Regarded as a silent epidemic, chronic wounds are a global public health issue. Wound healing is a complex, synchronized cascade of physiological processes restoring the anatomic and functional integrity of the skin; however, chronic wounds fail to proceed through the wound healing cascade. Wound pH oscillates during wound healing, usually traversing from a neutral pH to an acidic pH, while chronic wounds perpetuate in an elevated alkaline milieu. Although a neglected clinical parameter, pH has implications for relatively all pathologies of wound healing affecting oxygen release, angiogenesis, protease activity, bacterial toxicity and antimicrobial activity. Despite the array of wound healing products currently marketed, understanding the implications of pH on arresting wound healing can stimulate innovation within this vast market.
Formation of crystalline biofilms following infection by Proteus mirabilis can lead to encrustation and blockage of long-term indwelling catheters, with serious clinical consequences. We describe a simple sensor, placed within the catheter drainage bag, to alert of impending blockage via a urinary color change. The pH-responsive sensor is a dual-layered polymeric "lozenge", able to release the self-quenching dye 5(6)-carboxyfluorescein in response to the alkaline urine generated by the expression of bacterial urease. Sensor performance was evaluated within a laboratory model of the catheterized urinary tract, infected with both urease positive and negative bacterial strains under conditions of established infection, achieving an average "early warning" of catheter blockage of 14.5 h. Signaling only occurred following infection with urease positive bacteria. Translation of these sensors into a clinical environment would allow appropriate intervention before the occurrence of catheter blockage, a problem for which there is currently no effective control method.
It is becoming increasingly accepted that to understand and model the bacterial colonization and infection of abiotic surfaces requires the use of a biofilm model. There are many bacterial colonizations by at least two primary species, however this is difficult to model in vitro. This study reports the development of a simple mixed-species biofilm model using strains of two clinically significant bacteria: Staphylococcus aureus and Pseudomonas aeruginosa grown on nanoporous polycarbonate membranes on nutrient agar support. Scanning electron microscopy revealed the complex biofilm characteristics of two bacteria blending in extensive extracellular matrices. Using a prototype wound dressing which detects cytolytic virulence factors, the virulence secretion of 30 single and 40 mixed-species biofilms was tested. P. aeruginosa was seen to out-compete S. aureus, resulting in a biofilm with P. aeruginosa dominating. In situ growth of mixed-species biofilm under prototype dressings showed a real-time correlation between the viable biofilm population and their associated virulence factors, as seen by dressing fluorescent assay. This paper aims to provide a protocol for scientists working in the field of device related infection to create mixed-species biofilms and demonstrate that such biofilms are persistently more virulent in real infections. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018.
Objective: Emerging evidence suggests that chest radiography (CXR) following central venous catheter (CVC) placement is unnecessary when point-of-care ultrasound (POCUS) is used to confirm catheter position and exclude pneumothorax. However, few providers have adopted this practice, and it is unknown what contributing factors may play a role in this lack of adoption, such as ultrasound experience. The objective of this study was to evaluate the diagnostic accuracy of POCUS to confirm CVC position and exclude a pneumothorax after brief education and training of nonexperts. Methods:We performed a prospective cohort study in a single academic medical center to determine the diagnostic characteristics of a POCUS-guided CVC confirmation protocol after brief training performed by POCUS nonexperts. POCUS nonexperts (emergency medicine senior residents and critical care fellows) independently performed a POCUS-guided CVC confirmation protocol after a 30-minute didactic training. The primary outcome was the diagnostic accuracy of the POCUS-guided CVC confirmation protocol for malposition and pneumothorax detection. Secondary outcomes were efficiency and feasibility of adequate image acquisition, adjudicated by POCUS experts.Results: Twenty-six POCUS nonexperts collected data on 190 patients in the final analysis. There were five (2.5%) CVC malpositions and six (3%) pneumothoraxes on CXR. The positive likelihood ratios of POCUS for malposition detection and pneumothorax were 12.33 (95% confidence interval [CI] = 3.26 to 46.69) and 3.41 (95% CI = 0.51 to 22.76), respectively. The accuracy of POCUS for pneumothorax detection compared to CXR was 0.93 (95% CI = 0.88 to 0.96) and the sensitivity was 0.17 (95% CI = 0.00 to 0.64). The median (interquartile range) time for CVC confirmation was lower for POCUS (9 minutes [8.5-9.5 minutes]) compared to CXR
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