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.

Colonization with two different Blastocystis subtypes in DSS-induced colitis mice is associated with strikingly different microbiome and pathological features

Rationale: The gut microbiota plays a significant role in the pathogenesis of inflammatory bowel disease (IBD). However, the role of Blastocystis infection and Blastocystis-altered gut microbiota in the development of inflammatory diseases and their underlying mechanisms are not well understood. Methods: We investigated the effect of Blastocystis ST4 and ST7 infection on the intestinal microbiota, metabolism, and host immune responses, and then explored the role of Blastocystis-altered gut microbiome in the development of dextran sulfate sodium (DSS)-induced colitis in mice. Results: This study showed that prior colonization with ST4 conferred protection from DSS-induced colitis through elevating the abundance of beneficial bacteria, short-chain fatty acid (SCFA) production and the proportion of Foxp3⁺ and IL-10-producing CD4⁺ T cells. Conversely, prior ST7 infection exacerbated the severity of colitis by increasing the proportion of pathogenic bacteria and inducing pro-inflammatory IL-17A and TNF-α-producing CD4⁺ T cells. Furthermore, transplantation of ST4- and ST7-altered microbiota resulted in similar phenotypes. Conclusions: Our data showed that ST4 and ST7 infection exert strikingly differential effects on the gut microbiota, and these could influence the susceptibility to colitis. ST4 colonization prevented DSS-induced colitis in mice and may be considered as a novel therapeutic strategy against immunological diseases in the future, while ST7 infection is a potential risk factor for the development of experimentally induced colitis that warrants attention.

Experimental colonization with Blastocystis ST4 is associated with protective immune responses and modulation of gut microbiome in a DSS-induced colitis mouse model

Background

Blastocystis is a common gut protistan parasite in humans and animals worldwide, but its interrelationship with the host gut microbiota and mucosal immune responses remains poorly understood. Different murine models of Blastocystis colonization were used to examine the effect of a common Blastocystis subtype (ST4) on host gut microbial community and adaptive immune system.

Results

Blastocystis ST4-colonized normal healthy mice and Rag1^−/− mice asymptomatically and was able to alter the microbial community composition, mainly leading to increases in the proportion of Clostridia vadinBB60 group and Lachnospiraceae NK4A136 group, respectively. Blastocystis ST4 colonization promoted T helper 2 (Th2) response defined by interleukin (IL)-5 and IL-13 cytokine production, and T regulatory (Treg) induction from colonic lamina propria in normal healthy mice. Additionally, we observed that Blastocystis ST4 colonization can maintain the stability of bacterial community composition and induce Th2 and Treg immune responses to promote faster recovery from experimentally induced colitis. Furthermore, fecal microbiota transplantation of Blastocystis ST4-altered gut microbiome to colitis mice reduced the severity of colitis, which was associated with increased production of short-chain fat acids (SCFAs) and anti-inflammatory cytokine IL-10.

Conclusions

The data confirm our hypothesis that Blastocystis ST4 is a beneficial commensal, and the beneficial effects of Blastocystis ST4 colonization is mediated through modulating of the host gut bacterial composition, SCFAs production, and Th2 and Treg responses in different murine colonization models.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00018-022-04271-9.

inPhocus: Current State and Challenges of Phage Research in Singapore

Bacteriophages and phage-derived proteins are a promising class of antibacterial agents that experience a growing worldwide interest. To map ongoing phage research in Singapore and neighboring countries, Lee Kong Chian School of Medicine, Nanyang Technological University Singapore (NTU) and Yong Loo Lin School of Medicine, National University of Singapore (NUS) recently co-organized a virtual symposium on Bacteriophage and Bacteriophage-Derived Technologies, which was attended by more than 80 participants. Topics were discussed relating to phage life cycles, diversity, the roles of phages in biofilms and the human gut microbiome, engineered phage lysins to combat polymicrobial infections in wounds, and the challenges and prospects of clinical phage therapy. This perspective summarizes major points discussed during the symposium and new perceptions that emerged after the panel discussion.

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.

Microbial exposure during early human development primes fetal immune cells

The human fetal immune system begins to develop early during gestation; however, factors responsible for fetal immune-priming remain elusive. We explored potential exposure to microbial agents in utero and their contribution toward activation of memory T cells in fetal tissues. We profiled microbes across fetal organs using 16S rRNA gene sequencing and detected low but consistent microbial signal in fetal gut, skin, placenta, and lungs in the 2^nd trimester of gestation. We identified several live bacterial strains including Staphylococcus and Lactobacillus in fetal tissues, which induced in vitro activation of memory T cells in fetal mesenteric lymph node, supporting the role of microbial exposure in fetal immune-priming. Finally, using SEM and RNA-ISH, we visualized discrete localization of bacteria-like structures and eubacterial-RNA within 14^th weeks fetal gut lumen. These findings indicate selective presence of live microbes in fetal organs during the 2^nd trimester of gestation and have broader implications toward the establishment of immune competency and priming before birth.

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.

Repurposing the anticancer drug cisplatin with the aim of developing novel Pseudomonas aeruginosa infection control agents

Antibiotic resistance threatens effective treatment of microbial infections globally. This situation has spurred the hunt for new antimicrobial compounds in both academia and the pharmaceutical industry. Here, we report how the widely used antitumor drug cisplatin may be repurposed as an effective antimicrobial against the nosocomial pathogen Pseudomonas aeruginosa. Cisplatin was found to effectively kill strains of P. aeruginosa. In such experiments, transcriptomic profiling showed upregulation of the recA gene, which is known to be important for DNA repair, implicating that cisplatin could interfere with DNA replication in P. aeruginosa. Cisplatin treatment significantly repressed the type III secretion system (T3SS), which is important for the secretion of exotoxins. Furthermore, cisplatin was also demonstrated to eradicate in vitro biofilms and in vivo biofilms in a murine keratitis model. This showed that cisplatin could be effectively used to eradicate biofilm infections which were otherwise difficult to be treated by conventional antibiotics. Although cisplatin is highly toxic for humans upon systemic exposure, a low toxicity was demonstrated with topical treatment. This indicated that higher-than-minimal inhibitory concentration (MIC) doses of cisplatin could be topically applied to treat persistent and recalcitrant P. aeruginosa infections.

Antimicrobial activity profiles of Amphiphilic Xanthone derivatives are a function of their molecular Oligomerization

Currently, membrane-targeting small antimicrobial peptidomimetics (SAP) are important in antibiotic development because bacteria appear to develop resistance to these surface-active compounds less readily. However, the molecular membrane-targeting action of SAPs has received little attention. In this study, we investigated the effect of oligomerization of amphiphilic xanthone, a model SAP, on its antimicrobial properties against both Gram-positive and Gram-negative bacteria. First, oligomer formation by an amphiphilic xanthone, compound 2 (also coded as AM052), was investigated via solution-state nuclear magnetic resonance (NMR) spectroscopy. Then, the effects of oligomerization on membrane disruption were further studied via biophysical approaches. The results showed that the antimicrobial activities of SAPs develop in several stages: oligomer formation in aqueous solution, initial binding of oligomers to the membrane-water interface followed by insertion into the membrane bilayer, aggregation of antimicrobial oligomers in the membrane, and induced membrane leakage. Ultimately, the presence of the oligomers in the bacterial membrane leads to decreased membrane fluidity and bacterial cell death. Interestingly, the early formation of large oligomers leads to stronger membrane disruption and more rapid bacterial killing. However, reduced antimicrobial activities against Gram-negative bacteria were observed for compounds that formed larger oligomers because the LPS layer acts as a barrier to large complexes. Taken together, our results suggest that oligomerization of SAPs has a strong impact on their antimicrobial properties.

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.

Transient Osteoporosis of the Hip: A Case Report

Transient osteoporosis of the hip (TOH) is a benign, selflimiting condition characterised by acute onset groin pain in adults. Early diagnosis is important to differentiate it from progressive conditions such as osteonecrosis. We report on a middle-aged male who presented with right groin pain without any prior trauma. The diagnosis of transient osteoporosis of hip was confirmed by Magnetic Resonance Imaging (MRI) and he was successfully treated with a course of Alendronate sodium, anti-inflammatory analgesics and a period of non-weight bearing ambulation.

N-Lipidated Peptide Dimers: Effective Antibacterial Agents against Gram-Negative Pathogens through Lipopolysaccharide Permeabilization

Treating infections caused by multidrug-resistant Gram-negative pathogens is challenging, and there is concern regarding the toxicity of the most effective antimicrobials for Gram-negative pathogens. We hypothesized that conjugating a fatty acid moiety onto a peptide dimer could maximize the interaction with lipopolysaccharide (LPS) and facilitate the permeabilization of the LPS barrier, thereby improving potency against Gram-negative pathogens. We systematically designed a series of N-lipidated peptide dimers that are active against Gram-negative bacteria, including carbapenem-resistant Enterobacteriaceae (CRE). The optimized lipid length was 6-10 carbons. At these lipid lengths, the N-lipidated peptide dimers exhibited strong LPS permeabilization. Compound 23 exhibited synergy with select antibiotics in most of the combinations tested. 23 and 32 also displayed rapid bactericidal activity. Importantly, 23 and 32 were nonhemolytic at 10 mg/mL, with no cellular or in vivo toxicity. These characteristics suggest that these compounds can overcome the limitations of current Gram-negative-targeted antimicrobials such as polymyxin B.

Amino acid modified xanthone derivatives: novel, highly promising membrane-active antimicrobials for multidrug-resistant Gram-positive bacterial infections

Antibiotic resistance is a critical global health care crisis requiring urgent action to develop more effective antibiotics. Utilizing the hydrophobic scaffold of xanthone, we identified three components that mimicked the action of an antimicrobial cationic peptide to produce membrane-targeting antimicrobials. Compounds 5c and 6, which contain a hydrophobic xanthone core, lipophilic chains, and cationic amino acids, displayed very promising antimicrobial activity against multidrug-resistant Gram-positive bacteria, including MRSA and VRE, rapid time-kill, avoidance of antibiotic resistance, and low toxicity. The bacterial membrane selectivity of these molecules was comparable to that of several membrane-targeting antibiotics in clinical trials. 5c and 6 were effective in a mouse model of corneal infection by S. aureus and MRSA. Evidence is presented indicating that 5c and 6 target the negatively charged bacterial membrane via a combination of electrostatic and hydrophobic interactions. These results suggest that 5c and 6 have significant promise for combating life-threatening infections.

Interaction between gemcitabine and mitomycin-C in vitro

Both gemcitabine (2',2'-difluorodeoxycytidine; dFdCyd) and mitomycin-C (MMC) are active against several solid malignancies. dFdCyd is an attractive agent for use in combination with drugs which damage DNA and with radiation therapy because of its ability to inhibit DNA replication and repair as well as its radiosensitizing effect. We hypothesized that the repair of MMC adducts in DNA might be inhibited by dFdCyd leading to a synergistic effect. To test this possibility, we studied the effect of combining dFdCyd and MMC in HT29 human colon carcinoma cells in vitro. The cells were exposed to a variety of drug concentration ratios and schedules, then assessed for clonogenic survival. D50 values (drug concentration at which clonogenicity is inhibited by 50%) were calculated, and the interactive effects of the two drugs were evaluated using median effect analysis. In this approach, if the calculated combination index (CI) is < 1, 1, or > 1, it indicates synergism, additivity, or antagonism, respectively (Chou and Talalay 1984). We found that marked synergy (CI of 0.5-0.7) was produced by concurrent exposure to mitomycin and gemcitabine. In contrast, sequential treatment led only to additivity. These findings suggest that, when combined in an appropriate schedule, the chemosensitizing effect of gemcitabine may be beneficial in the treatment of malignancies which are sensitive to MMC.

Localization of P-type calcium channels in the central nervous system

The distribution of the P-type calcium channel in the mammalian central nervous system has been demonstrated immunohistochemically by using a polyclonal specific antibody. This antibody was generated after P-channel isolation via a fraction from funnel-web spider toxin (FTX) that blocks the voltage-gated P channels in cerebellar Purkinje cells. In the cerebellar cortex, immunolabeling to the antibody appeared throughout the molecular layer, while all the other regions were negative. Intensely labeled patches of reactivity were seen on Purkinje cell dendrites, especially at bifurcations; much weaker reactivity was present in the soma and stem segment. Electron microscopic localization revealed labeled patches of plasma membrane on the soma, main dendrites, spiny branchlets, and spines; portions of the smooth endoplasmic reticulum were also labeled. Strong labeling was present in the periglomerular cells of the olfactory bulb and scattered neurons in the deep layer of the entorhinal and pyriform cortices. Neurons in the brainstem, habenula, nucleus of the trapezoid body and inferior olive and along the floor of the fourth ventricle were also labeled intensely. Medium-intensity reactions were observed in layer II pyramidal cells of the frontal cortex, the CA1 cells of the hippocampus, the lateral nucleus of the substantia nigra, lateral reticular nucleus, and spinal fifth nucleus. Light labeling was seen in the neocortex, striatum, and in some brainstem neurons.