Antimicrobial and Antibiofilm Potential of Green-Synthesized Graphene-Silver Nanocomposite against Multidrug-Resistant Nosocomial Pathogens.

Hospital-acquired infections (HAIs) pose a significant risk to global health, impacting millions of individuals globally. These infections have increased rates of morbidity and mortality due to the prevalence of widespread antimicrobial resistance (AMR). Graphene-based nanoparticles (GBNs) are known to possess extensive antimicrobial properties by inflicting damage to the cell membrane, suppressing virulence, and inhibiting microbial biofilms. Developing alternative therapies for HAIs and addressing AMR can be made easier and more affordable by combining nanoparticles with medicinal plants harboring antimicrobial properties. Hence, this study was undertaken to develop a novel graphene-silver nanocomposite via green synthesis using Trillium govanianum plant extract as a reducing agent. The resulting nanocomposite comprised silver nanoparticles embedded in graphene sheets. The antibacterial and antifungal properties of graphene-silver nanocomposites were investigated against several nosocomial pathogens, namely, Candida auris, Candida glabrata, Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The nanocomposite displayed broad-range antimicrobial potential against the test pathogens, with minimum inhibitory concentrations (MICs) ranging between 31.25 and 125.0 µg/mL, and biofilm inhibition up to 80-96%. Moreover, nanocomposite-functionalized urinary catheters demonstrated hemocompatibility towards sheep erythrocytes and imparted anti-fouling activity to the biomaterial, while also displaying biocompatibility towards HEK 293 cells. Collectively, this investigation highlights the possible application of green-synthesized GBNs as an effective alternative to conventional antibiotics for combating multidrug-resistant pathogens.

Biofilms and their role on diseases.

Biofilms are complex, three-dimensional structures that provide a long-established survival mechanism for microorganisms. Biofilms play a substantial role in pathogenesis as they can evade the immune response and be highly resistant to conventional antimicrobials, thus impacting the human health and healthcare system. To address this issue, BMC Microbiology invites submissions to the collection 'Biofilms and its impact on disease'.

Identification of Staphylococcus aureus Penicillin Binding Protein 4 (PBP4) Inhibitors.

Methicillin-resistant Staphylococcus aureus (MRSA) is a global healthcare concern. Such resistance has historically been attributed to the acquisition of mecA (or mecC), which encodes an alternative penicillin binding protein, PBP2a, with low ß-lactam affinity. However, recent studies have indicated that penicillin binding protein 4 (PBP4) is also a critical determinant of S. aureus methicillin resistance, particularly among community-acquired MRSA strains. Thus, PBP4 has been considered an intriguing therapeutic target as corresponding inhibitors may restore MRSA ß-lactam susceptibility. In addition to its role in antibiotic resistance, PBP4 has also recently been shown to be required for S. aureus cortical bone osteocyte lacuno-canalicular network (OLCN) invasion and colonization, providing the organism with a niche for re-occurring bone infection. From these perspectives, the development of PBP4 inhibitors may have tremendous impact as agents that both reverse methicillin resistance and inhibit the organism's ability to cause chronic osteomyelitis. Accordingly, using a whole-cell high-throughput screen of a 30,000-member small molecule chemical library and secondary assays we identified putative S. aureus PBP4 inhibitors. Quantitative reverse transcriptase mediated PCR and PBP4 binding assays revealed that hits could be further distinguished as compounds that reduce PBP4 expression versus compounds that are likely to affect the protein's function. We also showed that 6.25 µM (2.5 µg/mL) of the lead candidate, 9314848, reverses the organism's PBP4-dependent MRSA phenotype and inhibits its ability to traverse Microfluidic-Silicon Membrane-Canalicular Arrays (µSiM-CA) that model the OLCN orifice. Collectively, these molecules may represent promising potential as PBP4-inhibitors that can be further developed as adjuvants for the treatment of MRSA infections and/or osteomyelitis prophylactics.

Optimized Silica-Binding Peptide-Mediated Delivery of Bactericidal Lysin Efficiently Prevents Staphylococcus aureus from Adhering to Device Surfaces.

Staphylococcal-associated device-related infections (DRIs) represent a significant clinical challenge causing major medical and economic sequelae. Bacterial colonization, proliferation, and biofilm formation after adherence to surfaces of the indwelling device are probably the primary cause of DRIs. To address this issue, we incorporated constructs of silica-binding peptide (SiBP) with ClyF, an anti-staphylococcal lysin, into functionalized coatings to impart bactericidal activity against planktonic and sessile Staphylococcus aureus. An optimized construct, SiBP1-ClyF, exhibited improved thermostability and staphylolytic activity compared to its parental lysin ClyF. SiBP1-ClyF-functionalized coatings were efficient in killing MRSA strain N315 (>99.999% within 1 h) and preventing the growth of static and dynamic S. aureus biofilms on various surfaces, including siliconized glass, silicone-coated latex catheter, and silicone catheter. Additionally, SiBP1-ClyF-immobilized surfaces supported normal attachment and growth of mammalian cells. Although the recycling potential and long-term stability of lysin-immobilized surfaces are still affected by the fragility of biological protein molecules, the present study provides a generic strategy for efficient delivery of bactericidal lysin to solid surfaces, which serves as a new approach to prevent the growth of antibiotic-resistant microorganisms on surfaces in hospital settings and could be adapted for other target pathogens as well.

A Novel Acinetobacter baumannii Bacteriophage Endolysin LysAB54 With High Antibacterial Activity Against Multiple Gram-Negative Microbes.

The rapid spread and emergence of multidrug-resistant Acinetobacter baumannii and other pathogenic Gram-negative bacteria spurred scientists and clinicians to look for alternative therapeutic agents to conventional antibiotics. In the present study, an A. baumannii bacteriophage p54 was isolated and characterized. Morphological and genome analysis revealed that bacteriophage p54 belongs to Myoviridae family with a genome size of 165,813 bps. A novel endolysin, namely LysAB54, showing low similarity with other well-known related endolysins, was cloned, expressed, and characterized from the bacteriophage p54. LysAB54 showed significant bactericidal activity against multidrug-resistant A. baumannii and other Gram-negative bacteria, including Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli, in the absence of outer membrane permeabilizers. Based on all those observations, LysAB54 could represent a potential agent for the treatment of multidrug-resistant Gram-negative superbugs.

Encapsulation and Delivery of Therapeutic Phages.

Delivery of therapeutic compounds to the site of action is crucial. While many chemical substances such as beta-lactam antibiotics can reach therapeutic levels in most parts throughout the human body after administration, substances of higher molecular weight such as therapeutic proteins may not be able to reach the site of action (e.g. an infection), and are therefore ineffective. In the case of therapeutic phages, i.e. viruses that infect microbes that can be used to treat bacterial infections, this problem is exacerbated; not only are phages unable to penetrate tissues, but phage particles can be cleared by the immune system and phage proteins are rapidly degraded by enzymes or inactivated by the low pH in the stomach. Yet, the use of therapeutic phages is a highly promising strategy, in particular for infections caused by bacteria that exhibit multi-drug resistance. Clinicians increasingly encounter situations where no treatment options remain available for such infections, where antibiotic compounds are ineffective. While the number of drug-resistant pathogens continues to rise due to the overuse and misuse of antibiotics, no new compounds are becoming available as many pharmaceutical companies discontinue their search for chemical antimicrobials. In recent years, phage therapy has undergone massive innovation for the treatment of infections caused by pathogens resistant to conventional antibiotics. While most therapeutic applications of phages are well described in the literature, other aspects of phage therapy are less well documented. In this review, we focus on the issues that are critical for phage therapy to become a reliable standard therapy and describe methods for efficient and targeted delivery of phages, including their encapsulation.

Proteinuria in Severe Hypothyroidism: A Prospective Study.

CONTEXT: Hypothyroidism is associated with reversible decline in kidney function as measured by estimated glomerular filtration rate (eGFR). eGFR and proteinuria are the most important markers for clinical assessment of kidney function. Though hypothyroidism is associated with proteinuria in cross-sectional data, the impact of treatment on proteinuria is unknown. OBJECTIVE: This study explores the effect of thyroid hormone replacement therapy on eGFR and 24-hour urine protein excretion in patients with severe primary hypothyroidism. DESIGN AND PARTICIPANTS: This study was a prospective, observational cohort study in adults with severe primary hypothyroidism (serum thyrotropin [TSH] > 50 µIU/mL). Individuals with preexisting or past kidney disease, kidney or urinary tract abnormalities, calculi or surgery, diabetes mellitus, or hypertension were excluded. The participants received thyroid hormone replacement therapy. Thyroid functions, eGFR, 24-hour urine protein excretion, and biochemical parameters were measured at baseline and 3 months. SETTING: This study took place at a single center, a tertiary care referral and teaching hospital. RESULTS: Of 44 enrolled participants, 43 completed 3 months of follow-up. At 3 months, serum TSH levels decreased and thyroxine levels increased (P < .001 for both). Significant increases in eGFR (mean difference, 18.25 ± 19.49 mL/min/1.73 m2; 95% CI, 12.25 to 24.25, P < .001) and declines in 24-hour urine protein excretion (mean difference, -68.39 ± 125.89 mg/day; 95% CI, -107.14 to -29.65, P = .001) were observed. Serum cholesterol and low-density lipoprotein levels also significantly decreased (P < .001). CONCLUSIONS: Thyroid hormone replacement therapy in patients with severe primary hypothyroidism improves eGFR and decreases 24-hour urine protein excretion, thereby suggesting reversible alterations.

A Choline-Recognizing Monomeric Lysin, ClyJ-3m, Shows Elevated Activity against Streptococcus pneumoniae.

Streptococcus pneumoniae is a leading pathogen for bacterial pneumonia, which can be treated with bacteriophage lysins harboring a conserved choline binding module (CBM). Such lysins regularly function as choline-recognizing dimers. Previously, we reported a pneumococcus-specific lysin ClyJ comprising the binding domain from the putative endolysin gp20 from the Streptococcus phage SPSL1 and the CHAP (cysteine, histidine-dependent amidohydrolase/peptidase) catalytic domain from the PlyC lysin. A variant of ClyJ with a shortened linker, i.e., ClyJ-3, shows improved activity and reduced cytotoxicity. Resembling typical CBM-containing lysins, ClyJ-3 dimerized upon binding with choline. Herein, we further report a choline-recognizing variant of ClyJ-3, i.e., ClyJ-3m, constructed by deleting its C-terminal tail. Biochemical characterization showed that ClyJ-3m remains a monomer after it binds to choline yet exhibits improved bactericidal activity against multiple pneumococcal strains with different serotypes. In an S. pneumoniae-infected bacteremia model, a single intraperitoneal administration of 2.32 µg/mouse of ClyJ-3m showed 70% protection, while only 20% of mice survived in the group receiving an equal dose of ClyJ-3 (P < 0.05). A pharmacokinetic analysis following single intravenously doses of 0.29 and 1.16 mg/kg of ClyJ-3 or ClyJ-3m in BALB/c mice revealed that ClyJ-3m shows a similar half-life but less clearance and a greater area under curve than ClyJ-3. Taken together, the choline-recognizing monomer ClyJ-3m exhibited enhanced bactericidal activity and improved pharmacokinetic proprieties compared to those of its parental ClyJ-3 lysin. Our study also provides a new way for rational design and programmed engineering of lysins targeting S. pneumoniae.

Development of Chitosan-Based Hydrogel Containing Antibiofilm Agents for the Treatment of Staphylococcus aureus-Infected Burn Wound in Mice.

Methicillin-resistant Staphylococcus aureus (MRSA) is considered a common colonizer of burn wound and accounts for high morbidity and mortality all across the globe. Systemic antibiotic therapy which is generally prescribed for these patients has a number of limitations. These include high drug dose, toxicity, and chances of development of drug resistance. However, local delivery of drug not only addresses these limitations but also provides better efficacy at the site of infection. In the present study, hydrogel preparations were developed for the topical delivery of moxifloxacin for the treatment of S. aureus-infected burn wound. Moxifloxacin was characterized by UV, FTIR, DSC, hot-stage microscopy, NMR, and HPLC and loaded into conventional and Boswellia-containing novel gels. Gels were characterized by visual examination, pH, UV spectroscopy, and release assays. In vivo studies showed that both gels were effective in eradicating the bacteria completely from the wound site when treatment was started during the early stage of infection. On the contrary, delayed treatment of planktonic and biofilm cells with novel gel showed better efficacy as compared with conventional gel in S. aureus-infected burn wound. Histopathological analysis also showed better skin healing efficacy of novel gel than conventional gel. Our results show that moxifloxacin can be efficiently used topically in the management of burn wound infections along with other antibacterial agents. Since biofilm-mediated infections are on the rise especially in chronic bacterial disease, therefore, a preparation containing antibiofilm agent-like Boswellia as one of the excipients would be more meaningful.

Comprehensive evaluation of chitosan nanoparticle based phage lysin delivery system; a novel approach to counter S. pneumoniae infections.

Cpl-1, an endolysin derived from Cp-1 phage has been found to be effective in a number of in-vitro and in-vivo pneumococcal infection models. However its lower bioavailability under in-vivo conditions limits its applicability as therapeutic agent. In this study, Cpl-1 loaded chitosan nanoparticles were set up in order to develop a novel therapeutic delivery system to counter antibiotic resistant S. pneumoniae infections. Interactions of chitosan and Cpl-1 were studied by in-silico docking analysis. Chitosan nanoparticles and Cpl-1 loaded chitosan nanoparticles were prepared by using ionic gelation method and the process was optimized by varying chitosan:TPP ratio, pH, stirring time, stirring rate and Cpl-1 concentration. Chitosan nanoparticles and Cpl-1 loaded chitosan nanoparticles were characterized to ascertain successful formation of nanoparticles and entrapment of Cpl-1 into nanoparticles. Chitosan nanoparticles and Cpl-1 loaded nanoparticles were also evaluated for nanoparticle yield, entrapment efficiency, in-vitro release, stability, structural integrity of Cpl-1, in-vitro bioassay, swelling studies, in-vitro biodegradation and heamolysis studies. Mucoadhesion behavior of chitosan nanoparticles and Cpl-1 loaded nanoparticles was explored using mucous glycoprotein assay and ex-vivo mucoadhesion assay, both preparations exhibited their mucoadhesive nature. Cellular cytotoxicity and immune stimulation studies revealed biocompatible nature of nanoparticles. The results of this study confirm that chitosan nanoparticles are a promising biocompatible candidate for Cpl-1 delivery with a significant potential to increase bioavailability of enzyme that in turn can increase its in-vivo half life to treat S. pneumoniae infections.

Endolysins as emerging alternative therapeutic agents to counter drug-resistant infections.

Endolysins are the lytic products of bacteriophages which play a specific role in the release of phage progeny by degrading the peptidoglycan of the host bacterium. In the light of antibiotic resistance, endolysins are being considered as alternative therapeutic agents because of their exceptional ability to target bacterial cells when applied externally. Endolysins have been studied against a number of drug-resistant pathogens to assess their therapeutic ability. This review focuses on the structure of endolysins in terms of cell binding and catalytic domains, lytic ability, resistance, safety, immunogenicity and future applications. It primarily reviews recent advancements made in evaluation of the therapeutic potential of endolysins, including their origin, host range, applications, and synergy with conventional and non-conventional antimicrobial agents.

A novel wound dressing consisting of PVA-SA hybrid hydrogel membrane for topical delivery of bacteriophages and antibiotics.

The emergence of antibiotic-resistant pathogens has made the treatment of infected burn wounds even more problematical than the pre-antibiotic era. Phage therapy is now being considered a promising treatment options to fight against antibiotic resistant pathogens. Hence, we introduce a novel PVA-SA hydrogel based wound dressing system for topical delivery of bacteriophages and antibiotic to treat infected burn injuries. Hydrogel membrane provides wound healing environment while surface absorbed bacteriophages/antibiotic takes care of the local infection. Different blends of PVA and SA were crosslinked by boric acid and calcium ions to form the hydrogel membrane and assessed for ideal wound dressing properties. 1:2 blended PVA: SA membrane displayed highest swelling index, gel fraction, protein adsorption, hemocompatibility and best mechanical properties among the 3 blends studied in this study. The selected membrane was further characterised by FTIR, FESEM and TGA. Overall, self-adherent, antibacterial and biocompatible membrane was obtained as revealed by the in-vitro antibacterial assays, elution assays and cell cytotoxicity assays. The in-vivo potential was evaluated using MRSA-infected murine burn wound model revealing significant bacterial reduction, wound contraction and reduced inflammation in membrane treated groups in comparison to control group. The dual coated hydrogel membrane delivering both MR10 phage and minocycline proved to be better treatment strategy to treat the resistant burn wound infection rather than phage and antibiotic alone.

Antibiofilm potential of Seabuckthorn silver nanoparticles (SBT@AgNPs) against Pseudomonas aeruginosa.

In era of antibiotic resistance, antibacterial silver nanoparticles are considered as potential alternative therapeutic agent to combat drug resistant pathogens. The aim of present study was to evaluate the antibacterial, antibiofilm and biocompatible potential of green synthesized Seabuckthorn silver nanoparticles (SBT@AgNPs). In the study, antibacterial efficiency of SBT@AgNPs was studied against Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and methicillin resistant Staphylococcus aureus. SBT@AgNPs were found to possess high antibacterial activity which was indicated in terms of low minimum inhibitory and bactericidal concentrations (2-4 µg/ml) obtained against test pathogens. Anti-biofilm activity of SBT@AgNPs on young as well as mature P. aeruginosa biofilms was also evaluated. SBT@AgNPs were able to eradicate the P. aeruginosa biofilms, which was further confirmed by field emission scanning electron microscopy and confocal laser scanning microscopy. Quorum sensing assay also revealed the quorum quenching activity of SBT@AgNPs. Biocompatibility and cytocompatibility results demonstrated SBT@AgNPs to exhibit first-rate non-toxicity as no membrane damage on RBCs or detrimental morphology variation was seen in human dermal fibroblast. LC-MS analysis was also carried out to analyze the potential antibacterial chemical compounds present in aqueous extract of Seabuckthorn leaves. To the best of our knowledge this is first study in which green synthesized silver nanoparticles were exploited to eradicate young as well as mature biofilms of P. aeruginosa. Results showed that SBT@AgNPs are highly antibacterial, antibiofilm, nontoxic in nature and consequently can aid in biomedical applications.

Effective Topical Delivery of H-AgNPs for Eradication of Klebsiella pneumoniae-Induced Burn Wound Infection.

The aim of the present study was to explore the therapeutic efficacy of microemulsion-based delivery of histidine-capped silver nanoparticles in eradicating Klebsiella pneumoniae-induced burn wound infection. The developed microemulsion was characterized on the basis of differential light scattering, phase separation, refractive index, and specific conductance. Emulgel was prepared and characterized on the basis of thixotropy, texture, differential scanning calorimetry, and release kinetics. Emulgel was further evaluated in skin irritation and in vivo studies, namely full-thickness K. pneumoniae-induced burn wound infection treatment via topical route. Efficacy of treatment was evaluated in terms of bacterial load, histopathology, wound contraction, and other infection markers. The developed emulgel provided significant in vivo antibacterial activity of histidine-capped silver nanoparticle preparations via topical route and resulted in reduction in bacterial load, wound contraction, and enhanced skin healing as well as decrement of inflammatory markers such as malondialdehyde, myeloperoxidase, and reactive nitrogen intermediate compared to untreated animals. The present study encourages the further employment of histidine-capped silver nanoparticles along with microemulsion-based drug delivery system in combating antibiotic-resistant topical infections.

Simple drop cast method for enumeration of bacteriophages.

Phage enumeration is a basic prerequisite for application of phages in industrial, medical and other processes. Double layer agar (DLA) plaque assay is the classical method employed for isolation, detection as well as enumeration of phage particles in a solution. However, DLA method is considered cumbersome due to its specific temperature requirements and need for one petriplate with two agar layers for each phage sample. We are proposing a drop cast method for enumeration of phages which is comparatively easier and cost effective than classical DLA method as single layer of agar without any specific temperature condition is required. Added advantage of this method is that 7-10 dilutions of phage suspension can be enumerated on a single agar plate in contrast to one dilution per plate as required in DLA method. Although standard deviation in phage count was higher in the proposed method than DLA method, still drop cast method provided first-approximation phage titer which can be further validated by DLA method for more accuracy. Hence, the present method can be considered reliable, easy and cost effective for determining approximate phage count in an unknown phage suspension.

Optimization of physicochemical parameters influencing the production of prodigiosin from Serratia nematodiphila RL2 and exploring its antibacterial activity.

In the present study, role of various physicochemical parameters influencing the production of antimicrobial pigment prodigiosin from Serratia nematodiphila RL2 was determined and optimized. The pigment-producing strain was isolated and based on molecular characterization (16S rRNA sequencing), was identified as S. nematodiphila RL2. The pigment produced by S. nematodiphila RL2 was characterized by thin layer chromatography (Rf 0.94), spectrophotometrically (λmax 535 nm) and identified as prodigiosin. Optimization of production parameters of prodigiosin revealed, nutrient broth medium supplemented with lactose and yeast extract at 1% concentration each, have a positive effect on the bacterial growth (10.25-4.6 mg/ml DCW) as well as pigment production (0.46-0.6 mg/ml). Prodigiosin production (0.64 mg/ml) increases optimally after 46-48 h of incubation, at 35 °C at pH between 6 and 7 with addition of metal ions such as Uranyl acetate. An increase of 65% in prodigiosin production (0.46-0.76 mg/ml) was observed after optimizing the various production parameters than unoptimized conditions. Antimicrobial activity of the prodigiosin was also evaluated and found to be effective antimicrobial agent against bacterial pathogens including Listeria sp., Pseudomonas sp., Yersinia sp. and Shigella sp. Present study indicate that S. nematodiphila RL2 is a potent source of pigment prodigiosin which can be further explored for production of prodigiosin.

Supramolecular nano-engineered lipidic carriers based on diflunisal-phospholipid complex for transdermal delivery: QbD based optimization, characterization and preclinical investigations for management of rheumatoid arthritis.

Diflunisal (DIF) is used for treatment of rheumatoid arthritis, osteoarthritis etc. DIF-phospholipid complex (DIF-PL complex) was prepared by solvent-evaporation method and characterized by molecular docking studies, SEM, FTIR, DSC, PXRD studies. Further, the DIF-PL complex was incorporated into supramolecular nano-engineered lipidic carriers (SNLCs) for transdermal delivery. The optimization exercise was done using Face centered cubic design (FCCD) after screening of variables by L8 Taguchi orthogonal array design. The optimized SNLC formulation depicted average particle size (188.1nm), degree of entrapment (86.77±3.33%), permeation flux (5.47±0.48µg/cm2/h) and skin retention (17.72±0.68µg/cm2). The dermatokinetic studies revealed the higher concentration of DIF in dermis. The Confocal laser scanning microscopy (CSLM) studies revealed penetration of SNLCs into the deeper layers of skin. The results of mice ear edema depicted significant inhibition of ear edema (76.37±12.52%; p<0.05). In CFA induced rheumatoid arthritis model, the inhibition of paw edema was significantly higher (73.85±14.5%). The levels of TNF-α were reduced in synovial fluid (146.74±1.69pg/mL) and serum (132.43±2.70pg/mL). Furthermore, the licking and biting time was reduced in formalin induced hyperalgesia model. Hence, it can be concluded that dual formulation strategy based SNLCs were promising in treatment of pain and inflammation associated with rheumatoid arthritis.