Artificial dry surface biofilm (DSB) models for testing the efficacy of cleaning and disinfection

Dry surface biofilms (DSB) harbouring pathogens are widespread in healthcare settings, difficult to detect and resistant to cleaning and disinfection interventions. Here, we describe a practical test protocol to palliate the lack of standard efficacy test methods for DSB. Staphylococcus aureus DSB were produced over a 12‐day period, grown with or without the presence of organic matter, and their composition and viability were evaluated. Disinfectant treatment was conducted with a modified ASTM2967‐15 test and reduction in viability, transferability, and biofilm regrowth post treatment were measured. Dry surface biofilms produced over a 12‐day period had a similar carbohydrates, proteins and DNA content, regardless the presence or absence of organic matter. The combination of sodium hypochlorite (1,000 ppm) and a microfiber cloth was only effective against DSB in the absence of organic load. With the increasing concerns of the uncontrolled presence of DSB in healthcare settings, the development of effective interventions is paramount. We propose that our DSB model in the presence of organic load is appropriate for the testing of biocidal products, while the use of three parameters, log10 reduction, transferability and regrowth, provides an accurate and practical measurement of product efficacy

It's a trap! The development of a versatile drain biofilm model and its susceptibility to disinfection

Background Pathogens in drain biofilms pose a significant risk for hospital-acquired infection. However, the evidence of product effectiveness in controlling drain biofilm and pathogen dissemination are scarce. A novel in-vitro biofilm model was developed to address the need for a robust, reproduceable and simple testing methodology for disinfection efficacy against a complex drain biofilm. Methods Identical complex drain biofilms were established simultaneously over 8 days, mimicking a sink trap. Reproducibility of their composition was confirmed by next-generation sequencing. The efficacy of sodium hypochlorite 1000 ppm (NaOCl), sodium dichloroisocyanurate 1000 ppm (NaDCC), non-ionic surfactant (NIS) and peracetic acid 4000 ppm (PAA) was explored, simulating normal sink usage conditions. Bacterial viability and recovery following a series of 15-min treatments were measured in three distinct parts of the drain. Results The drain biofilm consisted of 119 mixed species of Gram-positive and -negative bacteria. NaOCl produced a >4 log10 reduction in viability in the drain front section alone, while PAA achieved a >4 log10 reduction in viability in all of the drain sections following three 15-min doses and prevented biofilm regrowth for >4 days. NIS and NaDCC failed to control the biofilm in any drain sections. Conclusions Drains are one source of microbial pathogens in healthcare settings. Microbial biofilms are notoriously difficult to eradicate with conventional chemical biocidal products. The development of this reproducible in-vitro drain biofilm model enabled understanding of the impact of biocidal products on biofilm spatial composition and viability in different parts of the drain. Keyword

Determining the electrochemical transport parameters of sodium-ions in hard carbon composite electrodes

Sodium-ion batteries offer advantages over conventional Li-ion batteries, including cost and safety. However, much less is known about their operation and performance properties, particularly at the anode. The electron and ion transport in the active materials and composite electrode significantly impact battery performance. Understanding the changes in transport properties as a function of state-of-charge and state-of-health is essential for effective electrode design and performance assessment. In this work, the resistivity and diffusivity of sodium transport in hard carbon composite electrodes are studied at different states-of-health, using Galvanostatic Intermittent Titration Technique (GITT), Electrochemical Impedance Spectroscopy (EIS), and Electrochemical Potential Spectroscopy (EPS) in a stable 3-electrode test cell configuration. The reference electrode eliminated some voltage errors arising from the overpotentials on the counter electrode. The resistance contributions from the surface electrolyte interface, electrolyte transport in the electrode pores, and the charge transfer resistance are extrapolated from the impedance measurements and the diffusion coefficient from the GITT and EPS. The different techniques indicate similar trends in the diffusion coefficient during sodiation, desodiation, and ageing, although different orders of magnitude were observed between the EPS and GITT data. The accuracy of the parameters calculated using the different electrochemical techniques is discussed in detail

How dirty is your QWERTY? The risk of healthcare pathogen transmission from computer keyboards

Introduction Healthcare environmental surfaces may be contaminated with micro-organisms that cause healthcare-associated infections (HCAIs). Special attention is paid to near-patient surfaces but sites outside the patient zone receive less attention. This paper presents data on keyboard contamination and the risk of pathogen transmission from keyboards. Methods Keyboards from nursing stations in three hospitals and a dental practice were analysed for bacterial contamination. Surfaces were pre-treated to remove planktonic bacteria so that any remaining bacteria were presumed to be associated with biofilm. Bacterial transfer from keyboard keys was studied following wiping with sterile water or sodium hypochlorite. The presence of multi-drug-resistant organisms (MDROs) was sought using selective culture. Results Moist swabbing did not detect bacteria from any keyboard samples. Use of enrichment broth, however, demonstrated MDROs from most samples. Gram-negative bacteria were recovered from almost half (45%) of the samples, with meticillin-resistant Staphylococcus aureus, vancomycin-resistant enterococcus and MDR Acinetobacter spp. recovered from 72%, 31% and 17% of samples, respectively. Isolates were transferred from 69% of samples after wiping with sterile water, and from 54% of samples after wiping with 1000 ppm sodium hypochlorite. Discussion While moist swabbing failed to detect bacteria from keyboards, pathogens were recovered using enrichment culture. Use of water- or NaOCl-soaked wipes transferred bacteria from most samples tested. This study implies that hospital keyboards situated outside the patient zone commonly harbour dry surface biofilms (DSBs) that offer a potential reservoir for transferable pathogens. While the role of keyboards in transmission is uncertain, there is a need to pursue effective solutions for eliminating DSBs from keyboards

Beware Biofilm! Dry biofilms containing bacterial pathogens on multiple healthcare surfaces; a multicentre study

BackgroundWet biofilms associated with medical devices have been widely studied and their link with healthcare-associated infections (HCAIs) is well recognized. Little attention has been paid to the presence of dry biofilms on environmental surfaces in healthcare settings.AimTo investigate the occurrence, prevalence, and diversity of dry biofilms on hospital surfaces.MethodsSixty-one terminally cleaned items were received from three different UK hospitals. The presence of dry biofilm was investigated using culture-based methods and scanning electron microscopy (SEM). Bacterial diversity within biofilms was investigated using ribosomal RNA intergenic spacer analysis (RISA)–polymerase chain reaction and next-generation sequencing.FindingsMulti-species dry biofilms were recovered from 95% of 61 samples. Abundance and complexity of dry biofilms were confirmed by SEM. All biofilms harboured Gram-positive bacteria including pathogens associated with HCAI; 58% of samples grew meticillin-resistant Staphylococcus aureus. Dry biofilms had similar physical composition regardless of the type of items sampled or the ward from which the samples originated. There were differences observed in the dominance of particular species: dry biofilms from two hospitals contained mostly staphylococcal DNA, whereas more Bacillus spp. DNA was found on surfaces from the third hospital.ConclusionThe presence of dry biofilms harbouring bacterial pathogens is virtually universal on commonly used items in healthcare settings. The role of dry biofilms in spreading HCAIs may be underestimated. The risk may be further exacerbated by inefficient cleaning and disinfection practices for hospital surface

Supply network science: Emergence of a new perspective on a classical field.

Supply networks emerge as companies procure goods from one another to produce their own products. Due to a chronic lack of data, studies on these emergent structures have long focussed on local neighbourhoods, assuming simple, chain-like structures. However, studies conducted since 2001 have shown that supply chains are indeed complex networks that exhibit similar organisational patterns to other network types. In this paper, we present a critical review of theoretical and model based studies which conceptualise supply chains from a network science perspective, showing that empirical data do not always support theoretical models that were developed, and argue that different industrial settings may present different characteristics. Consequently, a need that arises is the development and reconciliation of interpretation across different supply network layers such as contractual relations, material flow, financial links, and co-patenting, as these different projections tend to remain in disciplinary siloes. Other gaps include a lack of null models that show whether the observed properties are meaningful, a lack of dynamical models that can inform how layers evolve and adopt to changes, and a lack of studies that investigate how local decisions enable emergent outcomes. We conclude by asking the network science community to help bridge these gaps by engaging with this important area of research

Dirty QWERTY: there's no ESC!

We were delighted to see our study on hospital keyboards receiving interest from Prof. Vos' research group in their recent letter. Clearly, both our groups are passionate about infection prevention, and ways to improve the safety in hospitals in UK and The Netherlands. We are therefore happy to provide additional information about our study to help with their understanding of keyboard contamination in UK hospitals. [...