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Biomedical subjects

C Wallis

Publications and source records attributed to C Wallis.

At least 109 records · Page 6Linked to original sources
PubMed1978

A simple method for concentration of enteroviruses and rotaviruses from cell culture harvests using membrane filters.

Organic compounds in cell culture harvests known as membrane-coating components (MCC) prevent virus adsorption to membrane filters. Blending cell culture harvests with fluorocarbon removed the MCC and permitted adsorption of virus in acidified harvests to epoxy-fiberglass filters. Subsequent elution with high pH buffer resulted in recovery of greater than 90% of the virus with concentrations of up to 100-fold.

Enterovirus↗
PubMed1978

Viruses in water.

Attention is drawn in this paper to the increasing problem of viral contamination of water and shellfish, particularly since growing demands for available water resources by a rising world population and expanding industry will make the recycling of wastewater almost inevitable in the future. The problem of eliminating viruses pathogenic for man from water is considered in the light of present water treatment procedures, which are often inadequate for that purpose. Man may be exposed to waterborne viruses through the consumption of contaminated water, shellfish, or crops, as a result of recreational activities involving water, or from aerosols following the spraying of crops with liquid wastes. Physical and chemical methods of eliminating viruses from water are discussed.

Humans↗
PubMed1977

Inactivation of clay-associated bacteriophage MS-2 by chlorine.

The model system consisted of bacteriophage MS-2, bentonite clay, and hypochlorous acid (HOC1). Factors that influenced association of the bacterial virus with bentonite were the titer of unadsorbed viruses, clay concentration, cation concentration, temperature, stirring rate, and the presence of soluble organics. Variation of the kinetic adsorption rate constant with stirring speed indicates that phage attachment is a diffusion-limited process; the attachment reaction has an apparent activation energy of 1 kcal/mol. About 18% of clay-associated bacteriophages was recovered by mixing the suspension with an organic eluent. Inactivation data were obtained from batch reactors operated under those conditions in which loss of HOC1 was minimal during the reaction. Bacteriophages attached to clay were more resistant to HOC1 than were freely suspended phages; for equivalent HOC1 concentrations, clay-associated phages required about twice the time that freely suspended phages required for loss of 99% of the initial virus titer.

Adsorption↗
PubMed1977

Concentration of enteroviruses from estuarine water.

Pleated cartridge filters readily adsorb viruses in estuarine water at low pH containing aluminum chloride. Adsorbed viruses are efficiently recovered by treating filters with glycine buffer at high pH. By using these procedures, it was possible to recover approximately 70% of the poliovirus added to 400 liters of estuarine water in 3 liters of filter eluate. Reconcentration of virus in the filter eluate in small volumes that are convenient for viral assays was more difficult. Reconcentration methods described previously for eluates from filters that process tap water or treated wastewater were inadequate when applied to eluates from filters used to process estuarine water containing large amounts of organic compounds. Two methods were found to permit efficient concentration of virus in filter eluates in small volumes. In both methods, virus in 3 liters of filter eluate was adsorbed to aluminum hydroxide flocs and then recovered in approximately 150 ml of buffered fetal calf serum. Additional reductions in volume were achieved by ultrafiltration or hydroextraction. By using these procedures 60 to 80% of the virus in 3 liters of filter eluate could be recovered in a final volume of 10 to 40 ml.

Adsorption↗
PubMed1977

Concentration of enteroviruses from large volumes of turbid estuary water.

A method is described for the efficient concentration of viruses from large volumes of highly turbid estuary water. Virus in acidified seawater in the presence of aluminum chloride is adsorbed to a 10-in. (about 25.4 cm) fibreglass depth cartridge and 2- and 0.65-micron epoxy-fibreglass filters in series. This filter series is capable of efficiently adsorbing enteroviruses from 50 U.S. gallons (about 190) of estuary water of varying salinity and turbidity. Adsorbed viruses were eluted from the filters with glycine buffer (pH 11.5) and the eluate reconcentrated by using a precipitate formed by the addition of ferric chloride. Viruses were eluted from this precipitate with fetal calf serum. Using this procedure, four different enteroviruses in 50 gallons (about 190) of estuary water were concentrated 9 000- to 12 000-fold with an overall efficiency of 41%.

Aluminum↗
PubMed1976

Wastewater renovation and reuse: virus removal by soil filtration.

Secondary sewage effluent and renovated water from four wells at the Flushing Meadows Wastewater Renovation Project near Phoenix, Arizona, in operation since 1967, were assayed approximately every 2 months in 1974 for viruses during flooding periods. Viruses, regularly found in the secondary effluent, were not detected in any renovated water samples. Our results indicated that human viral pathogens do not move through soil into the groundwater, but are apparently absorbed and degraded by the soil and reduced in numbers by a factor of at least 10(4) (99.99 percent removal).

Sanitary Engineering↗
PubMed1976

Concentration of viruses from large volumes of tap water using pleated membrane filters.

A method is described for the efficient concentration of viruses from large volumes of tap water in relatively short time periods. Virus in acidified tap water in the presence of aluminum chloride is adsorbed to a 10-inch (ca. 25.4 cm) fiberglass depth cartridge and a 10-inch pleated epoxy-fiberglass filter in series at flow rates of up to 37.8 liters/min (10 gallons/min). This filter series is capable of efficiently adsorbing virus from greater than 19,000 liters (5,000 gallons) of treated tap water. Adsorbed viruses are eluted from the filters with glycine buffer (pH 10.5) and the eluate is reconcentrated using an aluminum flocculation process. Viruses are eluted from the aluminum floc with glycine buffer (pH 11.5). Using this procedure, viruses in 1,900 liters (500 gallons) of tap water can be concentrated 100,000-fold in 3 h with an average recovery of 40 to 50%.

Adsorption↗
PubMed1976

Virus and bacteria removal from wastewater by land treatment.

Secondary sewage effluent and renovated water from four wells at the Flushing Meadows Wastewater Renovation Project near Phoenix, Arizona, in operation since 1967, were assayed approximately every 2 months in 1974 for viruses and enteric bacteria during flooding periods. No viruses of Salmonella sp. were detected in any renovated well water samples, and the numbers of fecal coliforms, fecal streptococci, and total bacteria were decreased by about 99.9% in the renovated well waters after the wastewater was filtered through about 9 m of soil.

Arizona↗
PubMed1976

Reconcentration of poliovirus from sewage.

Virus can be adsorbed from effluents of sewage treatment plants on large-surface membranes. Subsequent elution of virus requires large volumes, which in turn requires reconcentration of virus for assay. However, reconcentration of such viral eluates on small adsorbent surfaces is difficult because certain soluble sewage components are adsorbed along with the virus on the initial virus adsorbent and are removed along with the virus by the eluent. Upon acidification of the initial eluate to reconcentrate the virus on smaller membrane surfaces, flocs are formed that interfere with the reconcentration process. To circumvent this problem, the interfering sewage components can be removed by activated carbon and ion-exchange resins. The virus is then readily reconcentrated on small membranes.

Adsorption↗
PubMed1976

Concentration and purification of enteroviruses by membrane chromatography.

A simple procedure for the concentration and partial purification of enteroviruses from tissue culture harvests is described. After removal of acid-precipitating components with a cationic detergent, the detergent and most membrane-coating components were removed by treatment with a cationic-exchange resin. The resin effluent was then acidified, and the virus was adsorbed to epoxy-fiberglass membranes. Virus was then eluted with pH 11.5 glycine-NaOH buffer. Since this eluate contains no orgcentrated simply by acidifying the eluate and passing it through a smaller membrane than that used for the first concentration. As high as 500-fold concentrations can be achieved, with a high efficiency of recovery.

Adsorption↗
PubMed1975

Development of a simple method for concentrating enteroviruses from oysters.

The development of a simple method for concentrating enteroviruses from oysters is described. In this method viruses in homogenized oyster tissues are efficiently absorbed to oyster solids at pH 5.5 and low salt concentration. After low-speed centrifugation, the supernatant is discarded and viruses are eluted from the sedimented oyster solids by resuspending them in pH 3.5 glycine-buffered saline. The solids are then removed by low-speed centrifugation, and the virus-containing supernatant is filtered through a 0.2-micronm porosity filter to remove bacteria and other small particulates without removing viruses. The virus-containing filtrate is then concentrated to a volume of a few milliliters by ultrafiltration, and the concentrate obtained is inoculated directly into cell cultures for virus assay. When tested with pools of oysters experimentally contaminated with small amounts of different enteroviruses, virus recovery efficiency averaged 63%.

Adsorption↗
PubMed1975

Microbiological hazards of household toilets: droplet production and the fate of residual organisms.

Large numbers of bacteria and viruses when seeded into household toilets were shown to remain in the bowl after flushing, and even continual flushing could not remove a persistent fraction. This was found to be due to the adsorption of the organsims to the porcelain surfaces of the bowl, with gradual elution occuring after each flush. Droplets produced by flushing toilets were found to harbor both bacteria and viruses which had been seeded. The detection of bacteria and firuses falling out onto surfaces in bathrooms after flushing indicated that they remain airborne long enough to settle on surfaces throughout the bathroom. Thus, there is a possibility that a person may acquire an infection from an aerosol produced by a toilet.

Adsorption↗
PubMed1975

Studies on the survival and fate of enteroviruses in an experimental model of a municipal solid waste landfill and leachate.

In laboratory scale municipal solid waste lysimeters containing simulated refuse, and seeded with either laboratory or field strains of poliovirus type 1 and echovirus type 7, viruses were not detected in the lysimeter leachate produced over a 4-month period. In addition, viruses were detected in the lysimeter refuse contents after termination of lysimeter operation. These results appeared to be due to virus retention in the lysimeter caused by virus adsorption and virus inactivation. Evidence for virus inactivation was provided by the results of experiments on virus inactivation in composite leachate samples. Evidence for virus adsorption was supported by the rapid adsorption of viruses to various municipal solid waste components in the presence of a salt similar in composition to the major inorganic salts of leachates.

Adsorption↗