Publications by authors named "Mark D P Willcox"

196 Publications

Controlled bimatoprost release from graphene oxide laden contact lenses: In vitro and in vivo studies.

Colloids Surf B Biointerfaces 2021 Sep 2;208:112096. Epub 2021 Sep 2.

School of Optometry and Vision, University of New South Wales, Sydney, New South Wales, 2052, Australia.

Ocular drug delivery using contact lenses may be able to substitute for eye drop therapy. However, issues with hydrophobic drugs (like bimatoprost that is used to treat glaucoma) such as low drug uptake using a simple soaking method into preformed contact lenses and alteration in the swelling and transmittance of lenses restricts the application for drug delivery. This research uses graphene oxide (GO) to control the release of bimatoprost from contact lenses along with improvements in the drug uptake, and lens swelling and transmittance. GO was loaded into silicone hydrogel contact lenses by adding the GO at the same time as lenses were polymerized. These lenses were soaked in bimatoprost. Alternatively contact lenses, either with or without GO, were produced by adding bimatoprost during lens polymerization. GO improved contact lens swelling due to its water binding capacity and lens transmittance due to the molecular dispersion of bimatoprost on the surface of the GO which prevented the local precipitation of the drug. The bimatoprost uptake was not improved in the presence of GO. However, its in vitro release profile was improved. Adding bimatoprost and GO at the same time as lenses were polymerized (DL-GO-BMT) significantly decreased the loss of drug during extraction and sterilization in comparison to contact lenses (DL-BMT) without GO. As the amount of GO was increased, the DL-GO-BMT lenses showed a significant decrease in the burst and cumulative release of bimatoprost. Ocular irritation and histopathology reports demonstrated the safety of GO contact lens. The in vivo pharmacokinetic studies in the rabbit tear fluid showed significant improvement in mean residence time (MRT) and area under the curve (AUC) with DL-GO-0.2 μg-BMT-100 contact lens in comparison to eye drop solution. The study demonstrated that the addition of GO to contact lenses can control the release of bimatoprost as well as improved the lens swelling and transmittance. However, further optimization is needed to modulate the release of drug within the therapeutic level to manage glaucoma.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.colsurfb.2021.112096DOI Listing
September 2021

Advances and challenges in the nanoparticles-laden contact lenses for ocular drug delivery.

Int J Pharm 2021 Sep 13:121090. Epub 2021 Sep 13.

School of Optometry and Vision, University of New South Wales, Sydney, New South Wales 2052, Australia.

The delivery of drugs that target ocular tissues is challenging due to the physiological barriers of the eye like tear dilution, nasolacrimal drainage, blinking, tear turnover rate and low residence time Drug-laden contact lenses can be a possible solution to overcome some of these challenges. Nanoparticles are being extensively studied as novel systems for loading drugs into therapeutic contact lenses. The versatile features of the organic and inorganic nanoparticles and their diverse physicochemical properties make it possible to load and sustain drug release from the contact lenses. Nevertheless, several issues remains to be solved before its clinical application and commercialization such as changes in contact lens swelling (water content), transmittance, protein adherence, surface roughness, tensile strength, ion and oxygen permeability and drug leaching during contact lens manufacture. However, clinical studies demonstrated the potential of therapeutic contact lenses to manage the scientific, commercial and regulatory challenges to make its place in the market. This review highlights the different methodologies used to fabricate nanoparticle-laden contact lenses and highlights the major advances and challenges to commercialization.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijpharm.2021.121090DOI Listing
September 2021

The Autofluorescence Patterns of and : Effects of Antibiotics and Tetracaine.

Pathogens 2021 Jul 14;10(7). Epub 2021 Jul 14.

School of Optometry and Vision Science, University of New South Wales, Sydney 2052, Australia.

Keratitis (AK) can lead to substantial vision loss and morbidity among contact lens wearers. Misdiagnosis or delayed diagnosis is a major factor contributing to poor outcomes of AK. This study aimed to assess the effect of two antibiotics and one anaesthetic drug used in the diagnosis and nonspecific management of keratitis on the autofluorescence patterns of and two common bacteria that may also cause keratitis. ATCC 30868, ATCC 9027, and ATCC 6538 were grown then diluted in either PBS (bacteria) or ¼ strength Ringer's solution () to give final concentrations of 0.1 OD at 660 nm or 10 cells/mL. Cells were then treated with ciprofloxacin, tetracycline, tetracaine, or no treatment (naïve). Excitation-emission matrices (EEMs) were collected for each sample with excitation at 270-500 nm with increments in 5 nm steps and emission at 280-700 nm at 2 nm steps using a Fluoromax-4 spectrometer. The data were analysed using MATLAB software to produce smoothed color-coded images of the samples tested. exhibited a distinctive fluorescence pattern compared to bacteria. The addition of antibiotics and anaesthetic had variable effects on autofluorescence. Tetracaine altered the fluorescence of all three microorganisms, whereas tetracycline did not show any effect on the fluorescence. Ciprofloxacin produced changes to the fluorescence pattern for the bacteria, but not . Fluorescence spectroscopy was able to differentiate from in vitro. There is a need for further assessment of the fluorescence pattern for different strains of and bacteria. Additionally, analysis of the effects of anti-amoebic drugs on the fluorescence pattern of and bacteria would be prudent before in vivo testing of the fluorescence diagnostic approach in the animal models.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/pathogens10070894DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8308758PMC
July 2021

Polyphenylglyoxamide-Based Amphiphilic Small Molecular Peptidomimetics as Antibacterial Agents with Anti-Biofilm Activity.

Int J Mol Sci 2021 Jul 8;22(14). Epub 2021 Jul 8.

School of Chemistry, The University of New South Wales, Sydney, NSW 2052, Australia.

The rapid emergence of drug-resistant bacteria is a major global health concern. Antimicrobial peptides (AMPs) and peptidomimetics have arisen as a new class of antibacterial agents in recent years in an attempt to overcome antibiotic resistance. A library of phenylglyoxamide-based small molecular peptidomimetics was synthesised by incorporating an -alkylsulfonyl hydrophobic group with varying alkyl chain lengths and a hydrophilic cationic group into a glyoxamide core appended to phenyl ring systems. The quaternary ammonium iodide salts and showed excellent minimum inhibitory concentration (MIC) of 4 and 8 μM (2.9 and 5.6 μg/mL) against , respectively, while the guanidinium hydrochloride salt showed an MIC of 16 μM (8.5 μg/mL) against Additionally, the quaternary ammonium iodide salt inhibited 70% biofilm formation at 16 μM. It also disrupted 44% of pre-established biofilms at 32 μM and 28% of pre-established biofilms 64 μM, respectively. A cytoplasmic membrane permeability study indicated that the synthesised peptidomimetics acted via disruption and depolarisation of membranes. Moreover, the quaternary ammonium iodide salts and were non-toxic against human cells at their therapeutic dosages against .
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms22147344DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8303886PMC
July 2021

Effect of Antimicrobial Contact Lenses on Corneal Infiltrative Events: A Randomized Clinical Trial.

Transl Vis Sci Technol 2021 06;10(7):32

School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.

Purpose: To determine whether Mel4-coated antimicrobial contact lenses (MACLs) can reduce the incidence of corneal infiltrative events (CIEs) during extended wear.

Methods: A prospective, randomized, double-masked, single-center, contralateral, extended contact lens wear clinical trial was conducted with 176 subjects. Each participant was randomly assigned to wear a MACL in one eye and an uncoated control contact lens in the contralateral eye or an extended-wear biweekly disposable modality for 3 months. The main outcome measures were the incidence of CIEs per 100 eye-months, identification of the microbial types colonizing the contact lenses or eyes at the time of the CIEs, and their susceptibility to Mel4.

Results: Nine participants (5.1%) experienced unilateral CIEs; six participants had contact lens acute red eye, and three participants had infiltrative keratitis. The incidence rate for CIEs (0.4 events per 100 participant months; 1.7%) in the Mel4-coated lenses (test) was 69% less than that of the control lenses (1.3 events per 100 participant months; 3.4%; P = 0.29). All Gram-negative bacteria isolated from lenses and lids of participants with CIEs (Citrobacter diversus, Acinetobacter haemolyticus, and Acinetobacter lwoffii) were susceptible to Mel4 peptide; minimum inhibitory concentrations ranged from 15.6 to 62.5 µg/mL. Reduction of adhesion of these bacteria by Mel4-coated lenses ranged from 2.1 to 2.2 log10 colony-forming units/lens.

Conclusions: MACLs had the capacity to reduce CIEs by at least 50% compared with uncoated control lenses during extended wear over 3 months; however, due to the relatively low rates of CIEs, the reduction was not statistically different compared with control lenses.

Translational Relevance: This study provides evidence that antimicrobial contact lenses have the potential to reduce the incidence of corneal infiltrative events during extended wear.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1167/tvst.10.7.32DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8254012PMC
June 2021

Effect of Hygiene Procedures on Lens Case Contamination with Povidone-Iodine or Multipurpose Disinfecting Solutions.

Optom Vis Sci 2021 Jun;98(6):563-569

School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia.

Significance: A multipurpose disinfecting solution (MPDS), which contains povidone-iodine (PI) as a disinfectant, has high disinfecting efficacy not only on planktonic bacterium but also on the case biofilms. The addition of case hygiene practice removed more bacteria from cases than MPDS alone.

Purpose: This study compared the ability of two MPDSs, one containing PI and another containing polyaminopropyl biguanide and polyquaternium, to reduce bacterial numbers in solution or adhered to the cases following case hygiene procedures.

Methods: Bacterial strains (Delftia acidovorans, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Serratia marcescens, Staphylococcus aureus, and Staphylococcus epidermidis) were exposed to the MPDSs for the recommended disinfection times, and the viable number evaluated according to ISO 14729. Cases were inoculated with bacterial strains and incubated for 24 hours to allow for biofilm formation. Cases were disinfected with both disinfecting solutions for 4 hours and rinsed, followed by recapping or air-drying, or tissue-wiping and air-drying for 18 hours. The number of survivors was counted using standard culture techniques.

Results: Both products exceeded the recommended 3-log reduction against planktonic bacteria. Regarding biofilm, after rinsing and recapping wet, the numbers of D. acidovorans (mean difference [95% confidence interval] log10 colony-forming units per case, -2.9 [0.8 to -4.6], P < .01), P. aeruginosa (-2.0 [0.5 to -3.1], P < .01), S. marcescens (-1.7 [0.8 to -3.5], P < .05), and S. epidermidis (-2.1 [0.6 to -3.5], P < .05) in PI cases were significantly lower than in the dual-disinfectant MPDS storage cases. After air-drying, the PI storage cases had significantly lower numbers of S. maltophilia (-2.6 [0.6 to -4.0], P < .01), D. acidovorans (-1.6 [0.7 to -3.3], P < .05), and S. aureus (-1.6 [0.7 to -3.1], P < .05). The addition of tissue-wiping reduced the bacterial numbers in the MPDS storage cases to levels in the PI storage cases.

Conclusions: Contact lens users should be recommended to tissue-wipe and air-dry their lens storage cases after disinfection with regular MPDS.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/OPX.0000000000001700DOI Listing
June 2021

The role of nitric oxide in ocular surface physiology and pathophysiology.

Ocul Surf 2021 Jul 30;21:37-51. Epub 2021 Apr 30.

School of Optometry & Vision Science, University of New South Wales, Australia.

Nitric oxide (NO) has a wide array of biological functions including the regulation of vascular tone, neurotransmission, immunomodulation, stimulation of proinflammatory cytokine expression and antimicrobial action. These functions may depend on the type of isoform that is responsible for the synthesis of NO. NO is found in various ocular tissues playing a pivotal role in physiological mechanisms, namely regulating vascular tone in the uvea, retinal blood circulation, aqueous humor dynamics, neurotransmission and phototransduction in retinal layers. Unregulated production of NO in ocular tissues may result in production of toxic superoxide free radicals that participate in ocular diseases such as endotoxin-induced uveitis, ischemic proliferative retinopathy and neurotoxicity of optic nerve head in glaucoma. However, the role of NO on the ocular surface in mediating physiology and pathophysiological processes is not fully understood. Moreover, methods used to measure levels of NO in the biological samples of the ocular surface are not well established due to its rapid oxidation. The purpose of this review is to highlight the role of NO in the physiology and pathophysiology of ocular surface and propose suitable techniques to measure NO levels in ocular surface tissues and tears. This will improve the understanding of NO's role in ocular surface biology and the development of new NO-based therapies to treat various ocular surface diseases. Further, this review summarizes the biochemistry underpinning NO's antimicrobial action.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jtos.2021.04.007DOI Listing
July 2021

Novel Seleno- and Thio-Urea Containing Dihydropyrrol-2-One Analogues as Antibacterial Agents.

Antibiotics (Basel) 2021 Mar 19;10(3). Epub 2021 Mar 19.

School of Chemistry, The University of New South Wales, Sydney, NSW 2052, Australia.

The quorum sensing (QS) system in multi-drug-resistant bacteria such as is primarily responsible for the development of antibiotic resistance and is considered an attractive target for antimicrobial drug discovery. In this study, we synthesised a series of novel selenourea and thiourea-containing dihydropyrrol-2-one (DHP) analogues as LasR antagonists. The selenium DHP derivatives displayed significantly better quorum-sensing inhibition (QSI) activities than the corresponding sulphur analogues. The most potent analogue efficiently inhibited the QS system by 81% at 125 µM and 53% at 31 µM. Additionally, all the compounds were screened for their minimum inhibitory concentration (MIC) against the Gram-positive bacterium , and interestingly, only the selenium analogues showed antibacterial activity, with and being the most potent with a MIC of 15.6 µM.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/antibiotics10030321DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8003518PMC
March 2021

American Academy of Optometry Microbial Keratitis Think Tank.

Optom Vis Sci 2021 03;98(3):182-198

School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia.

Significance: Think Tank 2019 affirmed that the rate of infection associated with contact lenses has not changed in several decades. Also, there is a trend toward more serious infections associated with Acanthamoeba and fungi. The growing use of contact lenses in children demands our attention with surveillance and case-control studies.

Purpose: The American Academy of Optometry (AAO) gathered researchers and key opinion leaders from around the world to discuss contact lens-associated microbial keratitis at the 2019 AAO Annual Meeting.

Methods: Experts presented within four sessions. Session 1 covered the epidemiology of microbial keratitis, pathogenesis of Pseudomonas aeruginosa, and the role of lens care systems and storage cases in corneal disease. Session 2 covered nonbacterial forms of keratitis in contact lens wearers. Session 3 covered future needs, challenges, and research questions in relation to microbial keratitis in youth and myopia control, microbiome, antimicrobial surfaces, and genetic susceptibility. Session 4 covered compliance and communication imperatives.

Results: The absolute rate of microbial keratitis has remained very consistent for three decades despite new technologies, and extended wear significantly increases the risk. Improved oxygen delivery afforded by silicone hydrogel lenses has not impacted the rates, and although the introduction of daily disposable lenses has minimized the risk of severe disease, there is no consistent evidence that they have altered the overall rate of microbial keratitis. Overnight orthokeratology lenses may increase the risk of microbial keratitis, especially secondary to Acanthamoeba, in children. Compliance remains a concern and a significant risk factor for disease. New insights into host microbiome and genetic susceptibility may uncover new theories. More studies such as case-control designs suited for rare diseases and registries are needed.

Conclusions: The first annual AAO Think Tank acknowledged that the risk of microbial keratitis has not decreased over decades, despite innovation. Important questions and research directions remain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/OPX.0000000000001664DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8075116PMC
March 2021

Ocular microbiota and lens contamination following Mel4 peptide-coated antimicrobial contact lens (MACL) extended wear.

Cont Lens Anterior Eye 2021 Mar 4:101431. Epub 2021 Mar 4.

School of Optometry and Vision Science, UNSW Sydney, Australia.

Purpose: The purpose of this study was to investigate the effect of Mel4 antimicrobial peptide-coated contact lenses (MACL) on the microbiota of the conjunctiva and lenses during three months of extended wear.

Methods: One hundred and seventy-six participants were recruited into a randomised, contralateral, double masked, biweekly extended wear MACL and uncoated control lens trial. At the one month and 3-month visit, the conjunctival microbiota was sampled using sterile cotton swabs and contact lenses were collected aseptically. Standard microbiological procedures were employed for culture of the swabs and contact lenses and identification of the isolated microorganisms.

Results: Gram-positive bacteria (predominantly coagulase-negative staphylococci) were the most frequently isolated microbes from both contact lenses and conjunctiva. There was no difference in the frequency of isolation of most bacteria or fungi from the conjunctival swabs of eyes wearing either MACL or control lenses. The only exception was a higher frequency of eyes harbouring Staphylococcus arlettae when wearing control lenses (5%) versus MACL (<1%) (p = 0.002). There was no significant difference in the frequency of microbes isolated from MACL or control contact lenses. There were also no differences between lens types in the frequency of isolation of >1 microbial type per sampling occasion for either conjunctiva swabs or contact lenses.

Conclusion: MACL wear did not change the conjunctival microbiota during extended wear, and the types of microbes isolated from MACL were similar to those isolated from control lenses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.clae.2021.02.017DOI Listing
March 2021

Development of antibiotic resistance in the ocular Pseudomonas aeruginosa clone ST308 over twenty years.

Exp Eye Res 2021 04 18;205:108504. Epub 2021 Feb 18.

School of Optometry and Vision Science, UNSW, Sydney, Australia. Electronic address:

Corneal infection caused by a bacteria Pseudomonas aeruginosa is common cause of ocular morbidity. Increasing antibiotic resistance by ocular P. aeruginosa is an emerging concern. In this study the resistome of ocular isolates of Pseudomonas aeruginosa clone ST308 isolated in India in 1997 (PA31, PA32, PA33, PA35 and PA37) and 2018 (PA198 and PA219) were investigated. All the isolates of ST308 had >95% nucleotide similarity. The isolates from 2018 had larger genomes, coding sequences, accessory and pan genes compared to the older isolates from 1997. The 2018 isolate PA219 was resistant to all antibiotics except polymyxin B, while the 2018 isolate PA198 was resistant to ciprofloxacin, levofloxacin, gentamicin and tobramycin. Among the isolates from 1997, five were resistant to gentamicin, tobramycin and ciprofloxacin, four were resistant to levofloxacin while two were resistant to polymyxin B. Twenty-four acquired resistance genes were present in the 2018 isolates compared to 11 in the historical isolates. All isolates contained genes encoding for aminoglycoside (aph(6)-Id, aph(3')-lIb, aph(3″)-Ib), beta-lactam (blaPAO), tetracycline (tet(G)), fosfomycin (fosA), chloramphenicol (catB7), sulphonamide (sul1), quaternary ammonium (qacEdelta1) and fluoroquinolone (crpP) resistance. Isolate PA198 possessed aph(3')-VI, rmtD2, qnrVC1, blaOXA-488, blaPME-1, while PA219 possessed aadA1, rmtB, qnrVC1, aac(6')-Ib-cr, blaTEM-1B, blaVIM-2, blaPAO-1, mph(E), mph(A), msr(E). In both recent isolates qnrVC1 was present in Tn3 transposon. In 219 blaTEM-1 was carried on a transposon and blaOXA-10 on a class 1 integron. There were no notable differences in the number of single nucleotide polymorphisms, but recent isolates carried more insertions and deletions in their genes. These findings suggest that genomes of P. aeruginosa ocular clonal strains with >95% nucleotide identity isolated twenty years apart had changed over time with the acquisition of resistance genes. The pattern of gene mutations also varied with more insertions and deletions in their chromosomal genes which confer resistance to antibiotics.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.exer.2021.108504DOI Listing
April 2021

Developing evidence-based guidance for the treatment of dry eye disease with artificial tear supplements: A six-month multicentre, double-masked randomised controlled trial.

Ocul Surf 2021 04 2;20:62-69. Epub 2021 Jan 2.

Optometry and Vision Science Research Group, Aston University, Birmingham, UK.

Purpose: To assess the six-month therapeutic profiles of lipid and non-lipid-based artificial tear supplements in managing dry eye disease (DED).

Methods: Ninety-nine participants fulfilling the TFOS DEWS II diagnostic criteria for DED (64% females; mean ± SD age, 44 ± 16 years) were enrolled in a prospective, multicentre, double-masked, parallel group, randomised controlled trial. Participants instilled lipid-based nanoemulsion drops or non-lipid-based aqueous drops for six months, at least four times daily. Symptomology, tear film and ocular surface characteristics were assessed at Days 0, 30, 60, 90, 120, 150 and 180.

Results: Sustained reductions in OSDI, DEQ-5, and SANDE symptom scores from baseline were observed from Day 30 onwards in both groups (all p < 0.05) and decreased superior lid wiper epitheliopathy grades from Day 60 onwards (all p ≤ 0.01). Improvements in non-invasive tear film breakup time, and sodium fluorescein and lissamine green staining scores followed from Day 120 onwards in both groups (all p < 0.05). Tear lipid layer grades increased from Day 90 onwards only with the lipid-based drops, and with significantly greater improvement in those with suboptimal lipid layer thickness at baseline (grade ≤3; p = 0.02). By Day 180, 19% of participants no longer fulfilled the diagnostic criteria for DED.

Conclusions: Over a six-month treatment period, improvements in dry eye symptomology preceded tear film and ocular surface changes with regular use of both lipid and non-lipid-based artificial tear supplements. Both formulations addressed most mild-to-moderate forms of aqueous deficient and evaporative DED, while evaporative cases benefitted preferentially from lipid-based supplementation. This represents a first step towards mapping DED therapeutic strategies according to disease subtype and severity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jtos.2020.12.006DOI Listing
April 2021

Interaction of the surface bound antimicrobial peptides melimine and Mel4 with .

Biofouling 2020 10 8;36(9):1019-1030. Epub 2020 Nov 8.

School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.

Melimine and Mel4 are cationic antimicrobial peptides which can resist biofilm development once bound to biomaterials. The aim of the current study was to determine the mode of action of bound melimine and Mel4 against The peptides were covalently attached to glass using an azidobenzoic acid linker. The amount of attached peptides was confirmed by XPS and amino acid analysis and their covalent attachment by SDS extraction. The release of autolysins after interaction of with immobilized peptides was determined in cell free supernatants. The interaction of immobilized peptides with lipoteichoic acid was confirmed by ELISA. Membrane damage by surface bound peptides was assessed using DiSC(3)-5 (membrane potential sensitive), Syto-9 (membrane permeable) and PI (membrane impermeable) dyes with fluorescence microscopy. Release of ATP and nucleic acids (DNA/RNA) was measured in the surrounding fluid. Attachment of the peptides resulted in increased N% for melimine (5.4 ± 1.8%) and for Mel4 (4.8 ± 1.8%). The concentrations of immobilised amino acids were 0.297 nmole for melimine and 0.358 nmole for Mel4. SDS extraction released < 15% of peptides from the glass. The immobilized peptides bound ≥ 4 times more LTA than control surfaces. More autolysins (8 ± 2%;  = 0.026) were released from Mel4 than melimine or control surfaces. Membrane depolarization occurred at 15 min and was associated with a reduction in bacterial viability ≥ 37% for both peptides ( < 0.001). Disruption of the membrane potential resulted in loss of ATP from melimine (0.9 ± 0.4 nM) or Mel4 (0.6 ± 0.3 nM) coated surfaces compared to control ( < 0.001). Melimine coatings yielded 27 ± 11% ( = 0.026) and Mel4 gave 17 ± 12% ( = 0.150) PI stained cells after 4 h. DNA/RNA was released only by melimine coatings (2.1 ± 0.1 times;  = 0.011) compared to process control at 6 h. Both bound peptides resulted in the release of ATP, but only melimine released DNA/RNA while Mel4-coating resulted in the release of autolysins. Since the mode of action of melimine and Mel4 relate to the cell surface, they have potential for the development of infection-resistant implants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/08927014.2020.1843638DOI Listing
October 2020

Risk Factors for Contact Lens-Related Microbial Keratitis and Associated Vision Loss in a South Indian Population.

Eye Contact Lens 2021 Feb;47(2):118-126

School of Optometry and Vision Science (N.K., M.D.P.W.), University of New South Wales, Australia; Brien Holden Vision Institute (N.K.), Sydney, Australia; Cornea Service (P.G.), L. V. Prasad Eye Institute, Kallam Anji Reddy Campus, Hyderabad, India; and Jhaveri Microbiology Centre (S.S.), Prof. Brien Holden Eye Research Centre, Hyderabad Eye Research Foundation, L. V. Prasad Eye Institute, Kallam Anji Reddy Campus, Hyderabad, India.

Objectives: To identify risk factors associated with contact lens-related microbial keratitis (CL-MK) and subsequent vision loss in a south Indian population.

Methods: A retrospective study of medical records at the LV Prasad Eye Institute in Hyderabad, India, of patients diagnosed with CL-MK and of controls who had no history of corneal inflammation during contact lens wear was undertaken. Variables such as demographic data, contact lens wear details, duration of the event, visual acuity, epithelial defect and infiltrate size, and microbiology of the cornea during the event were collected. Differences between cases and controls were analyzed using parametric and nonparametric tests. Logistic regression was used to calculate the odds ratio (OR) and associated 95% confidence intervals in univariate and multivariate analyses for cases vs. controls and for factors associated with vision loss.

Results: One hundred sixty-seven cases of CL-MK and 153 controls were included in the analyses. Risk factors associated with the greatest increased OR for CL-related MK were: being in professional employment vs. a student (OR=3.9), disposing lenses yearly versus monthly or biweekly (OR=2.2), and any overnight wear (OR=2.8). Risk factors associated with vision loss were: high myopia (OR=3.6), severe vs. mild severity (OR=16.0), and hypopyon (OR=4.3).

Conclusions: Identification of these risk factors may help inform safe contact lens wear habits and management strategies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/ICL.0000000000000737DOI Listing
February 2021

Acquired fluoroquinolone resistance genes in corneal isolates of Pseudomonas aeruginosa.

Infect Genet Evol 2020 11 28;85:104574. Epub 2020 Sep 28.

School of Optometry and Vision Science, University of New South Wales Sydney, Australia; School of Biological Sciences, Monash University, Clayton, Victoria, Australia. Electronic address:

Fluoroquinolones are widely used as an empirical therapy for pseudomonal ocular infections. Based on increasing reports on acquired fluoroquinolone resistance genes in clinical isolates of Pseudomonas aeruginosa, we investigated 33 strains of P. aeruginosa isolated from the cornea of microbial keratitis patients in India and Australia between 1992 and 2018 to understand the prevalence of acquired fluoroquinolone resistance genes in ocular isolates and to assess whether the possession of those genes was associated with fluoroquinolone susceptibility. Fourteen out of 33 strains were resistant to at least one fluoroquinolone. We obtained the whole genome sequence of 33 isolates using Illumina MiSeq platform and investigated the prevalence of two fluoroquinolone resistance genes crpP and qnrVC1. To examine the associated mobile genetic elements of qnrVC1 positive strains, we obtained long read sequences using Oxford Nanopore MinION and performed hybrid assembly to combine long reads with Illumina short sequence reads. We further assessed mutations in quinolone resistance determining regions (QRDRs) and antibiotic susceptibilities to ciprofloxacin, levofloxacin and moxifloxacin to examine the association between resistance genes and phenotype. Twenty strains possessed crpP in genetic islands characterised by possession of integrative conjugative elements. The qnrVC1 gene was carried by four isolates on class I integrons and Tn3 transposons along with aminoglycoside and beta-lactam resistance genes. We did not observe any evidence of plasmids carrying fluoroquinolone resistance genes. Resistance to fluoroquinolones was observed in those strains which possessed crpP, qnrVC1 and that had QRDRs mutations. The presence of crpP on its own was not associated with increased resistance to fluoroquinolones.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.meegid.2020.104574DOI Listing
November 2020

Design, Synthesis and Biological Evaluation of Biphenylglyoxamide-Based Small Molecular Antimicrobial Peptide Mimics as Antibacterial Agents.

Int J Mol Sci 2020 Sep 16;21(18). Epub 2020 Sep 16.

School of Chemistry, The University of New South Wales, Sydney, NSW 2052, Australia.

There has been an increasing interest in the development of antimicrobial peptides (AMPs) and their synthetic mimics as a novel class of antibiotics to overcome the rapid emergence of antibiotic resistance. Recently, phenylglyoxamide-based small molecular AMP mimics have been identified as potential leads to treat bacterial infections. In this study, a new series of biphenylglyoxamide-based small molecular AMP mimics were synthesised from the ring-opening reaction of -sulfonylisatin bearing a biphenyl backbone with a diamine, followed by the conversion into tertiary ammonium chloride, quaternary ammonium iodide and guanidinium hydrochloride salts. Structure-activity relationship studies of the analogues identified the octanesulfonyl group as being essential for both Gram-positive and Gram-negative antibacterial activity, while the biphenyl backbone was important for Gram-negative antibacterial activity. The most potent analogue was identified to be chloro-substituted quaternary ammonium iodide salt , which possesses antibacterial activity against both Gram-positive (MIC against = 8 μM) and Gram-negative bacteria (MIC against = 16 μM, = 63 μM) and disrupted 35% of pre-established biofilms at 32 μM. Cytoplasmic membrane permeability and tethered bilayer lipid membranes (tBLMs) studies suggested that acts as a bacterial membrane disruptor. In addition, in vitro toxicity studies showed that the potent compounds are non-toxic against human cells at therapeutic dosages.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms21186789DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7555970PMC
September 2020

Antibiotic Resistance Characteristics of Isolated from Keratitis in Australia and India.

Antibiotics (Basel) 2020 Sep 14;9(9). Epub 2020 Sep 14.

School of Optometry and Vision Science, UNSW, Sydney, NSW 2052, Australia.

This study investigated genomic differences in Australian and Indian isolates from keratitis (infection of the cornea). Overall, the Indian isolates were resistant to more antibiotics, with some of those isolates being multi-drug resistant. Acquired genes were related to resistance to fluoroquinolones, aminoglycosides, beta-lactams, macrolides, sulphonamides, and tetracycline and were more frequent in Indian (96%) than in Australian (35%) isolates ( = 0.02). Indian isolates had large numbers of gene variations (median 50,006, IQR = 26,967-50,600) compared to Australian isolates (median 26,317, IQR = 25,681-33,780). There were a larger number of mutations in the and genes associated with the mismatch repair (MMR) system in Indian isolates, which may result in strains losing their efficacy for DNA repair. The number of gene variations were greater in isolates carrying MMR system genes or . In the phylogenetic division, the number of core genes were similar in both groups, but Indian isolates had larger numbers of pan genes (median 6518, IQR = 6040-6935). Clones related to three different sequence types-ST308, ST316, and ST491-were found among Indian isolates. Only one clone, ST233, containing two strains was present in Australian isolates. The most striking differences between Australian and Indian isolates were carriage of (that encodes a cytolytic phospholipase) in Indian isolates and (that encodes for GTPase activator activity) in Australian isolates, large number of acquired resistance genes, greater changes to MMR genes, and a larger pan genome as well as increased overall genetic variation in the Indian isolates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/antibiotics9090600DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7559795PMC
September 2020

Activity of Antimicrobial Peptides and Ciprofloxacin against Biofilms.

Molecules 2020 Aug 24;25(17). Epub 2020 Aug 24.

School of Optometry and Vision Science, University of New South Wales, Sydney, NSW 2052, Australia.

is increasingly resistant to conventional antibiotics, which can be compounded by the formation of biofilms on surfaces conferring additional resistance. was grown in sub-inhibitory concentrations of the antimicrobial peptides (AMPs) melimine and Mel4 or ciprofloxacin for 30 consecutive days to induce the development of resistance. Antibiofilm effect of AMPs and ciprofloxacin was evaluated using crystal violet and live/dead staining with confocal microscopy. Effect on the cell membrane of biofilm cells was evaluated using DiSC(3)-5 dye and release of intracellular ATP and DNA/RNA. The minimum inhibitory concentration (MIC) of ciprofloxacin increased 64-fold after 30 passages, but did not increase for melimine or Mel4. Ciprofloxacin could not inhibit biofilm formation of resistant cells at 4× MIC, but both AMPs reduced biofilms by >75% at 1× MIC. At 1× MIC, only the combination of either AMP with ciprofloxacin was able to significantly disrupt pre-formed biofilms (≥61%; < 0.001). Only AMPs depolarized the cell membranes of biofilm cells at 1× MIC. At 1× MIC either AMP with ciprofloxacin released a significant amount of ATP ( < 0.04), but did not release DNA/RNA. AMPs do not easily induce resistance in and can be used in combination with ciprofloxacin to treat biofilm.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/molecules25173843DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7503749PMC
August 2020

In vivo efficacy of silver-impregnated barrel contact lens storage cases.

Cont Lens Anterior Eye 2021 Aug 15;44(4):101357. Epub 2020 Aug 15.

School of Optometry and Vision Science, UNSW Sydney, NSW, Australia. Electronic address:

Purpose: This study examined the rate and level of microbial contamination of silver and non-silver (control) barrel contact lens storage cases in vivo.

Methods: A prospective, single-centre, randomized, double blinded, crossover study was conducted to evaluate the efficacy of silver and control barrel cases used with an Oxipol™-based disinfecting solution over a two-month period. Lens cases were collected, and the frequency, type and level of microbial contamination evaluated using viable culture and standard identification methods. Questionnaires were used to assess the contact lens-related hygiene compliance of the participants.

Results: Forty eight daily contact lens wearers completed the study. Overall, 27 % of silver and 35 % control lens cases (P > 0.05) were contaminated, predominantly with Gram-positive bacteria. Only, 12 % of participants had good compliance, with 46 % having average compliance and 43 % poor compliance. Compliance score was not associated with level of microbial contamination. However, the use of hydrogel lenses in combination with silver cases compared to non-silver barrel cases resulted significantly greater numbers of bacteria colonising cases.

Conclusion: The present investigation demonstrated that the use of silver barrel cases does not reduce the overall rate and level of bacterial contamination, but that using hydrogel lenses in combination with silver cases resulted in higher numbers of bacteria isolated from cases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.clae.2020.08.001DOI Listing
August 2021

Toll-like receptor gene polymorphisms in patients with keratitis.

Cont Lens Anterior Eye 2021 Jun 25;44(3):101352. Epub 2020 Jul 25.

School of Optometry and Vision Science, University of New South Wales, Australia. Electronic address:

Objective: To investigate differences in SNPs in TLR genes between people who had keratitis and controls in an Indian population.

Methods: 145 cases of keratitis and 189 matched controls were recruited. DNA was extracted from peripheral blood. Single nucleotide polymorphisms (SNP) in TLR2 (n = 6), TLR4 (n = 15), TLR5 (n = 13) and TLR9 (n = 10) were analysed. The risk of developing keratitis was assessed based on allele, genotype and haplotype associations.

Results: For all cases of keratitis, the TLR4 SNP rs4986791 TC genotype frequency was significantly higher in cases (p = 0.006, OR = 1.96, 95 % CI 1.19-3.2). Including cases of only microbial keratitis (MK) revealed that genotypes in TLR2 SNP rs5743706 TA (p = 0.0001; OR = 8.61; 95 % CI 2.59-28.56)), TLR4 SNP s4986791 TC (p = 0.002; OR = 2.65; 95 % CI 1.39-5.07) were significantly more common for MK, whereas the TLR5 SNP rs2241096 A allele (p = 0.00316, OR = 0.42, 95 % CI 0.2-0.9286) and GA genotype (p = 0.016; OR = 0.45; 95 % CI 0.23-0.86) was significantly less common in MK cases. The TLR2 SNP rs5743706 genotype TA was significantly less common in the sterile keratitis (SK) group (p = 0.004, OR = 0.43, 95 %CI 0.24-0.77). Haplotype analysis of MK compared to controls showed that TLR2 AT was more common in controls (p = 0.003); TLR4 ACAC was more common in cases (p = 0.004); TLR5 TGGCA was more common in controls (p = 0.001).

Conclusion: The present study revealed multiple associations between variants across TLR genes, which may have implications for understanding the underlying host factors, risk of developing keratitis and molecular pathogenesis in keratitis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.clae.2020.07.003DOI Listing
June 2021

TFOS European Ambassador meeting: Unmet needs and future scientific and clinical solutions for ocular surface diseases.

Ocul Surf 2020 10 3;18(4):936-962. Epub 2020 Jun 3.

Institute of Vision and Optics, University of Crete, and Department of Ophthalmology, University Hospital of Heraklion, Heraklion, Greece.

The mission of the Tear Film & Ocular Surface Society (TFOS) is to advance the research, literacy, and educational aspects of the scientific field of the tear film and ocular surface. Fundamental to fulfilling this mission is the TFOS Global Ambassador program. TFOS Ambassadors are dynamic and proactive experts, who help promote TFOS initiatives, such as presenting the conclusions and recommendations of the recent TFOS DEWS II™, throughout the world. They also identify unmet needs, and propose future clinical and scientific solutions, for management of ocular surface diseases in their countries. This meeting report addresses such needs and solutions for 25 European countries, as detailed in the TFOS European Ambassador meeting in Rome, Italy, in September 2019.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jtos.2020.05.006DOI Listing
October 2020

Mechanism of Action of Surface Immobilized Antimicrobial Peptides Against .

Front Microbiol 2019 22;10:3053. Epub 2020 Jan 22.

School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia.

Bacterial colonization and biofilm development on medical devices can lead to infection. Antimicrobial peptide-coated surfaces may prevent such infections. Melimine and Mel4 are chimeric cationic peptides showing broad-spectrum antimicrobial activity once attached to biomaterials and are highly biocompatible in animal models and have been tested in Phase I and II/III human clinical trials. These peptides were covalently attached to glass using an azidobenzoic acid linker. Peptide attachment was confirmed using X-ray photoelectron spectroscopy and amino acid analysis. Mel4 when bound to glass was able to adopt a more ordered structure in the presence of bacterial membrane mimetic lipids. The ability of surface bound peptides to neutralize endotoxin was measured along with their interactions with the bacterial cytoplasmic membrane which were analyzed using DiSC(3)-5 and Sytox green, Syto-9, and PI dyes with fluorescence microscopy. Leakage of ATP and nucleic acids from cells were determined by analyzing the surrounding fluid. Attachment of the peptides resulted in increases in the percentage of nitrogen by 3.0% and 2.4%, and amino acid concentrations to 0.237 nmole and 0.298 nmole per coverslip on melimine and Mel4 coated surfaces, respectively. The immobilized peptides bound lipopolysaccharide and disrupted the cytoplasmic membrane potential of within 15 min. Membrane depolarization was associated with a reduction in bacterial viability by 82% and 63% for coatings melimine and Mel4, respectively ( < 0.001). Disruption of membrane potential was followed by leakage of ATP from melimine (1.5 ± 0.4 nM) or Mel4 (1.3 ± 0.2 nM) coated surfaces compared to uncoated glass after 2 h ( < 0.001). Sytox green influx started after 3 h incubation with either peptide. Melimine coatings yielded 59% and Mel4 gave 36% PI stained cells after 4 h. Release of the larger molecules (DNA/RNA) commenced after 4 h for melimine (1.8 ± 0.9 times more than control; = 0.008) and after 6 h with Mel4 (2.1 ± 0.2 times more than control; < 0.001). The mechanism of action of surface bound melimine and Mel4 was similar to that of the peptides in solution, however, their immobilization resulted in much slower (approximately 30 times) kinetics.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fmicb.2019.03053DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6987417PMC
January 2020

A Comparative Study on the Diagnostic Utility of Corneal Confocal Microscopy and Tear Neuromediator Levels in Diabetic Peripheral Neuropathy.

Curr Eye Res 2020 08 26;45(8):921-930. Epub 2019 Dec 26.

School of Optometry & Vision Science, University of New South Wales , Sydney, Australia.

Aims: To determine the utility of corneal confocal microscopy and tear neuromediator analysis in the diagnosis of diabetic peripheral neuropathy (DPN) as a result of type 1 and type 2 diabetes.

Methods: Seventy individuals with either type 1 diabetes or type 2 diabetes (T1D/T2D) underwent corneal confocal microscopy to assess the corneal nerve morphology. The concentration of substance P and calcitonin gene-related peptide (CGRP) in tears was measured by enzyme-linked immunosorbent assay. Motor excitability studies were conducted on the median nerve to assess axonal ion channel function. Based on total neuropathy score (TNS), participants were stratified into DPN (DPN+ve; TNS ≥ 2; T1D, n = 19; T2D, n = 16) and without DPN (DPN-ve; TNS ≤ 1; T1D, n = 19; T2D, n = 16). Areas under the receiver operating characteristic curves (AUCs) were calculated to obtain specificity and sensitivity of the measures to diagnose DPN.

Results: In T1D, the concentration of substance P and confocal microscopy measures were significantly reduced ( < .010) in DPN+ve. Also, for the nerve excitability measures, mean peak response, percentage of threshold electrotonus at peak and after 90-100 ms, superexcitability and subexcitability were significantly reduced ( < .050) in DPN+ve. In T2D, except for inferior whorl length ( = .190), all other corneal confocal microscopy measures were significantly reduced ( < .010) in DPN+ve, but there was no difference in substance P concentration. For the diagnosis of DPN in T1D, the AUC for inferior whorl length (0.910), mean peak response (0.800) and concentration of substance P (0.770) were high and in T2D, the AUC for corneal nerve fiber length (0.809) and nerve fractal dimension (0.777) were high.

Conclusion: Corneal confocal microscopy parameters provide a better diagnostic ability to detect DPN in T1D and T2D than nerve excitability measures or concentrations of tear neuromediators. The concentration of substance P could also be useful in diagnosing DPN but for T1D only.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/02713683.2019.1705984DOI Listing
August 2020

Antibiotics and Microbial Keratitis: Do We Need to Test for Resistance?

Authors:
Mark D P Willcox

Eye Contact Lens 2020 Jan;46(1):1-2

School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/ICL.0000000000000682DOI Listing
January 2020

Corneal nerve fiber loss in diabetes with chronic kidney disease.

Ocul Surf 2020 01 23;18(1):178-185. Epub 2019 Nov 23.

School of Optometry & Vision Science, University of New South Wales, Australia.

Aims: Patients with chronic kidney disease (CKD) in type 2 diabetes typically manifest with severe peripheral neuropathy. Corneal confocal microscopy is a novel technique that may serve as a marker of nerve injury in peripheral neuropathy. This study examines the changes that occur in corneal nerve morphology as a result of peripheral neuropathy due to renal dysfunction in people with type 2 diabetes.

Methods: Sixty-two participants (mean age, 62 ± 12 years) with type 2 diabetes and 25 age-matched healthy controls underwent a comprehensive assessment of neuropathy using the total neuropathy score (TNS). The corneal sub-basal nerve plexus was imaged using corneal confocal microscopy. Corneal nerve fiber length, fiber density, branch density, total branch density, nerve fractal dimension, inferior whorl length and inferior whorl nerve fractal dimension were quantified. Based on the eGFR, participants were classified into those with diabetic CKD (eGFR < 60; n = 22) and those without CKD (eGFR ≥ 60; n = 40).

Results: Participants with diabetic CKD had significantly lower corneal nerve fiber density (P = 0.037), length (P = 0.036) and nerve fractal dimension (P = 0.036) compared to those without CKD. Multiple linear regression analysis revealed that reduced corneal nerve fiber density (ß coefficient = 0.098, P = 0.017), length (ß coefficient = 0.006, P = 0.008) and nerve fractal dimension (ß coefficient = 0.001, P = 0.007) was associated with low eGFR levels when adjusted for age, duration of diabetes and severity of neuropathy.

Conclusion: Corneal confocal microscopy detects corneal nerve loss in patients with diabetic CKD and reduction in corneal nerve parameters is associated with the decline of kidney function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jtos.2019.11.010DOI Listing
January 2020

Analytical separations for lipids in complex, nonpolar lipidomes using differential mobility spectrometry.

J Lipid Res 2019 11 11;60(11):1968-1978. Epub 2019 Sep 11.

School of Medicine and Molecular Horizons, University of Wollongong, Wollongong, Australia

Secretions from meibomian glands located within the eyelid (commonly known as meibum) are rich in nonpolar lipid classes incorporating very-long (22-30 carbons) and ultra-long (>30 carbons) acyl chains. The complex nature of the meibum lipidome and its preponderance of neutral, nonpolar lipid classes presents an analytical challenge, with typically poor chromatographic resolution, even between different lipid classes. To address this challenge, we have deployed differential mobility spectrometry (DMS)-MS to interrogate the human meibum lipidome and demonstrate near-baseline resolution of the two major nonpolar classes contained therein, namely wax esters and cholesteryl esters. Within these two lipid classes, we describe ion mobility behavior that is associated with the length of their acyl chains and location of unsaturation. This capability was exploited to profile the molecular speciation within each class and thus extend meibum lipidome coverage. Intriguingly, structure-mobility relationships in these nonpolar lipids show similar trends and inflections to those previously reported for other physicochemical properties of lipids (e.g., melting point and phase-transition temperatures). Taken together, these data demonstrate that differential ion mobility provides a powerful orthoganol separation technology for the analysis of neutral lipids in complex matrices, such as meibum, and may further provide a means to predict physicochemical properties of lipids that could assist in inferring their biological function(s).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1194/jlr.D094854DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6824485PMC
November 2019

The Effect of Age, Gender and Body Mass Index on Tear Film Neuromediators and Corneal Nerves.

Curr Eye Res 2020 04 18;45(4):411-418. Epub 2019 Sep 18.

School of Optometry & Vision Science, University of New South Wales, Sydney, Australia.

: To evaluate the effect of age, gender and body mass index (BMI) on the levels of tear film neuromediators and corneal nerve parameters in healthy individuals.: Twenty-six healthy subjects were screened for any neurological deficits. The concentration of substance P and calcitonin gene-related peptide (CGRP) in tears was measured by enzyme-linked immunosorbent assay. Corneal nerve fibers were imaged using confocal microscopy and assessed by automated image analysis software. Associations between the clinical variables were analyzed using Pearson or Spearman correlation. Univariate general linear regression was performed to examine the independent relationship between age, BMI and gender of the subjects with concentrations of substance P, CGRP and corneal nerve fiber parameters.: Fifteen (58%) of the study participants were male. The mean age of the study cohort was 36 ± 12 years (range, 21-59) with an average BMI of 25 ± 4 kg/m. The median [IQR] concentrations of substance P and CGRP was 715 [372-1463] pg/mL and 38 [15-74] ng/mL respectively. Moderate but significant positive correlations were found between the concentration of substance P and corneal nerve fiber density (r = 0.467, = .016), nerve fiber length (r = 0.528, = .006) and nerve fractal dimension (r = 0.614, = .002). There was a significant age-dependent reduction in the concentration of substance P (-6% pg/mL per year, = .001) and CGRP (-8% ng/ml per year, < .001). Corneal nerve fiber density (-0.171 no./mm per year, = .029) and nerve fractal dimension (-0.001 per year, = .021) showed reductions with advancing age. Gender and BMI did not influence any of the measurements.: The concentrations of substance P and CGRP in tears, as well as corneal nerve fiber density and nerve fractal dimension, are significantly reduced with advancing age. Age should be considered when evaluating patients for diagnosis and follow-up of corneal neuropathy or ocular surface disorders.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/02713683.2019.1666998DOI Listing
April 2020

Author Correction: Comparative mode of action of the antimicrobial peptide melimine and its derivative Mel4 against Pseudomonas aeruginosa.

Sci Rep 2019 Sep 10;9(1):13267. Epub 2019 Sep 10.

School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-019-49307-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6733850PMC
September 2019

Tear film substance P: A potential biomarker for diabetic peripheral neuropathy.

Ocul Surf 2019 10 30;17(4):690-698. Epub 2019 Aug 30.

School of Optometry & Vision Science, University of New South Wales, Australia.

Objective: To explore the changes that occur in the concentrations of substance P (SP) and calcitonin gene-related peptide (CGRP) in tears as a result of corneal denervation and its association with diabetic peripheral neuropathy (DPN).

Methods: Sixty-three individuals with type 1 diabetes/type 2 diabetes (T1D/T2D) and 34 age-matched healthy controls underwent a detailed assessment of neuropathy using the Total Neuropathy Score (TNS). The concentration of SP and CGRP in tears was measured by enzyme-linked immunosorbent assay. The corneal sub-basal nerve plexus was imaged using corneal confocal microscopy. Corneal nerve fibre length, fibre density, branch density, total branch density, nerve fractal dimension and inferior whorl length were quantified.

Results: In T1D, the median [IQR] concentration of SP in tears was significantly reduced in those with DPN, (130 [61-692]pg/mL) compared to both control subjects (763 [405-1555]pg/mL, P < 0.01) and in those without DPN (914 [339-1832]pg/mL, P = 0.01); the concentration of CGRP was not changed. In T2D, there was no difference in neuropeptides between participants with diabetes and controls, regardless of neuropathic status. In T1D and T2D, corneal nerve parameters were significantly different between those with DPN or without DPN and controls. A significant correlation was noted between the concentration of tear film SP and TNS in T1D (r = -0.49; P < 0.001) and corneal nerve fibre density (r = 0.45; P < 0.001). The concentration of tear film CGRP was correlated significantly with the reduction of corneal nerve fibre density (r = 0.41; P = 0.01) in T1D.

Conclusion: Tear film SP may provide a potential non-invasive biomarker for assessing neuropathy in T1D.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jtos.2019.08.010DOI Listing
October 2019

The Development of an Antimicrobial Contact Lens - From the Laboratory to the Clinic.

Curr Protein Pept Sci 2020 ;21(4):357-368

School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.

Contact lens wear is generally safe and provides excellent vision. However, contact lens wear is often associated with the risk of developing ocular surface infection and inflammation, and in severe cases, the infection can result in loss of vision. Antimicrobial peptide-coated contact lenses have been made to help reduce the incidence of infection and inflammation. This paper reviews the research progress from conception, through the laboratory and preclinical tests to the latest information on clinical testing of an antimicrobial contact lens. We provide insights into the pathways followed and pitfalls that have been encountered. The journey has not always been linear or smooth, but has resulted in some of the first published clinical testing of antimicrobial peptide-coated contact lenses in humans. We hope this may help lead to the development and commercialisation of antimicrobial contact lenses in the future.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2174/1389203720666190820152508DOI Listing
January 2021
-->