Comparison of the Phytochemical Composition and Antibacterial Activities of the Various Extracts from Leaves and Twigs of Illicium verum.

Previous studies have revealed the numerous biological activities of the fruits of Illicium verum; however, the activities of its leaves and twigs have remained undiscovered. The study aimed to investigate the phytochemical components and antibacterial activity of the various extracts from the leaves and twigs of Illicium verum. The herbal extracts were prepared by supercritical CO2 extraction (SFE) and 95% ethanol extraction, followed by partition extraction based on solvent polarity. Analysis of antimicrobial activity was conducted through the usage of nine clinical antibiotic- resistant isolates, including Staphylococcus aureus, Pseudomonas aeruginosa and Acinetobacter baumannii. Among the tested samples, the SFE extracts exhibited broader and stronger antibacterial activities against the test strains, with a range of MIC between 0.1-4.0 mg/mL and MBC between 0.2-4.5 mg/mL. Observations made through scanning electron microscopy revealed potential mechanism of the antimicrobial activities involved disruption of membrane integrity of the test pathogens. Evaluation of the chemical composition by gas chromatography-mass spectrometry indicated the presence of anethole, anisyl aldehyde, anisyl acetone and anisyl alcohol within the SFE extracts, demonstrating significant correlations with the antibacterial activities observed. Therefore, the leaves and twigs of Illicium verum hold great potential in being developed as new natural antibacterial agents.

Glycyrrhizin Use for Multi-Drug Resistant Pseudomonas aeruginosa: In Vitro and In Vivo Studies.

Purpose: Our purpose was to test glycyrrhizin (GLY) effects and ciprofloxacin interactions on multidrug resistant (MDR) isolates of Pseudomonas aeruginosa in vitro and in vivo in a mouse model of keratitis. Methods: A Hardy-disk tested antibiotic sensitivity of isolates MDR9 (nonocular) and B1045 (ocular). GLY MIC (both isolates) and ciprofloxacin was determined spectrophotometrically. A live/dead assay using confocal microscopy and plate count, tested GLY effects on bacterial permeabilization/viability. Proteomics profiled bacterial efflux pumps (MDR9 vs. PAO1); RT-PCR comparatively tested GLY effects on their mRNA expression levels. The activity of efflux pumps was tested using ethidium bromide (EB); and scanning electron microscopy (SEM) visualized the effects of GLY treatment of bacteria. A combination of GLY and ciprofloxacin was tested in C57BL/6 mice (begun 18 hours after infection) and disease scored, photographed and MPO and plate counts done. Results: MDR9 was resistant to 6/12 and B1045 to 7/12 antibiotics (both to ciprofloxacin). MIC GLY for MDR9 was 40 mg/mL and 15 mg/mL for B1045. Ciprofloxacin MIC (32 µg/mL) was reduced 2-fold to 16 µg/mL when ciprofloxacin and GLY were combined. GLY altered bacterial membrane permeability and reduced viability. Proteomics revealed increased efflux pumps in MDR9 versus PAO1; GLY reduced their mRNA expression levels and EB suggested decreased activity. In C57BL/6 mice, treatment with GLY and ciprofloxacin versus ciprofloxacin, significantly reduced clinical scores, plate count, and MPO. Conclusions: GLY decreases MDR by: altering bacterial parameters, including viability and efflux pump activity. In vivo, it increases the effectiveness of ciprofloxacin, reducing ocular disease, plate count, and MPO activity.

Photothermal-Induced Antibacterial Activity of Gold Nanorods Loaded into Polymeric Hydrogel against Pseudomonas aeruginosa Biofilm.

In this study, the photothermal-induced bactericidal activity of phospholipid-decorated gold nanorods (DSPE-AuNR) suspension against Pseudomonas aeruginosa planktonic and biofilm cultures was investigated. We found that the treatment of planktonic culture of Pseudomonas aeruginosa with DSPE-AuNR suspension (0.25-0.03 nM) followed by a continuous laser beam exposure resulted in ~6 log cycle reduction of the bacterial viable count in comparison to the control. The percentage reduction of Pseudomonas aeruginosa biofilm viable count was ~2.5-6.0 log cycle upon laser excitation with different concentrations of DSPE-AuNR as compared to the control. The photothermal ablation activity of DSPE-AuNR (0.125 nM) loaded into poloxamer 407 hydrogel against Pseudomonas aeruginosa biofilm resulted in ~4.5-5 log cycle reduction in the biofilm viable count compared to the control. Moreover, transmission electron microscope (TEM) images of the photothermally-treated bacteria revealed a significant change in the bacterial shape and lysis of the bacterial cell membrane in comparison to the untreated bacteria. Furthermore, the results revealed that continuous and pulse laser beam modes effected a comparable photothermal-induced bactericidal activity. Therefore, it can be concluded that phospholipid-coated gold nanorods present a promising nanoplatform to eradicate Pseudomonas aeruginosa biofilm responsible for common skin diseases.

Comparative in situ ROS mediated killing of bacteria with bulk analogue, Eucalyptus leaf extract (ELE)-capped and bare surface copper oxide nanoparticles.

This study demonstrates a simple one-pot green method for biosynthesis of terpenoids encapsulated copper oxide nanoparticles (CuONPs) using aqueous leaf extract of Eucalyptus globulus (ELE), as reducing, dispersing, and stabilizing agent. Indeed, the greater attachment and internalization of ELE-CuONPs in Gram-positive and -negative biofilm producing clinical bacterial isolates validated the hypothesis that terpenoids encapsulated CuONPs are more stable and effective antibacterial and antibiofilm agent vis-à-vis commercially available nano and micro sized analogues. Gas chromatography-mass spectroscopy (GC-MS) analysis of pristine ELE identified 17 types of terpenoids based on their mass-to-charge (m/z) ratios. Amongst them four bioactive terpenoids viz. terpineols, 2,6-octadienal-3,7-dimethyl, benzamidophenyl-4-benzoate and ß-eudesmol were found associated with the CuONPs as ELE-cap, and most likely involved in the nucleation and stabilization of ELE-CuONPs. Further, the Fourier transformed infrared (FTIR) analysis of ELE-CuONPs also implicated other functional biomolecules like proteins, sugars, alkenes, etc. with ELE terpenoids corona. Flow cytometric (FCM) data exhibited significantly enhanced intracellular uptake propensity of terpenoids encapsulated ELE-CuONPs and accumulation of intracellular reactive oxygen species (ROS), which ensued killing of planktonic cells of extended spectrum ß-lactamases (ESßL) producing Escherichia coli-336 (E. coli-336), Pseudomonas aeruginosa-621 (P. aeruginosa-621) and methicillin-resistant Staphylococcus aureus-1 (MRSA-1) clinical isolates compared to the bare surface commercial nano-CuO and bulk sized CuO. The study for the first-time demonstrated the (i) differential bio-nano interface activities due to ELE surface and varied cell wall composition of test bacterial isolates, (ii) antibacterial effect and biofilm inhibition due to disruption of proteins involved in adhesion and biofilm formation triggered by CuONPs induced intracellular oxidative stress, and (iii) indigenous terpenoids-capped bio-inspired CuONPs are more stable and effective antibacterial and antibiofilm agent as compared with commercially available nano-CuO and bulk-CuO.

Application of tungsten disulfide quantum dot-conjugated antimicrobial peptides in bio-imaging and antimicrobial therapy.

Two-dimensional (2D) tungsten disulfide (WS2) quantum dots offer numerous promising applications in materials and optoelectronic sciences. Additionally, the catalytic and photoluminescence properties of ultra-small WS2 nanoparticles are of potential interest in biomedical sciences. Addressing the use of WS2 in the context of infection, the present study describes the conjugation of two potent antimicrobial peptides with WS2 quantum dots, as well as the application of the resulting conjugates in antimicrobial therapy and bioimaging. In doing so, we determined the three-dimensional solution structure of the quantum dot-conjugated antimicrobial peptide by a series of high-resolution nuclear magnetic resonance (NMR) techniques, correlating this to the disruption of both model lipid and bacterial membranes, and to several key biological performances, including antimicrobial and anti-biofilm effects, as well as cell toxicity. The results demonstrate that particle conjugation enhances the antimicrobial and anti-biofilm potency of these peptides, effects inferred to be due to multi-dendate interactions for the conjugated peptides. As such, our study provides information on the mode-of-action of such conjugates, laying the foundation for their potential use in treatment and monitoring of infections.

Crataeva nurvala nanoparticles inhibit virulence factors and biofilm formation in clinical isolates of Pseudomonas aeruginosa.

Green synthesized nanoparticles have gained great attention due to their non-toxic and non-hazardous nature. In the present study, bark extract of the medicinal plant in Ayurveda Crataeva nurvala (Buch-Ham) (CN) was chosen for the biosynthesis of silver nanoparticles (AgNPs). These NPs were characterized by Ultra violet visible spectroscopy, Fourier Transform Infra Red, Atomic Force Microscopy, and Transmission Electron Microscopy (TEM). The average particle size of green synthesized CN-AgNPs was 15.2 ± 1.01 nm. Gas chromatography- mass spectrometry analysis of methanolic bark extract involved in the formation of CN-AgNPs revealed lupeol as a major active component. In this study, CN-AgNPs (15 µg ml-1 ) efficiently suppressed the production of quorum sensing mediated virulence factors viz. pyocyanin, protease, hemolysin, and biofilm formation in Pseudomonas aeruginosa. The pyocyanin production was strongly inhibited (74.64%) followed by proteolysis (47.3%) and hemolysin production (47.7%). However, the biofilm forming ability was maximally reduced up to 79.70%. Moreover, the Confocal Laser Scanning Microscopic Analysis showed that CN-AgNPs inhibit colonization of P. aeruginosa on to the surface. Furthermore, TEM analysis revealed internalization of CN-AgNPs inside the bacterial cell. It is concluded that green synthesized AgNPs have great potential to inhibit virulence factors and biofilm forming ability of drug-resistant clinical isolates of P. aeruginosa.

In vitro and in vivo antimicrobial activity of combined therapy of silver nanoparticles and visible blue light against Pseudomonas aeruginosa.

Silver nanoparticles (AgNPs) have been used as potential antimicrobial agents against resistant pathogens. We investigated the possible therapeutic use of AgNPs in combination with visible blue light against a multidrug resistant clinical isolate of Pseudomonas aeruginosa in vitro and in vivo. The antibacterial activity of AgNPs against P. aeruginosa (1×10(5) colony forming unit/mL) was investigated at its minimal inhibitory concentration (MIC) and sub-MIC, alone and in combination with blue light at 460 nm and 250 mW for 2 hours. The effect of this combined therapy on the treated bacteria was then visualized using transmission electron microscope. The therapy was also assessed in the prevention of biofilm formation by P. aeruginosa on AgNP-impregnated gelatin biopolymer discs. Further, in vivo investigations were performed to evaluate the efficacy of the combined therapy to prevent burn-wound colonization and sepsis in mice and, finally, to treat a real infected horse with antibiotic-unresponsive chronic wound. The antimicrobial activity of AgNPs and visible blue light was significantly enhanced (P<0.001) when both agents were combined compared to each agent alone when AgNPs were tested at MIC, 1/2, or 1/4 MIC. Transmission electron microscope showed significant damage to the cells that were treated with the combined therapy compared to other cells that received either the AgNPs or blue light. In addition, the combined treatment significantly (P<0.001) inhibited biofilm formation by P. aeruginosa on gelatin discs compared to each agent individually. Finally, the combined therapy effectively treated a horse suffering from a chronic wound caused by mixed infection, where signs of improvement were observed after 1 week, and the wound completely healed after 4 weeks. To our knowledge, this combinatorial therapy has not been investigated before. It was proved efficient and promising in managing infections caused by multidrug resistant bacteria and could be used as an alternative to conventional antibiotic therapy.

Effects of hyperbaric oxygen on Pseudomonas aeruginosa susceptibility to imipenem and macrophages.

BACKGROUND: The seriousness to treat burn wounds infected with Pseudomonas aeruginosa led us to examine whether the effect of the carbapenem antibiotic imipenem is enhanced by hyperbaric oxygen (HBO). MATERIALS & METHODS: The effects of HBO (100% O2, 3 ATA, 5 h) in combination with imipenen on bacterial counts of six isolates of P. aeruginosa and bacterial ultrastructure were investigated. Infected macrophages were exposed to HBO (100% O2, 3 ATA, 90 min) and the production of reactive oxygen species monitored. RESULTS: HBO enhanced the effects of imipenen. HBO increased superoxide anion production by macrophages and likely kills bacteria by oxidative mechanisms. CONCLUSION: HBO in combination with imipenem can be used to kill P. aeruginosa in vitro and such treatment may be beneficial for the patients with injuries containing the P. aeruginosa.

Development of antimicrobial biomaterials produced from chitin-nanofiber sheet/silver nanoparticle composites.

BACKGROUND: Chitin nanofibers sheets (CNFSs) with nanoscale fiber-like surface structures are nontoxic and biodegradable biomaterials with large surface-to-mass ratio. CNFSs are widely applied as biomedical materials such as a functional wound dressing. This study aimed to develop antimicrobial biomaterials made up of CNFS-immobilized silver nanoparticles (CNFS/Ag NPs). MATERIALS AND METHODS: CNFSs were immersed in suspensions of Ag NPs (5.17 ± 1.9 nm in diameter; mean ± SD) for 30 min at room temperature to produce CNFS/Ag NPs. CNFS/Ag NPs were characterized by transmission electron microscopy (TEM) and then tested for antimicrobial activities against Escherichia (E.) coli, Pseudomonas (P.) aeruginosa, and H1N1 influenza A virus, three pathogens that represent the most widespread infectious bacteria and viruses. Ultrathin sectioning of bacterial cells also was carried out to observe the bactericidal mechanism of Ag NPs. RESULTS: The TEM images indicated that the Ag NPs are dispersed and tightly adsorbed onto CNFSs. Although CNFSs alone have only weak antimicrobial activity, CNFS/Ag NPs showed much stronger antimicrobial properties against E. coli, P. aeruginosa, and influenza A virus, with the amount of immobilized Ag NPs onto CNFSs. CONCLUSIONS: Our results suggest that CNFS/Ag NPs interacting with those microbes exhibit stronger antimicrobial activities, and that it is possible to apply CNFS/Ag NPs as anti-virus sheets as well as anti-infectious wound dressings.

Multilayered coating on titanium for controlled release of antimicrobial peptides for the prevention of implant-associated infections.

Prevention of bacterial colonization and formation of a bacterial biofilm on implant surfaces has been a challenge in orthopaedic surgery. The treatment of implant-associated infections with conventional antibiotics has become more complicated by the emergence of multi-drug resistant bacteria. Antimicrobial eluting coatings on implants is one of the most promising strategies that have been attempted. This study reports a controlled release of an antimicrobial peptide (AMP) from titanium surface through a non-cytotoxic multilayered coating. Three layers of vertically oriented TiO2 nanotubes, a thin layer of calcium phosphate coating and a phospholipid (POPC) film were impregnated with a potent broad-spectrum AMP (HHC-36). The coating with controlled and sustained release of AMP was highly effective against both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria. No cytotoxicity to osteoblast-like cells (MG-63) was observed. Moderate platelet activation and adhesion on the implant surface with no observable activation in solution, and very low red blood cell lysis was observed on the implant. This multi-layer assembly can be a potential approach to locally deliver AMPs to prevent peri-implant infection in orthopaedics without being toxic to host cells.

An effective antibiofilm agent against Pseudomonas aeruginosa biofilm from traditional Thai herbal recipes used for wound treatments.

The presence of bacterial biofilm, particularly formed by Pseudomonas aeruginosa, has been considered an important factor responsible for wound chronicity. The objective of this study was to investigate the antibiofilm activity of water and ethanol extracts obtained from three traditional herbal recipes (THR-SK004, THR-SK010, and THR-SK011) on biofilm formation and on mature biofilm of a reference strain of P. aeruginosa. The effects of the extracts on the biofilm mass were evaluated by using crystal violet (CV) assay. The respiratory activity of preformed biofilm of P. aeruginosa after treatment with the extract was determined by MTT reduction assay. Scanning electron microscopy was used to furnish images of biofilm reduction after the recipe treatment. Tested ethanol extracts displayed antibiofilm activity, but the water extracts exhibited low biofilm inhibition activity at the tested concentrations. Remarkable reduction in biofilm formation of P. aeruginosa was found after treatment with the THR-SK010 ethanol extract (THR-SK010E). Treatments with this extract resulted in prevention of biofilm formation of P. aeruginosa on both polystyrene and glass surfaces. Almost 50% reduction in the bacterial metabolic activity in the preformed biofilm was seen after exposure to the extract-supplemented buffer for 12 hr. After a 24-hr treatment with THR-SK010E at 62.5 µg/ml, 97.3% of the preformed biofilms were destroyed. Promising antibiofilm activity was displayed by the THR-SK010 ethanol extract, suggesting further investigation to explore the possible utilization of the herbal recipe as an antibiofilm agent, especially for wound treatment.

Tea polyphenols inhibit Pseudomonas aeruginosa through damage to the cell membrane.

This paper aims to delineate the inhibition mechanism of tea polyphenols (TP) toward Pseudomonas aeruginosa by cell membrane damage. Morphological changes in bacteria treated with TP were investigated by transmission electron microscopy, with results indicating that the primary inhibitory action of TP is to damage bacterial cell membranes. TP also increased the permeability of the outer and inner membranes of P. aeruginosa and disrupted the cell membrane with the release of small cellular molecules. A proteomics approach based on two-dimensional gel electrophoresis and MALDI-TOF/TOF MS analysis was used to study the differences in the membrane proteins of TP-treated P. aeruginosa and those of control samples. Twenty-seven differentially expressed proteins were observed in the treated and the control groups. Most of the proteins identified by MALDI-TOF/TOF MS were enzymes (dihdrollpoamide dehydrogenase 50s ribosomal protein, and so on), which may have induced the metabolic disorder of the bacteria and resulted in their death.

Antibacterial activity and morphological changes of Pseudomonas aeruginosa cells after exposure to Vernonia cinerea extract.

The antibacterial activity of Vernonia cinerea (L.) extract was investigated using the broth dilution method. The extract showed a favorable antimicrobial activity against Pseudomonas aeruginosa with a minimum inhibition concentration (MIC) value of 3.13 mg/mL. V. cinerea extract at (1/2), 1, or 2 times the MIC significantly inhibited bacterial growth with a noticeable drop in optical density (OD) of the bacterial culture, thus confirming the antibacterial activity of the extract on P. aeruginosa. Imaging using scanning (SEM) and transmission (TEM) electron microscopy was done to determine the major alterations in the microstructure of the extract-treated P. aeruginosa. The main abnormalities noted via SEM and TEM studies were the alteration in morphology of the bacterial cells. The main reason for this destruction was the severe alterations of the cell wall with the formation of holes, invaginations, and morphological disorganization caused by the extract. The authors conclude that the extract may be used as a candidate for the development of antimicrobial agents.

Purification and identification of antibacterial phenolics from Tripodanthus acutifolius leaves.

AIMS: To perform an activity-guided purification, identification and quantification of antibacterial compounds from Tripodanthus acutifolius infusion. To validate the antibacterial activity of purified substances. METHODS AND RESULTS: Bioautographic methods were employed as screening assays for purifying bioactive substances. Purification procedures included sephadex LH-20 column chromatography and reverse phase HPLC. Identification was achieved by spectroscopic methods (UV-Vis, MS, NMR and polarimetry) and chromatographic assays (paper chromatography and HPLC). Antibacterial activity was studied by microdilution, colony count and photometric assays, Sytox green stain and transmission electron microscopy (TEM). Four glycoflavonoids (rutin, nicotiflorin, hyperoside and isoquercitrin) and an unusual phenylbutanoid glycoside (tripodantoside) were purified and identified. Tripodantoside was found at 6.59 +/- 0.82 g per 100 g of dry leaves. The flavonoids showed bactericidal effect at a concentration of 4 mg ml(-1) against Staphylococcus aureus and Pseudomonas aeruginosa strains from American Type Culture Collection, while tripodantoside was almost four times more active than those compounds, with a minimum bactericidal concentration = 1.024 mg ml(-1) against these strains. Tripodantoside aglycone showed bacteriolytic effects on the assayed strains, causing evident damages on cell wall and membrane, while tripodantoside did not exhibit those effects. CONCLUSIONS: The antibacterial activity of T. acutifolius infusion would be partially attributed to the purified glycoflavonoids and mainly to tripodantoside. SIGNIFICANCE AND IMPACT: The high extraction yield and the antibacterial activity exhibited by tripodantoside makes this chemical structure of interest to support further studies dealing with chemical modifications to increase the antibacterial activity or to seek another activities.

Effects of combined treatment with sansanmycin and macrolides on Pseudomonas aeruginosa and formation of biofilm.

OBJECTIVE: To observe the effects of combined treatment with sansanmycin and macrolides on Pseudomonas aeruginosa and formation of biofilm. METHODS: Micro-dilution method was used to determine the minimal inhibitory concentrations (MICs) of sansanmycin, gentamycin, carbenicillin, polymyxin B, roxithromycin, piperacillin, and tazobactam. PA1 and PA27853 biofilms were observed under optical microscope after staining and under SEM after treatment with sansanmycin at different dosages and combined treatment with sansanmycin and roxithromycin. Viable bacteria in PA1 and PA27853 biofilms were counted after treatment with sansanmycin at different dosages or combined treatment with sansanmycin and roxithromycin. RESULTS: The MIC of sansanmycin was lower than that of gentamycin and polymyxin B, but was higher than that of carbenicillin. Roxithromycin enhanced the penetration of sansanmycin to PA1 and PA27853 strains through biofilms. PA1 and PA27853 biofilms were gradually cleared with the increased dosages of sansanmycin or with the combined sansanmycin and roxithromycin. CONCLUSION: Sub-MIC levels of roxithromycin and sansanmycin substantially inhibit the generation of biofilms and proliferation of bacteria. Therefore, combined antibiotics can be used in treatment of intractable bacterial infection.

Investigation of functional and morphological changes in Pseudomonas aeruginosa and Staphylococcus aureus cells induced by Origanum compactum essential oil.

AIMS: Evaluation of the cellular effects of Origanum compactum essential oil on Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213. METHODS AND RESULTS: The damage induced by O. compactum essential oil on these two strains has been studied using different techniques: plate count, potassium leakage, flow cytometry (FC) and transmission electron microscopy (TEM). The results showed that oil treatment led to reduction of cells viability and dissipated potassium ion gradients. Flow cytometric analysis showed that oil treatment promoted the accumulation of bis-oxonol and the membrane-impermeable nucleic acid stain propidium iodide (PI), indicating the loss of membrane potential and permeability. The ability to reduce 5-cyano-2,3-ditolyl tetrazolium chloride was inhibited. Unlike in Ps. aeruginosa, membrane potential and membrane permeability in Staph. aureus cells were affected by oil concentration and contact time. Finally, TEM showed various structural effects. Mesosome-like structures were seen in oil-treated Staph. aureus cells whereas in Ps. aeruginosa, coagulated cytoplasmic material and liberation of membrane vesicles were observed, and intracellular material was seen in the surrounding environment. Both FC and TEM revealed that the effects in Ps. aeruginosa were greater than in Staph. aureus. CONCLUSIONS: Oregano essential oil induces membrane damage showed by the leakage of potassium and uptake of PI and bis-oxonol. Ultrastructural alterations and the loss of cell viability were observed. SIGNIFICANCE AND IMPACT OF THE STUDY: Understanding the mode of antibacterial effect of the oil studied is of a great interest in it further application as natural preservative in food or pharmaceutical industries.

Membrane-targeted synergistic activity of docosahexaenoic acid and lysozyme against Pseudomonas aeruginosa.

Antimicrobial polypeptides, including lysozymes, have membrane perturbing activity and are well-documented effector molecules of innate immunity. In cystic fibrosis, a hereditary disease with frequent lung infection with Pseudomonas aeruginosa, the non-esterified fatty acid DA (docosahexaenoic acid), but not OA (oleic acid), is decreased, and DA supplementation has been shown to improve the clinical condition in these patients. We hypothesized that DA may, either alone or in conjunction with lysozyme, exert antibacterial action against Ps. aeruginosa. We found that DA and lysozyme synergistically inhibit the metabolic activity of Ps. aeruginosa, in contrast with OA. Electron microscopy and equilibrium dialysis suggest that DA accumulates in the bacterial membrane in the presence of lysozyme. Surface plasmon resonance with live bacteria and differential scanning calorimetry studies with bacterial model membranes reveal that, initially, DA facilitates lysozyme incorporation into the membrane, which in turn allows influx of more DA, leading to bacterial cell death. The present study elucidates a molecular basis for the synergistic action of non-esterified fatty acids and antimicrobial polypeptides, which may be dysfunctional in cystic fibrosis.

Palm oil utilization for the simultaneous production of polyhydroxyalkanoates and rhamnolipids by Pseudomonas aeruginosa.

Direct utilization of palm oil for the simultaneous production of polyhydroxyalkanoates (PHAs) and rhamnolipids was demonstrated using Pseudomonas aeruginosa IFO3924. By secreted lipase, palm oil was hydrolyzed into glycerol and fatty acids. Fatty acids became favorable carbon sources for cell growth and PHA production via beta-oxidation and glycerol for rhamnolipid production via de novo fatty acid synthesis. Both PHA and rhamnolipid syntheses started after the nitrogen source was exhausted and cell growth ceased. PHA synthesis continued until all fatty acids were exhausted, and at that time, PHA content in the cells reached a maximum, but stopped despite the remaining glycerol (<2g/l). In contrast, rhamnolipid synthesis continued until glycerol was exhausted.

Screening antimicrobial activity of various extracts of Artemisia dracunculus L.

The antimicrobial activities of chloroform, acetone and two different concentrations of methanol extracts of Artemisia dracunculus L. were studied. These extracts were tested against nine bacteria and four yeasts strains by the disc diffusion method. The results indicated that the methanol extract of A. dracunculus is more effective against tested microorganisms than chloroform or acetone extracts. The chloroform and acetone extracts were inhibitory only towards Pseudomonas aeruginosa (ATCC 27853). While the methanol extract that was diluted with 10 ml distilled water showed inhibition zones against Shigella (RSHI), Listeria monocytogenes ATCC 7644, P. aeruginosa (ATCC 27853), the methanol extract that was diluted with 5 ml distilled water showed inhibition zones against two different strains of Escherichia coli (RSHI, ATCC 25922), Shigella (RSHI), L. monocytogenes (ATCC 7644), and P. aeruginosa ATCC 27853. The cells of microorganisms treated with plant extracts and normal microorganism cells were observed by scanning electron microscope. It was apparent that cells are damaged after treatment with A. dracunculus.

Tolerance of Pseudomonas aeruginosa to Melaleuca alternifolia (tea tree) oil is associated with the outer membrane and energy-dependent cellular processes.

OBJECTIVES: The essential oil of Melaleuca alternifolia (tea tree oil) and its components have antimicrobial activity against a wide range of Gram-positive and Gram-negative bacteria, fungi and viruses. The mechanism(s) by which Pseudomonas aeruginosa NCTC 10662 maintains a decreased susceptibility to tea tree oil and components was investigated. RESULTS: Ethylene diamine tetraacetic acid enhanced the antimicrobial activity of tea tree oil and terpinen-4-ol against stationary phase P. aeruginosa while polymyxin B nonapeptide enhanced the activity of tea tree oil and gamma-terpinene. Pre-treatment with the protonophore carbonyl cyanide m-chlorophenylhydrazone increased the susceptibility of exponential phase cells to sub-inhibitory concentrations of tea tree oil, terpinen-4-ol and gamma-terpinene, indicating that intrinsic tolerance to tea tree oil and components is substantially energy dependent. CONCLUSIONS: Increased tolerance to tea tree oil in P. aeruginosa is directly related to the barrier and energy functions of the outer membrane, and may involve efflux systems.