Browsing by Author "Owen, Lucy"

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    Antimicrobial Activity of Ternary Essential Oil Mixtures in Topical Cosmetic Preparations Against Acne Vulgaris-Associated Bacteria.
    (Phytochemical Society of Europe, 2017) Owen, Lucy; Grootveld, M.; Arroo, R. R. J.; Ruiz-Rodado, Victor; Price, Penny; Laird, Katie
    Acne vulgaris is a chronic skin condition associated with overgrowth of Propionibacterium acnes and Staphylococcus epidermidis. Antibiotics are commonly prescribed to control acne; however, resistance has emerged, indicating the need for new antimicrobial therapies1. Several essential oils (EOs) are antimicrobial, including against antibiotic-resistant isolates, indicating that antimicrobial formulations may be developed using EOs2. The aim of this study was to develop a topical preparation incorporating EOs to control acne-associated bacteria, and compare its efficacy with the topical antibiotic formulations Dalacin T® and Stiemycin®. The antimicrobial activity of litsea (Litsea cubeba), rosewood (Aniba rosaeadora) and clove bud (Syzigum aromaticum) EOs was identified using the Kirby-Bauer disc diffusion method3 and the minimum inhibitory concentrations (MICs) were determined using a broth microdilution assay3.The MICs of clove bud and rosewood were 1.38 mg/ml against S. epidermidis and P. acnes. The MIC of litsea was 1.11 mg/mL against S. epidermidis and 2.23 mg/mL against P. acnes. The antimicrobial activity of a ternary combination of these EOs was further investigated using the checkerboard method with calculation of fractional inhibitory concentration index (FICI)4. Synergy was observed against both test species (FICI < 0.5). The EOs were characterised by both GC-MS and NMR. The antimicrobial efficacy of a cosmetic preparation containing the ternary EO combination was then compared to that of the current prescription medicines Dalacin T® and Stiemycin®. A combination of 0.53 mg/mL litsea, 0.11 mg/mL rosewood and 0.11 mg/mL clove bud EOs was formulated into a neroli herbal distillate with 0.5% (v/v) ethanol. Survival of P. acnes and S. epidermidis (types and clinical isolates) after a 24 h contact with the formulations was determined and compared to Dalacin T® and Stiemycin®. The formulation completely inhibited P. acnes (7 log10 reduction) and S. epidermidis (6 log10 reduction), and was equivalent in activity to Dalacin T® and Stiemycin®, including erythromycin-resistant isolates. The EO combination alone was either more antimicrobial (p ≤ 0.05) or equivalent in activity to the active ingredients of Dalacin T® and Stiemycin® (10 mg/mL clindamycin phosphate and 20 mg/mL erythromycin, respectively). The formulation may be useful as an alternative to antibiotic preparations for the control of acne-associated bacteria.
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    Antiviral plant-derived natural products to combat RNA viruses: Targets throughout the viral life cycle
    (Wiley, 2021-12-25) Owen, Lucy; Laird, Katie; Shivkumar, Maitreyi
    There is need for new effective antivirals, particularly in response to the development of antiviral drug resistance and emerging RNA viruses such as SARS-CoV-2. Plants are a significant source of structurally diverse bioactive compounds for drug discovery suggesting that plant-derived natural products could be developed as antiviral agents. This article reviews the antiviral activity of plant-derived natural products against RNA viruses, with a focus on compounds targeting specific stages of the viral life cycle. A range of plant extracts and compounds have been identified with antiviral activity, often against multiple virus families suggesting they may be useful as broad-spectrum antiviral agents. The antiviral mechanism of action of many of these phytochemicals is not fully understood and there are limited studies and clinical trials demonstrating their efficacy and toxicity in vivo. Further research is needed to evaluate the therapeutic potential of plant-derived natural products as antiviral agents.
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    Characterisation and screening of antimicrobial essential oil components against clinically important antibiotic-resistant bacteria using thin layer chromatography-direct bioautography hyphenated with GC-MS, LC-MS and NMR.
    (Wiley, 2018-10-02) Owen, Lucy; White, A.; Laird, Katie
    Introduction: The antimicrobial activity of many Essential Oils (EOs) is well established, indicating that EOs may be a source of compounds for antimicrobial drug development. Thin Layer Chromatography-Direct Bioautography (TLC-DB) can quickly identify antimicrobial components in complex mixtures and can be applied to the screening of EOs for lead compounds. Objectives: This study aimed to identify antimicrobial components of oregano, rosewood and cumin EOs against antibiotic-sensitive and -resistant bacteria using TLC-DB and a multi-faceted approach of GC-MS, LC-MS and NMR techniques to characterise bioactive compounds. The study also aimed to quantify the antimicrobial activity of bioactive compounds in order to evaluate their potential for the development of therapies against antibiotic-resistant bacteria. Materials and Methods: EOs were eluted on TLC plates and sprayed with a suspension of Staphylococcus aureus, Enterococcus faecium, Escherichia coli or Pseudomonas aeruginosa (antibiotic-sensitive and -resistant isolates). Zones of inhibition, visualised with iodonitrotetrazolium chloride, were subject to GC-MS, LC-MS and NMR to characterise the bioactive compounds. Results: Seven compounds were identified from the three EOs using GC-MS, while LC-MS and NMR failed to detect the presence of any further non-volatile or heat labile compounds. Carvacrol was most antimicrobial compound identified, with minimum inhibitory concentrations ranging 0.99-31.62 mM. Conclusion: The identified antimicrobial compounds present in oregano, rosewood and cumin EOs including carvacrol may be candidates for the development of novel antimicrobial therapies against antibiotic-resistant bacteria.
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    Developing a topical preparation containing a synergistic antimicrobial combination of essential oils for the control of acne vulgaris-associated bacteria.
    (Society for Applied Microbiology, 2015) Owen, Lucy; Arroo, R. R. J.; Price, Penny; Laird, Katie
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    Development of a Silver-Based Dual-Function Antimicrobial Laundry Additive and Textile Coating for the Decontamination of Healthcare Laundry
    (Wiley, 2020-09-11) Owen, Lucy; Laird, Katie
    Aims: To repurpose a silver-based antimicrobial textile coating product (Micro-Fresh 1911) as a dual-function antimicrobial laundry additive and textile coating. Methods and Results: Survival of Escherichia coli or Staphylococcus aureus type and clinical isolates in a domestic 40°C wash was assessed with and without soiling and biological detergent. Washing with 2% w/v silver additive (wash phase) reduced E. coli and S. aureus by 7.14-8.08 log10 and no cross-contamination was observed. Under dirty conditions, 0.5% silver additive in the rinse phase of a wash with biological detergent reduced E. coli and S. aureus by 7.98-8.40 log10 (0.00-1.42 log10 cross contamination). ISO 20645:2006 and ISO 20743:2013 methods were used to assess the antimicrobial activity of polycotton washed with 2% w/v silver additive against S. aureus and E. coli. The treated polycotton was antimicrobial against E. coli and S. aureus type and clinical isolates and remains active after at least one further wash cycle at 40°C or 73°C. Conclusions: The silver additive exhibits antimicrobial activity in a 40°C domestic wash, preventing cross contamination onto clean textiles and depositing an antimicrobial coating onto polycotton. Significance and Impact of Study: The survival of microorganisms on healthcare uniforms during domestic laundering presents a potential risk of contaminating the home, cross-contamination of other clothing within the wash and transmitting potential pathogens back into healthcare settings via contaminated uniforms. Silver may be useful as an antimicrobial laundry additive to decontaminate healthcare laundry washed at low temperatures in domestic and industrial settings, to therefore reduce the potential risk of transmitting microorganisms within the domestic and clinical environments.
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    Disinfection of laundry using low temperature validated ozone system, OTEX, against human coronavirus HCoV-OC43
    (2021-09-27) Owen, Lucy; Cripwell, Lucy; Hook, Jackie; Shivkumar, Maitreyi; Laird, Katie
    Introduction: The survival of the COVID-19 coronavirus (SARS-CoV-2) on textiles during laundering and in the presence of ozone is not well understood. In this study, the stability of a model human coronavirus (HCoV-OC43), on cotton textiles laundered using the OTEX validated ozone disinfection system was investigated. Method: Samples of cotton were contaminated with HCoV-OC43 and then washed using the Foul and Infected (40°C) cycle with laundry detergent and ozone. Sterile textile samples were washed in the same load to investigate potential cross contamination of HCoV-OC43. After washing, the number of infectious virus particles present on the cotton samples was determined. In a time-assay study, the stability of HCoV-OC43 in the presence of ozone over time was also investigated. Cotton samples contaminated with HCoV-OC43 were exposed to ozone in solution, for 3 and 6 minutes. The number of infectious virus particles remaining on the cotton after the wash was determined. For both the contamination tests and time-assay study, washes without detergent and ozone were included as controls. Results: No infectious virus was detected on contaminated cotton samples after washing using the OTEX Foul and Infected cycle, demonstrating at least 1.6 log10 reduction in HCoV-OC43 infectivity from the textile when using this wash cycle. No infectious virus was detected on sterile textile samples included in the washes, suggesting that there was no detectable cross-contamination occurring within the wash. In the time-assay study, HCoV-OC43 infectivity was reduced by at least 4.3 log10 within 6 minutes of washing in the presence of ozone – beyond that of the limit of detection. Discussion: These findings show that ozone contributes to the inactivation of HCoV-OC43. Overall, the results suggest that coronaviruses such as HCoV-OC43 are unlikely to persist within the OTEX laundering cycle.
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    Dual-Function Antimicrobial Laundry Supplement and Textile Coating for the Decontamination of Healthcare Laundry
    (2020-04-18) Owen, Lucy; Laird, Katie
    Background: In the UK nurses’ uniforms are domestically laundered, posing a threat of cross contamination of healthcare-associated infections. The UK Department of Health recommends washing uniforms at 60ºC, however nurses most commonly wash them at 40ºC. Bacteria survive on textiles washed at low temperatures; 4.28-4.62 log10 Escherichia coli and Staphylococcus aureus survived washing at 40ºC and cross contaminated other textiles in the wash. Antimicrobial laundry supplements could sanitise textiles and limit cross-contamination. A supplement that deposits an antibacterial coating onto textiles could also reduce contamination between washes. This study aimed to investigate a silver-based antimicrobial textile coating product (Micro-Fresh 1911) as a dual-use antimicrobial laundry supplement and textile coating. Materials/methods: Polycotton inoculated with 108 CFU/mL E. coli or S. aureus (type and clinical isolates) were washed with 2% Micro-Fresh 1911 in a domestic washing machine (40°C) and surviving microorganisms enumerated. Washes were conducted with and without soiling and biological detergent. Control washes were water alone. The antimicrobial activity of polycotton washed with Micro-Fresh 1911 at 40°C was assessed against S. aureus and E. coli using ISO 20645 and ISO 20743 methods. Controls were polycotton washed in water and textile padded with Micro-Fresh 2611. Results: Washing with Micro-Fresh 1911 reduced E. coli and S. aureus by 7.14-8.08 log10. No cells were recovered from sterile textile, whereas washing with water alone reduced E. coli and S. aureus by 2.21-4.25 log10 and resulted in 3.13-4.01 log10 CFU cross-contamination. Combining Micro-Fresh 1911 with biological detergent reduced E. coli and S. aureus by 5.56-6.65 log10. Fabric washed with Micro-Fresh 1911 was antimicrobial against E. coli and S. aureus type and clinical isolates according to ISO 20645 and ISO 20743. The antimicrobial coating remained after washing the fabric in water once at 40°C and 73°C. Conclusions: Micro-Fresh 1911 exibits antimicrobial activity in a 40ºC domestic wash and deposits an antimicrobial layer onto polycotton. Micro-Fresh could be employed as an antimicrobial laundering product to reduce microbial contamination of healthcare laundry washed at low temperatures.
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    The effect of climbing chalk powder on the infectivity of human coronavirus OC43
    (Wiley, 2021-02-22) Owen, Lucy; Laird, Katie; Shivkumar, Maitreyi
    There does not appear to be any studies in the published literature on the stability of SARS-CoV-2 within climbing chalk powder (magnesium carbonate and/or calcium carbonate), which has been hypothesized to pose a potential risk of fomite transmission of coronavirus disease 2019 (COVID-19) within climbing gyms. The aim of this study was to determine the infectivity of a model human coronavirus HCoV-OC43 in the presence of climbing chalk powder on a dry plastic surface. The stability of HCoV-OC43 on a plastic surface dusted with climbing chalk powders (magnesium carbonate, calcium carbonate or a blended chalk) was determined by titration on BHK-21 fibroblast cells. No chalk and no virus controls were included. HCoV-OC43 was stable on the plastic surface for 48 h. The stability of HCoV-OC43 was significantly (P≤0.05) reduced in the presence of magnesium carbonate, calcium carbonate and the chalk blend; the infectivity was reduced by ≥2.29 log10 50% tissue culture infective dose (TCID50) immediately upon on contact and by ≥2.46 log10 TCID50 within 1 h of contact. These findings suggest that the infectivity of coronaviruses is reduced by climbing chalk, limiting the risk of potential fomite transmission.
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    The Effect of Low Temperature Laundering and Detergents on the Survival of Escherichia coli and Staphylococcus aureus on Textiles Used in Healthcare Uniforms
    (Journal of Applied Microbiology, 2017-06-09) Riley, Kate; Williams, J.; Davis, A.; Shen, Jinsong; Laird, Katie; Owen, Lucy
    Aims: To determine the survival of Escherichia coli and Staphylococcus aureus on cotton and polyester and the effectiveness of low temperature laundering and detergents on the removal of microorganism from healthcare laundry. Methods and Results: Survival of E. coli and S. aureus on polyester or cotton was assessed over 3 weeks and the efficacy of a domestic wash (40°C and 60°C) and a range of detergents was also determined. Both bacteria were able to survive on cotton (5 log(10)) and polyester (0.28 log(10)) for up to 3 weeks. Laundering at 40°C resulted in a 3.5 log(10) removal of the initial 7.7 log(10) inoculum and some cross contamination to sterile fabrics (3 log(10). Increasing the temperature to 60°C resulted in the complete removal of the initial inoculum. Conclusions: This study shows that most of the microorganisms are removed at 40°C however, those cells still remaining may have the potential for further contamination to the clinical environment and patients Significance and Impact of Study: National Health Service (NHS) nurses are required to domestically launder their uniforms at 60°C to ensure safe removal of microorganisms, 33% of NHS staff questioned said they launder their uniforms at 40°C, which could potentially result in transmission of Hospital Acquired Infections (HAIs).
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    Evaluation of Current Healthcare Laundry Hygiene Monitoring Methodologies
    (2022-04-23) Owen, Lucy; Laird, Katie
    Background Disease outbreaks in healthcare facilities (e.g., Bacillus cereus) have been linked to contaminated linen, highlighting the importance of decontamination of healthcare textiles and infection control measures to prevent recontamination. The COVID-19 pandemic has raised further concerns around textile hygiene. Methods for monitoring microbial kill during healthcare laundering and post-laundering contamination are not standardised across Europe, leading to potential variation in validation outputs. For example, EN14065 accreditation requires microbiological monitoring, however no standard method is prescribed. Microbial kill is commonly validated by laundering inoculated textiles. Post-laundering hygiene monitoring tests can be destructive (elution) or non-destructive (e.g., swabbing). This study aims to evaluate common methods for detection of microbial contamination on textiles and measuring kill during industrial laundering processes. Methods Recovery of Escherichia coli, Staphylococcus aureus, Enterococcus faecium or Bacillus cereus spores (108, 102 and 101 CFU/ml) from 100% cotton was evaluated using different elution buffers (phosphate buffered saline or maximum recovery diluent with and without polysorbate 80), agitation methods (vortexing, stomaching, shaking by hand or with glass beads) and recovery agar (selective or non-selective). Recovery was compared to swabbing, RODAC plates and dip slides. Survival of E. faecium during a cold industrial wash with and without detergent was compared between loose swatches and those enclosed within cloth bags. Results Recovery of all test species was significantly (p≤0.05) greater using elution methods than non-destructive methods, while RODAC plates and dip slides were unquantifiable at 108 CFU/ml. Recovery was not significantly different between elution buffers or recovery agar. Shaking by hand was generally marginally more precise and efficient in microbial recovery. E. faecium was significantly (p≤0.05) reduced by industrial laundering with and without detergent; there was no significant difference when enclosed in cloth bags. Conclusions Surface testing methods have limited sensitivity compared to elution methods, suggesting that destructive methods are most appropriate for hygiene monitoring of laundered healthcare textiles. Swatch testing is confounded by a loss of microorganisms to dilution and agitation in the wash; further tests need to be developed to monitor the kill of microorganisms in the wash in order to develop a standardised test methodology to be used throughout global industrial laundries.
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    From formulation to in vivo model: A comprehensive study of a synergistic relationship between vancomycin, carvacrol and cuminaldehyde against Enterococcus faecium
    (Wiley, 2020-02-11) Owen, Lucy; Webb, Joseph P.; Green, Jeffrey; Smith, Laura J.; Laird, Katie
    Vancomycin Resistant Enterococcus faecium (VRE) has become endemic in healthcare settings, reducing treatment options for enterococcal infections. New antimicrobials for VRE infections are a high priority, but the development of novel antibiotics is time-consuming and expensive. Essential Oils (EOs) synergistically enhance the activity of some existing antibiotics, suggesting that EO-antibiotic combinations could re-sensitise resistant bacteria and maintain the antibiotic repertoire. The mechanism of re-sensitisation of bacteria to antibiotics by EOs is relatively understudied. Here, the synergistic interactions between carvacrol (1.98 mM) and cuminaldehyde (4.20 mM) were shown to re-establish susceptibility to vancomycin (0.031 mg/L) in VRE, resulting in bactericidal activity (4.73 log10 CFU/mL reduction). Gene expression profiling, coupled with β-galactosidase leakage and salt tolerance assays suggested that cell envelope damage contributes to the synergistic bactericidal effect against VRE. The EO-vancomycin combination was also shown to kill clinical isolates of VRE (2.33-5.25 log10 CFU/mL reduction) and stable resistance did not appear to develop even after multiple passages. The in vivo efficacy of the EO-vancomycin combination was tested in a Galleria mellonella larvae assay; however no antimicrobial action was observed, indicating that further drug development is required for the EO-vancomycin combination to be clinically useful for treatment of VRE infections.
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    Healthcare worker knowledge and attitudes towards uniform laundering during the COVID-19 pandemic
    (Elsevier, 2021-12-29) Owen, Lucy; Apps, Lindsay; Stanulewicz, Natalia; Hall, Andrew; Laird, Katie
    Background: The COVID-19 pandemic raised concerns towards domestic laundering of healthcare worker (HCW) uniforms; this is common practice in countries such as the United Kingdom (UK) and United States. Previous research suggested 4-32% of nurses did not adhere to laundry policies, which could be an infection control risk. This study aimed to investigate the knowledge and attitudes of UK healthcare workers towards domestic laundering of uniforms during the COVID-19 pandemic. Methods: Online and paper questionnaires were distributed to HCWs and nursing students who regularly wear uniforms. Differences in knowledge between HCWs were analysed by Chi-squared tests and attitudes were examined using exploratory factor analysis. Results: 86% of participants (n=1099 of 1277) laundered their uniforms domestically. Respondents were confident in laundering their uniforms appropriately (71%), however 17% failed to launder at the recommended temperature (60°C). Most participants (68%) would prefer their employer launder their uniforms, with mixed negative emotions towards domestic laundering. Limited provision of uniforms and changing/storage facilities were a barrier to following guidelines. Conclusion: Most HCWs domestically launder their uniforms, despite a preference for professional laundering. One-fifth of HCWs deviated from the UK National Health Service uniform guidelines; onsite changing facilities were the most significant barrier towards adherence.
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    Heterogeneous Fenton’s-like Catalyst Potentiation of Hydrogen Peroxide Disinfection: an Investigation into Mechanisms of Action
    (Oxford University Press, 2023-02-16) Sewell, S; Owen, Lucy; Huddersman, Katherine; Laird, Katie; Walsh, Susannah
    Aims This study aimed to establish the mechanisms of action (MOA) of a novel surface-functionalized polyacrylonitrile (PAN) catalyst, which was previously shown to have potent antimicrobial activity in conjunction with hydrogen peroxide (H2O2). Methods and results Bactericidal activity was determined using a disinfectant suspension test. The MOA was investigated by measuring the loss of 260 nm absorbing material, membrane potential, permeability assays, analysis of intra- and extracellular ATP and pH, and tolerance to sodium chloride and bile salts. The catalyst lowered sub-lethal concentrations of H2O2 from 0.2 to 0.09%. H2O2 ± 3 g PAN catalyst significantly (P ≤ 0.05) reduced sodium chloride and bile salt tolerance, suggesting the occurance of sublethal cell membrane damage. The catalyst significantly increased (P ≤ 0.05) N-Phenyl-l-Napthylamine uptake (1.51-fold) and leakage of nucleic acids, demonstrating increased membrane permeability. A significant (P ≤ 0.05) loss of membrane potential (0.015 a.u.), coupled with pertubation of intracellular pH homeostasis and depletion of intracellular ATP, suggests potentiation of H2O2-mediated cell membrane damage. Conclusions This is the first study to investigate the catalyst’s antimicrobial mechanism of action, with the cytoplasmic membrane being a target for cellular injury.
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    Investigation of the stability and risks of fomite transmission of human coronavirus OC43 on leather
    (Oxford University Press, 2021-08-30) Shivkumar, Maitreyi; Adkin, Pat; Owen, Lucy; Laird, Katie
    Limited research exists on the potential for leather to act as a fomite of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or endemic coronaviruses including human coronavirus (HCoV) OC43; this is important for settings such as the shoe manufacturing industry. Antiviral coating of leather hides could limit such risks. This study aimed to investigate the stability and transfer of HCoVOC43 on different leathers, as a surrogate for SARS-CoV-2, and assess the antiviral efficacy of a silver-based leather coating. The stability of HCoV-OC43 (6.6 log10) on patent, full-grain calf, corrected grain finished and nubuck leathers (silver additive-coated and uncoated) was measured by titration on BHK-21 cells. Transfer from leather to cardboard and stainless steel was determined. HCoV-OC43 was detectable for 6 h on patent, 24 h on finished leather and 48 h on calf leather; no infectious virus was recovered from nubuck. HCoV-OC43 transferred from patent, finished and calf leathers onto cardboard and stainless steel up to 2 h post-inoculation (≤3.1–5.5 log10), suggesting that leathers could act as fomites. Silver additive-coated calf and finished leathers were antiviral against HCoV-OC43, with no infectious virus recovered after 2 h and limited transfer to other surfaces. The silver additive could reduce potential indirect transmission of HCoV-OC43 from leather.
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    Knowledge, attitudes and behaviours of UK healthcare workers towards uniform laundering polices during the COVID-19 pandemic
    (2021-07-09) Owen, Lucy; Apps, Lindsay; Stanulewicz, Natalia; Hall, Andrew; Laird, Katie
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    MESHGuide on COVID19: Schooling in a pandemic
    (MESHGuide, 2020) Younie, Sarah; Hall, Stephen; Laxton, Debra; Owen, Lucy; Laird, Katie
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    Microemulsification of essential oils for the development of antimicrobial and mosquito repellent functional coatings for textiles
    (Journal of Applied Microbiology, 2021-05-22) Soroh, Anita; Owen, Lucy; Rahim, Noor; Masania, Jinit; Abioye, Amos; Qutachi, Omar; Goodyer, Larry; Shen, Jinsong; Laird, Katie
    Aims: To develop an essential oil (EO)-loaded textile coating using an environmentally-friendly microemulsion technique to achieve both antimicrobial and mosquito repellent functionalities. Methods and Results: Minimum inhibitory concentrations and fractional inhibitory concentrations of litsea, lemon and rosemary EOs were determined against Staphylococcus aureus, Escherichia coli, Staphylococcus epidermidis, Pseudomonas aeruginosa and Trichophyton rubrum. A 1:2 mixture of litsea and lemon EOs inhibited all the microorganisms tested and was incorporated into chitosan-sodium alginate assembly by a microemulsification process. The EO-loaded microemulsions were applied to cotton and polyester fabrics using a soak-pad-dry method. The textile challenge tests demonstrated 7-8 log10 reductions of S. epidermidis, S. aureus and E. coli after 24 h and T. rubrum after 48 h. Aedes aegypti mosquito repellency was also assessed which demonstrated 71.43% repellency compared to 52.94% by neat EO-impregnated cotton. Conclusions: Textiles treated with the litsea and lemon EO microemulsion showed strong antimicrobial activity against the skin associated microorganisms E. coli, S. aureus, S. epidermidis and T. rubrum and potential mosquito repellent properties. Significance of Study: EOs could be useful for the development of natural, environmentally-friendly functional textiles to protect textiles and users from microbial contamination in addition to possessing other beneficial properties such as mosquito repellency.
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    A multi-faceted approach to determining the efficacy of metal and metal oxide nanoparticles against bacterial biofilms
    (Journal of Bionanoscience, 2018-10-01) Tejpal, Jyoti; Cross, R. B. M.; Owen, Lucy; Paul, Shashi; Jenkins, R. O.; Armitage, David; Laird, Katie
    Antibacterial efficacy of nanoscale silver, copper (II) oxide and zinc oxide were assessed against Pseudomonas aeruginosa and Staphylococcus aureus biofilms in solution and on surfaces. Using a Center for Disease Control biofilm reactor, minimum biofilm reduction concentrations, the coefficient of determination (R2) and log(10) reductions were determined. Atomic absorption spectroscopy, scanning electron microscopy and confocal laser scanning microscopy were used to assess the disruption of the biofilms. The efficacy of thin films of zinc oxide and silver deposited via magnetron sputtering and thermal evaporation respectively was also assessed. Minimum biofilm reduction concentrations of zinc oxide or silver nanoparticles were 256 or 50 µg/ml for P. aeruginosa and 16 or50 µg/ml for S. aureus respectively. When tested in combination the nanoparticles concentrations were at least halved resulting in significant (p ≤0.05) biofilm reductions of 3.77 log(10) - 3.91 log(10). Biofilm growth on thin films resulted in reductions of up to 1.82 log(10). The results suggest that nanoparticle suspensions and thin films of zinc oxide and may have potential as antimicrobial treatments for hard to eliminate biofilms in a clinical environment.
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    A Multifactorial Comparison of Ternary Combinations of Essential Oils in Topical Preparations to Current Antibiotic Prescription Therapies for the Control of Acne Vulgaris-Associated Bacteria.
    (2017-01-26) Laird, Katie; Owen, Lucy; Ruiz-Rodado, Victor; Price, Penny; Grootveld, M.; Arroo, R. R. J.
    Acne vulgaris, a chronic condition associated with overgrowth of Propionibacterium acnes and Staphylococcus epidermidis, is commonly treated with antibiotics. However, the emergence of antibiotic resistance has resulted in a need for alternative therapies. The aim of this study is to develop a topical preparation incorporating Essential Oils (EOs) for use against acne-associated bacteria and assess its efficacy against prescription therapies Dalacin T and Stiemycin. Antimicrobial screening of rosewood, clove bud and litsea EOs was conducted and interactions between binary and ternary combinations determined against P. acnes and S. epidermidis (type and clinical isolates) using Minimum Inhibitory Concentrations (MICs) and Fractional Inhibitory Concentrations (FICs). The EOs were characterised by both GC-MS and NMR. A combination of 0.53 mg/ml litsea, 0.11 mg/ml rosewood and 0.11 mg/ml clove bud were formulated into herbal distillates and compared to Dalacin T and Stiemycin against antibiotic sensitive and resistant isolates (erythromycin). The distillate with EO had synergistic activity against P. acnes (7log10 reduction) and indifferent activity against S. epidermidis, (6log10 reduction), antimicrobial activity was either significantly (p ≤ 0.05) more antimicrobial or equivalent to that of Dalacin T and Stiemycin. This formulation may serve as a valuable alternative for the control of acne vulgaris-associated bacteria.