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PubMed2002

Biofilm production by isolates of Candida species recovered from nonneutropenic patients: comparison of bloodstream isolates with isolates from other sources.

Biofilm production has been implicated as a potential virulence factor of some Candida species responsible for catheter-related fungemia in patients receiving parenteral nutrition. We therefore compared clinical bloodstream isolates representing seven different Candida species to each other and to those from other anatomical sites for the capacity to form biofilms in glucose-containing medium. Potential associations between the capacity to form biofilms and the clinical characteristics of fungemia were also analyzed. Isolates included the following from nonneutropenic patients: 101 bloodstream isolates (35 C. parapsilosis, 30 C. albicans, 18 C. tropicalis, 8 C. glabrata, and 10 other Candida species isolates) and 259 clinical isolates from other body sites (116 C. albicans, 53 C. glabrata, 43 C. tropicalis, 17 C. parapsilosis, and 30 other Candida species isolates). Organisms were grown in Sabouraud dextrose broth (SDB) containing a final concentration of 8% glucose to induce biofilm formation, as published previously. Biofilm production was determined by both visual and spectrophotometric methods. In this medium, biofilm production by C. albicans isolates was significantly less frequent (8%) than that by non-C. albicans Candida species (61%; P < 0.0001). The overall proportion of non-C. albicans Candida species isolates from the blood that produced biofilms was significantly higher than that of non-C. albicans Candida isolates obtained from other sites (79% versus 52%; P = 0.0001). Bloodstream isolates of C. parapsilosis alone were significantly more likely to be biofilm positive than were C. parapsilosis isolates from other sites (86% versus 47%; P = 0.0032). Non-C. albicans Candida species, including C. parapsilosis, were more likely to be biofilm positive if isolates were derived from patients whose candidemia was central venous catheter (CVC) related (95%; P < 0.0001) and was associated with the use of total parenteral nutrition (TPN) (94%; P < 0.005). These data suggest that the capacity of Candida species isolates to produce biofilms in vitro in glucose-containing SDB may be a reflection of the pathogenic potential of these isolates to cause CVC-related fungemia in patients receiving TPN.

Biofilms↗
PubMed2006

Distribution of bacterial proteins in biofilms formed by non-typeable Haemophilus influenzae.

The ability to preserve the fragile ultrastructural organization of bacterial biofilms using cryo-preparation methods for electron microscopy has enabled us to probe sections through non-typeable Haemophilus influenzae (NTHi) biofilms and determine the localization of NTHi-specific lipooligosaccharide (LOS) and proteins within these structures. Some of the proteins we examined are currently being considered as candidates for vaccine development, so it is important that their distribution and accessibility within the biofilms formed by NTHi be determined. We have localized LOS to the extracellular matrix (ECM) of the biofilm and the P6 outer membrane protein to the membrane of what appear to be viable bacteria within the biofilm. The Hap and HWM1/HMW2 adhesive proteins were associated with bacteria within the biofilm and were present in the biofilm ECM. The IgA1 protease is a secreted protein that was also associated with NTHi in the biofilm and was in the ECM, but was more concentrated in the top region of the biofilm, suggesting a role in protecting biofilm bacteria from antibody attack.

Adhesins, Bacterial↗
PubMed2025

Analysis of gene expression within individual cells reveals spatiotemporal patterns underlying Vibrio cholerae biofilm development.

Bacteria commonly exist in multicellular, surface-attached communities called biofilms. Biofilms are central to ecology, medicine, and industry. The Vibrio cholerae pathogen forms biofilms from single founder cells that, via cell division, mature into three-dimensional structures with distinct, yet reproducible, regional architectures. To define mechanisms underlying biofilm developmental transitions, we establish a single-molecule fluorescence in situ hybridization (smFISH) approach that enables accurate quantitation of spatiotemporal gene-expression patterns in biofilms at cell-scale resolution. smFISH analyses of V. cholerae biofilm regulatory and structural genes demonstrate that, as biofilms mature, overall matrix gene expression decreases, and simultaneously, a pattern emerges in which matrix gene expression becomes largely confined to peripheral biofilm cells. Both quorum sensing and c-di-GMP-signaling are required to generate the proper temporal pattern of matrix gene expression. Quorum sensing signaling is uniform across the biofilm, and thus, c-di-GMP-signaling alone sets the regional matrix gene expression pattern. The smFISH strategy provides insight into mechanisms conferring particular fates to individual biofilm cells.

Biofilms↗
PubMed2005

Airway biofilms: implications for pathogenesis and therapy of respiratory tract infections.

The differentiation of bacterial biofilms in the airway environment, the pathogenesis of airway biofilm, and possible therapeutic methods are discussed. Biofilm diseases that characteristically involve the respiratory system include cystic fibrosis (CF), diffuse panbronchiolitis (DPB), and bronchiectasia with Pseudomonas aeruginosa (P. aeruginosa) infection. There is evidence to suggest that almost all strains of P. aeruginosa have the genetic capacity to synthesize alginate, a main matrix of biofilms, when ecological conditions are unfavorable for their survival. The bacteria inside the mature biofilm show increased resistance to both antibacterials and phagocytic cells, express fewer virulence factors because of their stationary state of growth, and are less stimulatory to the mucosa because of the 'sandwich binding'. These factors facilitate both the colonization of bacteria and their extended survival even under unfavorable conditions. Since the biofilm limits colonization to a latent form, the clinical symptoms in this situation are unremarkable. However, the clinical progression of both CF and DPB proceeds in two characteristic directions. The first is an acute exacerbation caused by planktonic bacteria that have germinated from the biofilm. The second is a slow progression of disease that is induced by harmful immune reactions. The harmful reactions are mediated by alginate, which induces antigen antibody reactions around the airways, as well as formation of circulating immune complexes that are deposited on lung tissue. Furthermore, the highest titer of bacterial permeability increasing anti-neutrophil cytoplasmic autoantibodies (BPI-ANCA) is observed in association with highly impaired pulmonary function in patients with CF and DPB, as well as in patients with a lengthy period of colonization with P. aeruginosa. BPI-ANCA subsequently makes chronic airway infection even more intractable. The long-term use of 14- or 15-ring membered macrolides results in a favorable clinical outcome for patients with DPB and in some patients with CF. In the last 10 years, an increasing number of studies have reported secondary actions of macrolides that include effects on both airway and phagocytic cells, as well as an anti-biofilm activity. The 14- or 15-ring membered macrolides inhibit: (i) the alginate production from P. aeruginosa; (ii) the antibody reaction to alginate, which leads to a decrease in the immune complex formation; and (iii) the activation of the autoinducer 3-O-C12-homoserine lactone and subsequent expression of lasI and rhlI in quorum sensing systems in P. aeruginosa. These anti-biofilm actions of macrolides may represent their basic mechanisms of action on airway biofilm disease.

Anti-Bacterial Agents↗
PubMed2006

Coliforms and other microbial indicators occurrence in water and biofilm in full-scale distribution systems.

Biofilm and microbial water quality were studied in four middle size full-scale distribution systems (DS) in France serving 5,000-30,000 inhabitants (maximum residence time 23-160h) through three sampling campaigns over 1 year. Three of these DSs were chosen because of a quite high occurrence of bacterial indicators (i.e. total coliforms), the last DS was considered as a reference. Biofilm was studied on cast iron coupons incubated for more than 1 month in devices continuously fed with water from the DS in conditions imitating those met in DS. The devices were located at different points (4-6) along each DS. The abundance of bacteria in biofilm was estimated by heterotrophic plate counts (HPC) after detachment of the biofilm from the support by sonication. Microbiological water quality was estimated in parallel; analysis of total coliforms, E. coli, enterococci and anaerobic sulphide-reducing bacteria spores (ASRB spores) was carried out in biofilm and water. Over the period of the study, 171 water samples and 57 biofilm samples were collected. Over these 171 waters, 19 (11%) were positive for at least one of the measured indicators while two biofilm samples were positive (3.5%). Significant differences were observed in the levels of contamination between the DSs. High residence time in the DS, low disinfectant residual and high temperature increased the risk of indicator occurrence in the water phase. Due to the low number of biofilm samples positive for bacterial indicators, the data collected in the present study did not allow observation of a direct association between biofilm and water contaminations, even if the occurrence of indicators in water appeared on DSs with the highest density of biofilm (HPC).

Biofilms↗
PubMedDate not supplied

Use of an in vitro assay for determination of biofilm-forming capacity of bacteria in chronic rhinosinusitis.

BACKGROUND: Bacterial biofilms are increasingly implicated in the pathogenesis of chronic disease and have been established in several chronic ear, nose, and throat conditions, including chronic sinusitis (CRS). However, this relies on specialized imaging methods not widely available. We wished to assess the capacity of an easily performed, inexpensive in vitro test to assess biofilm production by bacteria recovered from individuals with CRS with or without nasal polyposis. METHODS: Bacterial isolates were recovered from patients consulting an academic tertiary rhinology practice. Biofilm formation was determined with an in vitro staining method using crystal violet. Ten isolates of Pseudomonas aeruginosa, Staphylococcus aureus, and 11 of coagulase-negative staphylococcus from patients with CRS having previously undergone endoscopic sinus surgery for >1 year were assessed. Samples were cultured 24 hours at 37 degrees C on 96-well plates in tryptic soy broth 0.5% glucose medium. After staining with crystal violet, optical density at 570 nm was measured to quantify biofilm production. Biofilm-forming capacity was compared with positive and negative controls for each species obtained from commercial sources. RESULTS: Positive controls all grew biofilms, with a tendency of lesser biofilm formation at higher dilutions. Twenty-two of 31 clinical samples produced a biofilm greater or equal to the positive control. Biofilm was recovered consistently for all three species studied. CONCLUSION: This in vitro assessment method is capable of detecting biofilm-forming capacity in bacteria recovered from individuals with CRS. This simple assay may be a useful complement to existing techniques for clinical research.

Bacteria↗
PubMed2005

The exopolysaccharide alginate protects Pseudomonas aeruginosa biofilm bacteria from IFN-gamma-mediated macrophage killing.

The ability of Pseudomonas aeruginosa to form biofilms and cause chronic infections in the lungs of cystic fibrosis patients is well documented. Numerous studies have revealed that P. aeruginosa biofilms are highly refractory to antibiotics. However, dramatically fewer studies have addressed P. aeruginosa biofilm resistance to the host's immune system. In planktonic, unattached (nonbiofilm) P. aeruginosa, the exopolysaccharide alginate provides protection against a variety of host factors yet the role of alginate in protection of biofilm bacteria is unclear. To address this issue, we tested wild-type strains PAO1, PA14, the mucoid cystic fibrosis isolate, FRD1 (mucA22+), and the respective isogenic mutants which lacked the ability to produce alginate, for their susceptibility to human leukocytes in the presence and absence of IFN-gamma. Human leukocytes, in the presence of recombinant human IFN-gamma, killed biofilm bacteria lacking alginate after a 4-h challenge at 37 degrees C. Bacterial killing was dependent on the presence of IFN-gamma. Killing of the alginate-negative biofilm bacteria was mediated through mononuclear cell phagocytosis since treatment with cytochalasin B, which prevents actin polymerization, inhibited leukocyte-specific bacterial killing. By direct microscopic observation, phagocytosis of alginate-negative biofilm bacteria was significantly increased in the presence of IFN-gamma vs all other treatments. Addition of exogenous, purified alginate to the alginate-negative biofilms restored resistance to human leukocyte killing. Our results suggest that although alginate may not play a significant role in bacterial attachment, biofilm development, and formation, it may play an important role in protecting mucoid P. aeruginosa biofilm bacteria from the human immune system.

Alginates↗
PubMed2002

Survival of Campylobacter jejuni in biofilms isolated from chicken houses.

Campylobacter jejuni is a thermophilic and microaerophilic enteric pathogen associated with poultry. Biofilms may be a source of C. jejuni in poultry house water systems since they can protect constituent microorganisms from environmental stress. In this study, the viability of C. jejuni in biofilms of gram-positive chicken house isolates (P1, Y1, and W1) and a Pseudomonas sp. was determined using a cultural method (modified brucella agar) and direct viable count (DVC). Two-day biofilms grown on polyvinyl chloride (PVC) coupons in R2A broth at 12 and 23 degrees C were incubated with C. jejuni for a 6-h attachment period. Media were then refreshed every 24 h for 7 days to allow biofilm growth. Two-day biofilms of P1, Y1, and Pseudomonas spp. enhanced attachment (P < 0.01) of C. jejuni (4.74, 4.62, and 4.78 log cells/cm2, respectively) compared to W1 and controls without preexisting biofilm (4.31 and 4.22 log cells/cm2, respectively). On day 7, isolates P1 and Y1 and Pseudomonas biofilms covered 5.4, 7.0, and 21.5% of the surface, respectively, compared to 4.9% by W1. Viable C. jejuni on the surface decreased (P < 0.05) with time, with the greatest reduction occurring on surfaces without a preexisting biofilm. The number of viable C. jejuni determined by DVC was greater than that determined by the cultural method, indicating that C. jejuni may form a viable but nonculturable state within the biofilm. Both DVC and the cultural method indicate that biofilms enhance (P < 0.01) the survival of C. jejuni during incubation at 12 and 23 degrees C over a 7-day period.

Animals↗
PubMed2001

Biofilm structure and mass transfer in a gas phase trickle-bed biofilter.

Mass transport phenomena occurring in the biofilms of gas phase trickle-bed biofilters are investigated in this study. The effect of biofilm structure on mass transfer mechanisms is examined using experimental observation from the operating of biofilters, microelectrode techniques and microscopic examination. Since the biofilms of biofilters used for waste gas treatment are not completely saturated with water, there is not a distinguishable liquid layer outside the biofilm. Results suggest that due to this characteristic, gas phase substrates (such as oxygen or volatile organic compounds) may not be limited by the aqueous phase because transport of the compound into the biofilm can occur directly through non-wetted areas. On the other hand, for substrates that are present only in the liquid phase, such as nitrate, the mass transfer limitation is more serious because of the limited liquid supply. Microscopic observations show that a layered structure with void spaces exists within the biofilm. Oxygen concentration distributions along the depth of the biofilms are examined using an oxygen microelectrode. Results indicate that there are some high dissolved oxygen zones inside the biofilm, which suggests the existence of passages for oxygen transfer into the deeper sections of the biofilm in a gas phase trickle-bed biofilter. Both the low gas-liquid mass transfer resistance and the resulting internal structure contribute to the high oxygen penetration within the biofilms in gas phase trickle-bed biofilters.

Biofilms↗
PubMed2001

Interspecies biofilms of Pseudomonas aeruginosa and Burkholderia cepacia.

The leading cause of morbidity and mortality in cystic fibrosis (CF) continues to be lung infections with Pseudomonas aeruginosa biofilms. Co-colonization of the lungs with P aeruginosa and Burkholderia cepacia can result in more severe pulmonary disease than P. aeruginosa alone. The interactions between P. aeruginosa biofilms and B. cepacia are not yet understood; one possible association being that mixed species biofilm formation may be part of the interspecies relationship. Using the Calgary Biofilm Device (CBD), members of all genomovars of the B. cepacia complex were shown to form biofilms, including those isolated from CF lungs. Mixed species biofilm formation between CF isolates of P. aeruginosa and B. cepacia was readily achieved using the CBD. Oxidation-fermentation lactose agar was adapted as a differential agar to monitor mixed biofilm composition. Scanning electron micrographs of the biofilms demonstrated that both species readily integrated in close association in the biofilm structure. Pseudomonas aeruginosa laboratory strain PAO1, however, inhibited mixed biofilm formation of both CF isolates and environmental strains of the B. cepacia complex. Characterization of the soluble inhibitor suggested pyocyanin as the active compound.

Biofilms↗
PubMedDate not supplied

[Biofilm formation by different strains of Salmonella typhimurium in artificial systems].

The ability of 14 different strains of Salmonella typhimurium to biofilm formation depending on genotype and culture conditions was investigated in artificial systems: in 96-well plastic microtitre plates, plastic and glass tubes, plastic Petri dishes and on microscope glasses. Quantitative biofilm growth was monitored by using an assay based on crystal violet staining, while planctonic growth in the same cultures was monitored by absorbance in iEMS Reader MF, and qualitatively--by digital photo and visually. Optimal rate between growth and biofilm indications for all strains was determined at initial cell concentration 10(6-7) KOE/ml and culture incubation at t degrees 28 degrees C. The nutrient content of the medium significantly influenced the quantity of produced biofilm. The nutrient broth LB without NaCl was more effective in promoting biofilm formation, than LB itself. The least quantity of biofilm was formed in water. The genotype of the strains also critically influenced the quantity of produced biofilm. Nonmotile mutants cells had reduced ability to form biofilm. RpoS mutant cells produced significantly less biofilm as compared with cells of isogenic parent strains. The chemical content of plastic and glass also influenced biofilm formation.

Bacterial Proteins↗
PubMed1999

Phylogenetic Composition, Spatial Structure, and Dynamics of Lotic Bacterial Biofilms Investigated by Fluorescent in Situ Hybridization and Confocal Laser Scanning Microscopy.

> Abstract The phylogenetic composition, three-dimensional structure and dynamics of bacterial communities in river biofilms generated in a rotating annular reactor system were studied by fluorescent in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM). Biofilms grew on independently removable polycarbonate slides exposed in the reactor system with natural river water as inoculum and sole nutrient and carbon source. The microbial biofilm community developed from attached single cells and distinct microcolonies via a more confluent structure characterized by various filamentous bacteria to a mature biofilm rich in polymeric material with fewer cells on a per-area basis after 56 days. During the different stages of biofilm development, characteristic microcolonies and cell morphotypes could be identified as typical features of the investigated lotic biofilms. In situ analysis using a comprehensive suite of rRNA-targeted probes visualized individual cells within the alpha-, beta-, and gamma-Proteobacteria as well as the Cytophaga-Flavobacterium group as major parts of the attached community. The relative abundance of these major groups was determined by using digital image analysis to measure specific cell numbers as well as specific cell area after in situ probing. Within the lotic biofilm community, 87% of the whole bacterial cell area and 79% of the total cell counts hybridized with a Bacteria specific probe. During initial biofilm development, beta-Proteobacteria dominated the bacterial population. This was followed by a rapid increase of alpha-Proteobacteria and bacteria affiliated to the Cytophaga-Flavobacterium group. In mature biofilms, alpha-Proteobacteria and Cytophaga-Flavobacteria continued to be the prevalent bacterial groups. Beta-Proteobacteria constituted the morphologically most diverse group within the biofilm communities, and more narrow phylogenetic staining revealed the importance of distinct phylotypes within the beta1-Proteobacteria for the composition of the microbial community. The presence of sulfate-reducing bacteria affiliated to the Desulfovibrionaceae and Desulfobacteriaceae confirmed the range of metabolic potential within the lotic biofilms.http://link.springer-ny.com/link/service/journals/00248/bibs/37n4p225.html

Journal Article↗
PubMed1994

Incidence and nature of peritoneal catheter biofilm determined by electron and confocal laser scanning microscopy.

Thirty-two Tenckhoff catheters retrieved from continuous ambulatory peritoneal dialysis patients with a history of peritonitis were examined for microbial biofilm. Confocal laser scanning microscopy was successfully employed to visualize bacteria in biofilm occluded from view by scanning electron microscopy. Occluded but viable microbial biofilm was associated with 17 (81%) catheters from patients free from infection following renal transplant. Mixed isolate biofilm with two or more isolates of coagulase-negative staphylococci or Staphylococcus aureus was found on 41% of these catheters. Clearly visible viable biofilm consisting exclusively of Pseudomonas aeruginosa occurred on all four catheters removed due to recurrent peritonitis. Five (71%) catheters retrieved from patients transferred to haemodialysis had viable biofilm. Antibiotic sensitivities of the biofilm isolates were similar in profile to those reported for non-biofilm isolates from infected dialysate. Persistence of catheter biofilm despite direct contact with therapeutic levels of antibiotics in peritoneal dialysate requires that attention be directed towards improving antibiotic efficacy against peritonitis-causing bacteria in biofilm form.

Bacterial Adhesion↗
PubMed1994

Vancomycin penetration into biofilm covering infected prostheses and effect on bacteria.

To evaluate the adequacy of penetration of antibiotics into biofilm, a novel in vitro model for prosthesis-related infection was developed. Sterile stainless steel orthopedic nuts were incubated with slime-producing Staphylococcus epidermidis. Biofilm-covered nuts were exposed to varying concentrations of vancomycin; then biofilms were harvested. Vancomycin levels in biofilm, as measured by fluorescent polarization immunoassay, far exceeded the MIC and MBC of vancomycin for the organism. Bacterial growth in biofilm was inversely related to vancomycin concentration in biofilm, but even extremely high drug concentrations did not eradicate bacteria embedded in biofilm. The MICs and MBCs for bacteria recovered from biofilm did not differ from those for incubating organisms. Thus, failure of glycopeptide antibiotics to cure prosthesis-related infection is not due to poor penetration of drugs into biofilm but likely due to diminished antimicrobial effect on bacteria in the biofilm environment.

Bioprosthesis↗
PubMed1994

Bacterial biofilm in chronic airway infection.

We hypothesized that bacterial biofilm formation could be an important factor that makes some infections intractable, and conducted the following study to confirm the role of bacterial biofilm in airway infection. We first microscopically examined airway surface in patients with an intractable airway infection and detected bacterial biofilms adhering to the airway surface. Most of the airway biofilm diseases were diffuse panbronchiolitis and bronchiectasia due to Pseudomonas aeruginosa or Klebsiella pneumoniae. In vivo examination revealed that chemotaxis of neutrophils in patients with biofilm bacteria was less than that in patients with floating type bacteria. Interaction of Pseudomonas biofilm with antibacterial agents was examined in vitro. The rate of survival of biofilm bacteria was higher than that of floating bacteria in contact with twice the minimal bactericidal concentration of ciprofloxacin (CPFX) or two to 10 times the minimal inhibitory concentration of cefclidin and meropenem which are highly potent antibacterial agents against P. aeruginosa. Additionally, the effects of clarithromycin (CAM) on biofilm bacteria were studied in order to investigate new therapeutic maneuvers against a bacterial biofilm. Also, the combination of CPFX and CAM was more effective in decreasing the bacterial survival rate than CPFX alone. The results suggest that administration CAM can be one of the therapeutic maneuvers against biofilm bacteria.

Animals↗
PubMed1991

Bacterial species dominance within a binary culture biofilm.

Studies with two species of bacteria, Pseudomonas putida and Hyphomicrobium sp. strain ZV620, were carried out to evaluate the overall net rate of accumulation of biofilm, the biofilm species composition, and individual species shear-related removal rates. Bacterial cells of either or both species were deposited onto glass or biofilm surfaces to initiate multispecies biofilms. Subsequent biofilm development was carried out under known conditions of nutrient concentration and laminar flow. Establishment of a depositing organism in a biofilm composed of another species was found to be a function of the relative growth rates of the bacterial species. In the case of simultaneous species deposition and subsequent binary culture development, the faster-growing organisms rapidly became the dominant biofilm species, but the slower-growing organisms remained established within the biofilm and continued to increase in numbers over time. The results also indicated that the rate of cell removal by fluid shear for a species was a function of biofilm cell number only if the species concentration was uniform with depth; in essence, only the upper layers of the biofilm were sheared off.

Bacteria↗
PubMed1998

A technique To quantify the population size and composition of the biofilm component in communities of bacteria in the phyllosphere

The presence of microbial biofilms in the phyllosphere of terrestrial plants has recently been demonstrated, but few techniques to study biofilms associated with living plant tissues are available. Here we report a technique to estimate the proportion of the bacterial population on leaves that is assembled in biofilms and to quantitatively isolate bacteria from the biofilm and nonbiofilm (solitary) components of phyllosphere microbial communities. This technique is based on removal of bacteria from leaves by gentle washing, separation of biofilm and solitary bacteria by filtration, and disintegration of biofilms by ultrasonication. The filters used for this technique were evaluated for their nonspecific retention rates of solitary bacteria and for the efficiency of filtration for different concentrations of solitary bacteria in the presence of biofilms and other particles. The lethality and efficiency of disintegration of the sonication conditions used here were also evaluated. Isolation and quantification of bacteria by this technique is based on use of culture media. However, oligonucleotide probes, sera, or epifluorescent stains could also be used for direct characterization of the biofilm and solitary bacteria in the suspensions generated by this technique. Preliminary results from estimates of biofilm abundance in phyllosphere communities show that bacteria in biofilms constitute between about 10 and 40% of the total bacterial population on broad-leaf endive and parsley leaves.

Journal Article↗
PubMed1994

Biofilm formation by Candida species on the surface of catheter materials in vitro.

A model system for studying Candida biofilms growing on the surface of small discs of catheter material is described. Biofilm formation was determined quantitatively by a colorimetric assay involving reduction of a tetrazolium salt or by [3H]leucine incorporation; both methods gave excellent correlation with biofilm dry weight (r = 0.997 and 0.945, respectively). Growth of Candida albicans biofilms in medium containing 500 mM galactose or 50 mM glucose reached a maximum after 48 h and then declined; however, the cell yield was lower in low-glucose medium. Comparison of biofilm formation by 15 different isolates of C. albicans failed to reveal any correlation with pathogenicity within this group, but there was some correlation with pathogenicity when different Candida species were tested. Isolates of C. parapsilosis (Glasgow), C. pseudotropicalis, and C. glabrata all gave significantly less biofilm growth (P < 0.001) than the more pathogenic C. albicans. Evaluation of various catheter materials showed that biofilm formation by C. albicans was slightly increased on latex or silicone elastomer (P < 0.05), compared with polyvinyl chloride, but substantially decreased on polyurethane or 100% silicone (P < 0.001). Scanning electron microscopy demonstrated that after 48 h, C. albicans biofilms consisted of a dense network of yeasts, germ tubes, pseudohyphae, and hyphae; extracellular polymeric material was visible on the surfaces of some of these morphological forms. Our model system is a simple and convenient method for studying Candida biofilms and could be used for testing the efficacy of antifungal agents against biofilm cells.

Candida↗