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Aurélien Dumètre - One of the best experts on this subject based on the ideXlab platform.
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Dynamics of Toxoplasma gondii Oocyst Phagocytosis by Macrophages
Frontiers in Cellular and Infection Microbiology, 2020Co-Authors: Omar Ndao, Pierre-henri Puech, Nadine Azas, Jitender Dubey, Camille Bérard, Laurent Limozin, Sameh Rabhi, Aurélien DumètreAbstract:Oocysts are the environmentally resistant stage of the protozoan parasite Toxoplasma gondii. They are responsible for foodborne infections in humans and animals worldwide. Infectious Oocysts contain sporozoites that have to exit the sporocyst and oocyst walls to initiate replication of the parasite within the host tissues. Given their robustness and resistance to chemical degradation, it is still unclear how the oocyst and sporocyst walls release the sporozoites. This process called excystation is thought to occur in the small intestine as a result of the combined action of digestive agents, yet to be identified. By using an oocyst-macrophage co-culture platform, we previously demonstrated in vitro that the excystation of sporozoites and their differentiation into replicative tachyzoites could occur in absence of digestive factors, following phagocytosis by macrophages. Here, we further characterize the dynamics of the oocyst phagocytosis at the single-cell level by using optical tweezers and micropipette aspiration techniques. Our results show that the oocyst internalization kinetics can vary among a given population of macrophages, but similar processes and dynamics could be observed. Most of the cells manipulate Oocysts for ~15 min before internalizing them in typically 30 min. This process mainly involves the actin cytoskeleton of the macrophages. Liberated sporozoites within macrophages then differentiate into tachyzoites within 4–6 h following oocyst-macrophage contact. Tachyzoites appear to develop better in macrophages challenged with free sporocysts or sporozoites than with whole Oocysts, suggesting that opening of the oocyst wall is one of the most limiting steps for sporozoite excystation completion.
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Macrophages facilitate the excystation and differentiation of Toxoplasma gondii sporozoites into tachyzoites following oocyst internalisation
Scientific Reports, 2016Co-Authors: Wesley Freppel, Pierre-henri Puech, David Ferguson, Nadine Azas, Jitender Dubey, Aurélien DumètreAbstract:Toxoplasma gondii is a common parasite of humans and animals, which is transmitted via Oocysts in cat faeces or tissue cysts in contaminated meat. The robust oocyst and sporocyst walls protect the infective sporozoites from deleterious external attacks including disinfectants. Upon oocyst acquisition, these walls lose their integrity to let the sporozoites excyst and invade host cells following a process that remains poorly understood. Given the resistance of the oocyst wall to digestive enzymes and the ability of Oocysts to cause parenteral infections, the present study investigated the possible contribution of macrophages in supporting sporozoite excystation following oocyst internalisation. By using single cell micromanipulations, real-time and time-point imaging techniques, we demonstrated that RAW macrophages could interact rapidly with Oocysts and engulfed them by remodelling of their actin cytoskeleton. Internalised Oocysts were associated to macrophage acidic compartments and showed evidences of wall disruption. Sporozoites were observed in macrophages containing oocyst remnants or in new macrophages, giving rise to dividing tachyzoites. All together, these results highlight an unexpected role of phagocytic cells in processing T. gondii Oocysts, in line with non-classical routes of infection, and open new perspectives to identify chemical factors that lead to oocyst wall disruption under physiological conditions.
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Development of a sensitive method for Toxoplasma gondii oocyst extraction in soil.
Veterinary Parasitology, 2011Co-Authors: Maud Lélu, Emmanuelle Gilot-fromont, Dominique Aubert, Agnès Richaume, Eve Afonso, Emilie Dupuis, Cécile Gotteland, Francine Marnef, Marie-lazarine Poulle, Aurélien DumètreAbstract:Toxoplasmosis is a world-wide infection caused by Toxoplasma gondii. Oocysts disseminated in the environment by infected cats provide a major source of infection for humans and intermediate hosts. The level of soil contamination and the dynamics of this contamination are mostly unknown due to the lack of sensitivity of detection method. Our aim was to improve the detection of T. gondii Oocysts in soil samples by comparing three extraction protocols (A, B and C) on unsporulated and sporulated Oocysts of different strains and ages, and by testing the effect of sporulation and soil characteristics on oocyst recovery using the most efficient method. The oocyst recovery obtained using protocol C, in which the flotation solution was placed under the sample solution after the dispersion step, was at least ten-fold higher than protocols A and B, in which the sample was just filtered before flotation. The efficiency of protocol C, tested on five artificial soil matrices and four natural soils inoculated with Oocysts, was lowest in soils with high proportions of sand. We recommend the protocol C for field investigations, and we advise that results should be interpreted with caution, considering the effect of soil characteristics, especially sand content, on oocyst recovery.
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how to detect toxoplasma gondii Oocysts in environmental samples
Fems Microbiology Reviews, 2003Co-Authors: Aurélien Dumètre, Marie Laure DardeAbstract:Detection of Toxoplasma gondii Oocysts in environmental samples is a great challenge for researchers as this coccidian parasite can be responsible for severe infections in humans and in animals via ingestion of a single oocyst from contaminated water, soil, fruits or vegetables. Despite field investigations, Oocysts have been rarely recovered from the environment due to the lack of sensitive methods. Immunomagnetic separation, fluorescence-activated cell sorting, and polymerase chain reaction have recently shown promising use in detection of protozoa from complex matrices. Such procedures could be applied to T. gondii detection, if studies on the antigenic and biochemical composition of the oocyst wall are completed. Using such methods, it will be possible to assess the occurrence, prevalence, viability and virulence of T. gondii Oocysts in environmental matrices and specify sources of human and animal contamination.
Dwight D Bowman - One of the best experts on this subject based on the ideXlab platform.
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cryptosporidium parvum determination of id50 and the dose response relationship in experimentally challenged dairy calves
Veterinary Parasitology, 2013Co-Authors: Jennifer A Zambriski, D V Nydam, Z J Wilcox, Dwight D Bowman, Hussni O Mohammed, Janice L LiottaAbstract:Abstract The objectives were to determine the median infective dose (ID 50 ) of Cryptosporidium parvum and to describe the dose–response relationship including associated clinical illness in experimentally challenged dairy calves. Within the first 24 h of life, 27 test calves were experimentally challenged with C. parvum Oocysts and 3 control calves were sham dosed. Test calves received 1 of 8 possible doses (25, 50, 100, 500, 1 × 10 3 , 1 × 10 4 , 1 × 10 5 , and 1 × 10 6 Oocysts). All 27 test calves developed diarrhea. Fecal oocyst shedding occurred in 25 (92.6%) test calves and in 0 control calves. The 2 non-shedding test calves both received 25 Oocysts. There was an inverse relationship between dose and time to onset of fecal oocyst shedding ( P = 0.005). There was no relationship found between dose and duration ( P = 0.2) or cessation ( P = 0.3) of fecal oocyst shedding. In addition, there was not a significant relationship between log-dose and the log-peak Oocysts ( P = 0.2) or log-total Oocysts ( P = 0.5) counted/g of feces across the dose groups. There was a positive dose–response relationship between log-dose and diarrhea ( P = 0.01). However, when controlling for other factors, such as onset and cessation of fecal oocyst shedding, dose was not a significant predictor of diarrhea ( P = 0.5). Onset and cessation of fecal oocyst shedding were found to be the best predictors of diarrhea ( P = 0.0006 and P = 0.04, respectively). The ID 50 for fecal oocyst shedding was 5.8 Oocysts, for diarrhea was 9.7 Oocysts, and for fecal oocyst shedding with diarrhea was 16.6 Oocysts. Given that the ID 50 of C. parvum is far less than would be excreted into the environment by a naturally infected calf, prevention and control of cryptosporidiosis is a formidable challenge.
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description of fecal shedding of cryptosporidium parvum Oocysts in experimentally challenged dairy calves
Parasitology Research, 2013Co-Authors: Jennifer A Zambriski, D V Nydam, Dwight D Bowman, Janice L Liotta, Mary L Bellosa, Alexandra J Burton, Thomas C Linden, Theresa L Ollivett, Leonardo Tondellomartins, Hussni O MohammedAbstract:The objective was to describe the probability of Cryptosporidium parvum fecal oocyst shedding at different magnitudes of exposure, the pattern of fecal shedding over time, and factors affecting fecal shedding in dairy calves. Within the first 24 h of life, 36 calves were experimentally challenged with C. parvum Oocysts at one of four possible magnitudes of oral exposure (1 × 10(3), 1 × 10(4), 1 × 10(5), and 1 × 10(6) Oocysts), and 7 control calves were sham dosed. Fecal shedding occurred in 33 (91.7 %) experimentally challenged calves and in none of the control calves. There was a difference in the log-total number of Oocysts counted per gram of feces dry weight among the four exposure groups; calves with the lowest magnitude of exposure (1 × 10(3) Oocysts) shed less than the other three groups. At higher magnitudes of exposure, there was more variability in the range of fecal oocyst shedding. There was an inverse relationship between the log-total amount of Oocysts counted per gram of feces dry weight and the number of days to the onset of fecal shedding per calf, i.e., the more time that elapsed to the onset of fecal shedding, the fewer Oocysts that were shed. The pattern of fecal shedding over time for all calves shedding Oocysts was curvilinear; the number of Oocysts increased with time, reached a peak, and declined. Therefore, the dynamics of oocyst shedding can be influenced in part by limiting exposure among calves and delaying the onset of fecal oocyst shedding.
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significance of wall structure macromolecular composition and surface polymers to the survival and transport of cryptosporidium parvum Oocysts
Applied and Environmental Microbiology, 2010Co-Authors: Michael B Jenkins, Dwight D Bowman, Barbara S Eaglesham, Larry Cameron Anthony, Scott C Kachlany, William C GhiorseAbstract:The structure and composition of the oocyst wall are primary factors determining the survival and hydrologic transport of Cryptosporidium parvum Oocysts outside the host. Microscopic and biochemical analyses of whole Oocysts and purified oocyst walls were undertaken to better understand the inactivation kinetics and hydrologic transport of Oocysts in terrestrial and aquatic environments. Results of microscopy showed an outer electron-dense layer, a translucent middle layer, two inner electron-dense layers, and a suture structure embedded in the inner electron-dense layers. Freeze-substitution showed an expanded glycocalyx layer external to the outer bilayer, and Alcian Blue staining confirmed its presence on some but not all Oocysts. Biochemical analyses of purified oocyst walls revealed carbohydrate components, medium- and long-chain fatty acids, and aliphatic hydrocarbons. Purified walls contained 7.5% total protein (by the Lowry assay), with five major bands in SDS-PAGE gels. Staining of purified oocyst walls with magnesium anilinonaphthalene-8-sulfonic acid indicated the presence of hydrophobic proteins. These structural and biochemical analyses support a model of the oocyst wall that is variably impermeable and resistant to many environmental pressures. The strength and flexibility of oocyst walls appear to depend on an inner layer of glycoprotein. The temperature-dependent permeability of oocyst walls may be associated with waxy hydrocarbons in the electron-translucent layer. The complex chemistry of these layers may explain the known acid-fast staining properties of Oocysts, as well as some of the survival characteristics of Oocysts in terrestrial and aquatic environments. The outer glycocalyx surface layer provides immunogenicity and attachment possibilities, and its ephemeral nature may explain the variable surface properties noted in oocyst hydrologic transport studies.
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using flow cytometry to determine the viability of cryptosporidium parvum Oocysts extracted from spiked environmental samples in chambers
Parasitology Research, 2002Co-Authors: Satomi Kato, Dwight D BowmanAbstract:Cryptosporidium parvum oocyst viability was determined by a dye permeability assay using a flow cytometric method. Oocysts were inoculated into small chambers with soil and biosolids. Oocysts extracted from soil and biosolids were then stained with propidium iodide (PI) and labeled with a fluorescein isothiocyanate (FITC)-conjugated monoclonal antibody. The oocyst population in each sample was determined using forward and side scatter plots, then further analyzed with fluorescence. A red and green fluorescence detector using gates established single populations of unstained, PI-stained, or FITC-labeled Oocysts. No statistical difference was observed between viability of Oocysts extracted from soil and biosolids as determined by either flow cytometry or microscopy. The location of excysted Oocysts was changed in forward and side scatter plots. Results indicated that, although Oocysts are not identified if they excyst, the flow cytometric method could be used to determine oocyst viability from spiked environmental samples.
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Inactivation of Cryptosporidium parvum Oocysts in field soil.
Southeast Asian Journal of Tropical Medicine and Public Health, 2001Co-Authors: Satomi Kato, William C Ghiorse, Michael B Jenkins, Elizabeth A. Fogarty, Dwight D BowmanAbstract:Cryptosporidium parvum Oocysts from dairy calves are believed to regularly contaminate watersheds. Identifying Oocysts and measuring their viability in the natural environment are important elements in estimating the riskposed by this resistant organism. A 152 day field study was conducted to measure the viabilities of Oocysts inoculated into 25 sampling points. Water potential, pH, and ammonium content were also measured at the same 25 sampling sites. A three-dimensional mapping program (Surfer®) was used to create 3-D maps of the viabilities of C. parvum Oocysts and other factors measured during the experiment. The results indicate that 3-D graphical presentation may be a useful means to identify potential sites of greatest risk of oocyst survival and could indicate areas where natural conditions are causing the most rapid oocyst inactivation, and this method can be a means for the future measurement of microorganism inactivation in the natural environment.
William C Ghiorse - One of the best experts on this subject based on the ideXlab platform.
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significance of wall structure macromolecular composition and surface polymers to the survival and transport of cryptosporidium parvum Oocysts
Applied and Environmental Microbiology, 2010Co-Authors: Michael B Jenkins, Dwight D Bowman, Barbara S Eaglesham, Larry Cameron Anthony, Scott C Kachlany, William C GhiorseAbstract:The structure and composition of the oocyst wall are primary factors determining the survival and hydrologic transport of Cryptosporidium parvum Oocysts outside the host. Microscopic and biochemical analyses of whole Oocysts and purified oocyst walls were undertaken to better understand the inactivation kinetics and hydrologic transport of Oocysts in terrestrial and aquatic environments. Results of microscopy showed an outer electron-dense layer, a translucent middle layer, two inner electron-dense layers, and a suture structure embedded in the inner electron-dense layers. Freeze-substitution showed an expanded glycocalyx layer external to the outer bilayer, and Alcian Blue staining confirmed its presence on some but not all Oocysts. Biochemical analyses of purified oocyst walls revealed carbohydrate components, medium- and long-chain fatty acids, and aliphatic hydrocarbons. Purified walls contained 7.5% total protein (by the Lowry assay), with five major bands in SDS-PAGE gels. Staining of purified oocyst walls with magnesium anilinonaphthalene-8-sulfonic acid indicated the presence of hydrophobic proteins. These structural and biochemical analyses support a model of the oocyst wall that is variably impermeable and resistant to many environmental pressures. The strength and flexibility of oocyst walls appear to depend on an inner layer of glycoprotein. The temperature-dependent permeability of oocyst walls may be associated with waxy hydrocarbons in the electron-translucent layer. The complex chemistry of these layers may explain the known acid-fast staining properties of Oocysts, as well as some of the survival characteristics of Oocysts in terrestrial and aquatic environments. The outer glycocalyx surface layer provides immunogenicity and attachment possibilities, and its ephemeral nature may explain the variable surface properties noted in oocyst hydrologic transport studies.
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Inactivation of Cryptosporidium parvum Oocysts in field soil.
Southeast Asian Journal of Tropical Medicine and Public Health, 2001Co-Authors: Satomi Kato, William C Ghiorse, Michael B Jenkins, Elizabeth A. Fogarty, Dwight D BowmanAbstract:Cryptosporidium parvum Oocysts from dairy calves are believed to regularly contaminate watersheds. Identifying Oocysts and measuring their viability in the natural environment are important elements in estimating the riskposed by this resistant organism. A 152 day field study was conducted to measure the viabilities of Oocysts inoculated into 25 sampling points. Water potential, pH, and ammonium content were also measured at the same 25 sampling sites. A three-dimensional mapping program (Surfer®) was used to create 3-D maps of the viabilities of C. parvum Oocysts and other factors measured during the experiment. The results indicate that 3-D graphical presentation may be a useful means to identify potential sites of greatest risk of oocyst survival and could indicate areas where natural conditions are causing the most rapid oocyst inactivation, and this method can be a means for the future measurement of microorganism inactivation in the natural environment.
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assessment of a dye permeability assay for determination of inactivation rates of cryptosporidium parvum Oocysts
Applied and Environmental Microbiology, 1997Co-Authors: Michael B Jenkins, Dwight D Bowman, Lynne J Anguish, Mark Walker, William C GhiorseAbstract:The ability to determine inactivation rates of Cryptosporidium parvum Oocysts in environmental samples is critical for assessing the public health hazard of this gastrointestinal parasite in watersheds. We compared a dye permeability assay, which tests the differential uptake of the fluorochromes 4'-6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI) by the Oocysts (A. T. Campbell, L. J. Robertson, and H. V. Smith, Appl. Environ. Microbiol. 58:3488-3493, 1992), with an in vitro excystation assay, which tests their ability to excyst and, thus, their metabolic potential and potential for infectivity (J.B. Rose, H. Darbin, and C.P. Gerba, Water Sci. Technol. 20:271-276, 1988). Formaldehyde-fixed (killed) Oocysts and untreated Oocysts were permeabilized with sodium hypochlorite and subjected to both assays. The results of the dye permeability assays were the same, while the excystation assay showed that no excystation occurred in formaldehyde-fixed Oocysts. This confirmed that oocyst wall permeability, rather than metabolic activity potential, was the basis of the dye permeability viability assessment. A previously developed protocol (L. J. Anguish and W. C. Ghiorse, Appl. Environ. Microbiol. 63:724-733, 1997) for determining viability of Oocysts in soil and sediment was used to examine further the use of oocyst permeability status as an indicator of oocyst viability in fecal material stored at 4 degrees C and in water at various temperatures. Most of the Oocysts in fresh calf feces were found to be impermeable to the fluorochromes. They were also capable of excystation, as indicated by the in vitro excystation assay, and were infective, as indicated by a standard mouse infectivity assay. The dye permeability assay further showed that an increase in the intermediate population of Oocysts permeable to DAPI but not to PI occurred over time. There was also a steady population of Oocysts permeable to both dyes. Further experiments with purified Oocysts suspended in distilled water showed that the shift in oocyst populations from impermeable to partially permeable to fully permeable was accelerated at temperatures above 4 degrees C. This sequence of oocyst permeability changes was taken as an indicator of the oocyst inactivation pathway. Using the dye permeability results, inactivation rates of Oocysts in two fecal pools stored in the dark at 4 degrees C for 410 and 259 days were estimated to be 0.0040 and 0.0056 oocyst day-1, respectively. The excystation assay gave similar inactivation rates of 0.0046 and 0.0079 oocyst day-1. These results demonstrate the utility of the dye permeability assay as an indicator of potential viability and infectivity of Oocysts, especially when combined with improved microscopic methods for detection of Oocysts in soil, turbid water, and sediments.
H V Smith - One of the best experts on this subject based on the ideXlab platform.
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molecular fingerprinting of cryptosporidium Oocysts isolated during water monitoring
Applied and Environmental Microbiology, 2006Co-Authors: R.a.b. Nichols, B M Campbell, H V SmithAbstract:We developed and validated a PCR-based method for identifying Cryptosporidium species and/or genotypes present on oocyst-positive microscope slides. The method involves removing coverslips and Oocysts from previously examined slides followed by DNA extraction. We tested four loci, the 18S rRNA gene (N18SDIAG and N18SXIAO), the Cryptosporidium oocyst wall protein (COWP) gene (STN-COWP), and the dihydrofolate reductase (dhfr) gene (by multiplex allele-specific PCR), for amplifying DNA from low densities of Cryptosporidium parvum Oocysts experimentally seeded onto microscope slides. The N18SDIAG locus performed consistently better than the other three tested. Purified Oocysts from humans infected with C. felis, C. hominis, and C. parvum and commercially purchased C. muris were used to determine the sensitivities of three loci (N18SDIAG, STN-COWP, and N18SXIAO) to detect low oocyst densities. The N18SDIAG primers provided the greatest number of positive results, followed by the N18SXIAO primers and then the STN-COWP primers. Some oocyst-positive slides failed to generate a PCR product at any of the loci tested, but the limit of sensitivity is not entirely based on oocyst number. Sixteen of 33 environmental water monitoring Cryptosporidium slides tested (oocyst numbers ranging from 1 to 130) contained mixed Cryptosporidium species. The species/genotypes most commonly found were C. muris or C. andersoni, C. hominis or C. parvum, and C. meleagridis or Cryptosporidium sp. cervine, ferret, and mouse genotypes. Oocysts on one slide contained Cryptosporidium muskrat genotype II DNA.
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effect of three concentration techniques on viability of cryptosporidium parvum Oocysts recovered from bovine feces
Journal of Clinical Microbiology, 1995Co-Authors: Zia Bukhari, H V SmithAbstract:Bovine fecal samples (1 g) negative for Cryptosporidium sp. Oocysts were seeded with 7 x 10(4) Cryptosporidium parvum Oocysts and purified by either water-ether concentration, sucrose density flotation, or zinc sulfate flotation to evaluate oocyst recovery. The effect of these purification techniques on the viability of recovered Oocysts was also evaluated. Significantly higher numbers of seeded Oocysts were recovered by water-ether concentration (recovery rate, 46 to 75%) than by sucrose density (24 to 65%) or zinc sulfate (22 to 41%) flotation methods. In addition, water-ether concentration did not exert a significant effect on the viability of the population of Oocysts recovered, whereas sucrose density flotation and zinc sulfate flotation selectively concentrated viable Oocysts. The water-ether concentration procedure is recommended for use in epidemiological studies in which both oocyst enumeration and viability assessment are required.
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survival of cryptosporidium parvum Oocysts under various environmental pressures
Applied and Environmental Microbiology, 1992Co-Authors: Lucy J Robertson, A T Campbell, H V SmithAbstract:The survival of various isolates of Cryptosporidium parvum Oocysts under a range of environmental pressures including freezing, desiccation, and water treatment processes and in physical environments commonly associated with Oocysts such as feces and various water types was monitored. Oocyst viability was assessed by in vitro excystation and by a viability assay based on the exclusion or inclusion of two fluorogenic vital dyes. Although desiccation was found to be lethal, a small proportion of Oocysts were able to withstand exposure to temperatures as low as -22 degrees C. The water treatment processes investigated did not affect the survival of Oocysts when pH was corrected. However, contact with lime, ferric sulfate, or alum had a significant impact on oocyst survival if the pH was not corrected. Oocysts demonstrated longevity in all water types investigated, including seawater, and when in contact with feces were considered to develop an enhanced impermeability to small molecules which might increase the robustness of the Oocysts when exposed to environmental pressures.
Thanh H Nguyen - One of the best experts on this subject based on the ideXlab platform.
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Transport of Cryptosporidium parvum Oocysts in a silicon micromodel.
Environmental Science & Technology, 2012Co-Authors: Changyong Zhang, Markus Hilpert, Theresa B. Kuhlenschmidt, Mark S. Kuhlenschmidt, Thanh H NguyenAbstract:Effective removal of Cryptosporidium parvum Oocysts by granular filtration requires the knowledge of oocyst transport and deposition mechanisms, which can be obtained based on real time microscopic observation of oocyst transport in porous media. Attachment of Oocysts to silica surface in a radial stagnation point flow (RSPF) cell and in a micromodel, which has 2-dimensional (2-D) microscopic pore structures consisting of an array of cylindrical collectors, was studied and compared. Real time transport of Oocysts in the micromodel was recorded to determine the attached oocyst distributions in transversal and longitudinal directions. In the micromodel, Oocysts attached to the forward portion of clean collectors, where the flow velocity was lowest. After initial attachment, Oocysts attached onto already attached Oocysts. As a result, the collectors ripened and the region available for flow was reduced. Results of attachment and detachment experiments suggest that surface charge heterogeneity allowed for oocyst attachment. In addition to experiments, Lattice-Boltzmann simulations helped understanding the slightly non-uniform flow field and explained differences in the removal efficiency in the transversal direction. However, the hydrodynamic modeling could not explain differences in attachment in the longitudinal direction.
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Transport of Cryptosporidium parvum Oocysts in a silicon micromodel.
Environmental Science & Technology, 2012Co-Authors: Changyong Zhang, Markus Hilpert, Theresa B. Kuhlenschmidt, Mark S. Kuhlenschmidt, Thanh H NguyenAbstract:Effective removal of Cryptosporidium parvum Oocysts by granular filtration requires the knowledge of oocyst transport and deposition mechanisms, which can be obtained based on real time microscopic observation of oocyst transport in porous media. Attachment of Oocysts to silica surface in a radial stagnation point flow (RSPF) cell and in a micromodel, which has 2-dimensional (2-D) microscopic pore structures consisting of an array of cylindrical collectors, was studied and compared. Real time transport of Oocysts in the micromodel was recorded to determine the attached oocyst distributions in transversal and longitudinal directions. In the micromodel, Oocysts attached to the forward portion of clean collectors, where the flow velocity was lowest. After initial attachment, Oocysts attached onto already attached Oocysts. As a result, the collectors ripened and the region available for flow was reduced. Results of attachment and detachment experiments suggest that surface charge heterogeneity allowed for oocyst attachment. In addition to experiments, Lattice-Boltzmann simulations helped understanding the slightly non-uniform flow field and explained differences in the removal efficiency in the transversal direction. However, the hydrodynamic modeling could not explain differences in attachment in the longitudinal direction.
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Composition and conformation of Cryptosporidium parvum oocyst wall surface macromolecules and their effect on adhesion kinetics of Oocysts on quartz surface.
Biomacromolecules, 2010Co-Authors: Yuanyuan Liu, Theresa B. Kuhlenschmidt, Mark S. Kuhlenschmidt, Thanh H NguyenAbstract:We characterized the composition and conformation of Cryptosporidium parvum (C. parvum) oocyst wall surface macromolecules and studied their effect on interactions between C. parvum oocyst and quartz surface. Proteinase K and mixed glycosidases were used to modify C. parvum oocyst surface macromolecules. The peptides released by proteinase K and carbohydrates hydrolyzed by mixed glycosidases were respectively analyzed with liquid chromatography/nanoelectrospray ionization tandem mass spectrometry (LC-MS/MS) and phenol-sulfuric acid assay to determine the composition of C. parvum oocyst wall surface macromolecules. Surface potential and polarity of the untreated and proteinase treated C. parvum Oocysts revealed information about the conformation of oocyst wall surface macromolecules. The results illustrated that C. parvum oocyst wall is covered by a fluffy layer of glycoproteins. Adhesion kinetics of untreated and proteinase K treated C. parvum Oocysts on quartz surface were studied in a radial stagnation ...
