Greater Antibacterial Activity Research Articles

In-vitro assessment of β-tricalcium phosphate/bredigite-ciprofloxacin (CPFX) scaffolds for bone treatment applications

In the present study, β-tricalcium phosphate (β-TCP) scaffolds with various amounts of bredigite (Bre) were fabricated by the space holder method. The effect of bredigite content on the structure, mechanical properties, in vitro bioactivity, and cell viability was investigated. The structural assessment of the composite scaffolds presented interconnected pores with diameter of 300–500 μm with around 78%–82% porosity. The results indicated that the compressive strength of the scaffolds with 20% bredigite (1.91 MPa) was improved in comparison with scaffolds with 10% bredigite (0.52 MPa), due to the reduction of the average pore and grain sizes. Also, the results showed that the bioactivity and biodegradability of β-TCP/20Bre were better than that of β-TCP/10Bre. Besides, in this study, the release kinetics of ciprofloxacin (CPFX) loaded β-TCP/Bre composites as well as the ability of scaffolds to function as a sustained release drug carrier was investigated. Drug release pattern of β-TCP/bredigite-5CPFX scaffolds exhibited the rapid burst release of 43% for 3 h along with sustained release (82%) for 32 h which is favorable for bone infection treatment. Antibacterial tests revealed that the antibacterial properties of β-TCP/bredigite scaffolds are strongly related to the CPFX concentration, wherein the scaffold containing 5% CPFX showed the most significant zone of inhibition (33 ± 0.5 mm) against Staphylococcus aureus. The higher specific surface areas of nanostructure β-TCP/bredigite scaffolds containing CPFX lead to an initial rapid release followed by constant drug delivery. MTT assay showed that the cell viability of β-TCP/bredigite scaffold loading with up to 1%–3% CPFX (95 ± 2%), is greater than for scaffolds containing 5% CPFX (84 ± 2%). In Overall, it may suggested that β-TCP/bredigite containing 1%–3% CPFX possesses great cell viability and antibacterial activity and be employed as bactericidal biomaterials and bone infection treatment.

Protein-Inorganic Hybrid Nanoflowers as Efficient Biomimetic Antibiotics in the Treatment of Bacterial Infection.

Nanozymes have been developed as new generation of biomimetic antibiotics against wound infection. However, most of new-developed nanozymes based on inorganic particles or hybrid ones usually originate from incompatible raw materials or unwanted metal salts, highly limiting their further biomedical usages. To overcome above drawbacks, it is highly required to develop novel nanozymes with great antibacterial activity by using biocompatible reagents and endogenous metal species as raw materials. Here, we demonstrated that bovine serum albumin enwrapped copper phosphate-based protein-inorganic hybrid nanoflowers possessed intrinsic peroxidase-like activity, which could be used as efficient biomimetic antibiotics against bacterial infection via the nanozyme-mediated generation of high toxic reactive oxygen species (ROS). With the admirable peroxidase-like activity, our nanoflowers could efficiently kill drug-resistance bacteria under physiological conditions, improve the wound healing after pathogen-induced infection, as well as avoid the potential tissue injury in time. Comprehensive toxicity exploration of these nanoflowers indicated their high biocompatibility and excellent biosafety. Our current strategy toward the design of protein-inorganic hybrid nanozymes with high biosafety and few side effects could provide a new paradigm for the development of nanozyme-based antibacterial platform in future.

Impacts of ε‐polylysine hydrochloride with thymol on biogenic amines formation and biochemical changes of squid ( Illex argentinus )

The effect of ε-polylysine hydrochloride (ε-PL) and thymol (TY) in the changes of biogenic amines (BAs) and the quality properties of Illex argentinus was evaluated by measuring the content of BAs, total viable count (TVC), pH, sensory score, and odor change. The experiment was divided into four groups, the control, ε-PL, TY, and the compound (ε-PL–TY) group. The results showed BAs-producing bacteria contained Enterobacteriaceae bacterium, Citrobacter braakii, Klebsiella pneumoniae, Obesumbacterium proteus, Hafnia alvei, Hafnia paralvei, and Hafnia alvei sensu. ε-PL, TY, and ε-PL–TY effectively inhibited the increase of BAs content, TBA, pH, and maintained the fresh flavor and sensory properties. ε-PL–TY was the best to reduce the content of phenethylamine, putrescine, cadaverine, and tyramine by 45.11%, 79.08%, 72.92%, and 63.53% compared with the control at the end of storage. ε-PL–TY was a promising BAs inhibitor that could protect the edible value and safety of aquatic products. Practical applications Illex argentinus is susceptible to corruption, and then microorganism in Illex argentinus will produce several biogenic amines, while the combined preservative is the most convenient way to protect its quality after postmortem. Although ε-polylysine hydrochloride has a better antibacterial activity as a preservative, the single preservative cannot exert a better effect. Thymol is a natural plant ingredient with great antioxidant properties and antibacterial activities, which had an inhibitory synergy with ε-PL in this study. ε-polylysine hydrochloride– thymol could be a promising preservative to control the biochemistry activities and protect the edible value of squid.

Bacterial cellulose/poly vinyl alcohol based wound dressings with sustained antibiotic delivery

The current work was aimed to prepare bacterial cellulose/poly vinyl alcohol (BC/PVA) wound dressings loaded with antibiotic which were prepared via freeze-thawing. The swelling ratio of BC/PVA hydrogels was in the range of 188–240%. The water loss percentage of BC was improved with the addition of PVA. 30% of the cumulative ampicillin delivery from BC/PVA hydrogels was achieved during 120 h suggesting significant role of PVA incorporation since 50% of ampicillin was released from BC after 24 h. BC/PVA hydrogels showed great antibacterial activity against E.coli and S. aureus. The results revealed that BC/PVA hydrogels presented great potential as wound dressings with high swelling ratio, low water loss percentage and slow antibiotic release properties.

TEA BIOACTIVE COMPOUNDS AS INHIBITOR OF MRSA PENICILLIN BINDING PROTEIN 2a (PBP2a): A MOLECULAR DOCKING STUDY

ABSTRACT Methicillin-Resistant Staphylococcus aureus (MRSA) is a hypervirulent multidrug- resistant bacteria. It is spreading around the globe and starting to be a global health problem. It causes bacteremia, infective endocarditis, and bloodstream infection. PBP2a is a protein responsible for MRSA’s resistance to antibiotics, especially beta-lactams. Tea contains bioactive compounds such as polyphenols. It is known to have great antibacterial activities. Therefore, this study aims to find potentials antibacterial compounds from tea polyphenols that can inhibit PBP2a in MRSA with better binding energy than the currently available drugs using the molecular docking approach. We found that theaflavin (-9,7 kcal/mol), as one of the tea polyphenols compound, has a better binding energy with ceftaroline (9,5 kcal/mol) therefore predicted to have better antibacterial activity. (−)- Epigallocatechingallate (-9,1 kcal/mol), (−)-epicatechingallate (-8,8 kcal/mol), myricetin (- 8,7 kcal/mol), quercetin (-8,5 kcal/mol), (−)-epicatechin (-8,3 kcal/mol), (−)- epigallocatechin (-8,3 kcal/mol), kaempferol (-8,3 kcal/mol), procyanidin B2 (-8,1), and theflavindigallate (-7,6 kcal/mol) also have the potential to inhibit MRSA due to its low binding energy. Key words : Molecular docking, MRSA, PBP2a, Tea polyphenols.

Antioxidant and Antimicrobial Properties of Pumpkin (Cucurbita maxima) Peel, Flesh and Seeds Powders

This research work was designed to investigate and utilize all three parts (peel, flesh and seeds) of pumpkin for their antioxidant and antimicrobial activities. Pumpkin parts were separated, dried, grinded to powder and extracted by using 80% methanol. Percentage yield of pumpkin peel, flesh and seeds extracts, was found 12.37±0.10, 8.84±0.07 and 3.53±0.06% respectively. DPPH free radical scavenging activity (mg AAE/100 g) of pumpkin peel, flesh and seeds extracts was found 13.00±0.08, 10.58:0.06 and 16.53±0.09 respectively. All three types of extracts exhibited prominent antifungal activities against four fungal strains Candida albicans, Fusarium oxysporum, Mucor miehei and Trichoderma spp. Pumpkin seeds extracts exhibited greater zone of inhibition against these fungal strains as compared to pumpkin peel and flesh extracts. For antibacterial study four bacterial strains Salmonella typhi, Escherichia coli , Bacillus subtilis and Streptococcus aureus were used. Pumpkin flesh extracts exhibited greater antibacterial activities as compared to pumpkin peel and seeds extracts. Keywords: Pumpkin, Extracts, Antibacterial, Antifungal, Zone of inhibition, Free radicals DOI: 10.7176/JBAH/11-6-05 Publication date: March 31 st 2021

Enhanced anticorrosive and antibacterial performances of silver nanoparticles/polyethyleneimine/MAO composite coating on magnesium alloys

A multi-functional composite coating was fabricated on magnesium (Mg) AZ31 alloy through micro-arc oxidation (MAO) combined with self-assembly technology. Polyethyleneimine (PEI) as a medium was assembled on MAO coating based on the chemical bonding and electrostatic interactions. Adhered PEI successfully mediates the self-assembly of functional silver nanoparticles (Ag NPs) with a formation of Ag NPs/PEI/MAO (APM) composite coating. The morphology and microstructure of as-prepared APM coating were characterized by using of different technologies (e.g. scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy). Its corrosion behavior in simulated body fluid and the corresponding antibacterial performance against Staphylococcus aureus (S. aureus) were also investigated. The potentiodynamic polarization results showed that the corrosion current density of APM coated AZ31 decreased more than three orders of magnitude in comparison with that of uncoated AZ31, indicating an enhanced anticorrosive ability. Electrochemical impedance spectroscopy results further revealed that the improvement of corrosion resistance was attributed to a synergistic effect of Ag NPs/PEI and MAO. The hydrogen evolution tests confirmed that APM coating provided AZ31 an excellent corrosion protection during a relatively long term. And the antibacterial research showed that APM coated AZ31 had a great antibacterial activity. This study presents a promising approach to fabricate a multi-functional composite coating on Mg alloy, which improves the anticorrosive performance of the substrate and endows it an antibacterial activity to meet a better demand in the applications.

The Impact of Composites with Silicate-Based Glasses and Gold Nanoparticles on Skin Wound Regeneration.

The silver content of the skin regeneration ointments can influence its regeneration process but in the meantime, it can take the benefit of the antibacterial properties of silver by avoiding the bacterial infection of an open wound. In the current study, the skin healing and regeneration capacity of bioactive glass with spherical gold nanocages (BGAuIND) in the Vaseline ointments were evaluated in vivo comparing the bioactive glass (BG)-Vaseline and bioactive glass with spherical gold (BGAuSP)-Vaseline ointments. Spherical gold nanocages are stabilized with silver and as a consequence the BGAuIND exhibits great antibacterial activity. Histological examination of the cutaneous tissue performed on day 8 indicates a more advanced regeneration process in rats treated with BGAuSP-Vaseline. The histopathological examination also confirms the results obtained after 11 days post-intervention, when the skin is completely regenerated at rats treated with BGAuSP-Vaseline compared with the others groups where the healing was incomplete. This result is also confirmed by the macroscopic images of the evolution of wounds healing. As expected, the silver content influences the wound healing process but after two weeks, for all of the post-interventional trials from the groups of rats, the skin healing was completely.

Hydrophobic N-halamine based POSS block copolymer porous films with antibacterial and resistance of bacterial adsorption performances

Functional films with antimicrobial efficacies and resistance of bacterial adhesion have great potential applications. In this paper, polyhedral oligomeric silsesquioxanes-(poly(trifluoroethyl methacrylate))8 (POSS-(PTFEMA)8) block copolymer and olefinic N-halamine monomer precursor containing quaternary ammonium groups (HQS) were used to prepare antibacterial porous films. The HQS compound was chlorinated (HQS-Cl) with tert-butylhypochlorite to achieve antibacterial functionality, and the stability and regenerability of HQS-Cl were examined. The porous film was prepared from POSS-(PTFEMA)8 by the breath figure approach and the stability of the porous films was examined. The surface morphology, stability and mechanical property of the porous films were studied. Moreover, the adding and spraying methods were carried out with HQS-Cl on the pincushion porous films to obtain hydrophobic antibacterial films. The static and dynamic hydrophobic properties were investigated by water contact angle and water droplet impact behavior. In addition, the bacterial adsorption of S. aureus and E. coli O157:H7 on the flat, porous and pincushion structure films were studied. The antibacterial testing results showed that the HQS-Cl modified pincushion films had great antibacterial activity and could completely inactivate 2.38 × 106 CFU/sample of S.aureus and 3.07 × 106 CFU/sample of E. coli O157:H7 within 30 min of contact time.

Green Synthesis of Highly Dispersed Zinc Oxide Nanoparticles Supported on Silica Gel Matrix by Daphne oleoides Extract and their Antibacterial Activity.

Background: ZnO nanoparticles (ZnO-NPs) are one of the most popular metal oxide nanoparticles, which exhibit significant antibacterial properties against various pathogens. Among nanoparticle synthesis methods, the green synthesis using plant extract is considered as an eco-friendly and cost-effective method for ZnO-NPs production, compared to the chemical procedures.Background: This study aimed to evaluate the green synthesis of ZnO-NPs loaded on silica gel matrix (ZnO/SG nanocomposite) by using methanol leaf extract of Daphne oleoides as a new extract and a cost-effective method. Furthermore, the antibacterial activity of the synthesized structure is evaluated against some pathogenic bacteria and the results are compared with unsupported ZnO-NPs.Materials and Methods: For ZnO/SG nanocomposite synthesis, a solution of Zn (NO3)2 was stirred with silica gel. Then the Daphne oleoides extract was added and stirred continuously until white precipitate was formed. The precipitate was heated at 200 ˚C for calcination, and ZnO/SG nanocomposite was obtained. The phytochemical constituents of leaf extract were then analyzed by gas chromatography–mass spectrometry (GC-MS). Afterwards, the structure of ZnO-NPs on SiO2 matrix (ZnO/SG nanocomposite) was characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FTIR). Surface area measurement was also determined by Brunauer-Emmett-Teller (BET) techniques. Furthermore, the antibacterial activity of ZnO/SG nanocomposites against pathogenic bacteria was evaluated using agar-based disk diffusion method standardized by clinical and laboratory guidelines. Results: The leaf extract of Daphne oleoides encompassed five major polyphenolic components. The results of the nanocomposite structure showed that ZnO-NPs with an average particle size of 38 nm were obtained and stabilized on the silica gel matrix. The BET surface area measurement of ZnO/SG nanocomposite was compared with unsupported ZnO-NPs, and the results indicated that the surface area of ZnO/SG nanocomposite was increased. Furthermore, the structure showed more powerful antibacterial activity against pathogens than unsupported ZnO-NPs. Conclusions: Green synthesis of ZnO-NPs supported on the silica gel matrix with the leaf extract of Daphne oleoides is a benign and effective procedure for ZnO/SG nanocomposite synthesis. Embedding ZnO-NPs in silica gel matrix prevents the agglomeration of nanoparticles and prepare homodispersed nanoparticles. This structure revealed great antibacterial activity against many pathogens.

On-Demand Antimicrobial Agent Release from Functionalized Conjugated Oligomer-Hyaluronic Acid Nanoparticles for Tackling Antimicrobial Resistance.

Controllable drug release is promising for fighting against antimicrobial resistance, which is a critical threat to human health worldwide. Herein, new hyaluronidase-responsive conjugated oligo(thiophene ethynylene) (OTE)-covalently modified hyaluronic acid (OTE-HA) nanoparticles for on-demand release of antimicrobial agents are reported. The synthesis of amphiphilic OTE-HA was carried out by esterification reaction. The resulting macromolecules were self-assembled in water to form nanoparticles, in which the hydrophobic OTE section, as bactericides, formed "cores" and the hydrophilic hyaluronic acid (HA) formed "shells". The OTE-HA nanoparticles avoid bactericide premature leakage and effectively block the dark cytotoxicity of the OTE section, possessing excellent biocompatibility. Using methicillin-resistant Staphylococcus aureus (MRSA) as an example, hyaluronidase, largely secreted by MRSA, can in situ trigger the release of OTE via hydrolyzing OTE-HA nanoparticles into fragments, even disaccharides linked with OTE. Importantly, the OTE section could effectively break cell membranes, leading to bacterial death. The half-maximal inhibitory concentration of the nanoparticles against MRSA is 3.3 μg/mL. The great antibacterial activity of OTE-HA nanoparticles against Gram-positive bacteria Streptococcus pneumoniae further confirms the controllable bactericide delivery mechanism. OTE-HA nanoparticles coated on a surface can also effectively inhibit the growth of bacteria, which holds a remarkable promise in biomedical applications. Therefore, this work provides a favorable strategy of on-demand and in situ drug release for sterilization and defeating antimicrobial resistance.

Porphyrin Alternating Copolymer Vesicles for Photothermal Drug-Resistant Bacterial Ablation and Wound Disinfection.

In the past two decades, polymer vesicles have aroused widespread interest and made significant developments. However, the applications of polymer vesicles in anti-infective therapy are still limited. Here, we construct a polymer vesicle (TPPBV) from a porphyrin alternating copolymer P(TPP-a-BDE) with a high photothermal conversion efficiency (54.1%), which is attributed to the unique chain-folding mechanisms of the alternating copolymer. In particular, TPPBVs exhibit great photothermal antibacterial activity against both Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) and Gram-negative extended-spectrum β-lactamases Escherichia coli (ESBL E. coli). Moreover, TPPBVs present a specific antibiofilm effect, and they also have remarkable therapeutic effects in vivo on an MRSA-infected mice model. We believe that the porphyrin alternating copolymer vesicles for photothermal bacterial ablation reported here will extend the applications of polymer vesicles.

Metagenomic Analysis Reveals the Mechanism for the Observed Increase in Antibacterial Activity of Penicillin against Uncultured Bacteria Candidatus Liberibacter asiaticus Relative to Oxytetracycline in Planta.

Citrus huanglongbing (HLB) is a devastating disease for the citrus industry. The previous studies demonstrated that oxytetracycline and penicillin are effective antibiotics against Candidatus Liberibacter asiaticus (CLas). However, since CLas is uncultured, the mechanisms of action of antibiotics against CLas are still unclear. It was recently reported that the endophytic microbial communities are associated with the progression of citrus HLB after oxytetracycline and penicillin treatment. Therefore, we hypothesize that penicillin has greater antibacterial activity against CLas than oxytetracycline, which may be associated with the alteration of the structure and function of endophytic microbial communities in HLB-affected citrus in response to these antibiotics. To test this hypothesis, the microbiome of HLB-affected citrus leaves treated with these two antibiotics was analyzed using a metagenomic method. Our results indicate that the microbial structure and function in HLB-affected citrus were altered by these two antibiotics. The relative abundance of beneficial bacterial species, including Streptomyces avermitilis and Bradyrhizobium, was higher in penicillin-treated plants compared to those treated with oxytetracycline, and the relative abundance of the bacterial species (such as Propionibacterium acnes and Synechocystis sp PCC 6803) associated with CLas survival was lower for penicillin-treated plants compared to oxytetracycline-treated plants. These results indicate that penicillin has greater antibacterial activity against CLas. Based on the metagenomic analysis, this study elucidated the mechanism for the observed increase in antibacterial activity of penicillin against CLas. The data presented here are not only invaluable for developing eco-friendly and effective biocontrol strategies to combat citrus HLB, but also provide a method for revealing mechanism of antimicrobial against uncultured bacteria in host.

Synthesis and antimicrobial activity evaluation of some new 7-substituted quinolin-8-ol derivatives: POM analyses, docking, and identification of antibacterial pharmacophore sites

Abstract Eight new 7-substituted quinolin-8-ol derivatives were synthesized moderate to good yields through quinolin-8-ol, and secondary amines as the starting reagents. The structures of the prepared compounds have been characterized by elemental analysis and 1H/13C NMR. The antimicrobial activity of this new series of heterocyclic compounds has been achieved in vitro against some bacterial strains by means of the disk method, and most of the tested compounds have shown comparable or greater antibacterial activity than nitroxoline (standard antibiotic). It was very motivating to observe that POM (Petra/Osiris/Molinspiration) bioinformatic analyses of compound 5 exhibited better antibacterial activity (MIC = 10 μg/mL against B. subtilis bacteria), and higher drug score (DS = 0.57) compared with Nitroxoline (DS = 0.47; MIC = 20 μg/mL). Molecular docking investigations were also conducted to investigate the binding affinities as well as interactions of some compounds with the target proteins.

Antibacterial Activity of Chitosan Nanoparticles: A Review

In recent years, nanotechnology has attracted attention in many fields because it has several up-and-coming novel uses. Many researchers have suggested that chitosan nanoparticles (CS-NPs) and their derivatives are one of the best nanomaterials for delivering antibacterial activity. CS-NPs have a broad spectrum of antibacterial activity, but they manifest different inhibitory efficacy against gram-negative (G−) and gram-positive (G+) bacterial species. The mechanism of antibacterial action is an intricate process that varies between G− and G+ bacteria as a result of the differences in cell wall and cell membrane chemistry. In previous studies, greater antibacterial activity was more evident against G− bacteria than G+ bacteria, whereas in some studies G+ bacteria were more sensitive. Researchers predicted that the varied responses of bacteria are caused by the mixed hydrophilicity and negative charge distribution on the bacterial surface. Moreover, its activity depends on a number of variables including bacterial target (i.e., G− or G+ bacteria) and bacterial growth, as well as its concentration, pH, zeta-potential, molecular weight, and degree of acetylation. Therefore, this review examines current research on the mechanisms and factors affecting antibacterial activity, and application of CS-NPs specifically against animal and plant pathogenic bacteria.

Chitosan-Reinforced MFC/NFC Aerogel and Antibacterial Property

MFC/NFC aerogel has water sensitivity, and it should be improved in strength in water before application. Chitosan was investigated as a MFC/NFC aerogel reinforcing agent in this paper. The reinforced aerogel showed slightly tighter structure and very good water stability and mechanical strength. FTIR disclosed the chemical bonds formed between chitosan and cellulose. Nanoparticles of silver (Ag-NPs) were loaded using the reinforced aerogel. The excellent Ag-NP monodistribution on the aerogel was expressed by TEM. Both chitosan-reinforced Ag-NPs loaded MFC aerogel and NFC aerogel and expressed great antibacterial activity, though reinforced MFC aerogel exhibited better properties, like higher BET, lighter density, more Ag-NP loading, and better distribution, than NFC aerogel in this research. Chitosan-reinforced MFC aerogel is a good potential substrate for nanoparticle loading and biocomposite making.

Preparation and characterisation of bifunctional surface-modified silicone catheter in lumen

ObjectivesThe purpose of this study was to evaluate the coating of antimicrobial peptides (AMPs) and polyvinylpyrrolidone (PVP) to the surface of a silicone catheter to reduce bacterial growth and to increase hydrophilicity, respectively. MethodsSurface characterisation was performed on bare silicone, AMP-coated, PVP-coated and AMP + PVP-coated silicone catheters using attenuated total reflectance-infrared (ATR-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and water contact angle. Antibacterial activity, antibacterial biofilm growth and XTT assay were performed on bare silicone, AMP-coated, PVP-coated and AMP + PVP-coated silicone catheters. Statistical analysis was performed by one-way ANOVA. ResultsThe water contact angle of the AMP + PVP-coated silicone catheter was 21.37 ± 2.17° compared with 107.23 ± 0.96°, 74.40 ± 1.76° and 20.77 ± 0.32° for bare silicone, AMP-coated and PVP-coated silicone catheters. Based on in vitro antimicrobial tests, the AMP + PVP-coated silicone catheter had 6.2, 2.2 and 2.5 greater antibacterial activity than that of the bare silicone catheter against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, respectively. Moreover, bacterial biofilm growth on the surface of the AMP + PVP-coated silicone catheter was minimal as characterised by scanning electron microscopy. MTT assay showed that bare silicone, AMP-coated, AMP + PVP-coated and PVP-coated silicone catheters were non-cytotoxic to 3T3 and human colon cancer (Caco-2) cells. ConclusionsThis work demonstrates that AMP + PVP-coated silicone catheters have potential clinical application prospects with improved hydrophilicity, excellent biocompatibility, antibacterial activity and a certain antibacterial biofilm effect.

In vitro antibacterial activities and molecular characterization of bacterial species isolated from farmlands against selected pathogens

This study aims to screen bacterial isolates from Olabisi Onabanjo University Farmland for antibacterial activity against pathogenic microorganisms. Agar well diffusion method was used. Isolates were identified molecularly. Chi-square test revealed significant association between isolates, antibacterial activity with likelihood p-value = 0.000 and 5% significant level. Six among thirty-five isolates exhibited antibacterial activity against the test pathogenic species. A greater antibacterial activity (50 % inhibition) was observed in Lysinibacillus sphearicus strain PRE16. It inhibited the growth of Bacillus subtilis, Staphylococcus aureus and Escherichia coli by 23.00 ± 2.00, 18.00 ± 2.00 and 20.00 ± 4.00 respectively. DNA sequencing revealed antagonist isolates as Bacillus sp. BCN2, Brochothrix thermosphacta strain P30C4, Bacillus aryabhattai strain KNUC205, Alcaligenes faecalis strain KEM24, Bacillus arsenicus strain CSD05 and Lysinibacillus sphaericus strain PRE16. Phylogenetic analysis revealed close relatedness of most isolates with Bacillus species strains. These strains are suggested to be effective for the discovery of new antibacterial agents.

Lipoic acid modified antimicrobial peptide with enhanced antimicrobial properties

RIWVIWRR-NH2 (Bac8c) is a natural antimicrobial peptide (AMP) exhibiting great antibacterial activity against Gram-negative and Gram-positive bacteria. In this work, lipoic acid was used as a fatty acid hydrophobic ligand to modify Bac8c (LA-Bac8c) to further improve its antimicrobial properties. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) assays showed that LA-Bac8c exhibited lower MIC (MBC) values against Staphylococcus aureus (S. aureus) and methicillin-resistant Staphylococcus aureus (MRSA) than Bac8c. Similar results were reflected in the antibiofilm activity towards S. aureus and MRSA, and LA-Bac8c showed better activity to the biofilm which has been formed or is being formed. In addition to this, the obvious interaction between bacteria/biofilm and LA-Bac8c was observed by microscopy. LA-Bac8c displayed strong membrane depolarization and outer membrane permeabilizing ability, and the cell membrane treated with LA-Bac8c was destroyed to the leakage of bacteria cellular components. All these data indicated LA-Bac8c could be used as a useful antimicrobial peptide with wide application prospect.

Antimicrobial properties of Andrographis paniculata (vinegar) leaf on selected human pathogens

The study was conducted to investigate the antibacterial effect of Andrographis paniculata against selected human pathogens using microbiological techniques. Different solvents were used to extract the active components from the leaves. The antibacterial activity was studied against selected human pathogens viz, Escherichia coli, Salmonella sp, Bacillus sp and Enterococccus sp. For E. coli, the range of minimum inhibition zone at 2.5 mg/ml, 5.0 mg/ml, 7.5 mg/ml and 10.0 mg/ml ethanol extract was 15 mm-25 mm while that of aqueous extract was 13 mm-17 mm with a non-detectable zone at 2.5 mg/ml concentration. Salmonella sp had inhibition zone range of 13 mm-22 mm for ethanol extract while the same organism showed minimum inhibitory zone range of 11 mm-21 mm for aqueous extract. The inhibition zone range of ethanol extract against Bacillus sp was 16.5 mm- 25.5 mm while aqueous extract had 9.5 mm-19 mm. Finally for Enterococcus sp, the inhibition zone range of ethanol extract was 15 mm-25.5 mm while aqueous extract had 9 mm-25 mm. Among the two solvents, ethanol extract showed greater antibacterial activity against the test organisms when compared with the aqueous extract at 10.0 mg/ml concentration of the extracts. Preliminary screening of phytochemicals in the leaf extract of Andrographis paniculata revealed the presence of alkaloids (6.266±0.376 mg/100g), saponins (11.055±0.134 mg/100g), flavonoids (1.175±0.067 mg/100g), tannins (2.230±0.099 mg/100g) and cyannogenic glycosides (0.870±0.057 mg/100g). The results revealed that 10.0mg/ml concentration had effect on all the test bacteria.