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At least 811 records · Page 45Linked to original sources
PubMed2005

Effect of oxygen limitation on the in vitro antimicrobial susceptibility of clinical isolates of Pseudomonas aeruginosa grown planktonically and as biofilms.

Pseudomonas aeruginosa, the predominant causative pathogen of chronic lung infection in patients with cystic fibrosis, may grow under anaerobic conditions as biofilms in the lungs of cystic fibrosis patients. To determine if growth under anaerobic conditions affects the antimicrobial susceptibility of P. aeruginosa, the susceptibility of clinical isolates of P. aeruginosa grown planktonically and as biofilms to a range of antibiotics was determined. Growth under anaerobic conditions did not reduce the ability of ceftazidime, meropenem, aztreonam, piperacillin, or piperacillin/tazobactam to inhibit planktonic growth, with MIC50 values for these antibiotics remaining unchanged or decreasing. However, tobramycin was less effective at inhibiting planktonic bacterial growth under anaerobic conditions, with the MIC50 of tobramycin increasing twofold. Growth under anaerobic conditions also decreased the bactericidal activity of tobramycin, with the MBC50 of tobramycin increasing fourfold. The killing kinetics of tobramycin was also examined under aerobic and anaerobic conditions for selected isolates. When isolates 6A and 12A were grown aerobically, concentration-dependent decreases in total viable count were apparent with tobramycin. In contrast, when these isolates were grown anaerobically, tobramycin at the same concentrations did not decrease the total viable count. When isolates were grown as biofilms under both aerobic and anaerobic conditions, isolate- and concentration-dependent differences in killing of the biofilms by tobramycin were apparent. However, tobramycin at concentrations up to 128 mg/l was unable to eradicate biofilms of any of the isolates tested, whether biofilms were grown aerobically or anaerobically. These results show that oxygen limitation may reduce, in a strain-dependent manner, the susceptibility to tobramycin of P. aeruginosa grown planktonically and as biofilms.

Aerobiosis↗
PubMed2003

Colored moderately thermophilic bacteria in paper-machine biofilms.

Biofilms cause several problems in papermaking. This report describes a microbiological survey of colored biofilms in six paper and board machines, including two case studies of outbreaks of colored slimes in which the causative bacteria were found. A total of 95 pink-, red-, orange- or yellow-pigmented strains were isolated. Nearly all (99%) of the strains grew at 52 degrees C, 72% grew at 56 degrees C, but only 30% grew at 28 degrees C, indicating that most of the strains were moderately thermophilic. Biofilm formation potential and biocide susceptibility of the strains were analyzed with a microtiter plate assay. In the presence of 5 ppm of methylene bisthiocyanate or 2,2-dibromo-3-nitrilopropionamide in paper-machine water, 55 strains formed biofims. Moreover, 39 strains increased biofilm production by 5-753% in the presence of biocide, suggesting that biocide concentrations inhibitory to planktonic but not to surface-attached cells may actually promote biofouling. The cells may have inactivated a portion of the biocides, as the cell density in this assay was high, corresponding to the highest cell densities occurring in the circulating waters. Four groups of colored bacteria that were isolated from several mills were identified. Pink-pigmented Deinococcus geothermalis and red-pigmented Meiothermus silvanus occurred as common primary biofilm-formers in paper machines. This report is the first description of the involvement of Meiothermus species in red-slime formation in the paper industry. The third group of bacteria (putative new species related to Roseomonas) contained strains that were not biofilm formers, but which were commonly found in slimes of neutral or alkaline machines. The fourth group contained red-pigmented biofilm-forming strains representing a novel genus of alpha- Proteobacteria related to Rhodobacter. Many colored paper-machine bacteria are species previously known from microbial mats of hot springs. Some characteristics of the bacterial groups are described here in order to facilitate their recognition in future cases of colored-slime outbreaks in the paper industry.

Biofilms↗
PubMed2004

Formation of biofilms in drinking water distribution networks, a case study in two cities in Finland and Latvia.

The formation of biofilms in drinking water distribution networks is a significant technical, aesthetic and hygienic problem. In this study, the effects of assimilable organic carbon, microbially available phosphorus (MAP), residual chlorine, temperature and corrosion products on the formation of biofilms were studied in two full-scale water supply systems in Finland and Latvia. Biofilm collectors consisting of polyvinyl chloride pipes were installed in several waterworks and distribution networks, which were supplied with chemically precipitated surface waters and groundwater from different sources. During a 1-year study, the biofilm density was measured by heterotrophic plate counts on R2A-agar, acridine orange direct counting and ATP-analyses. A moderate level of residual chlorine decreased biofilm density, whereas an increase of MAP in water and accumulated cast iron corrosion products significantly increased biofilm density. This work confirms, in a full-scale distribution system in Finland and Latvia, our earlier in vitro finding that biofilm formation is affected by the availability of phosphorus in drinking water.

Bacteria↗
PubMed2005

Destruction of Deinococcus geothermalis biofilm by photocatalytic ALD and sol-gel TiO2 surfaces.

The aim of the present work was to explore possibilities of photocatalytic TiO2 coating for reducing biofilms on non-living surfaces. The model organism, Deinococcus geothermalis, known to initiate growth of durable, colored biofilms on machine surfaces in the paper industry, was allowed to form biofilms on stainless steel, glass and TiO2 film coated glass or titanium. Field emission electron microscopy revealed that the cells in the biofilm formed at 45 degrees C under vigorous shaking were connected to the surface by means of numerous adhesion threads of 0.1-0.3 microm in length. Adjacent cells were connected to one another by threads of 0.5-1 microm in length. An ultrastructural analysis gave no indication for the involvement of amorphous extracellular materials (e.g., slime) in the biofilm. When biofilms on photocatalytic TiO2 surfaces, submerged in water, were exposed to 20 W h m(-2) of 360 nm light, both kinds of adhesion threads were completely destroyed and the D. geothermalis cells were extensively removed (from >10(7) down to below 10(6) cells cm(-2)). TiO2 films prepared by the sol-gel technique were slightly more effective than those prepared by the ALD technique. Doping of the TiO2 with sulfur did not enhance its biofilm-destroying capacity. The results show that photocatalytic TiO2 surfaces have potential as a self-cleaning technology for warm water using industries.

Biofilms↗
PubMed2006

A bioremediation approach using natural transformation in pure-culture and mixed-population biofilms.

Bacterial transformation by naked DNA is thought to contribute to gene transfer and microbial evolution within natural environments. In nature many microbial communities exist as complex assemblages known as biofilms where genetic exchange is facilitated. It may be possible to take advantage of natural transformation processes to modify the phenotypes of biofilm communities giving them specific and desirable functions. Work described here shows that biofilms composed of either pure cultures or mixed populations can be transformed with specific catabolic genes such that the communities acquire the ability to degrade a particular xenobiotic compound. Biofilms were transformed by plasmids bearing genes encoding green fluorescent protein (mut2) and/or atrazine chlorohydrolase (atzA). Confocal microscopy was used to quantify the number of transformants expressing mut2 in the biofilms. Degradation of atrazine by expressed atzA was quantified by tandem mass spectrometry. PCR analysis was performed to confirm the presence of atzA in transformed biofilms. These results indicate that it should be possible to use natural transformation to enhance bioremediation processes performed by biofilms.

Acinetobacter↗
PubMed1995

Influence of culture conditions on biofilm formation by Escherichia coli O157:H7.

Biofilms of Escherichia coli O157:H7 were developed on stainless steel chips in trypticase soy broth (TSB), 1/5 dilution of TSB, 0.1% Bacto peptone (BP) and a minimal salts medium (MSM) supplemented with 0.04% of one of the following carbon sources: glucose, glycerol, lactose, mannose, succinic acid, sodium pyruvate or lactic acid. It was found that biofilms developed faster and a higher number of adherent cells (ca. 10(6) CFU/cm2) were recovered when the organisms were grown in the low nutrient media. Regardless of the carbon source, biofilms developed in MSM consisted of shorter bacterial cells and thicker extracellular matrix (ECM), with glucose as the best substrate for stable biofilm formation. Fewer bacteria in initial attachment, non-hydrophobicity of bacterial cells, lack of ECM formation and easy detachment of the biofilm bacteria may contribute to poor biofilm formation in TSB. ECM is probably important for the stability of biofilms; however, at 10 degrees C and under anaerobic conditions, ECM seems to be unnecessary.

Anaerobiosis↗
PubMed2026

Identification of genetic determinants that promote biofilm growth under heterotrophic conditions in Cupriavidus necator using transposon enrichment.

Cupriavidus necator is a metabolically versatile β-proteobacterium of growing interest for auto- and heterotrophic bioprocesses, yet the genetic determinants governing its biofilm formation remain largely uncharacterized, particularly under process-relevant heterotrophic conditions. Here, we applied a forward-genetics transposon-enrichment approach to identify loci which promote surface-associated growth. A high-density mini-Tn5 mutant library (26,185 insertion clones, exceeding the >17,000 required for genome-wide coverage) was cultivated as a biofilm in a microfluidic flow-cell system on fructose for 168 h, and the surface-associated community was characterized by deep sequencing. Twelve genes showed significantly elevated insertion frequencies, several with documented links to biofilm formation in other bacteria, including the ferrous-iron uptake system (feoA/feoB), galU, and a GSDEF/EAL dual-domain protein. The gene B2043 (E6A55_RS29530), encoding this c-di-GMP-metabolizing protein, was selected for validation by markerless deletion. Under static conditions, the ΔB2043 mutant showed a 1.69 ± 0.06-fold increase in biofilm-associated biomass (p = 5.16 × 10-15). Under flow-through conditions, the mutant attached faster, entered exponential growth ∼10 h earlier, reached its biovolume plateau ∼16 h earlier than the wild-type, and formed distinct tower-like structures. These results identify B2043 as a negative regulator of biofilm formation acting predominantly during attachment, provide the first experimental evidence for c-di-GMP-dependent biofilm regulation in C. necator H16, and establish a functional-genomics framework - together with eleven further candidate loci - for engineering productive biofilms in this organism.

Biofilm formation↗
PubMed2004

Effect of carbohydrates on fructosyltransferase expression and distribution in Streptococcus mutans GS-5 biofilms.

Streptococcus mutans produces a fructosyltransferase (FTF) enzyme, which synthesizes fructan polymers from sucrose. Fructans contribute to the virulence of the biofilm by acting as binding sites for S. mutans adhesion and as extracellular nutrition reservoir for the oral bacteria. Antibodies raised against a recombinant S. mutans FTF were used to test the effect of glucose, fructose, and sucrose on FTF expression in S. mutans GS-5 biofilms. Biofilms formed in the presence of fructose and glucose showed a higher ratio of FTF compared to biofilms formed in the presence of sucrose. Confocal laser scanning microscopy images of S. mutans biofilms indicated a carbohydrate-dependent FTF distribution. The layer adjacent to the surface and those at the liquid interface displayed high amounts cell-free FTF with limited amount of bacteria while the in-between layers demonstrated both cell-free FTF and cells expressing cell-surface FTF. Biofilm of S. mutans grown on hydroxyapatite surfaces expressed several FTF bands with molecular masses of 160, 125, 120, 100, and 50 kDa, as detected by using FTF specific antibodies. The results show that FTF expression and distribution in S. mutans GS-5 biofilms is carbohydrate regulated.

Antibodies, Bacterial↗
PubMed2006

Dynamic removal of oral biofilms by bubbles.

A novel approach to the removal of biofilms from solid surfaces is to pass large numbers of air bubbles over the surfaces. Such a phenomenon occurs when teeth are brushed with some types of powered toothbrushes that accelerate bubbly fluid against or across teeth surfaces. Video recordings of air bubbles propelled against a mature biofilm of Streptococcus mutans showed that the bubbles removed the biofilm at the point of collision. A mathematical model of the removal process was proposed and was able to simulate the kinetics of the biofilm removal process. Removal rate was modeled to be proportional to the bubble footprint area and the number of collisions per time. The fraction of biofilm removed per bubble collision is on the order of 0.4, a value much larger than would have been expected based on previous research employing bubbles that moved slowly along a surface that was partially covered with adherent bacteria. The higher removal efficiency is attributed to fluid dynamic shear forces that occur in conjunction with the thermodynamic forces that pull bacteria from a surface as a bubble contacts the biofilm. Fast bubbly flow is expected to remove bacterial biofilm from hard surfaces such as teeth.

Air↗
PubMed2005

Regulation of cell-surface genes and biofilm formation by the C. albicans transcription factor Bcr1p.

The impact of many microorganisms on their environment depends upon their ability to form surface bound communities called biofilms [1]. Biofilm formation on implanted medical devices has severe consequences for human health by providing both a portal of entry and a sanctuary for invasive bacterial and fungal pathogens [1 and 2]. Biofilm regulators and adherence molecules are extensively defined for many bacterial pathogens [3, 4, and 5], but not for fungal pathogens such as Candida albicans. Elongated filaments called hyphae are a prominent feature of C. albicans biofilms, and known genes that promote biofilm formation are required for hyphal development [2, 6, 7 and 8]. From a new library of transcription-factor mutants, we identify Bcr1p, a zinc finger protein required for formation of biofilms but not hyphae. Expression analysis shows that Bcr1p activates cell-surface protein and adhesin genes, including several induced during hyphal development. BCR1 expression depends upon the hyphal regulator Tec1p. Thus, BCR1 is a downstream component of the hyphal regulatory network that couples expression of cell-surface genes to hyphal differentiation. Our results indicate that hyphal cells are specialized to present adherence molecules that support biofilm integrity.

Biofilms↗
PubMed2005

Expression of a peroxiredoxin-glutaredoxin by Haemophilus influenzae in biofilms and during human respiratory tract infection.

Evidence is mounting that nontypeable Haemophilus influenzae grows as a biofilm in the middle ear of children with otitis media and the airways of adults with chronic obstructive pulmonary disease. To begin to assess antigens expressed by H. influenzae in biofilms, cell envelopes of bacteria grown as a biofilm were compared to those grown planktonically. A approximately 30kDa peroxiredoxin-glutaredoxin was present in greater abundance during growth in biofilms. Mutants deficient in expression of peroxiredoxin-glutaredoxin were constructed by homologous recombination in four clinical isolates. The mutants showed a 25-50% reduction in biofilm formation compared to the corresponding parent strains. To study in vivo expression of peroxiredoxin-glutaredoxin during human respiratory tract infection, paired pre- and post-exacerbation serum from adults with chronic obstructive pulmonary disease and H. influenzae in sputum were assayed using an enzyme-linked immunosorbent assay and purified recombinant peroxiredoxin-glutaredoxin. Eight from 18 (44.4%) paired serum samples showed a significant increase in antibody to peroxiredoxin-glutaredoxin from pre- to post-infection. These results indicate that (1) peroxiredoxin-glutaredoxin is present in greater abundance in H. influenzae biofilms compared to planktonically grown bacteria; (2) peroxiredoxin-glutaredoxin is involved in biofilm formation by H. influenzae and the degree of involvement varies among strains; and (3) peroxiredoxin-glutaredoxin is expressed by H. influenzae during infection of the human respiratory tract and is recognized by the human immune system.

Adult↗
PubMed2005

Phage release from biofilm and planktonic Staphylococcus aureus cells.

The ability of pathogenic staphylococci to form biofilms facilitates colonization and the development of chronic infections. Therapy is hampered by the high tolerance of biofilms towards antibiotic treatment and the immune system. We found evidence that lysogenic Staphylococcus aureus cells in a biofilm and in planktonic cultures spontaneously release phages into their surroundings. Phages were detected over a much longer period in biofilm cultures than in planktonic supernatants because the latter were degraded by secreted proteases. Phage release in planktonic and biofilm cultures was artificially increased by adding mitomycin C. Two morphologically distinct phages in the S. aureus strain used in this work were observed by electron microscopy. We postulate that phage-release is a frequent event in biofilms. The resulting lysis of cells in a biofilm might promote the persistence and survival of the remaining cells, as they gain a nutrient reservoir from their dead and lysed neighboring cells. This might therefore be an early differentiation and apoptotic mechanism.

Bacteriolysis↗
PubMed2006

Identification of adenoid biofilms in chronic rhinosinusitis.

OBJECTIVE: To compare the percent mucosal surface area of adenoids removed from children with chronic rhinosinusitis (CRS) and those with obstructive sleep apnea (OSA) infected with biofilms. DESIGN: Comparative micro-anatomic investigation of adenoid mucosa using scanning electron microscopy from patients with CRS and OSA. SUBJECTS: 4 females and 12 males ranging from 3 months to 10 years of age. RESULTS: Adenoids removed from patients with CRS had dense mature biofilms covering the mucosal surface. More specifically, adenoids removed from patients with CRS had an average of 94.9% of their mucosal surface covered with mature biofilms vs. an average of 1.9% coverage on the adenoids removed from patients with OSA. These differences were statistically significant at the p<0.001 level. CONCLUSIONS: It is well established that adenoidectomy is useful in the treatment of CRS resistant to antibiotics. Adenoids removed from patients with CRS had almost their entire mucosal surface covered with biofilms vs. scant coverage for patients with OSA (p<0.001). Decreased metabolic activity, decreased growth rate, and transmission of resistance genes all contribute to the antibiotic resistant nature of the biofilms. These metabolically sessile communities shed planktonic microorganisms on an intermittent basis. Therefore biofilms in the nasopharynx of children with CRS may act as a chronic reservoir for bacterial pathogens resistant to standard antibiotics. Also, the mechanical debridement of the nasopharyngeal biofilms may explain the observed clinical benefit associated with adenoidectomy in this subset of pediatric patients.

Adenoidectomy↗
PubMed2006

Sensitivity of bacterial biofilms and planktonic cells to a new antimicrobial agent, Oxsil 320N.

The effective concentrations of disinfectants were determined for planktonic bacteria using the norms EN 1040 and NF T 72-150. This concentration corresponds to biocide efficacy after 5 min of contact, followed by neutralization. However, micro-organisms often colonize a substratum and form microcolonies or biofilms where they are enclosed in exopolymer matrices. Biofilms are commonly resistant to a broad range of antimicrobial agents, and resistance mechanisms involve exopolymer matrices, changes in gene expression and metabolic alterations. Due to these different resistance mechanisms, it is difficult to select and titrate antimicrobial agents to be effective against biofilms. In this context, SODIFRA developed a new disinfectant, Oxsil 320N (French patent 94 15 193). Oxsil 320N is an association of three active principles: hydrogen peroxide, acetic acid/peracetic acid and silver. This biocide was tested on planktonic bacteria and on 24-h biofilms formed on AISI 304 stainless steel surfaces. The effective concentration of Oxsil 320N was also determined on biofilms using SODIFRA recommendations (without neutralization of the biocide). Data showed that the antimicrobial efficacy measured on planktonic bacteria is not a reliable indicator of performance when biofilm is present. When biofilms were exposed to Oxsil 320N, the concentration needed to achieve a 10(5)-fold decrease in concentration was 10 times higher than that for bacterial suspensions (0.313% Oxsil 320N). An effective concentration of Oxsil 320N of 3.13% was required.

Acetic Acid↗
PubMed2004

delta-Aminolaevulinic acid mediated photodynamic antimicrobial chemotherapy on Pseudomonas aeruginosa planktonic and biofilm cultures.

To demonstrate photodynamic antimicrobial chemotherapy (PACT) against planktonic and biofilm cultures of Pseudomonas aeruginosa, using photoporphyrin IX which could be endogenously synthesized by administrating delta-aminolaevulinic acid (delta-ALA), and a light emitted diode (LED) array to photoactivate the photosensitizer. P. aeruginosa suspended cells or biofilms, grown on a rotating disk reactor, were treated by different concentrations of delta-ALA in the dark for 1 h, followed by LED irradiation for various time. Regrowth experiments were conducted by placed PACT-treated disks back to a sterile reactor. Viable cells were determined by serial dilution and plate counts. Both P. aeruginosa planktonic and biofilm cells were inhibited by PACT with light doses or photosensitizer concentrations increasing. Treatments of planktonic cells with 10 mM delta-ALA and incident dose 240 J cm(-2) or 7.5 mM ALA and incident dose 360 J cm(-2) led to completely photoinactivation. No viable biofilm cells were found after treatment of 20 mM delta-ALA and incident dose 240 J cm(-2). However, regrowth was observed once PACT-treated biofilms were put back to a sterile reactor. Regrowth could be prevented only if biofilm samples were treated PACT twice. delta-ALA-mediated PACT on P. aeruginosa planktonic and biofilm cells was effective, though the detailed mechanism still required further investigation.

Aminolevulinic Acid↗
PubMed2004

Green and red fluorescent protein vectors for use in biofilm studies of the intrinsically resistant Burkholderia cepacia complex.

Cystic fibrosis isolates of the Burkholderia cepacia complex (BCC) have demonstrated a propensity to associate intimately with Pseudomonas aeruginosa in mixed community biofilms, which may impact on their overall pathogenicity during infection of the lungs in cystic fibrosis. Here, we describe the construction and use of novel green and red fluorescent protein expression vectors suitable for labeling biofilm cells of multi-resistant clinical isolates of the BCC for microscopic analysis of both single species biofilms and mixed community associations with P. aeruginosa. Antimicrobial susceptibility testing established that tetracycline and/or trimethoprim were suitable selective agents for widespread use in BCC. The green and red fluorescent protein genes, driven by constitutively active promoters, were cloned into two mobilizable plasmids pBBR1MCS-3 and pBBR1Tp, carrying tetracycline and trimethoprim resistance cassettes, respectively. The fluorescence of transformed BCC and P. aeruginosa planktonic cells was detectable using fluorescence microscopy and/or fluorometry. The plasmids were stable in the absence of selection for at least 3 days in planktonic and biofilm cultures, and fluorescence was still visible in a 4-day glass coverslip flow cell biofilm. The plasmids functioned well to distinguish the two species in a mixed community biofilm, with no indications of plasmid transfer between species or cross-talk of the fluorescent signals. These vectors represent the first green and red fluorescent vectors to be constructed and analyzed specifically for wide spread use in BCC and P. aeruginosa single and mixed biofilm cultures.

Anti-Infective Agents↗
PubMed2005

Construction of artificially structured microbial consortia (ASMC) using dielectrophoresis: examining bacterial interactions via metabolic intermediates within environmental biofilms.

The construction of artificial biofilms with defined internal architectures is described. Bacterial cells are suspended in a low conductivity medium, guided to specific areas in a microelectrode array by dielectrophoresis (DEP), and then immobilised using the flocculating agent poly(ethylenimine). Multispecies biofilms can be constructed by introducing different species at different times. The rapid construction of such biofilms with defined internal architectures provides, when combined with visual reporters of gene activity, a powerful new method for the investigation of the effects of the spatial organisation on interactions between bacterial species in biofilms. To demonstrate the utility of the technique as a method for investigating metabolic interactions in biofilms, aggregates were constructed from Acinetobacter sp. C6 and Pseudomonas putida::gfp. The Acinetobacter degrades benzyl alcohol, overproducing benzoate, which in turn is consumed by the Pseudomonas strain. The P. putida has a chromosomally expressed cassette encoding a gfp downstream of the promoter which controls degradation of benzoate, making the interaction between the two strains in the metabolism of benzyl alcohol visible by the production of green fluorescent protein (GFP). Microscopic observation of the biofilms, including the use of confocal laser scanning microscopy (CLSM), confirmed that metabolic exchange occurred. In addition, it was observed that the bacteria appear to have a preferred biofilm architecture, with P. putida in the bottom layer, and Acinetobacter at the top.

Acinetobacter↗
PubMed2006

Biofilm formation by Staphylococcus aureus and Pseudomonas aeruginosa is associated with an unfavorable evolution after surgery for chronic sinusitis and nasal polyposis.

OBJECTIVES: To determine whether biofilm-forming capacity of bacteria demonstrated in chronic rhinosinusitis (CRS) has an impact on persistence of the disease following endoscopic sinus surgery (ESS). METHOD: Thirty-one bacterial strains recovered from 19 patients with CRS at least 1 year post-ESS. Evolution of disease was assessed by questionnaire and endoscopy as favorable or unfavorable. The bacteria were cultured on a 96-well culture plaque and a semi-quantitative method using crystal violet to quantify biofilm production was used. RESULTS: Twenty-two of 31 samples produced a biofilm thicker or equal to the positive control. Biofilm production was noted in 6/10 Pseudomonas aeruginosa isolates, 8/10 Staphylococcus aureus, and 8/11 coagulase-negative staphylococci. Biofilm formation was associated with a poor evolution for Pseudomonas aeruginosa and Staphylococcus aureus, but not coagulase-negative staphylococcus. CONCLUSION: There is a correlation between in vitro biofilm-producing capacity by Pseudomonas aeruginosa and Staphylococcus aureus and unfavorable evolution after ESS, suggesting a role for biofilm production in chronic sinusitis. EBM RATING: B-2b.

Adult↗