Minimum Bactericidal Concentration Research Articles

Ethanolic Cashew Leaf Extract Encapsulated in Tripolyphosphate–Chitosan Complexes: Characterization, Antimicrobial, and Antioxidant Activities

Ethanolic cashew leaf extract (ECL-E) is rich in phenolic compounds and shows remarkable antioxidative and antimicrobial activities. Encapsulation could stabilize ECL-E as the core. Tripolyphosphate (TPP)–chitosan (CS) nanoparticles were used to load ECL-E, and the resulting nanoparticles were characterized. The nanoparticles loaded with ECL-E at different levels showed differences in encapsulation efficiency (47.62–89.47%), mean particle diameters (47.30–314.60 nm), positive zeta potentials (40.37–44.24 mV), and polydispersity index values (0.20–0.56). According to scanning electron micrographs, the nanoparticles had a spherical or ellipsoidal shape, and a slight agglomeration was observed. The appropriate ratio of CS/ECL-E was 1:3, in which an EE of 89.47%, a particle size of 256.05 ± 7.70 nm, a zeta potential of 40.37 ± 0.66 mV, and a PDI of 0.22 ± 0.05 were obtained. The nanoparticles also exhibited high antioxidant activities, as assayed by DPPH and ABTS radical scavenging activities, ferric reducing ability power (FRAP), and oxygen radical absorbance capacity (ORAC). Low minimum inhibitory concentration and minimum bactericidal concentration were observed against Pseudomonas aeruginosa (9.38, 75.00 mg/mL) and Shewanella putrefaciens (4.69, 75.00 mg/mL). In addition, ECL-E loaded in nanoparticles could maintain its bioactivities under various light intensities (1000–4000 Lux) for 48 h. Some interactions among TPP, CS, and ECL-E took place, as confirmed by FTIR analysis. These nanoparticles had the increased storage stability and could be used for inactivating spoilage bacteria and retarding lipid oxidation in foods.

Phenotypic and genotypic determination of resistance to common disinfectants among strains of Acinetobacter baumannii producing and non-producing biofilm isolated from Iran

BackgroundNosocomial infections are a global problem in hospitals all around the world. It is considered a major health problem, especially in developing countries. The increase in the patient’s stay in hospitals has increased the mortality rate, and consequently, the costs drastically increase. The main purpose of using disinfectants in the hospital environment is to reduce the risk of nosocomial infections. Ethylene diamine tetra acetic acid (EDTA) causes lysis and increases susceptibility to antimicrobial agents in the planktonic form of bacteria. This substance affects the permeability of the outer membrane of bacteria. It also prevents the formation of biofilms by bacteria.Materials and methodsIn the current study, 120 isolates of Acinetobacter baumannii (A. baumannii) were confirmed by phenotypic and genotypic methods. Antibiogram was performed and then the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of isolates against 5% sodium hypochlorite, ethanol %70, sayasept-HP 2%, chlorhexidine 2%, dettol 4/8% were evaluated. In addition, the disinfectant effect was re-evaluated with the mixture of EDTA solution. All isolates were examined for biofilm presence by crystal violet staining method in triplicates and repeated three times for each strain. Also for all isolates detection of efflux pump genes (Qac-E, qacE-Δ1, SUG-E) by PCR technique was done.ResultsAntibiogram results of A. baumannii showed that 6.7% were Multi-drug-resistant (MDR), and 89.2% were Extensively drug-resistant (XDR) isolates. The highest effect of disinfectants was related to 5% sodium hypochlorite, and the least effect was 70% ethanol. EDTA increases the efficacy of selected disinfectants significantly. The highest prevalence of the efflux pump genes was related to SUG-E (95%) and Qac-E (91.7%), and, the qacE-Δ1 gene with 12.5%. The biofilm production rate was 91.3% among all isolates.ConclusionThe best and safest way to disinfect hospital floors and surfaces is to choose the right disinfectants, and learn how to use them properly. In this study, a mixture of disinfectants and EDTA had a significant effect on bactericidal activity. it was found that improper use of disinfectants, especially the use of sub-inhibitory dilutions, increases the resistance of bacteria to disinfectants.

Antimicrobial activity of compounds identified by artificial intelligence discovery engine targeting enzymes involved in Neisseria gonorrhoeae peptidoglycan metabolism

BackgroundNeisseria gonorrhoeae (Ng) causes the sexually transmitted disease gonorrhoea. There are no vaccines and infections are treated principally with antibiotics. However, gonococci rapidly develop resistance to every antibiotic class used and there is a need for developing new antimicrobial treatments. In this study we focused on two gonococcal enzymes as potential antimicrobial targets, namely the serine protease L,D-carboxypeptidase LdcA (NgO1274/NEIS1546) and the lytic transglycosylase LtgD (NgO0626/NEIS1212). To identify compounds that could interact with these enzymes as potential antimicrobials, we used the AtomNet virtual high-throughput screening technology. We then did a computational modelling study to examine the interactions of the most bioactive compounds with their target enzymes. The identified compounds were tested against gonococci to determine minimum inhibitory and bactericidal concentrations (MIC/MBC), specificity, and compound toxicity in vitro.ResultsAtomNet identified 74 compounds that could potentially interact with Ng-LdcA and 84 compounds that could potentially interact with Ng-LtgD. Through MIC and MBC assays, we selected the three best performing compounds for both enzymes. Compound 16 was the most active against Ng-LdcA, with a MIC50 value < 1.56 µM and MBC50/90 values between 0.195 and 0.39 µM. In general, the Ng-LdcA compounds showed higher activity than the compounds directed against Ng-LtgD, of which compound 45 had MIC50 values of 1.56–3.125 µM and MBC50/90 values between 3.125 and 6.25 µM. The compounds were specific for gonococci and did not kill other bacteria. They were also non-toxic for human conjunctival epithelial cells as judged by a resazurin assay. To support our biological data, in-depth computational modelling study detailed the interactions of the compounds with their target enzymes. Protein models were generated in silico and validated, the active binding sites and amino acids involved elucidated, and the interactions of the compounds interacting with the enzymes visualised through molecular docking and Molecular Dynamics Simulations for 50 ns and Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA).ConclusionsWe have identified bioactive compounds that appear to target the N. gonorrhoeae LdcA and LtgD enzymes. By using a reductionist approach involving biological and computational data, we propose that compound Ng-LdcA-16 and Ng-LtgD-45 are promising anti-gonococcal compounds for further development.

The Resistance of Bacillus Spores: Implications for the Strain-Specific Response to High-Performance Disinfectants.

Bacterial spores in materials and equipment pose significant biosecurity risks, making effective disinfection crucial. This study evaluated Ortho-phthalaldehyde (OPA) and a quaternary ammonia-glutaraldehyde solution (AG) for inactivating spores of Bacillus thuringiensis (BT), B. cereus (BC), and two strains of B. velezensis (BV1 and BV2). Spores of BV1 and BT were treated with 22.5mg/m3 OPA by dry fumigation or 1mg/mL AG by spray for 20min, according to the manufacturer's recommendation. As no sporicidal effect was observed, OPA was tested at 112.5mg/m3 for 40min, showing effectiveness for BT but not for BV1. Minimum bactericidal concentration (MBC) tests revealed higher MBC values for glutaraldehyde, prompting an overnight test with 112.5mg/m3 OPA by dry fumigation and 50mg/mL AG by spray, using formaldehyde as a control. AG reduced all Bacillus strains, but with limited sporicidal effect. OPA was sporicidal for BT and BV1 but not for BC and BV2, indicating a strain-dependent effect. Formaldehyde performed better overall but did not completely inactivate BV2 spores. Our findings suggest that OPA and AG have potential as formaldehyde replacements in wet disinfection procedures.

Antimicrobial activity evaluation of combinations of essential oils, thymol and R-limonene against food-borne pathogens and spoilage agents

The application of essential oils has been shown to be an effective and sustainable alternative against the multiplication of spoilage and pathogenic microorganisms in food. The aim of this work was to study the antimicrobial activity effect of Cerrado Rosemary (Baccharis dracunculifolia DC.), Pepper Rosemary (Lippia sidoides Cham.), Mandarin (Citrus nobilis Lour.), Mexican Lime (Citrus aurantifolia Swingle) essential oils, and the thymol and R-limonene compounds against strains of Penicillium expansum, Pichia kudriavzevii, Salmonella Thypimurium and Staphylococcus aureus. The essential oils were characterized in terms of their chemical composition, the Minimum Inhibitory Concentration, and Minimum Bactericidal and Fungicidal Concentration; using the microdilution method in 96-well plates. In addition, effects from mixtures of the essential oils, and the isolated compounds in sub-inhibitory concentrations were performed. The Pepper Rosemary essential oil and thymol, separately, showed the lowest Minimum Inhibitory Concentration values against all the microorganisms evaluated, with the lowest ranging from 0.03 to 1.25 mg. mL−1 for P. expansum and 0.31–1.25 mg. mL−1 for S. Thypimurium. Mandarin and Mexican lime, have an enhanced antimicrobial effect when used in mixture. The R-limonene compound showed a synergistic additive effect when combined with the essential oils, against S. aureus strains only. The application of thymol and Lippia was able to reduce growth by 3 log10 for S. aureus and S. Typhimurium in 24 h. Therefore, the Pepper Rosemary essential oil, applied freely or in combination with the thymol compound, has greater potential for use as an antifungal and bactericidal agent, against the microorganisms evaluated.

ANTI-BACTERIAL EFFECTIVENESS OF CHITOSAN OF PAPUYU FISH (Anabas testudineus) AGAINST BACTERIA Streptococcus mutans

Background: Streptococcus mutans is one of the main bacteria that cause dental caries by demineralized hard tissues of the teeth. People can use natural ingredients to reduce the number of Streptococcus mutans microorganisms, that is chitosan papuyu fish scales (Anabas testudineus). Purpose: The purpose is to analyze the antibacterial effectiveness of chitosan from papuyu fish scales (Anabas testudineus) against Streptococcus mutans bacteria based on the values of the MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration). Methods: This is an experimental study with posttest only with a control group design using 30 samples of chitosan papuyu fish scales (Anabas testudineus) grouped into 6 treatment groups and 5 samples repetitions. The treatment groups were chitosan papuyu fish scales (Anabas testudineus) with concentrations of 25%, 50%, 75%, and 100%, 0.2% chlorhexidine as a positive control, and aquades as a negative control. Calculation of absorbance using a UV-VIS Spectrophotometer Biobase BK-D560 for MIC and Streptococcus mutans bacterial colonies were visualized with a colony counter for MBC. Results: The results of the Kruskal Wallis test for MIC and MBC of papuyu fish chitosan concentrations of 25%, 50%, 75%, and 100% obtained significant results of p=0.00, which means p&lt;0, 05 and showed a significant difference between treatments. Conclusion: There are differences in the effectiveness of MIC and MBC chitosan of papuyu fish scales (Anabas testudineus) at concentrations of 25%, 50%, 75%, 100%, chlorhexidine gluconate 0.2% (positive control), and aquadest (negative control).

ANTIBACTERIAL ACTIVITY OF PAPUYU FISH SCALE CHITOSAN (Anabas testudineus) AGAINST Staphylococcus aureus

Backgrounds: Pulp disease due to caries can be treated through endodontic treatment, which aims to eliminate bacteria in the root canal so microorganisms cannot multiply. Staphylococcus aureus is a resistant microorganism causing root canal treatment failure. Chlorhexidine as a gold standard cannot remove biofilm and other organic debris. Utilization of nature, chitosan of papuyu fish scales (Anabas testudineus) has antibacterial properties that can be an alternative root canal irrigation material. Purpose: Analyze the antibacterial activity of chitosan of papuyu fish scales against Staphylococcus aureus based on the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). Methods: This research is a true experimental design with posttest only with control group design. The research groups were chitosan of Papuyu fish scales with concentrations of 25%, 50%, 75%, 100%, chlorhexidine gluconate 2% (positive control), and aquadest (negative control) with 6 repetitions. Results: The MIC value in the One-Way ANOVA test showed a significant difference (p&lt;0.05). Data analysis followed by Post Hoc Games-Howell test showed all treatment groups had significant differences between each other (p&lt;0.05). The MBC value in the Kruskal Wallis test shows that there is a significant difference (p&lt;0.05). Data analysis followed by MannWhitney test showed significant differences between each other (p&lt;0.05) except for the group of papuyu fish scale chitosan 25% concentration against papuyu fish scale chitosan 50% concentration, papuyu fish scale chitosan 100% concentration against chlorhexidine gluconate 2% (p&gt;0.05). Conclusion: There is a difference in the antibacterial activity of chitosan of Papuyu fish scales concentrations of 25%, 50%, 75%, 100%, chlorhexidine gluconate 2% (positive control) and aquadest (negative control) against Staphylococcus aureus bacteria.

EFFECT OF MORINGA (Moringa oleifera) LEAF EXTRACT ON IN VITRO INHIBITION OF Candida albicans BIOFILM

Background: Oral candidiasis is an opportunistic infection in the oral cavity. This infection is caused by the fungus Candida albicans. The most important virulent attribute of this fungus is its ability to form biofilms, which can adhere to mucosa, epithelial lining, organs, prostheses or dentures. The formed biofilm is resistant to antifungal drugs. Objectives: The purpose of this study was to determine the effect of Moringa (Moringa oleifera) leaf extract on the inhibition of Candida albicans biofilm formation in vitro. Methods: This type of research is experimental study using post tests with control group design. Fungus used in this study was Candida albicans ATCC 10231. Determination of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were conducted by microdilution method. Inhibition test of C. albicans biofilm formation was carried out using the polystyrene microplate assay method. Concentration of extracts used in this study were 12.5%, 6.25%, 3.13% and 1.57%. Inhibitory activity of biofilm was measured using a crystal violet (CV) assay. Results: The results showed that MIC of Moringa leaf extract against the fungus C. albicans was at a concentration of 6.25%. Moringa leaf extract starting at a concentration of 3.13% already has had ability to inhibit formation of C. albicans biofilm. Conclusion: It can be concluded that Moringa leaf extract can inhibit formation of Candida albicans biofilm, so it can be developed as an alternative herbal ingredient to prevent oral candidiasis.EFFECT OF MORINGA (Moringa oleifera) LEAF EXTRACT ON IN VITRO INHIBITION OF Candida albicans BIOFILM

Coaggregation dynamics in drinking water biofilms and implications for chlorine disinfection

Biofilms in drinking water (DW) systems persistently challenge traditional disinfection methods due to intricate microbial interactions, with coaggregation playing a crucial role in forming multispecies biofilms. This study examined the implications of coaggregation on tolerance towards sodium hypochlorite (NaOCl) disinfection. Dual-species biofilms were formed for seven days on polyvinyl chloride coupons, comprising a strain of the emerging pathogen Stenotrophomonas maltophilia and the coaggregating strain Delftia acidovorans 005P. For comparison, dual-species biofilms were also formed with a non-coaggregation strain (D. acidovorans 009P). The minimum bactericidal concentration (MBC) for each planktonic strain varied (D. acidovorans: 1mg/L, S. maltophilia: 1.5mg/L) below the safe DW treatment limits. However, high NaOCl doses (10×MBC and 100×MBC,) showed low efficacy against dual-species biofilms, indicating significant biofilm tolerance to disinfection. Membrane damage occurred at sub-MBC without culturability loss, underscoring biofilm resilience. The biofilm analysis revealed a complex interplay between the composition of extracellular polymeric substances and the architecture, which was influenced by the presence of the coaggregating strain. Overall, coaggregation significantly influenced biofilm formation and resilience, impacting NaOCl disinfection. These findings underscore the challenges of microbial interactions in biofilms, emphasizing the need for improved disinfection strategies to control biofilms in drinking water systems.

Psidium guajav-mediated zinc oxide nanoparticles as a multifunctional, microbicidal, antioxidant and antiproliferative agent against destructive pathogens.

Bio-inspired zinc oxide nanoparticles are gaining immense interest due to their safety, low cost, biocompatibility, and broad biological properties. In recent years, much research has been focused on plant-based nanoparticles, mainly for their eco-friendly, facile, and non-toxic character. Hence, the current study emphasized a bottom-up synthesis of zinc oxide nanoparticles (ZnO NPs) from Psidium guajava aqueous leaf extract and evaluation of its biological properties. The structural characteristic features of biosynthesized ZnO NPs were confirmed using various analytical methods, such as UV-Vis spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM). The synthesized ZnO NPs exhibited ahydrodynamic shape with an average particle size of 11.6-80.2nm. A significant antimicrobial efficiency with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 40 and 27µg/ml for Enterococcus faecalis, followed by 30 and 40µg/ml for Staphylococcus aureus, 20 and 30µg/ml for Staphylococcus mutans, 30µg/ml for Candida albicans was observed by ZnO NPs. Additionally, they showed significant breakdown of biofilms of Streptococcus mutans and Candida albicans indicating their future value in drug-resistance research. Furthermore, an excellent dose-dependent activity of antioxidant property was noticed with an IC50 of 9.89µg/ml. The antiproliferative potential of the ZnO NPs was indicated by the viability of MDA MB 231 cells, which showed adrastic decrease in response to increased concentrations of biosynthesized ZnO NPs. Thus, the present results open up vistas to explore their pharmaceutical potential for the development of targeted anticancer drugs in the future.

Silver Nanoparticles Synthesized from Water Extracts of Artemisia annua and Their Antibacterial Activity Against Aquatic Pathogens

AbstractSilver nanoparticles (AgNPs) by biological synthesis have many advantages. Among them, herbs attract wide attention due to their unique medicinal effects. In this paper, the water/alcohol/ether extracts of dried or fresh Artemisia annua were used as reducing agents and stabilizers to synthesize AgNPs. Water is a highly polar solvent that can effectively extract polar compounds such as phenolic profile, which possesses strong reducing properties and enables the reduction of Ag+ to AgNPs. The prepared AgNPs were characterized using ultraviolet–visible (UV–vis) absorption spectra, X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) spectroscopy, transmission electron microscopy (TEM), and zeta potential analysis. The AgNPs prepared from the water extracts of dried Artemisia annua have obvious bacteriostatic effects on six common aquatic pathogens and have a wide application prospect in aquaculture. The inhibition zone against Vibrio anguillarum is up to 16.88 mm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Vibrio anguillarum are 1.09 µg/mL and 2.17 µg/mL, respectively, which is lower than most published reports.

Antilisterial effect of alkyl polyglycosides biosurfactant and modes of action

Several outbreaks of Listeria monocytogenes originated mainly from contaminated contact surfaces. Thus, this study investigated the antilisterial effect of natural surfactants in terms of their use as a 2-in-1 sanitizing washer on a food contact surface and evaluated their modes of action. The antilisterial activity of alkyl polyglycosides (APGs), namely capryl glucoside (CA), coco glucoside (CG), and decyl glucoside (DG), was evaluated based on the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) using broth dilution assay. The results showed that CG had the strongest antilisterial activity. Therefore, CG was selected for further investigation. The time-kill assay showed a lethal effect of 0.5 % (w/w) CG by inactivating 4 Log reduction (99.99 %) of L. monocytogenes within 3 s. Furthermore, 1 % (w/w) CG with slight mechanical force in washing (by shaking) was efficient for sanitizing a stainless-steel coupon surface based on its ability to cause a total reduction of deposited L. monocytogenes (99.9 %) within 10 min. Scanning electron microscopy and applying Fourier-transform infrared spectroscopy revealed that CG chemically disrupted the cell wall and plasma membrane of L. monocytogenes within 5 min after a gentle wash. The results showed it had potent antimicrobial activity and was bactericidal against L. monocytogenes. Overall, our results supported the use of CG as a natural antibacterial surfactant to alter the chemical sanitizer and the possibility of its practical use in the food industry and for household use.

Comparison of Dracocephalum Moldavica Essential Oil with Chlorhexidine on Cariogenic Bacteria.

Dental caries and periodontal disease are the most common oral problems. Chemical antibacterial agents often have side effects; thus, researchers have long been in search for organic and herbal products to prevent dental caries and periodontal disease. The present study has aimed to assess the effects of Dracocephalum moldavica essential oil on Streptococcus mutans, Streptococcus salivarius, Streptococcus sobrinus, and Lactobacillus acidophilus compared to Chlorhexidine (CHX). In this in vitro study, the plants were collected from Zanjan Province, Iran. Analysis of the essential oil was carried out by gas chromatography/mass chromatography. Micro-broth dilution and disc diffusion methods were used for assessment of the antimicrobial activity, and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were evaluated. The mean diameter of the growth inhibition zones in the well plate method for Dracocephalum moldavica showed that it had greater antimicrobial activity against Lactobacillus acidophilusthan others (p Value= 0.01). Furthermore, Dracocephalum moldavica had higher antimicrobial activity than CHX. The results of MIC and MBC showed that Dracocephalum moldavica had lower antibacterial activity than CHX. Dracocephalum moldavica essential oil demonstrated antibacterial properties against cariogenic bacteria. Given that other favorable properties of these essential oils are confirmed, they may be suitable for use as antibacterial agents in the formulation of oral healthcare products.

Exploring naphthoquinone and anthraquinone derivatives as antibiotic adjuvants against Staphylococcus aureus biofilms: Synergistic effects of menadione

Given the ability of Staphylococcus aureus to form biofilms and produce persister cells, making infections difficult to treat with antibiotics alone, there is a pressing need for an effective antibiotic adjuvant to address this public health threat. In this study, a series of quinone derivatives were evaluated for their antimicrobial and antibiofilm activities against methicillin-susceptible and methicillin-resistant S. aureus reference strains. Following analyses using broth microdilution, growth curve analysis, checkerboard assay, time-kill experiments, and confocal laser scanning microscopy, menadione was identified as a hit compound. Menadione exhibited a notable antibacterial profile (minimum inhibitory concentration, MIC = 4–16 μg/ml; minimum bactericidal concentration, MBC = 256 μg/ml) against planktonic S. aureus and its biofilms (minimum biofilm inhibitory concentration, MBIC50 = 0.0625–0.25 μg/ml). When combined with oxacillin, erythromycin, and vancomycin, menadione exhibited a synergistic or additive effect against planktonic cells and biofilms of two S. aureus reference strains and six clinical isolates, highlighting its potential as a suitable adjuvant for further development against S. aureus biofilm-associated infections.

Comparative Assessment of Antimicrobial Activity of Methanolic Extracts of Five Species of Astragalus (Fabaceae) Collected from Southeast of Iran, Kerman

Background: The antimicrobial properties of certain plants against five microorganisms have been investigated and compared. Objectives: In this research, we collected, dried, and identified five perennial (chamaephyte) species of Astragalus (Fabaceae) from a mountainous region (Takht-e-Sartashtak) with an average elevation of 3600 meters in southeastern Iran. The species include Astragalus cemerinus, Astragalus dactylocarpus, Astragalus glaucacanthus, Astragalus rhodosemius, and Astragalus siliquosus. Methods: The methanolic extracts of these plant species were tested to evaluate their antimicrobial activity against five pathogenic microorganisms, including one fungus (Candida albicans), two gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), and two gram-positive bacteria (Bacillus cereus and Staphylococcus aureus). The tests were conducted using Mueller Hinton Agar culture media and the agar-well diffusion method. Results: The antimicrobial activity of these five species was compared. It was found that the plant species displayed different antimicrobial activities. Astragalus glaucacanthus was active against four of the five microorganisms and was the only plant active against Escherichia coli. Astragalus siliquosus showed no activity against any of the microorganisms. Conclusions: Most of the antimicrobial activity was observed with Astragalus rhodosemius against Staphylococcus aureus. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC) of the plant extracts were almost similar.

Antimicrobial Activity of Diverse Chemotypes of Lippia graveolens Against Aeromonas hydrophila Isolated from Oreochromis niloticus

[Objective] This study aimed to evaluate the antimicrobial efficacy of essential oil (EO) from diverse chemotypes of Lippia graveolens against oxytetracycline-resistant Aeromonas hydrophila, which primarily affects the tilapia aquaculture (O. niloticus) in Guatemala. [Methodology] L. graveolens were collected in three departments in Guatemala. The EO was obtained by hydrodistillation and characterized using gas chromatography and mass spectrometry (GC/MS). Subsequently, an antimicrobial assay was conducted using disk and dilution susceptibility tests and evaluation of synergistic interactions among the chemotypes. Each test was performed in triplicate. [Results] The analysis revealed the presence of twenty-seven compounds in the EO obtained from the chemotypes, with the main class being monoterpenes. The major constituents identified were cis-Dihydro-β-terpineol (8.84%) in chemotype I, carvacrol (51.82%) in chemotype II, and thymol (79.62%) in chemotype III. All EO chemotypes of L. graveolens demonstrated the ability to inhibit the A. hydrophila growth. Thymol chemotype exhibited the strongest inhibitory effect against bacterial growth, with a minimum inhibitory concentration (MIC) of 92.4 µg/mL and a minimum bactericidal concentration (MBC) of 184.8 µg/mL. Furthermore, the results suggest that there is no synergistic or additive effect when combining different chemotypes of L. graveolens. [Conclusions] This is the first report of L. graveolens chemotypes exhibiting antimicrobial activity against oxytetracycline-resistant A. hydrophila. The findings suggest that the chemotype thymol could be a potential treatment for infections in the tilapia aquaculture in Guatemala.

Enhanced Antibacterial Activity of Manuka Honey with Higher Methylglyoxal Concentration Against Staphylococcus Aureus: in vitro study

Objective This study aimed to investigate the antibacterial activity of two types of Manuka honey with varying concentrations of methylglyoxal (MGO), 70 mg/kg and 1050 mg/kg, against S. aureus in vitro. Methods Two types of Manuka honey were tested for their antimicrobial activities. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined using the broth tube dilution method. Results Both concentrations of Manuka honey exhibited antibacterial activity against S. aureus, with the higher concentration (1050 mg/kg) showing enhanced antibacterial effects. The MIC was 100% v/v (undiluted) for the lower concentration and 50% v/v for the higher concentration. The MBC was inferred to be at a dilution of 50% v/v for the higher concentration, but not reached for the lower concentration at the dilution levels used. Conclusion The findings suggest that Manuka honey with a higher concentration of MGO may be more effective in inhibiting and potentially killing S. aureus. The study highlights the potential use of high-concentration Manuka honey as an alternative antimicrobial agent and calls for further investigation in clinical settings.

Assessing chemical composition and biological activity in Eucryphia cordifolia Cav. (Cunoniaceae): A study applying the ecological niche centrality hypothesis

Eucryphia cordifolia Cav. native to the forests of southern Chile, was used for medicinal purposes by the Mapuche people in ancient times. However, there are no recent studies on the biological properties of its leaves in their natural habitat. This study assessed how the location of E. cordifolia populations in their ecological niche (center or periphery) impacts the chemical composition, antioxidant activity, and antimicrobial properties of leaf extracts.Ultra-Liquid Chromatography with Diode Array Detector, coupled to Quadrupole-Time of Fly Mass Spectrometry was used to characterize the chemical composition of the extracts (UHPLC-DAD-QTOF). The antioxidant activity was assessed through DPPH, ABTS, and ORAC assays, and the total polyphenol content was determined using the Folin-Ciocalteu method. Antimicrobial activity was analyzed using methods such as agar diffusion, determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and biofilm formation assay. The leaves extract contained 28 identified compounds, including flavonols, flavones, flavanols, and other bioactive compounds. The peripheral population exhibited higher antioxidant values based on ABTS and ORAC methods in autumn and spring, and higher total polyphenol levels only in autumn. The E. cordifolia extracts significantly inhibited the growth of E. coli, S. aureus, and P. aeruginosa, with minimum bactericidal concentration values ranging between 1.2 and 5.3 mg/mL, lower than in other studies. Additionally, the peripheral population displayed greater inhibition of C. glabrata biofilm formation compared to the centroid and intermediate populations in both summer and autumn. In conclusion, this first comprehensive investigation of E. cordifolia reveals that its leaves are a valuable source of bioactive compounds with biotechnological potential.

Green synthesized silver nanoparticles from Ocimum sanctum: A potent inhibitor of biofilm forming ability and efflux pumps in bacteria causing bovine mastitis

Therapeutic management of mastitis faces significant challenges due to multidrug resistance. In the present study, multi-drug-resistant (MDR) Staphylococcus spp, Klebsiella pneumoniae, and Escherichia coli were isolated from bovine clinical mastitis cases and the phenotypic and genotypic multidrug resistance profiling was carried out. Silver nanoparticles (AgNPs) were biosynthesized using Ocimum sanctum leaf extracts and characterized via UV Vis absorption, Fourier Transform Infrared Spectroscopy, X-ray diffraction studies, Energy dispersive spectroscopy and Electron Microscopy. The determined minimum inhibitory concentration and minimum bactericidal concentration of the AgNPs against the recovered MDR isolates were 62.5 μg/ml and 125 μg/ml respectively. At a concentration of 50 μg/ml, the AgNPs demonstrated biofilm inhibitory activities of 80.35 % for MDR E. coli, 71.29 % for S. aureus and 60.18 % for MDR K. pneumoniae. Post-treatment observations revealed notable differences in biofilm formation across bacterial isolates. Furthermore, AgNP treatment led to significant downregulation of expression of the efflux pump genes acrB, acrE, acrF, and emrB in Gram-negative isolates and norB in Staphylococci isolates. This research underscores the potential for the development of an eco-friendly antimicrobial alternative in the form of green synthesized silver nanoparticles to combat drug resistance offering potential antibiofilm and efflux pump inhibitory activities.

Extraction, characterization and evaluation of antimicrobial activity of chitosan from adult Zophobas morio (Fabricius, 1776) (Coleoptera: Tenebrionidae)

The increasing demand for chitosan has led to the exploration of alternative sources, including insects. In this study, chitosan was extracted from Zophobas morio beetles with 19.17 % yield. FTIR and Raman Spectroscopy showed similar peaks in Z. morio chitosan (ZC) and commercial chitosan (CC). ZC showed low crystallinity (40.96 %) and high thermal residual mass (42.7 %) than CC. SEM imaging of ZC displayed pores ranging from 10 μm to 0.3 μm. EDX mapping revealed the homogenous presence of C, N and O elements. ZC exhibited low molecular weight (435.95 kDa) and low intrinsic viscosity (317.95 cm3/g) than CC (680.20 kDa and 480.87 cm3/g, respectively). Degree of deacetylation of ZC and CC was 96.24 % and 78.26 %, respectively. ZC showed antimicrobial activity against Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13883), Proteus mirabilis (ATCC 29906), Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 29212) and Candida albicans (ATCC 90028) with zones of inhibition ranging from 5 mm to 11 mm. The minimum bactericidal concentration of ZC against K. pneumoniae and P. mirabilis was lower than CC. This study suggests the applicability of insect chitosan as an antimicrobial agent in the food and pharmaceutical industries.