Thermostability enhancement of polyethylene terephthalate degrading PETase using self- and nonself-ligating protein scaffolding approaches.

Polyethylene terephthalate (PET) hydrolase enzymes show promise for enzymatic PET degradation and green recycling of single-use PET vessels representing a major source of global pollution. Their full potential can be unlocked with enzyme engineering to render activities on recalcitrant PET substrates commensurate with cost-effective recycling at scale. Thermostability is a highly desirable property in industrial enzymes, often imparting increased robustness and significantly reducing quantities required. To date, most engineered PET hydrolases show improved thermostability over their parental enzymes. Here, we report engineered thermostable variants of Ideonella sakaiensis PET hydrolase enzyme (IsPETase) developed using two scaffolding strategies. The first employed SpyCatcher-SpyTag technology to covalently cyclize IsPETase, resulting in increased thermostability that was concomitant with reduced turnover of PET substrates compared to native IsPETase. The second approach using a GFP-nanobody fusion protein (vGFP) as a scaffold yielded a construct with a melting temperature of 80°C. This was further increased to 85°C when a thermostable PETase variant (FAST PETase) was scaffolded into vGFP, the highest reported so far for an engineered PET hydrolase derived from IsPETase. Thermostability enhancement using the vGFP scaffold did not compromise activity on PET compared to IsPETase. These contrasting results highlight potential topological and dynamic constraints imposed by scaffold choice as determinants of enzyme activity.

Diabetes Care During COVID-19 Pandemic in Singapore Using a Telehealth Strategy.

Singapore currently has one of highest number of confirmed COVID-19 cases in Southeast Asia. To curb the further spread of COVID-19, Singapore government announced a temporary nationwide lockdown (circuit breaker). In view of restrictions of patients' mobility and the enforcement of safe distancing measures, usual in-person visits were discouraged. Here we describe how diabetes care delivery was ad hoc redesigned applying a telehealth strategy. We describe a retrospective assessment of subjects with diabetes, with and without COVID-19 infection, during the circuit breaker period of 7th April to 1st June 2020 managed through Tan Tock Seng Hospital's telehealth platform. The virtual health applications consisted of telephone consultations, video telehealth visits via smartphones, and remote patient monitoring. The TTSH team intensively managed 298 diabetes patients using a telehealth strategy. The group comprised of (1) 84 inpatient COVID-19 patients with diabetes who received virtual diabetes education and blood glucose management during their hospitalisation and follow-up via phone calls after discharge and (2) 214 (n=192 non-COVID; n=22 COVID-positive) outpatient subjects with suboptimal glycaemic control who received intensive diabetes care through telehealth approaches. Remote continuous glucose monitoring was applied in 80 patients to facilitate treatment adjustment and hypoglycaemia prevention. The COVID-19 pandemic situation mooted an immediate disruptive transformation of healthcare processes. Virtual health applications were found to be safe, effective and efficient to replace current in-person visits.

Impact of prophylactic intracameral moxifloxacin on post-cataract surgery endophthalmitis: data from a tertiary eye care facility in rural India.

PURPOSE: To study the impact of prophylactic intracameral (IC) moxifloxacin on the incidence, clinical profile and outcomes in eyes developing post-cataract surgery endophthalmitis (PCE). METHODS: This was a single-centre, retrospective, comparative, observational study in which all eyes with PCE between June 2013 and May 2014 without IC moxifloxacin prophylaxis (group A) and June 2015-May 2016 with IC moxifloxacin prophylaxis (group B) were analysed. RESULTS: A total of 101,815 cataract surgeries were performed in group A and 112,967 in group B. PCE was diagnosed in 179 eyes (0.18%) in group A and 92 eyes (0.08%) in group B (p < 0.001). Greater reduction in risk of PCE was seen in subsidised patients compared to private. The presenting and final visual acuity was significantly better in group B (p < 0.05). CONCLUSIONS: Prophylactic IC moxifloxacin reduced the incidence of PCE with maximum benefit being observed for the subsidised patients and also helped achieve a significantly better visual acuity following the resolution of endophthalmitis.

Antimicrobial Activity and Cell Selectivity of Synthetic and Biosynthetic Cationic Polymers.

The mammalian and microbial cell selectivity of synthetic and biosynthetic cationic polymers has been investigated. Among the polymers with peptide backbones, polymers containing amino side chains display greater antimicrobial activity than those with guanidine side chains, whereas ethylenimines display superior activity over allylamines. The biosynthetic polymer ε-polylysine (εPL) is noncytotoxic to primary human dermal fibroblasts at concentrations of up to 2,000 µg/ml, suggesting that the presence of an isopeptide backbone has greater cell selectivity than the presence of α-peptide backbones. Both εPL and linear polyethylenimine (LPEI) exhibit bactericidal properties by depolarizing the cytoplasmic membrane and disrupt preformed biofilms. εPL displays broad-spectrum antimicrobial properties against antibiotic-resistant Gram-negative and Gram-positive strains and fungi. εPL elicits rapid bactericidal activity against both Gram-negative and Gram-positive bacteria, and its biocompatibility index is superior to those of cationic antiseptic agents and LPEI. εPL does not interfere with the wound closure of injured rabbit corneas. In a rabbit model of bacterial keratitis, the topical application of εPL (0.3%, wt/vol) decreases the bacterial burden and severity of infections caused by Pseudomonas aeruginosa and Staphylococcus aureus strains. In vivo imaging studies confirm that εPL-treated corneas appeared transparent and nonedematous compared to untreated infected corneas. Taken together, our results highlight the potential of εPL in resolving topical microbial infections.

Electrodiagnosis of reversible conduction failure in Guillain-Barré syndrome.

INTRODUCTION: In this study we propose electrodiagnostic criteria for early reversible conduction failure (ERCF) in axonal Guillain-Barré syndrome (GBS) and apply them to a cohort of GBS patients. METHODS: Serial nerve conduction studies (NCS) were retrospectively analyzed in 82 GBS patients from 3 centers. The criteria for the presence of ERCF in a nerve were: (i) a 50% increase in amplitude of distal compound muscle action potentials or sensory nerve action potentials; or (ii) resolution of proximal motor conduction block with an accompanying decrease in distal latencies or compound muscle action potential duration or increase in conduction velocities. RESULTS: Of 82 patients from 3 centers, 37 (45%) had ERCF, 21 (26%) had a contrasting evolution pattern, and 8 (10%) had both. Sixteen patients did not show an amplitude increase of at least 50%. CONCLUSION: Our proposed criteria identified a group of patients with a characteristic evolution of NCS abnormality that is consistent with ERCF. Muscle Nerve 56: 919-924, 2017.

Generalizability of Deep Neural Networks for Vertical Cup-to-Disc Ratio Estimation in Ultra-Widefield and Smartphone-Based Fundus Images.

Purpose: To develop and validate a deep learning system (DLS) for estimation of vertical cup-to-disc ratio (vCDR) in ultra-widefield (UWF) and smartphone-based fundus images. Methods: A DLS consisting of two sequential convolutional neural networks (CNNs) to delineate optic disc (OD) and optic cup (OC) boundaries was developed using 800 standard fundus images from the public REFUGE data set. The CNNs were tested on 400 test images from the REFUGE data set and 296 UWF and 300 smartphone-based images from a teleophthalmology clinic. vCDRs derived from the delineated OD/OC boundaries were compared with optometrists' annotations using mean absolute error (MAE). Subgroup analysis was conducted to study the impact of peripapillary atrophy (PPA), and correlation study was performed to investigate potential correlations between sectoral CDR (sCDR) and retinal nerve fiber layer (RNFL) thickness. Results: The system achieved MAEs of 0.040 (95% CI, 0.037-0.043) in the REFUGE test images, 0.068 (95% CI, 0.061-0.075) in the UWF images, and 0.084 (95% CI, 0.075-0.092) in the smartphone-based images. There was no statistical significance in differences between PPA and non-PPA images. Weak correlation (r = -0.4046, P < 0.05) between sCDR and RNFL thickness was found only in the superior sector. Conclusions: We developed a deep learning system that estimates vCDR from standard, UWF, and smartphone-based images. We also described anatomic peripapillary adversarial lesion and its potential impact on OD/OC delineation. Translational Relevance: Artificial intelligence can estimate vCDR from different types of fundus images and may be used as a general and interpretable screening tool to improve community reach for diagnosis and management of glaucoma.

Propranolol Ameliorates the Antifungal Activity of Azoles in Invasive Candidiasis.

The effectiveness of current antifungal therapies is hampered by the emergence of drug resistance strains, highlighting an urgent need for new alternatives such as adjuvant antifungal treatments. This study aims to examine the synergism between propranolol and antifungal drugs, based on the premise that propranolol is known to inhibit fungal hyphae. In vitro studies demonstrate that propranolol potentiates the antifungal activity of azoles and that the effect is more pronounced for propranolol-itraconazole combination. Using an in vivo murine systemic candidemia model, we show that propranolol-itraconazole combination treatment resulted in a lower rate of body weight loss, decreased kidney fungal bioburden and renal inflammation when compared to propranolol and azole treatment alone or untreated control. Altogether, our findings suggest that propranolol increases the efficacy of azoles against C. albicans, offering a new therapeutic strategy against invasive fungal infections.

Development of teixobactin analogues containing hydrophobic, non-proteogenic amino acids that are highly potent against multidrug-resistant bacteria and biofilms.

Teixobactin is a cyclic undecadepsipeptide that has shown excellent potency against multidrug-resistant pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE). In this article, we present the design, synthesis, and antibacterial evaluations of 16 different teixobactin analogues. These simplified analogues contain commercially available hydrophobic, non-proteogenic amino acid residues instead of synthetically challenging expensive L-allo-enduracididine amino acid residue at position 10 together with different combinations of arginines at positions 3, 4 and 9. The new teixobactin analogues showed potent antibacterial activity against a broad panel of Gram-positive bacteria, including MRSA and VRE strains. Our work also presents the first demonstration of the potent antibiofilm activity of teixobactin analogoues against Staphylococcus species associated with serious chronic infections. Our results suggest that the use of hydrophobic, non-proteogenic amino acids at position 10 in combination with arginine at positions 3, 4 and 9 holds the key to synthesising a new generation of highly potent teixobactin analogues to tackle resistant bacterial infections and biofilms.

Ocular Toxoplasmosis.

INTRODUCTION: Ocular toxoplasmosis is the leading cause of posterior uveitis worldwide, affecting individuals acrossdifferent age groups. The key to reducing vision loss includes prompt diagnosis and treatment. However, despite the prevalence of ocular toxoplasmosis, there has been little consensus regarding its pathophysiology,clinical features, diagnosis, and especially management. METHODS: The data sources were literature reviews, including Pub Med and Medline databases. Search terms included toxoplasmosis, retinitis, vasculitis, vitritis, uveitis alone or in combination with, serum, aqueous, vitreous eye, ocular and review. RESULTS: In this review paper, we have sought to provide an overview of the pathophysiology, epidemiology, and clinical features of the disease, both based on current literature and our own clinical experience. We have also discussed the use of serology, ocular fluid, and ophthalmic investigations that could further facilitate the diagnosis of ocular toxoplasmosis.Different management strategies have been reported worldwide, including newer approaches such as local therapy. CONCLUSION: A better understanding of critical aspects of ocular toxoplasmosis will hopefully lead to reduced morbidity, including blindness associated with this condition.

An Unusual Case of Concurrent Central Retinal Vein and Cilioretinal Artery Occlusion in a Healthy Patient.

It is rare for young, healthy patients to have retinal venous or arterial occlusions and even rarer for both to occur in concert. Such an occurrence should prompt a rapid and extensive workup to prevent further complications. We present our patient, a 37-year-old Lebanese male, who reported a 3-day history of blurring of vision in his left eye. He had no medical or ocular history and is a nonsmoker. Examination of the left fundus revealed inferior macular edema and retinal whitening associated with tortuous retinal veins. He was diagnosed with a combined central retinal vein and cilioretinal artery occlusion. Emergency treatment was done for an acute arterial occlusion. Embolic and thrombotic causes were excluded with investigations. The only positive result was homozygosity for 677C>T mutation of the 5,10 methylenetetrahydrofolate reductase (MTHFR) enzyme gene. MTHFR enzyme breaks down homocysteine, which is atherogenic and prothrombotic. This mutation can lead to a prothrombotic state, precipitating this occurrence. In fact, the Lebanese population is known to have the highest incidence of such mutations, but there are surprisingly few reports on retinal vascular occlusions attributed to this. He was promptly treated with antiplatelet therapy, possibly preventing a full-blown central retinal vein occlusion. After 4 weeks, his vision improved to 6/6 bilaterally. Examination showed less tortuous veins, no more retinal whitening, resolution of macula edema and visual field defect. Hyperhomocysteinemia can be significant in patients without ischemic risk factors. It is vital to manage these patients promptly, preventing future sight and life-threatening events.

Evaluation of Host Defense Peptide (CaD23)-Antibiotic Interaction and Mechanism of Action: Insights From Experimental and Molecular Dynamics Simulations Studies.

Background/Aim: Host defense peptides (HDPs) have the potential to provide a novel solution to antimicrobial resistance (AMR) in view of their unique and broad-spectrum antimicrobial activities. We had recently developed a novel hybrid HDP based on LL-37 and human beta-defensin-2, named CaD23, which was shown to exhibit good in vivo antimicrobial efficacy against Staphylococcus aureus in a bacterial keratitis murine model. This study aimed to examine the potential CaD23-antibiotic synergism and the secondary structure and underlying mechanism of action of CaD23. Methods: Peptide-antibiotic interaction was evaluated against S. aureus, methicillin-resistant S. aureus (MRSA), and Pseudomonas aeruginosa using established checkerboard and time-kill assays. Fractional inhibitory concentration index (FICI) was calculated and interpreted as synergistic (FIC<0.5), additive (FIC between 0.5-1.0), indifferent (FIC between >1.0 and ≤4), or antagonistic (FIC>4). SYTOX green uptake assay was performed to determine the membrane-permeabilising action of CaD23. Molecular dynamics (MD) simulations were performed to evaluate the interaction of CaD23 with bacterial and mammalian mimetic membranes. Circular dichroism (CD) spectroscopy was also performed to examine the secondary structures of CaD23. Results: CaD23-amikacin and CaD23-levofloxacin combination treatment exhibited a strong additive effect against S. aureus SH1000 (FICI = 0.60-0.69) and MRSA43300 (FICI = 0.56-0.60) but an indifferent effect against P. aeruginosa (FIC = 1.03-1.15). CaD23 (at 25 µg/ml; 2xMIC) completely killed S. aureus within 30 min. When used at sub-MIC concentration (3.1 µg/ml; 0.25xMIC), it was able to expedite the antimicrobial action of amikacin against S. aureus by 50%. The rapid antimicrobial action of CaD23 was attributed to the underlying membrane-permeabilising mechanism of action, evidenced by the SYTOX green uptake assay and MD simulations studies. MD simulations revealed that cationicity, alpha-helicity, amphiphilicity and hydrophobicity (related to the Trp residue at C-terminal) play important roles in the antimicrobial action of CaD23. The secondary structures of CaD23 observed in MD simulations were validated by CD spectroscopy. Conclusion: CaD23 is a novel alpha-helical, membrane-active synthetic HDP that can enhance and expedite the antimicrobial action of antibiotics against Gram-positive bacteria when used in combination. MD simulations serves as a powerful tool in revealing the peptide secondary structure, dissecting the mechanism of action, and guiding the design and optimisation of HDPs.

Hybrid derivative of cathelicidin and human beta defensin-2 against Gram-positive bacteria: A novel approach for the treatment of bacterial keratitis.

Bacterial keratitis (BK) is a major cause of corneal blindness globally. This study aimed to develop a novel class of antimicrobial therapy, based on human-derived hybrid host defense peptides (HyHDPs), for treating BK. HyHDPs were rationally designed through combination of functional amino acids in parent HDPs, including LL-37 and human beta-defensin (HBD)-1 to -3. Minimal inhibitory concentrations (MICs) and time-kill kinetics assay were performed to determine the concentration- and time-dependent antimicrobial activity and cytotoxicity was evaluated against human corneal epithelial cells and erythrocytes. In vivo safety and efficacy of the most promising peptide was examined in the corneal wound healing and Staphylococcus aureus (ATCC SA29213) keratitis murine models, respectively. A second-generation HyHDP (CaD23), based on rational hybridization of the middle residues of LL-37 and C-terminal of HBD-2, was developed and was shown to demonstrate good efficacy against methicillin-sensitive and methicillin-resistant S. aureus [MIC = 12.5-25.0 µg/ml (5.2-10.4 µM)] and S. epidermidis [MIC = 12.5 µg/ml (5.2 µM)], and moderate efficacy against P. aeruginosa [MIC = 25-50 µg/ml (10.4-20.8 µM)]. CaD23 (at 25 µg/ml or 2× MIC) killed all the bacteria within 30 min, which was 8 times faster than amikacin (25 µg/ml or 20× MIC). After 10 consecutive passages, S. aureus (ATCC SA29213) did not develop any antimicrobial resistance (AMR) against CaD23 whereas it developed significant AMR (i.e. a 32-fold increase in MIC) against amikacin, a commonly used treatment for BK. Pre-clinical murine studies showed that CaD23 (0.5 mg/ml) achieved a median reduction of S. aureus bioburden by 94% (or 1.2 log10 CFU/ml) while not impeding corneal epithelial wound healing. In conclusion, rational hybridization of human-derived HDPs has led to generation of a potentially efficacious and safe topical antimicrobial agent for treating Gram-positive BK, with no/minimal risk of developing AMR.

SLAP reagents for the photocatalytic synthesis of C3/C5-substituted, N-unprotected selenomorpholines and 1,4-selenazepanes.

Herein, we disclose the first set of unique selenium-containing SLAP (SiLicon Amine Protocol) reagents for the direct synthesis of C3/C5-substituted selenomorpholines and 1,4-selenazepanes from diverse (hetero)aldehydes under mild photocatalytic conditions. Enantiomerically pure 1,2-amino alcohol/α-amino acid versions of these heterocycles were also synthesized. Further, we have shown the late-stage modification of certain biologically active agents using the developed seleno-SLAP reagents.

The utility of sural-sparing pattern in the electrodiagnosis of regional subtypes of Guillain-Barré Syndrome.

OBJECTIVE: We present an exemplar patient, illustrating utility of the sural-sparing pattern in diagnosis of Guillain-Barré Syndrome (GBS). We then present data that sheds light on the pathophysiology of sural-sparing. METHOD AND RESULTS: We describe a case of complex ophthalmoplegia that exemplifies the challenge of diagnosing regional subtypes of Guillain-Barré Syndrome, and the value of scrutinizing sensory nerve action potentials for the sural-sparing pattern. We also demonstrate, in a series of GBS patients, how serial nerve conduction studies can reveal "covert" sural-sparing in patients without sural-sparing on the initial study. Finally, by studying the median and radial sensory nerve action potentials at digit I in GBS patients, we demonstrate that the likely pathology of sural-sparing is related to the predilection of median nerve for subclinical entrapment; where the blood-nerve barrier is deficient and therefore more exposed to the immunopathology of GBS. CONCLUSION: Incorporating sural-sparing would improve the specificity of GBS electrodiagnosis; especially in difficult to diagnose regional subtypes of GBS.

Publisher Correction: A Simplified, Graded, Electrodiagnostic Criterion for Guillain-Barré Syndrome That Incorporates Sensory Nerve Conduction Studies.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Mussel-Inspired Durable Antimicrobial Contact Lenses: The Role of Covalent and Noncovalent Attachment of Antimicrobials.

Contact lens is a major risk factor for microbial keratitis among contact lens wearers. Chemical strategies that can prevent microbial adhesion and biofilm formation are required to improve a wearer's hygiene and safety. Taking advantage of the material-independent properties of a polydopamine (pDA) coating, we investigated the role of covalent/noncovalent interactions of the antimicrobials and pDA in conferring long-term antimicrobial activities. The developed antimicrobial contact lenses not only retain their antibacterial efficiency against different bacterial strains for 2 weeks but also inhibit microbial adhesion and biofilm formation on the lens surfaces. The designed antimicrobial coatings were found to be safe for ocular cell lines. Moreover, the antimicrobial coatings did not affect the functional and surface properties of coated contact lenses. This methodology can be used to protect the contact lenses from microbial contamination for prolonged periods and has the potential to be extended for designing antimicrobial coatings for other medical devices as well.

Multifunctional Antimicrobial Nanofiber Dressings Containing ε-Polylysine for the Eradication of Bacterial Bioburden and Promotion of Wound Healing in Critically Colonized Wounds.

Bacterial colonization of acute and chronic wounds is often associated with delayed wound healing and prolonged hospitalization. The rise of multi-drug resistant bacteria and the poor biocompatibility of topical antimicrobials warrant safe and effective antimicrobials. Antimicrobial agents that target microbial membranes without interfering with the mammalian cell proliferation and migration hold great promise in the treatment of traumatic wounds. This article reports the utility of superhydrophilic electrospun gelatin nanofiber dressings (NFDs) containing a broad-spectrum antimicrobial polymer, ε-polylysine (εPL), crosslinked by polydopamine (pDA) for treating second-degree burns. In a porcine model of partial thickness burns, NFDs promoted wound closure and reduced hypertrophic scarring compared to untreated burns. Analysis of NFDs in contact with the burns indicated that the dressings trap early colonizers and elicit bactericidal activity, thus creating a sterile wound bed for fibroblasts migration and re-epithelialization. In support of these observations, in porcine models of Pseudomonas aeruginosa and Staphylococcus aureus colonized partial thickness burns, NFDs decreased bacterial bioburden and promoted wound closure and re-epithelialization. NFDs displayed superior clinical outcome than standard-of-care silver dressings. The excellent biocompatibility and antimicrobial efficacy of the newly developed dressings in pre-clinical models demonstrate its potential for clinical use to manage infected wounds without compromising tissue regeneration.

A Simplified, Graded, Electrodiagnostic Criterion for Guillain-Barré Syndrome That Incorporates Sensory Nerve Conduction Studies.

Traditional electrodiagnostic (EDX) criteria for Guillain-Barré Syndrome (GBS), e.g. those delineated by Ho et al. and Hadden et al., rely on motor nerve conduction studies (NCS), and focus on differentiating GBS subtypes instead of the accurate diagnosis of GBS. Sensory studies, including the sural-sparing pattern, are not routinely used in GBS EDX. We studied the utility of a simplified criterion that utilizes sensory NCS. Motor and sensory NCS abnormalities were defined by comparing against age and height adjusted norms derived from 245 controls. We considered the sural-sparing pattern a positive diagnostic feature. We analyzed 109 prospectively validated GBS patients and graded them as "Definite", "Probable" and "Possible" based on the number of motor and sensory abnormalities detected. Using proposed EDX criteria, 35.8%, 43.1%, 11.9% of all GBS patients were considered "Definite", "Probable" or "Possible" respectively; whereas traditional EDX criteria only diagnosed 49.5% of cases. 27.5%, 35.3% and 21.6% of patients with the Miller-Fisher Syndrome (MFS) subtype of GBS were considered "Definite", "Probable" or "Possible" respectively. In comparison, traditional criteria only detected 15.7% of cases. Our proposed EDX criterion, that includes sensory NCS, improves and grades the diagnostic certainty of GBS, especially MFS.