Biomedical subjects

L Schwartzbrod

Publications and source records attributed to L Schwartzbrod.

At least 19 recordsLinked to original sources

PubMed2004

Survival of infectious Poliovirus-1 in river water compared to the persistence of somatic coliphages, thermotolerant coliforms and Poliovirus-1 genome.

The microbiological quality of water is currently assessed by search for fecal bacteria indicators. There is, however, a body of knowledge demonstrating that bacterial indicators are less resistant to environmental factors than human pathogenic viruses and therefore underestimate the viral risk. As river water is often used as a resource for drinking water production, it is particularly important to obtain a valid estimation of the health hazard, including specific viral risk. This work was conducted to compare the survival of infectious Poliovirus-1 used as a pathogenic virus model to the persistence of, on the one hand, thermotolerant coliforms commonly used as indicators and on the other hand, to somatic coliphages and Poliovirus-1 genome considered as potential indicators. We studied the behavior of infectious Poliovirus-1 and the three (potential) indicators of viral contamination in river water at three different temperatures (4 degrees C,18 degrees C and 25 degrees C). This experiment was performed twice with river water sampled at two different periods, once in winter and once in summer. Our results showed that the survival of thermotolerant coliforms can be 1.5-fold lower than infectious Poliovirus-1. In contrast, under all our experimental conditions, somatic coliphages and Poliovirus-1 genome persisted longer than infectious Poliovirus-1, surviving, respectively, 2-6-fold and about 2-fold longer than infectious Poliovirus-1. According to our results exclusively based on survival capacity, somatic coliphages and viral genome, unlike thermotolerant coliforms appear to be better indicators of viral contamination in river water. Moreover, the disappearance of viral genome is well-correlated to that one of infectious virus irrespective of the conditions tested.

Adaptation, Physiological↗

PubMed2003

Recovery of feline calicivirus infectious particles and genome from water: comparison of two concentration techniques.

The aim of this work was to determine the recovery rate of feline calicivirus (FCV-F9) infectious particles and genome from water after a concentration step using either adsorption elution on glass wool or filtration through an electropositive membrane. The results showed that the membrane filtration technique allowed a 75% recovery rate of FCV-F9 infectious particles while the yield was only 5.3% for FCV-F9 genome. Using the glass wool adsorption-elution technique, the recovery rate of FCV-F9 infectious particles was 0.5% while the yield was 102.5% with Poliovirus 1.

Adsorption↗

PubMed2002

Fates of bacteriophages and bacterial indicators in the Moselle river (France).

It has been suggested that bacteriophages can provide useful information about the pathogenic microorganisms, particularly enteric viruses, present in water. This information is complementary to that obtained from bacterial indicators of faecal contamination, which would be of great value for evaluating the risks associated with the use of certain types of water. Before bacteriophages can be used as indicators of faecal contamination, we need to confirm that bacteriophages give a different response to that given by the well-known bacteria indicators and to determine what happens to bacteriophages in river water. Indeed, drinking water is often produced from river water, either by natural filtration through the soil or after undergoing various treatments. We collected 96 river water samples from six different sites between February and November 2000. The samples were analysed for three faecal indicator bacteria (thermotolerant coliforms, enterococci and spores of sulphite-reducing anaerobes) and three types of bacteriophages (somatic coliphages, F-specific phages and Bacteroides fragilis phages). The densities of thermotolerant coliforms and enterococci depended mainly on physical factors such as flow rate and water temperature. High temperature and low flow rate led to a decrease in the density of these microorganisms, especially in the absence of a major input of faecal pollution. Conversely, the densities of somatic coliphages, F-specific phages and spores of sulphite-reducing anaerobes remained constant regardless of the flow rate and temperature. The density of Bacteroides fragilis phages was too low for unambiguous determination of their fate in river water.

Bacteriophages↗

PubMed2002

Microbial agents associated with waterborne diseases.

Many classes of pathogens excreted in feces are able to initiate waterborne infections. There are bacterial pathogens, including enteric and aquatic bacteria, enteric viruses, and enteric protozoa, which are strongly resistant in the water environment and to most disinfectants. The infection dose of viral and protozoan agents is lower than bacteria, in the range of one to ten infectious units or oocysts. Waterborne outbreaks of bacterial origin (particularly typhoid fever) in the developing countries have declined dramatically from 1900s. Therefore, some early bacterial agents such as Shigella sonnei remains prevalent and new pathogens of fecal origin such as zoonotic C. jejuni and E. coli O157:H7 may contaminate pristine waters through wildlife or domestic animal feces. The common feature of these bacteria is the low inoculum (a few hundred cells) that may trigger disease. The emergence in early 1992 of serotype O139 of V. cholerae with epidemic potential in Southeast Asia suggests that other serotypes than V. cholerae O1 could also getting on epidemic. Some new pathogens include environmental bacteria that are capable of surviving and proliferating in water distribution systems. Other than specific hosts at risk, the general population is refractory to infection with ingested P. aeruginosa. The significance of Aeromonas spp. in drinking water to the occurrence of acute gastroenteritis remains a debatable point and has to be evaluated in further epidemiological studies. Legionella and Mycobacterium avium complex (MAC) are environmental pathogens that have found an ecologic niche in drinking and hot water supplies. Numerous studies have reported Legionnaires' disease caused by L. pneumophila occurring in residential and hospital water supplies. M. avium complex frequently causes disseminated infections in AIDS patients and drinking water has been suggested as a source of infection; in some cases the relationship has been proven. More and more numerous reports show that Helicobacter pylori DNA can be amplified from feces samples of infected patients, which strongly suggests fecal-to-oral transmission. Therefore, it is possible that H. pylori infection is waterbome, but these assumptions need to be substantiated. Giardiasis has become the most common cause of human waterborne disease in the U.S. over the last 30 years. However, as a result of the massive outbreak of waterborne cryptosporidiosis in Milwaukee, Wisconsin, affecting an estimated 403,000 persons, there is increasing interest in the epidemiology and prevention of new infection disease caused by Cryptosporidium spp. as well as monitoring water quality. The transmission of Cryptosporidium and Giardia through treated water supplies that meet water quality standards demonstrates that water treatment technologies have become inadequate, and that a negative coliform no longer guarantees that water is free from all pathogens, especially from protozoan agents. Substantial concern persists that low levels of pathogen occurrence may be responsible for the endemic transmission of enteric disease. In addition to Giardia and Cryptosporidium, some species of genera Cyclospora, Isospora, and of family Microsporidia are emerging as opportunistic pathogens and may have waterborne routes of transmission. More than 15 different groups of viruses, encompassing more than 140 distinct types can be found in the human gut. Some cause illness unrelated with the gut epithelium, such as Hepatitis A virus (HAV) and Hepatitis E virus (HEV). Numerous large outbreaks have been documented in the U.S. between 1950 and 1970, and the incidence rate has strongly declined in developing countries since the 1970s. Hepatitis E is mostly confined to tropical and subtropical areas, but recent reports indicate that it can occur at a low level in Europe. A relatively small group of viruses have been incriminated as causes of acute gastroenteritis in humans and fewer have proven to be true etiologic agents, including rotavirus, calicivirus, astrovirus, and some enteric adenovirus. These enteric viruses have infrequently been identified as the etiologic agents of waterborne disease outbreaks, because of inadequate diagnostic technology, but many outbreaks of unknown etiology currently reported are likely due to viral agents. Actually, Norwalk virus and Norwalk-like viruses are recognized as the major causes of waterborne illnesses world-wide. The global burden of infectious waterborne disease is considerable. Reported numbers highly underestimate the real incidence of waterborne diseases. The most striking concern is that enteric viruses such as caliciviruses and some protozoan agents, such as Cryptosporidium, are the best candidates to reach the highest levels of endemic transmission, because they are ubiquitous in water intended for drinking, being highly resistant to relevant environmental factors, including chemical disinfecting procedures. Other concluding concerns are the enhanced risks for the classic group of debilitated subjects (very young, old, pregnant, and immunocompromised individuals) and the basic requirement of to take specific measures aimed at reducing the risk of waterborne infection diseases in this growing, weaker population.

Animals↗

PubMed2002

Evaluation of bacteriophages during the treatment of sludge.

The aim of this work was to determine the effect of liming and composting on the fate of three bacteriophages (somatic coliphages, F-RNA phages, Bacteroides fragilis phages) considered as potential indicators of viral contamination. It was shown that the three bacteriophages studied exhibited variable densities in sludge. Somatic coliphages were most abundant (10(4) to 10(5) x 10 g(-1) DM) then F-RNA bacteriophages (10(2) to 10(4) x 10 g(-1) DM) and Bacteroides fragilis phages (10(1) to 10(2) x 10 g(-1) DM). The efficacy of liming was found to be pH dependent but also sludge dependent. The pH allowing 99% elimination of somatic coliphage is close to 9 for solid sludges and close to 13.5 for liquid sludges. For composting, our findings clearly demonstrated that phage inactivation is very clearly temperature-dependent. For temperatures reaching 70 degrees, there is a 5 log reduction in somatic coliphages while for temperature in the 50-55 degrees C range, the drop off is only 2 log. Considering the efficacy of the treatment methods, it is clear that the well-established industrial procedures that reach temperatures in the 60-70 degrees C range totally inactivate all 3 phages tested and present in sludge before composting.

Bacteriophages↗

PubMed2001

Best viral elution method available for quantification of enteroviruses in sludge by both cell culture and reverse transcription-PCR.

The aim of this study was to select one or several virus extraction techniques that enable simultaneous detection of enterovirus genomes and infectious particles in different types of urban sludge. Eight techniques were compared by using 16 different liquid and solid sludge samples. The numbers of infectious enteroviruses in cell cultures were determined by using the most-probable-number method. The enterovirus genome was quantified by a single-tube reverse transcription-PCR using TaqMan technology. The results were statistically analyzed by Friedman's test, a nonparametric test for analysis of randomized block data using only ranks in terms of extraction technique efficiency. Two techniques seemed to yield higher viral titers as determined by simultaneous detection by cell culture and PCR. The first involved a 10% beef extract solution at pH 9 and sonication; the second involved a 0.3 M NaCl-7% beef extract solution at pH 7.5 followed by Freon treatment. In solid sludge, no significant differences were observed among the eight techniques tested. Both of the best techniques can be used for simultaneous detection of infectious enterovirus particles and genomes in any type of urban sludge.

Enterovirus↗

PubMed2001

The effect of liming on the microbiological quality of urban sludge.

Treatments applied to sludge in order to stabilise and dehydrate them may give notable inactivation of microorganisms. This is observed when sludge is exposed either to high temperature or drastic pH when residual sludge is limed. The control of virological, parasitological and bacteriological sludge quality by detecting pathogenic microorganisms is slow and too expensive to be commonly practised. Thus, it is possible to replace pathogenic microorganisms detection by that of contamination indicators. The aim of this study was to determine the influence of liming on the behaviour of pathogenic microorganisms detected in urban sludge. The detection of Salmonella and helminth eggs was carried out in liquid sludge (2-3% dryness) and solid sludge (23% dryness) with added lime (0-45% weight/dry weight) and stored for 24 h-46 weeks. The results showed that liming modified some characteristics such as temperature, dryness and pH of the sludge. It appeared that, whatever the percentage of added lime, the temperature of liquid sludge did not change while it increased by about 9 degrees C when 30-45% lime was added to solid sludge. In the same way, the dryness of liquid sludge did not change during the liming, whereas the dryness of 45% limed solid sludge increased from 23% to 31%. Finally, 15%, 30% and 45% liming gave a pH of at least 10, 11.5 and 12, respectively, although the pH increase depended on the sludge type. The efficiency of liming was considered to be related to the pH and not to the percentage of added lime. Three factors determined the efficiency of pathogen elimination: (a) the pH reached by the sludge, (b) the period of liming activity and (c) the dryness of the sludge. Salmonella were eliminated from liquid sludge in 24 h at pH 10.7 and from solid sludge in 24 h at pH 10.0. Viable helminth egg concentration decreased to 3 eggs/10 g DM in liquid sludge in 14 d at pH 11.9 and 60 d at pH 11.6. In solid sludge, egg reduction was achieved in 24 h at pH 12.5, 7 d at pH 12.0 and 14 d at pH 11.5. From this study, it appeared that liming resulted in a much better microbiological quality of liquid sludge if its pH was maintained at 11.6 over 60 d or at pH 11.9 for 14 d. Solid sludge needed to be maintained at pH 11.5 for 14 d, pH 12.0 for 7 d or pH 12.5 for 24 h to achieve similar results.

Animals↗

PubMed2000

Quantification of enterovirus RNA in sludge samples using single tube real-time RT-PCR.

We have developed a quantitative RT-PCR method that can be used to determine the amount of enterovirus RNA in urban sludge samples. This method combines Taq-Man technology with the ABI Prism 7700 real-time sequence detection system. We optimized a one-step RT-PCR that uses a dual-labeled fluorogenic probe to quantify the 5' noncoding region of enteroviruses. For accurate quantification of the number of copies, a Mahoney type 1 poliovirus RNA standard was designed and produced using genetic engineering. This fragment, quantified using the Ribogreen method, was used in serial dilutions as an external standard. The method had a 7-log dynamic range (5 to 2 x 10(7)). PCR inhibitors were removed by extracting viral RNA (after virus concentration) using the RNeasy mini kit with added polyvinylpyrrolidone (PVP) and running the amplification reaction with a mixture containing PVP and T4 gene 32 protein. This real-time quantification of enterovirus RNA allows large numbers of samples to be screened. Its sensitivity, simplicity and reproducibility render it suitable as a screening method with which to characterize enteroviruses, the presence of infectious particles being subsequently confirmed by cell culture.

Enterovirus↗

PubMed1999

Comparison of seven RNA extraction methods on stool and shellfish samples prior to hepatitis A virus amplification.

When choosing an extraction method, two parameters have to be considered: recovery of the viral material and elimination or inactivation of inhibitory substances. Seven techniques for extracting hepatitis A virus (HAV) from stool and shellfish samples were compared, in order to identify the protocol most suited to both types of sample and with the best extraction yield. The protocols tested were either techniques for the recovery and purification of total RNA, such as RNAzol, PEG-CETAB, GTC-silica and Chelex, or techniques for isolating specifically HAV using a nucleotide probe or a monoclonal antibody. For stool samples, RNAzol, PEG-CETAB, and magnetic beads with antibody allowed detection of the virus in 11/12 and 12/12 of samples. For shellfish samples, three protocols allowed RNA to be extracted in 90% of cases, RNAzol, PEG-CETAB, and GTC-silica. Their rapidity and low cost make RNAzol and GTC-silica the most suitable for routine diagnostic testing. reserved.

Feces↗

PubMed1999

Comparative study of techniques used to recover viruses from residual urban sludge.

Eight virus extraction techniques were compared on three types of residual urban sludge for simultaneous detection of infectious enteroviruses, somatic coliphages, F-specific RNA bacteriophages and Bacteroides fragilis bacteriophages. The highest virus counts were found in extracts obtained using three extraction techniques described by respectively using a 10% beef extract solution at pH 9 and sonication, using a 0.3 M NaCl/7% beef extract solution at pH 7.5 and freon, and finally using a 0.1 M borate buffer/3% beef extract solution at pH 9 and sonication.

Bacteriophages↗

PubMed1999

Enterovirus genome detection in wastewater: multi centric evaluation of a commercial kit.

A multi-centric study was carried out in three laboratories, to evaluate the efficiency of a standardized kit for the detection of enterovirus genome in wastewater. Twenty one samples of 20 liters of wastewater were analyzed before and after concentration through glass wool. Each sample was analyzed with the Amplicor kit as well as with techniques developed independently in each laboratory. The results show that the Amplicor kit is well suited to the detection of enterovirus genome in treated wastewater. The results may be compared to those obtained with semi-nested RT-PCR techniques used in each laboratory. However, the Amplicor kit technique is more simple and has the advantage of providing a standardized technique useful for comparative studies. During this work it was observed that the sensitivity of the detection of infectious viruses and virus genome was improved when concentrated samples were used for analysis.

Cell Culture Techniques↗

PubMed1998

Detection of infectious enteroviruses, enterovirus genomes, somatic coliphages, and Bacteroides fragilis phages in treated wastewater.

In this study, three types of treated wastewater were tested for infectious enteroviruses, the enterovirus genome, somatic coliphages, and Bacteroides fragilis phages. The aim of this work was to determine whether the presence of the two types of bacteriophages or of the enterovirus genome was a good indicator of infectious enterovirus contamination. The enterovirus genome was detected by reverse transcription-polymerase chain reaction. Infectious enteroviruses were quantified by cell culturing (BGM cells), and the bacteriophages were quantified by plaque formation on the host bacterium (Escherichia coli or B. fragilis) in agar medium. Forty-eight samples of treated wastewater were analyzed. Sixteen samples had been subjected to a secondary treatment for 8 to 12 h (A), 16 had been subjected to a secondary treatment for 30 h (B1), and 16 had been subjected to both secondary and tertiary treatments (B2). The mean concentrations of somatic coliphages were 4.9 x 10(4) PFU . liter-1 for treatment line A, 9.8 x 10(3) PFU . liter-1 for B1, and 1.4 x 10(3) PFU . liter-1 for B2, with all the samples testing positive (100%). The mean concentrations of B. fragilis phages were 1.7 x 10(3) PFU . liter-1 for A (100% positive samples), 17 to 24 PFU . liter-1 for B1 (44% positive samples), and 0.8 to 13 PFU . liter-1 for B2 (6% positive samples). The mean concentrations of infectious enteroviruses were 4 most probable number of cytopathogenic units (MPNCU) . liter-1 for A (31% positive samples) and <1 MPNCU . liter-1 for B1 and B2 (0% positive samples). The percentages of samples testing positive for the enterovirus genome were 100% for A, 56% for B1, and 19% for B2. The percentages of samples testing positive for the enterovirus genome were significantly higher than those for infectious enteroviruses. This finding may have been due to the presence of noninfectious enteroviruses or to the presence of infectious enteroviruses that do not multiply in BGM cell cultures. However, under our experimental conditions, nondetection of the genome implies the absence of infectious viruses. There was a significant correlation between the concentration of somatic coliphages or B. fragilis phages and the presence of infectious enteroviruses or the presence of the enterovirus genome. However, the somatic coliphage concentration did not lead to fluctuations in the infectious enterovirus concentration, whereas the B. fragilis phage concentration did.

Bacteriophages↗

PubMed1998

Reverse transcriptase PCR detection of astrovirus, hepatitis A virus, and poliovirus in experimentally contaminated mussels: comparison of several extraction and concentration methods.

Four methods of extraction and three methods of concentration of three enteric viruses from mussels were comparatively evaluated by reverse transcriptase PCR (RT-PCR). Shellfish were experimentally contaminated by immersion in seawater seeded with astrovirus, hepatitis A virus, or poliovirus. Sixty-gram samples of mussel tissues were processed by using borate buffer, glycine solution, saline beef, and saline beef-Freon extraction methods. The viruses were concentrated by precipitation with polyethylene glycol 6000 (PEG 6000) or PEG 8000 or by organic flocculation. RT-PCR was performed with RNA extracts from crude shellfish extracts and concentrates with and without Sephadex LH20 filtration. The glycine solution and borate buffer extraction methods resulted in significantly more RT-PCR-positive samples than the saline beef extraction method. We assessed the efficiency of 20 combinations of extraction and concentration methods. The borate buffer-organic flocculation, borate buffer-PEG 6000, and glycine solution-PEG 6000 combinations gave RT-PCR-positive results for all 27 samples analyzed for the three viruses. Detoxification of the samples by Sephadex LH20 filtration significantly decreased the efficiency of RT-PCR virus detection.

Animals↗

PubMed1998

Potentiation of the virucidal activity of sterilized natural waters.

After heat, conductivity has been described as the second most inactivating factor of viruses in surface waters. Using poliovirus-1, we showed that a highly significant linear relationship between virus inactivation rate and water conductivity can be obtained for most of the tested sterilized water samples. Using sterile saline solutions, we demonstrated that this apparent relationship is false, i.e., virus inactivation rate is not affected by water conductivity alone. With the hypothesis that salts may serve to potentiate the antiviral activities of certain microbiological substances that are supposed to be found in the tested samples, we can explain the apparent relationship observed in this study and in similar ones. As a consequence, an effective water treatment could be responsible for the removal of both viruses and some virus-inactivating factors. Alternatively, virus-inactivating capability of a given water resource could be enhanced along with its hardness or its degree of mineralization.

Antiviral Agents↗

PubMed1998

Persistence of infectious hepatitis A virus and its genome in artificial seawater.

The stability of the hepatitis A virus (HAV) genome detectable by RT-PCR in artificial sterile seawater seeded with HAV has been compared to that of HAV detectable in cell culture. The HAV genome was detectable by RT-PCR for 232 days while virus particles were detectable in cell culture for only 35 days. This difference in stability indicates that detection of the HAV genome by RT-PCR is not a reliable indicator of the survival of HAV detectable in cell cultures. However, before these results can be extrapolated to stability in natural seawater, the effect of additional elements in the natural environment, such as bacteria, fungi and suspended matter, on the stability of the HAV genome and cell culture infectious HAV particles, will have to be examined.

Cell Line↗

PubMed1997

Use of Doehlert matrices for study of poliovirus-1 adsorption.

Experiments designed according to Doehlert matrices were carried out to study poliovirus-1 adsorption to Na-montmorillonite in a complex aqueous environment. Salt concentration and valence, virus load, clay concentration, and organic matter concentration were included in the design as selected parameters for possible or known involvement in viral adsorption in environmental waters. Use of this experimental design not only allowed to detect and quantify direct influence of the tested parameters upon the viral response, but also to reveal the influence of interactions between these tested factors. Thus, beyond the reassessment of the higher efficiency of multivalent cations on virus adsorption, as opposed to monovalent ones, detection was enabled of a tannic acid/aluminium specific interaction that seemed to be responsible for the nonavailability of these elements for interaction with viruses. Such a statistical tool allows for a gain in experimental accuracy beyond technical improvements and is particularly suited for low-cost study of multifactorial phenomena.

Adsorption↗

PubMed1997

Enterovirus genomes in wastewater: concentration on glass wool and glass powder and detection by RT-PCR.

Standard methods for detecting enteroviruses in environmental samples require cell culture, which is time consuming and expensive. The reverse transcription-polymerase chain reaction (RT-PCR) is a rapid, sensitive method for detecting enteroviruses in water. However, environmental samples often contain substances that inhibit PCR amplification of target RNA. Hence the virus must be concentrated by procedures that do not interfere with amplification. This study shows that virus concentration by adsorption onto glass powder or glass wool supports is suitable for detecting viral genomes in treated wastewater by RT semi-nested PCR. No enterovirus genome was detected directly in 25 samples of treated wastewater by RT semi-nested PCR. However, samples concentrated by adsorption onto glass wool or glass powder showed that 48% (glass powder) and 56% (glass wool) contained virus. Secondary concentration by organic flocculation was unsuitable for detecting virus concentrated on glass wool (20% positive samples), but it helped to increase the detection of the genome after concentration on glass powder (72% positive samples).

Cell Line↗

PubMed1997

Poliovirus-1 inactivation and interaction with biofilm: a pilot-scale study.

A pilot-scale study was initiated to examine the behavior of viruses pulse injected into a distribution system. The influence of a free-chlorine residual and that of virus preadsorption to clay particles was evaluated by tracing the viruses both in the water flow and after elution from the biofilm. These experiments demonstrated, first, that virus preadsorption on 40 mg of Na-montmorillonite per liter increased the residence time of the viruses within the pilot plant by roughly three times and, second, that preadsorption to clay did not prevent viruses from being inactivated by chlorine. Moreover, with no clay added, a greater amount of viruses was recovered from the biofilm than from the water flow (by a factor of 2 or 10 in the absence or presence of chlorine, respectively), indicating a tendency for virus accumulation within biofilms.

Biofilms↗