BIOTECH 1
What Is Biotechnology?
Biotechnology is technology based on biology, especially when used in agriculture, food science, and medicine.
Of the many different definitions available, the one formulated by the UN Convention on Biological Diversity is one of the broadest:
Biotechnology is any technological application that uses biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use. One section of biotechnology is the directed use of organisms for the manufacture of organic products (examples include beer, milk-products, and skin). Naturally present bacteria are utilized by the mining industry in bioleaching. Biotechnology is also used to recycle, treat waste, clean up sites contaminated by industrial activities (bioremediation), and produce biological weapons.
There are also applications of biotechnology that do not use living organisms. Examples are DNA microarrays used in genetics and radioactive tracers used in medicine.
Modern biotechnology is often associated with the use of genetically altered microorganisms such as E. coli or yeast for the production of substances like insulin or antibiotics. It can also refer to transgenic animals or transgenic plants, such as Bt corn. Genetically altered Mammalian cells, such as Chinese Hamster ovarian cells, are also widely used to manufacture pharmaceuticals. Another promising new biotechnology application is the development of plant-made pharmaceuticals.
There are number of jargon terms for sub-fields of biotechnology.
Red biotechnology is biotechnology applied to medical processes. An example would include an organism designed to produce an antibiotic, or engineering genetic cures to diseases through genomic manipulation.
White biotechnology, also known as grey biotechnology, is biotechnology applied to industrial processes. An example would include an organism designed to produce a useful chemical. White biotechnology tends to consume less resources that traditional processes when used to produce industrial goods.
Green biotechnology is biotechnology applied to agricultural processes. An example would include an organism designed to grow under specific environmental conditions or in the presence (or absence) of certain agricultural chemicals. Green biotechnology tends to produce more environmentally friendly solutions then traditional industrial agriculture. An example of this would include a plant engineered to express a pesticide, thereby eliminating the need for external application of pesticides.
The term blue biotechnology has also been used to describe the marine and aquatic applications of biotechnology, but its use is relatively rare.
Biotechnology timeline:
8000BC Collecting of seeds for replanting. Evidence that Babylonians, Egyptians and Romans used selective breeding (artificial selection) practices to improve livestock.
6000BC Brewing beer, fermenting wine, baking bread with help of yeast
4000BC Chinese made yoghurt and cheese with lactic-acid-producing bacteria
1500 Plant collecting around the world
1800 Nikolai I. Vavilov created comprehensive research on breeding animals
1880 Microorganisms discovered
1856 Gregor Mendel started recombinant plant genetics
1919 Karl Ereky, a Hungarian engineer, first used the word biotechnology
1975 Method for producing monoclonal antibody developed by Kohler and Milstein
1980 Modern biotech is characterized by recombinant DNA technology. The prokaryote model, E. coli, is used to produce insulin and other medicine, in human form. (About 5% of diabetics are allergic to animal insulins available before)
1992 FDA approves of the first GM food from Calgene: "flavor saver" tomato
2000 Completion of the Human Genome Project
Industrial biotechnology (also known as white biotechnology) is the practice of using cells to generate industrially-useful products. The Economist speculated (as cited in the Economist article listed in the "References" section) industrial biotechnology might significantly impact the chemical industry. The Economist also suggested it might enable economies to become less dependent on fossil fuels.
Diversa is an example of a company that specializes in industrial biotechnology.
Bioremediation can be defined as any process that uses microorganisms or their enzymes to return the environment altered by contaminants to its original condition. Bioremediation may be employed in order to attack specific contaminants, such as chlorinated pesticides that are degraded by bacteria, or a more general approach may be taken, such as oil spills that are broken down using multiple techniques including the addition of fertilizer to facilitate the decomposition of crude oil by bacteria.
Not all contaminants are readily treated through the use of bioremediation; for example, heavy metals such as cadmium and lead are not readily absorbed or captured by organisms. The integration of metals such as mercury into the food chain may make things worse as organisms bioaccumulate these metals.
However, there are a number of advantages to bioremediation, which may be employed in areas which cannot be reached easily without excavation. For example, hydrocarbon spills (or more specific: gasoline) may contaminate groundwater well below the surface of the ground; injecting the right organisms, in conjunction with oxygen-forming compounds, may significantly reduce concentrations after a period of time. This is much less expensive than excavation followed by burial elsewhere or incineration, and reduces or eliminates the need for pumping and treatment, which is a common practice at sites where hydrocarbons have contaminated groundwater.
Generally, bioremediation technologies can be classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site while ex situ involves the removal of the contaminated material to be treated elsewhere. Some examples of bioremediation technologies are bioventing, land farming, bioreactor, composting, bioaugmentation and biostimulation.
A bioreactor is a vessel in which is carried out a chemical process which involves organisms or biochemically active substances derived from such organisms.
Bioreactors are commonly cylindrical, ranging in size from some liter to cube meters,and are often made of stainless steel.
Bioreactor design Bioreactor design is quite a complex engineering task. Under optimum conditions the microorganisms or cells will reproduce at an astounding rate. The vessel's environmental conditions like gas (i.e., air, oxygen, nitrogen, carbon dioxide) flowrates, temperature, pH and dissolved oxygen levels, and agitation speed need to be closely monitored and controlled. One bioreactor manufacturer, Broadley-James Corporation, uses vessels, sensors, controllers, and a control system, digitally networked together for their bioreactor system.
Fouling can harm the overall sterility and efficiency of the bioreactor, especially the heat exchangers. To avoid it the bioreactor must be easily cleanable and must be as smooth as possible (therefore the round shape).
Heat exchange is needed to maintain the bioprocess at a constant temperature. Biological fermentation is a major source of heat, therefore in most cases bioreactors need water refrigeration. They can be refrigerated with an external jacket or, for very large vessels, with internal coils.
Optimal oxygen transfer is perhaps the most difficult task to accomplish. Oxygen is poorly soluble in water -and even less in fermentation broths- and is relatively scarce in air (20.8%). Oxygen transfer is usually helped by agitation, that is also needed to mix nutrients and to keep the fermentation homogeneous. There are however limits to the speed of agitation, due both to high power consumption (that's proportional to the cube of the speed) and the damage to organisms due to excessive tip speed.
Compost is the decomposed remnants of organic materials (those with plant and animal origins). Compost is used in gardening and agriculture, mixed in with the soil. It improves soil structure, increases the amount of organic matter, and provides nutrients.
Biochem Biophys Res Commun, 1999 Aug 2, 261(2), 238 - 41 Protein expression in liposomes; Oberholzer T et al.; Compartmentalization is one of the key steps in the evolution of cellular structures and, so far, only few attempts have been made to model this kind of "compartmentalized chemistry" using liposomes . The present work shows that even such complex reactions as the ribosomal synthesis of polypeptides can be carried out in liposomes . A method is described for incorporating into 1-palmitoyl-2-oleoyl-sn-3-phosphocholine (POPC) liposomes the ribosomal complex together with the other components necessary for protein expression . Synthesis of poly(Phe) in the liposomes is monitored by trichloroacetic acid of the (14)C-labelled products . Control experiments carried out in the absence of one of the ribosomal subunits show by contrast no significant polypeptide expression . This methodology opens up the possibility of using liposomes as minimal cell bioreactors with growing degree of synthetic complexity, which may be relevant for the field of origin of life as well as for biotechnological applications .
Biodegradation, 1999 Feb, 10(1), 63 - 73 Anaerobic biodegradability of phthalic acid isomers and related compounds; Kleerebezem R et al.; All three phthalic acid isomers (ortho, meta and para benzene dicarboxylic acid) are produced in massive amounts, and used in the chemical industry as plasticizers or for the production of polyester . Wastestreams generated during the production of phthalate isomers generally contain high concentrations of aromatic acids . To study the potential biodegradability of these primarily anthropogenic compounds in anaerobic bioreactors, biodegradability studies were performed . Compounds tested were benzoate, ortho-phthalate, isophthalate, terephthalate, dimethyl phthalate, dimethyl terephthalate, para-toluate and para-xylene . Seed materials tested were two types of granular sludge and digested sewage sludge . It was found that all phthalate isomers and their corresponding dimethyl-esters, could be completely mineralized by all seed materials studied . Lag phases required for 50% degradation of these compounds, ranged from 17 to 156 days . The observed degradation curves could be explained by growth of an initially small amount of organisms in the inoculum with the specific ability to degrade one phthalate isomer . The observed order in the length of the lag phases for the phthalate isomers is: phthalate < terephthalate < isophthalate . This order appears to be related to the environmental abundancy of the different phthalate isomers . The initial step in the degradation pathway of both dimethyl phthalate esters was hydrolysis of the ester sidechain, resulting in the formation of the corresponding mono-methyl-phthalate isomer and phthalate isomer . The rate limiting step in mineralization of both dimethyl phthalate and dimethyl terephthalate was found to be fermentation of the phthalate isomer . Para-toluate was degraded only by digested sewage sludge after a lag phase of 425 days . The observed degradation rates of this compound were very low . No mineralization of para-xylene was observed . In general, the differences in the lag phases between different seed materials were relatively small . These results indicate that the time needed for the start-up of anaerobic bioreactors treating wastewaters containing phthalic acid isomers, depends little on the microbial composition of the seed material applied, but may take several months.
Mol Reprod Dev, 1999 Sep, 54(1), 17 - 23 Analysis of control elements for position-independent expression of human alpha-lactalbumin YAC; Fujiwara Y et al.; A major problem in the production of transgenic animal bioreactors using microinjections is the low production rate of high-expressing transgenic animals due to the position effect . We previously reported that transgenic rats carrying the 210 kb yeast artificial chromosome (YAC) including the human alpha-lactalbumin gene express the transgene in a position-independent manner . The 210 kb YAC was thought to have all the elements necessary for position-independent expression . In this paper, we constructed fragmented YAC clones and a cosmid clone, and produced transgenic rats to analyze these elements . Transgenic rats with both the 50 kb upstream and downstream regions of the alpha-lactalbumin gene had position-independent expression . Transgenic rats with the 20 kb upstream and downstream regions, however, had position-dependent expression . Therefore, all the elements necessary for position-independent expression are thought to be located in the 50 kb upstream to 50 kb downstream region of the alpha-lactalbumin gene . Furthermore, we replaced the human alpha-lactalbumin promoter with the bovine alphaS1-casein promoter in the 210 kb YAC and produced transgenic rats . Position-dependent expression was observed . The elements required for position-independent expression of the bovine alphaS1-casein gene are different from those required for the human alpha-lactalbumin gene, despite the fact that the two genes have the same tissue and developmental specificity .
Appl Microbiol Biotechnol, 1999 Jun, 51(6), 760 - 4 High-density Escherichia coli cultures for continuous L(-)-carnitine production; Obon JM et al.; The use of a biological procedure for L-carnitine production as an alternative to chemical methods must be accompanied by an efficient and highly productive reaction system . Continuous L-carnitine production from crotonobetaine was studied in a cell-recycle reactor with Escherichia coli O44 K74 as biocatalyst . This bioreactor, running under the optimum medium composition (25 mM fumarate, 5 g/l peptone), was able to reach a high cell density (26 g dry weight/l) and therefore to obtain high productivity values (6.2 g L-carnitine l-1 h-1) . This process showed its feasibility for industrial L-carnitine production . In addition, resting cells maintained in continuous operation, with crotonobetaine as the only medium component, kept their biocatalytic capacity for 4 days, but the biotransformation capacity decreased progressively when this particular method of cultivation was used.
Ann N Y Acad Sci, 1999 Jun 18, 875, 405 - 11 Bioreactor development for tissue-engineered cartilage; Wu F et al.; The development of tissue engineered cartilage is emerging as a potential treatment for the repair of cartilage defects . By seeding chondrocytes onto poly-glycolic acid (PGA) biodegradable scaffolds within a convective-flow bioreactor, the synthesis of tissue-engineered articular cartilage has been recently demonstrated . The ability to cultivate and manipulate this cell-polymer construct to possess specific dimensions, as well as biochemical and biomechanical properties is critical for potential application as an in vivo therapy of damaged articular surfaces . Bioreactor design requirements for stages from research to development to commercialization are discussed . Advantages and limitations to various bioreactor designs are critiqued . These studies illustrate the ability to synthesize tissue-engineered cartilage under convective-flow conditions for potential human tissue repair.
Ann N Y Acad Sci, 1999 Jun 18, 875, 386 - 97 Computer controlled bioreactor for large-scale production of cultured skin grafts; Prenosil JE et al.; KERATOR--an automated membrane bioreactor--was developed to produce Autologous Wound Dressing (AWD) at significantly reduced cost and time of transplantation down to two weeks time . At the same time, the risk of human error is largely eliminated . The computer-controlled reactor is modular, allowing the production of up to 0.5 m2 AWD at one time . A special feature of the reactor is a hydrophilic polymeric support membrane on which the human keratinocytes attach and proliferate . Recently developed serum-free medium is used to culture keratinocytes as a monolayer without a feeder layer of murine fibroblasts . The use of composite skin grafts consisting of a subconfluent keratinocyte layer on a polymeric support film is a very promising method for skin transplantation owing to the high activity of non-differentiated keratinocyte cells and reduction of the time needed to prepare the skin grafts . A microscopic video system with image analysis was developed for on-line monitoring of the cell growth and morphology in the KERATOR . The computer uses the obtained information to control medium change and to predict the end of cultivation.
Ann N Y Acad Sci, 1999 Jun 18, 875, 364 - 8 Cultivation and characterization of a new immortalized human hepatocyte cell line, HepZ, for use in an artificial liver support system; Werner A et al.; The new human hepatocyte cell line HepZ was investigated with regard to use it for a mass cell cultivation . The cells were originally derived from a human liver biopsy and immortalized through lipofectamine-mediated transfection of albumin-promotor-regulated antisense constructions against the negative controlling cell cycle proteins Rb and p53 (pAlb asRb, pAIb asp53) . Furthermore, plasmids including genes coding for the cellular transcription factor E2F and D1 cyclin (pCMV E2F, pSV2neo D1) were cotransfected to overcome the G1-restriction point . Cell cultivation was performed in a 2-liter bioreactor with a working volume of 1 liter . With CultiSpher G microcarriers used in a concentration of 3 g/l a maximal density of 7.1 x 10(6) cells/ml was achieved in a cultivation period of 20 days . The cells exhibited a maximal specific growth rate of 1.0 per day in the first 4 days . After 9 days of cultivation the stationary growth phase was reached with an average cell density of 5.5 x 10(6) cells/ml . The viability status of the culture was determined indirectly by measuring of the lactate dehydrogenase activity (LDH) at 37 degrees C . During the growth phase the activity rose slightly up to a value of 200 U/l . The cells were flat after first attachment on the gelatine microcarriers and spherical after growing into the three-dimensional inner matrix--both of which characteristics were verified by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) . The liver-specific cytochrome P450 activity was challenged with a pulse of 7 micrograms/ml lidocaine at a cell density of 4.5 x 10(6) cells/ml . After an induction period of 3 days with 50 micrograms/ml of phenobarbital, 26 ng/ml MEGX were generated within one day compared to 5 ng/ml without induction . The new cell line HepZ has proven to retain liver-specific qualities and to be appropriate for mass cell cultivation for bioartificial devices.
Ann N Y Acad Sci, 1999 Jun 18, 875, 326 - 39 Bioreactors for hybrid liver support: historical aspects and novel designs; Busse B et al.; A novel bioreactor construction has been designed for the utilization of hepatocytes and sinusoidal endothelial cells . The reactor is based on capillaries for hepatocyte aggregate immobilization . Three separate capillary membrane systems, each permitting a different function are woven in order to create a three dimensional network . Cells are perfused via independent capillary membrane compartments . Decentralized oxygen supply and carbon dioxide removal with low gradients are possible . The use of identical parallel units to supply hepatocytes facilitates scale up . In vitro studies demonstrate long-term external metabolic function in primary isolated hepatocytes within bioreactors . These systems are capable of supporting essential liver functions . Animal experiments have verified the possibility of scaling-up the bioreactors for clinical treatment . However, since there is no reliable animal model for investigation of the treatment of acute liver failure, the promising results obtained from these studies have limited relevance . The small number of clinical studies performed so far is not sufficient to reach conclusions about improvements in the therapy of acute liver failure . Although important progress has been made in the development of these systems, various hepatocyte culture models and bioreactor constructions are being discussed in the literature, which indicates competition in this field of medical research . An overview, which emphasizes the development of hepatocyte culture models for bioreactors, subsequent in vitro studies, animal studies, and clinical application, is also provided.
Ann N Y Acad Sci, 1999 Jun 18, 875, 310 - 25 Overview of extracorporeal liver support systems and clinical results; McLaughlin BE et al.; Patients with acute liver failure (ALF) continue to have an almost 50% mortality rate despite improvements associated with the use of orthotopic liver transplantation (OLT) . Numerous ex vivo methods have been developed in attempts to improve patient survival . These methods can be divided into three groups: detoxification (e.g., dialysis, charcoal adsorption, plasma exchange), which only provides excretory function; ex vivo liver perfusion (e.g., whole organ or tissue perfusion), which provides some metabolic function; and bioartificial or cell-based systems, which combine elements of the first two methods . Clinical trials have shown minimal efficacy of the various detoxification methods in terms of ALF patient survival, while the relative success of OLT has shown the importance of providing metabolic as well as excretory functions . Attempts to provide those additional functions with ex vivo tissue perfusion have been fraught with complications such as clotting and acute tissue rejection, leading to the conceptual development of cell-based bioreactor systems . A number of these bioartificial systems have been clinically evaluated, and the preliminary patient survival rates have encouraged further work in this area.
Arch Otolaryngol Head Neck Surg, 2001 May, 127(5), 525 - 8 Bacterial colonization of endotracheal tubes in intubated neonates; Friedland DR et al.; OBJECTIVE: To obtain in vivo bacterial colonization profiles on endotracheal tubes at different sites in the neonatal airway in an attempt to better characterize one potential element of chondritis . DESIGN: A case series in which cultures were obtained from calculated segments of 33 endotracheal tubes immediately following extubation . This allowed for sampling at specific levels of the airway corresponding to the trachea, the subglottis, and the oropharynx . Data collected included gender, race, duration of intubation, use of antibiotic therapy, comorbidities, gestational age at birth and extubation, crown-rump length, weight, radiographic distance from tube tip to carina, and culture results . SETTING: Newborn intensive care unit at a tertiary care medical center . PATIENTS: Twenty-nine neonates intubated for longer than 24 hours (range, 24 hours to 15 days) . MAIN OUTCOME MEASURES: Bacterial and fungal cultures obtained from 3 endotracheal tube segments for each extubation . RESULTS: A statistically significant difference (P < .05) was found in colonization rates between patients intubated for less than 4 days and those intubated for longer periods . No significant difference was noted in bacterial profile between the 3 sites . CONCLUSIONS: Data demonstrate that bacterial colonization of an indwelling object in the neonatal airway increases with the duration of intubation . Furthermore, 4 days seems to represent a critical period in the formation of such colonization (possibly in the form of a biofilm) . These bacteria may contribute to the chondritis known to precede the development of subglottic stenosis . Further studies are indicated to suggest ways to interrupt this process and reduce the incidence of airway injury.
Antimicrob Agents Chemother, 2001 Jun, 45(6), 1761 - 70 Multidrug efflux pumps: expression patterns and contribution to antibiotic resistance in Pseudomonas aeruginosa biofilms; De Kievit TR et al.; Pseudomonas aeruginosa biofilms are intrinsically resistant to antimicrobial chemotherapies . At present, very little is known about the physiological changes that occur during the transition from the planktonic to biofilm mode of growth . The resistance of P . aeruginosa biofilms to numerous antimicrobial agents that are substrates subject to active efflux from planktonic cells suggests that efflux pumps may substantially contribute to the innate resistance of biofilms . In this study, we investigated the expression of genes associated with two multidrug resistance (MDR) efflux pumps, MexAB-OprM and MexCD-OprJ, throughout the course of biofilm development . Using fusions to gfp, we were able to analyze spatial and temporal expression of mexA and mexC in the developing biofilm . Remarkably, expression of mexAB-oprM and mexCD-oprJ was not upregulated but rather decreased over time in the developing biofilm . Northern blot analysis confirmed that these pumps were not hyperexpressed in the biofilm . Furthermore, spatial differences in mexAB-oprM and mexCD-oprJ expression were observed, with maximal activity occurring at the biofilm substratum . Using a series of MDR mutants, we assessed the contribution of the MexAB-OprM, MexCD-OprJ, MexEF-OprN, and MexXY efflux pumps to P . aeruginosa biofilm resistance . These analyses led to the surprising discovery that the four characterized efflux pumps do not play a role in the antibiotic-resistant phenotype of P . aeruginosa biofilms.
Biomaterials, 2001 May, 22(10), 1035 - 47 Long-term stability of grafted polyethylene glycol surfaces for use with microstamped substrates in neuronal cell culture; Branch DW et al.; Crucial to long-term stability of neuronal micropatterns is functional retention of the underlying substratum while exposed to cell culture conditions . We report on the ability of covalently bound PEG films in long-term cell culture to continually retard protein adhesion and cell growth . PDMS microstamps were used to create poly-d-lysine (PDL) substrates permissive to cell attachment and growth, and polyethylene glycol (PEG) substrates were used to minimize protein and cell adhesion . Film thickness was measured using null ellipsometry and atomic force microscopy (AFM) . Organosilane film structure was examined using Fourier transform infrared (FT-IR) spectroscopy . Long-term film stability in cell culture conditions was tested by immersion in 0.1 M sodium phosphate buffer pH 7.4 for up to one month . Null ellipsometry and water contact measurements indicated that organosilane films were stable up to one month, whereas the PEG film thickness declined rapidly after day 25 . Hippocampal cells plated at 200 cells/mm2 on uniform PEG substrates gave a steady increase in biofilm thickness on PEG films throughout the culture, possibly from proteins of neuronal origin . We found that all the layers in the cross-linking procedure were stable in cell culture conditions, with the exception of PEG, which degraded after day 25.
J Clin Periodontol, 2001 Jun, 28(6), 569 - 75 Infection-mediated early-onset periodontal disease in P/E-selectin-deficient mice; Niederman R et al.; BACKGROUND: Retrospective and correlation studies suggest that early-onset periodontal disease may be due to a deficiency in phagocyte function, a pathogenic oral biofilm, and/or dysregulated gingival cytokine expression . Increased susceptibility to periodontal disease is therefore thought to result from multiple risk factors . METHODS: We tested this hypothesis prospectively using P/E-selectin adhesion molecule deficient mice that mimic the human syndrome leukocyte adhesion deficiency II . RESULTS: Our studies demonstrate that, in comparison to wild type animals, P/E-/- mice exhibit: spontaneous, early onset alveolar bone loss which is significant by 6 weeks of age; a 10-fold elevation in bacterial colonization of their oral cavities; and elevated gingival tissue levels of the bone resorptive cytokine IL-1alpha . Alveolar bone loss is completely prevented by prophylactic antibiotic therapy . CONCLUSIONS: These experiments provide the first prospective evidence for the multiple risk factor hypothesis of periodontal disease, and validate the first animal model for early onset periodontitis in which both the microbiota and host response can be systematically manipulated . P/E-/- animals should be useful in testing the virulence of putative periodontal pathogens, in determining the role of host resistance factors in periodontitis, in exploring the proposed relationship(s) between infection mediated alveolar bone loss and systemic health disorders, and exploring their genetic relationships.
J Clin Periodontol, 2001 May, 28(5), 411 - 8 The effect of systemic antibiotics in the treatment of patients with recurrent periodontitis; Serino G et al.; BACKGROUND: Subjects with periodontal disease exist who either (i) respond poorly to initial mechanical therapy ("refractory" periodontitis) or (ii) fail to adopt adequate self-performed plaque control techniques and hence develop recurrent disease ("recurrent" periodontitis) at multiple sites during the supportive treatment phase (SPT) . Various systemic antibiotic regimens have been tried as adjuncts to the mechanical (re-) treatment of such "difficult to treat"-patients . While most studies indicated a positive outcome of the adjunctive therapy, some clinical investigators reported that this additional measure provided little or no benefit . AIM: The aim of the present investigation was to study the more long term effect of adjunctive antibiotic therapy in the re-treatment of patients with a well defined history of recurrent periodontitis . MATERIAL AND METHODS: 17 subjects with recurrent advanced periodontal disease were, following a baseline examination, subjected to non-surgical therapy including the use of systemic antibiotics (amoxicillin and metronidazole) . They were placed in a careful SPT program and re-examined after 1, 3 and 5 years . The examinations included both clinical and microbiological assessments . RESULTS: It was demonstrated that in subjects with advanced and recurrent periodontitis, re-treatment including (i) comprehensive scaling and root planing (SRP), (ii) systemic administration of antibiotics and (iii) meticulous supragingival plaque control by both mechanical and chemical means established periodontal conditions that in the short term (3 years) and in the majority of subjects could be properly maintained by traditional SPT measures . Between 3 and 5 years, however, only 5 of the 17 subjects exhibited stable periodontal attachment levels . CONCLUSIONS: Some deep pockets and furcations were most likely inadequately instrumented during the active treatment phase . Microorganisms residing in biofilms left in such locations were probably not sufficiently affected by the 2 weeks of adjunctive antibiotic therapy . It is suggested that removal of certain subgingival deposits, therefore, may require surgical intervention.
Infect Immun, 2001 Jun, 69(6), 4079 - 85 Anaerobic conditions induce expression of polysaccharide intercellular adhesin in Staphylococcus aureus and Staphylococcus epidermidis; Cramton SE et al.; Products of the intercellular adhesion (ica) operon in Staphylococcus aureus and Staphylococcus epidermidis synthesize a linear beta-1,6-linked glucosaminylglycan . This extracellular polysaccharide mediates bacterial cell-cell adhesion and is required for biofilm formation, which is thought to increase the virulence of both pathogens in association with prosthetic biomedical implants . The environmental signal(s) that triggers ica gene product and polysaccharide expression is unknown . Here we demonstrate that anaerobic in vitro growth conditions lead to increased polysaccharide expression in both S . aureus and S . epidermidis, although the regulation is less stringent in S . epidermidis . Anaerobiosis also dramatically stimulates ica-specific mRNA expression in ica- and polysaccharide-positive strains of both S . aureus and S . epidermidis . These data suggest a mechanism whereby ica gene expression and polysaccharide production may act as a virulence factor in an anaerobic environment in vivo.
J Food Prot, 2001 May, 64(5), 652 - 8 Decontamination of lettuce using acidic electrolyzed water; Koseki S et al.; The disinfectant effect of acidic electrolyzed water (AcEW), ozonated water, and sodium hypochlorite (NaOCl) solution on lettuce was examined . AcEW (pH 2.6; oxidation reduction potential, 1140 mV; 30 ppm of available chlorine) and NaOCl solution (150 ppm of available chlorine) reduced viable aerobes in lettuce by 2 log CFU/g within 10 min . For lettuce washed in alkaline electrolyzed water (AIEW) for 1 min and then disinfected in AcEW for 1 min, viable aerobes were reduced by 2 log CFU/g . On the other hand, ozonated water containing 5 ppm of ozone reduced viable aerobes in lettuce 1.5 log CFU/g within 10 min . It was discovered that AcEW showed a higher disinfectant effect than did ozonated water significantly at P < 0.05 . It was confirmed by swabbing test that AcEW, ozonated water, and NaOCI solution removed aerobic bacteria, coliform bacteria, molds, and yeasts on the surface of lettuce . Therefore, residual microorganisms after the decontamination of lettuce were either in the inside of the cellular tissue, such as the stomata, or making biofilm on the surface of lettuce . Biofilms were observed by a scanning electron microscope on the surface of the lettuce treated with AcEW . Moreover, it was shown that the spores of bacteria on the surface were not removed by any treatment in this study . However, it was also observed that the surface structure of lettuce was not damaged by any treatment in this study . Thus, the use of AcEW for decontamination of fresh lettuce was suggested to be an effective means of controlling microorganisms.
Environ Sci Technol, 2001 Mar 15, 35(6), 1118 - 26 Methyl tert-butyl ether biodegradation by indigenous aquifer microorganisms under natural and artificial oxic conditions; Landmeyer JE et al.; Microbial communities indigenous to a shallow groundwater system near Beaufort, SC, degraded milligram per liter concentrations of methyl tert-butyl ether (MTBE) under natural and artificial oxic conditions . Significant MTBE biodegradation was observed where anoxic, MTBE-contaminated groundwater discharged to a concrete-lined ditch . In the anoxic groundwater adjacent to the ditch, concentrations of MTBE were > 1 mg/L . Where groundwater discharge occurs, dissolved oxygen (DO) concentrations beneath the ditch exceeded 1.0 mg/Lto a depth of 1.5 m, and MTBE concentrations decreased to
Crit Rev Oral Biol Med, 2001, 12(2), 179 - 85 Immunodominant antigens in periodontal disease: a real or illusive concept? Podmore M, Ebersole JL, Kinane DF. The humoral arm of the immune system provides protection from many medically significant pathogens . The antigenic epitopes of the pathogens which induce these responses, and the subsequent characteristics of the host response, have been extensively documented in the medical literature, and in many cases have resulted in the development and implementation of effective vaccines or diagnostic tests . There is a substantial body of literature on the humoral immune response in periodontal disease, which is targeted at micro-organisms present within periodontal pockets . However, the significance and specificity of the immune response in periodontal disease have proved difficult to elucidate, due to the large number of potential pathogens in the plaque biofilm and the apparent commensal nature of many of these opportunistic pathogens . This review addresses our current knowledge of the approaches and strategies which have been used to elucidate and examine the concept of immunodominant antigens in medical infections and, more recently, periodontal disease . An identification/understanding of the immunodominant antigens would be informative with respect to: (i) the relative importance of the implicated pathogens, (ii) new approaches to immunological diagnosis, (iii) specific bacterial virulence determinants, (iv) natural protective responses, and (v) the selection of potential vaccine candidate antigens . We conclude that immunodominance of antigens in periodontal disease may be relevant to our understanding of periodontal disease pathogenesis, but due to the complexity and diversity of the 'pathogenic microbial ecology', it is currently an enigmatic topic requiring a multidisciplinary approach linking clinical, microbiological, and immunological investigations . We also conclude, after assessing the literature available on the topic of immunodominance, that it is a term that, if used, must be clearly defined and understood, since it is often used loosely, leading to a general misinterpretation by readers of oral and medical literature.
Water Res, 2001 Jun, 35(8), 2029 - 37 Clogging of a limestone fracture by stimulating groundwater microbes; Ross N et al.; Biological clogging is promoted in aquifers either to contain or to remediate groundwater . In this study, an apparatus able to detect small changes in hydraulic conductivity (K) was developed to measure the clogging of a single fracture in limestone, following microbial stimulation . The fracture had a 2.5 mm2 section and was 50 cm long . Prior to the inoculation of the limestone, the sequencing of representative clones from 16S rRNA genes isolated from groundwater, showed significant affiliation with Cytophaga spp., Arcobacter spp . and Rhizobium spp . These bacteria are known to secrete extracellular polymeric substances and form biofilms . When nutrients were added to the inoculated limestone, a decrease in K occurred after 8 days, reaching 0.8% of its initial value after 22 days (Kfi = 340 cm min-1) . This study showed that a stimulation of indigenous microbes from groundwater effectively clogged a macrofracture in limestone, suggesting the potential application of biobarriers in fractured rock aquifers.
Int J Antimicrob Agents, 2001 May, 17(5), 351 - 6 Airway biofilm disease; Kobayashi H; This paper describes the formation of biofilm, its characteristics, its effect on the host cells and treatment of the condition . The airway biofilm diseases are known to be intractable and persistent; also, auto-immune factors play a role in the development of the symptoms . The characteristic of airway biofilm diseases is of a harmful auto-immune reaction occurring along with the symptoms which are different from the simple acute infection interaction between microorganism and host in an acute airway infection.
Trends Microbiol, 2001 May, 9(5), 222 - 7 The biofilm matrix--an immobilized but dynamic microbial environment; Sutherland IW; The biofilm matrix is a dynamic environment in which the component microbial cells appear to reach homeostasis and are optimally organized to make use of all available nutrients . The major matrix components are microbial cells, polysaccharides and water, together with excreted cellular products . The matrix therefore shows great microheterogeneity, within which numerous microenvironments can exist . Although exopolysaccharides provide the matrix framework, a wide range of enzyme activities can be found within the biofilm, some of which will greatly affect structural integrity and stability.
J Colloid Interface Sci, 2001 May 1, 237(1), 54 - 61 Atomic Force Microscopy Study of the Adhesion of Saccharomyces cerevisiae; Bowen WR et al.; An atomic force microscope (AFM) has been used to quantify directly the adhesion of metabolically active Saccharomyces cerevisiae cells at a hydrophilic mica surface, a mica surface with a hydrophobic coating, and a protein-coated mica surface in an aqueous environment . The measurements used "cell probes" constructed by immobilizing a single cell at the apex of a tipless AFM cantilever . Adhesion was quantified from force-distance data for the retraction of the cell from the surface . The data indicated stretching and sequential bond-breaking as the cell probe was retracted from all of the surfaces . Detailed studies were made for physiologically active cells, which were shown to have different adhesion properties to glutaraldehyde-treated cells . Greatest cell adhesion was measured at the hydrophobic surface . Prior adsorption of a bovine serum albumin protein layer at the hydrophilic surface did not significantly affect cell adhesion . Changes in yeast surface hydrophobicity and zeta-potential with yeast cell age were correlated with differences in adhesion . Cells from the stationary phase adhered most strongly to a mica surface . Time of surface contact was demonstrated to be important . Both the force needed to detach a cell from a hydrophilic mica surface and the length of the adhesive interaction increased after 5 min contact . The AFM cell probe technique gives unique insights into primary colonization events in biofilm formation . It will continue to aid both fundamental studies and the assessment of new procedures that are designed to lower cell adhesion at surfaces relevant to biotechnology, medicine, and dentistry
Cornea, 2001 May, 20(4), 362 - 5 The detection of bacteria and bacterial biofilms in punctal plug holes; Sugita J et al.; PURPOSE: An investigation into bacterial biofilm formation on and in punctal plugs . METHODS: The study involved 21 patients with severe dry eye whose puncta were occluded by the use of punctal plugs . Of these, 15 had Sjogren's syndrome, 3 had non-Sjogren's syndrome, 2 had Stevens-Johnson syndrome, and 1 had graft-versus-host disease . From 17 of the 21 subjects, 18 samples of material were extracted from the holes of the punctal plugs (16 unilateral and 1 bilateral) and were subjected to enrichment culture . Nineteen punctal plugs were removed and processed for electron microscopy: 15 by scanning electron microscopy, and 4 by transmission electron microscopy . RESULTS: Positive cultures were found in 8 of 18 (44%) samples of the material extracted from the holes of punctal plugs . In six of these eight cases (75%) the cultured bacterial species was Staphylococcus epidermidis, whereas in the other two cases (25%) it was S . aureus . In 8 of the 15 punctal plugs examined by scanning electron microscopy and in the material extracted from 1 plug that was examined by transmission electron microscopy, there was clear evidence of bacterial colonization . CONCLUSION: Careful observation of patients with punctal plugs is important . If material accumulates in or on a punctal plug, it may contain bacteria and may form a bacterial biofilm . In these cases, replacement of the plug, clearing of the hole, or an alternative treatment should be considered.
Water Res, 2001 May, 35(7), 1730 - 8 The formation of malodorous dimethyl oligosulphides in treated groundwater: the role of biofilms and potential precursors; Franzmann PD et al.; Water distributed from the Wanneroo Groundwater Treatment Plant intermittently contains dimethyl trisulphide (DMTS) . The compound is responsible for a "swampy odour" in the water . DMTS production from potential precursors was insignificant in the absence of biofilms when compared with DMTS production from precursors in the presence of biofilms in a biofilm reactor . Greatest dimethyl disulphide (DMDS) and DMTS production (> 3000 ng L-1 DMTS) occurred in the reactors when supplied with methane thio-containing compounds, such as methionine, S-methyl cysteine and methyl-3-(methylmercapto)-propionate . Abiotic DMTS production from oligosulphides also occurred through the addition of the methylating agents, methyl iodide or methyl-p-toluene sulphonate . Significant DMTS production also occurred with Wanneroo water that contained added omega-thio-containing compounds such as cysteine (1400 ng L-1 DMTS), and 3-mercaptopropionate (210 ng L-1) . Biomethylation, a ubiquitous response by microorganisms for the detoxification of toxic compounds, generated DMDS/TS from biofilm oligosulphides . Biofilms exposed to the toxic compounds selenate or 2,4,6-trichlorophenol methylated oligosulphides in addition to the toxins . Sodium sulphide also stimulated DMTS production . Easily Biodegradable Dissolved Organic Carbon (BDOC) probably contributed indirectly to DMTS production by the biofilms, although whether this was a result of its stimulation of greater microbial activity or consumption of oxygen, or both, remains unresolved . Stagnation of water in the biofilm reactors also increased DMTS production, which was concomitant with depletion of oxygen concentrations in the bulk water . Many processes, such as degradation of methane thio-containing compounds, methylation of sulphides and oligosulphides, and changes in contributions of different metabolic pathways upon depletion of oxygen concentrations upon water stagnation, probably contribute simultaneously to "swampy odour" production in the distribution system.
J Periodontol, 2001 Mar, 72(3), 401 - 10 Evaluation of ultrasonic scaling unit waterline contamination after use of chlorine dioxide mouthrinse lavage; Wirthlin MR et al.; BACKGROUND: An infection control problem in dental operatories which is not fully controlled is waterline contamination by heterotrophic mesophilic bacteria . These bacteria are present in water supplies as a planktonic phase and adhere to the lumen of tubings as a biofilm comprised of their external cell surface glycocalyx and by production of extracellular carbohydrate polymers . The adherent film is most difficult to remove . The accumulated planktonic phase can be reduced significantly by flushing water from the lines before use in patient treatment, but will return when the equipment is idle through the accumulation of more planktonic phase and by slough of the biofilm surface-adsorbed phase not yet enmeshed in the carbohydrate matrix . Chlorine dioxide has antimicrobial activity against many bacteria, spores, and viruses . It is used in water supply treatment as a disinfectant and slime preventive and has an advantage over chlorine in that carcinogenic trihalomethanes are not generated . METHODS: This study compared use of phosphate buffer-stabilized chlorine dioxide (0.1%) mouthrinse as a lavage in ultrasonic dental scaler units with the use of tap water as a control . Sterile water flushed through the units onto heterotrophic plate count (HPC) sampler plates was cultured 7 days at room temperature and colonies were counted at 12x . One test and one control unit were used for biopsy of internal tubing and scanning electron microscopy imaging . RESULTS: The HPC counts, in colony forming units (CFU)/ml, were reduced 3- to 5-fold by flushing tap water through the units, but they returned after units were idle overnight . When phosphate-buffered chlorine dioxide mouthrinse was used as a lavage, CFU/ml were reduced 12- to 20-fold . Holding chlorine dioxide in waterlines overnight reduced recurrent buildup compared to water (P
J Periodontol, 2001 Mar, 72(3), 393 - 400 Dental unit waterline contamination and its possible implications during periodontal surgery; Putnins EE et al.; BACKGROUND: Dental unit waterline contamination has become a concern to clinical dentistry . This concern arises from the fact that bacteria sloughed from established biofilms in dental unit waterlines increase heterotrophic bacteria counts in water exiting these units . METHODS: Scanning microscopy and bacterial viability staining were used to examine the sessile and planktonic biofilm present in dental unit waterlines and water samples, respectively . In addition, the limulus amebocyte assay was used to measure the lipopolysaccharide (LPS) levels in water samples . RESULTS: All dental unit waterlines were coated with a well-established biofilm made up of filamentous and bacillus-like microorganisms . Water samples collected from these dental units contained high numbers of individual bacteria and bacterial aggregates . A viability staining technique identified significantly more bacteria in water than could be cultured, and 64% of the total bacterial population stained as nonvital . Since the bacterial load (viable and nonviable) was high, we examined the LPS in dental unit water samples . The mean LPS levels in water collected from high-speed and air/water lines in use were 480 and 1,008 endotoxin units (EU)/ml . This was significantly higher than the mean level of 66 EU/ml found in water samples collected from adjacent clinic sinks . The LPS level at the start of the day (2,560 EU/ml) was reduced by 70% with 1 minute of flushing (800 EU/ml) . Flushing times of 5 and 10 minutes were not able to reduce LPS levels to zero . CONCLUSION: The presence of high heterotrophic bacterial counts, sloughing biofilm, and high LPS levels are discussed in relation to patient risk and periodontal wound healing biology.
J Calif Dent Assoc, 2000 Mar, 28(3), 185 - 93 Responsible use of antimicrobials in periodontics; Jorgensen MG et al.; New products and treatment modalities for the management of periodontal disease continue to offer the clinician a large number of choices, many of which involve antimicrobials . Specific pathogenic bacteria play a central role in the etiology and pathogenesis of destructive periodontal disease . Under suitable conditions, periodontal pathogens colonize the subgingival environment and are incorporated into a tenacious biofilm . Successful prevention and treatment of periodontitis is contingent upon effective control of the periodontopathic bacteria . This is accomplished by professional treatment of diseased periodontal sites and patient-performed plaque control . Attention to community factors, such as water contamination and bacterial transmission among family members, facilitates preventive measures and early treatment for the entire family . Subgingival mechanical debridement, with or without surgery, constitutes the basic means of disrupting the subgingival biofilm and controlling pathogens . Appropriate antimicrobial agents that can be administered systemically (antibiotics) or via local delivery (povidone-iodine) may enhance eradication or marked suppression of subgingival pathogens . Microbiological testing may aid the clinician in the selection of the most effective antimicrobial agent or combination of agents . Understanding the benefits and limitations of antibiotics and antiseptics will optimize their usefulness in combating periodontal infections.
J Mass Dent Soc, 2000 Autumn, 49(3), 10 - 3 Quantifiable risk in dentistry--a letter to the profession; Neiburger EJ; Recent attention to certain worries such as the AIDS "epidemic," biofilms in dental unit water lines, and hepatitis C have resulted in unbalanced and often inappropriate action by dentists and public health authorities . These actions include exaggerating, underestimating, and ignoring risks in the dental environment . To be effective and responsible practitioners, we must recognize reality and proportion, concentrate resources on the greatest problems, and seek dependable epidemiology . Infection control issues are an important application for this form of evidence-based science.
No comments:
Post a Comment