Nano-antibiotic based on silver nanoparticles functionalized to the vancomycin-cysteamine complex for treating Staphylococcus aureus and Enterococcus faecalis.

BACKGROUND: Bacterial resistance is defined as a microorganism's capacity to develop mechanisms for resisting a determined antimicrobial. Gram-positive bacteria, such as Staphylococcus aureus (S. aureus) and Enterococcus faecalis (E. faecalis), are internationally recognized among the isolates with this resistance profile. In this context, the demand for new medicines has risen, and silver nanoparticles (AgNPs) have been highlighted, especially for their anti-bacterial effects. To develop a nano-antibiotic for treating these Gram-positive strains, we herein report synthesizing and characterizing a nano-antibiotic based on AgNPs functionalized with the complex vancomycin-cysteamine. METHODS: AgNPs were produced using the bottom-up methodology and functionalized with vancomycin modified by the carbodiimide chemistry, forming Ag@vancomycin. Susceptibility tests were performed using S. aureus and E. faecalis strains to assess the bacteriostatic and bactericidal potential of the developed nano-antibiotic. RESULTS: Fourier transform infrared spectroscopy measurements showed the efficacy of vancomycin chemical modification, and the characteristic bands of AgNPs functionalization with the antibiotic. The increase in the nano-antibiotic average hydrodynamic diameter observed by dynamic light scattering proved the presence of vancomycin at the surface of AgNPs. The data from the minimum inhibitory concentration and minimal bactericidal concentration assays tested on standard and clinical planktonic strains of S. aureus and E. faecalis presented excellent performance. CONCLUSION: The results indicate the promising development of a new nano-antibiotic in which the functionalization potentiates the bacteriostatic action of AgNPs and vancomycin with greater efficacy against Gram-positive strains.

Near-Infrared-Controlled Nanoplatform Exploiting Photothermal Promotion of Peroxidase-like and OXD-like Activities for Potent Antibacterial and Anti-biofilm Therapies.

Nanozymes that mimic peroxidase (POD) activity can convert H2O2 into bactericidal free radicals, which is referred to as chemodynamic therapy (CDT). High glutathione (GSH) levels in the infectious tissue severely limit the performance of CDT. Herein, we report a near-infrared-controlled antibacterial nanoplatform that is based on encapsulating tungsten sulfide quantum dots (WS2QDs) and the antibiotic vancomycin in a thermal-sensitive liposome. The system exploits the photothermal sensitivity of the WS2QDs to achieve selective liposome rupture for the targeted drug delivery. We determined that WS2QDs show a strong POD-like activity under physiological conditions and the oxidase-like activity, which can oxidate GSH to further improve the CDT efficacy. Moreover, we found that increased temperature promotes multiple enzyme-mimicking activities of WS2QDs. This platform exerts antibacterial effects against Gram-positive Mu50 (a vancomycin-intermediate Staphylococcus aureus reference strain) and Gram-negative Escherichia coli and disrupts biofilms for improved penetration of therapeutic agents inside biofilms. In vivo studies with mice bearing Mu50-caused skin abscess revealed that this platform confers potent antibacterial activity without obvious toxicity. Accordingly, our work illustrates that the photothermal and nanozyme properties of WS2QDs can be deployed alongside a conventional therapeutic to achieve synergistic chemodynamic/photothermal/pharmaco therapy for powerful antibacterial effects.

Demineralized bone matrix paste formulated with biomimetic PLGA microcarriers for the vancomycin hydrochloride controlled delivery: Release profile, citotoxicity and efficacy against S. aureus.

Infection and resulting bone defects caused by Staphylococcus aureus is one of the major issues in orthopaedic surgeries. Vancomycin hydrochloride (VaH) is largely used to manage these events. Here, a human derived bone paste supplemented with biopolymer microcarriers for VaH sustained delivery to merge osteoinductive and antimicrobial actions is described. In detail, different emulsion formulations were tested to fabricate micro-carriers of poly-lactic-co-glycolic acid (PLGA) and hydroxyapatite (HA) by a proprietary technology (named Supercritical Emulsion Extraction). These carriers (mean size 827 ± 68 µm; loading 47 mgVaH/gPLGA) were assembled with human demineralized bone matrix (DBM) to obtain an antimicrobial bone paste system (250 mg/0.5 cm3 w/v, carrier/DBM). Release profiles in PBS indicated a daily drug average release of about 4 µg/mL over two weeks. This concentration was close to the minimum inhibitory concentration and able to effectively inhibit the S. aureus growth in our experimental sets. Carriers cytotoxicity tests showed absence of adverse effects on cell viability at the concentrations used for paste assembly. This approach points toward the potential of the DBM-carrier-antibiotic system in hampering the bacterial growth with accurately controlled antibiotic release and opens perspectives on functional bone paste with PLGA carriers for the controlled release of bioactive molecules.

Metal-organic frameworks for on-demand pH controlled delivery of vancomycin from chitosan scaffolds.

A potential bone substitute and drug carrier system is prepared to be used in treatment of serious bone infections like osteomyelitis. Vancomycin (VAN), as an antibiotic was loaded into ZIF8 nanocrystals for a pH responsive controlled release (ZIF8/VAN). Chitosan scaffolds loaded with ZIF8/VAN were prepared by wet-spinning to obtain 3D biocompatible scaffolds. Characterization of scaffolds were performed to determine the morphology, swelling behavior and pH controlled VAN release. Antibacterial activity studies were done to investigate the effectiveness of the carrier system against Staphylococcus aureus. VAN molecule encapsulation efficiency for nanosized ZIF8 crystals was calculated as 99.3%. The results showed that the VAN loaded to ZIF8 nanocrystals was released in a pH controlled manner from the chitosan scaffolds. About 70% of the VAN was released during 8 h at pH 5.4, while this value was 55% at pH 7.4. VAN release was increased with higher dissolution of ZIF8 in acidic conditions and reached a plateau value of ~77% at the end of 48 h at pH 5.4 conditions. ZIF8 and ZIF8/VAN chitosan scaffolds showed a strong effect in the reduction of S. aureus activity in comparison to chitosan scaffolds alone. This effect was best pronounced under pH 5.4 conditions which can mimic the environment of an inflamed tissue. MC3T3-E1 preosteoblasts showed high proliferation and osteogenic activities on ZIF8 loaded chitosan scaffolds.

Effects of Microplate Type and Broth Additives on Microdilution MIC Susceptibility Assays.

The determination of antibiotic potency against bacterial strains by assessment of their minimum inhibitory concentration normally uses a standardized broth microdilution assay procedure developed more than 50 years ago. However, certain antibiotics require modified assay conditions in order to observe optimal activity. For example, daptomycin requires medium supplemented with Ca2+, and the lipoglycopeptides dalbavancin and oritavancin require Tween 80 to be added to the growth medium to prevent the depletion of free drug via adsorption to the plastic microplate. In this report, we examine systematically the effects of several different plate types on microdilution broth MIC values for a set of antibiotics against Gram-positive and Gram-negative bacteria, both in medium alone and in medium supplemented with the commonly used additives Tween 80, lysed horse blood, and 50% human serum. We observed very significant differences in measured MICs (up to 100-fold) for some lipophilic antibiotics, such as the Gram-positive lipoglycopeptide dalbavancin and the Gram-negative lipopeptide polymyxins, and found that nonspecific binding plates can replace the need for surfactant additives. Microtiter plate types and any additives should be specified when reporting broth dilution MIC values, as results can vary dramatically for some classes of antibiotics.

Biologically anchored chitosan/gelatin-SrHAP scaffold fabricated on Titanium against chronic osteomyelitis infection.

The obstacles faced to treat chronic osteomyelitis infection clinically led to the search for an ideal biomaterial, resulted in combining two major aspects of bone tissue engineering namely surface modified metallic implant and polymer nanocomposite scaffold. In the present study Gelatin - Strontium incorporated Hydroxyapatite (SrHAP) forming HG scaffold, vancomycin loaded chitosan -gelatin polyelectrolyte complex incorporated gelatin-SrHAP, forming HV scaffolds (HV1-0.5wt% and HV2-1wt% vancomycin) were investigated. The HG, HV1 and HV2 scaffolds were successfully fabricated on Cp-Ti through anchoring by treatment with dopamine, which forms a bidentate co-ordination through NH bonding. Interconnected porous morphology of the scaffolds was confirmed, besides the globular Sr-HAP found in HV2 scaffold. The total amount of vancomycin encapsulation for HV1 and HV2 scaffolds were determined to be 47.55±1.6µg and 82.45±3.5µg respectively. Among the scaffolds studied HV2 scaffold were found to have a significant antibacterial activity for both MRSA and MSSA strains compared to Cp-Ti, HG and HV1 scaffolds. The HV2 scaffold also had significantly higher% of cell viability compared to Cp-Ti, HG and HV1 scaffolds. Furthermore, the presence of the drug vancomycin had no toxic effect on the cells, rather it aided in enhanced cell proliferation and spreading.

Multifunctional nanocomplex for surface-enhanced Raman scattering imaging and near-infrared photodynamic antimicrobial therapy of vancomycin-resistant bacteria.

Since vancomycin (Van)-resistant enterococci (VRE) strains first emerged as a serious threat to public health, extensive studies focused on optical imaging and antimicrobial therapy have been performed for monitoring and microbiological control. In this study, we developed silicon 2,3-naphthalocyanine dihydroxide (Nc) and Van functionalized silica-encapsulated, silver-coated gold nanoparticles (Au@AgNP@SiO2@Nc-Van) as a novel theranostic system for surface-enhanced Raman scattering (SERS) detection and antimicrobial photodynamic therapy (aPDT) of VRE strains. The silver-coated gold nanoparticle, as the SERS-active core, exhibited excellent Raman enhancement efficacy. Results of in vitro bacterial SERS imaging revealed Van-enhanced specific binding affinity toward VRE. Meanwhile, Si(IV) naphthalocyanine, serving as a near-infrared (NIR) photosensitizer, was axially linked to the nanoparticle surface, yielding nanostructured hybrid materials that could photoinactivate VRE. Almost 4-5 logs of bacterial reduction were obtained upon in vitro photodynamic therapy of VRE treated with a nanomolar concentration of the nanocomplex. Mouse infection assays were applied for an in vivo evaluation of VRE lethality. Upon near-infrared light irradiation, this hybrid nanomaterial caused obvious infection regression and even complete eradication compared to the findings in the non-treated groups. Therefore, this novel nanosystem integrating SERS imaging and noninvasive aPDT has huge potential for applications in theranostics with regard to VRE management.

Vancomycin-modified Fe3O4@SiO2@Ag microflowers as effective antimicrobial agents.

Nanomaterials combined with antibiotics exhibit synergistic effects and have gained increasing interest as promising antimicrobial agents. In this study, vancomycin-modified magnetic-based silver microflowers (Van/Fe3O4@SiO2@Ag microflowers) were rationally designed and prepared to achieve strong bactericidal ability, a wide antimicrobial spectrum, and good recyclability. High-performance Fe3O4@SiO2@Ag microflowers served as a multifunction-supporting matrix and exhibited sufficient magnetic response property due to their 200 nm Fe3O4 core. The microflowers also possessed a highly branched flower-like Ag shell that provided a large surface area for effective Ag ion release and bacterial contact. The modified-vancomycin layer was effectively bound to the cell wall of bacteria to increase the permeability of the cell membrane and facilitate the entry of the Ag ions into the bacterium, resulting in cell death. As such, the fabricated Van/Fe3O4@SiO2@Ag microflowers were predicted to be an effective and environment-friendly antibacterial agent. This hypothesis was verified through sterilization of Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus, with minimum inhibitory concentrations of 10 and 20 µg mL-1, respectively. The microflowers also showed enhanced effect compared with bare Fe3O4@SiO2@Ag microflowers and free-form vancomycin, confirming the synergistic effects of the combination of the two components. Moreover, the antimicrobial effect was maintained at more than 90% after five cycling assays, indicating the high stability of the product. These findings reveal that Van/Fe3O4@SiO2@Ag microflowers exhibit promising applications in the antibacterial fields.

Multidrug-Resistant Enterococcal Infections: New Compounds, Novel Antimicrobial Therapies?

Over the past two decades infections due to antibiotic-resistant bacteria have escalated world-wide, affecting patient morbidity, mortality, and health care costs. Among these bacteria, Enterococcus faecium and Enterococcus faecalis represent opportunistic nosocomial pathogens that cause difficult-to-treat infections because of intrinsic and acquired resistance to a plethora of antibiotics. In recent years, a number of novel antimicrobial compound classes have been discovered and developed that target Gram-positive bacteria, including E. faecium and E. faecalis. These new antibacterial agents include teixobactin (targeting lipid II and lipid III), lipopeptides derived from nisin (targeting lipid II), dimeric vancomycin analogues (targeting lipid II), sortase transpeptidase inhibitors (targeting the sortase enzyme), alanine racemase inhibitors, lipoteichoic acid synthesis inhibitors (targeting LtaS), various oxazolidinones (targeting the bacterial ribosome), and tarocins (interfering with teichoic acid biosynthesis). The targets of these novel compounds and mode of action make them very promising for further antimicrobial drug development and future treatment of Gram-positive bacterial infections. Here we review current knowledge of the most favorable anti-enterococcal compounds along with their implicated modes of action and efficacy in animal models to project their possible future use in the clinical setting.

Spanish Broom (Spartium junceum L.) fibers impregnated with vancomycin-loaded chitosan nanoparticles as new antibacterial wound dressing: Preparation, characterization and antibacterial activity.

In this work, we propose as new wound dressing, the Spanish Broom fibers impregnated with vancomycin (VM) loaded chitosan nanoparticles. Spanish Broom fibers were extracted by patented method DiCoDe and the morphological, physical and mechanical properties were investigated. Chitosan nanoparticles were prepared by ionic gelation using different weight ratios between chitosan (CH) and tripolyphosphate (TPP). Nanoparticles were characterized in terms of size, zeta potential, yield, encapsulation efficiency, stability and drug release. Finally, the antibacterial activity against Staphylococcus aureus as well as in vitro cytotoxicity on HaCaT cells were evaluated. The best formulation CH/TPP 4:1 was selected based on the encapsulation efficiency and yield. Spanish Broom fibers impregnated with loaded nanoparticles showed an increased antibacterial activity against S. aureus compared to the same fibers containing VM without nanoparticles. Moreover, these fibers were not toxic to HaCaT keratinocytes cells. In conclusion, Spanish Broom fibers impregnated with VM loaded CH/TPP nanoparticles would appear to be a promising candidate for wound dressing application.

Antibacterial and anticancerous drug loading kinetics for (10-x)CuO-xZnO-20CaO-60SiO2-10P2O5 (2 ≤ x ≤ 8) mesoporous bioactive glasses.

In the present study, antibacterial and anticancerous drug loading kinetics for the (10-x)CuO-xZnO-20CaO-60SiO2-10P2O5 (2≤x≤8, varying in steps of 2) mesoporous bioactive glasses (MBGs) have been studied. XRD analysis of the as prepared glass samples proved its amorphous nature. Scanning electron microscopy (SEM) revealed the apatite layer formation on the surface of the MBGs after soaking for 15 days in SBF. Ion dissolution studies of calcium, phosphorous and silicon have been performed using inductively coupled plasma (ICP). FTIR and Raman analysis depicted about the presence of various bonds and groups present in the glasses. The pore size of MBGs lies in the range of 4.2-9.7 nm. Apart from this, specific surface area of the MBGs varied from 263 to 402 cm2/g. The MBGs were loaded with Doxorubicin (DOX), Vancomycin (VANCO) and Tetracycline (TETRA) drugs among which, the decreasing copper content influenced the loading properties of doxorubicin and tetracycline drugs. Vancomycin was fully loaded almost in all the MBGs, whereas other drugs depicted varying loading with respect to the copper content.

Engineered porous scaffolds for periprosthetic infection prevention.

Periprosthetic infection is a consequence of implant insertion procedures and strategies for its prevention involve either an increase in the rate of new bone formation or the release of antibiotics such as vancomycin. In this work we combined both strategies and developed a novel, multifunctional three-dimensional porous scaffold that was produced using hydroxyapatite (HA) and ß-tricalcium phosphate (ß-TCP), coupled with a pectin (PEC)-chitosan (CHIT) polyelectrolyte (PEI), and loaded with vancomycin (VCA). By this approach, a controlled vancomycin release was achieved and serial bacterial dilution test demonstrated that, after 1week, the engineered construct still inhibits the bacterial growth. Degradation tests show an excellent behavior in a physiological and acidic environment (<10% of mass loss). Furthermore, the PEI coating shows an anti-inflammatory response, and good cell proliferation and migration were demonstrated in vitro using osteoblast SAOS-2 cell line. This new engineered construct exhibits excellent properties both as an antibacterial material and as a stimulator of bone formation, which makes it a good candidate to contrast periprosthetic infection.

Development of nanoantibiotic delivery system using cockle shell-derived aragonite nanoparticles for treatment of osteomyelitis.

A local antibiotic delivery system (LADS) with biodegradable drug vehicles is recognized as the most effective therapeutic approach for the treatment of osteomyelitis. However, the design of a biodegradable LADS with high therapeutic efficacy is too costly and demanding. In this research, a low-cost, facile method was used to design vancomycin-loaded aragonite nanoparticles (VANPs) with the aim of understanding its potency in developing a nanoantibiotic bone implant for the treatment of osteomyelitis. The aragonite nanoparticles (ANPs) were synthesized from cockle shells by a hydrothermal approach using a zwitterionic surfactant. VANPs were prepared using antibiotic ratios of several nanoparticles, and the formulation (1:4) with the highest drug-loading efficiency (54.05%) was used for physicochemical, in vitro drug release, and biological evaluation. Physiochemical characterization of VANP was performed by using transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, and Zetasizer. No significant differences were observed between VANP and ANP in terms of size and morphology as both samples were cubic shaped with sizes of approximately 35 nm. The Fourier transform infrared spectroscopy of VANP indicated a weak noncovalent interaction between ANP and vancomycin, while the zeta potential values were slightly increased from -19.4±3.3 to -21.2±5.7 mV after vancomycin loading. VANP displayed 120 hours (5 days) release profile of vancomycin that exhibited high antibacterial effect against methicillin-resistant Staphylococcus aureus ATCC 29213. The cell proliferation assay showed 80% cell viability of human fetal osteoblast cell line 1.19 treated with the highest concentration of VANP (250 µg/mL), indicating good biocompatibility of VANP. In summary, VANP is a potential formulation for the development of an LADS against osteomyelitis with optimal antibacterial efficacy, good bone resorbability, and biocompatibility.

Visual and absorbance analyses of admixtures containing vancomycin and piperacillin-tazobactam at commonly used concentrations.

PURPOSE: The compatibility of vancomycin and piperacillin-tazobactam in concentrations typically used in extended-infusion dosing schemes was evaluated. METHODS: Piperacillin-tazobactam was reconstituted and diluted to concentrations of 33.75, 45, 50, 60, 67.5, 80, and 90 mg/mL. Vancomycin was diluted to concentrations of 4-8, 10, and 12 mg/mL. The resultant admixtures were visually observed after preparation against black and white backgrounds each hour between hours 1 through 4 and after 24 hours. Frozen products of each medication and brand-name Zosyn powder for reconstitution also were studied. Each combination of products and concentrations was tested for precipitation using simulated Y-site administration. Absorbance and microscopic analyses were performed to discern less perceptible incompatibilities in combinations that did not result in visual precipitation. Changes in absorbance were evaluated using two-way repeated-measures analysis of variance with post hoc Bonferroni corrections. RESULTS: No tested concentrations of piperacillin-tazobactam showed precipitations with vancomycin up to concentrations of 7 mg/mL. Piperacillin-tazobactam 80-90 mg/mL formed reversible precipitation with vancomycin 8 mg/mL. All tested concentrations of piperacillin-tazobactam formed a reversible precipitate with vancomycin 10 mg/mL. Irreversible precipitation was noted with all combinations of piperacillin-tazobactam and vancomycin 12 mg/mL. No significant changes in absorbance analyses were identified for all tested piperacillin-tazobactam concentrations and vancomycin 4-10 mg/mL compared with 0.9% sodium chloride injection (p > 0.05). Similar results were observed using frozen preparations and brand-name Zosyn. CONCLUSION: Visual, microscopic, and absorbance analyses showed no evidence of incompatibility when piperacillin-tazobactam 33.75-90 mg/mL was combined with vancomycin ≤7 mg/mL. Reversible and irreversible precipitates formed when piperacillin-tazobactam was combined with vancomycin ≥8 mg/mL.

In vitro dose and duration dependent approaches for the assessment of ameliorative effects of nanoconjugated vancomycin against Staphylococcus aureus infection induced oxidative stress in murine peritoneal macrophages.

AIMS: The present study was aimed to evaluate the in vitro ameliorative effect of nanoconjugated vancomycin (NV) against vancomycin sensitive and resistant strains of Staphylococcus aureus infection-induced oxidative stress in murine peritoneal macrophage. METHODS: Peritoneal macrophages from mice were treated with VSSA and VRSA (5 × 10(6) CFU/mL), VSSA + NV (5-250 µg/ml) and VRSA + NV (5-250 µg/ml) for 18 h, having 3 h interval in culture media; and the superoxide anion generation, lipid peroxidation, protein oxidation, antioxidant enzymes status and glutathione enzymes activity were monitored. RESULTS: The significantly increased free radical generation, lipid peroxidation, protein carbonyls and oxidized glutathione levels were observed in VSSA and VRSA treated group as compared to control group; where as reduced glutathione level, antioxidant enzymes status and glutathione dependent enzymes were decreased significantly. All these changes come near to control in NV treated group in a dose and duration dependent fashion. Among the different doses and duration intervals of NV, maximum ameliorative effect was observed by 100 µg/ml for 12 h treatment which does not produce any damage to the cell. CONCLUSIONS: These findings suggest the potential use and beneficial role of nanoconjugated vancomycin as a modulator of S. aureus infection-induced cellular damage in murine peritoneal macrophage.

In vitro elution of vancomycin from biodegradable osteoconductive calcium phosphate-polycaprolactone composite beads for treatment of osteomyelitis.

In this work, osteoconductive composite materials comprising a large volume fraction of a bioresorbable calcium phosphate ceramic (CaP) and a smaller amount of a polycaprolactone polymer (PCL) were studied as a degradable antibiotic carrier material for treatment of osteomyelitis. Beads loaded with 1 and 4wt.% vancomycin were prepared by admixing dissolved drug to an in situ synthesized dicalcium phosphate (DCP)-PCL or solution-mixed beta-tricalcium phosphate (ßTCP)-PCL composite powder followed by high pressure consolidation of the blend at room temperature. Vancomycin release was measured in phosphate-buffered saline (PBS) at 37°C. All the beads gradually released the drug over the period of 4-11weeks, depending on the composite matrix homogeneity and porosity. Mathematical modeling using the Peppas equation showed that vancomycin elution was diffusion controlled. The stability of the antibiotic after high pressure application at room temperature was demonstrated by high-performance liquid chromatography-mass spectrometry (HPLC-MS) studies and MIC testing. The preservation of the structure and activity of vancomycin during the processing of composite beads and its sustained in vitro release profile suggest that high pressure consolidated CaP-PCL beads may be useful in the treatment of chronic bone infections as resorbable delivery vehicles of vancomycin and even of thermally unstable drug substances.

Photo-activated porphyrin in combination with antibiotics: therapies against Staphylococci.

Staphylococcal infections have become difficult to treat due to antibiotic insensitivity and resistance. Antimicrobial combination therapies may minimize acquisition of resistance and photodynamic therapy is an attractive candidate for these combinations. In this manuscript, we explore combined use of antibiotics and meso-tetra (4-aminophenyl) porphine (TAPP), a cationic porphyrin, for treatment of Staphylococcus aureus contamination. We characterize the antimicrobial activity of photoactivated TAPP and show that activity is largely lost in the presence of a radical scavenger. Importantly, TAPP can be reactivated with continued, albeit attenuated, antibacterial activity. We then show that the antimicrobial activity of illuminated TAPP is additive with chloramphenicol and tobramycin for S. aureus and Escherichia coli, and synergistic for MRSA and Staphylococcus epidermidis. Chloramphenicol+methylene blue, another photosensitizer, also show additivity against S. aureus. In contrast, ceftriaxone and vancomycin do not strongly augment the low level effects of TAPP against S. aureus. Eukaryotic cells exhibit a dose-dependent toxicity with illuminated TAPP. Our results suggest that even sub-minimum inhibitory concentrations of photo-activated TAPP could be used to boost the activity of waning antibiotics. This may play an important role in treatments reliant on antibiotic controlled release systems where augmentation with photo-active agents could extend their efficacy.

Hunter screening design to understand the product variability of solid dispersion formulation of a peptide antibiotic.

The focus of present research was to understand and control the variability of solid dispersion (SD) formulation of non-ribosomal peptide antibiotic, vancomycin (VCM). Hunter screening design was constructed using seven independent variables namely melting temperature (X1), congealing temperature (X2), mixing time (X3), type of capsule shell (X4), filling method (X5), molecular weight of polyethylene glycol (PEG, X6) and surfactant type (X7), and responses measured were cumulative percentage of VCM released in 45 min (Y1) and potency (Y2). The SD formulations were prepared by melt-fusion method, and tested for dissolution, potency, and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and near infrared chemical imaging (NIR-CI). Statistically significant (p<0.05) effect of congealing temperature (X2), type of capsule shell (X4), filling method (X5), molecular weight of PEG (X6) was revealed on Y1, and R(2) of 0.992 was obtained between experimental and predicted value. None of the factors have statistically significant (p>0.05) influence on Y2. SEM, DSC and PXRD indicated crystalline nature of SD formulations. Homogeneity of SD formulations was shown by NIR-CI images. In summary, the quality of VCM SD formulations could be assured by controlling the critical factors during manufacturing.

Identifying producers of antibacterial compounds by screening for antibiotic resistance.

Microbially derived natural products are major sources of antibiotics and other medicines, but discovering new antibiotic scaffolds and increasing the chemical diversity of existing ones are formidable challenges. We have designed a screen to exploit the self-protection mechanism of antibiotic producers to enrich microbial libraries for producers of selected antibiotic scaffolds. Using resistance as a discriminating criterion we increased the discovery rate of producers of both glycopeptide and ansamycin antibacterial compounds by several orders of magnitude in comparison with historical hit rates. Applying a phylogeny-based screening filter for biosynthetic genes enabled the binning of producers of distinct scaffolds and resulted in the discovery of a glycopeptide antibacterial compound, pekiskomycin, with an unusual peptide scaffold. This strategy provides a means to readily sample the chemical diversity available in microbes and offers an efficient strategy for rapid discovery of microbial natural products and their associated biosynthetic enzymes.

Underlying the mechanism of vancomycin and human serum albumin interaction: a biophysical study.

In the present study, the binding mechanism of vancomycin with human serum albumin (HSA) was determined. Upon addition of vancomycin to HSA, the fluorescence emission was quenched and the binding constant of vancomycin with HSA was found to be 6.05 × 10(3) M(-1) at 295 K, which corresponds to -2.16 × 10(4) J·mol(-1) of free energy. The conformation of HSA was altered upon binding of vancomycin with a decrease in α helix and an increase in ß sheets and random coils, suggesting partial unfolding of the secondary structure. Molecular docking experiments found that vancomycin binds strongly with HSA at the hydrophobic pocket through hydrogen bonding and van der Waals interactions. An average binding distance of 4.71 nm has been determined on the basis of the Förster resonance energy theory. It was demonstrated that vancomycin binding to HSA causes protein structural changes.