Antiviral activity of copper contact surfaces against MS2 coliphage and hepatitis a virus.

AIMS: Viral diseases can be indirectly transmitted by contaminated non-food contact surfaces to final food products by cross-contamination. The interaction of metal surfaces and viruses, MS2 coliphage and hepatitis A virus (HAV), was investigated for strategy development in decreasing this transmission risk. METHODS AND RESULTS: MS2 deposited onto stainless-steel surface was stable but inactivated at 0.95 log10 PFU min-1 on 99.9% copper surfaces. Greater copper-inactivation of MS2 was observed in (a) simple media (phosphate buffered saline, PBS) than protein-rich media (beef extract buffer), and (b) acidic than pH ≥ 6.8 environments. Among food matrices (strawberry juices and beef broth), the greatest MS2 inactivation by copper occurred in filtered strawberry juice at pH 3.5. At a reduction of 0.17 log10 PFU min-1, HAV survived longer than MS2 on copper by FRhK-4 cell infectivity assay. CONCLUSIONS: The inactivation of virus on copper surfaces was greater in acidic viral surrounding environments and in simple PBS medium. In the same 99% PBS medium, MS2 may not be an appropriate surrogate for HAV when assessing viral inactivation on copper surfaces.

Genome-regulated Assembly of a ssRNA Virus May Also Prepare It for Infection.

Many single-stranded, positive-sense RNA viruses regulate assembly of their infectious virions by forming multiple, cognate coat protein (CP)-genome contacts at sites termed Packaging Signals (PSs). We have determined the secondary structures of the bacteriophage MS2 ssRNA genome (gRNA) frozen in defined states using constraints from X-ray synchrotron footprinting (XRF). Comparison of the footprints from phage and transcript confirms the presence of multiple PSs in contact with CP dimers in the former. This is also true for a virus-like particle (VLP) assembled around the gRNA in vitro in the absence of the single-copy Maturation Protein (MP) found in phage. Since PS folds are present at many sites across gRNA transcripts, it appears that this genome has evolved to facilitate this mechanism of assembly regulation. There are striking differences between the gRNA-CP contacts seen in phage and the VLP, suggesting that the latter are inappropriate surrogates for aspects of phage structure/function. Roughly 50% of potential PS sites in the gRNA are not in contact with the protein shell of phage. However, many of these sit adjacent to, albeit not in contact with, PS-binding sites on CP dimers. We hypothesize that these act as PSs transiently during assembly but subsequently dissociate. Combining the XRF data with PS locations from an asymmetric cryo-EM reconstruction suggests that the genome positions of such dissociations are non-random and may facilitate infection. The loss of many PS-CP interactions towards the 3' end of the gRNA would allow this part of the genome to transit more easily through the narrow basal body of the pilus extruding machinery. This is the known first step in phage infection. In addition, each PS-CP dissociation event leaves the protein partner trapped in a non-lowest free-energy conformation. This destabilizes the protein shell which must disassemble during infection, further facilitating this stage of the life-cycle.

Transfer of MS2 bacteriophage from surfaces to raspberry and pitanga fruits and virus survival in response to sanitization, frozen storage and preservation technologies.

This study assessed the norovirus (NoV) surrogate bacteriophage MS2 transfer from stainless steel, glass and low-density polypropylene surfaces to raspberry and pitanga fruits. The effect of sodium hypochlorite (100 ppm, 1 min) on MS2 survival on whole fruits, the MS2 survival in sanitized fruits and derived pulps during frozen storage, and in response to preservation technologies (heat, organic acids and salts) was also assessed. The highest (p < 0.05) viral transfer (%) was observed from glass and stainless steel (∼90%) to raspberry, and from glass and polypropylene (∼75%) to pitanga, after 60 min of contact. Sodium hypochlorite reduced (p < 0.05) MS2 titer by 3.5 and 3.8 log PFU/g in raspberry and pitanga, respectively. MS2 decreased (p < 0.05) up to 1.4 log PFU/g in frozen stored sanitized fruits (whole fruits and pulps) after 15 days, with no further changes after 30 days. Thermal treatments reduced MS2 titer (p < 0.05) in both fruit pulps. MS2 inactivation was higher in pitanga pulp. The addition of ascorbic acid, citric acid, sodium benzoate, or sodium metabisulfite had little effect (<1 log PFU/g) on MS2 concentration in either fruit. These results may inform NoV risk management practice in processing and handling of fruits.

Optimizing the synthesis and purification of MS2 virus like particles.

Introducing bacteriophage MS2 virus-like particles (VLPs) as gene and drug delivery tools increases the demand for optimizing their production and purification procedure. PEG precipitation method is used efficiently to purify VLPs, while the effects of pH and different electrolytes on the stability, size, and homogeneity of purified MS2 VLPs, and the encapsulated RNA sequences remained to be elucidated. In this regard, a vector, capable of producing VLP with an shRNA packed inside was prepared. The resulting VLPs in different buffers/solutions were assessed for their size, polydispersity index, and ability to protect the enclosed shRNA. We report that among Tris, HEPES, and PBS, with or without NaNO3, and also NaNO3 alone in different pH and ionic concentrations, the 100 mM NaNO3-Tris buffer with pH:8 can be used as a new and optimal MS2 VLP production buffer, capable of inhibiting the VLPs aggregation. These VLPs show a size range of 27-30 nm and suitable homogeneity with minimum 12-month stability at 4 °C. Moreover, the resulting MS2 VLPs were highly efficient and stable for at least 48 h in conditions similar to in vivo. These features of MS2 VLPs produced in the newly introduced buffer make them an appropriate candidate for therapeutic agents' delivery.

Transfer Rate of Enveloped and Nonenveloped Viruses between Fingerpads and Surfaces.

Fomites can represent a reservoir for pathogens, which may be subsequently transferred from surfaces to skin. In this study, we aim to understand how different factors (including virus type, surface type, time since last hand wash, and direction of transfer) affect virus transfer rates, defined as the fraction of virus transferred, between fingerpads and fomites. To determine this, 360 transfer events were performed with 20 volunteers using Phi6 (a surrogate for enveloped viruses), MS2 (a surrogate for nonenveloped viruses), and three clean surfaces (stainless steel, painted wood, and plastic). Considering all transfer events (all surfaces and both transfer directions combined), the mean transfer rates of Phi6 and MS2 were 0.17 and 0.26, respectively. Transfer of MS2 was significantly higher than that of Phi6 (P < 0.05). Surface type was a significant factor that affected the transfer rate of Phi6: Phi6 is more easily transferred to and from stainless steel and plastic than to and from painted wood. Direction of transfer was a significant factor affecting MS2 transfer rates: MS2 is more easily transferred from surfaces to fingerpads than from fingerpads to surfaces. Data from these virus transfer events, and subsequent transfer rate distributions, provide information that can be used to refine quantitative microbial risk assessments. This study provides a large-scale data set of transfer events with a surrogate for enveloped viruses, which extends the reach of the study to the role of fomites in the transmission of human enveloped viruses like influenza and SARS-CoV-2. IMPORTANCE This study created a large-scale data set for the transfer of enveloped viruses between skin and surfaces. The data set produced by this study provides information on modeling the distribution of enveloped and nonenveloped virus transfer rates, which can aid in the implementation of risk assessment models in the future. Additionally, enveloped and nonenveloped viruses were applied to experimental surfaces in an equivalent matrix to avoid matrix effects, so results between different viral species can be directly compared without confounding effects of different matrices. Our results indicating how virus type, surface type, time since last hand wash, and direction of transfer affect virus transfer rates can be used in decision-making processes to lower the risk of viral infection from transmission through fomites.

Electron Beam Susceptibility of Enteric Viruses and Surrogate Organisms on Fruit, Seed and Spice Matrices.

The objective of this study was to use high-energy electron beam (HEEB) treatments to find surrogate microorganisms for enteric viruses and to use the selected surrogates as proof of concept to investigate low-energy electron beam (LEEB) treatments for enteric virus inactivation at industrial scale on frozen blueberries. Six food matrices inoculated with HAV (hepatitis A virus), MNV S99 (murine norovirus), bacteriophages MS2 and Qß, and Geobacillus stearothermophilus spores were treated with HEEB at 10 MeV using 4, 8 and 16 kGy doses. G. stearothermophilus spores showed the highest inactivation on all matrices except on raisins, with a dose-dependent effect. HAV reached the maximum measurable log10 reduction (> 3.2 log10) when treated at 16 kGy on raisins. MNV showed the highest resistance of all tested microorganisms, independent of the dose, except on frozen blueberries. On frozen blueberries, freeze-dried raspberries, sesame seeds and black peppercorns, HAV showed a mean inactivation level in between those of MS2 and G. stearothermophilus. Based on this, we selected both surrogate organisms as first approximation to estimate HAV inactivation on frozen blueberries during LEEB treatment at 250 keV using 16 kGy. Reductions of 3.1 and 1.3 log10 were measured for G. stearothermophilus spores and MS2, respectively, suggesting that a minimum reduction of 1.4 log10 can be expected for HAV under the same conditions.

Survival of MS2 and Φ6 viruses in droplets as a function of relative humidity, pH, and salt, protein, and surfactant concentrations.

The survival of viruses in droplets is known to depend on droplets' chemical composition, which may vary in respiratory fluid between individuals and over the course of disease. This relationship is also important for understanding the persistence of viruses in droplets generated from wastewater, freshwater, and seawater. We investigated the effects of salt (0, 1, and 35 g/L), protein (0, 100, and 1000 µg/mL), surfactant (0, 1, and 10 µg/mL), and droplet pH (4.0, 7.0, and 10.0) on the viability of viruses in 1-µL droplets pipetted onto polystyrene surfaces and exposed to 20%, 50%, and 80% relative humidity (RH) using a culture-based approach. Results showed that viability of MS2, a non-enveloped virus, was generally higher than that of Φ6, an enveloped virus, in droplets after 1 hour. The chemical composition of droplets greatly influenced virus viability. Specifically, the survival of MS2 was similar in droplets at different pH values, but the viability of Φ6 was significantly reduced in acidic and basic droplets compared to neutral ones. The presence of bovine serum albumin protected both MS2 and Φ6 from inactivation in droplets. The effects of sodium chloride and the surfactant sodium dodecyl sulfate varied by virus type and RH. Meanwhile, RH affected the viability of viruses as shown previously: viability was lowest at intermediate to high RH. The results demonstrate that the viability of viruses is determined by the chemical composition of carrier droplets, especially pH and protein content, and environmental factors. These findings emphasize the importance of understanding the chemical composition of carrier droplets in order to predict the persistence of viruses contained in them.

ssRNA phage penetration triggers detachment of the F-pilus.

Although the F-specific ssRNA phage MS2 has long had paradigm status, little is known about penetration of the genomic RNA (gRNA) into the cell. The phage initially binds to the F-pilus using its maturation protein (Mat), and then the Mat-bound gRNA is released from the viral capsid and somehow crosses the bacterial envelope into the cytoplasm. To address the mechanics of this process, we fluorescently labeled the ssRNA phage MS2 to track F-pilus dynamics during infection. We discovered that ssRNA phage infection triggers the release of F-pili from host cells, and that higher multiplicity of infection (MOI) correlates with detachment of longer F-pili. We also report that entry of gRNA into the host cytoplasm requires the F-plasmid-encoded coupling protein, TraD, which is located at the cytoplasmic entrance of the F-encoded type IV secretion system (T4SS). However, TraD is not essential for pilus detachment, indicating that detachment is triggered by an early step of MS2 engagement with the F-pilus or T4SS. We propose a multistep model in which the ssRNA phage binds to the F-pilus and through pilus retraction engages with the distal end of the T4SS channel at the cell surface. Continued pilus retraction pulls the Mat-gRNA complex out of the virion into the T4SS channel, causing a torsional stress that breaks the mature F-pilus at the cell surface. We propose that phage-induced disruptions of F-pilus dynamics provides a selective advantage for infecting phages and thus may be prevalent among the phages specific for retractile pili.

Effect of polymer and glass physicochemical properties on MS2 recovery from food contact surfaces.

Viruses are transmissible via their interaction with contact surfaces of food containers or tools. This study evaluated the recoveries of MS2 coliphage, a virus surrogate, from polypropylene (PP), polyvinyl chloride (PVC), polyethylene (PE), and glass (borosilicate and soda lime), as influenced by the surface chemistry and topography. MS2 (5-6 logs) in PBS with 1% TSB was inoculated onto each of 9 different surfaces, 24-h cold-incubated, and recovery was quantified by infectivity. The order of MS2 recovery efficiency from smooth surfaces was PP > PE ≥ soda lime glass, which classified into 3 ANOVA groups, p = 0.05. The MS2 recovery ratios of smooth vs. rough surfaces were 1.4-1.5. Atomic force microscopy revealed 21-nm diam pinholes (<28-nm of MS2 size) in the borosilicate glass. The lowest and highest MS2 recoveries among the 9 surfaces were demonstrated by the hole-bearing borosilicate glass (34 ±â€¯8%) and smooth PP (69 ±â€¯14%) respectively. Generally greater MS2 recovery was obtained from smooth PP and PE surfaces compared to glass, but topographic alterations (pinholes or increased roughness) decreased recovery possibly by trapping the viruses.

Virus inactivation in groundwater in a postglacial lava field in arctic climate.

Outbreaks of viral gastroenteritis are often connected to contaminated drinking water. The assessment of the water quality relies on the cultivation of indicator bacteria, and little is known of the fate of viruses in groundwater, especially in arctic regions. In Iceland, the groundwater temperature is between 3 and 6°C. The aim of this study was to determine virus inactivation at low temperature in a groundwater microcosm and in a borehole in a postglacial lava field. Two phage species that are commonly used as surrogates for norovirus were used, MS2 and PhiX174. Dialysis bags were used for the samples, and a device was constructed to hold many samples at a time and protect the samples in the borehole. No significant decrease of infective PhiX174 phages in the borehole or of the MS2 phages in the microcosm was observed. A slightly significant decrease of PhiX174 in the microcosm was noticed, with one log reduction time of 476 days. On the other hand, a significant reduction in MS2 was found in the field test, where the time needed for 90% reduction was 12·5 days. The results showed that an infective virus can exist in groundwater for months or years in arctic regions and a great difference may exist between results from microcosm and field tests. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reveals that arctic regions are highly sensitive to virus contamination as an infective virus may exist in groundwater for years at low temperature. The results also show that the virus inactivation observed in field tests may differ considerably from the inactivation observed in laboratory microcosms. The results emphasize the importance of large protection zones around drinking water intakes as well as good wastewater treatment so that the likelihood of faecal contamination of groundwater is reduced.

Measurements of the self-assembly kinetics of individual viral capsids around their RNA genome.

Self-assembly is widely used by biological systems to build functional nanostructures, such as the protein capsids of RNA viruses. But because assembly is a collective phenomenon involving many weakly interacting subunits and a broad range of timescales, measurements of the assembly pathways have been elusive. We use interferometric scattering microscopy to measure the assembly kinetics of individual MS2 bacteriophage capsids around MS2 RNA. By recording how many coat proteins bind to each of many individual RNA strands, we find that assembly proceeds by nucleation followed by monotonic growth. Our measurements reveal the assembly pathways in quantitative detail and also show their failure modes. We use these results to critically examine models of the assembly process.

Influence of algal organic matter of Microcystis aeruginosa on ferrate decay and MS2 bacteriophage inactivation.

Surface water contaminated with algae and with enteric viruses is a global problem. When surface water is used as a drinking water source, it is important to know the influence of algal organic matter on the disinfection of viruses. In this work, we studied the disinfection efficacy of ferrate and the influence of algal organic matter on the disinfection. We determined the MS2 inactivation kinetics by ferrate under three pH conditions (7, 8, and 8.7). The experimental results and pH-dependent calculation suggest that H2FeO4 and HFeO4- are 1935 and 8 times as effective as FeO42- in MS2 inactivation. We also found that intracellular algal organic matter (IAOM) had a stronger effect on MS2 inactivation kinetics than extracellular algal organic matter (EAOM) suggesting that IAOM led to higher consumption of Fe(VI) compared to EAOM. At pH 8.7, while significant consumption of FeO42- by as low as 8 mg C/L of EAOM and 2 mg C/L of IAOM was detected, MS2 inactivation was negatively influenced only when 13 mg C/L of IAOM present. This study showed that it is important to control pH and to determine the concentration of algal organic matter if ferrate is used for disinfection of surface water contaminated with algae.

The use of bacteriophage MS2 for the development and application of a virucide decontamination test method for porous and heavily soiled surfaces.

AIMS: (i) To develop an analytical method for recovery and quantification of bacteriophage MS2-as a surrogate for foot-and-mouth disease virus-from complex porous surfaces, with and without the presence of laboratory-developed agricultural grime; (ii) to evaluate, with a 4-log dynamic range, the virucidal activity of common biocides for their ability to decontaminate surfaces and hence remediate facilities, following a foreign animal disease contamination incident. METHODS AND RESULTS: An analytical method was developed and optimized for MS2 recovery from simulated agricultural surfaces. The addition of Dey-Engley neutralizing broth to an extraction buffer improved MS2 viability in liquid extracts, with optimal analytical holding times determined as <8 to ≤24 h, depending on matrix. The recovery of MS2 from surface materials decreased in the order: nonporous reference material >grimed porous materials >nongrimed porous materials. In disinfectant testing, two spray applications of pAB were effective against MS2 (≥4-log reduction) on all operational-scale materials. Two per cent citric acid had limited effectiveness, with a ≥4-log reduction observed on a selected subset of grimed concrete samples. CONCLUSIONS: Decontamination efficacy test results can be affected by surface characteristics, extraction buffer composition, analytical holding time and surface-specific organism survivability. Efficacy should be evaluated using a test method that reflects the environmental characteristics of the intended application. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study demonstrate the importance of analytical method verification tests for disinfectant testing prior to application in complex environments.

Development and Evaluation of a Novel Armored RNA Technology Using Bacteriophage Qß.

Foodborne viruses are a global threat to food safety. Real-time reverse transcription polymerase chain reaction (RT-PCR) is the most commonly used method to detect viral RNA in food. Armored RNA (AR) prepared using the MS2 phage system is a successful positive control for detecting foodborne viruses and is an important quality control process when using real-time RT-PCR. In this study, we report a novel technology for preparing AR using bacteriophage Qß and compare its stability with AR prepared using the MS2 phage system for packaging norovirus detection target RNA. AR could be successfully and efficiently produced using the developed bacteriophage Qß system. Two types of AR-AR-QNoV prepared using the Qß system and AR-MNoV prepared using the MS2 system-were stored at different temperatures for different durations. After incubating at - 20 °C for 360 days, the copy numbers of AR-QNoV and AR-MNoV decreased by 8.9% and 35.9%, respectively. After incubating at 4 °C for 60 days, the copy numbers of AR-QNoV and AR-MNoV decreased by 12.0% and 38.9%, respectively. After incubating at 45 °C, the copy numbers of AR-QNoV decreased by 71.8% after 5 days, whereas those of AR-MNoV decreased by 92.9% after only 4 days. After 5 days, AR-MNoV could not be detected using real-time RT-PCR. There was a significant difference in copy numbers decrease rate between AR-QNoV and AR-MNoV at three different temperatures (P < 0.05 ). Therefore, AR prepared using the new bacteriophage Qß system is more stable than the traditional AR, making the developed strategy a good candidate for AR preparation and quality control.

Contamination of health care personnel during removal of contaminated gloves.

In simulations of contaminated glove removal, 37% of health care personnel using their typical doffing technique contaminated their skin with a fluorescent solution. The frequency of contamination was significantly lower when the technique recommended by the Centers for Disease Control and Prevention was used versus not used (8 of 34, 24% vs 29 of 66, 44%). In simulations in which only the palm of the glove was contaminated, a modified doffing technique, to minimize the risk for contact with contaminated surfaces, reduced contamination of personnel.

Phage single-gene lysis: Finding the weak spot in the bacterial cell wall.

In general, the last step in the vegetative cycle of bacterial viruses, or bacteriophages, is lysis of the host. dsDNA phages require multiple lysis proteins, including at least one enzyme that degrades the cell wall (peptidoglycan (PG)). In contrast, the lytic ssDNA and ssRNA phages have a single lysis protein that achieves cell lysis without enzymatically degrading the PG. Here, we review four "single-gene lysis" or Sgl proteins. Three of the Sgls block bacterial cell wall synthesis by binding to and inhibiting several enzymes in the PG precursor pathway. The target of the fourth Sgl, L from bacteriophage MS2, is still unknown, but we review evidence indicating that it is likely a protein involved in maintaining cell wall integrity. Although only a few phage genomes are available to date, the ssRNA Leviviridae are a rich source of novel Sgls, which may facilitate further unraveling of bacterial cell wall biosynthesis and discovery of new antibacterial agents.

Influence of water antimicrobials and storage conditions on inactivating MS2 bacteriophage on strawberries.

Foodborne illnesses caused by norovirus contaminated fresh produce remain a food safety concern worldwide. In the present study, the impacts of commercial and home processing conditions of strawberries were evaluated for inactivation of the MS2 bacteriophage. MS2 was used as a surrogate of norovirus and was spot inoculated onto strawberries to achieve 6.6 log PFU/g. The inoculated strawberries were washed with tap water, electrolyzed water, or 50 ppm chlorine for 90 s prior to and after storage. After initial washing, the strawberries were separately stored at -20 °C and -80 °C for 30 days. Change in MS2 populations on strawberries was evaluated by plaque assay method on day 1, 15, and 30 for -20 °C and -80 °C groups. The results showed that washing strawberries prior to storage resulted in a significant decrease (approximately 1 log PFU/g) of MS2 population regardless of the treatment (p < 0.05). Frozen storage had minor effects on inactivating MS2, which resulted in approximately a 0.5 log PFU/g reduction at the end of storage. Washing frozen berries in electrolyzed water or 50 ppm chlorine on day 30 resulted in an additional 1 log PFU/g decrease in MS2 compared to water alone. These results suggest that washing strawberries with a chemical antimicrobial prior to and post frozen storage may enhance microbial safety.

Live E. coli bacteria label-free sensing using a microcavity in-line Mach-Zehnder interferometer.

The paper presents the first study to date on selective label-free biosensing with a microcavity in-line Mach-Zehnder interferometer induced in an optical fiber. The sensing structures were fabricated in a single-mode fiber by femtosecond laser micromachining. In contrast to other studies of this sensing scheme, where only the sensitivity to refractive index changes in the cavity was investigated, this research used chemical surface treatment of the sensor to ensure detection specificity. Immobilized MS2 bacteriophages were applied as recognition elements specifically targeting live E. coli C3000 bacteria. It is shown that the sensor allows for real-time monitoring of biological phenomena taking place on the surface of the microcavity. The developed biosensor exhibits ultrahigh refractive index sensitivity of 15,000 nm/RIU and is capable of detecting live E. coli bacteria concentrations as low as 100 colony forming units (CFU)/mL in liquid volume as low as picoliters.

Inactivation of feline calicivirus using ultraviolet light-emitting diodes.

Ultraviolet light-emitting diodes (UV-LEDs) with peak emission wavelengths of 265, 280 and 300 nm were applied for the inactivation of feline calicivirus (FCV) in water, and the results were compared to those derived with a common viral surrogate coliphage MS2. The fluence response profiles indicated that the log10-based inactivation rate constant of FCV was 0.113, 0.101 and 0.007 cm2 mJ-1 for the 265, 280 and 300 nm UV-LEDs, respectively, while that of MS2 was 0.034, 0.033 and 0.003 cm2 mJ-1 for the 265, 280 and 300 nm UV-LEDs, respectively. Namely, FCV was about two to three times more sensitive than MS2 to germicidal UV emissions adopted in this study, and the 265 nm and 280 nm UV-LEDs were particularly effective to inactivate FCV. Results of this study are to be a part of database on fluence response profiles of various microorganisms, which would foster the development of disinfection apparatuses equipped with UV-LEDs.

The impact of chlorine and heat on the infectivity and physicochemical properties of bacteriophage MS2.

Enteric viruses and bacteriophages are exposed to various inactivating factors outside their host, and among them chlorine and heat are the most commonly used sanitizer in water industry and treatment in the food industry, respectively. Using MS2 phages as models for enteric viruses, we investigated the impact of free chlorine and heat on their physicochemical properties. Free chlorine was first evaluated alone. No increase in either capsid permeability or hydrophobicity was observed. The negative surface charge slightly increased suggesting molecular changes in the capsid. However, a weakening of the capsid by chlorine was suggested by differential scanning fluorimetry. This phenomenon was confirmed when chlorination was followed by a heat treatment. Indeed, an increase in the inactivation of MS2 phages and the permeability of their capsids to RNases was observed. More interestingly, an increase in the expression of hydrophobic domains at the phage surface was observed, but only for phages remaining infectious. The chlorine-caused weakening of the capsid suggested that, for an optimal use, the oxidant should be followed by heat. The increased permeability to RNases and the expression of hydrophobic domains may contribute to the development or improvement of molecular methods specific for infectious enteric viruses.