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At least 613 records · Page 34Linked to original sources
PubMed2005

Chronic rhinosinusitis and biofilms.

BACKGROUND AND HYPOTHESIS: Biofilms have been implicated in several head and neck infectious processes such as the following: dental and periodontal disease, otitis media, tympanostomy tube otorrhea, and chronic tonsillitis. We believe that biofilms also are associated with chronic rhinosinusitis. No information is known regarding the presence of biofilms in chronic rhinosinusitis. STUDY DESIGN AND SETTING: With institutional review board approval, tissue was obtained from consenting chronic rhinosinusitis patients who were undergoing functional endoscopic sinus surgery. Specimens were taken bilaterally from the ethmoid and maxillary sinuses. Inclusion criteria consisted of a positive diagnosis with pathologic tissue confirmation of chronic inflammation. Diagnosis was based on patient history, physical exam, and coronal sinus CT findings. Once collected, the specimens were labeled and fixed in formalin. The specimens were subsequently dehydrated, with successive immersions in increasing concentrations of diluted ethanol. The specimens were allowed to air dry and then were affixed to aluminum stubs with colloidal carbon. The sample surface was coated with a gold and palladium layer. The specimens were examined under an electron microscope. Areas of interest were photographed. RESULTS: Specimens from 5 patients were examined. All revealed bacterial biofilms. Invariably, biofilms were seen in the ethmoid, as well as in other samples. Denudation of ciliated and goblet cells was noted in all specimens. Biofilms resembled that of Staphylococcus species. Unidentified biofilms were also seen. CONCLUSIONS: This is the first documentation of biofilms in association with chronic rhinosinusitis. Further investigation is warranted, especially with control research subjects.

Adult↗
PubMed2006

Biofilms: implications in bioremediation.

Biofilms are assemblages of single or multiple populations that are attached to abiotic or biotic surfaces through extracellular polymeric substances. Gene expression in biofilm cells differs from planktonic stage expression and these differentially expressed genes regulate biofilm formation and development. Biofilm systems are especially suitable for the treatment of recalcitrant compounds because of their high microbial biomass and ability to immobilize compounds. Bioremediation is also facilitated by enhanced gene transfer among biofilm organisms and by the increased bioavailability of pollutants for degradation as a result of bacterial chemotaxis. Strategies for improving bioremediation efficiency include genetic engineering to improve strains and chemotactic ability, the use of mixed population biofilms and optimization of physico-chemical conditions. Here, we review the formation and regulation of biofilms, the importance of gene transfer and discuss applications of biofilm-mediated bioremediation processes.

Bacteria↗
PubMed2005

Biofilm production by Staphylococcus aureus associated with intramammary infection.

Biofilm production by 221 Staphylococcus aureus isolates from 45 dairy herds was evaluated. Isolates were from composite milk of 117 cows, from teat skin of 70 cows, and from 34 milking machine unit liners. Of S. aureus from milk samples, 41.4% were biofilm producers, as compared to 24.7 and 14.7% of the isolates collected from skin and liners. Pulsed field gel electrophoresis (PFGE) best categorized S. aureus biofilm producers as compared to phage typing and binary typing. PFGE types that were significantly associated with isolation from milk as opposed to teat skin or liners, had isolates that were more likely to produce biofilm than PFGE types that were isolated from milk, skin and liners at similar frequencies. By contrast, PFGE type A was significantly associated with isolation from teat skin and had few biofilm producers. PFGE type Q, which is exclusively a milk, isolate produced more biofilm as evidenced by absorbance values. Given S. aureus that are associated with milk are more likely to produce biofilm as compared to extramammary sources (teat skin and milking unit liners), suggests that biofilm production is a risk factor for infection.

Animals↗
PubMed2004

Investigation of biocide efficacy by photoacoustic biofilm monitoring.

The undesired growth of biofilms on solid surfaces is often termed biofouling. Biofilms consist mainly of water and microbial cells which are embedded in a biopolymer matrix. Biofouling lowers the water quality and increases the frictional resistance in tubes. Further, biofilms increase the pressure differences in membrane processes and can clog filtration membranes, valves, and nozzles. For investigation and improvement of biocide efficacy and anti-fouling strategies, on-line and in situ monitoring of the biofilm is necessary. In this study, photoacoustic spectroscopy (PAS) was employed for biofilm monitoring. PAS allows the depth-resolved investigation of growth and detachment processes of biofilms. Strategies based on the oxidant hydrogen peroxide were compared to popular isothiazolinone biocides. Hydrogen peroxide allowed a very fast and efficient removal of attached biofilms, whereas no effect on the biofilm matrix was observed in most cases when isothiazolinone biocides were used.

Acoustics↗
PubMed2005

Evaluation of some halogen biocides using a microbial biofilm system.

A simple method for the formation of microbial biofilms of three species, Pseudomonas fluorescens, Pseudomonas aeruginosa, and Klebsiella pneumoniae, on a small glass slide was established, and its suitability for evaluation of disinfectant efficacy was examined. The biofilms formed were observed in situ by confocal laser scanning microscopy (CLSM). Using the biofilms established, biocidal efficacy of several halogen biocides, such as hypochlorite (HOCl), bromochlorodimethylhydantoin (Br, Cl-DMH), ammonia monochloramine (NH2Cl), a stabilized hypobromite biocide named STABREX, and a mixed solution of NH4Br and HOCl, was evaluated. The formation of NHBrCl in the mixed solution was indicated by UV spectra analysis. Biofilm cells were more resistant to these biocides than planktonic cells and the extent of resistance varied with the biocide tested. Among the biocides tested, the biocidal potency of HOCl was the most susceptible to the change brought about by biofilm formation. By CLSM observation, differences in biofilm conformation were revealed between the microbial species. The efficacy of the biocide tested varied with the structure of biofilms formed. The assay method developed in the present study would be useful for further investigation on biofilm disinfection.

Anti-Bacterial Agents↗
PubMed2005

Characterization of biofilm structure and its effect on membrane permeability in MBR for dye wastewater treatment.

Two membrane bioreactors were operated at aerobic (DO=6.0mg/L) and anoxic (DO<0.3mg/L) conditions for the treatment of synthetic dye wastewater to determine the effect of dissolved oxygen on membrane filterability. The rate of membrane fouling for the anoxic MBR was five times faster than that for the aerobic MBR. Differences in the nature of the biofilm that was formed on the membrane surface as the result of different DO level was the main factor in the different fouling rates. The biofilm structure was characterized using digital image analysis techniques. Biofilm images were obtained using confocal laser scanning microscopy (CLSM) at various operation points. Structural parameters were then computed from these images using an image analysis software (ISA-2). The structural parameters indicated that the anoxic biofilm was thinner than the aerobic biofilm but the anoxic biofilm was spread out on the membrane surface more uniformly and densely, resulting in the higher membrane fouling. Based on the extracellular polymeric substances (EPS) visualization and quantification, it was also found that EPS, key membrane foulants were spread out more uniformly in the anoxic biofilm in spite of lower amount of EPS compared to that in the aerobic biofilm.

Biofilms↗
PubMed2006

Effect of DO concentration on biofilm structure and membrane filterability in submerged membrane bioreactor.

The structures of biofilms deposited on the membrane surface under different dissolved oxygen (DO) conditions were characterized to identify its relation to membrane filterability in membrane bioreactors (MBR). The rate of membrane fouling for the low DO (LDO) reactor was 7.5 times faster than that for the high DO (HDO) reactor. Even though the biofilm deposited on the membrane surface in the HDO was thicker than in the LDO at the operating terminated (TMP reached 30 Kpa), biofilm resistance in both reactors were similar. Exactly, specific cake resistance of the HDO was lower than that of the LDO. Difference in biofilm characteristics as a result of different DO level was main factor affecting biofouling for both MBRs. The number of small particles ranging from 2-5mum in the biofilm as well as in the bulk solution for the LDO was greater than those for the HDO. The small particles in the bulk solution of the LDO more preferentially deposited on the membrane surface than those of HDO did. Hence, the biofilm porosity in the LDO (0.65) was smaller than that in HDO (0.85). The reduced porosity of LDO biofilm resulted in lower filterability than the HDO. The porosity data obtained from analysis of images of biofilm using confocal scanning laser microscopy (CLSM) was verified in terms of specific cake resistance (alpha) by comparing the experimentally measured values with the semi-theoretically computed values.

Biofilms↗
PubMed2001

Methane microprofiles in a sewage biofilm determined with a microscale biosensor.

Microprofiles of the methane concentration in a 3.5-mm-thick sewage outlet biofilm were measured at high spatial and temporal resolution using a microscale biosensor for methane. In the freshly collected biofilm, methane was building up to a concentration of 175 mumol l-1 at 3 mm depth with a total methanogenesis of 0.14 mumol m-2 s-1, as compared to an aerobic respiration (including methane oxidation) of 0.80 mumol m-2 s-1. A model biofilm was established by homogenisation of an in situ biofilm and 12 days of incubation with surplus sodium acetate. The homogenised biofilm was able to maintain 50% of the methanogenic activity in the absence of external electron donor. Oxygen had only a minor effect on the methane production, but aerobic respiration consumed a substantial part of the produced methane and was thus an important control on methane export from the biofilm. A concentration of 2 mmol l-1 nitrate was shown to inhibit methanogenesis only in the upper layer of the biofilm, whereas a further addition of 2 mmol l-1 sulphate inhibited methanogenesis in the entire biofilm. The study demonstrated the power of the methane microsensor in the study of microhabitats with concurrent production and consumption of methane.

Bacteria↗
PubMed2002

Bulk water phase and biofilm growth in drinking water at low nutrient conditions.

In this study, the bacterial growth dynamics of a drinking water distribution system at low nutrient conditions was studied in order to determine bacterial growth rates by a range of methods, and to compare growth rates in the bulk water phase and the biofilm. A model distribution system was used to quantify the effect of retention times at hydraulic conditions similar to those in drinking water distribution networks. Water and pipe wall samples were taken and examined during the experiment. The pipes had been exposed to drinking water at approximately 13 degrees C, for at least 385 days to allow the formation of a mature quasi-stationary biofilm. At retention times of 12 h, total bacterial counts increased equivalent to a net bacterial growth rate of 0.048 day(-1). The bulk water phase bacteria exhibited a higher activity than the biofilm bacteria in terms of culturability, cell-specific ATP content, and cell-specific leucine incorporation rate. Bacteria in the bulk water phase incubated without the presence of biofilm exhibited a bacterial growth rate of 0.30 day(-1). The biofilm was radioactively labelled by the addition of 14C-benzoic acid. Subsequently, a biofilm detachment rate of 0.013 day(-1) was determined by measuring the release of 14C-labelled bacteria of the biofilm. For the quasi-stationary phase biofilm, the detachment rate was equivalent to the net growth rate. The growth rates determined in this study by different independent experimental approaches were comparable and within the range of values reported in the literature.

Adenosine Triphosphate↗
PubMed1999

In vitro bactericidal activities of beta-lactamases, amikacin, and fluoroquinolones against Pseudomonas aeruginosa biofilm in artificial urine.

OBJECTIVES: To compare bactericidal activities of antimicrobial agents against Pseudomonas aeruginosa biofilms by employing an in vitro model of catheter-associated infection because such infections are refractory to antimicrobial treatment. METHODS: Bactericidal activities of piperacillin (PIPC), ceftazidime (CAZ), panipenem (PAPM), amikacin (AMK), ciprofloxacin (CPFX), and levofloxacin (LVFX) were examined against a P. aeruginosa biofilm generated on a Teflon catheter in artificial urine. The colony-forming activities of biofilm bacteria were determined for 48 hours during the treatment with each drug at concentrations of 1 up to 128 times the minimal bactericidal concentration (MBC), and time-kill curves were constructed by plotting the viable cell counts against time. RESULTS: Although CAZ was more bactericidal to the biofilm bacteria than PIPC, the biofilm bacteria still remained on the catheter during CAZ treatment at a concentration 128 times the MBC for 48 hours. Biofilm bacteria were completely eradicated within 48 hours by treatment with PAPM and AMK at a concentration 64 and 128 times the MBC, respectively. Both CPFX and LVFX eradicated biofilm bacteria completely by 24 hours at a concentration 32 times the MBC. CONCLUSIONS: These results indicate that fluoroquinolones have the most potent bactericidal activity against the P. aeruginosa biofilm generated in urine.

Amikacin↗
PubMed2002

Modified enzyme activity assay to determine biofilm biomass.

An assay of potential exoproteolytic enzyme activity was modified to quantitatively measure the biomass of attached biofilm. The assay utilized the nonfluorescent compound L-leucine-beta-naphthylamide (LLbetaN) that becomes fluorescent when bacterial exoenzymes break the peptide bond, releasing the fluorochrome beta-naphthylamine. Fluorescence development was measured by pumping the liquid phase of a biofilm sample through a fluorescence detector and recording the detector output using a personal computer. A significant linear relationship was shown to exist between the rate of fluorescence development and the biofilm's biomass as carbon, determined using total direct cell counts, measured cell volumes and an existing relationship between cell volume and cell carbon. The technique was used to measure biofilm biomass for experiments where iron oxides were the substratum. Biofilm biomass measurements made using heterotrophic plate counts (HPCs) on R2A medium were shown to correlate well to biomass measurements made using the modified enzyme assay. The technique was shown to be sufficiently sensitive to measure biomass on samples containing little biofilm biomass, such as those exposed to free chlorine. While granular and porous media were used for the experiments presented, small biofilm coupons could easily be used to measure biofilm biomass, expanding the number of possible applications for the enzyme assay technique.

Bacteria↗
PubMed2002

Application of fluorescently labelled lectins for the visualization and biochemical characterization of polysaccharides in biofilms of Pseudomonas aeruginosa.

Fluorescently labelled lectins were used in combination with epifluorescence microscopy and confocal laser scanning microscopy to allow the visualization and characterization of carbohydrate-containing extracellular polymeric substances (EPS) in biofilms of Pseudomonas aeruginosa. A mucoid strain characterized by an overproduction of the exopolysaccharide alginate, and an isogenic, non-mucoid strain were used. Model biofilms grown on polycarbonate filters were treated with lectins concanavalin A (ConA) and wheat germ agglutinin (WGA) that were fluorescently labelled with fluorescein isothiocyanate or tetramethyl rhodamine isothiocyanate. Fluorescently labelled ConA yielded cloud-like regions that were heterogeneously distributed within mucoid biofilms, whereas these structures were only rarely present in biofilms of the non-mucoid strain. The bacteria visualized with the fluorochrome SYTO 9 were localized both within and between the ConA-stained regions. In WGA-treated biofilms, the lectin was predominantly associated with bacterial cells. Alginate seemed to be involved in the interaction of ConA with the EPS matrix, since (i) pre-treatment of biofilms with an alginate lyase resulted in a loss of ConA biofilm staining, and (ii) using an enzyme-linked lectinsorbent assay (ELLA), ConA was shown to bind to purified alginate, but not to alginate that was degraded by alginate lyase. The application of fluorescently labelled lectins in combination with ELLA was found to be useful for the visualization and characterization of extracellular polysaccharide structures in P. aeruginosa biofilms.

Biofilms↗
PubMed2000

Comparative evaluation of adhesion and biofilm formation of different Listeria monocytogenes strains.

Thirteen Listeria monocytogenes strains were used to grow biofilms on glass surfaces in static conditions at 37 degrees C for up to 4 days. After the initial 3-h adhesion and in subsequent 1-day intervals, cell numbers were determined using standard plate count after swabbing the cells from the glass surface. The three-dimensional structure of in situ biofilms was determined by confocal scanning laser microscopy (CSLM). After 3 h incubation, bacterial cells for all 13 strains of L. monocytogenes were found attached to glass slides and all strains formed biofilms within 24 h. The strains varied significantly in their ability to adhere to the surface and significant differences for cell numbers after 24 h biofilm growth were found. Cell counts in biofilms formed by five L. monocytogenes strains were monitored over 4 days. The counts increased for the first 2 days reaching 10(5) cfu/cm2, except for L. monocytogenes 7148 (10(4) cfu/cm2). After 2 days, cell counts remained at 10(5) cfu/cm2 for four strains (tested on days 3 and 4), while L. monocytogenes 7148 continued to grow and reached 10(5) cfu/cm2 on day 4. This difference in biofilm growth was not related to variations in growth rates of planktonic cells suggesting that growth behaviour of Listeria in biofilms may be different from their planktonic growth. CSLM revealed that the biofilms grown under static conditions consisted of two distinct layers with 0.5 log10 higher cell numbers in the bottom layer as compared to the upper layer.

Bacterial Adhesion↗
PubMed1999

Behaviour of L. monocytogenes in an artificially made biofilm of a nisin-producing strain of Lactococcus lactis.

The survival of Listeria monocytogenes in a binary biofilm with a bacteriocin producer (Lactococcus lactis CNRZ 150) was investigated. Two situations were simulated: in the first, L. monocytogenes was deposited on a 1-day biofilm of Lactococcus lactis (deferred adhesion); in the second, L. monocytogenes was simultaneously mixed with Lact. lactis (simultaneous adhesion). Biofilms were cultivated in tryptic soy broth supplemented with 6 g l(-1) of yeast extract (TSB-YE) and L. monocytogenes counts were followed for 48 h, both in co-culture with Lact. lactis and in pure culture. The influence of the mode of inoculation of L. monocytogenes (deferred or simultaneous adhesion) into the Lact. lactis biofilm, the size of the L. monocytogenes inoculum and the replacement of the culture medium at 20-24 h on the survival of L. monocytogenes was studied. Results showed that the antilisterial activity of the Lact. lactis started within the first 6 h of the deposition of L. monocytogenes. The log cycle reduction rate in number of L. monocytogenes in the mixed biofilm (compared to the pure biofilm) was greatly dependent on the inoculum size: when the smallest inoculum was used to colonise stainless steel coupons (10(6)-10(7) CFU ml(-1)), the log cycle reduction was greater and L. monocytogenes was not detected after t = 10 h (simultaneous adhesion) and t = 24 h (deferred adhesion) in the adherent population as well as in the planktonic population. On the other hand, in the case of a greater supply of L. monocytogenes (10(8) CFU ml(-1)), the results showed that the early reduction of L. monocytogenes counts was relatively slow and was followed by a stabilisation of the population, leading to the establishment of a great number of resident cells in the biofilm (10(5) to 106 CFU cm(-2)). This population level was maintained during the 48 h of experimentation and replacement of the culture media with fresh medium at t = 22 h (simultaneous adhesion) or t = 24 h (deferred adhesion) did not modify the level of the population of L. monocytogenes within the biofilm.

Biofilms↗
PubMed2000

Development of a biofilm formation method for waste forms stability evaluation.

The development of an accurate assessment protocol is critical for the prediction of long-term performance of waste disposal systems under field conditions. In this study, the development of a biofilm formation method for the evaluation of waste forms stability to microbially induced degradation (MID) is reported. The development process involved significant modifications to the existing Nuclear Regulatory Commission (NRC) approach. In the biofilm formation method, the control media and fermenter broths are designed to be of similar pH to avoid overestimation of the microbe's capability to degrade the waste forms. In the NRC approach, the pH values are different. The existing one-stage process of the NRC approach is also replaced with a two-stage process in the biofilm formation method. This is to ensure full evaluation of the microbe's involvement in waste forms degradation. The first stage of the two-stage process is for biofilm formation and the second is for biofilm evaluation. The use of a two-stage process eliminates the possibility of substrate limitation, resulting in values of degradation indices that are about two times higher than those obtained using the single-stage NRC approach. Two waste forms (100% Tuskegee cement and 21% cobalt chloride/79% cement) were used in the development of the biofilm formation method. Both waste forms showed evidence of biofilm formation. The formation of biofilm on the cobalt-containing waste form indicates a lack of anti-microbial capability of cobalt.

Biodegradation, Environmental↗
PubMed2002

Biofilm formation in Escherichia coli is affected by 3-(N-morpholino)propane sulfonate (MOPS).

In most natural environments, association with a surface in a structure known as a biofilm is the prevailing microbial life-style. Escherichia coli has been a useful model for the study of biofilm formation. Here we analyzed the amounts of biofilm formed when E. coli was cultured in the presence of MOPS [3-(N-morpholino)propane sulfonatel. We used the "O'Toole and Kolter" method, which consisted of growing cells in PVC microtiter dishes and staining the formed biofilm with crystal violet. Our results showed that: 1) the addition of 100 mM MOPS to the rich Luria-Bertani (LB) medium increased the capacity of biofilm formation of several E. coli strains; and 2) the biofilm formed by cells growing in the presence of MOPS was more evident and well defined than that of cells cultured in LB-only medium. The improved ability of forming biofilms was maintained even for 60 h after removing MOPS from the medium, indicating that this improvement was due to a change in the metabolism of E. coli growing in the presence of MOPS or that, under these conditions, biofilm formation was favored.

Biofilms↗
PubMed2003

Quorum sensing-dependent biofilms enhance colonization in Vibrio cholerae.

Vibrio cholerae is the causative agent of the diarrheal disease cholera. By an incompletely understood developmental process, V. cholerae forms complex surface-associated communities called biofilms. Here we show that quorum sensing-deficient mutants of V. cholerae produce thicker biofilms than those formed by wild-type bacteria. Microarray analysis of biofilm-associated bacteria shows that expression of the Vibrio polysaccharide synthesis (vps) operons is enhanced in hapR mutants. CqsA, one of two known autoinducer synthases in V. cholerae, acts through HapR to repress vps gene expression. Vibrio biofilms are more acid resistant than planktonic cells. However, quorum sensing-deficient biofilms have lower colonization capacities than those of wild-type biofilms, suggesting that quorum sensing may promote cellular exit from the biofilm once the organisms have traversed the gastric acid barrier of the stomach. These results shed light on the relationships among biofilm development, quorum sensing, infectivity, and pathogenesis in V. cholerae.

Acyltransferases↗
PubMed2004

Uranium immobilization by sulfate-reducing biofilms.

Hexavalent uranium [U(VI)] was immobilized using biofilms of the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans G20. The biofilms were grown in flat-plate continuous-flow reactors using lactate as the electron donor and sulfate as the electron acceptor. U(VI)was continuously fed into the reactor for 32 weeks at a concentration of 126 microM. During this time, the soluble U(VI) was removed (between 88 and 96% of feed) from solution and immobilized in the biofilms. The dynamics of U immobilization in the sulfate-reducing biofilms were quantified by estimating: (1) microbial activity in the SRB biofilm, defined as the hydrogen sulfide (H2S) production rate and estimated from the H2S concentration profiles measured using microelectrodes across the biofilms; (2) concentration of dissolved U in the solution; and (3) the mass of U precipitated in the biofilm. Results suggest that U was immobilized in the biofilms as a result of two processes: (1) enzymatically and (2) chemically, by reacting with microbially generated H2S. Visual inspection showed that the dissolved sulfide species reacted with U(VI) to produce a black precipitate. Synchrotron-based U L3-edge X-ray absorption near edge structure (XANES) spectroscopy analysis of U precipitated abiotically by sodium sulfide indicated that U(VI) had been reduced to U(IV). Selected-area electron diffraction pattern and crystallographic analysis of transmission electron microscope lattice-fringe images confirmed the structure of precipitated U as being that of uraninite.

Biofilms↗