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PubMed1985

Adsorption of viruses to charge-modified silica.

The purpose of this study was to provide a clearer understanding of virus adsorption, focusing specifically on the role of electrostatic interactions between virus particles and adsorbent surfaces. The adsorption of poliovirus 1, reovirus types 1 and 3, and coliphages MS-2 and T2 to colloidal silica synthetically modified to carry either positive or negative surface charge was evaluated. Adsorption experiments were performed by combining virus and silica in 0.1-ionic-strength buffers of pH 4.0, 6.4, and 8.5. Samples agitated for specified adsorption periods were centrifuged to pellet adsorbent particles plus adsorbed virus, and the supernatants were assayed for unadsorbed virus. All viruses adsorbed exclusively to negatively charged silica at pH values below their isoelectric points, i.e., under conditions favoring a positive surface charge on the virions. Conversely, all viruses adsorbed exclusively to positively charged silica at pH values above their isoelectric points, i.e., where virus surface charge is negative. Viruses in near-isoelectric state adsorbed to all types of silica, albeit to a lesser degree.

Adsorption↗
PubMed1986

Use of geostatistics to predict virus decay rates for determination of septic tank setback distances.

Water samples were collected from 71 public drinking-water supply wells in the Tucson, Ariz., basin. Virus decay rates in the water samples were determined with MS-2 coliphage as a model virus. The correlations between the virus decay rates and the sample locations were shown by fitting a spherical model to the experimental semivariogram. Kriging, a geostatistical technique, was used to calculate virus decay rates at unsampled locations by using the known values at nearby wells. Based on the regional characteristics of groundwater flow and the kriged estimates of virus decay rates, a contour map of the area was constructed. The map shows the variation in separation distances that would have to be maintained between wells and sources of contamination to afford similar degrees of protection from viral contamination of the drinking water in wells throughout the basin.

Coliphages↗
PubMed1989

Disinfection of model indicator organisms in a drinking water pilot plant by using PEROXONE.

PEROXONE is an advanced oxidation process generated by combining ozone and hydrogen peroxide. This process stimulates the production of hydroxyl radicals, which have been shown to be superior to ozone for the destruction of some organic contaminants. In this study, pilot-scale experiments were conducted to evaluate the microbicidal effectiveness of PEROXONE and ozone against three model indicator groups. Escherichia coli and MS2 coliphage were seeded into the influent to the preozonation contactors of a pilot plant simulating conventional water treatment and were exposed to four ozone dosages (0.5, 1.0, 2.0, and 4.0 mg/liter), four hydrogen peroxide/ozone (H2O2/O3) weight ratios (0, 0.3, 0.5, and 0.8), and four contact times (4, 5, 12, and 16 min) in two source waters--Colorado River water and state project water--of different quality. The removal of heterotrophic plate count bacteria was also monitored. Results of the study indicated that the microbicidal activity of PEROXONE was greatly affected by the applied ozone dose, H2O2/O3 ratio, contact time, source water quality, and type of microorganism tested. At contact times of 5 min or less, ozone alone was a more potent bactericide than PEROXONE at all H2O2/O3 ratios tested. However, this decrease in the bactericidal potency of PEROXONE was dramatic only as the H2O2/O3 ratio was increased from 0.5 to 0.8. The fact that the bactericidal activity of PEROXONE generally decreased with increasing H2O2/O3 ratios was thought to be related to the lower ozone residuals produced. The viricidal activity of PEROXONE and ozone was comparable at all of the H2O2/O3 ratios. Heterotrophic plate count bacteria were the most resistant group of organisms. Greater inactivation of E. coli and MS2 was observed in Colorado River water than in state project water and appeared to result from differences in the turbidity and alkalinity of the two waters. Regardless of source water, greater than 4.5 log10 of E. coli and MS2 was inactivated at an applied ozone dosage of 2.0 mg/liter (and a 4-min contact time) when the H2O2/O3 ratio was less than or equal to 0.5. Comparative disinfection experiments indicated that free chlorine was the most potent bactericidal agent, followed (in descending order of effectiveness) by ozone, PEROXONE, and chloramines. These results indicate that the PEROXONE process must be optimized for each source water to achieve microbicidal effectiveness.

Chloramines↗
PubMed1991

Evaluation of an Escherichia coli host strain for enumeration of F male-specific bacteriophages.

A method was developed for the selective enumeration of F male-specific bacteriophages in samples of environmental waters. The host strain for the phages, Escherichia coli HS(pFamp)R, has three antibiotic resistance markers, ampicillin on the Famp plasmid, which codes for pilus production, and streptomycin and nalidixic acid on the chromosome. The strain is resistant to coliphages T2 to T7 and phi X174. More than 95% of the phages from environmental samples which plaqued on the host strain were F male specific. The host bacterium had a higher plaquing efficiency than E. coli K-12 Hfr for F-specific phages in stock suspensions and sewage effluents. The F male-specific phage levels in prechlorinated, secondary-treated sewage effluents generally were about 10(3) to 10(4) PFU/100 ml. The levels in the influents to the sewage treatment plants and in septic tank contents were about 10(5) PFU/100 ml. RNA-containing phages composed about 90% of the total F-specific phage population in sewage effluents.

Bacteriophage phi X 174↗
PubMed1993

Distribution of viral abundance in the reef environment of Key Largo, Florida.

The distribution of viral and microbial abundance in the Key Largo, Fla., reef environment was measured. Viral abundance was measured by transmission electron microscope direct counts and plaque titer on specific bacterial hosts in water and sediment samples from Florida Bay (Blackwater Sound) and along a transect from Key Largo to the outer edge of the reef tract in Key Largo Sanctuary. Water column viral direct counts were highest in Blackwater Sound of Florida Bay (1.2 x 10(7) viruses per ml), decreased to the shelf break (1.7 x 10(6) viruses per ml), and were inversely correlated with salinity (r = -0.97). Viral direct counts in sediment samples ranged from 1.35 x 10(8) to 5.3 x 10(8)/cm(3) of sediment and averaged nearly 2 orders of magnitude greater than counts in the water column. Viral direct counts (both sediment and water column measurements) exceeded plaque titers on marine bacterial hosts (Vibrio natriegens and others) by 7 to 8 orders of magnitude. Water column viral abundance did not correlate with bacterial direct counts or chlorophyll a measurements, and sediment viral parameters did not correlate with water column microbial, viral, or salinity data. Coliphage, which are indicators of fecal pollution, were detected in two water column samples and most sediment samples, yet their concentrations were relatively low (<2 to 15/liter for water column samples, and <2 to 108/cm(3) of sediment). Our findings indicate that viruses are abundant in the Key Largo environment, particularly on the Florida Bay side of Key Largo, and that processes governing their distribution in the water column (i.e., salinity and freshwater input) are independent of those governing their distribution in the sediment environment.

Animals↗
PubMed1996

Occurrence of airborne bacteria and pathogen indicators during land application of sewage sludge.

Glass impingers (AGI-30) were used at a commercial sludge application site to determine the levels of airborne bacteria and pathogen indicators. Even though heterotrophic bacteria averaged 10(5) CFU/m3, none of the sites showed the presence of Salmonella spp. or indicators such as fecal coliforms or coliphages. Indicators such as H2S producers and pathogenic clostridia were present in locations having significant physical agitation of the sludge material. PCR-based ribotyping using the 16S-23S interspacer region is a promising method to identify the genetic relatedness and origins of airborne clostridia.

Air Microbiology↗
PubMed1996

Immunoaffinity concentration and purification of waterborne enteric viruses for detection by reverse transcriptase PCR.

To assess the risks from viral contamination of drinking-water supplies, there is a clear need for methods to directly detect viral pathogens. In this study, we developed a broad-spectrum immunocapture method for concentration and purification of enteric viruses. The method involved indirect antibody capture (AbCap) of intact viruses followed by release of virion genomic RNA and reverse transcriptase PCR for amplification and oligoprobe hybridization for detection. The procedure involved concentrating enteric viruses from large volumes of water by standard filtration-elution techniques with IMDS filters and 1 liter of 1% beef extract-0.05 M glycine (BE/G) as an eluate. The BE/G eluate was concentrated and purified by polyethylene glycol (PEG) precipitation, Pro-Cipitate (a commercially available protein precipitating reagent) precipitation, and a second PEG precipitation to a volume of approximately 500 mu l. Aliquots of the second PEG precipitate were further processed by RNA extraction, AbCap, or cell culture analysis for infectious viruses. The AbCap method was applied to 11 field samples of fecally contaminated surface water. Of the 11 samples, 9 were positive for enteric viruses by AbCap method 4 of 11 samples were positive for enteric viruses by direct RNA extraction of a small aliquot of the second PEG concentrate; and 4 of 11 samples were positive for enteric viruses by measurement of cell culture infectivity. The results of enteric viruses were compared with those for standard bacterial and coliphage indicators of fecal contamination.

Animals↗
PubMed1999

Comparative survival of free shiga toxin 2-encoding phages and Escherichia coli strains outside the gut.

The behavior outside the gut of seeded Escherichia coli O157:H7, naturally occurring E. coli, somatic coliphages, bacteriophages infecting O157:H7, and Shiga toxin 2 (Stx2)-encoding bacteriophages was studied to determine whether the last persist in the environment more successfully than their host bacteria. The ratios between the numbers of E. coli and those of the different bacteriophages were clearly lower in river water than in sewage of the area, whereas the ratios between the numbers of the different phages were similar. In addition, the numbers of bacteria decreased between 2 and 3 log units in in situ survival experiments performed in river water, whereas the numbers of phages decreased between 1 and 2 log units. Chlorination and pasteurization treatments that reduced by approximately 4 log units the numbers of bacteria reduced by less than 1 log unit the numbers of bacteriophages. Thus, it can be concluded that Stx2-encoding phages persist longer than their host bacteria in the water environment and are more resistant than their host bacteria to chlorination and heat treatment.

Animals↗
PubMed1966

Role of differential air pressure zones in the control of aerosols in a large animal isolation facility.

The uncontrolled transmission of hog cholera in a large animal isolation facility, designed to control the movement of aerosols within and between individual wings of a multiunit building, indicated the need for a critical study of aerosol behavior under existing conditions of operation. Studies with aerosols of Escherichia coli B T3 bacteriophage (T3 coliphage) conclusively demonstrated the impossibility of obtaining the desired control by means of a "static" air balance relationship between adjacent areas within the facility. Modifications needed to provide the desired control of the air-handling system are outlined and discussed.

Aerosols↗
PubMed1969

Glutaraldehyde inactivation of virus in tissue.

High concentrations of influenza virus and T3 coliphage were inoculated into mouse tissue blocks. Exposure of the inoculated tissue blocks to 5% alkaline glutaraldehyde resulted in rapid inactivation of both viral agents.

Aldehydes↗
PubMed1970

Evaluation of the Edgegard laminar flow hood.

In a horizontal back-to-front flow high-efficiency particulate air-filtered laminar hood, it is shown that a Blake bottle obstruction to the air flow causes a downstream cone of turbulent air which can draw microbial contamination into the work area of the hood. In controlled experiments, contamination with T3 coliphage was reduced by a series of perforations around the open edge of the hood which eliminates the cone of turbulent air. The average reduction in phage counts was 90.75, 86.79, 91.12, and 98.92%, depending upon the site of nebulization. The phage counts were reduced in 48 of the 51 tests.

Air Microbiology↗
PubMed1971

Monitoring of low-level virus in natural waters.

The insoluble polyelectrolyte technique for concentrating virus is extended to extremely low virus levels. The effectiveness of this method employing a coliphage T2 model is a constant 20% over a range of virus levels from 10(3) to 10(-4) plaque-forming units/ml. The efficiency of the method is dependent upon pH control during the concentration phase. Although the study was initiated to develop a method for quantitating the effectiveness of water and wastewater treatment methods for the removal of viruses from waters at low concentrations, the potential of the technique for efficient monitoring of natural waters is apparent.

Centrifugation, Density Gradient↗
PubMed1974

Inactivation of bacteriophage T3 in aerosols: effect of prehumidification on survival after spraying from solutions of salt, peptone, and saliva.

Coliphage T(3) was inactivated by a factor of 10(3) to 10(4) within 30 min after spraying from solutions of NaCl. Addition of peptone to the spray medium protected against inactivation at high relative humidity (RH), presumably by preventing surface inactivation. Prehumidification of the sample before collection had no effect on recovery if sprayed from solutions of NaCl, with or without peptone. If only peptone was present in the spray medium, prehumidification of the aerosol sample increased the recovery by a factor of 1,000 at low RH and by a factor of 5 at high RH. In aerosols sprayed from saliva, inactivation was nearly equal to that in peptone, with an increase of recovery after prehumidification by a factor of 1,000.

Aerosol Propellants↗
PubMed1975

Biohazards assessment in large-scale zonal centrifugation.

A study was conducted to determine the biohazards associated with use of the large-scale zonal centrifuge for purification of moderate risk oncogenic viruses. To safely and conveniently assess the hazard, coliphage T3 was substituted for the virus in a typical processing procedure performed in a National Cancer Institute contract laboratory. Risk of personnel exposure was found to be minimal during optimal operation but definite potential for virus release from a number of centrifuge components during mechanical malfunction was shown by assay of surface, liquid, and air samples collected during the processing. High concentration of phage was detected in the turbine air exhaust and the seal coolant system when faulty seals were employed. The simulant virus was also found on both the centrifuge chamber interior and rotor surfaces.

Air Microbiology↗
PubMed1972

Naturally occurring R factor, derepressed for pilus synthesis, belonging to the same compatibility group as the sex factor F of Escherichia coli K-12.

A naturally occurring R factor with constitutive pilus synthesis is described which resembles the sex factor F in compatibility and in restricting coliphage T7. Unlike F, it is not cured during growth with acridine orange. Results suggest that the R factor produces repressor of pilus synthesis, to which the operator is insensitive (i(+)o(c)). In this respect it differs from both the F factor (i(-)o(+)) and wild-type F-like R factors (i(+)o(+)).

Acridines↗
PubMed1973

Comparison of the activities of extracts of Escherichia coli and Salmonella typhimurium in amino acid incorporation.

We have compared the amino acid incorporating activities of extracts of Escherichia coli and Salmonella typhimurium in in vitro protein-synthesizing systems directed by bacterial messenger ribonucleic acid (mRNA) of both species and by the genomes of coliphages Qbeta and f2. E. coli and S. typhimurium extracts translate both homologous and heterologous bacterial mRNAs at comparable rates. S. typhimurium extracts translate phage RNAs only 10 to 15% as fast as E. coli extracts do. The presence of glucose in the growth medium increases the activity of S. typhimurium extracts three- to fourfold in the phage RNA-directed systems. Glucose has a much more limited effect on the activities of E. coli extracts. We show that similar amounts of phage RNA-ribosome complexes are formed in both the E. coli and the S. typhimurium systems, indicating that the different activities observed may be attributed to different rates of peptide elongation or to the formation of complexes at different sites on the RNA strand.

Amino Acids↗
PubMed1974

Direct selection for P1-sensitive mutants of enteric bacteria.

A method has been developed to isolate mutants sensitive to coliphage P1 from bacterial genera normally not sensitive to this phage. P1clr100KM was used. This phage is heat inducible and confers kanamycin resistance when present as a prophage (in lysogens). P1-sensitive mutants of Klebsiella, Enterobacter, Citrobacter, and Erwinia have been found. This technique provides a well-known genetic system for the study of many bacterial genera that previously had either no such system or only a marginally useful means of genetic manipulation. It also extends the range of possible intergeneric hybrids that may be constructed and studied.

Bacteriological Techniques↗