Differential persistence of F-specific RNA phage subgroups hinders their use as single tracers for faecal source tracking in surface water.

The four subgroups of F-specific RNA bacteriophages (I-IV) have been proposed as potential tracers for faecal source tracking. Groups II and III predominate in human sources while groups I and IV are most abundant in animal sources. The four subgroups of naturally occurring F-specific RNA bacteriophages were identified in different samples by plaque hybridization with genotype-specific probes and the persistence of each subgroup was evaluated.

A method to maintain mammalian cells for days alive at 4 degrees C.

This paper describes a method for the temporary storage of cultured cells. Cells from recently completed cell monolayers were trypsinized and then centrifuged. After centrifugation, the supernatant and pellet were kept at 4 degrees C for one week.

Evaluation of Escherichia coli host strain CB390 for simultaneous detection of somatic and F-specific coliphages.

Escherichia coli WG5, the strain recommended by the International Organization for Standardization (ISO) to detect somatic coliphages, was transformed to F(+) by introducing the plasmid Famp, which rendered it capable of simultaneously detecting both somatic and F-specific coliphages. Indeed, this strain, CB390, proved as effective in detecting similar numbers of phages as the sum of somatic and F-specific bacteriophages detected by the host strains recommended by both the ISO and the U.S.

A membrane-based quantitative carrier test to assess the virucidal activity of disinfectants and persistence of viruses on porous fomites.

A membrane-based quantitative carrier test method to assess the virucidal activity of disinfectants and the persistence of viruses on fomites under different environmental conditions is described. The method is based on the inactivation of the virus adsorbed to cellulose ester membranes followed by the direct enumeration of the viruses surviving the treatment without the need of an elution step. The method was suitable for four different human enteroviruses tested.

Enteroviruses and bacteriophages in bathing waters.

A new procedure for detecting and counting enteroviruses based on the VIRADEN method applied to 10 liters of seawater was examined. It improved the efficiency of detection by taking into account both the number of positive isolations and numbers found with traditional methods. It was then used to quantify viruses in bathing waters.

Double-layer plaque assay for quantification of enteroviruses.

We describe here a double-layer plaque assay for the quantification of enteroviruses, combining a monolayer plaque assay and a suspended-cell plaque assay. The double-layer assay provides significantly greater counts than other methods of virus quantification of both suspensions of pure culture viruses and naturally occurring viruses. The counts obtained by this method are approximately one order of magnitude greater than those obtained with the more commonly used method, the monolayer plaque assay.

Bacterial host strains that support replication of somatic coliphages.

Somatic coliphages detected by Escherichia coli strain WG5 have been proposed as potential indicators of water quality. Their potential replication in the water environment is considered a drawback for their use as indicators. However, the contribution of replication outside the gut to the total numbers has never been quantified.

Survival of bacterial indicator species and bacteriophages after thermal treatment of sludge and sewage.

The inactivation of naturally occurring bacterial indicators and bacteriophages by thermal treatment of a dewatered sludge and raw sewage was studied. The sludge was heated at 80 degrees C, and the sewage was heated at 60 degrees C. In both cases phages were significantly more resistant to thermal inactivation than bacterial indicators, with the exception of spores of sulfite-reducing clostridia.

Counting cytopathogenic virus adsorbed to cellulose nitrate membrane filters as a simple method for counting viruses in raw sewage and sewage effluents.

Using the VIRMETADEN (acronym derived from virus adsorption enumeration) method to count cytopathogenic viruses adsorbed to cellulose nitrate membrane filters from prefiltered and decontaminated sewage samples was shown to be feasible. The numbers of naturally occurring enteroviruses recovered by the VIRMETADEN method were significantly higher than those obtained by standard plaque assay. For prefiltration of sewage samples, low protein binding polyvinylidene fluoride (PVDF) membranes of 0.