Antimicrobial mechanism of β-glycyrrhetinic acid isolated from licorice, Glycyrrhiza glabra

-Glycyrrhetinic acid isolated from Glycyrrhiza glabra had an antibacterial activity of 7.6 and 12.5 g ml^–1 against Bacillus subtilis and Staphylococcus epidermidis without causing hemolysis of human erythrocytes, whereas it was not inhibitory against Escherichia coli, Proteus vulgaris and various fungi. Confocal microscopy showed that -glycyrrhetinic acid was located within the bacteria but had not caused membrane disruption. It then inhibited synthesis of DNA, RNA and protein.     

Antimicrobial activity of FeIII,CuII, AgI,ZnII and HgII complexes of 2-(2-hydroxy-5-bromo/nitro-phenyl)-1H- and 2-(2-hydroxyphenyl)-5-methyl/chloro/nitro-1H-benzimidazoles

Antimicrobial activity of 2-(2-hydroxyphenyl)-5-R⁵-1H-benzimidazoles, 2-(2-hydroxy-5-R^5′-phenyl)-1H-benzimidazoles and their Fe^III, Cu^II, Ag^I, Zn^II and Hg^II nitrate complexes was tested towardStaphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri, andProteus mirabilis. Antifungal activity was tested againstCandida albicans. Benzimidazole benzene ring substituents increase the antimicrobial activity, phenol ring substituents decrease it. The ligands show an antibacterial effect against onlyS. aureus whereas Ag^I and Hg^II complexes of the ligands have a higher activity with respect to the other complexes to all the bacteria. On the other hand, Fe^III complexes show a considerable activity againstS. aureus andS. epidermidis.     

Analysis of functional properties of <Emphasis Type="Italic">Lactobacillus acidophilus</Emphasis>

Metabolites from Lactobacillus acidophilus were analysed. The results showed that Lactobacillus acidophilus Ind-1 and Lactobacillus acidophilus Lakcid produced respectively 12.73 g and 13.33 g lactic acid l⁻¹ after incubating in skim milk at 37 °C for 36 h; and 2.229 unit and 1.808 unit β-galactosidase l⁻¹ in an MRS medium. The proteolytic activity of Lactobacillus acidophilus was high and the content of 17 free amino acids in the fermented milk of Lactobacillus acidophilus Ind-1 and Lactobacillus acidophilus Lakcid was 394.4 mg l⁻¹ and 563.2 mg l⁻¹, respectively. Meantime, Lactobacillus acidophilus reduced cholesterol level in an MRS medium supplemented with cholesterol. Furthermore, Lactobacillus acidophilus Ind-1 and Lactobacillus acidophilus Lakcid showed antimicrobial activity against Bacillus anthracis and Escherichia coli.     

Analysis of glucose catabolites by using head-space gas chromatography for differentiation of some Gram-negative species

Volatile products from the degradation of glucose by a total of 66 strains ofEnterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Proteus vulgaris, andPseudomonas aeruginosa were analyzed by head-space gas chromatography. The bacteria were incubated for 1 h in a glucose-containing buffer solution before being analyzed by gas chromatography, using manual, semiautomatic, and automatic head-space injection. From the chromatographic patterns obtained, all strains could be differentiated as to species, with the exception of two strains ofProteus mirabilis, which gave chromatograms similar to those produced byProteus vulgaris. The gas chromatographic head-space technique developed provides a rapid and easily performed means for identification of bacteria, particularly when using an automatic injection unit, as exemplified in this study on some of the Gram-negative species commonly encountered in urinary tract infections.     

Bacteria competing with the adhesion and biofilm formation by <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

The activity of antagonistic substances produced by Pseudomonas aeruginosa and Lactobacillus acidophilus against the planktonic and sessile populations of Staphylococcus aureus strains was demonstrated. The strongest effects were caused by probiotic L. acidophilus strain — bacteriocin-like inhibitory substances (BLIS) positive. However, the S. aureus A3 growth, adhesion and biofilm formation was also limited by cell-free supernatant of L. acidophilus H-1 (BLIS negative). Moreover, competitive direct interactions were observed between staphylococci and the above bacteria, which influenced the formation of dualspecies aggregates on the surface.     

Actinomycin-Producing Endophytic Streptomyces parvulus Associated with Root of Aloe vera and Optimization of Conditions for Antibiotic Production

Endophytic actinomycetes are a rich source of novel antimicrobial compounds. The aim of this study was to evaluate the production of antimicrobial compound by endophytic Streptomyces sp. Av-R5 associated with root of Aloe vera against multidrug-resistant human pathogens. The 16S rRNA sequence of the isolate Av-R5 has been identified as Streptomyces parvulus NBRC 13193^T (AB184326) and the sequence was submitted to the National Center for Biotechnology Information (NCBI) GenBank database (accession number KY771080). Streptomyces parvulus Av-R5 grown under submerged fermentation condition optimized by central composite design (glucose 11.16 g/L, soybean meal 10.25 g/L, sodium chloride 11.18 g/L, calcium carbonate 1.32 g/L at pH 7.19 at 31.42 °C with 6.04% seed inoculum for 10 days of incubation) exhibited the highest activity against multidrug-resistant Staphylococcus aureus JNMC-3, Staphylococcus epidermidis JNMC-4, Klebsiella pneumoniae MTCC-3384, Klebsiella pneumoniae JNMC-6, Pseudomonas aeruginosa MTCC-741, Proteus vulgaris JNMC-7, Candida albicans MTCC-183, and Aspergillus niger MTCC-872. The structures of the active compounds were elucidated by UV-Vis spectroscopy, ¹H and ¹³C NMR, FT-IR, and ESIMS. Actinomycin D and actinomycin X_0β were detected in crude extracts and major components were eluted by HPLC at 10.96 and 6.81 min, respectively. In this case, a high yield of actinomycin D and actinomycin X_0β (400 mg/L) was achieved with Streptomyces parvulus Av-R5, fermented in glucose soybean meal broth media, which can be used in industrial fermentation process to obtain high yields.

     

Microwave-assisted synthesis of antimicrobial agents based on pyridazine moiety

An efficient and simple microwave assisted synthesis of sulfonamide derivatives incorporating the pyridazine moiety has been developed. These sulfonamides were used for the preparation of new heterocyclic compounds via reaction with different reagents using a microwave irradiation technique. The structures of the newly synthesized compounds were confirmed on the basis of FTIR, ¹H and ¹³C-NMR, mass spectral techniques and elemental analyses. Some of the new synthesized compounds were assayed for their in vitro antibacterial activity against Gram-positive bacteria, Staphylococcus aureus and Staphylococcus epidermidis, Gram-negative bacteria, Escherichia coli and Klebsiella pneumonia and antifungal activity against Aspergillus fumigatus and Candida albicans. Most of the new compounds showed significant antibacterial and antifungal activity.     

Altered bacterial culture density following exposure to aflatoxins

Summary Eight species of bacteria were incubated in culture media containing 10 g/ml aflatoxin B₁ (AFB₁), aflatoxin B₂ (AFB₂), or aflatoxin G₂ (AFG₂). Their culture density at 20°C was determined at four and eight days (d) after inoculation. In all species of bacteria studied (Bacillus cereus, Proteus mirabilis, Erysipylothrix rusiopathie (insidiosa), Streptococcus fecalis, Staphylococcus epidermis, Klebsiella pneumoniae, Micrococcus spp., andEscherichia coli), AFB₁, AFB₂ and AFG₂ substantially decreased culture sizes at 4 d, but not at 8 d. InB. cereus andP. mirabilis, culture sizes were increased by AFB₁, AFB₂, and AFG₂ at 8 d post inoculation. These results indicate that AFB₁, AFB₂, and AFG₂ suppressed initial growth of these species in vitro, while later growth in some species was either unaltered or enhanced.     

A quantitative assessment of the antimicrobial activity of garlic (Allium sativum)

An aqueous extract of freeze-dried garlic (Allium sativum), when incorporated into growth media, inhibited many representative bacteria, yeasts, fungi and a virus. All microorganisms tested were susceptible to garlic. Quantitative assessment of the minimum inhibitory concentrations for bacteria and yeasts showed values ranging from 0.8 to 40.0 mg garlic ml^-1. Fungal radial colony growth was inhibited by at least 25% at concentrations as low as 2.0 mg garlic ml^-1. The 50% endpoint neutralization titre for rotavirus was 2.4 to 2.8 g ml^-1. Lactic acid bacteria were the least sensitive microorganisms to the inhibitory effects of garlic. In mixed culture studies of Lactobacillus acidophilus and Escherichia coli, garlic prevented the establishment of E. coli, although the final outcome of competition was not affected.L.P. Rees, S.F. Minney and N.T. Plummer are with Interprise Ltd, Baglan Bay Industrial Park, Port Talbot SA 12 7DJ, UK. J.H. Slater and D.A. Skyrme are with the School of Pure and Applied Biology, University of Wales, Cardiff, P.O. Box 915, Cardiff CF1 3TL, UK.     

Isolation,Identification and Screening of Potential Probiotic Bacteria in Milk from South African Saanen Goats

This study aimed to evaluate lactic acid bacteria isolates from Saanen goats’ milk for probiotic attributes, thereby determining their potential as direct-fed microbials for goats. Isolates were identified using API 50CH system, 16S rDNA sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry. All 17 isolates obtained were identified as Lactobacillus plantarum except one identified as Pediococcus acidilactici. Four isolates identified as L. plantarum (Accession numbers KJ026587.1, KM207826.1, KC83663.1 and KJ958428.1) by at least two of the techniques used and isolate 17 differently identified by all the methods used were selected as representatives and then screened for probiotic properties. These isolates displayed phenotypic probiotic attributes including tolerance to acid and bile salts, ability to adhere to intestines and possession of antagonistic activities against Proteus vulgaris, Staphylococcus aureus, Salmonella typhimurium, Pseudomonas aeruginosa and Escherichia coli. The lactic acid bacteria isolated from Saanen goats’ milk showed potential to be used as sustainable probiotics in goats’ industry. Successful use of probiotics in animals depends upon availability of appropriate isolates originating from the specific host animal. This study is a positive contribution towards identification of isolates with potential for formulation as direct-fed microbials for South African Saanen goats.     

Bladder cytopathic effects associated with Gram-negative bacterial genera

The interaction of bacteria belonging to several genera with the bladder epithelium was studied. An in vivo rat bladder model system was used to evaluate the cytopathic effects of members of eight representative genera of bacteria and six strains ofEscherichia coli on the bladder surface. Alterations were noted mainly with the Gram-negative bacteria (Escherichia, Klebsiella, Enterobacter, Proteus, Pseudomonas), although some strains were associated with more cytopathology than others. Foci of cytopathology consisted of swelling, exfoliated epithelial cells, strand formation, and ulceration. Aggregates of bacteria, epithelial cells, and debris were shed into the bladder lumen. In contrast, members of three genera of Gram-positive organisms (Lactobacillus, Streptococcus, Staphylococcus) caused little or no cytopathology. The study strongly suggests that the bladder responds in a relatively uniform manner to viable Gram-negative organisms, while the response to Gram-positive organisms is minimal.     

Antimicrobial activity of naphthoquinones from Fusaria

Twenty-two naphthoquinone compounds isolated or derived synthetically from culture extracts ofFusarium solani andF. oxysporum were examined for antimicrobial activity. Fifteen exhibited antibiotic activity againstStaphylococcus aureus, and 12 were active againstStreptococcus pyogenes, but none were active at the highest rate of 128 g/ml againstEscherichia coli, Klebsiella pneumoniae, Salmonella typhi, Proteus vulgaris, Serratia marcescens, orPseudomonas aeruginosa. Of 8 plant pathogenic bacteria tested against 11 naphthoquinones,Corynebacterium poinsettiae was inhibited by 6 compounds, andPseudomonas viridiflava was weakly inhibited by one. Only one of a group of 6 fluorescent soil pseudomonads was inhibited by one naphthoquinone. Antifungal activity of 10 compounds against 8 fungal plant pathogens was limited to inhibition ofPhytophthora parasitica by one naphthopyran.South Atlantic, Agricultural Research Service, U.S. Department of Agriculture. Mention of a trademark or proprietary product is for identification only and does not imply a warranty or guarantee of the product by the U.S. Department of Agriculture over other products which may also be suitable.     

Growth of Ag-nanoparticles in an aqueous solution and their antimicrobial activities against Gram positive,Gram negative bacterial strains and Candida fungus

Silver nanoparticles (AgNPs) were synthesized using Ocimum sanctum (Tulsi) leaves aqueous extract as reducing as well as a capping agent in absence and presence of cetyltrimethylammonium bromide (CTAB). The resulting nanomaterials were characterized by UV–visible spectrophotometer, and transmission electron microscope. The UV–Vis spectroscopy revealed the formation of AgNPs at 400–450 nm. TEM photographs indicate that the truncated triangular silver nanoplates and/or spherical morphology of the AgNPs with an average diameter of 25 nm have been distorted markedly in presence of CTAB. The AgNPs were almost mono disperse in nature. Antimicrobial activities of AgNPs were determined by using two bacteria (Gram positive Staphylococcus aureus MTCC-3160), Gram negative Escherichia coli MTCC-450) and one species of Candida fungus (Candida albicans ATCC 90030) with Kirby-Bauer or disc diffusion method. The zone of inhibition seems extremely good showing a relatively large zone of inhibition in both Staphylococcus aureus, Escherichia coli, and Candida albicans strains.     

Copper Oxide Nanomaterials Derived from Zanthoxylum armatum DC. and Berberis lycium Royle Plant Species: Characterization,Assessment of Free Radical Scavenging and Antibacterial Activity

Copper oxide nanomaterials were synthesized by a facile sustainable biological method using two plant species (Zanthoxylum armatum DC. and Berberis lycium Royle ). The formation of materials was confirmed by FT‐IR, ATR, UV‐visible, XRD, TEM, SEM, EDX, TGA and PL. The antibacterial activity was evaluated by agar well diffusion method to ascertain the efficacy of plant species extract and extract derived copper oxide nanomaterials against six Gram‐positive bacteria namely Staphylococcus aureus, Streptococcus mutans, Streptococcus pyogenes, Corynebacterium diphtheriae, Corynebacterium xerosis, Bacillus cereus and four Gram‐negative bacteria such as Klebsiella pneumonia, Escherichia coli, Pseudomonas aeruginosa and Proteus vulgaris against the standard drug, Ciprofloxacin for Gram‐positive and Gentamicin for Gram‐negative bacteria, respectively. In both cases, copper oxide nanomaterials were found to be sensitive in all the bacterial species. Sensitivity of copper oxide nanomaterials shows an be higher as compared to plant species extract against different bacteria. Scavenging activity of plant extracts along with nanomaterials have been accessed using previously reported protocols employing ascorbic acid as standard. Scavenging activity of copper oxide nanomaterials shows an increase with increase in concentration. The biological activity (bactericidal and scavenging efficiency) of plant derived copper oxide nanomaterials revealed that these materials can be used as potent antimicrobial agent and DPPH scavengers in industrial as well as pharmacological fields.     

Probiotic Strawberry Yogurts: Microbiological,Chemical and Sensory Properties

This study was performed to determine the viability of Lactobacillus acidophilus and Bifidobacterium bifidum in yogurt made with strawberry marmalade (SM) and to examine the quality properties of probiotic yogurt. Acidity, pH, bacterial counts and sensory analysis of the yogurt samples were investigated on days 1, 3, 5, 7, 10 and 14 during storage at 4 °C. The survival rate of L. acidophilus was greater than that of B. bifidum. The viability of L. acidophilus decreased during the storage period, but B. bifidum numbers remained stable during the storage period. The highest L. acidophilus count (7.20 log cfu/g) was found in L. acidophilus + B. bifidum SM yogurt on day 1. The highest B. bifidum count (6.13 log cfu/g) was detected in yogurt containing L. acidophilus + B. bifidum SM yogurt on day 7. Yeast and mould counts of all yogurts increased during the storage period. Coliform bacteria and Staphylococcus aureus were not detected in the yogurt samples. The highest overall acceptance sensory score was observed in yogurts containing L. acidophilus. Considering the sensory and probiotic characteristics of all yogurt samples, this study suggested that strawberry yogurt with a suitable 5–7 day storage period can be produced with single L. acidophilus addition or single B. bifidum addition.     

Synthesis and evaluation of a class of new coumarin triazole derivatives as potential antimicrobial agents

A series of new coumarin-based 1,2,4-triazole derivatives were designed, synthesized and evaluated for their antimicrobial activities in vitro against four Gram-positive bacteria (Staphylococcus aureus, MRSA, Bacillus subtilis and Micrococcus luteus), four Gram-negative bacteria (Escherichia coli, Proteus vulgaris, Salmonella typhi and Shigella dysenteriae) as well as three fungi (Candida albicans, Saccharomyces cerevisiae and Aspergillus fumigatus) by two-fold serial dilution technique. The bioactive assay showed that some synthesized coumarin triazoles displayed comparable or even better antibacterial and antifungal efficacy in comparison with reference drugs Enoxacin, Chloromycin and Fluconazole. Coumarin bis-triazole compounds exhibited stronger antibacterial and antifungal efficiency than their corresponding mono-triazole derivatives.     

玫瑰精油的化学成分及其抗菌活性

通过水蒸汽同步蒸馏法提取玫瑰精油,采用GC-MS方法分析了玫瑰精油的化学组成,共鉴定出其中14个化学成分并测定其相对含量,占总含量的95.25%。香茅醇为玫瑰精油的主要成分,相对含量为90.37%。体外抑菌实验表明,玫瑰精油除对黑曲霉没有抗菌活性外,对其它7种供试菌均具有不同程度的抑制作用,其中对表皮葡萄球菌、金黄色葡萄球菌和大肠杆菌的最小抑菌浓度(MIC)为0.063%(v/v),对枯草芽孢杆菌、变形杆菌和白色念珠菌的最小抑菌浓度（MIC）为0.125%(v/v),而对绿脓杆菌(Pseudomonas aeruginosa)的抗菌活性相对较弱,MIC为0.5%(v/v)。抑菌直径结果也表明了玫瑰精油除对黑曲霉、绿脓杆菌的抗菌活性较弱外,对其它6种菌株的抑菌直径都大于8.5 mm。考察了玫瑰精油对3种敏感菌株包括金黄色葡萄球菌(革兰氏阳性菌)、大肠杆菌(革兰氏阴性菌)和白色念珠菌(真菌)的杀菌动态过程,为玫瑰精油的应用提供了理论依据。     

Production of the medicinal and prophylactic preparation enterobifidin usingBifidobacterium adolescentis MS-42

Production of Enterobifidin includes the stages of preparation of culture media, reparation of lyophilizedBifidobacterium adolescentis MS-42 culture, preparation of starters, cultivation of bacteria in fermenters, biomass conservation, and its biological control. The preparation contains physiologically active bifidobacterium cells with high activities of growth(μ = 0.7 h⁻¹,g = 1.0 h) and acid formation (titratable acidity is ∼120–140°T; acetate concentration, 0.50–0.75%; and lactate concentration, 0.33–0.50%). The antagonistic activity of these bacteria towardsEscherichia coli 08,E. coli 086,E. coli 015,E. coli 0115, andE. coli 0101 amounts to 98.2; toProteus vulgaris 102, to 87.2; andStaphylococcus aureus 209p, to 83.2%. The bifidobacteria (with a titer of ∼10⁹ CFU/ml) remained viable for two to five months.     

Resveratrol,pterostilbene, and baicalein: plant-derived anti-biofilm agents

Microbial adhesion to surfaces and the subsequent biofilm formation may result in contamination in food industry and in healthcare-associated infections and may significantly affect postoperative care. Some plants produce substances with antioxidant and antimicrobial properties that are able to inhibit the growth of food-borne pathogens. The aim of our study was to evaluate antimicrobial and anti-biofilm effect of baicalein, resveratrol, and pterostilbene on Candida albicans, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli. We determined the minimum inhibitory concentrations (MIC), the minimum adhesion inhibitory concentration (MAIC), and the minimum biofilm eradication concentration (MBEC) by crystal violet and XTT determination. Resveratrol and pterostilbene have been shown to inhibit the formation of biofilms as well as to disrupt preformed biofilms. Our results suggest that resveratrol and pterostilbene appear potentially very useful to control and inhibit biofilm contaminations by Candida albicans, Staphylococcus epidermidis, and Escherichia coli in the food industry.     

Antimicrobial activity and biofilm formation inhibition of green tea polyphenols on human teeth

The antimicrobial effects and biofilm formation inhibition of tea polyphenols (TPP) extracted from Korean green tea (Camellia sinensis L) were evaluated against 12 oral microorganisms. Effective antimicrobial activity against all microorganisms tested, including Lactobacillus spp. (Lactobacillus acidophilus and Lactobacillus plantarum), Streptococcus spp. (Streptococcus mutans, Streptococcus sanguis, Streptococcus sobrinus, Streptococcus mitis, and Streptococcus salivarius), Staphylococcus aureus, Neisseria meningitidis, Escherichia coli, Enterobacter cloacae, Enterococcus faecalis, and Candida albicans, was shown at 2,000 μg/mL TPP within 5 min of incubation. Scanning electron microscopy (SEM) analysis revealed various morphological changes, such as the presence of perforations, the formation of cell aggregates, and the leakage of cytoplasmic materials from cells treated with TPP, depending on the bacteria. The potential role of TPP in biofilm formation inhibition on human teeth was evaluated in BHI broth with 2 mixed strains of S. mutans and S. sanguis. SEM analysis showed biofilm formation on the surface of a tooth shaken only in saline solution, whereas almost no biofilm was observed on a tooth incubated in TPP solution. This result suggests that TPP is effective against adherent cells of S. mutans and S. sanguis. Thus, TPP would be useful for development as an antimicrobial agent against oral microorganisms, and has great potential for use in mouthwash solutions for the prevention and treatment of dental caries.