Minimum Inhibitory Concentration Research Articles

The antimicrobial effectiveness of Rosmarinus officinalis, Lavandula angustifolia, and Salvia officinalis essential oils against Klebsiella pneumoniae and Pseudomonas aeruginosa in vitro and in silico

This study aimed to explore the phytochemical analyses and antibacterial potential of three essential oils (EOs) using both in-vitro and in-silico experiments for drug discovery. The Eos of Rosmarinus officinalis, Lavandula angustifolia, and Salvia officinalis were extracted by hydrodistillation, and GC–MS determined the chemical composition. The antibacterial activities of each EO were studied by the disc diffusion method. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of these EOs were determined by micro-dilution. In addition, the EOs were combined with ineffective antibiotics (Aztreonam et al.) against clinical bacteria (P. aeruginosa and K. pneumoniae) to determine this association's effect. The in-vitro toxicological study was based on the MTT cytotoxicity assay. Finally, in-silico methods were employed to estimate their possible antibacterial mechanisms. Molecular docking was performed to calculate the predictive binding affinities of five major volatile components to three proteins key in the bacterial cycle using the AutoDock Vina program; prediction of drug-likeness properties and Toxicity prediction were carried out respectively by SwissADME and ProToxII online server. The results showed that the three EOs possessed antibacterial activity against ATCC and clinical K. pneumoniae. We note that P. aeruginosa was resistant to lavender and sage EOs. Surprisingly, adding EOs to antibiotics ineffective against resistant bacteria showed a significant synergistic antibacterial effect. Cytotoxicity assay of essential oils showed different values ranging from 0.22 to 0.43 µL/mL. Finally, the molecular docking study revealed that both compounds (1,8-Cineol, 1-Dodecene, Linalool, cis-Thujone, and Camphor) from the three EOs have a significant potential to inhibit the protein target involved in bacteria resistance. Furthermore, the SwissADME prediction results showed that all five components satisfy the rule of five and exhibit acceptable drug-like characteristics. findings suggest that the three EOs have interesting antibacterial activity. The in-vitro and in-silico studies gave a great potentiation and may constitute a promising option to control the emergence of MDR P. aeruginosa and K. pneumoniae.

The bacteriostatic effect of a new controlled-release carotenoids-silver nanoparticle

Discuss the bacteriostatic effect of a novel controlled release silver nanoparticles carotenoids-silver nanoparticle. Detect the optimal extraction conditions for carotenoids through material liquid ratio, different ultrasonic temperatures and times; Detect the optimal synthesis conditions of carotenoids-silver nanoparticle through different volume ratios, UV irradiation times, and temperatures; Detect the bacteriostatic effects on Escherichia coli and Staphylococcus albus using the minimum inhibitory concentration (MIC) and Oxford cup agar plate diffusion method. The experiment proved that the best extraction effect of carotenoids was achieved when the volume ratio of orange peel powder to ethanol was 1:25, the ultrasound time was 40 min, and the temperature was 50 °C; When the amount of carotenoid extract added is 12 mL, the concentration of silver nitrate is 8 mmol/l, the UV irradiation time is 40 min, and the ultrasound temperature is 60 °C, the synthesized carotenoids-silver nanoparticle has the highest absorbance value; carotenoids-silver nanoparticle have strong inhibitory effects on the growth of both Escherichia coli and Staphylococcus albus. As the concentration increases, the bacteriostatic effect also becomes stronger, especially the strongest inhibitory effect on Staphylococcus albus. It was shown that carotenoids-silver nanoparticle has significant bacteriostatic effects, providing new ideas for the development of bacteriostatic agents in plant resources.

Optimal Extraction Technique and Antibacterial Properties of Essential Oil Through Magnolia sieboldii K. Koch Leaves

To provide scientific support for the exploration and application of the essential oil derived through leaves of Magnolia sieboldii K. Koch, this paper explores extraction technology optimization, composition analysis, and antibacterial properties for the essential oil derived through Magnolia sieboldii K. Koch leaves. Essential oil derived through Magnolia sieboldii K. Koch leaves was extracted by adopting hydrodistillation. With single-factor test and reaction surface improvement methods, the extraction technology of essential oil derived through Magnolia sieboldii K. Koch leaves was optimized. The structure of chemicals has been explored through the use of gas chromatographmass spectrometer (GC-MS) technology. By conducting Kirby-Bauer test and applying spread plate method, the antibacterial properties for essential oil has been measured. The liquid-solid ratio was 7.15 mL/g, the dilution period was 4.00 h, and the NaCl mass percentage was 2.26% as a consequence of the response surface optimization. The rate about gathered essential oil under such circumstances was 0.31537%. By performing chemical composition analysis, 43 compounds were measured from essential oil. Thel oil was sensitive to Staphylococcus aureus, Bacillus subtilis, and Escherichia coli with inhibitory area diameters of 17.27, 10.85, and 9.56 mm, respectively. The minimum inhibitory concentration (MIC) values for the three bacteria strains were 2.5 × 10–6, 5 × 10–6, and 10 × 10–6 g/mL, respectively. The optimum extraction rate of essential oil derived through leaves of Magnolia sieboldii K. Koch by hydro distillation is 0.35%, with the cancer-fighting substance β-elemene reaching up to a maximum of 42.53%. Simultaneously, the essential oil derived through leaves of Magnolia sieboldii K. Koch exhibits notable antibacterial effect and large development potential, suggesting the comprehensive development and utilization.

Lemon essential oil nanoemulsions: Potential natural inhibitors against Escherichia coli

Lemon essential oil (LEO) is a common natural antibacterial substance, and encapsulating LEO into nanoemulsions (NEs) can improve their stability and broaden its application. Our study aimed to investigate the bacterial inhibitory effect of LEO-NEs against Escherichia coli (E. coli). Results showed that the minimum inhibitory concentration (MIC) of LEO-NEs was 6.25 mg/mL, and the time-kill curve showed that E. coli were significantly killed by LEO-NEs after 5 h of treatment at 1MIC. Flow-cytometry analysis showed that LEO-NEs adversely affected the cell-membrane depolarisation, cell-membrane integrity, and efflux pump function of E. coli. Confocal laser scanning microscopy demonstrated that 8MIC of LEO-NEs induced changes in the cell-membrane permeability and cell-wall integrity of E. coli. Proteomic results suggested that the mode of action LEO-NEs against E. coli was to enhance bacterial chemotaxis and significantly inhibit ribosomal assembly. They may also affect butyric acid, ascorbic acid and aldehyde metabolism, and sulphur-relay system pathways. In conclusion, LEO-NEs had potential application as a natural antibacterial agent for the control of E. coli in the food industry.

Synthesis and Biological Evaluation of Novel Oxazolidinone Derivatives Containing Dithiocarbamate Moiety as Antibacterial Agents

Background: In this article, a series of novel oxazolidinone derivatives containing dithiocarbamate moieties have been designed and synthesized. Methods: Their antibacterial activities were measured against Staphylococcus aureus, vancomycin-resistant Enterococcus faecium (VREF), linezolid-resistant Enterococcus faecalis (LREF) and Streptococcus agalactiae (GBS) by minimal inhibitory concentration (MIC) assays. Results: Dithiocarbamates were found conducive to the maintenance of antibacterial activity. Most of them exhibited potent activity against Gram-positive pathogens comparable to linezolid. The most promising compound A8 showed remarkable antibacterial activity against S.aureus, VREF, LREF, and GBS pathogens with MIC values between 0.25 and 1 μg/mL, which might be a promising drug candidate for further investigation. Conclusion: A series of novel oxazolidinone derivatives containing dithiocarbamate moieties might be promising drug candidates for further investigation.

Chemical Characterization and Evaluation of the Antimicrobial Activity of Extracts from Two Cultivars of Cannabis sativa L. (Tisza and Kompolti) Grown in Sardinia

The present work was aimed at the chemical characterization and antimicrobial activity of some extracts of aerial parts (essential oils from leaves and inflorescences and resins from inflorescences) of two legal hemp (Cannabis sativa) varieties, Tisza and Kompolti, grown in Sardinia. Chemical characterization was carried out by gas chromatography (GC) and gas chromatography–mass spectrometry (GC-MS) techniques. The main constituent was myrcene (11.75% in Tisza and 18.21% in Kompolti); delta-9-tetrahydrocannabinol (THC) was not found, while cannabidiol was present up to 0.36% in Tisza and up to 2.80% in Kompolti. The antimicrobial activity of these extracts against a panel of microorganisms was also determined via minimum inhibitory concentration (M.I.C.) determination. While the results showed minor or negligible antimicrobial activity of the extracts against the Gram+ and Candida strains (M.I.C. values equal to or greater than 4 mg/mL), good antibacterial activity (especially of resins) was recorded against S. aureus (M.I.C. 0.015–0.031 mg/mL); no substantial differences were detected between the chemical compositions of the two Cannabis varieties.

The Phytochemical Composition and Antibacterial Effects of Allium sativum Clove Extracts on Some Enteric Bacterial Pathogens

In this study, the phytochemicals present in the cloves of Allium sativum were determined, and their antibacterial activities against some enteric bacterial pathogens were assessed. The phytochemical constituents were determined after the extraction process was completed using water and ethanol as the solvents. Furthermore, the aqueous and ethanolic extracts of A. sativum were tested against Escherichia coli, Salmonella typhi and Shigella dysenteriae isolated from faeces of gastroenteritis patients. The agar diffusion technique (punch method) was used for this. Additionally, the extracts' minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined. The mean values of the zones of inhibition obtained were statistically analyzed using ANOVA. The least significant difference was determined according to the LSD test at P<0.05. The results of the phytochemical analysis revealed the presence of saponin, alkaloids, flavonoids, and tannins. Furthermore, the antibacterial susceptibility test showed that the aqueous and ethanolic extracts possess antibacterial properties against all the test organisms. The ethanolic extract at the concentration of 500mg/ml had zones of inhibition of 29.00b against E. coli, 24.00b against S. dysenteriae and the lowest 20.00b against S. typhi. On the other hand, at that same concentration, the aqueous extract had zones of inhibition of 20.00b against E. coli and 18.00b against S. dysenteriae and S. typhi. This study suggests that A. sativum extracts possess antibacterial properties. Furthermore, since the ethanolic extract was more effective than the aqueous extract, it could be that the antibacterial potency of A. sativum is solvent-dependent. In conclusion, the findings from this study suggest that further purification of the constituents of the plant might lead to the development of novel antibiotics.

Green synthesis, characterization and applications of Phyllanthus emblica fruit extract mediated chromium oxide nanoparticles.

The green synthesis of metallic nanoparticles is attributable towards diverse applications in various fields, recently. In this research, we report simple and eco-friendly synthesis of chromium oxide (Cr2O3) nanoparticles using the fruit extract of Phyllanthus emblica as a reducing and capping agent. The absorbance peaks at 350nm and 450nm validated the nanoparticle formation in UV-visible spectrum. FTIR spectrum revealed the nature of functional groups. The crystalline properties of nanoparticles were ascertained by XRD analysis. EDX spectrum corroborated the elemental composition of nanoparticles in which chromium and oxygen constituted 68% of total weight. SEM images demonstrated agglomeration of nanoparticles resulting in the formation of large irregularly shaped flakes. Cr2O3 nanoparticles demonstrated excellent antimicrobial properties against 11 bacterial isolates and 1 fungal isolate. The largest inhibition zone (53mm) was measured against A. baumannii while the smallest inhibition zone (26mm) was recorded against S. aureus. Minimum inhibitory concentration (MIC) values were < 1µg/ml for all microbes. However, the synthesized nanoparticles did not reveal synergism with any of the selected antibiotics (FICI values > 1). Nanoparticles possessed potent anti-biofilm powers with maximum (77%) inhibition of E. coli biofilms and minimum (45%) inhibition of S. enterica biofilms. Photocatalytic activity of Cr2O3 nanoparticles was evaluated to determine their efficacy in environmental bioremediation. Outcomes demonstrated degradation of methyl red (84%) but not of methylene blue dye. Furthermore, the Cr2O3 nanoparticles displayed considerable antioxidant (43%) as well as anti-inflammatory (44%) potentials. Hence, the present study accounts for the versatile applications of P. emblica-mediated Cr2O3 nanoparticles which could be pursued for future biomedical and environmental applications.

Profiling Key Aroma Compounds of Senecio glaucus L. and their Antimicrobial and Antioxidant Activities: Multiplex of GC-MS, NMR and In Silico Studies.

The essential oils of Senecio plants have been used to treat a wide range of ailments. The current study aimed to extract the essential oil of Senecio glaucus obtained from Egypt's Nile delta and determine its chemical profile using GC-MS and NMR analysis. Then, the antimicrobial activity of the oil has been investigated against different fungal and bacterial strains. In addition, its activity as radical scavenger has been evaluated using DPPH, ABTS, and metal chelating techniques. The results revealed the identification of 50 compounds representing 98.80 % of the oil total mass. Sesquiterpenes, including dehydrofukinone (27.15 %) and 4,5-di-epi-aristolochene (10.27 %), as well as monoterpenes, including p-cymene (4.77 %), represented the most predominant constituents. The dehydrofukinone has been isolated and structurally confirmed using 1D and 2D NMR techniques. The oil has showed remarkable antifungal activity against Candida glabrata and C. albicans where the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values were 3.13 μg/mL and 1.50 μg/mL and 12.50 μg/mL and 6.30 μg/mL, respectively that could be attributed to the sesquiterpene ketones present in the aerial tissues of the plant. Also, this oil inhibited the growth of the tested bacteria with MIC ranging from 12.50-100.00 μg/mL. In comparison to ascorbic acid and Trolox, the EO had remarkable scavenging activity of DPPH, ABTS and metal chelating with IC50 values of 313.17±13.4, 493.83±20.1, and 409.13±16.7 μg/mL. The docking studies of the identified compounds of the oil to different microbial targets, including Gyrase B and α-sterol demethylase, showed that the phytol possessed the best binding affinities toward the active sites of both enzymes with ΔG=-7.42 and -7.78 kcal/mol, respectively. In addition, the phytol revealed the highest binding affinity to tyrosine kinase Hck with ΔG=-7.44 kcal/mol.

Durlobactam, a Diazabicyclooctane β-Lactamase Inhibitor, Inhibits BlaC and Peptidoglycan Transpeptidases of Mycobacterium tuberculosis.

Peptidoglycan synthesis is an underutilized drug target in Mycobacterium tuberculosis (Mtb). Diazabicyclooctanes (DBOs) are a class of broad-spectrum β-lactamase inhibitors that also inhibit certain peptidoglycan transpeptidases that are important in mycobacterial cell wall synthesis. We evaluated the DBO durlobactam as an inhibitor of BlaC, the Mtb β-lactamase, and multiple Mtb peptidoglycan transpeptidases (PonA1, LdtMt1, LdtMt2, LdtMt3, and LdtMt5). Timed electrospray ionization mass spectrometry (ESI-MS) captured acyl-enzyme complexes with BlaC and all transpeptidases except LdtMt5. Inhibition kinetics demonstrated durlobactam was a potent and efficient DBO inhibitor of BlaC (KIapp 9.2 ± 0.9 μM, k2/K 5600 ± 560 M-1 s-1) and similar to clavulanate (KIapp 3.3 ± 0.6 μM, k2/K 8400 ± 840 M-1 s-1); however, durlobactam had a lower turnover number (tn = kcat/kinact) than clavulanate (1 and 8, respectively). KIapp values with durlobactam and clavulanate were similar for peptidoglycan transpeptidases, but ESI-MS captured durlobactam complexes at more time points. Molecular docking and simulation demonstrated several productive interactions of durlobactam in the active sites of BlaC, PonA1, and LdtMt2. Antibiotic susceptibility testing was conducted on 11 Mtb isolates with amoxicillin, ceftriaxone, meropenem, imipenem, clavulanate, and durlobactam. Durlobactam had a minimum inhibitory concentration (MIC) range of 0.5-16 μg/mL, similar to the ranges for meropenem (1-32 μg/mL) and imipenem (0.5-64 μg/mL). In β-lactam + durlobactam combinations (1:1 mass/volume), MICs were lowered 4- to 64-fold for all isolates except one with meropenem-durlobactam. This work supports further exploration of novel β-lactamase inhibitors that target BlaC and Mtb peptidoglycan transpeptidases.

Antibacterial, antibiofilm, and antivirulence potential of the main diterpenes from Copaifera spp. oleoresins against multidrug-resistant bacteria.

To evaluate the antibacterial, antibiofilm and antivirulence potential of the main diterpenes from Copaifera spp. oleoresins against multidrug-resistant (MDR) bacteria. Antimicrobial assays included determination of the Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Minimum Inhibitory Concentration of Biofilm (MICB50), as well as synergistic and antivirulence assays for eight diterpenes against MDR. The tests revealed that two diterpenes (named 1 and 5) showed the best results, with MIC and MBC between 12.5 and 50μg/mL against most MDR bacteria. These diterpenes exhibited promising MICB50 in concentration between 3.12-25μg/mL but showed no synergistic antimicrobial activity. In the assessment of antivirulence activity, diterpenes 1 and 5 inhibited only one of the virulence factors evaluated (Dnase) produced by some strains of S. aureus at subinhibitory concentration (6.25μg/mL). Results obtained indicated that diterpenes isolated from Copaifera oleoresin plays an important part in the search of new antibacterial and antibiofilm agents that can act against MDR bacteria.

Antibacterial and antibiofilm activities of diclofenac against levofloxacin-resistant Stenotrophomonas maltophilia isolates; emphasizing repurposing of diclofenac

Background and Objectives: Stenotrophomonas maltophilia is an opportunistic pathogen causing nosocomial infections. Diclofenac is an anti-inflammatory drug that is considered a non-antibiotic drug. This study assessed the antibacterial and antibiofilm effects of diclofenac and levofloxacin/diclofenac combination against levofloxacin resistant isolates.&#x0D; Materials and Methods: Minimum inhibitory concentration was determined using broth microdilution method for levo- floxacin, diclofenac, and levofloxacin/diclofenac combination. Biofilm forming capacity and biofilm inhibition assay were determined. Relative gene expression was measured for efflux pump genes; smeB, and smeF genes and biofilm related genes rmlA, spgM, and rpfF without and with diclofenac and the combination.&#x0D; Results: Diclofenac demonstrated MIC of 1 mg/ml. The combination-with ½ MIC diclofenac- showed synergism where levofloxacin MIC undergone 16-32 fold decrease. All the isolates that overexpressed smeB and smeF showed a significant decrease in gene expression in presence of diclofenac or the combination. The mean percentage inhibition of biofilm for- mation with diclofenac and the combination was 40.59% and 46.49%, respectively. This agreed with biofilm related genes expression investigations.&#x0D; Conclusion: Diclofenac showed an antibacterial effect against Stenotrophomonas maltophilia. The combination showed in-vitro synergism, significant reduction in biofilm formation and in the relative level of gene expression. Furthermore, it can potentiate the levofloxacin activity or revert its resistance.&#x0D;  

Small Peptide Conjugates of Benzothiazole‐2‐Carboxylic Acids Targeting DprE1 Against Tuberculosis

AbstractInhibitors of Decaprenylphosphoryl‐β‐D‐ribose 2′‐epimerase (DprE1) are being thoroughly explored as potential pharmacological entities for the development of new anti‐tubercular therapeutics. In this context, benzothiazole‐bearingcompounds have emerged as potential non‐covalent DprE1 inhibitors active against mycobacterium tuberculosis. In view of the promising anti‐tubercular activity of benzothiazole based non‐covalent DprE1 inhibitor TCA1; a series of thirty small peptide conjugates of benzothiazole‐2‐carboxylic acid has been synthesized and evaluated for their anti‐tubercular activity against the M.tb H37Ra strain by broth microdilution assay. Among the compounds tested, compounds methyl (6‐methoxybenzo[d]thiazole‐2 carbonyl)tryptophylalaninate and methyl (6‐methylbenzo[d]thiazole‐2‐carbonyl)tryptophylalaninate demonstrated potential anti‐tubercular activity with minimum inhibitory concentration (MIC) values of 4 and 8 μg/mL, respectively. These compounds were further identified to be mycobactericidal and are completely killing the microbes at 8‐16 μg/mL concentrations. Furthermore, the cytotoxicity study of most potent compound methyl (6‐methoxybenzo[d]thiazole‐2 carbonyl)tryptophylalaninate illustrated no significant toxicity to the human cell line HepG2. Moreover, synthesised compounds were subject to molecular docking, ADME studies and MM‐GBSA calculations. In silico studies suggest that these compounds show strong interactions with key amino acids in the binding pocket of DprE1 (PDBID: 4KW5) with the most active conjugates residing well (with docking scores of −08.49 and −7.902 kcal/mol).

Based on molecular docking and real-time PCR technology, the two-component system Bae SR was investigated on the mechanism of drug resistance in CRAB.

This study aimed to explore the role of the two-component system Bae SR in the mechanism of drug resistance in carbapenem-resistant A. baumannii (CRAB) using molecular docking and real-time polymerase chain reaction (PCR). The two-component system Bae SR of Acinetobacter baumannii was subjected to molecular docking with imipenem, meropenem, and levofloxacin. Antibacterial assays and fluorescence quantitative PCR were used to explore protein-ligand interactions and molecular biological resistance mechanisms related to CRAB. The analysis of the two-component system in A. baumannii revealed that imipenem exhibited the highest docking energy in Bae S at - 5.81kcal/mol, while the docking energy for meropenem was - 4.92kcal/mol. For Bae R, imipenem had a maximum docking energy of - 4.28kcal/mol, compared with - 4.60kcal/mol for meropenem. The highest binding energies for Bae S-levofloxacin and Bae R-levofloxacin were - 3.60 and - 3.65kcal/mol, respectively. All imipenem-resistant strains had minimum inhibitory concentration (MIC) values of 16µg/mL, whereas levofloxacin-resistant strains had MIC values of 8µg/mL. The time-sterilization curve showed a significant decrease in bacterial colony numbers at 2h under the action of 8µg/mL imipenem, indicating antibacterial effects. In contrast, levofloxacin did not exhibit any antibacterial activity. Fluorescence quantitative PCR results revealed significantly increased relative expression levels of bae S and bae R genes in the CRAB group, which were 2 and 1.5 times higher than those in the CSAB group, respectively, with statistically significant differences. Molecular docking in this study found that the combination of Bae SR and carbapenem antibiotics (imipenem, meropenem) exhibited stronger affinity and stability compared with levofloxacin. Moreover, the overexpression of the two-component system genes in carbapenem-resistant A. baumannii enhanced its resistance to carbapenem, providing theoretical and practical insights into carbapenem resistance in respiratory tract infections caused by A. baumannii.

Screening Studies of the Antimicrobial Activity of the Pyrimidine Compound 2,2-[6-Bromo-2,4-Dioxoquinazoline-1,3(2H)diyl]bis(N-Carbamimidoylacetamide)

The aim of this study was to screen the antimicrobial activity of a pyrimidine compound under the laboratory code VMA-21-01. Antimicrobial activity was studied in relation to: Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, Klebsiella pneumonia, and Proteus mirabilis. The antimicrobial activity of 2,2-[6-Bromo-2,4-dioxoquinazoline- 1,3(2H)diyl]bis(N-carbamimidoylacetamide) was carried out in vitro by serial dilution and determination of its minimum inhibitory concentration. The sensitivity of microorganisms to the test substance was determined in a meat-peptone broth (visual assessment), followed by reinoculation on meat-peptone agar and colony count. DMSO tubes were used as a control. A 4% gentamicin solution was used as a comparison drug. In an in vitro experiment, it was found that the pyrimidine compound 2,2-[6-Bromo-2,4-dioxyquinazoline-1,3(2H)diyl]bis(N-carbamimidoylacetamide) under the laboratory cipher VMA21-01 has bactericidal activity against K. pneumonia comparable to the comparison drug gentamicin, as well as bacteriostatic activity against S. aureus, S. pneumoniae, E. coli, and P. mirabilis. 

Molecular epidemiology and resistance mechanisms of tigecycline-non-susceptible Acinetobacter baumannii isolated from a tertiary care hospital in Chongqing, China.

We studied 34 isolates of Tigecycline-Non-Susceptible A. baumannii (TNAB) obtained from clinical specimens at a large tertiary care hospital in Chongqing, China. These 34 strains belonged to 8 different clones including ST195 (35.3%) and ST208 (17.7%). EBURST analysis found that these 8 ST types belonged to the Clonal Complex 92. Tigecycline resistance-associated genes adeR, adeS, adeL, adeN, rrf, rpsJ, and trm were detected in most strains. The expression level of the resistance-nodulation-cell division (RND) efflux pumps in TNAB strains was higher than the reference strain ATCC19606. 58.8% of strains had a decrease in the tigecycline minimum inhibitory concentration (MIC) after the addition of carbonyl cyanide 3-chlorophenylhydrazone (CCCP). The TNAB strains in our hospital have a high degree of affinity and antibiotic resistance. Regular surveillance should be conducted to prevent outbreaks of TNAB epidemics.

Increased susceptibility to azithromycin of Pseudomonas aeruginosa biofilms using RPMI 1640 testing media.

Azithromycin (AZM) is efficient for treatment of chronic Pseudomonas aeruginosa biofilm lung infections, despite of resistance in conventional susceptibility testing. It has been shown that planktonic P. aeruginosa are more susceptible to AZM when tested in RPMI 1640 medium. The aim of the study was to test the susceptibility to AZM of P. aeruginosa biofilms in LB vs RPMI 1640 media. We investigated the effect of AZM on planktonic and biofilms of (WT) P. aeruginosa (PAO1), the hypermutable (ΔmutS) and the antibiotic-resistant phenotype(ΔnfxB) mutants. The effect of AZM on young and mature biofilms was investigated in the modified Calgary Biofilm Device by estimation of the minimal biofilm inhibitory concentration (MBIC). The AZM MBIC90 in LB/RPMI1640 on young biofilms treated for 24 h was 16/4 μg/mL for PAO1, 32/8 μg/mL for ΔmutS, and 256/16 μg/mL for ΔnfxB, while in mature biofilms was 256/2 μg/mL for PAO1 and ΔmutS and 16/1 μg/mL for ΔnfxB. The effect of AZM was improved when the treatment was prolonged to 72 h, supporting the intracellular accumulation of AZM. An increased susceptibility of P. aeruginosa biofilms to AZM was observed in RPMI 1640 than in LB medium. Our results might improve susceptibility testing and dosing of AZM for treatment of biofilm infections.

Glucose-Binding Dioclea bicolor Lectin (DBL): Purification, Characterization, Structural Analysis, and Antibacterial Properties.

In this study, we purified a lectin isolated from the seeds of Dioclea bicolor (DBL) via affinity purification. Electrophoresis analysis revealed that DBL had three bands, α, β, and γ chains, with molecular masses of approximately 29, 14, and 12kDa, respectively. Gel filtration chromatography revealed that the native form of DBL had a molecular mass of approximately 100kDa, indicating that it is a tetramer. Interestingly, DBL-induced hemagglutination was inhibited by several glucosides, mannosides, ampicillin, and tetracycline with minimum inhibitory concentration (MIC) values of 1.56-50mM. Analysis of the complete amino acid sequence of DBL revealed the presence of 237 amino acids with high similarity to other Diocleinae lectins. Circular dichroism showed the prominent β-sheet secondary structure of DBL. Furthermore, DBL structure prediction revealed a Discrete Optimized Protein Energy (DOPE) score of -26,642.69141/Normalized DOPE score of -1.84041. The DBL monomer was found to consist a β-sandwich based on its 3D structure. Molecular docking showed the interactions between DBL and α-D-glucose, N-acetyl-D-glucosamine, α-D-mannose, α-methyl-D-mannoside, ampicillin, and tetracycline. In addition, DBL showed antimicrobial activity with an MIC of 125μg/mL and exerted synergistic effects in combination with ampicillin and tetracycline (fractional inhibitory concentration index ≤ 0.5). Additionally, DBL significantly inhibited biofilm formation and showed no toxicity in murine fibroblasts (p < 0.05). These results suggest that DBL exhibits antimicrobial activity and works synergistically with antibiotics.

Gentamicin Susceptibility and Comparison of Adhesion and Invasion of Caco-2 and HD11 Cell Lines by Salmonella enterica Serotypes

Foodborne Salmonella serovars are important facultative intracellular pathogens that cause gastroenteritis in humans. Four strains from three of the more predominant Salmonella serovars in poultry were studied: Typhimurium, Enteritidis, and Heidelberg. Gentamicin susceptibility was determined using an agar disc diffusion test and minimum inhibitory concentration (MIC) assays for S. Typhimurium ATCC 14028 and S. Heidelberg ARI-14. Both strains were susceptible to gentamicin in disc diffusion. The MIC of gentamicin was approximately 125 mg/ml for all strains tested. These strains’ adhesion and invasion abilities were determined with two different cell lines, a human intestinal epithelial cell line (Caco-2) as well as a chicken macrophage cell line (HD11). Attachment percentages for each Salmonella strain were greater than the strain’s ability to invade cells. Similar attachment percentages to Caco-2 cells were observed for S. Typhimurium and S. Heidelberg. Attachment percentages were lower in HD11 cells than in Caco-2 cells, although Salmonella exhibited higher apparent HD11 invasion, likely from HD11 phagocytosis. Salmonella Enteritidis showed lower rates of adhesion and invasion in HD11 cells compared to Salmonella Typhimurium. Developing a better understanding of Salmonella virulence mechanisms is critical to reducing Salmonella infections.

Influence of flavonoids from Sedum aizoon L. on mitochondrial function of Rhizopus nigricans in strawberry.

Rhizopus nigricans (R. nigricans), one of the fungi that grows the fastest, is frequently discovered in postharvest fruits, it's the main pathogen of strawberry root rot. Flavonoids in Sedum aizoon L. (FSAL) is a kind of green and safe natural substance extracted from Sedum aizoon L. which has antifungal activity. In this study, the minimum inhibitory concentration (MIC) of FSAL on R. nigricans and cell apoptosis tests were studied to explore the inhibitory effect of FSAL on R. nigricans. The effects of FSAL on mitochondria of R. nigricans were investigated through the changes of mitochondrial permeability transition pore(mPTP), mitochondrial membrane potential(MMP), Ca2+ content, H2O2 content, cytochrome c (Cyt c) content, the related enzyme activity and related genes of mitochondria. The results showed that the MIC of FSAL on R. nigricans was 1.800mg/mL, with the addition of FSAL (1.800mg/mL), the mPTP openness of R. nigricans increased and the MMP reduced. Resulting in an increase in Ca2+ content, accumulation of H2O2 content and decrease of Cyt c content, the activity of related enzymes was inhibited and related genes were up-regulated (VDAC1, ANT) or down-regulated (SDHA, NOX2). This suggests that FSAL may achieve the inhibitory effect of fungi by damaging mitochondria, thereby realizing the postharvest freshness preservation of strawberries. This lays the foundation for the development of a new plant-derived antimicrobial agent.