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PubMed1999

Adhesion and surface-aggregation of Candida albicans from saliva on acrylic surfaces with adhering bacteria as studied in a parallel plate flow chamber.

Adhesive interactions between Candida albicans and oral bacteria are generally thought to play a crucial role in the microbial colonization of denture acrylic, which may lead to denture stomatitis. This study investigated the influence of saliva on the adhesive interactions between C. albicans and Streptococcus sanguis or Actinomyces naeslundii on denture acrylic. First, bacteria were allowed to adhere to the acrylic surface from a flowing suspension, and subsequently yeasts were flowed over the acrylic surface. The organisms were assayed in the presence or absence of human whole saliva. All experiments were carried out in a parallel plate flow chamber and enumeration was done in situ with an image analysis system. In the absence of adhering bacteria, adhesion of C. albicans from buffer was more extensive than from saliva. However, in the presence of adhering bacteria, yeast adhesion from saliva was increased with respect to adhesion of yeasts from buffer, indicating that specific salivary components constitute a bridge between bacteria and yeasts. In all cases, yeast aggregates consisting of 3 to 5 yeast cells were observed adhering to the surface. A surface physico-chemical analysis of the microbial cell surfaces prior to and after bathing the microorganisms in saliva, suggests that this bridging is mediated by acid-base interactions since all strains show a major increase in electron-donating surface free energy parameters upon bathing in saliva, with no change in their zeta potentials. The surface physico-chemical analysis furthermore suggests that S. sanguis and A. naeslundii may use a different mechanism for adhesive interactions with C. albicans in saliva.

Acrylic Resins↗

PubMed2005

Management and control of microbial populations' development in LSS of missions of different durations.

The problem of interaction between man and microorganisms in closed habitats is an inextricable part of the whole problem of co-existence between macro- and microorganisms. Concerning the support of human life in closed habitat, we can, conventionally, divide microorganisms, acting in life support system (LSS) into three groups: useful, neutral and harmful. The tasks, for human beings for optimal coexistence with microhabitants seem to be trivial: (1) to increase the activity of useful forms, (2) decrease the activity harmful forms, (3) not allow the neutral forms to become the harmful ones and even to help them to gain useful activity. The task of efficient management and control of microbial population's development in LSS highly depends on mission duration. As for short-term missions without recycling, the proper hygienic procedures are developed. For longer missions, the probability of transformation of the neutral forms into the harmful ones is becoming more dangerous. The LSS for long-term missions are to use cycling-recycling systems, including system with biological recycling. In these systems, microbial populations as regenerative link should be useful and active agents. Some problems of microbial populations control and management are discussed in the paper.

Aerospace Medicine↗

PubMed1999

Structural Interactions among Epilithic Cyanobacteria and Heterotrophic Microorganisms in Roman Hypogea.

Abstract Phototrophic microbial communities present in the Roman Catacombs were characterized and different species of terrestrial epilithic cyanobacteria were found to occur as dominant organisms. Eucapsis, Leptolyngbya, Scytonema, and Fischerella were the most frequently encountered cyanobacterial taxa, while a few species of green algae and the diatom Diadesmis gallica occurred in minor amounts. Streptomyces strains, a few genera of eubacteria, and to a lesser extent fungi were always present in the same microhabitats and contributed to the deterioration of stone surfaces. The combined use of light and electron microscopy evidenced the structural relationships among rod-shaped or filamentous bacteria and cyanobacterial cells, as well as the presence of polysaccharide capsules and sheaths, and of mineral precipitates on S. julianum filaments. The significance of the intimate association among the microorganisms was discussed in relation to the damage caused by the growth of biological patinas on stone surfaces.http://link.springer-ny.com/link/service/journals/00248/bibs/38n3p244.html</hea

Journal Article↗

PubMed1994

Saperconazole therapy of murine disseminated candidiasis: efficacy and interactions with amphotericin B.

The efficacy of a new triazole antifungal agent, saperconazole, in a murine model of disseminated candidiasis was studied. Mice were intravenously infected with Candida albicans blastoconidia and treated for 14 days with oral saperconazole, intraperitoneal amphotericin B, or a combination of these. Amphotericin B alone was the most efficacious in prolonging survival and in decreasing renal colony counts, usually with complete sterilization of the kidneys by the end of the treatment course. Saperconazole improved survival rates and effected a decrease in renal colony counts, but kidneys were not microbiologically sterilized. Combination therapy with saperconazole and amphotericin B did not result in a decrease in the efficacy of amphotericin B by either end point (survival or renal colony counts). High-pressure liquid chromatographic analysis of saperconazole concentrations in serum indicated low levels of absorption of the drug. We conclude that saperconazole is effective in the treatment of murine invasive candidiasis and that the theoretical concern about adverse interactions between the two drugs does not apply to the dosages studied in these experiments.

Absorption↗

PubMed2006

Application of classification and regression trees for sensitivity analysis of the Escherichia coli O157:H7 food safety process risk model.

Microbial food safety process risk models are simplifications of the real world that help risk managers in their efforts to mitigate food safety risks. An important tool in these risk assessment endeavors is sensitivity analysis, a systematic method used to quantify the effect of changes in input variables on model outputs. In this study, a novel sensitivity analysis method called classification and regression trees was applied to safety risk assessment with the use of portions of the Slaughter Module and Preparation Module of the E. coli O157:H7 microbial food safety process risk as an example. Specifically, the classification and regression trees sensitivity analysis method was evaluated on the basis of its ability to address typical characteristics of microbial food safety process risk models such as nonlinearities, interaction, thresholds, and categorical inputs. Moreover, this method was evaluated with respect to identification of high exposure scenarios and corresponding key inputs and critical limits. The results from the classification and regression trees analysis applied to the Slaughter Module confirmed that the process of chilling carcasses is a critical control point. The method identified a cutoff value of a 2.2-log increase in the number of organisms during chilling as a critical value above which high levels of contamination would be expected. When classification and regression trees analysis was applied to the cooking effects part of the Preparation Module, cooking temperature was found to be the most sensitive input, with precooking treatment (i.e., raw product storage conditions) ranked second in importance. This case study demonstrates the capabilities of classification and regression trees analysis as an alternative to other statistically based sensitivity analysis methods, and one that can readily address specific characteristics that are common in microbial food safety process risk models.

Consumer Product Safety↗

PubMed2006

In-situ nitrogen removal from the eutrophic water by microbial-plant integrated system.

OBJECTIVE: This study was to assess the influence of interaction of combination of immobilized nitrogen cycling bacteria (INCB) with aquatic macrophytes on nitrogen removal from the eutrophic waterbody, and to get insight into different mechanisms involved in nitrogen removal. METHODS: The aquatic macrophytes used include Eichhornia crassipes (summer-autumn floating macrophyte), Elodea nuttallii (winter-growing submerged macrophyte), and nitrogen cycling bacteria including ammonifying, nitrosating, nitrifying and denitrifying bacteria isolated from Taihu Lake. The immobilization carriers materials were made from hydrophilic monomers 2-hydroxyethyl acrylate (HEA) and hydrophobic 2-hydroxyethyl methylacrylate (HEMA). Two experiments were conducted to evaluate the roles of macrophytes combined with INCB on nitrogen removal from eutrophic water during different seasons. RESULTS: Eichhornia crassipes and Elodea nuttallii had different potentials in purification of eutrophic water. Floating macrophyte+bacteria (INCB) performed best in improving water quality (during the first experiment) and decreased total nitrogen (TN) by 70.2%, nitrite and ammonium by 92.2% and 50.9%, respectively, during the experimental period, when water transparency increased from 0.5 m to 1.8 m. When INCB was inoculated into the floating macrophyte system, the populations of nitrosating, nitrifying, and denitrifying bacteria increased by 1 to 2 orders of magnitude compared to the un-inoculated treatments, but ammonifying bacteria showed no obvious difference between different treatments. Lower values of chlorophyll a, COD(Mn), and pH were found in the microbial-plant integrated system, as compared to the control. Highest reduction in N was noted during the treatment with submerged macrophyte+INCB, being 26.1% for TN, 85.2% for nitrite, and 85.2% for ammonium at the end of 2nd experiment. And in the treatment, the populations of ammonifying, nitrosating, nitrifying, and denitrifying bacteria increased by 1 to 3 orders of magnitude, as compared to the un-inoculated treatments. Similar to the first experiment, higher water transparency and lower values of chlorophyll a, COD(Mn) and pH were observed in the plant+ INCB integrated system, as compared to other treatments. These results indicated that plant-microbe interaction showed beneficial effects on N removal from the eutrophic waterbody.

Biodegradation, Environmental↗

PubMed1998

Role of Fusobacterium nucleatum and coaggregation in anaerobe survival in planktonic and biofilm oral microbial communities during aeration.

Coaggregation is a well-characterized phenomenon by which specific pairs of oral bacteria interact physically. The aim of this study was to examine the patterns of coaggregation between obligately anaerobic and oxygen-tolerant species that coexist in a model oral microbial community. Obligate anaerobes other than Fusobacterium nucleatum coaggregated only poorly with oxygen-tolerant species. In contrast, F. nucleatum was able to coaggregate not only with both oxygen-tolerant and other obligately anaerobic species but also with otherwise-noncoaggregating obligate anaerobe-oxygen-tolerant species pairs. The effects of the presence or absence of F. nucleatum on anaerobe survival in both the biofilm and planktonic phases of a complex community of oral bacteria grown in an aerated (gas phase, 200 ml of 5% CO2 in air x min-1) chemostat system were then investigated. In the presence of F. nucleatum, anaerobes persisted in high numbers (>10(7) x ml-1 in the planktonic phase and >10(7) x cm-2 in 4-day biofilms). In an equivalent culture in the absence of F. nucleatum, the numbers of black-pigmented anaerobes (Porphyromonas gingivalis and Prevotella nigrescens) were significantly reduced (P </= 0.001) in both the planktonic phase and in 4-day biofilms, while the numbers of facultatively anaerobic bacteria increased in these communities. Coaggregation-mediated interactions between F. nucleatum and other species facilitated the survival of obligate anaerobes in aerated environments.

Actinomyces↗

PubMed1998

The effects of starch and protein degradation rates, hay sources, and feeding frequency on rumen microbial fermentation in a continuous culture system.

Six continuous culture fermenters were used in three experiments to study the effects of dietary starch and protein degradability combination, hay sources, and feeding frequency on fermentation by rumen microorganisms. Experiments 1 and 2 used a 3 x 2 factorial design in which six diets were formulated to contain low (LS), medium (MS), or high starch degradability (HS) in combination with low (LP) or high protein degradability (HP). The dietary combinations were (1) LS + HP, (2) LS + LP, (3) MS + HP, (4) MS + LP, (5) HS + HP, and (6) HS + LP. In experiment 1, pangola was used as the hay source, and in experiment 2, alfalfa hay was used. In experiment 3, two starch degradabilities (LS, MS) and two hay sources (alfalfa, A; pangola, P) were combined with two feeding frequencies (2 X/d, 12 X/d). The dietary combinations were (1) LS + A + 12 X/d, (2) MS + A + 12 X/d, (3) LS + A + 2 X/d, (4) MS + A + 2 X/d, (5) LS + P + 12 X/d, and (6) MS + P + 12 X/d. A CRD design was used for experiment 3. Two rumen-cannulated Holstein cows fed alfalfa hay ad lib were used as donors of rumen fluid for all experiments. Each period was 6 d in length, with 5 d for adaptation and 1 d for sampling. In experiments 1 and 2, the effects of starch degradability on the composition of rumen microorganisms were significant. The MS or HS with HP had the highest total bacterial and protozoal density (P < 0.05). As for VFA, pH and nitrogen products, the effects of starch and protein degradability were not significant. There was no interaction between starch and protein degradability on most of microbial composition (ammonia-N, microbial nitrogen). In experiment 3, 12 X/d feeding frequency (MS + A + 12 X/d vs. MS + A + 12 X/d) resulted in higher pH, which tended to increase bacterial and protozoal density and starch and protein digestibilities. Different hay sources altered the starch and protein synchronization effect on the ammonia-N concentration (mg/dl) and non-ammonia N content (% DM) in the continuous culture system.

Animal Feed↗

PubMed2004

Penicillin-induced killing and postantibiotic effect in oral streptococci are enhanced by platelet microbicidal proteins.

Thrombin-induced platelet microbicidal proteins (tPMP) are alpha-granule-derived cationic antimicrobial proteins released from platelets by stimulation with thrombin. tPMP has potent microbicidal activities against a broad spectrum of common microbial pathogens in infective endocarditis. We studied in vitro interactions of tPMP with penicillin against oral streptococci, Streptococcus rattus BHT (a tPMP-susceptible organism) and Streptococcus gordonii DL1 (a tPMP-insusceptible organism). tPMP was prepared by stimulating rabbit platelets with thrombin. tPMP plus penicillin showed a synergistic bactericidal effect on both S. rattus BHT and S. gordonii DL1, in contrast to either agent alone. Sequential exposure of both S. rattus BHT and S. gordonii DL1 to tPMP followed by exposure to penicillin at 10x the MICs resulted in a significant extension of the postantibiotic-effect duration compared with antibiotic exposure alone. The combined data indicate that tPMP exerts cooperative bactericidal and growth-inhibiting effect in concert with penicillin.

Animals↗

PubMed2026

Optimizing eco-engineering pedogenesis of bauxite residues: Synergistic effects of humus and FeSO4/sulfur on microbial community and function.

Eco-engineered pedogenesis represents a promising approach for soil amelioration of bauxite residues (BRs) through exogenous organic matter. However, the role of humus in mediating this process remains poorly understood, significantly impeding the eco-engineering rehabilitation of BRs. In this study, we conducted pot experiments and subsequent microbial analysis to evaluate the individual improvement of humic acid (HA), fulvic acid (FA), and corn straw (SWZ) on the BRs' pedogenesis. High-throughput sequencing analysis revealed that both FA and SWZ were more effective than HA in steering microbial community assembly, as community diversity, dominant taxa enrichment, and species' interaction were all significantly higher (p < 0.05) in the FA/SWZ treatments than in HA treatments. Notably, the combination of FA with FeSO4 specifically enriched halophilic taxa, while FA coupled with sulfur (S) significantly improved the connectivity and complexity of the microbial network, as the average connection degree increasing from 1.008 to 1.113. Hydrolytic enzyme activity assays further indicated that FA, especially when combined with S, was the most effective treatment in restoring microbial function during BR pedogenesis. These findings highlight FA as a critical driver of microbial restructuring and functional recovery in BRs. Moreover, its efficacy can be enhanced by co-amendment with FeSO4 or S. This study provides important theoretical and practical insights for optimizing organic-inorganic amendment strategies to accelerate the eco-engineering pedogenesis of bauxite residues.

Humic Substances↗

PubMedDate not supplied

[Interaction of microorganisms with solids].

The paper generalizes data from literature dedicated to microorganisms interaction with solids. This interaction is widely spread in nature and considerably affects physiological activity of microbial populations. The role of physical, chemical and biological factors in this process is analyzed. It is noted that under certain conditions the hydrophobic forces are the basic factor in this interaction. The role of the cell surface components in this process is discussed.

Bacterial Adhesion↗

PubMed1999

Interaction of antimicrobial peptides with biological and model membranes: structural and charge requirements for activity.

Species right across the evolutionary scale from insects to mammals use peptides as part of their host-defense system to counter microbial infection. The primary structures of a large number of these host-defense peptides have been determined. While there is no primary structure homology, the peptides are characterized by a preponderance of cationic and hydrophobic amino acids. The secondary structures of many of the host-defense peptides have been determined by a variety of techniques. The acyclic peptides tend to adopt helical conformation, especially in media of low dielectric constant, whereas peptides with more than one disulfide bridge adopt beta-structures. Detailed investigations have indicated that a majority of these host-defense peptides exert their action by permeabilizing microbial membranes. In this review, we discuss structural and charge requirements for the interaction of endogenous antimicrobial peptides and short peptides that have been derived from them, with membranes.

Amino Acid Sequence↗

PubMed2004

Novel approach to characterization of combined pharmacodynamic effects of antimicrobial agents.

There is considerable need for new modeling approaches in the study of combined antimicrobial effects. Current methods based on the Loewe additivity and Bliss independence models are associated with implicit assumptions about the interacting system. To circumvent these limitations, we propose an alternative approach to the quantification of pharmacodynamic drug interaction (PDI). Pilot time-kill studies were performed with 10(8) CFU of Pseudomonas aeruginosa/ml at baseline with meropenem or tobramycin alone. The studies were repeated with 25 concentration combinations of meropenem (0 to 64 mg/liter) and tobramycin (0 to 32 mg/liter) in a five-by-five array. The data were modeled with a three-dimensional response surface using effect summation as the basis of null interaction. The interaction index (Ii) is defined as the ratio of the volumes under the planes (VUP) of the observed and expected surfaces: VUP(observed)/VUP(expected). Synergy and antagonism are defined as Ii values of <1 and >1, respectively. In all combinations, an enhanced killing effect was seen compared to that of either drug at the same concentration. The most significant synergism was observed between 1 and 5 mg/liter of meropenem and between 1 and 4 mg/liter of tobramycin; seven out of nine combinations had a >2-log drop compared to the more potent agent. The Ii was found to be 0.76 (95% confidence interval, 0.65 to 0.91) for the concentration ranges of the agents. The results corroborate previous data indicating that meropenem is synergistic with an aminoglycoside when used in combination against P. aeruginosa. Our parametric approach to quantifying PDI appears robust and warrants further investigations.

Algorithms↗

PubMed1991

Complete structure of the cell surface polysaccharide of Streptococcus oralis C104: a 600-MHz NMR study.

Specific lectin-carbohydrate interactions between certain oral streptococci and actinomyces contribute to the microbial colonization of teeth. The receptor molecules of Streptococcus oralis, 34, ATCC 10557, and Streptococcus mitis J22 for the galactose and N-acetylgalactosamine reactive fimbrial lectins of Actinomyces viscosus and Actinomyces naeslundii are antigenically distinct polysaccharides, each formed by a different phosphodiester-linked oligosaccharide repeating unit. These streptococci all coaggregated strongly with both A. viscosus and A. naesludii strains, whereas S. oralis C104 interacted preferentially with certain strains of the latter species. Receptor polysaccharide was isolated from S. oralis C104 cells and was shown to contain galactose, N-acetylgalactosamine, ribitol, and phosphate with molar ratios of 4:1:1:1. The 1H NMR spectrum of the polysaccharide shows that it contains a repeating structure. The individual sugars in the repeating unit were identified by 1H coupling constants observed in E-COSY and DQF-COSY spectra. NMR methods included complete resonance assignments (1H and 13C) by various homonuclear and heteronuclear correlation experiments that utilize scalar couplings. Sequence and linkage assignments were obtained from the heteronuclear multiple-bond correlation (HMBC) spectrum. This analysis shows that the receptor polysaccharide of S. oralis C104 is a ribitol teichoic acid polymer composed of a linear hexasaccharide repeating unit containing two residues each of galactopyranose and galactofuranose and a residue each of GalNAc and ribitol joined end to end by phosphodiester linkages with the following structure. [----6)Galf(beta 1----3)Galp(beta 1----6)Galf(beta 1----6)GalpNAc(beta 1----3) Galp(alpha 1----1)ribitol(5----PO4-]n

Actinomyces↗

PubMed2004

Microbial composition of biofilms in a brewery investigated by fatty acid analysis, fluorescence in situ hybridisation and isolation techniques.

Biofilms associated with brewery plants can harbour spoiling microorganisms that potentially damage the final product. Most beer-spoiling microorganisms are thought to depend on numerous interactions with the accompanying microbiota. However, there is no information on the microbial community structure of biofilms from bottling plants. The conveyors that transport the bottles to and from the plant are known as potential sources of microbial contamination of beer. Consequently, the material buildup from two conveyors was analysed using a cultivation/isolation approach, and the culture-independent techniques of whole cell fatty acid analysis and fluorescence in situ hybridisation (FISH). Heterogeneous communities were present at both conveyors. Although characteristic fatty acids for Eukarya were present, FISH-signals for Eukarya were extremely low. The Proteobacteria, in particular the Gammaproteobacteria, were abundant at both sample sites. Bacterial isolates were obtained for every dominating group detected by FISH: the Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria, the Xanthomonadaceae, the Actinobacteria, the Bacteroidetes and the Firmicutes.

Bacteria↗

PubMed2003

The interaction of moxifloxacin and warfarin in three elderly patients.

Moxifloxacin is an oral 8-methoxyquinolone with a broad spectrum of anti-microbial activity. Clinical trials indicate that moxifloxacin is a safe and well-tolerated antibiotic. We describe a potentially serious interaction between moxifloxacin and warfarin in three frail, elderly patients. The healthy volunteers studied for the moxifloxacin-warfarin interaction differ from these patients.

Journal Article↗

PubMed2004

Collectins: players of the innate immune system.

Collectins are a family of collagenous calcium-dependent defense lectins in animals. Their polypeptide chains consist of four regions: a cysteine-rich N-terminal domain, a collagen-like region, an alpha-helical coiled-coil neck domain and a C-terminal lectin or carbohydrate-recognition domain. These polypeptide chains form trimers that may assemble into larger oligomers. The best studied family members are the mannan-binding lectin, which is secreted into the blood by the liver, and the surfactant proteins A and D, which are secreted into the pulmonary alveolar and airway lining fluid. The collectins represent an important group of pattern recognition molecules, which bind to oligosaccharide structures and/or lipid moities on the surface of microorganisms. They bind preferentially to monosaccharide units of the mannose type, which present two vicinal hydroxyl groups in an equatorial position. High-affinity interactions between collectins and microorganisms depend, on the one hand, on the high density of the carbohydrate ligands on the microbial surface, and on the other, on the degree of oligomerization of the collectin. Apart from binding to microorganisms, the collectins can interact with receptors on host cells. Binding of collectins to microorganisms may facilitate microbial clearance through aggregation, complement activation, opsonization and activation of phagocytosis, and inhibition of microbial growth. In addition, the collectins can modulate inflammatory and allergic responses, affect apoptotic cell clearance and modulate the adaptive immune system.

Animals↗

PubMed1980

Role of bacterial interactions in the colonization of oral surfaces of Actinomyces viscosus.

The effects of several microbial residents of human oral cavities on the attachment of Actinomyces viscosus T14V to tooth surfaces were assessed by using the saliva-coated hydroxyapatite (sHA) in vitro system. Attachment to sHA by A. viscosus T14V was not inhibited in the presence of Streptococcus mutans GS5, either in the presence or absence of sucrose. Precoating sHA beads with S. mutans in the presence of sucrose also did not retard strain T14V attachment. However, the presence of Streptococcus sanguis M5 during strain T14V attachment markedly inhibited the interaction of A. viscosus T14V with sHA, whereas another S. sanguis strain, strain G9B, produced relatively weak inhibition. The inhibitory effect of S. sanguis M5 appeared to result from the direct interaction of this organism with A. viscosus T14V. Conversely, the presence of strain T14V markedly increased the attachment of S. sanguis M5 to sHA while partially inhibiting the attachment of S. sanguis G9B. Moreover, sHA beads precoated with A. viscosus T14V bound much higher levels of S. sanguis M5 relative to uncoated sHA, whereas S. sanguis G9B attachment was only weakly inhibited. It was also observed that sHA beads precoated with either S. sanguis M5 or G9B inhibited subsequent attachment by strain T14V. These results suggest the possibility that the attachment sites for both S. sanguis strains partially overlap those for A. viscosus T14V. Streptococcus mitis weakly inhibited attachment of strain T14V to sHA, and both Streptococcus salivarius and Lactobacillus casei had little effect on attachment. In addition, both a radioisotope attachment assay and fluorescent microscopy demonstrated no significant attachment of A. viscosus T14V to human epithelial cells.

Actinomyces↗