Showing papers on "Biofilm published in 1992"

Prevention and control of bacterial infections associated with medical devices.

Abstract: Bacteria that grow in association with medical devices always form slime enclosed biofilms, within which they are protected, to a large extent, from the bactericidal activity of chemical biocides and antibiotics. Mature biofilms (> 7 days) are demonstrably resistant to 500-5,000 times the concentrations of these agents than are necessary to kill free floating (planktonic) cells of the same organism. The authors have discovered that this well established inherent resistance of biofilm bacteria to antibacterial agents can be completely obviated if these agents are applied to these adherent populations within an electric field. The killing of biofilm bacteria by antibiotics can be dramatically enhanced by relatively weak electric fields (1.5 V/cm and 15 microA/cm2) that, in themselves, have no deleterious effects on these slime protected populations adherent to plastic or metal surfaces. This bioelectric technology can readily be used to enhance the preimplantation sterilization of medical devices by biocides. The authors suggest that it may also be used to control biofilm formation and consequent infection by electrically enhanced perioperative antibiotic prophylaxis and by electrically enhanced penetration of antibiotics to kill the biofilm bacteria that form the inherently resistant nidus of chronic device related infections.

Biofilm formation in the industry: A review

Abstract: Biofilm and biofouling refer to biological deposits on any surface. Biofilms consist of both microbes and their extracellular products, usually polysaccharides. The purpose of biofilm is to protect the microbes from hostile environments or to act as a trap for nutrient acquisition. Biofilm formation causes problems in many branches of industry, such as in industrial water systems and the medical and process industries. Besides causing problems in cleaning and hygiene, biofilm may cause energy losses and blockages in condenser tubes, cooling fill materials, water and wastewater circuits, and heat exchange tubes, and on ship hulls. Biofilm can also present microbial risks due to the release of pathogens from cooling towers or by reducing water quality in drinking water distribution systems. In the medical industry biofilm is referred to as glycocalyx when diseases of the lungs or the gastrointestinal or urinary tract are involved.

Development and experimental evaluation of a steady‐state, multispecies biofilm model

Abstract: A steady-state model for quantifying the space competition in multispecies biofilms is developed. The model includes multiple active species, inert biomass, substrate utilization and diffusion within the biofilm, external mass transport, and detachment phenomena. It predicts the steady-state values of biofilm thickness, species distribution, and substrate fluxes. An experimental evaluation is carried out in completely mixed biofilm reactors in which slow-growing nitrifying bacteria compete with acetate-utilizing heterotrophs. The experimental results show that the model successfully describes the space competition. In particular, increasing acetate concentrations causes NH(4) (+)-N fluxes to decrease, because nitrifiers are forced deeper into the biofilm, where they experience greater mass-transport resistance.

Immunogold and fluorescein immunolabelling of Legionella pneumophila within an aquatic biofilm visualized by using episcopic differential interference contrast microscopy.

Abstract: Biofilms containing diverse microflora were developed in tap water on glass and polybutylene surfaces Legionella pneumophila within the biofilms was labelled with monoclonal antibodies and visualized with immunogold or fluorescein isothiocyanate conjugates Development of a differential interference contrast technique in an episcopic mode enabled simultaneous visualization of the total biofilm flora and gold-labelled legionellae The legionellae occurred in microcolonies within the biofilm in the absence of amoebae, suggesting that the bacterial consortium was supplying sufficient nutrients to enable legionellae to grow extracellularly within the biofilm

Dynamic interactions of biofilms of mucoid Pseudomonas aeruginosa with tobramycin and piperacillin.

Abstract: The dynamic interaction of planktonic and biofilm cells of mucoid Pseudomonas aeruginosa with tobramycin and piperacillin was investigated in a chemostat system. The results indicated that planktonic and young biofilm cells of the 2-day-old chemostat culture of P. aeruginosa were susceptible to killing by chemostat-controlled doses of either 250 micrograms of piperacillin per ml plus 5 micrograms of tobramycin per ml or 500 micrograms of piperacillin per ml plus 5 micrograms of tobramycin per ml. Complete eradication of the planktonic and young biofilm cells was observed after exposure of the cells to six chemostat-controlled doses of these antibiotic at 8-h intervals for 7 days. Regrowth of the organism was not observed after the termination of antibiotic therapy on day 7. A different picture was observed when antibiotic treatment was initiated on day 10 after inoculation. Viable old biofilm cells were reduced to approximately 20% after exposure to the chemostat-controlled doses of 500 micrograms of piperacillin per ml plus 5 micrograms of tobramycin per ml. Complete eradication of old biofilm cells could not be achieved, and regrowth of the organism occurred after the termination of antibiotic therapy. These data suggest that young biofilm cells of mucoid P. aeruginosa can be effectively eradicated with the combination of piperacillin and tobramycin, while old biofilm cells are very resistant to these antibiotics and eradication of old biofilm cells is not achievable with the chemostat-controlled doses of piperacillin and tobramycin used in this study.

Effect of biofilm culture upon the susceptibility of Staphylococcus epidermidis to tobramycin

Abstract: Biofilms of Staphylococcus epidermidis were cultured at various specific growth rates, and susceptibilities to tobramycin were compared with those of equivalent plank-tonic populations. In all instances, susceptibility increased significantly with increasing specific growth rate. However, resuspension of the biofilms increased susceptibility, suggesting some involvement of the glycocalyx in reducing antibiotic permeation of the biofilm. Cells that dispersed spontaneously from the biofilms at steady state were particularly susceptible to this agent. Since such cells correspond to newly-divided daughter cells, the relationship between tobramycin susceptibility and the phase in the division cycle was investigated. Susceptibility was enhanced in cultures dividing synchronously shortly before, during and shortly after cell separation. Perfusion of actively-growing S. epidermidis biofilms with tobramycin also demonstrated increased susceptibility with increasing growth rate, but also showed rapid recovery following removal of the agent.

Scanning electron microscopy of bacterial biofilms on indwelling bladder catheters.

Abstract: Fifty Foley bladder catheters that had been indwelling for periods ranging from 3 to 83 days (mean 35 days) were examined for the presence of bacterial biofilm. Scanning electron microscopy on freeze-dried cross-sections and fixed, critical point-dried longitudinal sections revealed biofilm formation on the luminal surfaces of 44 of the catheters. Culture of urine samples and sonicates from catheters revealed that the prevalence of bacteriuria was less than that of catheter colonization. A wide range of nosocomial species were found colonizing the catheters,Escherichia coli being most often isolated. The bacterial composition of the biofilms ranged from single species to mixed communities containing up to four species. There was no relationship between the length of time that the catheter had been in situ and the extent of biofilm formation. The biofilms varied in thickness from 3 to 490 µm and were visible as layers of bacterial cells up to about 400 cells deep, embedded in a matrix.

Growth-rate-independent killing by ciprofloxacin of biofilm-derived Staphylococcus epidermidis evidence for cell-cycle dependency

Abstract: Cell culture methods that allow culture of Staphylococcus epidermidis biofilms at controlled growth rates were used to examine susceptibility to ciprofloxacin. Changes in biofilm susceptibility, dependent upon growth rate, were compared with those for suspended populations grown in chemostat, and also for newly-formed daughter cells shed from the biofilm during its growth and development. Susceptibility increased for intact and resuspended biofilms, and also for planktonic cultures, with increases in growth rate. The dependence of susceptibility upon growth rate was greatest for slow growing cells (mu, 0.01-0.15/h). At any particular growth rate, biofilms appeared more susceptible than their planktonic counterparts. Newly-formed daughter cells were relatively tolerant to ciprofloxacin at all rates of growth. Lack of growth rate dependency for the newly-formed cells suggested a role for the cell-division cycle in determining resistance. This was confirmed by examining the susceptibility of S. epidermidis throughout batch cultures with cell division synchronized. Perfusion of various steady-state biofilms with ciprofloxacin demonstrated killing of the adherent population even at much reduced rates of growth.

Biofilm reduction method

Abstract: A method of killing microorganisms which form a biofilm on a tissue or implant surfaces in a patient, and Which are refractory to a biocide at a dose which effective to kill the microorganism in planktonic form. The effect of the biocide is potentiated, to an effective killing level, by applying an electric field across the surface containing the biofilm.

Eradication of biofilm cells of Staphylococcus aureus with tobramycin and cephalexin.

Abstract: The kinetics of growth and formation of biofilm by Staphylococcus aureus were investigated under iron-limited conditions in the chemostat. The population of planktonic cells reached 5.5 x 10(9) cells/mL 24 h after inoculation (D = 0.05 h-1) and remained constant throughout. The number of biofilm cells of S. aureus colonizing the silicone tubing increased exponentially from 6 x 10(4) to 2.7 x 10(7) cells/cm2 (6 days later) and continued to increase at a reduced rate to 2.7 x 10(8) cells/cm2 on day 13. Planktonic cells of S. aureus were susceptible to tobramycin and cephalexin. The planktonic cells could be successfully eradicated with a combination of 5 micrograms tobramycin plus 100 micrograms cephalexin per millilitre. Exposure of young biofilm cells of S. aureus to 5 micrograms tobramycin plus 100 micrograms cephalexin per millilitre resulted in a rapid loss of cell viability. The percentage of survival dropped to less than 0.0001% after exposure to these concentrations of antibiotics for 3 h. Old biofilm cells of S. aureus were found to be extremely resistant to these antibiotics. The cell viability was reduced to 0.09% after exposure to 10 micrograms tobramycin plus 100 micrograms cephalexin per millilitre. The results suggest that it is possible to eradicate S. aureus infection at the early stage with tobramycin plus cephalexin. Any delay in implementing antibiotic therapy is likely to result in the failure of the treatment. It is important to note that the concentrations of antibiotics required for the eradication of young biofilm cells must be determined for the treatment of device-associated infections.

Susceptibility of biofilm cells of Pseudomonas aeruginosa to bactericidal actions of whole blood and serum.

Abstract: The planktonic and young biofilm cells (harvested on day 2) of mucoid Pseudomonas aeruginosa were susceptible to the bactericidal actions of whole blood and serum. Aging biofilms of this organism (harvested on day 7) were very resistant to the killing effect of whole blood and serum. From this study we propose that the establishment of aging biofilms may contribute to persistence of this organism in biofilm-associated infections.

Extracellular Polymers in Biofilms

Abstract: Many of those who study biofilms view them as a collection of living organisms at an interface but this definition should be expanded to include the products of those organisms. A major product is the matrix in which biofilm cells are found. It is somewhat surprising that there is such an emphasis on the biotic component of the film because this phase occupies only a small fraction of the volume (Characklis & Cooksey, 1983). It is often the biofilm matrix that causes many of the economic problems associated with biofilm formation since it acts as a layer of immobilized water. It is in fact highly hydrated and contains 98–99% water (Christensen and Characklis, 1990). This matrix, which is really a collection of polymers rather than a single material, is made by many organisms in biofilms. The polymers have been referred to collectively as capsules, sheaths, slime and glycocalyces. Costerton et al (1981) proposed the term glycocalyx for use in procaryotic biology. They defined a glycocalyx as “those polysaccharide-containing structures of bacterial origin, lying outside the integral elements of the outer membrane of Gram-negative cells and the peptidoglycan of Gram-positive cells”. They further subdivided glycocalyces into (1) glycoprotein subunits at the cell surface and (2) capsules. “Capsules” were further subdivided into (a) those that are rigid and exclude particles such as Indian ink ( a classical negative “stain” in bacteriology); (b) those, which in contrast to (a), are flexible and include Indian ink; (c) integral capsules that are closely associated with the cell surface and (d) those capsules that are peripheral to the cell and can be lost to the aqueous phase. In a brief but comprehensive review (Geesey, 1982), Geesey used a less structured term for the high molecular weight material extracellular to cells.

Measurements of the distribution of adenylate concentrations and adenylate energy charge across Pseudomonas aeruginosa biofilms.

Abstract: Adenine nucleotide pools and adenylate energy charge distributions were determined by using a laboratory-generated quasi-steady-state Pseudomonas aeruginosa biofilm. The method used involved freezing and sectioning of the intact biofilm, followed by extraction and assay of the adenylates in the sectioned material. Results indicated an increase in adenylate energy charge of about 0.2 units from the bottom to the surface of the biofilm. However, energy charge values were generally low throughout the biofilm, reaching a maximum of only 0.6 units. Of the adenylates measured, AMP was the predominant nucleotide, especially in the deeper parts of the biofilm profile.

Encyclopedia of microbiology

Abstract: Contents by Subject Area. Preface. From the Preface to the First Edition. Guide to the Encyclopedia. Acknowledgments. VOLUME 1 - A-C: ABC Transport. Acetic Acid Production. Acetogenesis and Acetogenic Bacteria. Actinomycetes. Adhesion, Bacterial. Aerobic Respiration: Oxidases and Globins. Aerosol Infections. Agrobacterium. Agrobacterium and Plant Cell Transformation. AIDS, Historical. Airborne Microorganisms and Indoor Air Quality. Alkaline Environments. Amino Acid Function and Synthesis. Amino Acid Production. Aminoglycosides, Bioactive Bacterial Metabolites. Amylases, Microbial. Anaerobic Respiration. Antibiotic Biosynthesis. Antibodies and B Cells. Antifungal Agents. Antigenic Variation. Antisense RNAs. Antiviral Agents. Arboviruses. Archaea. Arsenic. Attenuation, Transcriptional. Autotrophic CO2 Metabolism. Metabolism. Azotobacter. Bacillus subtilis, Genetics. Bacteriocins. Bacterophages. Beer/Brewing. Beet Necrotic Yellow Vein Virus. Biocatalysis for Synthesis of Chiral Pharmaceutical Intermediates. Biocides. Biodegradation. Biodeterioration: In Wood, Architecture, Art, and Other Media. Biofilms and Biofouling. Biological Control of Weeds. Biological Nitrogen Fixation. Biological Warfare. Bioluminescence, Microbial. Biomonitors of Environmental Contamination by Microorganisms. Biopesticides, Microbial. Biopolymers, Production and Uses of. Bioreactor Monitoring and Control. Bioreactors. Bioremediation. Biosensors. Biosurfactants. Biotransformations. Carbohydrate Synthesis and Metabolism. Carbon and Nitrogen Assimilation, Regulation of. Careers in Microbiology. Caulobacter, Genetics. Cell Division, Prokaryotes. Cell Membrane: Structure and Function. Cellular Immunity. Cellulases. Cell Walls, Bacterial. Chemotaxis. Chlamydia. Cholera. Cholera, Historical. Chromosome, Bacterial. Chromosome Replication and Segregation. Clostridia. Coenzyme and Prosthetic Group Biosynthesis. Conjugation, Bacterial. Conservation of Cultural Heritage. Continuous Culture. Cosmetic Microbiology. Crystalline Bacterial Cell Surface Layers. Cyanobacteria. VOLUME 2 - D-K: Dairy Products. Detection of Bacteria in Blood: Centrifugation and Filtration. Developmental Processes in Bacteria. Diagnostic Microbiology. Dinoflagellates. Diversity, Microbial. DNA Repair. DNA Replication. DNA Restriction and Modification. DNA Sequencing and Genomics. Downy Mildews. Ecology, Microbial. Economic Consequences of Infectious Diseases. Education in Microbiology. Emerging Infections. Energy Transduction Processes: From Respiration to Photosynthesis. Enteropathogenic Bacteria. Enteroviruses. Enzymes, Extracellular. Enzymes in Biotechnology. ErwiniaL Genetics of Pathogenicity Factors. Escherchia coli, General Biology. Escherchia coli, and Salmonella, Genetics. Evolution, Theory and Experiments. Exobiology. Exotoxins. Extremeophiles. Eyespot. Fermentation. Fermented Foods. Fimbriae, Pili. Flagella. Food-borne Illnesses. Food Spoilage and Preservation. Foods, Quality Control. Freeze-Drying of Microorganisms. Freshwater Microbiology. Fungal Infections, Cutaneous. Fungal Infections, Systemic. Fungi, Filamentous. Gaeumannomyces graminis. Gastrointestinal Microbiology. Genetically Modified Organisms: Guidelines and Regulations from Research. Genomic Engineering of Bacterial Metabolisms. Germfree Animal Techniques. Global Burden of Infectious Diseases. Glycogen Biosynthesis. Glyoxylate Bypass in Escherichia coli. Gram-Negative Anaerobic Pathogens. Gram-Negative Cocci, Pathogenic. Growth Kinetics, Bacterial. Haemophilus influenzae, Genetics. Heat Stress. Heavy Metal Pollutants: Environmental and Biotechnological Aspects. Heavy Metals, Bacterial Resistances. Helicobacter pylori. Hepatitis Viruses. Heterotrophic Microorganisms. High-Pressure Habitats. History of Microbiology. Horizontal Transfer of Genes between Microorganisms. Identification of Bacteria, Computerized. Industrial Biotechnology, Overview. Industrial Effluents: Sources, Properties, and Treatments. Industrial Fermentation Processes. Infectious Waste Management. Influenza Viruses. Insecticides, Microbial. Interferons. International Law and Infectious Disease. Intestinal Protozoan Infections in Humans. Iron Metabolism. VOLUME 3 - L-P: Lactic Acid Bacteria. Lactic Acid, Microbially Produced. Legionella. Leshmania. Lignocellulose, Lignin, Ligninases. Lipases, Industrial Uses. Lipid Biosynthesis. Lipids, Microbially Produced. Lipopolysaccharides. Low-Nutrient Environments. Low-Temperature Environments. Luteoviridae. Lyme Disease. Malaria. Mapping Bacterial Genomes. Meat and Meat Products. Mercury Cycle. Metal Extraction and Ore Discovery. Methane Biochemistry. Methane Production/Agricultural Waste Management. Methanogenesis. Method, Philosophy of. Methylation of Nucleic Acids and Proteins. Methylotrophy. Microbes and the Atmosphere. Microscopy, Confocal. Microscopy, Electron. Microscopy, Optical. Mutagenesis. Mycobacteria. Mycorrhizae. Mycotoxicoses. Myxobacteria. Myxococcus, Genetics. Natural Selection, Bacterial. Nitrogen Cycle. Nitrogen Fixation. Nodule Formation in Legumes. Nucleotide Metabolism. Nutrition of Microorganisms. Oil Pollution. Oncogenic Viruses. Oral Microbiology. Ore Leaching by Microbes. Origin of Life. Osmotic Stress. Outer Membrane, Gram-Negative Bacteria. Oxidative Stress. Paramyxoviruses. Patenting of Living Organisms and Natural Products. Pectinases. PEP: Carbohydrate Phosphotransferase Systems. Pesticide Biodegradation. Phloem-Limited Bacteria. Phosphorus Cycle. Photosensory Behavior. pH Stress. Phytophthora infestans. Phytoplasma. Pigments, Microbially Produced. Plague. Plant Disease Resistance: Natural Mechanisms and Engineered Resistance. Plant Pathogens. Plant Virology, Overview. Plasmids, Bacterial. Plasmids, Catabolic. Plasmodium. Polio. Polyketide Antibiotics. Polymerase Chain Reaction (PCR). Potyviruses. Powderey Mildews. Prions. Protein Biosynthesis. Protein Secretion. Protozoan Predation. Pseudomonas. Pulp and Paper. VOLUME 4 - Q-Z: Quorum Sensing in Gram-Negative Bacteria. Rabies. Ralstonia solanacearum. recA: The Gene and Its Protein Product. Recombinant DNA, Basic Procedures. Refrigerated Foods. Retroviruses. Rhinoviruses. Rhizoctonia. Rhizosphere. Ribosome Synthesis and Regulation. Rickettsiae. RNA Splicing, Bacterial. Rumen Fermentation. Rust Fungi. Secondary Metabolites. Selenium. Sexually Transmitted Diseases. Skin Microbiology. Smallpox. Smuts, Bunts, and Ergot. Soil Dynamics and Organic Matter, Decomposition. Soil Microbiology. SOS Response. Space Flight, Effects on Microorganisms. Spirochetes. Spontaneous Generation. Sporulation. Staphylococcus. Starvation, Bacterial. Stock Culture Collections and Their Databases. Strain Improvement. Streptococcus pneumoniae. Streptomyces, Genetics. Stringent Response. Sulfide-Containing Environments. Sulfur Cycle. Surveillance of Infectious Diseases. Symbiotic Microorganisms in Insects. Syphilis, Historical. Temperature Control. Tetrapyrrole Biosynthesis in Bacteria. Timber and Forest Products. T Lymphocytes. Tospoviruses. Toxoplasmosis. Transcriptional Regulation in Prokaryotes. Transcription, Viral. Transduction: Host DNA Transfer by Bacteriophages. Transformation, Genetic. Transgenic Animal Technology. Translational Control and Fidelity. Transposable Elements. Trypanosomes. Two-Component Systems. Typhoid, Historical. Typhus Fevers and Other Rickettsial Diseases. Vaccines, Bacterial. Vaccines, Viral. Verticillium. Viruses. Viruses, Emerging. Virus Infection. Vitamins and Related Biofactors, Microbial Production. Wastewater Treatment, Industrial. Wastewater Treatment, Municipal. Water-Deficient Environments. Water, Drinking. Wine. Xanthomonas. Xylanases. Yeasts. Zoonoses. Contributors. Glossary. Index.

Some bacterial parameters influencing the neutrophil oxidative burst response to Pseudomonas aeruginosa biofilms

Abstract: Persistence of bacteria in spite of a normal host immune system and relevant antibiotic treatment is a key problem in many chronic infections, such as the bronchopulmonary P. aeruginosa infection in cystic fibrosis patients. The capability of bacteria to establish themselves in microcolonies or biofilms is an important protective mechanism of the microorganisms. We examined the human PMN oxidative burst response to P. aeruginosa in biofilm and in planktonic form. The PMN chemiluminescence response to P. aeruginosa in biofilms was reduced to 30.5-47.5% (p less than 0.04) and the superoxide response to 85.9% (p less than 0.02) of the response to equivalent numbers of planktonic bacteria. Mechanical disruption of the biofilms before the assays elicited a significantly increased response in the chemiluminescence experiments and to nonopsonized biofilms in the superoxide anion experiments. We conclude that biofilm bacteria, although able to stimulate the PMN, result in a reduced, suboptimal response leading to lack of efficient eradication of the bacteria in the chronic infection.

Development and composition of the epixylic biofilm in a blackwater river

Abstract: SUMMARY 1 Comparisons of chlorophyll a, bacterial density, frequencies of dividing cells, ash-free dry mass (AFDM) and extracellular polysaccharide content were made for biofilm developing on wood (Salix) submerged in replicated stream-side flumes exposed to either ambient light (light treatment) or covered to exclude light (dark treatment) Biofilm was sampled on days 3, 6, 9 and 14 during experimental periods occurring irrMay, September, November and December 2 There were no significant differences in bacterial cell densities, frequencies of dividing cells, AFDM or extracellular poiysaccharide content between light and dark treatments Ash content and bacterial biomass was similar to seston, suggesting the importance of seston as a source of material accumulating in the biofilm 3 Of total epixylic organic carbon 72% was estimated to be extracellular polysaccharide, and 08% was bacterial carbon At least nine times more carbon was contained in extracellular polysaccharide than in bacterial biomass 4 In the epixylon of the Ogeechee River, bacterial dynamics appear to be controlled by factors other than the availability of algal substrates

Radiochemical assay to measure the biofilm produced by coagulase-negative staphylococci on solid surfaces and its use to quantitate the effects of various antibacterial compounds on the formation of the biofilm

Abstract: A firmly adherent mass of slime plus organisms (biofilm) accumulates on the sides of culture tubes when some strains of coagulase-negative staphylococci are grown in a chemically-defined medium containing [14C]glucose. This mass was washed (to remove labelled medium) and then counted after adding scintillation fluid. Organisms from the liquid culture were also washed and counted to check that [14C]glucose had been utilised to label the bacteria. Nine strains were examined in this way, and the results were compared with those obtained with four older techniques for recognising slime production or adherent bacteria. The new method is quick, and has advantages of reproducibility and good discrimination between strains; there was a 15-fold difference in counts in the biofilm between slime-producing and non-producing strains respectively. With the new radiolabel assay, the effects of several antibacterial compounds on the build-up of the biofilm were investigated with four slime-producing strains. Tunicamycin, chloramphenicol and 5-fluorouracil, at levels below their minimum growth-inhibitory concentrations, each greatly diminished biofilm formation; several other drugs had less effect.

Repeated cadmium biosorption by regeneratedEnterobacter aerogenes biofilm attached to activated carbon

Abstract: The bacteriumEnterobacter aerogenes has been used to develop a biofilm over activated carbon for biosorption from various strength cadmium solutions (25–500ppm). High bacterial resistance to metal poisoning allowed biofilm regeneration to raise the net loading of cadmium over the carbon by repeated biosorption runs.

Kinetic interaction of biofilm cells of Staphylococcus aureus with cephalexin and tobramycin in a chemostat system.

Abstract: Planktonic and young biofilm cells were completely eradicated after exposure of these cells to drug levels representing one loading and two maintenance doses of tobramycin and cephalexin. A very different picture was observed when antibiotic exposure was initiated on day 21. Complete eradication of the old biofilm cells was not observed even when the antibiotic exposure was continued for an extra 6 days. Regrowth of the organism was observed when the antibiotic exposure was terminated.

Effect of the growth phase of foodborne biofilms on their resistance to a chlorine sanitizer. II

Abstract: The effect of biofilm age of the resistance to a chlorine sanitizer was studied with Pseudomonas fluorescens, Listeria monocytogenes and Bacillus subtilis. The results showed that 24 h was not sufficient for biofilm development and that a minimum of 48 h was necessary for biofilm growth. The micro-organisms were more resistant when the biofilm was produced in milk rather than in meat media. Residual glycocalyx was observed after all the chlorine treatments

Deposition of bacterial cells onto glass and biofilm surfaces

Abstract: Deposition rates of Pseudomonas putida and Hyphomicrobium ZV620 onto glass and biofilm surfaces were quantified. Both species deposited to glass at a much slower rate than to biofilm. A definite bias by depositing cells for biofilms of their own species was evident in the highest attachment rates observed in this study.