Bacterial Inhibition Studies Research Articles

Eco-design and tunable structure-properties of chitosan-epoxy-glycerol-silicate biohybrids using integrated crosslinking

Tunable structure-properties were achieved for chitosan-epoxy-glycerol-silicate (CHTGP) biohybrids, eco-designed via integrated amine-epoxy and waterborne sol-gel crosslinking reactions. Medium molecular weight chitosan (CHT), with 83 % degree of deacetylation was prepared by microwave-assisted alkaline deacetylation of chitin. The amine group of chitosan was covalently bonded to the epoxide of 3-glycidoxypropyltrimethoxysilane (G) for further crosslinking with a sol-gel derived glycerol-silicate precursor (P) from 0.5 % to 5 %. The impact of crosslinking density on the structural morphology, thermal, mechanical, moisture-retention and antimicrobial properties of the biohybrids were characterized by FTIR, NMR, SEM, swelling and bacterial inhibition studies and contrasted with a corresponding series (CHTP) without epoxy silane. Water uptake was significantly reduced in all biohybrids with a 12 % window of variation between the two series. Properties observed in biohybrids with only epoxy-amine (CHTG) or sol-gel crosslinking reactions (CHTP), were reversed in the integrated biohybrids (CHTGP) to impart improved thermal and mechanical stability and antibacterial activity.

Enhanced antibiotic activity of ampicillin conjugated to gold nanoparticles on PEGylated rosette nanotubes.

PurposeThis work presents the preparation of a nanocomposite of ampicillin-conjugated gold nanoparticles (AuNPs) and self-assembled rosette nanotubes (RNTs), and evaluates its antibacterial properties against two strains of drug-resistant bacteria (Staphylococcus aureus [S. aureus], methicillin-resistant S. aureus [MRSA]).Materials and methodsSmall, nearly monodisperse AuNPs (1.43±0.5 nm in diameter) nucleated on the surface of polyethylene glycol-functionalized RNTs in a one-pot reaction. Upon conjugation with ampicillin, their diameter increased to 1.86±0.32 nm. The antibacterial activity of the nanocomposite against S. aureus and MRSA was tested using different concentrations of ampicillin. The cytocompatibility of the nanocomposite was also tested against human dermal fibroblasts.ResultsBased on bacterial inhibition studies, the nanocomposite demonstrated enhanced antibiotic activity against both bacterial strains. The minimum inhibitory concentration (MIC) of the nanocomposite against S. aureus was found to be 0.58 μg/mL, which was 18% lower than ampicillin alone. The nanocomposite also exhibited a 20 hrs MIC of 4 μg/mL against MRSA, approximately 10–20 times lower than previously reported values for ampicillin alone. In addition, at concentrations of 4 μg/mL of ampicillin (70 μg/mL of AuNPs), the nanocomposite showed negligible cytotoxic effects.ConclusionOur findings offer a new approach for the treatment of drug-resistant bacteria by potentiating inhibitory effects of existing antibiotics, and delivering them using a non-toxic formulation.

Search of multiple hot spots on the surface of peptidyl-tRNA hydrolase: structural, binding and antibacterial studies.

Peptidyl-tRNA hydrolase (Pth) catalyzes the breakdown of peptidyl-tRNA into peptide and tRNA components. Pth from Acinetobacter baumannii (AbPth) was cloned, expressed, purified and crystallized in a native unbound (AbPth-N) state and in a bound state with the phosphate ion and cytosine arabinoside (cytarabine) (AbPth-C). Structures of AbPth-N and AbPth-C were determined at 1.36 and 1.10 Å resolutions, respectively. The structure of AbPth-N showed that the active site is filled with water molecules. In the structure of AbPth-C, a phosphate ion is present in the active site, while cytarabine is bound in a cleft which is located away from the catalytic site. The cytarabine-binding site is formed with residues: Gln19, Trp27, Glu30, Gln31, Lys152, Gln158 and Asp162. In the structure of AbPth-N, the side chains of two active-site residues, Asn70 and Asn116, were observed in two conformations. Upon binding of the phosphate ion in the active site, the side chains of both residues were ordered to single conformations. Since Trp27 is present at the cytarabine-binding site, the fluorescence studies were carried out which gave a dissociation constant (KD) of 3.3 ± 0.8 × 10-7 M for cytarabine. The binding studies using surface plasmon resonance gave a KD value of 3.7 ± 0.7 × 10-7 M. The bacterial inhibition studies using the agar diffusion method and the biofilm inhibition assay established the strong antimicrobial potential of cytarabine. It also indicated that cytarabine inhibited Gram-negative bacteria more profoundly when compared with Gram-positive bacteria in a dose-dependent manner. Cytarabine was also effective against the drug-resistant bacteria both alone as well as in combination with other antibiotics.

Development of Absorbable, Antibiotic-Eluting Sutures for Ophthalmic Surgery.

PurposeTo develop and evaluate an antibiotic-eluting suture for ophthalmic surgery.MethodsWet electrospinning was used to manufacture sutures composed of poly(L-lactide), polyethylene glycol (PEG), and levofloxacin. Size, morphology, and mechanical strength were evaluated via scanning electron microscopy and tensile strength, respectively. In vitro drug release was quantified using high performance liquid chromatography. In vitro suture activity against Staphylococcus epidermidis was investigated through bacterial inhibition studies. Biocompatibility was determined via histological analysis of tissue sections surrounding sutures implanted into Sprague-Dawley rat corneas.ResultsSutures manufactured via wet electrospinning were 45.1 ± 7.7 μm in diameter and 0.099 ± 0.007 newtons (N) in breaking strength. The antibiotic release profile demonstrated a burst followed by sustained release for greater than 60 days. Increasing PEG in the polymer formulation, from 1% to 4% by weight, improved drug release without negatively affecting tensile strength. Sutures maintained a bacterial zone of inhibition for at least 1 week in vitro and elicited an in vivo tissue reaction comparable to a nylon suture.ConclusionsThere is a need for local, postoperative delivery of antibiotics following ophthalmic procedures. Wet electrospinning provides a suitable platform for the development of sutures that meet size requirements for ophthalmic surgery and are capable of sustained drug release; however, tensile strength must be improved prior to clinical use.Translational RelevanceNo antibiotic-eluting suture exists for ophthalmic surgery. A biocompatible, high strength suture capable of sustained antibiotic release could prevent ocular infection and preclude compliance issues with topical eye drops.

Investigation on sodium benzoate release from poly(butylene adipate-co-terephthalate)/organoclay/sodium benzoate based nanocomposite film and their antimicrobial activity.

Polymeric nanocomposites embedded with nontoxic antimicrobial agents have recently gained potential industrial significance, mainly for their applicability to preserve food quality and ensure safety. In this study, a poly(butylene adipate-co-terephthalate) (PBAT)/organoclay (CMMT) based nanocomposite film doped with sodium benzoate (SB) as antimicrobial agent was prepared by a solution mixing process. A homogenous dispersion of organoclay (cetyltrimethylammonium-modified montmorillonite [CMMT]) in PBAT matrix was observed by X-ray diffraction and transmission electron microscopy. PBAT/CMMT nanocomposite film showed higher barrier properties against water and methanol vapor compared to the PBAT film. The release of SB from PBAT and its nanocomposite film was measured and the relevant data were fitted to the Weibull model. The higher values of Weibull's shape factor and scale parameter as corroborated by experimental findings indicated faster rate of SB release from PBAT/CMMT/SB nanocomposite film, when compared to the pristine PBAT film. Bacterial inhibition studies were accomplished against 2 food pathogenic bacteria, Bacillus subtilis and Staphylococcus aureus, by determining the zone of inhibition and corresponding growth profiles. Both bacterial inhibition studies and growth profiles established that PBAT/CMMT/SB demonstrated better antimicrobial activity than PBAT/SB film. Therefore, PBAT/CMMT/SB nanocomposite film can be used for food packaging application as it showed good barrier properties and antimicrobial activity against food pathogenic bacteria.

In vitro and in vivo evaluation of Assam Bora rice starch-based bioadhesive microsphere as a drug carrier for colon targeting

Objective: The aim of this study is to develop, characterize and evaluate (in vitro and in vivo) a novel colon-targeted bioadhesive microsphere (BAM) containing metronidazole (MTZ).Methods: BAMs are prepared using Assam Bora rice starch as a natural bioadhesive polymer by a double emulsion solvent evaporation method.Results: The prepared microspheres showed a uniform spherical shape, with excellent retention time. The in vitro drug release study of the optimized formulations, in different physiological environments, confirmed the insignificant release of metronidazole in the physiological conditions of the stomach (10 – 12.5%) and small intestine (< 25%). Further, fast and major drug release in cecal content (> 90) indicated that the release of the drug was unaffected by the hostile environment of the gastrointestinal tract (GIT). In vitro bacterial inhibition studies illustrated that MTZ loaded BAMs, inhibiting metronidazole-sensitive Bacteroides fragilis and selected BAMs (F1 – F7), have an equivalent or higher zone of inhibition than the marketed formulation. An in vivo organ distribution study of MTZ revealed that Assam Bora rice starch-based microspheres were relatively intact in the upper part of GIT, and the drug was released only after reaching the colon, owing to the microbial degradation of Assam Bora rice starch by microflora residing in the colon.Conclusion: MTZ release patterns exhibited slow and extended release over longer periods of time, which shows the potential of Assam Bora rice starch microspheres as a drug carrier for an effective colon-targeted delivery system.

Development of Polysaccharide based Colon Targeted Drug Delivery System: Design and Evaluation of Assam Bora rice Starch based Matrix Tablet

The aim of this study was to develop a novel colon targeted matrix tablet containing Metronidazole (MTZ) as model drug. Matrix tablets were prepared using Assam Bora rice starch, which is essentially a natural polymer, by wet granulation technique. The granules prepared were subjected to evaluation for angle of repose, bulk density, compressibility index, Hausner's ratio, total porosity, and drug content. The developed tablets were also analysed for thickness, diameter, weight variation tests, tablet crushing strength, friability, and in vitro release studies. The granules displayed satisfactory flow properties, compressibility, Hausner's ratio and drug content. Almost all the tablet formulations showed acceptable pharmacotechnical properties and complied with the in-house developed specifications for the tested parameters. Drug release study confirmed to the initial fast release in the acidic environment of surface adhered drug followed by slow release in alkaline media subsequently leading to fast and major drug release in the caecal content. Furthermore, the release of drug was unaffected by the hostile environment of GIT which can be ascribed to microbial degradation, promptly followed by enzymatic degradation. Curve fitting proved that the drug release from the tablets followed the Higuchi model. In vitro bacterial inhibition studies illustrated that the released drugs were able to diffuse through agar medium, inhibiting MTZ sensitive Bacteroides fragilis. The selected MTZ matrix tablets (F1-F6) had zones of inhibition paralleling those of the marketed formulation.

Differential survival of bacteria ingested by zooplankton from a stratified eutrophic lake

Field studies were performed in stratified Lake Oglethorpe to isolate and identify culturable, free‐living bacterioplankton from lake water and those associated within zooplankton. Heterotrophic colony counts of whole water were lower than acridine orange epifluorescent direct counts by 3–4 orders of magnitude, whereas colony counts were increased by an order of magnitude when the lake water was fractionated for zooplankton, then treated and sonicated to release bacteria from within zooplankton. Cultured bacterial species were segregated by sampling depth among the epilimnion, metalimnion, and hypolimnion and the zooplankton fractions. Laboratory feeding experiments with Daphnia ambigua and mixed suspensions of these lake bacteria demonstrated that zooplankton‐associated bacteria survived induced gut retention in D. ambigua for 23 h longer than free‐living bacteria. Feeding rate experiments showed no difference between ingestion or clearance rates of the mixed cultured bacteria, but bacterial inhibition studies showed that survivors inhibited nonsurvivors. These studies suggest that some bacterioplankton can survive digestion and interact in guts of zooplankton.

Histopathologic and bacterial evaluation of conventional and new copper amalgams.

In vivo pulpal responses in monkeys and in vitro bacterial inhibition studies were completed on new copper amalgams, Sybraloy, Dispersalloy, Tytin and a conventional Spheraloy amalgam. Amalgams were placed in cavities lined with ZOE and in unlined cavities. Silicate and ZOE were used as controls. A total of 165 adult monkey teeth were evaluated at 3 days, 5 and 8 weeks. At 3 days the pulpal responses elicited by the copper amalgams appeared similar to conventional Spheraloy, all showing a slight to moderate response. At 5 weeks the majority of amalgams exhibited a slight pulpar response with a tubular reparative dentin under each restoration. The 8 week pulpal response showed a reduction of the inflammatory response characterized by a tubular reparative dentin with a uniform zone of predentin. Lined ZOE controls exhibited a slight response while silicate showed a moderate response with some persistent chronic inflammation. In vitro bacterial tests revealed that the various amalgams had little to no inhibitory effect on the three serotypes of S. mutans that are most prominent in humans.