand surface in the presence of EPS. The XDLVO sphere-plate model predicted that EPS induced a higher electrostatic double layer (EDL) repulsive force, Lewis acid-base (AB) and steric stabilization (ST), as well as a lower Lifshitz-van der Waals (LW) attractive force. However, at the highest EPS concentration (1000 mg L-1), the promotion of EPS on bacterial mobility weakened as a result of lower repulsive interactions between cells, which was supported by observed enhanced bacterial aggregation. Consequently, the increased aggregation led to greater bio-colloidal straining and ripening in the sand column, weakening the positive impact of EPS on bacterial transport. These findings suggested that EPS exhibited concentration-dependent effects on bacterial surface properties and transport behavior and revealed non-intuitive dual effects of EPS on those processes.

Extracellular polymeric substances induced cell-surface interactions facilitate bacteria transport in saturated porous media.

Bacteria often respond to dynamic soil environment through the secretion of extracellular polymeric substances (EPS). The EPS modifies cell surface properties and soil pore-scale hydration status, which in turn, influences bacteria transport in soil. However, the effect of soil particle size and EPS-mediated surface properties on bacterial transport in the soil is not well understood. In this study, the simultaneous impacts of EPS and collector size on Escherichia coli (E. coli) transport and deposition in a sand column were investigated. E. coli transport experiments were carried out under steady-state flow in saturated columns packed with quartz sand with different size ranges, including 0.300-0.425 mm (sand-I), 0.212-0.300 mm (sand-II), 0.106-0.150 mm (sand-III) and 0.075-0.106 mm (sand-IV). Bacterial retention increased with decreasing sand collector size, suggesting that straining played an important role in fine-textured media. Both experiment and simulation results showed a clear drop in the retention rate of the bacterial population with the presence of additional EPS (200 mg L-1) (EPS+). The inhibited retention of cells in sand columns under EPS+ scenario was likely attributed to enhanced bacteria hydrophilicity and electrostatic repulsion between cells and sand particles as well as reduced straining. Calculations of the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) interactions energies revealed that high repulsive energy barrier existed between bacterial cells and sand particles in EPS+ environment, primarily due to high repulsive electrostatic force and Lewis acid-base force, as well as low attractive Lifshitz-van der Waals force, which retarded bacterial population deposition. Steric stabilization of EPS would also prevent the approaching of cells close to the quartz surface and thereby hinder cell attachment. This study was the first to show that EPS reduced bacterial straining in saturated porous media. These findings provide new insight into the functional effects of extrinsic EPS on bacterial transport behavior in the saturated soil environment, e.g., aquifers.

Assessment and management of cough among patients with lung cancer in a radiotherapy department in China: a best practice implementation project.

OBJECTIVES: This project aimed to implement an evidence-based practice to assess and manage lung cancer-associated cough, thereby relieving patients' physical pain and psychological challenges and improving their quality of life. INTRODUCTION: Cough is one of the most common symptoms experienced by patients with lung cancer. If a cough is not proactively managed, patients may develop decreased compliance with treatments and experience a reduced quality of life. Cough assessment and management are essential components of nursing practice that should include evidence-based interventions. METHODS: Seven evidence-based audit criteria were developed from current evidence. The JBI Practical Application of Clinical Evidence System (PACES) was used to perform a baseline audit on 30 patients and 20 nurses in the Department of Radiotherapy of Nanfang Hospital. The Getting Research into Practice (GRiP) component of PACES was used to identify barriers, strategies, resources and outcomes. Following implementation of strategies to improve compliance, a post-audit was conducted using the same sample size and audit criteria. RESULTS: The seven evidence-based audit criteria were as follows: 1) Clinicians have received training on the assessment and management of lung cancer-associated cough; 2) In patients with lung cancer-associated cough, a comprehensive assessment was conducted to identify any co-existing causes linked to cough; 3) Any reversible causes of cough were treated according to evidence-based guidelines; 4) A validated scale was used to assess the frequency and severity of cough and distress experienced by the patients; 5) Patients (and their caregivers) have received education regarding management of cough; 6) Patients (and their caregivers) have received training on cough suppression exercises; 7) For symptomatic therapy, a stepwise approach was followed according to evidence-based guidelines. The baseline results showed that compliance rates were 0% for criteria 1, 4 and 5; 70% for criterion 6; 80% for criterion 7; 90% for criterion 3 and 93% for criterion 2. The implementation of strategies to increase compliance with best practice, including establishing training and education programs for nursing staff and patients, utilizing some validated scales to assess the frequency and severity of cough and the distress caused to the patients, and establishing a quality control team to supervise implementation of the assessment and management of cough, achieved ≥ 93% compliance rate for all seven audit criteria. CONCLUSION: An evidence-based and nurses-oriented best practice for cough assessment and management was successfully established among patients with lung cancer-associated cough.