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At least 757 records · Page 42Linked to original sources
PubMed2001

Influence of calcium ions on the mechanical properties of a model biofilm of mucoid Pseudomonas aeruginosa.

The mechanical properties of biofilms and in particular their mechanical strength is of great importance for both biofilm reactors and for the removal of undesired biofilms as in cases of biofouling and biocorrosion. By uniaxial compression measurements, it is possible to determine the apparent elastic or Young's modulus and the yield stress as parameters for mechanical stability. This was performed with a recently developed device, using model biofilms of mucoid strain Pseudomonas aeruginosa SG81. The biofilms were grown on membrane filters placed on nutrient agar medium with different concentrations of calcium ions. The compressive stress-strain behaviour up to failure was recorded at a compression speed of 1 micron s-1. The apparent Young's modulus, representing the stiffness of the biofilm, and the yield stress obtained from the stress--strain diagram were used for the description of mechanical properties of biofilms. A certain critical concentration of calcium ions was found where the Young's modulus of the P. aeruginosa biofilms increases strongly and subsequently remains constant for higher calcium concentrations. This behaviour is explained by the presence of calcium ions crosslinking alginate, which is the major component of the extracellular polymeric substances produced by the mucoid P. aeruginosa strain used in this investigation.

Biofilms↗
PubMed2001

Persistence of two model enteric viruses (B40-8 and MS-2 bacteriophages) in water distribution pipe biofilms.

The persistence of two model enteric virions (Bacteroides fragilis phage B40-8 and coliphage MS-2) within pipe biofilms was investigated in situ in an urban distribution system. Biofilms were allowed to develop on uPVC and stainless steel (SS) coupons in a modified Robbins' device for 70 d within a 150 mm uPVC reticulation main. Coupons were then placed in annular reactors and slug dosed with B40-8 and MS-2 phages (10(8) pfu/mL). Pipe water velocity, pH and free chlorine were recorded during the experimental period. Biofilms on uPVC were generally more abundant (based on total bacterial counts, HPCs, total protein and total carbohydrate). Both B40-8 and MS-2 were incorporated into biofilms formed on uPVC and SS coupons (> 10(4) and > 10(3) pfu/microgram protein respectively) and persisted for > 30 d and 6 d respectively, reflecting biofilm biomass on the two pipe surfaces. Virion loss/inactivation from biofilm followed an initial rapid phase, followed by a very slow phase representing approximately 0.01% of the original virion population. Virions, therefore, have the potential to accumulate within distribution biofilm and problems could arise when clusters of biofilm-associated enteric virions become detached from the substrata by hydrodynamic forces or sudden changes in disinfection regime.

Bacteroides fragilis↗
PubMed2001

Bacterial biofilms: a review of current research.

Biofilms provide bacterial cells with a protective environment that allows for survival from antibiotics and host defense mechanisms. In order to understand how to control biofilms, it is important to understand the complexity of the biofilm system. This is in overview of four areas of current biofilm research: biofilm resistance to antimicrobials and host defense mechanisms, the complexity of biofilm structure, the possible existence of a biofilm phenotype, and the ramifications of cell cell communication within the biofilm.

Bacterial Physiological Phenomena↗
PubMedDate not supplied

Testing antimicrobials against biofilm bacteria.

Standard laboratory methods are needed to assess the efficacy of antimicrobial agents that are applied to biofilm bacteria. Existing standard suspension tests and dried surface tests show much greater efficacy than antimicrobial agents applied to biofilms. The greater resistance of biofilm bacteria to antimicrobial agents can be attributed to a number of interacting factors, including reaction and diffusion processes that limit an agent's accessibility to bacteria, phenotypic changes in biofilm bacteria caused by stress, and adaptation of the bacteria. Because biofilm systems are so diverse, a variety of new biofilm tests with features that differ in important ways from existing tests will ultimately be required. For example, the biofilm test apparatus may include a pump and a continuous-flow stirred tank reactor. This report provides an overview of biofilm testing and suggests a strategy for creating standard test methods.

Bacteria↗
PubMed2003

Biofilm in combined sewers: wet weather pollution source and/or dry weather pollution indicator?

In a sewer trunk, three kinds of deposit, acting as potential wet weather sources, be found: the biofilm, the organic layer and the gross bed sediment. This research program, on the "Le Marais" catchment (Paris, France), focused on the biofilm. The objectives were to describe, using a Transmission Electronic Microscope, the architecture of the sewer biofilm and to investigate the contents and the distributions of aliphatic and aromatic hydrocarbons in biofilm. The electron micrographs illustrated a uniform film of bacteria totally covering the surface of a thick organic matrix. A large cohesion of the cell layer and organic matrix complex, due to exopolysaccharides, was noticed. Hence, the hydrocarbon contents were measured not only in the biofilm itself, but in this complex. Our results showed that almost all hydrocarbons were stored in the gross bed sediment and the organic layer and, consequently, the biofilm was not an important potential source of wet weather pollution. Comparison between the hydrocarbon distributions in the biofilm and in the other deposits indicated that the biofilm could be used as an indicator of the aliphatic hydrocarbon pollution in the organic layer.

Biofilms↗
PubMed2003

Influence of the Sonicare toothbrush on the structure and thickness of laboratory grown Streptococcus mutans biofilms.

PURPOSE: To evaluate the effect of powered brushing with the Sonicare electronic toothbrush on the structure and thickness reduction of S. mutans biofilms using digital time-lapse microscopy (DTLM) and confocal microscopy (CM) techniques. MATERIALS AND METHODS: S. mutans biofilms grown on glass microscope slides on BHI and 2% sucrose were exposed to Sonicare for 15 seconds with the bristle tips just contacting the slide, and at distances of 0.5, 1.0, and 1.5 mm above the slide. RESULTS: With direct bristle contact, the reduction in biofilm thickness was greater than 99%. DTLM showed the break up and detachment of biofilm caused by the shear forces generated by the rapid bristle motion in real time. The Sonicare was shown to significantly reduce biofilm thickness even when the bristles were 1 mm above the biofilm. The percent biofilm thickness reduction was inversely proportional to the bristle distance. This study demonstrates the Sonicare toothbrush effectively removed biofilm from hard flat surfaces both by direct bristle contact and by fluid dynamic shear forces alone.

Analysis of Variance↗
PubMed2003

Enteric virions and microbial biofilms--a secondary source of public health concern?

Through their many sorption sites, microbial biofilms can accumulate both organic and inorganic particulate and colloidal material from bulk water environments. An application of such first principles to the ecology of "biocolloidal" enteric virions would suggest that they too may be concentrated by biofilms in a similar way. Though previous studies have isolated human gastrointestinal (enteric) virions from microbial biofilms, the exact human health significance of this has been neither fully investigated nor completely understood. Through an assessment of the location, accumulation and persistence of model enteric virion (phiX174, MS2 and B40-8 bacteriophages as well as 20 nm fluorescent latex microspheres) within biofilms, the aim of the current study was to investigate whether the interaction of enteric virions with distribution pipe biofilms could provide a secondary source of public health concern to consumers. Model enteric virions were found to be incorporated into biofilms at concentrations representing 1% of those present in the adjacent bulk water environment. A sub-population (0.01%) of these persisted throughout an experimental period of 30 days, inferring their potential to accumulate over time. Furthermore, model enteric virions were partitioned into bacterial microcolonies, environments where biofilm bacteria can persist and re-grow, even in the presence of "acceptable" levels of disinfection. A risk model for enteric virion accumulation and release from distribution pipe biofilms suggested that associated risks may exceed USEPA benchmark values. These findings could have wide-reaching implications in water treatment and distribution strategies, and necessitate a re-appraisal of current water guideline values.

Bacteria↗
PubMedDate not supplied

Microbial biofilms in the gut: visualization by electron microscopy and by acridine orange staining.

The expression of colonization factors by gut bacteria, the growth rate of gut bacteria, and the rate of plasmid exchange by gut bacteria indicate that biofilms are a normal component of bacterial growth in the large bowel. Further, in vitro experiments demonstrate that growth of normal enteric bacteria in biofilms can be facilitated by secretory IgA (SIgA) and by mucins, 2 major components of the gut milieu. However, biofilms have not been previously observed in the normal gut. In this study, bacterial colonies characteristic of biofilms were observed by electron microscopy in normal rat, baboon, and human gut by electron microscopy. Confirming these results, acridine orange staining of flash-frozen tissues revealed biofilms in the mucus lining along normal gut epithelium. Immunofluorescenct microscopy supported this finding and demonstrated an association between IgA and the biofilms. These findings provide direct evidence that biofilms are present and may play an important role in the commensal relationship between enteric bacteria and their hosts. Hematoxylin and eosin staining of formalin-fixed tissues resulted in dissociation of the luminal contents from the epithelium, suggesting that the association between biofilms and the gut epithelium is sensitive to some conditions used to preserve tissue for histologic evaluation.

Acridine Orange↗
PubMed2004

Candida biofilms: antifungal resistance and emerging therapeutic options.

Intravascular catheter infections are a major cause of morbidity and mortality in hospitalized patients, accounting for the majority of the 200,000 nosocomial bloodstream infections occurring in the US annually. Of the intravenous lines that are culture-positive for Candida, 40% actually represent fungemia, which generally necessitates systemic treatment and line removal to affect cure. Until recently, the reason for the need for device removal was unclear. However, our research group and others have demonstrated a near-total resistance to antifungals by biofilm-associated Candida. Similar to bacterial species, Candida biofilm formation proceeds through early, intermediate and maturation phases. This process is associated with the generation of a polysaccharide extracellular matrix (ECM). Mature C. albicans biofilms have a heterogeneous architecture, in terms of distribution of fungal cells and ECM, and exhibit broad antimicrobial resistance. The mechanisms causing such profound antifungal resistance are beginning to be understood. Recent data indicate that resistance is phase-specific and multifactorial, involving efflux pumps and sterol synthesis (at early and mature biofilm phases, respectively). Neither metabolic quiescence nor the ECM appear to contribute substantially. Susceptibility testing and confocal scanning laser microscopy demonstrated that azoles failed to exert activity against mature Candida biofilms. However, sub-inhibitory concentrations of voriconazole impaired biofilm formation and caused cell morphological aberrations. In contrast, lipid-formulation amphotericins and the echinocandins uniquely exhibited activity against mature biofilms. The mechanisms underlying this ability are unknown. The role of other pharmacological (eg, catheter coatings, antimicrobial peptides and antibiotic locks) and non-pharmacological methods in the prevention and treatment of device-related biofilms is discussed in this review.

Animals↗
PubMed2004

Effects of hydroxylamine on microbial community structure and function of autotrophic nitrifying biofilms determined by in situ hybridization and the use of microelectrodes.

Effects of hydroxylamine (NH2OH), an intermediate of NH4+ oxidation, on microbial community structure and function of two autotrophic nitrifying biofilms fed with and without NH2OH were analyzed by a 16S rRNA approach and the use of microelectrodes. In the NH2OH-added biofilm, partial oxidation of NH4+ to NO2- was observed, whereas complete oxidation of NH4+ to NO3- was achieved in the control biofilm. In situ hybridization results revealed that no nitrite-oxidizing bacteria (NOB) hybridized with any specific probes were detected in the NH2OH-added biofilm. Thus, the addition of low concentrations of NH2OH (250 microM) completely inhibited the growth of NOB. Phylogenetic analysis of 16S rDNA indicated that the ammonia-oxidizing bacteria (AOB) detected in both biofilms were closely related to Nitrosomonas europaea, and that the clone sequences from both biofilm libraries have more than 99% similarity to each other. However, in situ hybridization results revealed that the addition of NH2OH changed the form of growth pattern of the dominant Nitrosomonas spp. from dense clusters mode to single scattered cells mode. Microelectrode measurements revealed that the average NH4+ consumption rate calculated in the NH2OH-added biofilm was two times higher than that in the control biofilm. This clearly demonstrated that the oxidation of NH4+ was stimulated by NH2OH addition.

Biofilms↗
PubMed2004

Contamination potential of drinking water distribution network biofilms.

Drinking water distribution system biofilms were investigated for the presence of hygienically relevant microorganisms. Early biofilm formation was evaluated in biofilm reactors on stainless steel, copper, polyvinyl chloride (PVC) and polyethylene coupons exposed to unchlorinated drinking water. After 12 to 18 months, a plateau phase of biofilm development was reached. Surface colonization on the materials ranged between 4 x 10(6) and 3 x 10(7) cells/cm2, with heterotrophic plate count (HPC) bacteria between 9 x 10(3) and 7 x 10(5) colony-forming units (cfu)/cm2. Established biofilms were investigated in 18 pipe sections (2 to 99 years old) cut out from distribution pipelines. Materials included cast iron, galvanized steel, cement and PVC. Colonization ranged from 4 x 10(5) to 2 x 10(8) cells/cm2, HPC levels varied between 1 and 2 x 10(5) cfu/cm2. No correlation was found between extent of colonization and age of the pipes. Using cultural detection methods, coliform bacteria were rarely found, while Escherichia coli, Pseudomonas aeruginosa and Legionella spp. were not detected in the biofilms. In regular operation, distribution system biofilms do not seem to be common habitats for pathogens. However, nutrient-leaching materials like rubber-coated valves were observed with massive biofilms which harboured coliform bacteria contaminating drinking water.

Biofilms↗
PubMedDate not supplied

Evidence of bacterial biofilms on frontal recess stents in patients with chronic rhinosinusitis.

BACKGROUND: Bacterial biofilms have been documented on middle ear mucosa, tonsils, and cholesteatoma. We hypothesize that bacterial biofilms are present in mucosa of patients with chronic sinusitis. We believe that frontal sinus stents may serve as a reservoir for biofilms. EXPERIMENT: We studied silicone frontal sinus stents removed from six patients 1 to 4 weeks after FESS with scanning electron microscopy (SEM). RESULTS: We identified evidence of bacterial biofilms on the frontal recess stents in six of six patients under SEM. Five of these patients had sinus cultures positive for Staphylococcus aureus. Bacterial biofilms were identified by evidence of glycocalyx, water channels, and three-dimensional structure. These images were similar to other images of known biofilms. CONCLUSIONS: This is evidence of the possible presence of bacterial biofilms on frontal sinus stents in patients with chronic sinusitis. Further study into the role of bacterial biofilms in perpetuating chronic sinusitis is warranted.

Biofilms↗
PubMed2006

[Susceptibility of Streptococcus mutans biofilm to antimicrobial agents].

OBJECTIVE: To investigate the susceptibility of Streptococcus mutans (S. mutans) biofilms to antimicrobial agent by confocal laser scanning microscopy (CLSM). METHODS: S. mutans biofilms formed in vitro on glass slice were acted on with penicillin of different concentrations for 3 h. Then these biofilms were stained by fluorescence and were observed by CLSM. The bacterial density and viability of biofilms were recorded. RESULTS: When S. mutans biofilms were exposed to penicillin of 2 500 mg/L for 3 h, it was not completely killed. The higher the concentration of penicillin was, the weaker the biofilms against penicillin. CONCLUSIONS: Compared with planktonic S. mutans, S. mutans biofilms produced stronger resistance to penicillin. It suggests that we should find new strategies to control the infection caused by biofilm in clinic.

Anti-Infective Agents↗
PubMed1996

Resistance of Streptococcus sanguis biofilms to antimicrobial agents.

Bacteria living in biofilms as dental plaque on tooth surfaces are generally more resistant to antimicrobial agents than bacteria in batch culture normally used for in vitro susceptibility testing. In order to compare the resistance of free-living and surface-grown oral bacteria, the MIC of Streptococcus sanguis 804 and ATCC 10556 to amoxicillin, doxycycline and chlorhexidine was determined by a broth dilution method. Subsequently, S. sanguis biofilms established in an in vitro flow model were perfused with the antimicrobial agents for 48 h at concentrations equal to and up to 500 times the MIC, and biofilm cell number was determined during this period. The antibiotics at the MIC did not affect the cell number of S. sanguis biofilms compared to the starting point, and only after 48 h at 500 times the MIC were the biofilm bacteria eliminated. At intermediate concentrations biofilm cell number gradually decreased. Chlorhexidine also gradually reduced biofilm cell number, but was inhibitory at concentrations closer to the MIC than was the case for the antibiotics. Thus S. sanguis in biofilms survived up to 500 times the MIC found in batch culture for up to 48 h.

Amoxicillin↗
PubMed1989

Application of an empirically derived growth curve model to characterize Staphylococcus epidermidis biofilm development on silicone elastomer.

An in vitro model permitting the development of a staphylococcal biofilm on silicone elastomer is described. Biofilm was determined over time by viable cell quantitation for S. epidermidis strains 8-14B, RP62 and SP2. The log10 viable count data were analysed empirically as a function of time using a negative exponential growth curve model. Although initial colonization and biofilm 72 h cell density of silicone was significantly higher for strain RP62 than SP2, biofilm growth rates did not differ. Strain 8-14B demonstrated a faster biofilm growth rate for the initial 24 h than did RP62 or SP2. The statistical model described was sensitive enough to detect strain differences in biofilm development on silicone elastomer and can be further employed to evaluate the ability of selected biomaterials to retard biofilm development, and the ability of various antimicrobial agents to influence biofilm microbe development.

Biocompatible Materials↗
PubMed1991

Proteus mirabilis biofilm protection against struvite crystal dissolution and its implications in struvite urolithiasis.

Proteus mirabilis biofilm formation, struvite (MgNH4PO4.6H2O) crystal formation and dissolution in an artificial urine mixture were monitored using computer-enhanced microscopy (CEM) and a 1 x 3 mm. glass flow cell. Image analysis showed that P. mirabilis biofilm formation did not occur to any extent at macroenvironment flow rates greater than two mL/h (equivalent to a microenvironment flow rate of less than 5 microns./sec). Essentially, cells attached to glass surfaces, grew slowly and divided. Daughter cells were generally released directly into the medium where they could then presumably colonize other regions. Microcolonies formed by the adhesion of aggregates of cells from the medium, and over time grew into biofilms. Struvite crystallization due to urease activity and pH elevation above neutrality, was preceded by the deposition of organic matter on the glass surface, followed by the appearance of a number of tiny (one to two microns.) crystals. Crystals forming within a biofilm at low dilution rates took on a characteristic twinned or "X-shaped" appearance (crystal habit) indicative of a rapid growth rate. Those forming outside the biofilm took on a more tabular appearance reflecting their slower growth. When the macroenvironment flow rate of artificial urine (initial pH 5.8) in the glass flow cell was increased from two mL/h to four mL/h, struvite crystals not associated with biofilms dissolved within five to 10 min. Crystals entrapped within the P. mirabilis biofilm withstood flow rates up to 200 mL/h presumably due to the maintenance of an alkaline Mg-saturated microenvironment within the biofilm. These observations may suggest a mechanism by which struvite calculi can grow in spite of neutral or acidic urine pH and resist mild acidification therapy.

Bacterial Adhesion↗
PubMed2004

Quantitative analyses of Streptococcus mutans biofilms with quartz crystal microbalance, microjet impingement and confocal microscopy.

Microbial biofilm formation can be influenced by many physiological and genetic factors. The conventional microtiter plate assay provides useful but limited information about biofilm formation. With the fast expansion of the biofilm research field, there are urgent needs for more informative techniques to quantify the major parameters of a biofilm, such as adhesive strength and total biomass. It would be even more ideal if these measurements could be conducted in a real-time, non-invasive manner. In this study, we used quartz crystal microbalance (QCM) and microjet impingement (MJI) to measure total biomass and adhesive strength, respectively, of S. mutans biofilms formed under different sucrose concentrations. In conjunction with confocal laser scanning microscopy (CLSM) and the COMSTAT software, we show that sucrose concentration affects the biofilm strength, total biomass, and architecture in both qualitative and quantitative manners. Our data correlate well with previous observations about the effect of sucrose on the adherence of S. mutans to the tooth surface, and demonstrate that QCM is a useful tool for studying the kinetics of biofilm formation in real time and that MJI is a sensitive, easy-to-use device to measure the adhesive strength of a biofilm.

Journal Article↗
PubMed1994

[An ATP bioluminescence assay for the analysis of bacterial biofilms].

To analyze the bio-activity of the bacterial biofilm, the ATP content of the biofilm was assayed using the ATP bioluminescence assay. A linear relationship between the ATP content and the number of the planktonic Pseudomonas aeruginosa cells was observed. An in vitro experiment was set up using a modified Robbins device (MRD). A biofilm of P. aeruginosa was developed on the silicon discs of this device by recirculating artificial urine medium through the MRD. The activity of the biofilm, assayed by ATP luminescence, increased rapidly during the first 4 hrs of circulation, and essentially remained unchanged for 32 hrs during medium circulation. After the biofilm developed, the medium was exchanged to the new artificial urine with piperacillin or clarythromycin or ofloxacin and circulated for 8 hrs. The biofilm changed its bio-activity by the antibiotics, and the change could be detected by measuring the ATP content. These changes of ATP content studied were correlated well with the findings detected by scanning electron microscopy. Finally, ATP measurement of the bacterial biofilm was useful in analyzing the bio-activity of bacterial biofilm.

Adenosine Triphosphate↗