Polyethyleneimine‐Modified Piezoelectric Barium Titanate of Various Sizes Reveals Improved Antibacterial Properties

Bacteria have acquired resistance against almost all antibiotics because of the misuse of antibacterial agents and long periods of treatment. Antimicrobial peptides (AMPs) are one of the most encouraging candidates to solve this problem, as they possess high prokaryotic selectivity, and affect the bacteria by a unique mode of action. Novel cyclic undecapeptides (QNRNFYFNRNQ and QNRNFHFNRNQ) and their linear counterparts were investigated for their antibacterial activity against virulent strains. The minimal inhibitory concentration (MIC) values showed that tyrosine and histidine AMPs have promising antibacterial activity against virulent bacteria. The MIC values against the P. aeruginosa PA14, E. coli O157:H7 CR3, S. aureus 209P, and B. subtilis ATCC 6633 bacterial strains were evaluated for the cyclic peptide containing tyrosine, and their values were 6.25, 12.5, 12.5, and 12.5 µM, respectively. Meanwhile, for the linear form, they were 9.3, 12.5, 12.5, and 12.5 µM, respectively. The cyclic-peptide–containing histidines’ MIC values were 6.25, 3.1, 6.25, and 3.1 µM, respectively. Meanwhile, for the linear form, they were 3.1, 3.1, 3.1, and 6.25 µM, respectively. The antibacterial activities of the new AMPs were compared with that of gentamicin sulfate, and showed relatively higher potencies. Time-inhibition studies demonstrated the rapid antibacterial effects of the novel AMPs, which were more likely to be concentration-dependent, rather than time-dependent. At double the MIC concentration, all of the tested peptides exhibited relatively stable antibacterial effects up to 24 h, especially the peptides containing tyrosine, which showed an improved antibacterial effect.

1281. An Evaluation of Tebipenem In Vitro Activity Against a Panel of Pseudomonas aeruginosa Isolates with Efflux, AmpC, and OprD Mutations

Essential oils (EOs) from Citrus are not only economic, eco-friendly and natural alternatives to chemical preservatives but also have other biological applications. This study aimed to investigate the chemical composition of Citrus species (EOs from C. limonia, C. latifolia, C. sinensis and C. deliciosa fruit peel) to evaluate their in vitro antibacterial activity against Listeria monocytogenes, Yersinia enterocolitica, Staphylococcus aureus, Clostridium botulinum and Bacillus cereus. The chemotaxis model, which was used for evaluating their anti-inflammatory activity, showed that EOs exhibited effective results when the dose was 100 µg/mL. Regarding all antimicrobial activities, minimum inhibitory concentration (MIC) values of EOs were calculated by the broth microdilution method on 96-well microplates. EOs showed satisfactory antifungal activity against Malassezia furfur (MIC values between 32.5 and 62.5 µg/mL). Citrus deliciosa, whose MIC = 95.8 µg/mL, inhibited acetylcholinesterase (AChE) more selectively. All EOs from Citrus spp. fruit peel showed good antibacterial activity against Yersinia enterocolitica (MIC = 62.5 µg/mL) and Staphylococcus aureus (MIC = 62.5 µg/mL), mainly the EO from C. deliciosa whose MIC values were 50 µg/mL for both. EOs were moderately active against Clostridium botulinum, Bacillus cereus and Listeria monocytogenes since MIC values ranged from 100 μg/mL to 400 μg/mL. Both GC-FID and GC-MS analyses revealed that the single major constituent determined in EOs is the terpene limonene. EOs from Citrus may be important active ingredients of several products to prevent bacterial growth in food, to attack the fungus that causes seborrheic dermatitis and to treat inflammatory processes. In short, the promising antiacetylcholinesterase activity of EOs under evaluation was attributed to the high concentration of the monoterpene limonene

N-Heterocyclic carbene (NHC) complexes are known to have antibacterial properties in solutions. However, these complexes have never been immobilized on solid supports to prepare antibacterial surfaces. Here, we tackled this lack and succeeded in immobilizing these NHC complexes on gold surfaces by electropolymerization. For this, we synthesized a series of various NHC complexes of different low-valent transition metals (M = Ag(I), Au(I), Rh(I), Ru(II), Cu(I)) bearing a pyrrole function at the five-membered carbenic cycle. We measured the antibacterial properties of these complexes against two Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and two Gram-positive bacteria (Staphylococcus aureus and Listeria innocua) by determining their minimum inhibitory concentration (MIC) values. All NHC complexes presented interesting antibacterial properties that are metal-dependent. The silver-NHC complex showed higher antibacterial activity against Gram-negative bacteria (MIC = 16 μg·mL-1) than against Gram-positive bacteria (MIC = 32 μg·mL-1) and was poorly efficient against L. innocua. All other metal-NHC complexes were more efficient against Gram-positive bacteria, with MIC values in the range 4-16 μg·mL-1. These NHC complexes were then electropolymerized on gold substrates using their pyrrole function. Efficient incorporation of these NHC species into polypyrrole (PPy) films was confirmed by X-ray photoelectron spectroscopy (XPS) measurements with metal contents ranging from 0.8% (Cu) to 12.3% (Ag). Scanning electron microscopy (SEM) and profilometry measurements ascertain that the homogeneity, structure, and thickness of the films depend on the metal. The antibacterial activities of the polypyrrole films were then determined by the halo inhibition method. A very good match between the antibacterial properties of the films and those of the monomers with Ag(I), Au(I), and Rh(I) complexes was found. For the other complexes, the metallic content was too low to obtain interesting antibacterial properties. The cytotoxicity of the films was finally evaluated on normal human dermal fibroblasts (NHDF). Our study reveals a strong impact of the doping anions of polypyrrole on cell viability.

Background: Artemisia indica is a traditionally used medicinal plant in the treatment of various conditions such as loss of appetite, abdominal discomfort, antimalarial infection, dermal wound infection, etc. Objectives: This study aims to determine the presence of phytochemical content, antioxidant, antibacterial, and antidandruff activity of leaf extract of A. indica . Materials and Methods: Dried ground leaves were subjected to a cold extraction method using an absolute concentration of methanol, ethanol, and water. Total phenolic, flavonoid, and proanthocyanidin content was estimated by using a linear regression equation from the calibration curve and expressed in terms of gallic acid equivalent (GAE) and rutin equivalent (RE). Antioxidant properties were determined using DPPH (1,1-diphenyl-2-picryl-hydrazyl), nitric oxide, and hydrogen peroxide assay, and their IC 50 values were calculated. The antibacterial activity was tested using the agar well diffusion method against the common five pathogenic strains, and the zone of inhibition is compared with gentamicin (1 mg/mL) as a positive control. The minimum inhibitory concentration (MIC) value was obtained by the microbroth dilution method. The antidandruff assay was performed on Malassezia furfur by the disk diffusion method into Sabouraud dextrose agar overlaid with 1 mL of olive oil, and the MIC value was determined by the microtiter plate method. Results: The result showed that the Artemisia methanolic extract represents ample content of phenolics (248±3.29 mg/g of GAE), flavonoids (222.33±4.41 mg/g of RE), and proanthocyanidin (222.83±1.62 mg/g of RE equivalent). The antioxidant assay revealed that methanolic extract has the highest radical scavenging activity followed by aqueous extract and then ethanolic extract. The antibacterial activity of leaf extract shows MIC value ranging from 6 to 25 μg/mL against various human pathogenic bacteria. The antidandruff assay showed that MIC value of methanolic extract is lesser than that of ethanolic extract (350<400) mg/mL. Conclusion: The results concluded that leaf extract of A. indica contains phenolics, flavonoids, and proanthocyanidin and exhibits adequate antibacterial, antidandruff, and antioxidant activity.

BackgroundAntibiotic resistances of pathogens and breast cancer warrant the search for new alternative strategies. Phytoextracts can eradicate microbe-borne diseases as well as cancer with lower side effects compared to conventional antibiotics.AimUnripe and ripe Azadirachta indica (neem) seed extracts were explored as potential antibiofilm and anticancer agents in combating multidrug-resistant infectious bacteria as well as anticancer agents against the MDR breast cancer cell lines.Methods Shed-dried neem seeds (both unripe and ripe) were pulverized and extracted using methanol. The chemical components were identified with FTIR and gas chromatography - mass spectrometry. Antibiofilm activity of neem seed extracts were assessed in terms of minimum biofilm inhibitory concentration (MBIC), minimum biofilm eradication concentration (MBEC), and fluorescence microscopic studies on Staphylococcus aureus and Vibrio cholerae. Bacterial cells were studied by fluorescence microscopy using acridine orange/ethidium bromide as the staining agents. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were evaluated to observe the antibacterial activities. Cytotoxicity of the extracts against human blood lymphocytes and the anticancer activity against drug-resistant breast cancer cell lines were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and fluorescence-activated cell sorting (FACS) studies.Results 4-Ethyl-2-hydroxy-2-cyclopentene-1-one, phthalic acid, and 2-hexyl-tetrahydro thiophane were the major compounds in unripe neem seed, whereas 3,5-dihydroxy-6-methyl-2,3-dihydro-4-H-pyran-4-one and 4-ethylbenzamide were predominant in ripe neem seed. Triazine derivatives were also common for both the extracts. MBIC values of unripe and ripe neem seed extracts for S. aureus are 75 and 100 µg/mL, respectively, and for V. cholerae, they are 100 and 300 µg/mL, respectively. MBEC values of unripe and ripe seed extracts are 500 and 300 µg/mL, respectively for S. aureus and for V. cholerae the values are 700 and 500 µg/mL, respectively. Fluorescence microscopic studies at 16 and 24 h, after bacterial culture, demonstrate enhanced antibiofilm activity for the ripe seed extract than that of the unripe seeds for both the bacteria. MTT assay reveals lower cytotoxicity of both the extracts towards normal blood lymphocytes, and anticancer activity against breast cancer cell line (MDA-MB-231) with superior activity of ripe seed extract. FACS studies further supported higher anticancer activity for ripe seed extract.ConclusionsMethanolic extract of neem seeds could substantially inhibit and eradicate biofilm along with their potent antibacterial and anticancer activities. Both the extracts showed higher antibiofilm and antibacterial activity against S. aureus (gram-positive) than V. cholerae (gram-negative). Moreover, ripe seed extract showed higher antibiofilm and anticancer activity than unripe extracts.Graphical

The in vitro assessment of diruthenium(II)-arene compounds against Escherichia coli, Streptococcus pneumoniae, and Staphylococcus aureus showed a significant antibacterial activity of some compounds against S. pneumoniae, with minimum inhibitory concentration (MIC) values ranging from 1.3 to 2.6 µM, and a medium activity against E. coli, with MIC of 25 µM. The nature of the substituents anchored on the bridging thiols and the compounds molecular weight appear to significantly influence the antibacterial activity. Fluorescence microscopy showed that these ruthenium compounds enter the bacteria and do not accumulate in the cell wall of gram-positive bacteria. These diruthenium(II)-arene compounds exhibit promising activity against S. aureus and S. pneumoniae and deserve to be considered for further studies, especially the compounds bearing larger benzo-fused lactam substituents.

Recent data show an emergence of resistance in the Bacteroides fragilis group against several antimicrobial agents and inducible resistance against metronidazole in nim-positive strains. The aim of the present study was to investigate inducible metronidazole resistance in nim-positive as well as in nim-negative B. fragilis group strains. Of 18 B. fragilis strains (including four nim-positive reference strains and one ATCC strain), two Bacteroides ovatus strains, and one Bacteroides thetaiotaomicron DSM strain minimum inhibitory concentration (MIC) values for metronidazole were determined by Etest and analyzed for nim genes (nimA to -G) by PCR. For this purpose bacterial suspensions were incubated on supplemented Columbia agar plates containing metronidazole at twice the MIC value of the specific strain and incubated under anaerobic conditions for 48 hours. After incubation, growing bacteria were harvested and thereafter incubated at four times the original MIC. This procedure was repeated with increasing antibiotic concentrations. The resulting MIC values were confirmed by Etest. The MIC values for metronidazole of the four nim-positive reference strains ranged from 3 to 8 mg/l. The B. fragilis ATCC 25285 strain and the B. thetaiotaomicron DSM 2255 strain were nim negative with MIC values of 0.19 mg/l and 0.75 mg/l, respectively. Three clinical isolates of B. fragilis strains showed MIC values of > 256 mg/l. In all three strains, nim genes were detected by PCR. The other clinical isolates were nim negative. In these strains, MIC values ranged from 0.19 to 0.75 mg/l. After several passages on metronidazole containing agar, all B. fragilis group strains exhibited MIC values of > 256 mg/l determined by Etest. Metronidazole resistance can be selected not only in nim-positive strains but also in nim-negative strains, suggesting that mechanisms other than nim genes are involved. These findings and the emerging resistance of the B. fragilis group against several antimicrobial agents underscore the importance of susceptibility testing of anaerobes even in routine laboratories.

In recent years many of researchers were studying antimicrobial and other chemical and biological characteristics of medicinal and nonmedicinal plants seeking for better drug alternatives for treatment of diseases. The antimicrobial activity of methanolic extracts of ripped and unripped figs was studied alone and in combination in vitro. Minimum inhibitory concentration (MIC) values were determined by broth microdilution on standard microorganisms. Two different lower concentrations of MIC were used for analysis of combinational antibacterial activities. Findings showed that ripped Fig extract in concentrations of ≥ 13 to ≥6.5 mg/ml have MIC values on tested bacteria, but unripped Fig extract showed a MIC value in ≥7 mg/ml against all of the studied bacteria. Sub MIC concentrations (1:4 and 1:4 MIC) of combination of ripped and unripped extracts indicated synergic and additive effects on bacteria, respectively. In this study ripped and unripped Fig extracts in selected concentrations(1:4 and 1:2 MICs) have indicate synergic and additive antibacterial activity on bacteria, in addition antibacterial activity of unripped Fig extract was higher than ripped Fig extract and was significant(p=0.002). Since Fig has been used from ancient eras by humans, this kind of extracts could be a potential candidate for combination therapy of infections. Key words: Ripped fig extract, unripped fig extract, synergy, additive, MIC.

Organotellurium compounds are being well researched as potential candidates for their functional roles in therapeutic and clinical biology. Here, we report the in vitro anticancer and antibacterial activities of an AS101 analog, cyclic zwitterionic organotellurolate (IV) compound 2 [Te-{CH2CH(NH3+)COO}(Cl)3]. Different concentrations of compound 2 were exposed to fibroblast L929 and breast cancer MCF-7 cell lines to study its effect on cell viability. The fibroblast cells with good viability confirmed the biocompatibility, and compound 2 also was less hemolytic on RBCs. A cytotoxic effect on MCF-7 breast cancer cell line investigated compound 2 to be anti-cancerous with IC50 value of 2.86 ± 0.02µg/mL. The apoptosis was confirmed through the cell cycle phase arrest of the organotellurolate (IV) compound 2. Examination of the antibacterial potency compound 2 was done based on the agar disk diffusion, minimum inhibitory concentration, and time-dependent assay for the Gram-positive Bacillus subtilis and Gram-negative Pseudomonas putida. For both bacterial strains, tests were performed with the concentration range of 3.9-500μg/mL, and the minimum inhibition concentration value was found to be 125μg/mL. The time-dependent assay suggested the bactericidal activity of organotellurolate (IV) compound, 2 against the bacterial strains.

We compared the values of the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) values ​​of three antimicrobial agents for 72 bovine isolates ofPasteurella multocida, 80 swine isolates ofP. multocida, 80 bovine isolates ofEscherichia coli, 80 swine isolates ofE. coli, and 80 isolates ofStaphylococcus aureusfrom bovine mastitis. The ratio of MIC90​​/MPC90which limited mutant selection window (MSW) was ≤ 0.12/4 mg/l for enrofloxacin, 0.5/≥ 64 mg/l for florfenicol and 4/≥ 128 mg/l for tulathromycin in bovineP. multocidaisolates, ≤ 0.12/2 mg/l for enrofloxacin, 0.5/≥ 64 mg/l for florfenicol and 4/≥ 128 mg/l for tulathromycin in swineP. multocidaisolates, 1/16 mg/l for enrofloxacin, 8/≥ 64 mg/l for florfenicol and 8/≥ 128 mg/l for tulathromycin in bovineE. coliisolates, 0.5/16 mg/l for enrofloxacin, ≥ 64/≥ 64 mg/l for florfenicol and 8/≥ 128 mg/l for tulathromycin in swineE. coliisolates, and 0.25/16 mg/l for enrofloxacin, 4/≥ 64 mg/l for florfenicol and 4/≥ 128 mg/l for tulathromycin inS. aureusisolates. These findings indicate that the dosage of antimicrobial agents to achieve serum concentration equal to or higher than MPC could reduce selection of resistant bacterial subpopulation.

BackgroundFosfomycin combination therapy is a potential approach for treatment of multidrug-resistant (MDR) PA infections despite a lack of approved susceptibility breakpoints for this organism. While DD testing is commonly used for fosfomycin, growth of discrete inner colonies (IC) within the zone of inhibition has been observed for multiple organisms following DD. Criteria recommended by CLSI and EUCAST are contradictory for interpreting these inner colonies. We therefore sought to determine the frequency of inner colonies and MIC differences between PA parent-inner colony pairs from an international isolate collection.MethodsA convenience collection of 198 clinical PA isolates from three U.S institutions (n = 82), two Australian institutions (n = 72), and the CDC & FDA Antibiotic Resistance Isolate Bank (n = 44) were included. Fosfomycin MIC values were determined in duplicate on separate days by DD and broth microdilution (BMD) testing. For parent isolates with discrete IC observed during DD, IC isolates were subcultured and MIC values were determined and then compared to their corresponding parent isolates. MIC values were interpreted using CLSI Escherichia coli (EC) breakpoints (susceptible: MIC ≤ 64 μg/mL, intermediate: MIC = 128, resistant: MIC ≥ 256 μg/mL).ResultsParent isolate BMD MIC values ranged from < 4 to > 256 μg/mL while IC isolate BMD MIC values ranged from 128 to > 1024 μg/mL. MIC50/90 values were 128/256 μg/mL and > 1024/ > 1024 μg/mL for the parent and IC isolates, respectively. A high frequency of 45% (89/198) of parent isolates displayed discrete IC which also demonstrated a higher frequency of resistance (97.8%) compared to the parent isolates (23.7%).ConclusionIC MIC values were higher overall compared to parent MIC values, with an average fold difference of ~18 between the parent-inner colony pairs. The frequency of IC found in this study (45%) is considerably higher than previously observed in EC clinical isolates. These data highlight the need to further investigate the importance of these IC and warrant caution for extrapolation of EC breakpoints for fosfomycin susceptibility testing against PA.DisclosuresAll Authors: No reported disclosures

&lt;p&gt;&lt;em&gt;Rhododendron&lt;/em&gt; has long been known to treat various diseases including diarrhea, but diversity and potency of its endophytic actinobacteria has not been studied. The objectives of this research were to explore the existence of endophytic actinobacteria from &lt;em&gt;Rododendron &lt;/em&gt;spp. and assesed their antibacterial activity, as an effort to control the growth of bacterial pathogen resistant to some antibiotics. The endophytes were isolated from &lt;em&gt;Rhododendron &lt;/em&gt;spp. using HV medium, and purified in ISP2 medium. The antibacterial activity was assayed against Enteropathogenic &lt;em&gt;Escerichia coli &lt;/em&gt;(EPEC) K1.1 resistant to ampicillin and &lt;em&gt;Bacillus pumilus&lt;/em&gt;. The Minimum Inhibitory Concentration (MIC) value, macroscopic and microscopic were examined. Twenty three of endophytic actinobacteria were successfully isolated from 7 &lt;em&gt;Rhododendron&lt;/em&gt; species. Two of them, i.e. RJkb1 and RJkb3 isolates, had high antibacterial activity, with 17.2 mm and 14.5 mm inhibition zone against EPEC K1-1, respectively; and 12.4 mm and 16.1 mm inhibition zone against &lt;em&gt;B&lt;/em&gt;.&lt;em&gt; pumilus&lt;/em&gt;, respectively. The highest antibacterial activity for both RJkb1 and RJkb3 isolates was achieved at day 15, at 28 &lt;sup&gt;o&lt;/sup&gt;C. At 250 µg/mL to 1750 µg/mL either RJkb1 or RJkb3 supernatant showed no activity against EPEC K1-1. The MIC value against &lt;em&gt;B. pumilus&lt;/em&gt;&lt;em&gt; &lt;/em&gt;was at 1250 µg/mL for both tested isolates. Under an electron microscope observation, cell morphology of the treated &lt;em&gt;B. pumilus&lt;/em&gt; showed elongated cells and viewer in cell number, compared with the untreated one. From this work, the existence of endophytic actinobacteria from &lt;em&gt;Rhododendron &lt;/em&gt;spp. and their antibacterial activity contribute to the understanding of their diversity and potency as antibacterial agent. &lt;/p&gt;

Background: Olive leaf and arugula seed crude extracts were tested for their in vitro antibacterial activities. Utilizing the disc diffusion technique, antibacterial activity against three microorganisms was assessed. Both the minimum bactericidal concentration (MBC) and the minimum inhibition concentration (MIC) have been established. The standard medication for the investigation of antibacterial activity was gallic acid. Materials and Methods: The antibacterial activity was selected against two Gram-positive bacteria, Bacillus cereus and Staphylococcus aureus; The extract’s antibacterial activity was determined using a diffusion test on Mueller-Hinton agar that had previously been injected with 1 mL of an 18-hour-old bacterial solution (106 CFU/mL). Results: With an average zone of inhibition of 3 to 8 mm, the methanol extract of olive leaves and arugula seeds demonstrated strong antibacterial activity. Staphylococcus aureus was the bacterium with the highest level of sensitivity. In comparison to olive leaf extract, the antibacterial activity of arugula seed extract was higher. For Staphylococcus aureus and Bacillus cereus, the minimum inhibition concentration (MIC) values of the olive leaves and arugula seeds extract were 80 and 40 g/ml, respectively, while the minimum bactericidal concentration (MBC) values for S. aureus and B. cereus, respectively, were 60 and 600 g/ml. Conclusion: These findings imply that arugula seeds and olive leaves have intriguing antimicrobial properties.

BackgroundSeveral herbs are traditionally used in the treatment of a variety of ailments particularly in the rural areas of South Africa where herbal medicine is mainly the source of health care system. Many of these herbs have not been assessed for safety or toxicity to tissue or organs of the mammalian recipients.MethodsThis study evaluated the cytotoxicity of some medicinal plants used, inter alia, in the treatment of diarrhoea, and stomach disorders. Six selected medicinal plants were assessed for their antibacterial activities against ampicillin-resistant and kanamycin-resistant strains of Escherichia coli by the broth micro-dilution methods. The cytotoxicities of methanol extracts and fractions of the six selected plants were determined using a modified tetrazolium-based colorimetric assay (3-(4, 5-dimethylthiazol)-2, 5-diphenyl tetrazolium bromide (MTT) assay).ResultsThe average minimum inhibitory concentration (MIC) values of the plants extracts ranged from 0.027 mg/mℓ to 2.5 mg/mℓ after 24 h of incubation. Eucomis autumnalis and Cyathula uncinulata had the most significant biological activity with the least MIC values. The in vitro cytotoxicity assay on human hepatocarcinoma cell line (Huh-7) revealed that the methanol extract of E. autumnalis had the strongest cytotoxicity with IC50 of 7.8 μg/mℓ. Ethyl acetate and butanol fractions of C. uncinulata, Hypoxis latifolia, E. autumnalis and Lantana camara had lower cytotoxic effects on the cancer cell lines tested with IC50 values ranging from 24.8 to 44.1 μg/mℓ; while all the fractions of Aloe arborescens and A. striatula had insignificant or no cytotoxic effects after 72 h of treatment.ConclusionsOur results indicate that the methanol fraction of E. autumnalis had a profound cytotoxic effect even though it possessed very significant antibacterial activity. This puts a query on its safety and hence a call for caution in its usage, thus a product being natural is not tantamount to being entirely safe. However, the antibacterial activities and non-cytotoxic effects of A. arborescens and A. striatula validates their continuous usage in ethnomedicine.