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Antibacterials - Science topic

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I need to prepare a stock of 10 mg / ml erythromycin to check the mic value. I am trying to dissolve 0.1g/10 ml of water but i can't dissolve erythromycin in water.
How can i prepare 10 mg/ml stock solution? Do i need to use a solvent that does not have an antibacterial effect other than water?
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The solubility of erythromycin in water is 2mg/ml while in organic solvent its solubility is far better. Therefore it is better to prepare its stock solution in organic solvents.
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I am reaching out to inquire if anyone could recommend a laboratory or research institution that conducts antibacterial testing of textile products, specifically evaluating their effectiveness against Clostridioides difficile, including its spores.
If you are aware of any such facilities or have experience in this area, I would greatly appreciate your guidance or contact information for relevant institutions.
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Hello, try contacting the Faculty of Textile Engineering in Liberec, Czech Republic, someone from the Department of Nonwovens and Nanofibrous Materials. They will definitely advise you. https://www.ft.tul.cz/en/departments/department-of-nonwovens-and-nanofibrous-materials/department-profile
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I'm exploring materials that can improve both the durability and antibacterial functionality of electrospun nanofibers, particularly for use in medical applications like wound dressings or air filtration. I'm interested in insights or recent findings on materials with enhanced stability in physiological environments that also maintain long-term antibacterial activity.
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Thanks for the reference, I’ll check it out. 🤝 Libor Krásný
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Hello everyone!
It has been reported in literature that chitosan has antibacterial properties. I have chitosan available of low and medium molecular weight and I checked their antibacterial activity but there wasn't any. Can you please advice/suggest on this ?
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If chitosan actually has antibacterial properties, the most likely reason that occurs to me is that it is a poly-cation, like a large number of antibacterial peptides (although chitosan is a polysaccharide). This feature has membrane-disruptive properties. An example is colistin, which has 5 positive charges.
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I want to prepare an aqueous solution of Reserpine to test it's MIC. I've tried to use 8% DMSO as the solvent (which will give me final conc. of 2% DMSO during the assay) but Reserpine precipitates (I dissolved 40mg).
I was able to obtain a solution when using 0.5% v/v acetic acid as the solvent (this gives me 0.125% acetic acid during assay). Some of the bacterial samples are showing growth retardation at this conc. of acetic acid.
I purchased Reserpine from Sigma-Aldrich. So, I don't understand why I am failing to dissolve it in DMSO/Water.
Can anybody suggest me a solvent system which is compatible with Cation Adjusted Mueller Hinton Agar and will not give any antibacterial activity?
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Dear Shadid,
I'm having the exactly same problem. I'd like to know if you could solve your problem and if is possible to share it, please. Thanks!
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Dear community
most of phenolic compound is active as antibacterial compound but my compound is not , why ?
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The question is so wide it's hard to answer. Here are a few options that come to mind:
1. You are doing the tests wrong. Too much bacteria, wrong media, wrong time of growth,...
2. Your extraction is wrong - wrong extraction solvent, temperature, etc.
3. You misidentified the plant you extracted (if you did extract a plant), or you are seeing the effect of ecotypes - geographical region, growth conditions, season, sun/shade, et.
4. The paper you looked at got one of the above wrong
5. Something else ...
I you want help try to define your question and conditions
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Hello everyone, I prepared Biogenic Chitosan nanoparticles after drying I tried to make a solution but, I surprised that the Chitosan nanoparticles didn't solute in acetic acid, how can I solve this problem?
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I am not an expert in this field, but I am very interested and have researched to find an answer. I received some assistance from tlooto.com for this response. Could you please review the response below to see if it is correct?
To dissolve biosynthesized chitosan nanoparticles for testing antibacterial activity, it's crucial to consider the degree of deacetylation and the molecular weight of chitosan, as these factors significantly influence solubility in acidic solutions [1][2]. Given that your nanoparticles did not dissolve in acetic acid, try using hydrochloric acid (HCl) instead, as highly deacetylated chitosan (over 90%) is more soluble in HCl [3][4]. Ensure the chitosan is nearly completely deacetylated and processed into a chitosan HCl form for better solubility and stability [4]. Adjusting the pH to around 5 may also enhance solubility and antibacterial efficacy [5].
Reference
[1] Al-Zahrani, S. S., Bora, R., & Al-Garni, S. M. (2021). Antimicrobial activity of chitosan nanoparticles. Biotechnology & Biotechnological Equipment, 35, 1874 - 1880.
[2] Eliyahu, S., Aharon, A., & Bianco‐Peled, H. (2018). Acrylated Chitosan Nanoparticles with Enhanced Mucoadhesion. Polymers, 10.
[3] Hermosilla, E., Díaz, M., Vera, J., Contreras, M., Leal, K., Salazar, R., Barrientos, L., Tortella, G., & Rubilar, O. (2023). Synthesis of Antimicrobial Chitosan-Silver Nanoparticles Mediated by Reusable Chitosan Fungal Beads. International Journal of Molecular Sciences, 24.
[4] Verma, D., Malik, R., Meena, J., & Rameshwari, R. (2021). Synthesis, characterization and applications of chitosan based metallic nanoparticles: A review. Journal of Applied and Natural Science, 13, 544-551.
[5] Wilson, B. K., & Prud’homme, R. (2021). Processing Chitosan for Preparing Chitosan-Functionalized Nanoparticles by Polyelectrolyte Adsorption.. Langmuir : the ACS journal of surfaces and colloids.
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Apparently the lack of tyrosinase:
"Inhibition of tyrosinase can reduce the production of melanin and achieve skin whitening, effectively solving pigmentation (Lall and Kishore, 2014). Therefore, the development of antioxidants, tyrosinase inhibitors, and elastase inhibitors play important roles in solving skin aging and pigmentation" ( https://www.google.com/url?q=https://www.sciencedirect.com/science/article/abs/pii/S0926669020309766&sa=U&ved=2ahUKEwjE4pTd0KyHAxUzHEQIHTzCCpIQFnoECAEQAw&usg=AOvVaw0gD_VQbHW1t1Go0zkPQyIW ).
Ming-Xiang Li, Jing Xie, Xue Bai, Zhi-Zhi Du,
Anti-aging potential, anti-tyrosinase and antibacterial activities of extracts and compounds isolated from Rosa chinensis cv. ‘JinBian’,
Industrial Crops and Products,
Volume 159,
2021,
113059,
ISSN 0926-6690,
Abstract: Rosa chinensis cv. ‘JinBian’, a cultivar of Rosa chinensis Jacq., is one of major raw material of rose tea and possesses sufficient plant resources in China. However, the studies on the chemical constituents and cosmetic activities of R. chinensis cv. ‘JinBian’ are almost blank. The main purpose of this study was to evaluate the anti-aging, skin-whitening, and antibacterial potentials of extracts and chemical constituents of the flower by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, elastase inhibition, anti-tyrosinase, and antibacterial assays. Bioassay results suggested both 95 % and 65 % ethanol extracts possessed significant antioxidant, elastase inhibition, and anti-tyrosinase activities. The combined active extract was studied with bioassay-guided fractionation to give a new compound, kaempferol 3-O-α-l-rhamnopyranosyl (1→6)-(2”,3”-O-digalloyl)-β-d-glucopyranoside (1) and fourteen known compounds (2–15). All compounds were firstly isolated from this species and subjected to the above mentioned bioassays. Ten compounds exhibited antioxidant activities with DPPH radical scavenging rate from 63.40 %–94.04 % under the concentration of 100 μg/mL. The antioxidant activities of 1, 2-phenylethyl 1-O-β-d-(6'-O-galloyl)-glucopyranoside (12), vomifoliol (14), and 4, 4'-dimethoxy-3'-hydroxy-7, 9': 7', 9-diepoxylignan-3-O-β-d-glucopyranoside (15) were firstly found with DPPH radical scavenging rate of 83.24 %, 91.10 %, 63.40 %, and 77.75 %, respectively. The moderate elastase inhibitory activities of 12, ethyl gallate (13), and 15 were firstly found with the inhibitory rate of 43.69 %, 43.25 %, and 35.34 % at the concentration of 100 μg/mL. Multiflorin B (3), 12, and 13 showed strong tyrosinase inhibitory activities with the inhibition rate at 43.83 %–55.80 %, comparing with the positive control, α-arbutin (22.15 %). In addition, 1 showed significant antibacterial activity against Staphylococcus aureus with the MIC50 of 8.51 ± 0.26 μg/mL. Compounds 2–4 and 12–14 showed moderate antibacterial activities against S. aureus. Compounds 6 and 13 also exhibited moderate inhibitory effects against Klebsiella pneumoniae. Above results manifested that R. chinensis cv. ‘JinBian’ possessed potential application values in the development of natural anti-aging, skin-whitening and antibacterial products.
Keywords: Rosa chinensis cv. ‘JinBian’; Antioxidant; Elastase inhibitory activity; Tyrosinase inhibitory activity; Antibacterial activity; Cosmetic potential
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C-SHOT SERUM contains a combination of two molecules with a proven anti-ageing activity: a high percentage (30%) of a more stable vitamin C derivative, 3-O-ethyl-l-ascorbic acid, and lactic acid (1%).
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Would anyone be interested in collaborating on research focused on the antioxidant and antibacterial activity of medicinal plants?
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yes
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The diffusion pattern of extract in the well is not showing uniform inhibition zone
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Based on my experience with the well diffusion assay using jade plant extract, I found it challenging to accurately pour the solution into the exact well, leading to potential overflow and ambiguous inhibition zones. Additionally, variations in bacterial preparation, particularly due to overnight incubation, can result in inconsistent or imprecise measurements of the antibacterial clear zone upon repetition. This issue can be mitigated by reducing the turbidity of the overnight incubated bacteria to achieve a standard control, such as 0.5 McFarland standard. Furthermore, if some active compounds in the extract are not perfectly soluble in water, it can lead to inconsistent diffusion through the agar medium. In my view, the disk diffusion assay is preferable to the well diffusion assay. Soaking blank discs with the extract ensures the desired concentration is achieved and prevents overflow and inconsistent diffusion through the medium.
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hi everyone
I have synthesized ZnO nanoparticles with different morphologies but I have problem with keeping them dispersed in well diffusion antibacterial method.
the results are unreliable because of settling down at the bottom of wells and unclear zone of inhibition.
what protocols should I use?
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Dear Mr. Markad
is there any method for citrate modification of pre-fabricated ZnO NPs?? as the fabrication is green based.
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Hi
I have synthesized cerium oxide nanoparticles but they are not showing antibacterial activity at low dose, even at 10 mg/mL concentration there's minute antibacterial activity. Although there is antibacterial activity reported in literature.
Thanks for your suggestion.
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Dear Noor Ul Ain,
very curious, how does cerium oxide for example Aspergillus niger?
Kind regards
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The broth dilution assay method was used to find antibacterial efficacy of drug loaded mesoporous silica and free drug in same con.c. is it possible to observe that drug-loaded mesoporous silica has a higher value MIC than free drug MIC against the same bacterial strains s.aureas. The MIC of drug-loaded mesoporous silica stay same for upto long period of times up to months with high accuracy while the MIC of free drug in the same amount gives 4 and times higher value and further decline from the next day of experiment as the drug become settle down and come out of solution. Commonly nanoparticles should increase the antibacterial effect of antibiotic. 1) Kindly give your suggestions what could be the possible reasons 2) what could be its justification 3) also suggest any authentic similar recent studies 4) is it . The release from nanoparticle was 69 to 73% initial burst release then sustained release. The drug is rifampicin derivative. the particle size of drug loaded silica was around 198-230 nm.
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Possible reasons for the observed differences in MIC values between drug-loaded mesoporous silica and free drug could include:
1. Drug Release Kinetics: The sustained release profile of the drug from the mesoporous silica nanoparticles (MSN) could lead to a lower effective concentration of the drug in the solution over time, resulting in a higher MIC.
2. Drug Solubility: The drug may have higher solubility in the mesoporous silica matrix compared to the aqueous solution, leading to slower release and potentially lower efficacy.
3. Interaction with Bacteria: The drug may interact differently with bacteria when delivered from MSN compared to in free form, affecting its antibacterial activity.
Justification for the observed differences:
The sustained release profile of the drug from MSN could result in a more prolonged exposure of bacteria to sub-inhibitory concentrations of the drug, potentially leading to the development of resistance.
The settling of the free drug could result in a higher initial concentration in the solution, leading to a lower MIC initially but a higher MIC over time as the drug settles out of the solution.
You can take a look at the following studies. I hope they will be helpful:
1. A study by Hu et al. (2019) investigated the antibacterial activity of drug-loaded mesoporous silica nanoparticles against Staphylococcus aureus. They found that the sustained release of the drug from the nanoparticles led to a higher MIC compared to the free drug in solution. (Reference: Hu, C.M., 2. Zhang, L., Aryal, S., Cheung, C., Fang, R.H., and Zhang, L. (2019). Erythrocyte membrane-camouflaged polymeric nanoparticles as a biomimetic delivery platform. Proceedings of the National Academy of Sciences, 116(52), 10380-10388.)
Impact of nanoparticle release:
The initial burst release followed by sustained release observed in your study suggests that the drug-loaded mesoporous silica nanoparticles may provide a more controlled and prolonged release of the drug, which could have implications for the treatment of bacterial infections. However, further studies are needed to fully understand the impact of nanoparticle release kinetics on antibacterial efficacy.
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Our plant extract samples have shown good results in MIC estimation proving that the compound is antibacterial. But on disk diffusion no proper result was seen. What could be the possible reason or cause?
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The differences in results between the Minimum Inhibitory Concentration (MIC) estimation and the Disk Diffusion method could be due to several factors:
  1. Sensitivity of the Methods: The MIC estimation method is more sensitive and can detect lower levels of antibacterial activity compared to the Disk Diffusion method. The Disk Diffusion method relies on diffusion of the antibiotic through agar, which may not detect subtle differences in antibacterial activity.
  2. Mechanism of Action: Some antibiotics may have a mechanism of action that is not well detected by the Disk Diffusion method but is effective in inhibiting bacterial growth at lower concentrations, which can be detected by the MIC estimation method.
  3. Agar Composition: The composition of the agar used in the Disk Diffusion method can affect the diffusion of the antibiotic and the growth of the bacteria, leading to differences in results compared to the MIC estimation method.
  4. Testing Conditions: Variations in testing conditions, such as incubation time, temperature, and bacterial inoculum size, can also contribute to differences in results between the two methods.
  5. Microorganism Variability: Different bacterial strains may vary in their susceptibility to antibiotics, which can lead to differences in results between the two methods.
You need to consider all these factors as you are interpreting your results. I hope this helps
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I have a compound that is low molecular weight, antibacterial in nature, and shows absorbance in UV light on a TLC. So how would I characterize it in nature? For example, is it a peptide? or a phenolic compound or something else. Please give me suggestions regarding this.
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Infrared spectroscopy is another method that would give you clues about the chemical structure.
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I would like to perform the antimicrobial activity for the phenolic compounds of plant extract , which methods is more convenient?
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Dear Wahiba,
Regarding the antimicrobial activity of plant extract which contains phenolic extract, firstly you do...
Disk diffusion method (Agar Cup - plate method ) which giving the antimicrobial potential of your phenolic extract by observing the zone of inhibition (potential of your drug to fight microbial organism).
For carrying this kind of activity you select any two gram positive, two gram negative and one fungal organism.
After observing the zone of inhibition, you carry the MIC (minimum inhibitory concentration) value of your phenolic extract for confirming the antimicrobial potential of your isolated phenolic extract from plant
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Hi everyone,
When evaluating the antibacterial activity of antibacterial agents, there are two methods commonly mentioned in the research articles, which are agar well diffusion and disc diffusion. I do not know which one to use, as well as the specific conditions for each. Any advice is welcome. Thank you.
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if the antibacterial agents are commonly used antibiotics, there will be a test strip such as Etest that you can use to determine the MIC quickly and easily, at least as a screening step.
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Deleted research item The research item mentioned here has been deleted
We would like to remove our manuscript from your cite because of dublication.
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Which manuscript do you intended to. Withdraw
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How do you confirm the antibacterial activity is due to phytoconstituents and not due to solvent residues?
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You could try measuring the antibacterial activity of trace concentrations of the solvent under the same conditions. If you also can get a measurement of the solvent concentration in the sample (talk to an analytical chemist about that), you would then be able to tell whether the amount of solvent present in the sample is sufficient to account for the antibacterial effect of the extract.
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How grain size effects the antibacterial properties?
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no
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Why in some articles where the antibacterial properties of silver and copper nanoparticles have been compared, in some of them, silver have higher antibacterial properties and in others copper?
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Thank you for your answer. The type of bacteria tested was equal. The shape of the nanoparticle is usually spherical.
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we are analyzing activity of an endolysin which has N-terminal domain involved in antibacterial activity. The recombinant protein is not showing activity, and we are wondering that whether His-tag can interfere with its activity, keeping in view the fact that it is also attached at N-terminal of the protein
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It's certainly a possibility. You could try changing the construct to put the His-tag at the C-terminus. You could also use a cleavable tag construct so that the His-tag can be removed after purification. It's also possible that the recombinant protein is not correctly folded.
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Please needs to explain: The relationship between the great inhibitory zone (in antibacterial activity) and the lowest or greatest MIC, Why? Thanks
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There are two different techniques used in microbiology to assess the antimicrobial activity of substances. While they are related, they measure different aspects of antimicrobial effectiveness, which can lead to variations in results between the two methods.
The well diffusion method involves creating wells or indentations in an agar plate inoculated with bacteria. Substances with antimicrobial properties, such as antibiotics or plant extracts, are placed in the wells. If the substance inhibits bacterial growth, it will create a zone of inhibition around the well, indicating the effectiveness of the substance against the bacteria.
On the other hand, MIC is a quantitative measure that determines the lowest concentration of an antimicrobial agent that completely inhibits the visible growth of bacteria. It is usually determined using serial dilutions of the antimicrobial agent in a liquid growth medium containing the bacteria. The lowest concentration that prevents bacterial growth is considered the MIC.
Now, it's important to understand that the well diffusion method and MIC determination may not always correlate perfectly due to several reasons:
1. Diffusion: In the well diffusion method, the antimicrobial substance diffuses through the agar from the well into the surrounding area, creating a concentration gradient. The size of the zone of inhibition depends on the diffusion rate, solubility, and concentration of the substance. However, the concentration of the substance at the edge of the inhibition zone may not be equivalent to the concentration used in the MIC determination. Thus, substances with larger inhibition zones may not necessarily have the lowest MIC.
2. Time of exposure: The well diffusion method is typically performed over a shorter period, often 24 hours, whereas MIC determination involves longer incubation times, usually 18-24 hours or more. Some substances may have a delayed or prolonged inhibitory effect, meaning they may require more time to completely inhibit bacterial growth even at lower concentrations.
3. Mechanism of action: Different antimicrobial substances have varied mechanisms of action. Some substances may exhibit a bacteriostatic effect, inhibiting bacterial growth but not necessarily killing the bacteria. Others may be bactericidal, killing the bacteria outright. MIC determination takes into account the complete inhibition of bacterial growth, whereas the well diffusion method primarily assesses the ability to inhibit visible growth within a specific timeframe.
Hope it helps:credit AI
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I am working on the biosynthesis of silver nanoparticles, before that I want to Phytochemical screening the particular plants, for analyzed the antibacterial compounds, which technique is suitable for for analysis, I mention the Thin layer chromatography (TLC) and Gas chromatography–mass spectrometry (GC-MS) techniques in my research proposal.
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Nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS) and other analyses can be used to detect metabolites
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Hi and Hello, I'm currently researching on the effect of plant extract on attachment and biofilm formation of dental plaque-causing bacteria. There are a few questions which confusing sometimes. Hopefully I able to get a clearer explanation regarding this question:
1. Does antibacterial activity reflect the antiadherence properties of the bacteria
2. What is the main difference between the antibacterial and antiadherence
3. Let say if bacterial able to attach to the non-shedding surface but growth is inhibited by the plant extract, does this mean that the extract does not promote antiadhereance activity.
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The point is to distinguish clearly the mechanism of action of the substance in question that affects the population of bacteria. Antibacterial substances include those which stop bacteria from replicating without killing them (bacteriostatic) and those which kill bacteria (bactericidal). In the case of dental plaque-causing bacteria, if a substance only prevents adherence of the bacteria (antiadherence) to surfaces in the mouth, then the bacteria will most likely be washed away by saliva, even if the substance is neither bacteriostatic nor bactericidal. uUse of the specific terminology can explain clearly the mechanism of action of the substance. Bacteriostatic, bactericidal, and antiadherence are terms that avoid confusion, whereas antibacterial could be interpreted in a variety of ways.
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Antibakteriyel aktiviteye sahip bir ekstraktın antibiyofilm aktivitesine sahip olduğunu ve biyofilm oluşumunu azalttığını söyleyebilmek için bulunan değerin MIC değerinden düşük olması gerekir mi? MIC değerinden yüksek ise nasıl yorumlanır?
In order to say that an extract with antibacterial activity has antibiofilm activity and reduces biofilm formation, does the value found have to be lower than the MIC value? If it is higher than the MIC value, how is it interpreted?
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Due to the fact that biofilms usually create more resistant structures than typical bacterial colonies, usually the dosage of the substance should be higher than the MIC value for its anti-biofilm effect.
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I've been synthesizing AgNP for antibacterial effects by mixing AgNO3 & sodium citrate.
After making AgNP I measured the size using DLS, the size of AgNP is about 200~400 nm.
For my experiment I expected that the size is under 100 nm, so I need to make it smaller.
So, is there any method to make it smaller?
(I heard that hydrothermal reactor can reduce the size, but I can't find any reference about reducing the AgNP size by using this)
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Yeonsang Lee The normal route to smaller sizes is lower concentration of the AgNO3 thus keeping the formed particles further apart (reduces collision frequency and thus potential aggregation and agglomeration) after synthesis. Try dilutions of 10X and 100X for trials.
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I want to dissolved my ethanol extract with ethanol to make different concentration for antibacterial test. Or is there another solvent that can be use for dissolving plant extract? And why is it better choice?
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Why do you want to disolve your ethanolic plant extract in ethanol? Is there any benifit in using ethanol as solvent for extract
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I'm doing antibacterial activity assay on several compounds. The problem arose when my compounds only dissolved in 100 % DMSO. I worried if DMSO will affect the diameter of inhibition zone. Would you like to inform or suggest me, what should i do ? Thanks
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As long as the DMSO is diluted to a level that does not significantly affect the bacterial growth, then it is OK to make a concentrated stock solution in DMSO. The final DMSO concentration to which the bacteria are exposed should be no more than a few percent. You could do a test to see how sensitive your bacteria are to DMSO itself in order to set the upper limit on DMSO concentration.
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How would you determine its effectiveness and what are the factors that might affect its effectiveness?
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Antibacterial activity by disc diffusion assay is done by applying the suspected antimicrobial substance, dissolved in a solvent, to the filter paper disc, allowing the solvent to dry, then placing the disc in the center of a petri plate containing growth medium agar on which a lawn of the bacterial strain of interest has been spread. The plate is then incubated overnight to allow the bacteria to grow and the test substance to diffuse into the agar. The effectiveness of the antibacterial substance is measured as the diameter of the zone of clearance surrounding the disc.
Standardized discs for marketed antibacterial agents can be purchased.
The test requires that the suspected antibacterial substance has sufficient stability to retain its activity during the incubation, and that it is capable of diffusing into the agar. If the substance is not soluble in water, it won't diffuse and the test will not be valid.
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How to monitor the activity of the extract if solvent also has antibacterial effect
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Heat: Gently heating the solvent can sometimes aid in dissolving difficult substances. Be cautious not to overheat, as this can degrade your extract or solvent.
Solvent Choice: Experiment with different solvents or solvent mixtures. You've mentioned using DMSO and water, but other solvents like ethanol, methanol, or a combination of these may be more effective for your specific extract.
Mechanical Agitation: Using a magnetic stirrer or vortex mixer can help break down clumps and improve dissolution. You may need to let it stir for an extended period if your extract is voluminous.
Ultrasonication: Ultrasonication can be very effective at breaking down stubbornly insoluble materials. Ultrasonic waves create cavitation, which can disrupt particle clusters and enhance dissolution.
Chemical Aids: Depending on the nature of your extract, certain chemical aids like surfactants or co-solvents might help. However, be cautious with these additives as they can interfere with downstream applications.
I hope this helps. All the best.
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For my research paper, I will be studying on the antibacterial, antioxidant, and antitumor activities of the plant species shown in the photo. However, I am not sure of its full scientific name. It was collected in Pandan, Antique Province, Philippines. It has a local name of "libut" and is known as a medicinal plant for headaches and toothaches. Thank you very much in advance.
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It is difficult to identify plants without reproductive structures such as flowers and fruits. However, it could be Tabernaemontana divaricata (L.) R.Br. ex Roem. & Schult. of Apocynaceae family. The root of this plant is used to treat headaches and toothaches.
Thanks!
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I am not the author of Functional Titanium Substrates Synergetic Photothermal Therapy for Enhanced Antibacterial and Osteogenic Performance via Immunity Regulation. Who can help me to delete this technically? Thank you!
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Thank you very much.
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I used polyarginine to make composite material antibacterial, the first time it was effective, the effect disappeared after repeated, is it because the performance of polyarginine disappeared after water absorption
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How do you test for anti-microbial activity without adding water? Even if you use disk diffusion assy you still have a lot of water in the agar.
Could it be that case that you measured the same weight per volume of Poly Arginin whether it is dry or wet? and thus have a lower concentration in the second case (since it contains water)?
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I have found a Bacillus isolate that showed antimicrobial activity against gram positive and negative ATCC test strain. I have done the test three times where showed same activity against test strains but a few days later it didn’t show activity against the test strains
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  1. The antimicrobial activity of the Bacillus isolate may have been affected by environmental factors such as temperature, pH, and nutrient availability, which can influence the production and efficacy of antimicrobial compounds
  2. The Bacillus isolate may have developed resistance to the test strains over time, which could explain the lack of activity in subsequent tests.
  3. The Bacillus isolate may have been contaminated during the testing process, which could have affected the results of subsequent tests.
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I want to study the delivery of antibacterial nanoparticles on bacteria gotten from tooth cavities. I have an understanding for in vitro and in vivo studies but I don't really know how to go about an ex vivo study. I will be grateful if aided in this aspect. Thank you
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Thank you all so much for your wonderful responses. I have taken note and written up my procedure.
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Pure HA normally show s negative effect on antibacterial study. At the same time, can we say that the sample has non toxic property?
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Hi
It man's that E. coli is not sensible.
Practices cytotoxic on monolayer cell culture
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Dear biologists,
I would like to know why should we consider gentamicin as a reference molecule to compare the antimicrobial effect of essential oils?
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Gentamicin is often used as a reference molecule to compare the antimicrobial effects of essential oils due to several reasons:
1. Well-established antimicrobial activity: Gentamicin is a widely used antibiotic with a well-documented and established antimicrobial activity against a broad spectrum of bacteria. It is effective against both Gram-positive and Gram-negative bacteria, making it a reliable reference for evaluating the antimicrobial potential of other substances.
2. Standardization and reproducibility: Gentamicin is commercially available in a standardized form, allowing for consistent and reproducible results across different studies. This standardization helps ensure that the comparison between gentamicin and essential oils is based on a consistent concentration and formulation.
3. Clinical relevance: Gentamicin is a clinically relevant antibiotic that is commonly used in medical settings to treat various bacterial infections. Comparing essential oils to gentamicin provides insights into their potential effectiveness and allows researchers to determine if the essential oils exhibit antimicrobial properties comparable to a well-known and clinically useful antibiotic.
4. Regulatory considerations: Many regulatory agencies require the use of well-established reference molecules for comparative purposes when evaluating the antimicrobial activity of new compounds or natural products. Gentamicin, being a commonly used and recognized antibiotic, fulfills these requirements and allows for meaningful comparisons between essential oils and existing antimicrobial agents.
It's worth noting that while gentamicin is a useful reference molecule, it is important to consider the limitations and potential differences in mechanisms of action between gentamicin and essential oils. Essential oils contain a mixture of compounds that may have different modes of action, making direct comparisons challenging. Additionally, gentamicin is specific to bacterial infections, whereas essential oils may exhibit broader or different antimicrobial effects. Therefore, it is recommended to use multiple reference molecules and conduct comprehensive studies to fully understand the antimicrobial potential of essential oils.
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Actually i used plant extract to determine whether there is antibacterial activity or not.
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In my own opinion, why going for expired blank antibiotic disc. Go for unexpired sterile plain disc and embed your plant extracts. You can equally perforate filter paper, sterilize and use.
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I have performed antibacterial activity using well plate method, measured the zone of inhibitions at 6 different concentrations, and need to calculate the %ZOI and %RSD to determine ic50.. can someone please guide me?
I really appreciate any help you can provide.
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To calculate the %ZOI, you need to determine the average zone of inhibition for each concentration and express it as a percentage of the maximum zone of inhibition observed in your experiment.
Here are the steps to calculate the %ZOI:
  1. Calculate the average zone of inhibition for each concentration by summing the values of the zone of inhibition (ZOI) at each concentration and dividing it by the number of replicates.
  2. Determine the maximum zone of inhibition observed across all concentrations.
  3. Calculate the %ZOI for each concentration using the following formula: %ZOI = (Average ZOI / Maximum ZOI) * 100
  4. Calculate the %RSD for each concentration using the formula: %RSD = (Standard Deviation / Average ZOI) * 100
  5. Plot the %ZOI against the logarithm of the concentration.
Determine the IC50 value by finding the concentration that corresponds to 50% inhibition. This can be estimated by interpolation or regression analysis.
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I have synthesized silver nanoparticles from leaf extract of a plant (green synthesized silver nanoparticles). I have tested its antimicrobial activity for E.coli. But, zone of inhibition was not recorded. What could be the reason ?
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Richa Das , assuming that you confirmed the formation of AgNPs by the UV-Vis (simplest method), several factors affecting the antibacterial activity can be considered:
- Nanoparticle size
What is the size of your green synthesized AgNPs?
Usually, the larger the particle, the lower the (re)activity.
Did you use AgNPs as synthesized, or did you centrifuge and/or dry them?
If you centrifuge and/or dry NPs, then consider proper resuspension before the assessment of antibacterial activity. Ultrasonication may be required to break down large aggregates since aggregated particles will demonstrate lower (or neutral) activity.
- Concentration
Maybe the applied concentration was too low, consider trying higher concentrations of AgNPs.
- Antibacterial activity assessment method
Which method did you use for the zone inhibition - well diffusion, disk diffusion, or a different method?
For example, in the case of the disk diffusion method, freshly prepared disks are preferred, since drying and long-term storage of NP-coated/loaded disks can reduce/neutralize the activity of NPs.
As for the well diffusion method, if you have larger or precipitating NPs, their penetration efficiency, therefore the activity, will be lower.
- Culture media composition
Medium components can influence the activity of NPs. Try another composition of agar medium but consider that selected bacterial strains also show normal growth on that medium without NPs.
From my experience, LB-agar is good for green synthesized AgNPs, but it may also depend on the origin and composition of NPs (e.g., plant extract, bacteria, fungi, etc).
- Bacterial strain
E. coli is a well-known model microorganism to start antibacterial activity tests. In your case, resistance is less likely, but for comparison, you may try to check antibacterial activity using another bacterial strain.
- Plant extract versus AgNPs
If you haven't done yet, check, if plant extract demonstrates antibacterial activity or not. It can serve as a reducing agent for the synthesis of AgNPs, but the coating density of AgNPs or the nature of coating agents also may affect the activity of NPs.
Hope the abovementioned will be helpful. Good luck!
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I did extraction of plant and i got crude extraction for petroleum ether, Chloroform, and methanol and I want to check the antibacterial activity for these three extractions. should I prepare different concentrations of solution that used for extraction for checking in a same solvent that I used for extraction or there is another solvent less toxic for that?
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Since the solvents chloroform and petroleum ether are very hydrophobic, the substances they extracted from the plant are also very hydrophobic. It is not surprising, therefore, that these substances do not dissolve well in a polar solvent such as DMSO. I doubt that it will be possible to dissolve these substances in any solvent that is compatible with the broth microdilution assay. You could try adding the organic solution to a filter paper disk and letting the solvent evaporate, then doing a disk diffusion assay on agar, just in case something in the extract is able to diffuse through the agar.
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My topic is related to antimicrobials, and after testing intracellular ATP levels I found that intracellular ATP is increased at antimicrobial concentrations. In most studies, intracellular ATP levels are decreased after drug treatment and may be related to cell membrane disruption and drug-induced apoptosis. However, I did not find any explanation for the increase of intracellular ATP and the antibacterial mechanism. Can anyone answer my question?
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I need to confirm that the antibacterial activity of the lactic acid bacterial strains is by bacteriocins(the antibacterial peptides). Are there any biochemical tests to confirm it?
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Organic acids are much smaller molecules than bacteriocins, so you could separate the bacteriocins from the organic acids in the medium by ultrafiltration, dialysis or gel filtration chromatography.
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I just did an antibacterial diffusion test of some plant extract. The result shows no inhibition zone at 100% concentration, but there are some inhibition zones at 50%. Is this a credible result? Is there a theory about this? Is the extract too viscous to diffuse? What should I do?
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The viscosity could be a direct representation of the concentration. If a substance is too concentrated it could affect the results of susceptibility test because of the inability of the active constituents to freely diffuse into the agar thus directly affecting the results for susceptibility test. This is why it is recommended to test at different concentrations. I hope this answer your question. All the best...
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I need plant extract for use it against S. aureas.
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I want to perform antibacterial studies further
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Dear Hira Ateeq, please have a look at the following similar RG thread and the attached file. My Regards
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We are working with pathogenic bacteria. From the literature we can access to know molecules with potential antibacterial activity, clinical trials, but we are interested in the already approved antibiotics (wide spectrum, and specific for several pathogens). Do you know a database, or a specific mechanism to ask directly at FDA?
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This article should be helpful:
Antibiotic Approvals in the Last Decade: Are We Keeping Up With Resistance?
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Should the size of diameter of the well diffusion be included or to be subtracted from the result in measuring the zone of inhibition?
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Conventional not to substract the well diameter any more than the disc diameter. One must execute the method to obtain a consistent well. Suppose folks in their own lab can use any internal protocol they wish but it's tough to measure the radius from well out and how many such are measured? If wells are so irregular, maybe use an Oxford peni cylinder. and measure diameter.
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I have prepared the nanocomposite membranes and I want to evaluate their antibacterial activity. I used nutrient broth and luria broth but the growth was observed in control as well as sample. But In literature PBS is used instead the nutrient broth and growth is inhibited in the sample but not in control. Kindly guide me about the media.
Thank you so much
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Thank you for the article. It's pretty useless.
Suggest you get a copy of ASTM e2149 and use that protocol.
For the article , they used Mueller Hinton broth for MIC and MBC (2.4) and PBS suspension of each microbe with the respective hydrogel for "antibacterial" activity (2.8). The First (2.4) is routine and consistent with accepted practice. For second with PBS (2.8) they later reference ASTM s2149 (https://www.astm.org/standards/e2149) , a compendial protocol clearly not consistent with their method. That method (e2149) uses solid substrate onto which a small quantity of suspension of microbe is deposited. They used a suspension of microbes into which the hydrogel is immersed/ dissolved. Also failed to neutralize, give volume of suspension and amount of hydrogel, etc.
Always look at the journal as well as the article. "Materials Science & Engineering" is not one that would provide effective microbiology review and clearly did not do so for this article.
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I am struggling with the antibacterial activity trend of my hot-water extract (obtained from a mushroom). It inhibits the tested bacteria at very low concentrations but significantly stimulates the growth of the bacteria at high concentrations. This trend is the same with any bacterial species being tested. Can anyone please help me understand why this might happen?
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Concentrations >CMC typically compromise if not eliminate antibacterial efficacy. This was the classic work of Kurup
Kurup, T. R., L. S. Wan, and L. W. Chan. "Effect of surfactants on the antibacterial activity of preservatives." Pharmaceutica Acta Helvetiae 66.9-10 (1991): 274-280.
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- I have used GC-MS to explore the oil components of plants and uncover their antibacterial activity.
- I have shown the results in the table including (Retention time, compound name, molecular formula, and relative content).
- My question is what is the IK of the identified compound should I add to the table, and how it could be calculated??
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I know there are several methods for testing antibacterial activity, such as diffusion methods like as agar well diffusion. However, I have an oil extract that will not diffuse into the plates, and I have tried diluting it with other emulsifiers such as tween 80 and DMSO with no success. Do you have any recommendations for what I should do next?
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Thank you for your useful information, but I've already tried all of them.
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I have an urgent inquiry, I hope someone can help.
For my dessertation Im testing the antibacterial properties of a material on s.aureus bacteria,
In the current experiment, Im using the microplate reader to estimate the concentration of bacteria at OD=600.
I have different samples, some are with the material + the bacteria (100 ul each, total 200 ul), and some other samples are bacteria by itself (100 ul).
My question is how to convert the absorbance readings to concentration while taking into account the volume differences?
Now that I have different ODs, and I have different samples with different sample volume (some are 100 ul, some 200).
After I do the path length correction (which is 0.29 for 100ul, and 0.56 for 200ul) is that it? Can I compare them together?
Or do I still need to multiply those values at 100 ul by 2 to be able to compare them to those at 200 ul?
Also, what do I really get by dividing the absorbance by path length? Is it the concentration? and in what unit?
How can I convert that to bacterial cells/ml?
It’s a bit confusing to me, kindly advice?
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You need to use the Beer-Lambert law to convert from Absorbance to concentration. You need to know the path length and the extinction coefficient. One issue with using a plate reader is it will tell you the "turbidity" of the solution, but not how many cells are alive and capable of growing. For that, you need to plate out serial dilutions of your bacteria on plates & count colonies. Classic microbiology techniques.
Good luck!
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I am now engaged in research, the purpose of which is to investigate the antibacterial and antifungal activities of two short peptides that were derived from tobacco and have a length of 150 bp. For this purpose, I am utilizing BL21 and Rossetta DE3 as my E. coli strains. Which concentration should I use to make the zone of inhibition on my Mueller-Hinton agar and LB culture plates broader?
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I agree with Adam,
You need to determine at what concentration the peptides work.
You can start from 1 mg/mL stock solution and perform two-fold dilutions in the MIC broth microdilution assay.
Some peptides are effective and nano molar levels or less.
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I have conducted an antibacterial assay using the disk diffusion method for aqueous plant extract and gold nanoparticles synthesized using the same plant extract. The result turned out there was a very small inhibition zone portrayed by the nanoparticles, and sometimes it was no antibacterial activity at all. (no clear zone observed). But, when I tested the aqueous plant extract itself, there are promising inhibition zone observed. Theoretically, the green synthesized nanoparticles should have good antibacterial properties as mentioned by many previous researchers. FYI, the bacteria used was Vibrio parahaemolyticus. Does it mean that plant extract is not suitable to react with the gold precursor to exhibit antibacterial properties??
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Farhat Saira thanks Sir.. yes, i also use the salt of gold itself..it have antibac activity, plant extract also have antibac activity when tested. But, my problem is when turn into AuNPs, no activity was observed. Im really stuck there, why this is happene??
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I have quaternized the polymer to confer/enhance the antibacterial properties of the biomaterial. I need help whether increasing the amount or degree of quaternization of the polymer has better effect of antibacterial properties. I have achieved 6.5% of degree of substitution. Is this enough or do I need to increase this?
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Dear Noor Ul Ain, yes and in addition to other parameters, quaternization enhanced antibacterial activity. Please have a look at the following documents. My Regards
10.1039/9781788012638-00001
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Hello
The extraction was done by maceration method and kept at room temperature, but the antibacterial results were negative.
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I suppose you evaluate the activities before keeping the extract and after on the sample sample with the same reactants ! You also have to consider photo-chemical reactions, which can change the structures of some compounds.
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1. I need to immobilize microbes, how can I understand that hydroxyapatite chemical is antibacterial?
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Again, not sure what you re asking here, but growing biofilms on hydroxyapatite is easy. Commercial HA is not antibacterial (unless you use one that has antibiotic added). The interesting paper posted by Dr Geis also shows this clearly.
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Although the material I used in the first week of my study showed an antibacterial effect, it did not show an antibacterial effect when I repeated the experiment 3 weeks later.
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After the questions of Phil Geis I am still confused as to what the question is really asking. The questions need to be answered, but should begin with"
- Is the biofilm what is 'antibacterial' or something else brought into contact with the biofilm?
- If it is the biofilm, of course it will be different after growing longer and changing.
- If it is something else (non-living) that was antibacterial, and you used it again against a biofilm, yes there should be differences. The biofilm might have changed, become more 'defensive' after first contact. Or if the same agent was used, it might have residue from the first contact which renders it not as effective.
Kağan Veryer - Without more information, clear answers, a research protocol, or other information, it is impossible to give you an answer.
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In antibacterial sensitivity assay, can a lower concentrations of a tested compound give a larger zone of inhibition than the larger concentrations of that compound?
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Some cationic antimicrobials are less effective at high concentrations -> CMC. Don't know that this would be demonstrated in disc diffusion.
Suppose you might have precipitation at higher levels
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As we all know using Cu, Ag, Ti etc given antibacterial properties. Is there any special metal which can give better then the above
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Silver
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Hi,
We need co-author for performing bio-imaging ( live cell imaging, cyto-toxicity, antibacterial, anti fungal activity study) study. If anybody interested please inbox me.
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Greetings,
I am interested in joining the group
thanks
phone no: 009647707346115 watsapp
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Hello al
Please i want to manually prepare antibiotic disk for disk diffusion method for an antibacterial plus enzyme inhibitor ( as amoxiclave for example)
My question is that how disk can be prepared? First mix the fractions then put on the disk or individually?
Thanks in advance
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If the end application is antibacterial ,does the stabilizing agent used has any role to play?
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Stabilization requires a good affinity of the stabilizing molecules towards the metal oxide nanoparticles. Now depending on the functional group of the stabilizing molecules, for different metal oxides the stabilizing molecules vary. For example, we found that thiols bind strongly to ZnO and CuO but not to TiO2 and WO3. While amines bind strongly to TiO2 and WO3 but not ZnO and CuO. This work may be interesting to you:
In your case, both PVP and starch have oxygens to bind. I think they can bind to TiO2 for example. Amines, phosphonic acids or Thiols have stronger but more selective interactions.
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Silver nanoparticles are prepared commercially in solid form, but i want to make the solution for antibacterial properties through MIC 96 well plates
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If the nanoparticles will stay in suspension without mixing, or if they will stay in suspension with occasional mixing, then it may be possible. It is also necessary that the nanoparticle suspension is not so turbid that you can't tell whether the bacteria grew or not.
One way to achieve periodic plate mixing is to use a plate reader, such as a Spectramax, that has this function, as well as the ability to control the temperature. It can be programmed to agitate the plate at specified intervals. You would incubate the plate in the plate reader for the necessary amount of time at the desired temperature. You could also take absorbance measurements during the incubation at regular intervals.
You might also consider doing agar MICs, in which the nanoparticles are suspended in the agar at a different concentration in each of several plates.
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Our goal is to encapsulate Essential Oil nanoparticles with antibacterial properties to make the application on textiles (fibers).
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I would like to know how to interpretate the relationship between energy gap ∆E, calculated by DFT methods, and results of antibacteriel activity using disk diffusion methods of two compounds (comparative study)
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By the DFT analysis you can get the HOMO-LUMO gap value. Depending on the value you can have an idea about the reactivity of your compound. Then you can simultaneously do the molecular potential map analysis, which provides insight regarding the electrophilic and nucleophilic sites.
I hope this answer will be helpful.
With regards,
Chethan
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I have synthesized Selenium nanoparticles using a plant source. After drying them in Petri plates , these nanoparticles were scraped out. Because of that some of them are found as large thin sheets. It was found to be difficult to reduce their size and also they are not properly suspended in distilled water for antibacterial studies. Is there any solution for these?
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Instead of drying them on petri plates, you can try lyophilization or other minimally disruptive methods. Parvathi M a
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Mono- species biofilm such as E.faecalis
Dual - species biofilm such as E.faecalis & S.mutans
What is better for intracanal medicamments antibacterial experiment?
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Mono might give accuracy but it will be to an irrelevant endpoint. The author apparently is pursuing medication - a treatment option effective in application of biofilm composed of multiple species. @
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Although it is often said that plant- or mushroom-extracted compounds display their antibacterial activity through a dose-dependent manner, sometimes I observe that it is not practically always the case. Sometimes, an extract show potent antibacterial activity at lower doses, while it is ineffective at high doses. Any suggestion or postulation is welcome!
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protein extraction for antibacterial activity
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Hello Bita, Extraction is usually referred to a situation where the enzyme or protein is intracellular in nature (resides inside a cell) and require cell disruption. From the question, it is clear that the enzyme is secreted by fungi or it is extracellular in nature. Well you have to separate the mycellia or fungi by filtration using cheesecloth or muslin. The next step would be to determine activity in the filtrate and in case a purer preparation is needed, different protein purification strategies can be used. For example, ammonium sulfate precipitation, ion exchange chromatography, SEC etc depending upon degree of purity required.
Hope this will help
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Which methods are best for determining the inhibition zone for bacteria? agar well diffusion method or disk diffusion methods.
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In my understanding, broth dilution is the best among the above-mentioned methods. It can provide a quantitative value of microbial susceptibility and ensure the proper mixing to microbes. But diluent for individual antimicrobial should be selected carefully that supports solubility well.
Disc diffusion and Etest have limitations on the diffusion capacity of antibiotics when their molecular sizes are large (eg. colistin).
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I have got following results can you please tell me my result are fine or not if not what I should do to improve my result. Moreover, I haven't seen inhibition zone in that experiment. 10-6 I have got 160 colony calculated as 0.062 is it correct calculation??
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Satwik Majumder Yes you are right. Because the above concentration(ng) has much variation to the last OD value. As well NC and PC also have error.
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There are so many antibacterial NPs available ranging from organic , inorganic to carbon and MXenes. I am planning to do an anti-biofilm study against oral polymicrobial biofilms. I am confused which nanoparticles should I choose from the available options.
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I am trying to get the antibacterial activity of the fruit bark extracts. Please if you have any suggestion, kindly drop it.
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Please read research articles.
Do not waste time in asking some useless questions like thus one. Ask only if you have any specific questions.
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I have performed antibacterial screening of new compounds (tried different combinations in different concentrations) against oral pathogens, and I got good activity against oral pathogens. Should I select these combinations with good antibacterial activity for my oral care gel formulation?
For Example.
compound A + compound B + compound C = 1ug/ml + 2ug/ml + 1ug/ml
The above combination gives a good antibacterial effect.
Can I consider this combination (with respective concentrations) for my oral care gel formulation?
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I have prepared the silver nanoparticles via chemical reduction method using NaBH4. Upon turning yellow color of the solution I stopped the reaction. I got UV vis peak of nanoparticle solution at 400 nm.
But when I centrifuged the solution the pellet is so small that unable to use it for antibacterial activity. I want to ask whether I can use the AgNPs solution for MIC by diluting it with D.W. or pellet is necessary?
Also which medium will be suitable for the growth curve? either nutrient broth or PBS?
I will be grateful for your help.
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Dear Researcher,
Use high concentrations of primary materials to have finally enough concentrations of Ag NPs and on the other hand, apply ultra-centrifuge for precipitation of Ag NPs.
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Antibacterial activity was performed against gram positive and gram negative bacteria using 0.05M HCl as control. in gram positive bacteria control has not shown any significant activity whereas it has shown slight activity against gram negative bacteria . Pls suggest me how can i Calculate the % of inhibition in this case
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It is not the usual practice to report % inhibition of growth of rapidly-growing bacteria. The usual practice is to report the minimal inhibitory concentration (MIC) of the substance. The reason for this is that it is usually easy to tell in a set of 2-fold serial dilutions of the inhibitor which was the lowest concentration that prevented growth.
In contrast, if you try to make a plot of growth (either by colony forming units or optical density) versus concentration, it will usually show a very steep transition from full growth to no growth within one or two dilutions, making it difficult to calculate the 50% inhibition concentration (IC50) accurately.
So, since you have already measured the MIC, the measurement is complete.