Optimisation of a lozenge-based sensor for detecting impending blockage of urinary catheters

Catheter-associated urinary tract infections resulting from urease-positive microorganisms are more likely to cause a urinary catheter blockage owing to the urease activity of the microbes. Catheter blockage can be dangerous and increases the risk of severe infections, such as sepsis. Ureases, a virulence factor in Proteus mirabilis, cause an increase in urine pH - leading to blockage. An optimised biosensor "lozenge" is presented here, which is able to detect impending catheter blockage. This lozenge has been optimised to allow easy manufacture and commercialisation. It functions as a sensor in a physiologically representative model of a catheterised urinary tract, providing 6.7 h warning prior to catheter blockage. The lozenge is stable in healthy human urine and can be sterilized for clinical use by ethylene oxide. Clinically, the lozenge will provide a visible indication of impending catheter blockage, enabling quicker clinical intervention and thus reducing the morbidity and mortality associated with blockage.</p

Limiting Pseudomonas aeruginosa Biofilm Formation Using Cold Atmospheric Pressure Plasma

We investigate the ability to disrupt and limit growth biofilms of Pseudomonas aeruginosa using application of cold atmospheric pressure (CAP) plasma. The effect of the bio-film's exposure to a helium (CAP) jet was assessed at varying time points during biofilm maturation. Results showed that the amount of time during biofilm growth that CAP pressure was applied has a crucial role on the ability of biofilms to mature and recover after CAP exposure. Intervention during the early stages of biofilm formation (0-8 h) results in a 4-5-log reduction in viable bacterial cells (measured at 24 h of incubation) relative to untreated biofilms. However, CAP treatment of biofilm at 12 h and above only results in a 2-log reduction in viable cells. This has potentially important implications for future clinical application of CAP to treat infected wounds

Di-anionic self-associating supramolecular amphiphiles (SSAs) as antimicrobial agents against MRSA and Escherichia coli

Herein, we report a series of di-anionic supramolecular self-associating amphiphiles (SSAs). We elucidate the antimicrobial properties of these SSAs against both methicillin resistant Staphylococcus aureus and Escherichia coli. In addition, we show this class of compound to form both intra- and intermolecular hydrogen bonded macrocyclic structures in the solid state

TCF-ALP: a fluorescent probe for the selective detection of Staphylococcus bacteria and application in "smart" wound dressings

Alkaline phosphatase (ALP) is an important enzyme-based biomarker present in several bacterial species; however, it is currently undervalued as a strategy to detect pathogenic bacteria. Here, we explore our ALP-responsive colorimetric and fluorescent probe (TCF-ALP) for such applications. TCF-ALP displayed a colorimetric and fluorescence response towards Staphylococcus aureus (S. aureus), with a limit of detection of 3.7 × 106 CFU mL−1 after 24 h incubation. To our surprise, TCF-ALP proved selective towards Staphylococcus bacteria when compared with Enterococcus faecalis (E. faecalis), and Gram-negative P. aeruginosa and E. coli. Selectivity was also seen in clinically relevant S. aureus biofilms. Owing to the high prevalence and surface location of S. aureus in chronic wounds, TCF-ALP was subsequently encapsulated in polyvinyl alcohol (PVA)-based hydrogels as a proof-of-concept “smart” wound dressing. TCF-ALP hydrogels were capable of detecting S. aureus in planktonic and biofilm assays, and displayed a clear colour change from yellow to purple after 24 h incubation using ex vivo porcine skin models. Overall, TCF-ALP is a simple tool that requires no prior knowledge, training, or specialist equipment, and has the potential to overcome issues related to invasive swabbing and tissue biopsy methods. Thus, TCF-ALP could be used as a tool to monitor the early development of infection in a wound and allow for the rapid provision of appropriate treatment for Staphylococcal bacterial infections

The Evaluation of Ester Functionalised TCF‐based Fluorescent Probes for the Detection of Bacterial Species

The ester functionality is commonly seen in the areas of chemical biology and medicinal chemistry for the design of cell‐permeable active molecules. Ester‐based pro‐drug/pro‐sensor strategies are employed to mask polar functional groups (i. e. carboxylic acids) and improve the overall cell permeability of these functional molecules. However, their use as reactive units for sensing applications, including bacterial detection, has not been fully explored. Herein, we synthesised two TCF‐based fluorescent probes, TCF‐OAc and TCF‐OBu. As expected, both TCF‐OAc and TCF‐OBu demonstrated a significant fluorescence (22‐ and 43‐fold, respectively) and colorimetric response (yellow to purple) towards porcine liver esterase (PLE) with a limit of detection of 1.18 mU/mL and 0.45 mU/mL, respectively. With these results in hand, the ability of these probes to detect planktonic suspensions of gram‐positive Staphylococcus aureus (S. aureus) and gram‐negative Pseudomonas aeruginosa (P. aeruginosa), and Escherichia coli (E. coli) were evaluated. Different fluorescence responses for gram‐positive and gram‐negative bacteria were observed between TCF‐OAc and TCF‐OBu. After 1 h incubation, TCF‐OAc proved more sensitive towards S. aureus, demonstrating a significant fluorescence “turn on” response (16‐fold); whereas, TCF‐OBu was more selective towards P. aeruginosa, with a 22‐fold increase in the fluorescence response observed. These results demonstrate the influence of the ester chain length on the selectivity for bacterial species

Diagnostic test accuracy of point-of-care procalcitonin to diagnose serious bacterial infections in children

Background: The National Institute for Health and Care Excellence (NICE) have called for research into the role of biomarkers, and specifically procalcitonin (PCT), for the early diagnosis of serious bacterial infections (SBI) in children. The aim of this study was to compare the diagnostic test accuracy of C-reactive protein (CRP) and PCT for the diagnosis of SBI in children. Methods: Data was collected prospectively from four UK emergency departments (ED) between November 2017 and June 2019. Consecutive children under 18years of age with fever and features of possible sepsis and/or meningitis were eligible for inclusion. The index tests were PCT and CRP and the reference standard was the confirmation of SBI. Results: 213 children were included in the final analysis. 116 participants (54.5%) were male, and the median age was 2 years, 9months. Parenteral antibiotics were given to 100 (46.9%), three (1.4%) were admitted to a paediatric intensive care unit and there were no deaths. There were ten (4.7%) confirmed SBI. The area under the curve for PCT and CRP for the detection of SBI was identical at 0.70. Conclusions: There was no difference in the performance of PCT and CRP for the recognition of SBI in this cohort. Trial registration: Registered at https://www.clinicaltrials.gov(trial registration: NCT03378258) on the 19th of December 2017

On-demand release of silver from composite hydrogel by cold atmospheric plasma jet for wound infection control

Silver is an antimicrobial commonly used within wound care chiefly in advanced dressings or in a topical cream form, such as silver sulfadiazine (SSD). Although silver is effective at controlling the growth of many common wound bacteria, it can be cytotoxic and can build up in tissue, stalling the healing process. Here, we demonstrate the development of an on-demand release system for delivery of silver from a composite hydrogel comprising sodium polyacrylate particles dispersed in a cryo-crosslinked polyvinyl alcohol carrier gel. Application of cold atmospheric plasma (CAP) jet to the silver loaded hydrogel resulted in controlled release of silver. This release is thought to occur due to the formation of nitrous acids in the hydrogel by the CAP, resulting in protonation of carboxylate groups in the hydrogel and subsequent gel de-swelling due to the reduction in interchain charge repulsion. The location of silver within the sodium polyacrylate particles was probed using scanning electron microscopy and EDX imaging. The released silver inhibited the growth of Enterococcus faecalis, Pseudomonas aeruginosa, and Staphylococcus aureus and significantly reduced the viable cell count of the P. aeruginosa biofilm