Electronegative Filters Research Articles

Recovery of human norovirus from water by virus concentration methods

The aim of this study was to evaluate the applicability of virus concentration methods to detect human norovirus (HuNoV) in water. One conventional virus concentration method using an electropositive filter (1MDS-method) and two methods developed by our research group using an electronegative filter (Mg-method and Al-method) were subjected to recovery tests of the HuNoV strain GII.4, which was obtained from a diarrhea patient, and poliovirus (PV) type 1 inoculated into 5 kinds of water samples. The mean recovery yields of HuNoV by the Mg-method, determined by real-time PCR, were 186%, 80%, 167%, 15%, and 39% for MilliQ water, tap water, bottled water, river water, and pond water, respectively ( n = 2 each), which were generally comparable to those of PV. A similar trend was observed for the Al-method ( n = 8 in total), suggesting that both Mg- and Al-methods can be appropriate for concentrating HuNoVs from water samples. Unlike these two methods, no clear correlation was found between the recovery of HuNoV and PV by the 1MDS-method ( n = 6 in total). This study is significant because it provides observations on the use of virus concentration methods for the detection of uncultivable HuNoV in water samples.

Quantitative detection of sapoviruses in wastewater and river water in Japan

To detect sapoviruses at a wastewater treatment plant (WWTP) and in a river in Japan, quantitatively. Influent and effluent samples at a WWTP and river water samples were collected monthly for 1 year. The water samples were subjected to virus concentration using an HA electronegative filter, followed by quantification of sapoviruses using real-time PCR. The concentration of sapoviruses in influent ranged from 2.8 x 10(3) to 1.3 x 10(5) copies per litre, showing a higher value in winter. Seven (58%) of 12 effluent samples were positive for sapoviruses, as were 23 (64%) of 36 river water samples collected from three sites along the Tamagawa River. Sapoviruses were abundant in the influent even in the nonepidemic period, suggesting that sporadic and asymptomatic infections occur throughout the year. Increasing concentration of sapoviruses was discharged into the river during the epidemic period winter. This is the first study demonstrating the quantitative detection of sapoviruses in aquatic environments.

Concentration of enteric adenovirus 40 from tap, sea and waste water

The enteric adenovirus types 40 (Ead 40) and 41 (Ead 41) are the second most common cause of viral gastroenteritis in children. Since their occurrence in the aquatic environment is unknown, their role as waterborne pathogens has not been determined. This study evaluated the ability of electronegative microporous filters to recover Ead 40 from tap water, secondary treated sewage, and artificial and natural sea waters, and the ability of electropositive microporous filters to recover Ead 40 from tap water. The efficiency of organic flocculation and PEG precipitation to reconcentrate Ead 40 from beef extract eluents was also assessed. Viral assays were conducted by the TCID 50 method in PLC/PRF/5 cells. With electronegative filters, recovery efficiencies of 36, 38, and 22% were obtained from 113-1. volumes of tap, sea water, and secondary sewage, respectively, using electropositive filters Ead 40 was recovered from tap water, with an efficiency of 26.5%. No significant difference was observed, by paired t-test analysis, when comparing the concentration efficiencies between organic flocculation (38.6%), and PEG precipitation (40%). These results show that Ead 40 can be concentrated from water samples, with efficiencies comparable to other enteric viruses.

Detection of enteroviruses in marine waters by direct RT-PCR and cell culture

Sewage outfalls and storm water runoff introduces pathogenic human enteric viruses into marine coastal waters, which may pose a potential public health risk. Although members of the enterovirus group have been suggested as possible indicators of sewage pollution in marine waters, the lack of rapid, sensitive and cost effective methods have prevented routine monitoring in the United States. This study compared traditional cell culture and direct RT-PCR (reverse transcriptase-polymerase chain reaction) amplification for detection of an enterovirus. Poliovirus could be recovered from 100 L of artificial seawater with an average efficiency of 77%, using adsorption and elution from electronegative filters. Viruses were eluted from the filters with 1.5% beef extract for viruses (BEV) adjusted to pH 9.5 and reconcentrated by organic flocculation to a volume of 30 mL. Substances which interfered with detection by RT-PCR were removed by treatment of the concentrates with sephadex and chelex resins. Direct RT-PCR could detect 2.5 and 0.025 PFU (plaque forming units) for single (25 cycles) and double PCR (2 × 25 cycles) in 10 μL of pure culture poliovirus samples, respectively. These methods are currently being applied to assess the occurrence of enteroviruses at marine bathing beaches influenced by sewage discharges.

Detection of enteroviruses in marine waters by direct RT-PCR and cell culture

Sewage outfalls and storm water runoff introduces pathogenic human enteric viruses into marine coastal waters, which may pose a potential public health risk. Although members of the enterovirus group have been suggested as possible indicators of sewage pollution in marine waters, the lack of rapid, sensitive and cost effective methods have prevented routine monitoring in the United States. This study compared traditional cell culture and direct RT-PCR (reverse transcriptasepolymerase chain reaction) amplification for detection of an enterovirus. Poliovirus could be recovered from 100 L of artificial seawater with an average efficiency of 77%, using adsorption and elution from electronegative filters. Viruses were eluted from the filters with 1.5% beef extract for viruses (BEV) adjusted to pH 9.5 and reconcentrated by organic flocculation to a volume of 30 mL. Substances which interfered with detection by RT-PCR were removed by treatment of the concentrates with sephadex and chelex resins. Direct RT-PCR could detect 2.5 and 0.025 PFU (plaque forming units) for single (25 cycles) and double PCR (2 × 25 cycles) in 10 µL of pure culture poliovirus samples, respectively. These methods are currently being applied to assess the occurrence of enteroviruses at marine bathing beaches influenced by sewage discharges.

Elimination of Coliphages, Clostridium perfringens and Human Enteric Viruses during Drinking Water Treatment: Results of Large Volume Samplings

Using a single filtration method of 100 L (raw and settled water) or 1000 L (filtered and tap water) volumes, the elimination of human enteric viruses, coliphages and Clostridium perfringens was studied during drinking water treatment. The VIRADEL method was used for the concentration of these microorganisms on electronegative filters. Concentrates were assayed for human enteric viruses on MA-104 cells using two blind passages and our HISG-immunoperoxidase method. Coliphages were assayed by plaque assay using a nalidixic-acid resistant (selected in our laboratory) ATCC 13706 E. coli host strain by thé doulle layer agar method. Clostridium perfringens were enumerated by membrane filtration on m-CP agar (Difco). The water filtration plant studied uses full conventional treatment including ozonation and post-chlorination. The results obtained suggest that, using similar volumes of waters for the detection of these indicators, coliphages and C. perfringens are slightly more resistant than cultivable human enteric viruses and that they could thus serve as rapid indicators for the elimination of human enteric viruses in treated waters.

A highly efficient second-step concentration technique for bacteriophages and enteric viruses using ammonium sulfate and Tween 80.

Addition of Tween 80 to a 1.5% solution of beef extract was found to enhance the elution of bacteriophages adsorbed to electronegative filters. When reconcentration of the eluate was attempted by ammonium sulfate precipitation, a floating layer containing most of the viruses was formed. This floating layer can be obtained with several nonionic detergents including Tween 80 and under a salt saturation of 55% with ammonium sulfate, potassium tartrate, and sodium phosphate. Virus recovery ranged from 91 to 103% and was obtained with several bacteriophage strains. With poliovirus type 1, coxsackievirus B-4, and rotavirus SA-11 the recoveries were 100, 20, and 80%, respectively, but toxicity to cell culture was encountered: after removal of the detergent by a second floating layer method the recovery was 32% for poliovirus. Compared with organic flocculation, this method also had both improved recovery for bacteriophages and protective properties for samples frozen at -70 degrees C.

Wound fiberglass depth filters as a less expensive approach for the concentration of viruses from water.

Wound fiberglass depth cartridge filters (25.4 cm) with a nominal porosity of 1 micron were used to concentrate viruses from large volumes of surface water. They were found to be an excellent, less expensive alternative to the 0.2-micron pleated cartridge filters normally used for the concentration of enteric viruses from water. More than 99% of experimentally seeded poliovirus was adsorbed to these filters when the pH of the water was adjusted to pH 3.5 and aluminium chloride was added to a final concentration of 0.001 M, as recommended for electronegative filters. In comparative recovery of indigenous viruses from river water, similar results were obtained with two 1-micron or a 3-microns + 0.2-micron filter combination. The cost of the two 1-micron filters is about Can. $26, while it is about Can. $58 for the other combination.

Humic acid interference with virus recovery by electropositive microporous filters.

The effects of humic acid on poliovirus type 1 recovery from water by Zeta Plus 60S filters were investigated. The humic acid interfered by preventing virus adsorption to the filters, and the interference increased as a function of the amount of humic acid filtered. Humic acid decreased virus adsorption when filtered before the virus, but did not elute virus which had adsorbed to the filters. The effects on virus recovery were not due to alterations in virus titer or neutralizability. The addition of AlCl3, which improved virus recovery by electronegative filters in the presence of humic acid, did not aid in overall virus recovery by the Zeta Plus filters in the presence or absence of humic acid. However, the salt and humic acid in combination improved virus adsorption and concurrently reduced virus elution efficiency. The addition of NaH2PO4 had no direct effect on virus recovery and did not alter the effect of humic acid. In an attempt to identify the components of humic acid responsible for the interference, humic materials were fractionated by size by using Sephadex gel chromatography and dialysis, and the fractions were tested for interfering activity. Interference was not associated with specific size fractions of the humic materials.

Capture of latex beads, bacteria, endotoxin, and viruses by charge-modified filters.

This report demonstrates how electropositive filters can be used to enhance the removal of microorganisms and other negatively charged particles from water. It was shown that electropositive depth filters were capable of adsorbing viruses and endotoxins many times smaller than the average pore size of the filter. Electronegative filters of similar porosity or electropositive filters that had been treated to destroy the positive charge were almost ineffective under similar conditions for the removal of viruses and small latex spheres. The results of this study indicate that electropositive filters are highly effective in the removal of a wide range of contaminants over a wide range of pH values and ionic conditions.