Antibacterial and antilarval activity of deep-sea bacteria from sediments of the West Pacific Ocean

Deep-sea microorganisms are a new source of bioactive compounds. In this study, crude ethyl acetate extracts of 176 strains of deep-sea bacteria, isolated from sediments of the West Pacific Ocean, were screened for their antibacterial activity against four test bacterial strains isolated from marine biofilms. Of these, 28 deep-sea bacterial strains exhibited antibacterial activity against one or more of the bacteria tested. Active deep-sea bacterial strains belonged mainly to the genera of Pseudomonas, Psychrobacter and Halomonas. Additionally, antilarval activity of 56 deep-sea bacterial strains was screened using Balanus amphitrite larvae. Seven bacterial strains produced metabolites that had strong inhibitive effects on larval settlement. None of these metabolites showed significant toxicity. The crude extract of one deep-sea Streptomyces strain could completely inhibit larval settlement at a concentration of 25 microg ml(-1).     

Synthesis of novel steroidal heterocyclic derivatives as antibacterial agents

This study aimed at the synthesis of novel structurally promising steroidal heterocycles and to elucidate the potential role of these compounds as antibacterial agents. Epi-androsterone 1 reacted with CS2 and sodium hydride in dimethylsulfoxide to yield alpha-oxoketene dithiodisodium salt 2. The non-isolable salt 2 reacted with acetyl chloride, benzoyl chloride, phenacyl bromide and iodomethane to afford the corresponding alpha-oxodithioacetal derivatives 4a,b, 6 and 7, respectively. Interaction of 2 with the alkyl halide reagents 8a-d yielded the corresponding thiophene derivatives 10a-d. Alpha-oxoketene dithioacetal 7 reacted with urea and thiourea to furnish the pyrimidinoandrostane derivatives 12a,b. Compound 7 also reacted with ortho-phenylene diamine and ortho-aminophenol 13a,b to produce the dinucleophilic adducts 15a,b. The in vitro antibacterial evaluation of some newly prepared compounds showed that all compounds have high significant antibacterial activity against the used strains of gram positive and gram negative bacteria.     

Antibacterial, antifungal and cytotoxic activity of terrestrial cyanobacterial strains from Serbia

Cyanobacteria are known to be a rich source of biologically active compounds some of which can have pharmaceutical importance. In this work we present the screening results of cyanobacterial strains for their antibacterial, antifungal, and cytotoxic activity. Cyanobacterial strains were isolated from various soil types in province of Vojvodina and Central Serbia, Republic of Serbia. The screening included 9 strains of Anabaena and 9 strains of Nostoc. Both, extracellular products (from the culture liquid) and cellular crude lipophilic extracts were tested against 13 bacterial strains and 8 fungal strains. Cytotoxic activity was tested against three human cell lines. Methanol extracts were prepared according to ?stensvik. Antibacterial and antifungal activities were determined measuring inhibition zone, 48 h after inoculation. The cytotoxic activity was determined by sulforhodamine B (SRB) colorimetric assay. Of all cyanobacterial strains tested, 52% showed some antifungal and 41% antibacterial activity. Two out of six tested strains possessed cytotoxic activity. The cytotoxic activity of Anabaena strain S12 was found both in culture liquid and crude cell extract. It occurred specifically between the 21st and 42nd day of cultivation against HeLa and MCF7 cells, but had no activity against cell line derived from a healthy tissue. A high percentage of the active strains among the tested strains justify the effort of screening cyanobacteria that are isolated from terrestrial environments. The most promising strains for the fur- ther study are Anabaena strain S12 which showed strong cytotoxic and antibacterial activity and Ana- baena strain S20 which produces a potent antifungal compound. The future work, besides further screening and chemical identification of the active compounds, should also include the development of culture techniques that would lead to more efficient production of biologically active compounds.     

Antibacterial and antilarval activity of deep-sea bacteria from sediments of the West Pacific Ocean

Abstract

Deep-sea microorganisms are a new source of bioactive compounds. In this study, crude ethyl acetate extracts of 176 strains of deep-sea bacteria, isolated from sediments of the West Pacific Ocean, were screened for their antibacterial activity against four test bacterial strains isolated from marine biofilms. Of these, 28 deep-sea bacterial strains exhibited antibacterial activity against one or more of the bacteria tested. Active deep-sea bacterial strains belonged mainly to the genera of Pseudomonas, Psychrobacter and Halomonas. Additionally, antilarval activity of 56 deep-sea bacterial strains was screened using Balanus amphitrite larvae. Seven bacterial strains produced metabolites that had strong inhibitive effects on larval settlement. None of these metabolites showed significant toxicity. The crude extract of one deep-sea Streptomyces strain could completely inhibit larval settlement at a concentration of 25 μg ml^?1.     

Antibacterial spectrum and cytotoxic activities of serrulatane compounds from the Australian medicinal plant Eremophila neglecta

Aims: To determine the antibacterial spectrum and cytotoxic activities of serrulatane compounds from the Australian plant Eremophila neglecta. Methods and Results: Antimicrobial activities of serrulatane compounds 8,19‐dihydroxyserrulat‐14‐ene ( 1 ) and 8‐hydroxyserrulat‐14‐en‐19‐oic acid ( 2 ) were tested against Gram‐negative and Gram‐positive bacteria including human and veterinary pathogens and some multidrug‐resistant isolates. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of the compounds were determined by broth microdilution assay. Both compounds exhibited antibacterial activity against all Gram‐positive test strains. They showed antimycobacterial activity against isolates of Mycobacterium fortuitum and Mycobacterium chelonae. Of the five Gram‐negative bacteria tested, only Moraxella catarrhalis showed susceptibility to the compounds. Cytotoxic activities were tested in the Vero cell line. Compound 1 showed more activity than 2 in both antibacterial and cytotoxicity assays with cytotoxicity at concentrations similar to the MBC. Conclusions: Serrulatane compounds showed significant activity against medically important bacteria, with 1 exhibiting stronger antibacterial activity. However, they also displayed toxicity to mammalian cells. Significance and Impact of the Study: Serrulatanes are of interest as novel antibacterial compounds for use in biomedical applications; this study reports data obtained with a range of bacterial strains and mammalian cells, essential for assessing the capabilities and limitations of potential applicability of these compounds.     

Synthesis and biological evaluation of novel N-acyl substituted quinolin-2(1H)-one derivatives as potential antimicrobial agents

A series of novel N-acyl substituted quinolin-2(1H)-one derivatives were synthesized and screened in vitro for their antibacterial and antifungal activities by disc diffusion method. All the compounds exhibited moderate to good antimicrobial activities, some of these compounds displayed comparable or better antibacterial or antifungal activities against some tested strains compared to the reference drugs Streptomycin and Fluconazole.     

Enhanced biofilm formation and increased resistance to antimicrobial agents and bacterial invasion are caused by synergistic interactions in multispecies biofilms

Most biofilms in their natural environments are likely to consist of consortia of species that influence each other in synergistic and antagonistic manners. However, few reports specifically address interactions within multispecies biofilms. In this study, 17 epiphytic bacterial strains, isolated from the surface of the marine alga Ulva australis, were screened for synergistic interactions within biofilms when present together in different combinations. Four isolates, Microbacterium phyllosphaerae, Shewanella japonica, Dokdonia donghaensis, and Acinetobacter lwoffii, were found to interact synergistically in biofilms formed in 96-well microtiter plates: biofilm biomass was observed to increase by >167% in biofilms formed by the four strains compared to biofilms composed of single strains. When exposed to the antibacterial agent hydrogen peroxide or tetracycline, the relative activity (exposed versus nonexposed biofilms) of the four-species biofilm was markedly higher than that in any of the single-species biofilms. Moreover, in biofilms established on glass surfaces in flow cells and subjected to invasion by the antibacterial protein-producing Pseudoalteromonas tunicata, the four-species biofilms resisted invasion to a greater extent than did the biofilms formed by the single species. Replacement of each strain by its cell-free culture supernatant suggested that synergy was dependent both on species-specific physical interactions between cells and on extracellular secreted factors or less specific interactions. In summary, our data strongly indicate that synergistic effects promote biofilm biomass and resistance of the biofilm to antimicrobial agents and bacterial invasion in multispecies biofilms.     

Chemical Constituents and Antimicrobial Activity of Indian Green Leafy Vegetable Cardiospermum halicacabum

The present study was carried out to analyze chemical constituents and antibacterial activity of ethanolic leaf extract of Cardiospermum halicacabum (ECH). The FT-IR spectrum confirmed the presence of alcohols, phenols, alkanes, alkynes, aliphatic ester and flavonoids in ECH. The GC–MS analysis revealed that ECH contained about twenty four compounds. The major chemical compounds identified were cyclohexane-1, 4, 5-triol-3-one-1-carboxylic acid, benzene acetic acid, caryophyllene, phytol and neophytadiene. The ECH was screened for its antibacterial activity against different bacterial strains and anti fungal activity against Candida albicans by agar well diffusion and minimum inhibitory concentration (MIC) assay. ECH exhibited antibacterial and antifungal activity. All the tested bacterial strains showed MIC values ranging from 80 to 125 μg of extract/ml and C. albicans showed 190 μg of extract/ml as a MIC. The maximum activity ECH was observed against human pathogen Staphylococcus aureus followed by Escherichia coli and the fish pathogen Aeromonas hydrophila. ECH exhibited moderate activity against some of the tested multidrug resistant strains.     

生姜中6个姜辣素类成分的抗菌活性研究

为了探究生姜化学成分的抗菌活性及初步构效关系,采用色谱法从生姜中分离得到6个姜辣素类化合物,采用波谱法对这6个成分进行鉴定,分别为5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-4-decen-3-one(1)、5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-4-dodecen-3-one(2)、5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-4-tetradecane-3-one(3)、[6]-姜酚(4)、[8]-姜酚(5)和[10]-姜酚(6)。采用抗菌纸片扩散法测定6个化合物对15株病原菌株的抗菌活性。结果表明化合物1和4抗菌活性最好,而6对所有菌株均无活性。初步构效关系分析表明:烯醇型化合物对革兰氏阳性菌的抗菌活性优于姜酚型化合物;而姜酚型化合物对革兰氏阴性菌的抗菌活性优于烯醇型化合物。此外,姜辣素类成分脂肪链的长度增加,可能导致抗菌活性降低。     

Enhanced Biofilm Formation and Increased Resistance to Antimicrobial Agents and Bacterial Invasion Are Caused by Synergistic Interactions in Multispecies Biofilms

Most biofilms in their natural environments are likely to consist of consortia of species that influence each other in synergistic and antagonistic manners. However, few reports specifically address interactions within multispecies biofilms. In this study, 17 epiphytic bacterial strains, isolated from the surface of the marine alga Ulva australis, were screened for synergistic interactions within biofilms when present together in different combinations. Four isolates, Microbacterium phyllosphaerae, Shewanella japonica, Dokdonia donghaensis, and Acinetobacter lwoffii, were found to interact synergistically in biofilms formed in 96-well microtiter plates: biofilm biomass was observed to increase by >167% in biofilms formed by the four strains compared to biofilms composed of single strains. When exposed to the antibacterial agent hydrogen peroxide or tetracycline, the relative activity (exposed versus nonexposed biofilms) of the four-species biofilm was markedly higher than that in any of the single-species biofilms. Moreover, in biofilms established on glass surfaces in flow cells and subjected to invasion by the antibacterial protein-producing Pseudoalteromonas tunicata, the four-species biofilms resisted invasion to a greater extent than did the biofilms formed by the single species. Replacement of each strain by its cell-free culture supernatant suggested that synergy was dependent both on species-specific physical interactions between cells and on extracellular secreted factors or less specific interactions. In summary, our data strongly indicate that synergistic effects promote biofilm biomass and resistance of the biofilm to antimicrobial agents and bacterial invasion in multispecies biofilms.     

Biofilm formation and the presence of the intercellular adhesion locus ica among staphylococci from food and food processing environments

In clinical staphylococci, the presence of the ica genes and biofilm formation are considered important for virulence. Biofilm formation may also be of importance for survival and virulence in food-related staphylococci. In the present work, staphylococci from the food industry were found to differ greatly in their abilities to form biofilms on polystyrene. A total of 7 and 21 of 144 food-related strains were found to be strong and weak biofilm formers, respectively. Glucose and sodium chloride stimulated biofilm formation. The biofilm-forming strains belonged to nine different coagulase-negative species of Staphylococcus. The icaA gene of the intercellular adhesion locus was detected by Southern blotting and hybridization in 38 of 67 food-related strains tested. The presence of icaA was positively correlated with strong biofilm formation. The icaA gene was partly sequenced for 22 food-related strains from nine different species of Staphylococcus, and their icaA genes were found to have DNA similarities to previously sequenced icaA genes of 69 to 100%. Northern blot analysis indicated that the expression of the ica genes was higher in strong biofilm formers than that seen with strains not forming biofilms. Biofilm formation on polystyrene was positively correlated with biofilm formation on stainless steel and with resistance to quaternary ammonium compounds, a group of disinfectants.     

8-hydroxyquinoline and quinazoline derivatives as potential new alternatives to combat Candida spp. biofilm

Often associated to the colonization by Candida spp. biofilm, the catheter-related infections are a serious health problem since the absence of a specific therapy. Hence, the main objective of this work was to evaluate the activity of 8-hydroxyquinoline and quinazoline derivatives on Candida spp. biofilms. A quinazoline derivative (PH100) and an 8-hydroxyquinoline derivative (PH157) were tested against nine strains of C. albicans, C. tropicalis and C. parapsilosis, and their biofilms in polystyrene microtitre plates and on polyurethane central venous catheter. The PH157 compound was incorporated into a film-forming system-type formulation and its capacity to inhibit biofilm formation on catheters was evaluated. The compounds were active against planktonic and sessile cells, as well as against the tested biofilms. PH157 compound performed better than the PH100 compound. The formulation containing PH157 presented results very similar to those of the compound in solution, which indicates that its activity was preserved. Both compounds showed activity against Candida spp. strains and their biofilm, with better PH157 activity. The formulation preserved the action of the PH157 compound, in addition, it facilitates its application on the catheter. The structural modifications that these compounds allow can generate compounds that are even more active, both against planktonic cells and biofilms.     

Solute size effects on the diffusion in biofilms of Streptococcus mutans

The diffusion of poly(ethylene glycol) (PEG) (MW varying between 200 and 10,000), and of three different types of micelles was examined in Streptococcus mutans biofilms using infrared spectroscopy. PEGs were used because they show limited interactions with biological materials and their weight can be selected in order to cover a wide range of size. The study showed that a considerable fraction at the base of the biofilm was not accessible to the diffusing solute molecules and this inaccessible fraction was very dependent on the size of the diffusing molecules. In parallel, it was found that the diffusion coefficients of these solutes in the biofilms were less than those in water and this reduction was less pronounced for large macromolecules, an effect proposed to be related to their limited penetration. Triton X-100, a neutral detergent, forms micelles that behave like PEG, suggesting that the behaviour observed for neutral macromolecules can be extrapolated to neutral macroassemblies. However, the diffusion, as well as the penetration of sodium dodecylsulphate micelles (a negatively charged surfactant) and cetylpyridinium chloride micelles (positively charged), in the biofilms appeared to be significantly influenced by electrostatic interactions with biofilm components. The present findings provide useful insights associated with the molecular parameters required to efficiently penetrate bacterial biofilms. The study suggests a rationale for the limited bactericidal power of some antibiotics (the large ones). The restricted accessibility of macromolecules and macroassemblies to biofilms must be examined carefully in order to offer guidelines in the development of novel antibacterial treatments.     

The inhibitory activity of pomelo essential oil on the bacterial biofilms development on soft contact lenses

The aim of present study was to investigate the microbial colonization of worn contact lenses (CLs) and to evaluate the inhibitory effect of pomelo (Citrus maxima) peels essential oil on the biofilm development on unworn CLs. The essential oil was isolated by steam distillation and analyzed by gas chromatography coupled with mass spectrometry, twenty compounds being isolated. The antimicrobial activity of pomelo oil was tested against S. epidermidis and P. aeruginosa strains, known for their ability to develop biofilms on prosthetic devices, by qualitative screening methods and quantitative assay of the minimal inhibitory concentrations (MIC) in order to evaluate the antibiofilm activity. Our study revealed that all worn CLs where 100% colonized by staphylococci and Enterobacteriaceae strains. The pomelo essential oil inhibited the development of bacterial biofilms formed by Gram-positive and Gram-negative microorganisms on soft CLs, its antibiofilm activity being specific and dependent on different physical parameters (contact time and temperature). The architecture of bacterial biofilms developed on soft contact lenses was analyzed using confocal scanning laser microscopy (CSLM).     

Modulation of antibiotic resistance in bacterial pathogens by oleanolic acid and ursolic acid

Antibiotic resistance among bacterial pathogens is a serious problem for human and veterinary medicine, which necessitates the development of novel therapeutics and antimicrobial strategies. Some plant-derived compounds, e.g. pentacyclic triterpenoids such as oleanolic acid (OA) and ursolic acid (UA), have potential as a new class of antibacterial agents as they are active against many bacterial species, both Gram-positive and Gram-negative, and specifically target the cell envelope. The aim of the present study was to investigate the influence of OA and UA on the susceptibility of four bacterial pathogens (Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus and Staphylococcus epidermidis) to the β-lactam antibiotics ampicillin (Ap) and oxacillin (Ox). Antimicrobial assays were conducted with bacteria growing in liquid suspension cultures (planktonic cells) or as biofilms. Using FICI value estimation and the time-kill method it was demonstrated that in some combinations, the tested compounds acted in synergy to lower the susceptibility of S. aureus, S. epidermidis and L. monocytogenes to ampicillin and oxacillin, but no synergy was observed for P. aeruginosa. These results indicate that OA and UA may be useful when administered in combination with β-lactam antibiotics to combat bacterial infections caused by some Gram-positive pathogens.     

Synthesis and activities of naphthalimide azoles as a new type of antibacterial and antifungal agents

Naphthalimide-derived azoles as a new type of antimicrobial agents were synthesized and evaluated for their efficiency in vitro against eight bacteria and two fungi by two fold serial dilution technique. Most title compounds exhibited good antimicrobial potency with low MIC values ranging from 1 to 16 μg/mL. Notably, some synthesized compounds displayed comparable or even better antibacterial and antifungal activities against some tested strains than the reference drugs Orbifloxacin, Chloromycin and Fluconazole, respectively.     

Design, synthesis and antibacterial activity of novel 1,3-thiazolidine pyrimidine nucleoside analogues

The synthesis of a new class of 1,3-thiazolidine nucleoside analogues in which furanose oxygen atom was replaced with nitrogen atom and 2'-carbon atom with sulfur atom is described. N-tert-butoxycarbonyl-2-acyloxy-4-trityloxymethyl-1,3-thiazolidine was coupled with the pyrimidine bases like uracil, thymine, etc. in the presence of lewis acids stannic chloride or trimethyl silyl triflate following Vorbruggen procedure. The antibacterial activity of the novel 1,3-thiazolidine pyrimidine nucleoside analogues is highlighted. All compounds (7a-e) with free NH group in the pyrimidine moiety showed significant biological activity against all the standard strains used and in that compounds 7d and 7e showed significant activity against 14 human pathogens tested.     

Solute Size Effects on the Diffusion in Biofilms of Streptococcus mutans

The diffusion of poly(ethylene glycol) (PEG) (MW varying between 200 and 10,000), and of three different types of micelles was examined in Streptococcus mutans biofilms using infrared spectroscopy. PEGs were used because they show limited interactions with biological materials and their weight can be selected in order to cover a wide range of size. The study showed that a considerable fraction at the base of the biofilm was not accessible to the diffusing solute molecules and this inaccessible fraction was very dependent on the size of the diffusing molecules. In parallel, it was found that the diffusion coefficients of these solutes in the biofilms were less than those in water and this reduction was less pronounced for large macromolecules, an effect proposed to be related to their limited penetration. Triton X-100, a neutral detergent, forms micelles that behave like PEG, suggesting that the behaviour observed for neutral macromolecules can be extrapolated to neutral macroassemblies. However, the diffusion, as well as the penetration of sodium dodecylsulphate micelles (a negatively charged surfactant) and cetylpyridinium chloride micelles (positively charged), in the biofilms appeared to be significantly influenced by electrostatic interactions with biofilm components. The present findings provide useful insights associated with the molecular parameters required to efficiently penetrate bacterial biofilms. The study suggests a rationale for the limited bactericidal power of some antibiotics (the large ones). The restricted accessibility of macromolecules and macroassemblies to biofilms must be examined carefully in order to offer guidelines in the development of novel antibacterial treatments.     

Antibacterial activity against β- lactamase producing Methicillin and Ampicillin-resistants Staphylococcus aureus: fractional Inhibitory Concentration Index (FICI) determination

Background

The present study reports the antibacterial capacity of alkaloid compounds in combination with Methicillin and Ampicillin-resistants bacteria isolated from clinical samples. The resistance of different bacteria strains to the current antibacterial agents, their toxicity and the cost of the treatment have led to the development of natural products against the bacteria resistant infections when applied in combination with conventional antimicrobial drugs.

Method

The antibacterial assays in this study were performed by using inhibition zone diameters, MIC, MBC methods, the time-kill assay and the Fractional Inhibitory Concentration Index (FICI) determination. On the whole, fifteen Gram-positive bacterial strains (MRSA/ARSA) were used. Negative control was prepared using discs impregnated with 10 % DMSO in water and commercially available Methicillin and Ampicillin from Alkom Laboratories LTD were used as positive reference standards for all bacterial strains.

Results

We noticed that the highest activities were founded with the combination of alkaloid compounds and conventional antibiotics against all bacteria strains. Then, results showed that after 7 h exposition there was no viable microorganism in the initial inoculums.

Conclusion

The results of this study showed that alkaloid compounds in combination with conventional antibiotics (Methicillin, Ampicillin) exhibited antimicrobial effects against microorganisms tested. These results validate the ethno-botanical use of Cienfuegosia digitata Cav. (Malvaceae) in Burkina Faso. Moreover, this study demonstrates the potential of this herbaceous as a source of antibacterial agent that could be effectively used for future health care purposes.     

Preliminary evaluation of antimicrobial activity of diastereomeric cis/trans-3-aryl(heteroaryl)-3,4-dihydroisocoumarin-4-carboxylic acids

Preliminary differentiating screening of the antibacterial and antifungal activity of a series of diastereomeric cis/trans-3-aryl(heteroaryl)-3,4-dihydroisocoumarin-4-carboxylic acids (3a-i) was performed by the agar diffusion method against twelve microorganism strains of different taxonomic groups. S. aureus and A. niger were the most sensitive strains to the antibiotic effect of the tested compounds, both inhibited by 10 of 12 compounds. The most potent antibacterial agent was cis-3-phenyl-3,4-dihydroisocoumarin-4-carboxylic acid (cis-3a), exhibiting activity against all seven bacterial test strains.