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L Schwartzbrod

Publications and source records attributed to L Schwartzbrod.

At least 37 records · Page 2Linked to original sources
PubMed1996

Comparison study on three protocols used to concentrate poliovirus type 1 from drinking water.

The efficiency of three techniques used to concentrate enteric viruses from water media and based on adsorption-elution on glass are tested. The techniques are adsorption on glass wool (GW) at the natural pH of the water and adsorption on glass powder using acidified water (pH 3.5). In the second case, two devices are used the classical apparatus (CGP) and the modified apparatus (MGP). A solution of glycine 0.05 M--3% beef extract pH 9.5 is used in all three techniques to perform the elution. The sensitivity of the above concentration methods is assayed with samples of 20 liters of tap water artificially contaminated with a known quantity of poliovirus type 1 (10(1) to 10(7) MPNCU [20 L]-1). The resulting concentrates are inoculated to BGM cell cultures and tittered according to the MPN technique. The study demonstrated that the recovery rate increased with the viral concentration of the samples with maximum efficiency reaching 81% for GW, 89% for CGP and 99% for MGP. A Wilcoxon test performed on paired samples and on the overall results with all three methods. Significant differences were demonstrated leading to the ranking of the techniques in the growing order of sensitivity GW, CGP and MGP. These finding were confirmed using a fitting technique according to the algorithm of Marquardt.

Algorithms↗
PubMed1996

Effect of heat on the survival of infectious coxsackievirus B3 and its genome in water.

The aim of this study was to estimate the resistance of the viral genome of coxsackie B3 to heat (from 25 degrees C to 95 degrees C) with respect to the infectious virus. The results show that viral genomes were much more resistant to heat than infectious virus. The infectious coxsackie B3 was undetectable following incubation at 55 degrees C for 15 min., while the viral genome was still detected after incubation at 95 degrees C for 15 min. The viral genome became undetectable by RT semi-nested PCR after incubation at 95 degrees C for 30 min. We suggest that the rapid loss of infectious ability of the virus after incubation at 55 degrees C may be mostly due to cleavage or conformation changes in the viral capsid without significant destruction of the genome.

Cell Line↗
PubMed1995

Direct sequencing of hepatitis A virus strains isolated during an epidemic in France.

Direct sequencing of PCR products was used to study the VP1 region of the hepatitis A virus (HAV) genome (position 2199 to 2356) of nine strains isolated from human stools collected during a hepatitis A epidemic (western France, 1992), three strains from environmental samples (1990, 1991, and 1992), and two HAV cell culture isolates (the French strain CF53/Lyon and strain CLF). These viruses differed from CF53/Lyon (genotype I) by between 1 and 10.3%, and results indicated the existence of two groups of strains belonging to two different subgenotypes (IA and IB). With this sequencing technique it was possible to monitor the epidemiology of HAV and study its relations.

Adolescent↗
PubMed1995

Rotavirus quantification: a comparison between the enumerative and the MPN techniques.

A commonly used technique to isolate rotaviruses from a water environment involves the inoculation on cell culture associated with the revelation of the viral multiplication by indirect immunofluorescence. The results of the experiment using this methodology may be expressed either with an enumerative technique or with a MPN technique. We have found that the enumerative method provided the highest yield as opposed to the MPN method by a ratio close to 3.7. According to the experimental conditions that were used, the enumerative method should be favored for the detection of viruses from a medium with low viral density or when quantifying viruses from a given sample. This work involves a comparative study where the MPN method is very attractive because of the ease of implementation and the rapidity with which results may be obtained.

Analysis of Variance↗
PubMed1993

Virucidal activity of an activated sludge supernatant.

The virucidal activity of the activated sludge aqueous phase was studied from the time of initial inoculation with a poliovirus type 1 suspension and for durations of three and nine days. The mixtures were incubated in presence of a nutritive medium at 26 degrees C and samples were drawn at regular intervals of time for viral titration. The activated sludge supernatant (ASS) caused an important decrease of the titer of the poliovirus type 1 suspension especially after nine days of incubation. There was an average reduction of the viral titer of 79% after three days and 97% after nine days. When incubating the ASS with a nutritive medium before inoculating it, the viral decrease was much greater than when incubating without nutritive medium. When sterilizing the ASS before incubation and then inoculating it, no significant virucidal activity was observed (0% to 6%). Furthermore, when the ASS was subjected to a sterilization by filtration after incubation and was then inoculated, there existed a lower but not negligible viral inactivation (53% to 64%). The virucidal activity potentiality of the ASS is therefore due to microorganisms acting both directly as a support for viral particles adsorption and indirectly via the synthesis of substances with virucidal activity. When freezing and thawing the incubated ASS, and then sterilizing it by filtration before inoculation, the viral decrease reached 87% to 94%. This proves that the virucidal substances are only partly excreted by the microorganisms.

Antiviral Agents↗
PubMed1991

Influence of sewage discharge on the pollution of an estuary (Morlaix, France).

The purpose of this paper is to evaluate the pollution introduced into the Morlaix estuary by the city discharge of sewage and to determine its consequences on the microbiological quality of estuarine water and sediment. It has been shown that between 10(13) and 10(14) fecal coliforms and streptococci and between 10(6) and 10(7) enteroviruses are thus conveyed per day. The study of the downstream contamination indicates that the bacterial and viral density is much more significant in the sediment and that the bacterial concentration decreases gradually from upstream to downstream whereas the viral density only varies slightly in the water and shows very irregular fluctuation in the sediment.

Bacteria↗
PubMed1989

Recovery of solid-associated virus: evaluation of different procedures.

Three different extraction-concentration methods for virological analysis of sludge, marine and river sediments are studied. Enterovirus present in the concentrates were enumerated using the plaque technique with BGM cells. The results show that the indirect extraction technique isolated virus from the largest number of marine sediment samples. The direct extraction method is the best to recover virus from river sediments. Among the sludge samples, the number of positive samples did not vary much with the different techniques. It appears that there is no one universal method for virus concentration applicable to all categories of sediments and sludge.

Enterovirus↗
PubMed1988

Improved method for contamination of mussels by poliovirus.

An experimental method for contaminating mussels with poliovirus that approaches natural conditions in a coastal zone is described. A 280 liter aquarium is used to determine optimum conditions for obtaining a maximum titer of virus in mussels. When mussels were kept for 1 h in water contaminated with from 3 to 368 PFU ml-1, between 1 to 628 PFU g-1 tissue were recovered. Mussels exposed to contaminated water for periods of up to 10 days showed decreased titers of virus which seemed to parallel the natural inactivation of viruses in water with time. 1 h of exposure to contaminated water was always sufficient for a maximum adsorption of viral particles by mussels.

Animals↗
PubMed1986

The effect of a mass poliomyelitis vaccination program on the occurrence of enteroviruses in seawater.

A mass poliomyelitis immunization program undertaken in a coastal city correlated with a significant increase in the levels of vaccinal-type strains of poliovirus recovered in the surrounding seawater. These vaccinal strains were detected together with other wild strains regularly isolated that did not exceed the levels usually detected. The need for a serious monitoring of uncontrolled sewage discharges into the sea is discussed.

Humans↗
PubMed1985

Recovery of reoviruses from tap water.

Samples of piped water were taken from the source of the springs in ten villages in Lorraine. Usually this water has not been subjected to disinfection. The water was tested for fecal indicator bacteria, phages and animal viruses. Of the ten samples examined, seven contained no fecal indicator bacteria, phages or animal viruses, in three samples, however, Reovirus type 2 was found. Among the three positive samples only one contained fecal bacteria and phages. Consequently, the two other samples could be regarded as drinking water, despite the presence of viruses. Such an approach poses the problem of testing drinking water for viruses and suggests that viral tests should be undertaken as part of the water quality control.

Animals↗
PubMed1982

Viral pollution of seawater at Barcelona.

A virological study of sea water was carried out at Barcelona (Spain) in June and September 1979. Three beaches were sampled in June; the September samples were taken in front of an outlet at 2, 5, 20 and 1,000 m offshore. All of the samples from the 3 beaches contained viruses, at rates varying from 0.12 to 1.72 MPNCU/l. Vaccinal poliovirus type 3 and coxsackie B5 predominated. For the offshore samples, 55% were positive with rates ranging from 0.15 to 0.36 MPNCU/l. Vaccinal poliovirus type 3 was clearly predominant. There was no significant difference in viral pollution rates between 2m and 1,000 m offshore.

Enterovirus B, Human↗
PubMed1981

Improved method for virological analysis of food.

A single, simple method for recovering enteroviruses from several different kinds of food, such as ground beef, fish, oysters, and mussels, has been improved. First, sample contamination technique was studied. It appears that virus adsorption occurs at food pH and varies according to the kind of food and the food-virus exchange surface. Second, virus recovery was evaluated. According to the experimental results obtained, we propose the following method. Samples are submerged in 100 ml of demineralized water adjusted to pH 9 with a conductivity of 8,000 mg of NaCl per liter. Then, viruses are concentrated by ultrafiltration or by ultracentrifugation. This method was efficient for virus recovery from the four kinds of food, even in cases of very low contamination.

Animals↗
PubMed1977

[Correlation between the intensity of spontaneous bacteriolysis and bacterial pollution in superficial waters].

A study on the determination of the intensity of spontaneous bacteriolysis in different samples of water from the hydrographic basin of Lorraine, has led us to propose a new way of expressing the spontaneous bacteriolytic power: PBSG. Its utilization has permitted us to establish correlations between the intensity of spontaneous bacteriolytic power and the degree of bacteriological pollution found in different places in the two rivers, the Moselle and the Meurthe. A very strong correlation has been shown between the rate of global spontaneous bacteriolysis after 6 days and the number of coliforms in the water.

Bacteriolysis↗
PubMed1977

[Attempt to express the spontaneous global bacteriolytic power of water].

The utilization of a technique for the determination of spontaneous bacteriolytic power in surface waters has led us to propose a new way of expressing the spontaneous bacteriolytic power of water: PBSG. PBSG allows us to evaluate the intensity of global spontaneous bacteriolysis and to compare the global spontaneous bacteriolytic powers of different water samples.

Bacteriolysis↗