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At least 1,135 records · Page 63Linked to original sources
PubMed2004

Mode of action of an antimicrobial biomaterial for use in hydrocephalus shunts.

OBJECTIVES: Infection remains a major complication of shunting for hydrocephalus. The causative bacteria, mainly staphylococci, gain access to the shunt at operation and colonize the shunt tubing. This leads to biofilm development requiring shunt removal. As there is no clear evidence to support antibiotic prophylaxis, we have developed an impregnated antimicrobial shunt material. This study aimed to elucidate its mode of action in terms of bacterial adherence and killing kinetics. METHODS: Plain and impregnated material, with and without plasma protein conditioning film, were exposed to Staphylococcus epidermidis. Bacterial adherence was determined by scanning electron microscopy, chemiluminescence and culture. Time taken to kill 100% of bacteria (tK(100)) was determined by serial chemiluminescence, culture and the use of differential viability microscopy. RESULTS: The antimicrobial material did not reduce bacterial adherence. However, 100% of attached bacteria were killed in 48-52 h, even in the presence of a conditioning film. CONCLUSIONS: Impregnated antimicrobial material is likely to reduce shunt infection rates significantly without the risks and side effects of systemic antibiotics.

Anti-Infective Agents↗
PubMed2005

An antibacterial surface on dental implants, based on the photocatalytic bactericidal effect.

BACKGROUND: It is well known that the moderately roughened surfaces of dental implants enhance direct bone-implant contact. However, rough implant surfaces, as compared to smooth surfaces, are thought to pose a higher risk of bacterial infection when exposed to the oral cavity. PURPOSE: This study was focused on evaluating the photocatalytic bactericidal effects of anatase titanium dioxide (TiO(2)) on gram-negative anaerobic bacteria known to be associated with periimplantitis. MATERIALS AND METHODS: A film of photocatalytic anatase TiO(2) was added onto the surface of commercially pure titanium disks by plasma source ion implantation (PSII) followed by annealing. The photocatalytic properties of the film were confirmed by the degradation of methylene blue. Actinobacillus actinomycetemcomitans and Fusobacterium nucleatum cells were incubated anaerobically and seeded on the disk. The disks were then exposed to ultraviolet A (UVA) illumination from black light in an anaerobic environment. After illumination, the number of viable cells was counted in terms of colony-forming units. RESULTS: The anatase TiO(2) film added by the PSII method and annealing exhibited a strong photocatalytic reaction under UVA illumination. The viability of both types of bacteria on the photocatalytic TiO(2) film was suppressed to less than 1% under UVA illumination within 120 minutes. CONCLUSION: The bactericidal effect of the TiO(2) photocatalyst is of great use for sterilizing the contaminated surface of dental implants.

Aggregatibacter actinomycetemcomitans↗
PubMed2006

Mycobacterium leprae is naturally resistant to PA-824.

Leprosy responds very slowly to the current multidrug therapy, and hence there is a need for novel drugs with potent bactericidal activity. PA-824 is a 4-nitroimidazo-oxazine that is currently undergoing phase I clinical trials for the treatment of tuberculosis. The activity of PA-824 against Mycobacterium leprae was tested and compared with that of rifampin in axenic cultures, macrophages, and two different animal models. Our results conclusively demonstrate that PA-824 has no effect on the viability of M. leprae in all three models, consistent with the lack of the nitroimidazo-oxazine-specific nitroreductase, encoded by Rv3547 in the M. leprae genome, which is essential for activation of this molecule.

Animals↗
PubMed1993

Antiviral activity of a phosphorothioate oligonucleotide complementary to RNA of the human cytomegalovirus major immediate-early region.

Phosphorothioate oligonucleotides complementary to mRNA of the human cytomegalovirus (HCMV) DNA polymerase gene or to RNA transcripts of the major immediate-early regions 1 and 2 (IE1 and IE2) of HCMV were evaluated for antiviral activity in a 96-well immunoassay with primary human dermal fibroblasts as host cells. Oligonucleotides complementary to RNA of the IE2 region exhibited the most potent antiviral activity. One of these oligonucleotides, ISIS 2922, was at least 30-fold more potent than the nucleoside analog, ganciclovir, with a 50% effective concentration of 0.37 microM in the 96-well immunoassay. In an infectious virus yield reduction assay, ISIS 2922 and ganciclovir reduced production of infectious virus by 2 log units at concentrations of 2.2 and 36 microM, respectively. A control oligonucleotide showed no inhibition of virus production at concentrations as high as 3 microM. ISIS 2922 reduced IE protein synthesis in HCMV-infected cells in a dose-dependent manner which correlated with antiviral activity. The antiviral activity of ISIS 2922 was not due to oligonucleotide-induced cytotoxicity since effects on cell viability or proliferation were observed only at concentrations well in excess of effective antiviral concentrations. The specificity and potency of ISIS 2922 suggest that it may be useful for the treatment of cytomegalovirus disease in humans.

Antiviral Agents↗
PubMedDate not supplied

[Selection of Escherichia coli and Pseudomonas putida cultures with an enhanced resistance to immobilization on polyacrylamide gel].

Clones of Escherichia coli (A4, A70, G60) and Pseudomonas putida (A70, G30) with an elevated resistance to the process of immobilization in polyacrylamide gel and to the action of monomeric acrylamide were selected from the parent E. coli IBPM B115 and P. putida. The isolated cultures remained resistant to the above actions for a long time. The frequency at which cells with the elevated resistance appeared was comparable with the frequency of bacterial mutations. The plasmid analysis did not reveal the presence of plasmid DNA in the cells of the isolated cultures. The decrease in the viability index of bacterial populations caused by their immobilization in polyacrylamide gel and by the action of monomeric acrylamide did depend on the growth phase. The cells were more resistant to these actions in the stationary phase. The isolated cultures were more resistant as compared to the parent cultures irrespective of the growth phase.

Acrylamides↗
PubMed2005

Comparison of four methods to enumerate probiotic bifidobacteria in a fermented food product.

Four methods of enumeration were compared by monitoring levels of probiotic bifidobacteria in fermented oat drink during storage. Strains of Bifidobacterium longum and B. lactis were quantified by plate counts, fluorescent in situ hybridization (FISH), quantitative real-time PCR and commercial LIVE/DEAD BacLight bacterial viability kit, and the methods were further developed to suit the enumeration of bifidobacteria in fermented foods. Plate counts of both B. lactis and B. longum were lower than the PCR and FISH counts. The LIVE/DEAD counts of B. lactis were comparable to PCR and FISH counts. The plate counts of B. lactis were slightly but significantly lower than LIVE/DEAD counts, suggesting that the cells that were not able to grow on plates may have become dormant. The plate counts of B. longum were several log units lower than LIVE/DEAD counts, suggesting that a remarkable part of the cells were dormant. Real-time PCR and FISH were shown to suit the quantification of the total amount of probiotic bifidobacteria in foods. Plate counts and LIVE/DEAD counts provided conflicting information on viability especially in the case of B. longum. We conclude that the choice of enumeration method for probiotic bacteria may have significant effect on the results of the analysis. The strain-specific properties and the objects of the analysis should be taken into account when enumeration methods for different probiotic strains are chosen.

Bifidobacterium↗
PubMed2006

Survival and growth of Aspergillus carbonarius on wine grapes before harvest.

Aspergillus carbonarius, the primary OTA-producing species in Australia, was inoculated onto the surface of Chardonnay and Shiraz bunches at pre-bunch closure, veraison and pre-harvest during the 2002-03 and 2003-04 seasons. Mean A. carbonarius counts decreased between pre-bunch closure and veraison, and increased between veraison and pre-harvest. Increases in A. carbonarius counts from veraison onwards were most marked in Chardonnay bunches during 2003-04; such bunches comprised more berries and were heavier than in 2002-03. Bunches with no berry damage yielded low A. carbonarius counts at pre-harvest and harvest. Exposure to direct sunlight over several days reduced viability of A. carbonarius spores supported on filter membranes by 10(5), despite the spores having thick, heavily melanised walls. The estimated cumulative UV exposure for that period was 10 mWh. Thus, UV radiation may be a contributory factor to the decline of A. carbonarius spores on berry surfaces, particularly in the early stages of berry development.

Aspergillus↗
PubMed2003

Neisseria gonorrhoeae penicillin-binding protein 3 exhibits exceptionally high carboxypeptidase and beta-lactam binding activities.

A soluble form of penicillin-binding protein 3 (PBP 3) from Neisseria gonorrhoeae was expressed and purified from Escherichia coli and characterized for its interaction with beta-lactam antibiotics, its catalytic properties with peptide and peptidoglycan substrates, and its role in cell viability and morphology. PBP 3 had an unusually high k(2)/K' value relative to other PBPs for acylation with penicillin (7.7 x 10(5) M(-1) s(-1)) at pH 8.5 at 25 degrees C and hydrolyzed bound antibiotic very slowly (k(3) < 4.6 x 10(-5) s(-1), t(1/2) > 230 min). PBP 3 also demonstrated exceptionally high carboxypeptidase activity with a k(cat) of 580 s(-1) and a k(cat)/K(m) of 1.8 x 10(5) M(-1) s(-1) with the substrate N(alpha)-Boc-N(epsilon)-Cbz-L-Lys-D-Ala-D-Ala. This is the highest k(cat) value yet reported for a PBP or other serine peptidases. Activity against a approximately D-Ala-D-Lac peptide substrate was approximately 2-fold lower than against the analogous approximately D-Ala-D-Ala peptide substrate, indicating that deacylation is rate determining for both amide and ester hydrolysis. The pH dependence profiles of both carboxypeptidase activity and beta-lactam acylation were bell-shaped with maximal activity at pH 8.0-8.5. PBP 3 displayed weak transpeptidase activity in a model transpeptidase reaction but was active as an endopeptidase, cleaving dimeric peptide cross-links. Deletion of PBP 3 alone had little effect on viability, growth rate, and morphology of N. gonorrhoeae, although deletion of both PBP 3 and PBP 4, the other low-molecular-mass PBP in N. gonorrhoeae, resulted in a decreased growth rate and marked morphological abnormalities.

Acylation↗
PubMed1996

Effect of fluconazole on viability of Candida albicans over extended periods of time.

The treatment of chronic mycoses may expose the infecting organisms to antimicrobial agents for extended periods of time. It is possible that an azole antifungal drug such as fluconazole, with primarily fungistatic activity in standard in vitro susceptibility tests, might be able to damage the fungal cells and reduce their viability over prolonged incubations under nonproliferating conditions. To test this possibility, Candida albicans yeast cells were exposed to various concentrations of fluconazole in RPMI 1640 tissue culture medium for 4 h at 37 degrees C, washed free of the drug, and then incubated at 37 degrees C for a 28-day period; enumeration of the remaining CFU at various times during this period revealed no increased loss of viability for the fluconazole-exposed organisms. However, when fluconazole was added to the organisms maintained in distilled water (with or without pretreatment with the drug), a marked reduction of viability was found. At 14 days of incubation with two strains of C. albicans, negative cultures were found for 7 of 10 and 10 of 11 samples, respectively, containing 1.0 microgram of fluconazole per ml versus 0 of 10 and 1 of 11 control samples (P of < 0.01 and 0.001, respectively). The effect of fluconazole on fungal viability under these conditions became noticeable at approximately 7 days and was greater when the samples were incubated at 37 degrees C rather than 25 degrees C. These findings suggest that fluconazole may have fungicidal effects on fungal cells during prolonged exposures under conditions in which the organisms are prevented from proliferating by lack of nutrients.

Antifungal Agents↗
PubMed1996

In vitro activities of azithromycin and doxycycline against 15 isolates of Chlamydia pneumoniae.

Fourteen isolates of Chlamydia pneumoniae, 12 from clinically ill patients and 2 from subjectively healthy individuals from an area within a 400-km proximity of Gävle, Sweden, and strain IOL-207, originally from the eye of an Iranian child, were tested for susceptibilities to the antibiotics doxycycline and azithromycin. MICs and minimum chlamydiacidal concentrations were found to correlate well with values reported earlier by other investigators. In addition to MIC and minimum chlamydiacidal concentration testing, testing for the viability of C. pneumoniae after exposure to antibiotic concentrations as high as 50 mg/liter was carried out by passaging antibiotic-treated, infected cell cultures four times in the absence of antibiotics. It was found that all Chlamydia strains were viable after four passages, regardless of antibiotic concentration in the cell culture.

Anti-Bacterial Agents↗
PubMed1991

Effects of cytochalasin D and methylamine on intracellular growth of Legionella pneumophila in amoebae and human monocyte-like cells.

A cloned and axenically cultured strain of Hartmannella vermiformis was used as a model to study intracellular multiplication of Legionella pneumophila in amoebae. The growth of L. pneumophilia in both H. vermiformis and a human monocyte-like cell line (U937) was investigated with cytoskeletal and metabolic inhibitors. L. pneumophila replicated only intracellularly in these cellular models, and electron microscopy showed ultrastructural similarities in the initial phase of multiplication. Treatment of amoebae with an inhibitor of microfilament-dependent phagocytosis (cytochalasin D, 0.5 or 1.0 micrograms/ml) did not inhibit intracellular growth of L. pneumophila; however, intracellular multiplication was inhibited by treatment of U937 monocytes with the same concentrations of cytochalasin D. Methylamine (10 to 100 mM), an inhibitor of adsorptive pinocytosis, inhibited the replication of L. pneumophila in amoebae in a dose-dependent manner. All doses of methylamine tested (10 to 50 mM) inhibited growth of L. pneumophila in U937 monocytes. Cytochalasin D and methylamine had no effect on the multiplication of L. pneumophila in culture medium or on the viability of amoebae or U937 monocytes. Intracellular replication of L. pneumophila in H. vermiformis may be accomplished by a cytochalasin D-independent mechanism, such as adsorptive pinocytosis. In contrast, both cytochalasin D- and methylamine-sensitive mechanisms may be essential for the intracellular multiplication of L. pneumophila in U937 monocytes.

Analysis of Variance↗
PubMed2004

Cryopreservation with hydroxyethylstarch (HES) + dimethylsulfoxide (DMSO) gives better results than DMSO alone.

This study compares the cryopreservation of PBSC by means of HES 3% + DMSO 5% ina mechanical freezer with the cryopreservation of PBSC by means of DMSO 10% in an automated rate controlled freezer. The cells harvested from the same patient were divided in two equal parts and frozen according to both methods. Cryopreservation with HES +DMSO is better than DMSO alone in terms of viability (p<0.001) and Granulocyte Macrophage Colony Forming Unit (GM-CFU) activity (p<0.05). The freezing curves differ essentially in the slope down after the surfusion peak. However, surfusion peaks are similar in both conditions. The relevance of mechanical freezing is the saving of time and the safety of such a procedure.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Sensitisation of Candida albicans to killing by low-power laser light.

The purpose of this study was to determine whether Candida albicans, and other Candida spp. responsible for HIV-associated candidosis, could be sensitised to killing by low-power laser light. Suspensions of C. albicans were treated with a number of potential photosensitisers, exposed to laser light from a Helium/Neon (HeNe) or Gallium aluminium arsenide (GaAs) laser for 120 s and survivors enumerated. Toluidine blue O (TBO), thionin and crystal violet were able to sensitise the yeast to killing by light from the HeNe laser (energy dose = 876 mJ at a density of 66.36 J/cm2), the kills achieved being 6.8 x 10(6) cfu/ml, 3.1 x 10(6) cfu/ml and 1.3 x 10(6) cfu/ml respectively. TBO was also able to sensitise several other Candida spp. to killing by HeNe laser light. Dihaematoporphyrin ester was not an effective photosensitiser under the conditions employed. Methylene blue, but not aluminium disulphonated phthalocyanine, was able to sensitise C. albicans to killing by light from the GaAs laser (energy dose 1.32 J at a density of 2.04 J/cm2). The viability of the yeast was not affected by exposure to laser light in the absence of the photosensitisers. As killing of dye-sensitised C. albicans, and other Candida spp., could be achieved by exposure to low-power laser light for short periods of time, this approach merits further investigation as a potential therapeutic modality for HIV-associated candidosis.

Aluminum↗
PubMed2004

Effects on the structure of Arctic ecosystems in the short- and long-term perspectives.

Species individualistic responses to warming and increased UV-B radiation are moderated by the responses of neighbors within communities, and trophic interactions within ecosystems. All of these responses lead to changes in ecosystem structure. Experimental manipulation of environmental factors expected to change at high latitudes showed that summer warming of tundra vegetation has generally led to smaller changes than fertilizer addition. Some of the factors manipulated have strong effects on the structure of Arctic ecosystems but the effects vary regionally, with the greatest response of plant and invertebrate communities being observed at the coldest locations. Arctic invertebrate communities are very likely to respond rapidly to warming whereas microbial biomass and nutrient stocks are more stable. Experimentally enhanced UV-B radiation altered the community composition of gram-negative bacteria and fungi, but not that of plants. Increased plant productivity due to warmer summers may dominate food-web dynamics. Trophic interactions of tundra and sub-Arctic forest plant-based food webs are centered on a few dominant animal species which often have cyclic population fluctuations that lead to extremely high peak abundances in some years. Population cycles of small rodents and insect defoliators such as the autumn moth affect the structure and diversity of tundra and forest-tundra vegetation and the viability of a number of specialist predators and parasites. Ice crusting in warmer winters is likely to reduce the accessibility of plant food to lemmings, while deep snow may protect them from snow-surface predators. In Fennoscandia, there is evidence already for a pronounced shift in small rodent community structure and dynamics that have resulted in a decline of predators that specialize in feeding on small rodents. Climate is also likely to alter the role of insect pests in the birch forest system: warmer winters may increase survival of eggs and expand the range of the insects. Insects that harass reindeer in the summer are also likely to become more widespread, abundant and active during warmer summers while refuges for reindeer/caribou on glaciers and late snow patches will probably disappear.

Animals↗
PubMed1995

Minocycline in lepromatous leprosy.

Twelve patients were treated with three dose levels of minocycline for 30 days, primarily to detect the dose-related effects on Mycobacterium leprae viability, followed by another 5 months of daily minocycline for overall efficacy and persistence of clinical and antibacterial effects. Subsequently, the patients were given standard WHO/MDT chemotherapy for multibacillary leprosy. Clinical improvement was recognizable during the first month, occurring much earlier among those on minocycline 200 mg daily than those who received minocycline 100 mg daily. A similar change also was observed in one patient 11 days after three daily doses of 100 mg of minocycline. At the end of 6 months, all patients were clinically improved with a slight reduction in the average bacterial index (BI) and logarithmic index of bacilli in biopsy (LIB). The effects of minocycline on viability by mouse foot pad inoculation and palmitic acid oxidation assays were noted beginning at 10 to 14 days of daily dosing and becoming more definite after 30 days of treatment. Both tests correlated fairly well. Doses of 200 mg daily did not appear to be more efficient than minocycline 100 daily. Phenolic glycolipid-I (PGL-I) antigen determinations done on some patients during the first month remained positive and did not correlate with changes in viability results. At the end of 6 months, after 5 months of 100 mg of minocycline monotherapy, no viable organisms could be demonstrated by mouse foot pad inoculation and palmitic acid oxidation assays; assays for PGL-I antigen were all negative.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2006

Germanium dioxide induces mitochondria-mediated apoptosis in Neuro-2A cells.

Germanium (Ge) is commonly used in the semiconductor industry as well as health-promoting and medical field. Biologically, germanium possesses erythropoietic, anti-microbial, anti-tumor, anti-amyloidosis, and immunomodulative effects. However, toxic effects of Ge-containing compounds on kidney, muscle, neuronal cells, and nerves have been reported. Mitochondrial dysfunction was found to be involved in the pathogenesis of GeO(2)-induced nephropathy and myopathy. Since it is well known that mitochondria play a major role in apoptosis triggered by many stimuli, an effort was made to examine whether the Ge-induced neurotoxicity occurs through mitochondria-mediated apoptosis. A mouse neuroblastoma cell line, Neuro-2A, was used in the present study. After incubating with 0.1-800microM of GeO(2) for 0-72h, the cell viability of Neuro-2A cells was inhibited in a dose- and time-dependent manner. Further analysis showed that aside from the changes in the nuclear morphology responsible for apoptosis, the release of cytochrome c, the loss of mitochondrial membrane potential, the translocation of Bax, and the reduction of Bcl-2 expression were also observed in Neuro-2A cells after GeO(2) treatment. These results indicate that the mitochondria-mediated apoptosis is involved in this in vitro model of GeO(2)-induced neurotoxicity.

Acridine Orange↗
PubMed2005

Anti-inflammatory activity of verminoside from Kigelia africana and evaluation of cutaneous irritation in cell cultures and reconstituted human epidermis.

Kigelia africana is a plant used in Africa for anti-inflammatory, anti-microbial, and anti-skin-aging effects. Various papers have reported on the composition and biological activities of its CH2Cl2 extracts and dermal formulations. Chemical analysis of a polar extract of fruit from K. africana indicated the presence of verminoside (1), an iridoid, as a major constituent, and of a series of polyphenols such as verbascoside (2). In vitro assays showed that 1 had significant anti-inflammatory effects, inhibiting both iNOS expression and NO release in the LPS-induced J774.A1 macrophage cell line. Cytotoxicity and cutaneous irritation of the extract and of compounds 1 and 2 were investigated. The crude extract and 1 did not affect cell viability in vitro either in cells grown in monolayers (ML) or in the reconstituted human epidermis (RHE, 3D) model; neither caused release of pro-inflammatory mediators or histomorphological modification of RHE.

Animals↗