N-acylhomoserine lactone (AHL)-based quorum sensing (QS) is important for the regulation of proteobacterial virulence determinants. Thus, the inhibition of AHL synthases offers non-antibiotics-based therapeutic potentials against QS-mediated bacterial infections. In this work, functional AHL synthases of Pseudomonas aeruginosa LasI and RhlI were heterologously expressed in an AHL-negative Escherichia coli followed by assessments on their AHLs production using AHL biosensors and high resolution liquid chromatography-mass spectrometry (LCMS). These AHL-producing E. coli served as tools for screening AHL synthase inhibitors. Based on a campaign of screening synthetic molecules and natural products using our approach, three strongest inhibitors namely are salicylic acid, tannic acid and trans-cinnamaldehyde have been identified. LCMS analysis further confirmed tannic acid and trans-cinnemaldehyde efficiently inhibited AHL production by RhlI. We further demonstrated the application of trans-cinnemaldehyde inhibiting Rhl QS system regulated pyocyanin production in P. aeruginosa up to 42.06%. Molecular docking analysis suggested that trans-cinnemaldehyde binds to the LasI and EsaI with known structures mainly interacting with their substrate binding sites. Our data suggested a new class of QS-inhibiting agents from natural products targeting AHL synthase and provided a potential approach for facilitating the discovery of anti-QS signal synthesis as basis of novel anti-infective approach.
Silver and copper nanoparticles were produced by chemical reduction of their respective nitrates by ascorbic acid in the presence of chitosan using microwave heating. Particle size was shown to increase by increasing the concentration of nitrate and reducing the chitosan concentration. Surface zeta potentials were positive for all nanoparticles produced and these varied from 27.8 to 33.8 mV. Antibacterial activities of Ag, Cu, mixtures of Ag and Cu, and Ag/Cu bimetallic nanoparticles were tested using Bacillus subtilis and Escherichia coli. Of the two, B. subtilis proved more susceptible under all conditions investigated. Silver nanoparticles displayed higher activity than copper nanoparticles and mixtures of nanoparticles of the same mean particle size. However when compared on an equal concentration basis Cu nanoparticles proved more lethal to the bacteria due to a higher surface area. The highest antibacterial activity was obtained with bimetallic Ag/Cu nanoparticles with minimum inhibitory concentrations (MIC) of 0.054 and 0.076 mg/L against B. subtilis and E. coli, respectively.
Escherichia coli ST131 is now recognised as a leading contributor to urinary tract and bloodstream infections in both community and clinical settings. Here we present the complete, annotated genome of E. coli EC958, which was isolated from the urine of a patient presenting with a urinary tract infection in the Northwest region of England and represents the most well characterised ST131 strain. Sequencing was carried out using the Pacific Biosciences platform, which provided sufficient depth and read-length to produce a complete genome without the need for other technologies. The discovery of spurious contigs within the assembly that correspond to site-specific inversions in the tail fibre regions of prophages demonstrates the potential for this technology to reveal dynamic evolutionary mechanisms. E. coli EC958 belongs to the major subgroup of ST131 strains that produce the CTX-M-15 extended spectrum β-lactamase, are fluoroquinolone resistant and encode the fimH30 type 1 fimbrial adhesin. This subgroup includes the Indian strain NA114 and the North American strain JJ1886. A comparison of the genomes of EC958, JJ1886 and NA114 revealed that differences in the arrangement of genomic islands, prophages and other repetitive elements in the NA114 genome are not biologically relevant and are due to misassembly. The availability of a high quality uropathogenic E. coli ST131 genome provides a reference for understanding this multidrug resistant pathogen and will facilitate novel functional, comparative and clinical studies of the E. coli ST131 clonal lineage.
In this article, gelatin/copper activated faujasites (CAF) composite scaffolds were fabricated by lyophilisation technique for promoting partial thickness wound healing. The optimised scaffold with 0.5% (w/w) of CAF, G (0.5%), demonstrated pore size in the range of 10-350 μm. Agar disc diffusion tests verified the antibacterial role of G (0.5%) and further supported that bacterial lysis was due to copper released from the core of CAF embedded in the gelatin matrix. The change in morphology of bacteria as a function of CAF content in gelatin scaffold was studied using SEM analysis. The confocal images revealed the increase in mortality rate of bacteria with increase in concentration of incorporated CAF in gelatin matrix. Proficient oxygen supply to needy cells is a continuing hurdle faced by tissue engineering scaffolds. The dissolved oxygen measurements revealed that CAF embedded in the scaffold were capable of increasing oxygen supply and thereby promote cell proliferation. Also, G (0.5%) exhibited highest cell viability on NIH 3T3 fibroblast cells which was mainly attributed to the highly porous architecture and its ability to enhance oxygen supply to cells. In vivo studies conducted on Sprague Dawley rats revealed the ability of G (0.5%) to promote skin regeneration in 20 days. Thus, the obtained data suggest that G (0.5%) is an ideal candidate for wound healing applications.
The emergence of novel diseases caused by microbial pathogens and the undesirable side effects of certain antibiotics has been a recent dilemma in the medical arena. Consequently, it has stirred the discovery of many naturally occurring agents which could possibly provide important ramifications against various pharmacological targets and to combat various ailments. The main aim of the present study was to determine the antimicrobial activity of the crude methanolic extract of Piper (P.) sarmentosum against methicillin resistant Staphylococcus aureus (MRSA), Escherichia coli, Vibrio cholera and Streptococcus pneumoniae.
Silver nanoparticles (Ag NPs) were synthesized by the chemical reducing method in the external and interlamellar space of montmorillonite (MMT) as a solid support at room temperature. AgNO(3) and NaBH(4) were used as a silver precursor and reducing agent, respectively. The most favorable experimental conditions for synthesizing Ag NPs in the MMT are described in terms of the initial concentration of AgNO(3). The interlamellar space limits changed little (d-spacing = 1.24-1.47 nm); therefore, Ag NPs formed on the MMT suspension with d-average = 4.19-8.53 nm diameter. The Ag/MMT nanocomposites (NCs), formed from AgNO(3)/MMT suspension, were characterizations with different instruments, for example UV-visible, PXRD, TEM, SEM, EDXRF, FT-IR, and ICP-OES analyzer. The antibacterial activity of different sizes of Ag NPs in MMT were investigated against Gram-positive, ie, Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) and Gram-negative bacteria, ie, Escherichia coli, Escherichia coli O157:H7, and Klebsiella pneumoniae, by the disk diffusion method using Mueller-Hinton agar (MHA). The smaller Ag NPs were found to have significantly higher antibacterial activity. These results showed that Ag NPs can be used as effective growth inhibitors in different biological systems, making them applicable to medical applications.
Using the chemical reduction method, silver nanoparticles (Ag NPs) were effectively synthesized into the zeolite framework in the absence of any heat treatment. Zeolite, silver nitrate, and sodium borohydride were used as an inorganic solid support, a silver precursor, and a chemical reduction agent, respectively. Silver ions were introduced into the porous zeolite lattice by an ion-exchange path. After the reduction process, Ag NPs formed in the zeolite framework, with a mean diameter of about 2.12-3.11 nm. The most favorable experimental condition for the synthesis of Ag/zeolite nanocomposites (NCs) is described in terms of the initial concentration of AgNO(3). The Ag/zeolite NCs were characterized by ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence, and Fourier transform infrared. The results show that Ag NPs form a spherical shape with uniform homogeneity in the particle size. The antibacterial activity of Ag NPs in zeolites was investigated against Gram-negative bacteria (ie, Escherichia coli and Shigella dysentriae) and Gram-positive bacteria (ie, Staphylococcus aureus and methicillin-resistant Staphylococcus aureus) by disk diffusion method using Mueller-Hinton agar at different sizes of Ag NPs. All of the synthesized Ag/zeolite NCs were found to have antibacterial activity. These results show that Ag NPs in the zeolite framework can be useful in different biological research and biomedical applications.
In this study, antibacterial characteristic of silver/poly (lactic acid) nanocomposite (Ag/PLA-NC) films was investigated, while silver nanoparticles (Ag-NPs) were synthesized into biodegradable PLA via chemical reduction method in diphase solvent. Silver nitrate and sodium borohydride were respectively used as a silver precursor and reducing agent in the PLA, which acted as a polymeric matrix and stabilizer. Meanwhile, the properties of Ag/PLA-NCs were studied as a function of the Ag-NP weight percentages (8, 16, and 32 wt% respectively), in relation to the use of PLA. The morphology of the Ag/PLA-NC films and the distribution of the Ag-NPs were also characterized. The silver ions released from the Ag/PLA-NC films and their antibacterial activities were scrutinized. The antibacterial activities of the Ag/PLA-NC films were examined against Gram-negative bacteria (Escherichia coli and Vibrio parahaemolyticus) and Gram-positive bacteria (Staphylococcus aureus) by diffusion method using Muller-Hinton agar. The results indicated that Ag/PLA-NC films possessed a strong antibacterial activity with the increase in the percentage of Ag-NPs in the PLA. Thus, Ag/PLA-NC films can be used as an antibacterial scaffold for tissue engineering and medical application.
This study was carried out to evaluate the antibacterial activity of aqueous and organic extracts of Thymus capitatus L. (Lamiaceae) leaves and stems. Dried ground powder leaves and stems were extracted with water (aqueous extracts), ethanol, dichloromethane and hexane (Soxhlet extracts). The antibacterial activity of these extracts was evaluated against bacteria using disc diffusion method. The result obtained showed that the leaves had stronger antibacterial activity than the stems extracts. The ethanolic extract had the highest yield products and the high antibacterial activity than all other solvents. The results suggest that essential oil as non-polar organic compounds could be the main active compounds in this plant. Therefore the antibacterial activity of leaves ethanol extracts (LEE) was compared with essential oils leaves extracts (LEO) of T. capitatus. The LEO showed greater antibacterial activity than LEE. The LEO showed a broad spectrum of antibacterial activity and the Pseudomonas aeruginosa was the most sensitive bacteria.
Actinopyga lecanora, a type of sea cucumber commonly known as stone fish with relatively high protein content, was explored as raw material for bioactive peptides production. Six proteolytic enzymes, namely alcalase, papain, pepsin, trypsin, bromelain and flavourzyme were used to hydrolyze A. lecanora at different times and their respective degrees of hydrolysis (DH) were calculated. Subsequently, antibacterial activity of the A. lecanora hydrolysates, against some common pathogenic Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus) and Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas sp.) were evaluated. Papain hydrolysis showed the highest DH value (89.44%), followed by alcalase hydrolysis (83.35%). Bromelain hydrolysate after one and seven hours of hydrolysis exhibited the highest antibacterial activities against Pseudomonas sp., P. aeruginosa and E. coli at 51.85%, 30.07% and 30.45%, respectively compared to the other hydrolysates. Protein hydrolysate generated by papain after 8 h hydrolysis showed maximum antibacterial activity against S. aureus at 20.19%. The potent hydrolysates were further fractionated using RP-HPLC and antibacterial activity of the collected fractions from each hydrolysate were evaluated, wherein among them only three fractions from the bromelain hydrolysates exhibited inhibitory activities against Pseudomonas sp., P. aeruginosa and E. coli at 24%, 25.5% and 27.1%, respectively and one fraction of papain hydrolysate showed antibacterial activity of 33.1% against S. aureus. The evaluation of the relationship between DH and antibacterial activities of papain and bromelain hydrolysates revealed a meaningful correlation of four and six order functions.
beta-Lactamases have been identified as the major cause of antimicrobial resistance to beta-lactam antibiotics in Escherichia coli. The activities of ampicillin-sulbactam and amoxicillin-clavulanate as well as a range of beta-lactam antibiotics were studied with 87 clinical E. coli isolates from patients of the University Malaya Medical Center using the disc diffusion technique. Susceptible, intermediate and resistant categories were established based on the diameter of zones of inhibition set by the National Committee for Clinical Laboratory Standards (NCCLS). The isolates were then classified into 6 phenotypes according to the criteria stated in the methodology: S (susceptible to all beta-lactams); TL (resistant to aminopenicillins; amoxicillin-clavulanate susceptible and susceptible or intermediate to ampicillin-sulbactam); TI (resistant to aminopenicillins and ampicillin-sulbactam; susceptible to amoxicilin-clavulanate); TH-IRT (resistant to aminopenicillins; intermediate or resistant to amoxicillin-clavulanate; resistant to ampicillin-sulbactam); ESBL (resistant to aminopenicillins and oxyimino cephalosporins; positive results with the double-disc diffusion test); and CP (resistant to aminopenicillins, beta-lactam-beta-lactamase inhibitor combinations, oxyimino cephalosporins and cephamycins). Results showed that the TL phenotype was the commonest (40.2% of the isolates) followed by S (31%), TH-IRT (16.1%), ESBL and CP (3.4% each) and TI (2.3%). One isolate showed both ESBL and CP phenotypes while two isolates were classified as inconclusive. Representatives from each phenotype were further analysed for the presence of beta-lactamases which revealed a predominance of TEM and SHV enzyme producers. PCR-SSCP analysis of the SHV gene from all the ESBL and CP isolates revealed the predominance of SHV 5-type enzyme which was concurrent with our previous studies.
Phoenix dactylifera or date palm fruits are reported to contain natural compounds that exhibit antioxidant and antibacterial properties. This research aimed to study the effect of fruit chilling at 4 °C for 8 weeks, extract storage at -20 °C for 5 weeks, and extraction solvents (methanol or acetone) on total phenolic content (TPC), antioxidant activity and antibacterial properties of Saudi Arabian P. dactylifera cv Mabroom, Safawi and Ajwa, as well as Iranian P. dactylifera cv Mariami. The storage stability of total anthocyanin content (TAC) was also evaluated, before and after storing the extracts at -20 °C and 4 °C respectively, for 5 weeks. Mariami had the highest TAC (3.18 ± 1.40 mg cyd 3-glu/100 g DW) while Mabroom had the lowest TAC (0.54 ± 0.15 mg cyd 3-glu/100 g DW). The TAC of all extracts increased after storage. The chilling of date palm fruits for 8 weeks prior to solvent extraction elevated the TPC of all date fruit extracts, except for methanolic extracts of Mabroom and Mariami. All IC50 values of all cultivars decreased after the fruit chilling treatment. Methanol was a better solvent compared to acetone for the extraction of phenolic compounds in dates. The TPC of all cultivars extracts decreased after 5 weeks of extract storage. IC50 values of all cultivars extracts increased after extract storage except for the methanolic extracts of Safawi and Ajwa. Different cultivars exhibited different antibacterial properties. Only the methanolic extract of Ajwa exhibited antibacterial activity against all four bacteria tested: Staphylococcus aureus, Bacillus cereus, Serratia marcescens and Escherichia coli. These results could be useful to the nutraceutical and pharmaceutical industries in the development of natural compound-based products.
In the current study, facile synthesis of carboxymethyl cellulose (CMC) and sodium alginate capped silver nanoparticles (AgNPs) was examined using microwave radiation and aniline as a reducing agent. The biopolymer matrix embedded nanoparticles were synthesized under various experimental conditions using different concentrations of biopolymer (0.5, 1, 1.5, 2%), volumes of reducing agent (50, 100, 150 μL), and duration of heat treatment (30 s to 240 s). The synthesized nanoparticles were analyzed by scanning electron microscopy, UV-Vis spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy for identification of AgNPs synthesis, crystal nature, shape, size, and type of capping action. In addition, the significant antibacterial efficacy and antibiofilm activity of biopolymer capped AgNPs were demonstrated against different bacterial strains, Staphylococcus aureus MTCC 740 and Escherichia coli MTCC 9492. These results confirmed the potential for production of biopolymer capped AgNPs grown under microwave irradiation, which can be used for industrial and biomedical applications.
OBJECTIVE: To identify commonly reported community-acquired organisms and antimicrobial resistance patterns exhibited by Gram-positive and Gram-negative pathogens among pilgrims visiting emergency care departments in Makkah.
METHOD: The study was designed as a retrospective audit of all patients (pilgrims) admitted to two hospitals and residing in the city of Makkah, Saudi Arabia.
RESULTS: Among 374 isolates, Gram-negative pathogens accounted for 280 (75%), while the remaining 94 (25%) were Gram-positive organisms. Among all isolated pathogens, the highest resistance was observed for amoxicillin-clavulanic acid. Klebsiella pneumoniae had the highest resistance to amoxicillin-clavulanic acid and ampicillin. Most of the organisms were sensitive to tobramycin except Acinetobacter baumannii (n=3, 50%), Escherichia coli (n=4, 57%), and K. pneumoniae (n=6, 46%).
CONCLUSION: Overall, a high resistance was observed for beta-lactam antibiotics. In addition, a high resistance was noted for ceftazidime with A. baumannii species (n=16, 77%). However, for quinolones, the highest resistance to ciprofloxacin was observed for E. coli, A. baumannii, methicillin-resistant Staphylococcus aureus, and K. pneumoniae.
KEYWORDS: Antimicrobial resistance; Community-acquired organisms; Makkah; Pilgrims
Malabaricones A-C (1-3) and giganteone A (4) were isolated from the bark of Myristica cinnamomea King. Their structures were elucidated and characterized by means of NMR and MS spectral analyses. These isolates were evaluated for their anti-quorum sensing activity using quorum sensing biosensors, namely Escherichia coli [pSB401] and Escherichia coli [pSB1075], whereby the potential of giganteone A (4) as a suitable anti-quorum sensing agent was demonstrated.
The marine soft corals Sarcophyton trocheliophorum crude extracts possessed antimicrobial activity towards pathogenic bacterial strains, i.e. Bacillus cereus, Salmonella typhi, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Bioassay-guided fractionation indicated that the antimicrobial effect was due to the presence of terpenoid bioactive derivatives. Further biological assays of the n-hexane fractions were carried out using turbidity assay, inhibition zone assay and minimum inhibitory concentration for investigating the growth-inhibition effect towards the Gram-positive and Gram-negative bacteria. The fractions were screened and the structure of the isolated compound was justified by interpretation of the spectroscopic data, mainly mass spectrometry (GC-MS). The structure was assigned as (5S)-3-[(3E,5S)-5-hydroxy-3-hepten-6-yn-1-yl]-5-methyl-2(5H)-furanone and was effective at concentrations as low as 0.20 mg/mL. The above findings, in the course of our ongoing research on marine products, may implicate that the profound anti-microbial activity of the S. trocheliophorum soft corals, inhabiting the red sea reefs, is attributed to the presence of growth-inhibiting secondary metabolites mainly terpenoids.
The development of reliable and ecofriendly approaches for the production of nanomaterials is a significant aspect of nanotechnology nowadays. One of the most important methods, which shows enormous potential, is based on the green synthesis of nanoparticles using plant extract. In this paper, we aimed to develop a rapid, environmentally friendly process for the synthesis silver nanoparticles using aqueous extract of sumac. The bioactive compounds of sumac extract seem to play a role in the synthesis and capping of silver nanoparticles. Structural, morphological and optical properties of the nanoparticles were characterized using FTIR, XRD, FESEM and UV-Vis spectroscopy. The formation of Ag-NP was immediate within 10 min and confirmed with an absorbance band centered at 438 nm. The mean particle size for the green synthesized silver nanoparticles is 19.81 ± 3.67 nm and is fairly stable with a zeta potential value of -32.9 mV. The bio-formed Ag-NPs were effective against E. coli with a maximum inhibition zone of 14.3 ± 0.32 mm.
The electrochemical oxidation of caffeine, a widely over-the-counter stimulant drug, has been investigated in effluent wastewater and deionized water (DIW) using graphite-poly vinyl chloride (PVC) composite electrode as anode. Effects of initial concentration of caffeine, chloride ion (Cl(-)) loading, presence of hydrogen peroxide (H2O2), sample volume, type of sample and applied voltage were determined to test and to validate a kinetic model for the oxidation of caffeine by the electrochemical oxidation process. The results revealed that the electrochemical oxidation rates of caffeine followed pseudo first-order kinetics, with rate constant values ranged from 0.006 to 0.23 min(-1) depending on the operating parameters. The removal efficiency of caffeine increases with applied voltage very significantly, suggesting a very important role of mediated oxidation process. However, the consumption energy was considered during electrochemical oxidation process. In chloride media, removal of caffeine is faster and more efficiently, although occurrence of more intermediates takes place. The study found that the adding H2O2 to the NaCl solution will inhibit slightly the electrochemical oxidation rate in comparison with only NaCl in solution. Liquid chromatography-time of flight-mass spectrometry (LC-TOF-MS) technique was applied to the identification of the by-products generated during electrochemical oxidation, which allowed to construct the proposed structure of by-products.
Tuning the characteristics of solvents to fit industrial requirements has currently become a major interest in both academic and industrial communities, notably in the field of room temperature ionic liquids (RTILs), which are considered one of the most promising green alternatives to molecular organic solvents. In this work, several sets of imidazolium-based ionic liquids were synthesized, and their toxicities were assessed towards four human pathogens bacteria to investigate how tunability can affect this characteristic. Additionally, the toxicity of particular RTILs bearing an amino acid anion was introduced in this work. EC50 values (50% effective concentration) were established, and significant variations were observed; although all studied ILs displayed an imidazolium moiety, the toxicity values were found to vary between 0.05 mM for the most toxic to 85.57 mM for the least toxic. Linear quantitative structure activity relationship models were then developed using the charge density distribution (σ-profiles) as molecular descriptors, which can yield accuracies as high as 95%.