Predictive modelling of a novel anti-adhesion therapy to combat bacterial colonisation of burn wounds

As the development of new classes of antibiotics slows, bacterial resistance to existing antibiotics is becoming an increasing problem. A potential solution is to develop treatment strategies with an alternative mode of action. We consider one such strategy: anti-adhesion therapy. Whereas antibiotics act directly upon bacteria, either killing them or inhibiting their growth, anti-adhesion therapy impedes the binding of bacteria to host cells. This prevents bacteria from deploying their arsenal of virulence mechanisms, while simultaneously rendering them more susceptible to natural and artificial clearance. In this paper, we consider a particular form of anti-adhesion therapy, involving biomimetic multivalent adhesion molecule 7 coupled polystyrene microbeads, which competitively inhibit the binding of bacteria to host cells. We develop a mathematical model, formulated as a system of ordinary differential equations, to describe inhibitor treatment of a Pseudomonas aeruginosa burn wound infection in the rat. Benchmarking our model against in vivo data from an ongoing experimental programme, we use the model to explain bacteria population dynamics and to predict the efficacy of a range of treatment strategies, with the aim of improving treatment outcome. The model consists of two physical compartments: the host cells and the exudate. It is found that, when effective in reducing the bacterial burden, inhibitor treatment operates both by preventing bacteria from binding to the host cells and by reducing the flux of daughter cells from the host cells into the exudate. Our model predicts that inhibitor treatment cannot eliminate the bacterial burden when used in isolation; however, when combined with regular or continuous debridement of the exudate, elimination is theoretically possible. Lastly, we present ways to improve therapeutic efficacy, as predicted by our mathematical model

Mathematical model predicts anti-adhesion--antibiotic--debridement combination therapies can clear an antibiotic resistant infection

As antimicrobial resistance increases, it is crucial to develop new treatment strategies to counter the emerging threat. In this paper, we consider combination therapies involving conventional antibiotics and debridement, coupled with a novel anti-adhesion therapy, and their use in the treatment of antimicrobial resistant burn wound infections. Our models predict that anti-adhesion–antibiotic–debridement combination therapies can eliminate a bacterial infection in cases where each treatment in isolation would fail. Antibiotics are assumed to have a bactericidal mode of action, killing bacteria, while debridement involves physically cleaning a wound (e.g. with a cloth); removing free bacteria. Anti-adhesion therapy can take a number of forms. Here we consider adhesion inhibitors consisting of polystyrene microbeads chemically coupled to a protein known as multivalent adhesion molecule 7, an adhesin which mediates the initial stages of attachment of many bacterial species to host cells. Adhesion inhibitors competitively inhibit bacteria from binding to host cells, thus rendering them susceptible to removal through debridement. An ordinary differential equation model is developed and the antibiotic-related parameters are fitted against new in vitro data gathered for the present study. The model is used to predict treatment outcomes and to suggest optimal treatment strategies. Our model predicts that anti-adhesion and antibiotic therapies will combine synergistically, producing a combined effect which is often greater than the sum of their individual effects, and that anti-adhesion–antibiotic–debridement combination therapy will be more effective than any of the treatment strategies used in isolation. Further, the use of inhibitors significantly reduces the minimum dose of antibiotics required to eliminate an infection, reducing the chances that bacteria will develop increased resistance. Lastly, we use our model to suggest treatment regimens capable of eliminating bacterial infections within clinically relevant timescales

Biofilms in diabetic foot ulcers: impact, risk factors and control strategies

Diabetic foot ulcers (DFUs) are a serious complication from diabetes mellitus, with a huge economic, social and psychological impact on the patients life. One of the main reasons why DFUs are so difficult to heal is related to the presence of biofilms. Biofilms promote wound inflammation and a remarkable lack of response to host defences/treatment options, which can lead to disease progression and chronicity. In fact, appropriate treatment for the elimination of these microbial communities can prevent the disease evolution and, in some cases, even avoid more serious outcomes, such as amputation or death. However, the detection of biofilm-associated DFUs is difficult due to the lack of methods for diagnostics in clinical settings. In this review, the current knowledge on the involvement of biofilms in DFUs is discussed, as well as how the surrounding environment influences biofilm formation and regulation, along with its clinical implications. A special focus is also given to biofilm-associated DFU diagnosis and therapeutic strategies. An overview on promising alternative therapeutics is provided and an algorithm considering biofilm detection and treatment is proposed.This work was supported by: Base Funding—UIDB/00511/2020 of the Laboratory for Process Engineering, Environment, Biotechnology and Energy—LEPABE—funded by national funds through the FCT/MCTES (PIDDAC); Project Biocide_for_Biofilm-PTDC/BII-BTI/30219/2017- POCI-01-0145-FEDER-030219, ABFISH–PTDC/ASP-PES/28397/2017-POCI-01-0145-FEDER- 028397 and Germirrad-POCI-01-0247-FEDER-072237, funded by FEDER funds through COMPETE2020— Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PID DAC) through FCT/MCTES. The authors also thank the CITAB (Centre for the Research and Technol ogy of Agro-Environmental and Biological Sciences) under the scope of the FCT funds with reference UIDB/AGR/04033/2020. Ana Afonso (2020.04773.BD) and Diana Oliveira (SFRH/BD/138217/2018) acknowledge the FCT grants. Anabela Borges thanks the FCT for the financial support of their work contract through the Scientific Employment Stimulus—Individual Call—[CEECIND/01261/2017].info:eu-repo/semantics/publishedVersio

Bioprospecting the Skin Microbiome: Advances in Therapeutics and Personal Care Products

Bioprospecting is the discovery and exploration of biological diversity found within organisms, genetic elements or produced compounds with prospective commercial or therapeutic applications. The human skin is an ecological niche which harbours a rich and compositional diversity microbiome stemming from the multifactorial interactions between the host and microbiota facilitated by exploitable effector compounds. Advances in the understanding of microbial colonisation mechanisms alongside species and strain interactions have revealed a novel chemical and biological understanding which displays applicative potential. Studies elucidating the organismal interfaces and concomitant understanding of the central processes of skin biology have begun to unravel a potential wealth of molecules which can exploited for their proposed functions. A variety of skin-microbiome-derived compounds display prospective therapeutic applications, ranging from antioncogenic agents relevant in skin cancer therapy to treatment strategies for antimicrobial-resistant bacterial and fungal infections. Considerable opportunities have emerged for the translation to personal care products, such as topical agents to mitigate various skin conditions such as acne and eczema. Adjacent compound developments have focused on cosmetic applications such as reducing skin ageing and its associated changes to skin properties and the microbiome. The skin microbiome contains a wealth of prospective compounds with therapeutic and commercial applications; however, considerable work is required for the translation of in vitro findings to relevant in vivo models to ensure translatability.</jats:p

Open fracture infection following combat trauma : defining the problem and evaluating novel treatments

PhD ThesisThe British military was engaged in combat operations in Iraq and Afghanistan over a 12-year period from 2003 to 2014. It has been asserted that over this time survival after combat injury improved generating a cohort of patients with complex limb injuries, including open fractures, which are prone to infection and challenging to reconstruct. Using an anatomic measure of injury severity I demonstrate an improvement in survival after combat injury. I further tested this finding by devising a military specific version of an anatomic-physiological injury scoring system, which confirmed the survival improvement. The UK military trauma registry was used to determine that the most frequently fractured bone was the Tibia and 65% of these fractures were open. Of these, 23% were surgically treated for infection in the first year and S. aureus bacteria was the causative organism in 60%. Infection was significantly associated with amputation or unplanned revision surgery. To further investigate open fracture infections in a controlled setting, an established rodent model of a stabilised, S. aureus contaminated, femoral defect was refined. This model was used to investigate the relationship between timing of treatment and infection. The results of this study indicate that delaying antibiotics administration has a greater effect on infection rates than delaying surgery and that early antibiotics can reduce the greater infection seen with surgical delay but not negate its effect entirely. Novel treatments with potential to reduce infection in open fractures were then evaluated. Chlorhexidine was found to be similar to saline for wound irrigation with respect to preventing infection. A novel biodegradable antibiotic gel proved to be superior at preventing infection in the model than the existing clinical standard local antibiotic delivery vehicle: bone cement (Polymethylmethacrylate) beads. Finally Bismuth Thiols were demonstrated to potentiate the effect of antibiotics in preventing infection

Wound infection following Hepatopancreatobiliary (HPB) surgery – a measure of predictive surgical and transmission factors and patient outcomes

Incidence of surgical site infections (SSIs) following hepatopancreatobiliary (HPB) surgery can be as high as 20 – 40 %. SSIs, particularly those caused by antimicrobial resistant (AMR) organisms, are a significant burden for both patients and the NHS. The aim of this study was to determine risk factors, incidence and the source of these infections and to measure how bacteria that can cause SSIs can form biofilms. Patients’ surgical sites were swabbed before and after surgery as well as different surfaces on the HPB ward. The bacteria were identified and their AMR was determined. Patient demographics, comorbidities and full blood counts were analysed to determine risk factors associated with SSIs. Biofilm assays (crystal violet, XTT and bacterial percentage coverage), using three of the isolates found on patients (Enterobacter cloacae, Enterococcus faecium and Staphylococcus haemolyticus) were conducted. The incidence of SSIs was 23.1 % and risk factors identified included bile leak, use of drains, pancreatic surgery, open surgery, long surgery and long hospital stay. Statistical analysis showed poor post-operative nutrition, post- operative pneumonia and return to the operating theatre as being significant risk factors for SSI. The bacteria found to cause SSIs were all gut commensals that were isolated from the drain fluid and not from the wound swabs, suggesting transmission occurred during surgery. High levels of multi-drug resistant (MDR) and extensively drug resistant (XDR) species were isolated, particularly XDR coagulase negative staphylococci. The surfaces with the most MDR and XDR species included most of the bathroom surfaces, the nurses’ phone and computer keyboard, bedside cabinet and the soap dispenser. In vitro biofilm assays showed that AMR could develop among bacteria in a polymicrobial biofilm and this could therefore occur within a polymicrobial SSI and hospital setting, making treatment more difficult. It is clear that more needs to be done to prevent SSIs following HPB surgery and that the hospital can still act as a reservoir for MDR and XDR bacteria

Factors Predicting Patient Outcomes in a UK Burn’s Unit; The influence of Acinetobacter Baumannii and the antimicrobial peptide LL-37 in burn wounds..

PhDSepsis and multi-organ failure are the most frequently reported causes of death in burn injuries. Their early identification allows therapies and resources to be targeted in a more effective and efficient way. Due to its frequent antibiotic drug resistance Acinetobacter baumannii (MRAB) is increasingly causing a problem in burns units. New strategies need to be found to combat infection and sepsis in the burn ICU. This study examines the potential of the Albumin Creatinine Ratio, a marker of systemic endothelial dysfunction in predicting outcomes, sepsis and multi-organ failure; the role of Acinetobacter in causing organ failure; and explores for the presence of the cathelicidin, LL-37 in the burn wound and examines it potential utility for treating infection and sepsis. It was found that ACR on admission and at 48 hours is predictive of patient outcomes and the development of sepsis, and may be of use predicting multi-organ failure. Multi-organ failure occurs more frequently in MRAB patients compared to those patients with drug sensitive Acinetobacter baumannii. The number of agency nursing staff and work intensity are possible contributing factors in MRAB acquisition. LL-37 has been found in both acute burn wounds as well as in the grafted healing burn wound and is active against drug resistant Acinetobacter baumannii. ACR can therefore identify those patients at risk of sepsis and may have a role in predicting multi-organ failure. MRAB acquisition in the burns intensive care unit is a significant cause for concern as patients are more likely to suffer from multi-organ failure as well as prolonging their hospital stay and resulting in poorer outcomes. LL-37 has many functions and importantly plays a role in the body’s innate immune system. In the era of increasing antibiotic resistance it may provide a novel therapeutic role in treating MRAB infection