Retention of E. coli and water on the skin after liquid contact

The frequent contact people have with liquids containing pathogenic microorganisms provides opportunities for disease transmission. In this work, we quantified the transfer of bacteria-using E. coli as a model- from liquid to skin, estimated liquid retention on the skin after different contact activities (hand immersion, wet-cloth and wet-surface contact), and estimated liquid transfer following hand-to-mouth contacts. The results of our study show that the number of E. coli transferred to the skin per surface area (n [E. coli/cm2]) can be modeled using n = C (10-3.38+h), where C [E. coli/cm3] is the concentration of E. coli in the liquid, and h [cm] is the film thickness of the liquid retained on the skin. Findings from the E. coli transfer experiments reveal a significant difference between the transfer of E. coli from liquid to the skin and the previously reported transfer of viruses to the skin. Additionally, our results demonstrate that the time elapsed since the interaction significantly influences liquid retention, therefore modulating the risks associated with human interaction with contaminated liquids. The findings enhance our understanding of liquid-mediated disease transmission processes and provide quantitative estimates as inputs for microbial risk assessments

Virus inactivation in stored human urine, sludge and animal manure under typical conditions of storage or mesophilic anaerobic digestion

Viruses represent major disease transmitting agents carried by human excreta and animal manure. Understanding virus inactivation is therefore essential in preventing microbial spread due to inadequate treatment of these materials. Here, we investigated the inactivation kinetics of the single-stranded (ss) RNA phage MS2, DNA phages T4 and ΦX174, and the double-stranded DNA human adenovirus in stored human urine, sludge, and animal manure, at temperatures and pH values typical of storage under naturally occurring conditions or mesophilic anaerobic digestion (< 40 °C). The ssRNA phage MS2 was most readily inactivated in all samples compared to the other viruses tested. This is consistent with previous findings in well-controlled buffer solutions of similar composition, where inactivation was found to be governed by bases (NH3, carbonate, hydroxide) that catalyze the transesterification and cleavage of the ssRNA. Correspondingly, MS2 inactivation kinetics in real matrices could be adequately modelled by only taking into account the effects of temperature, pH, carbonate and ammonia on the integrity of ssRNA. DNA viruses were more persistent compared to MS2; however, inactivation in selected sludge and manure samples proceeded at faster rates compared to well-controlled buffer solutions of similar composition. This indicates a contribution of microbial or enzymatic activity to inactivation of DNA viruses. Overall, this study identifies the most important factors contributing to inactivation of viruses in human excreta and manure, and highlights the differences in inactivation kinetics and mechanisms between ssRNA and DNA viruses

Removal of Waterborne Viruses by Tetrahymena pyriformis Is Virus-Specific and Coincides with Changes in Protist Swimming Speed

Biological treatment of waterborne viruses, specifically grazing of viruses by protists, can enhance microbial water quality while avoiding the production of toxic byproducts and high energy costs. However, tangible applications are limited by the lack of understanding of the underlying mechanisms. Here, we examined the feeding behavior of Tetrahymena pyriformis ciliates on 13 viruses, including bacteriophages, enteric viruses, and respiratory viruses. Significant differences in virus removal by T. pyriformis were observed, ranging from no removal (Qbeta, coxsackievirus B5) to ≥2.7 log10 (JC polyomavirus) after 48 h of co-incubation of the protist with the virus. Removal rates were conserved even when protists were co-incubated with multiple viruses simultaneously. Video analysis revealed that the extent of virus removal was correlated with an increase in the protists' swimming speed, a behavioral trait consistent with the protists' response to the availability of food. Protistan feeding may be driven by a virus' hydrophobicity but was independent of virus size or the presence of a lipid envelope. Keywords: biological water treatment; enveloped virus; grazing; protists; swimming speed; waterborne virus

Removal of Waterborne Viruses by Tetrahymena pyriformis Is Virus-Specific and Coincides with Changes in Protist Swimming Speed

Biological treatment of waterborne viruses, specifically grazing of viruses by protists, can enhance microbial water quality while avoiding the production of toxic byproducts and high energy costs. However, tangible applications are limited by the lack of understanding of the underlying mechanisms. Here, we examined the feeding behavior of Tetrahymena pyriformis ciliates on 13 viruses, including bacteriophages, enteric viruses, and respiratory viruses. Significant differences in virus removal by T. pyriformis were observed, ranging from no removal (Qbeta, coxsackievirus B5) to ≥2.7 log10 (JC polyomavirus) after 48 h of co-incubation of the protist with the virus. Removal rates were conserved even when protists were co-incubated with multiple viruses simultaneously. Video analysis revealed that the extent of virus removal was correlated with an increase in the protists' swimming speed, a behavioral trait consistent with the protists' response to the availability of food. Protistan feeding may be driven by a virus' hydrophobicity but was independent of virus size or the presence of a lipid envelope.</p

Photoinactivation of virus on iron-oxide coated sand: enhancing inactivation in sunlit waters

Adsorption onto iron oxides can enhance the removal of waterborne viruses in constructed wetlands and soils. If reversible adsorption is not coupled with inactivation, however, infective viruses may be released when changes in solution conditions cause desorption. The goals of this study were to investigate the release of infective bacteriophages MS2 and Phi X174 (two human viral indicators) after adsorption onto an iron oxide coated sand (IOCS), and to promote viral inactivation by exploiting the photoreactive properties of the IOCS. The iron oxide coating greatly enhanced viral adsorption (adsorption densities up to similar to 10(9) infective viruses/g IOCS) onto the sand, but had no affect on infectivity. Viruses that were adsorbed onto IOCS under control conditions (pH 7.5, 10 mM Tris, 1250 mu S/cm) were released into solution in an infective state with increases in pH and humic acid concentrations. The exposure of IOCS-adsorbed MS2 to sunlight irradiation caused significant inactivation via a photocatalytic mechanism in both buffered solutions and in wastewater samples (4.9 log(10) and 3.3 log(10) inactivation after 24-h exposure, respectively). Unlike MS2, Phi X174 inactivation was not enhanced by photocatalysis. In summary, IOCS enhanced the separation of viruses from the water column, and additionally provided a photocatalytic mechanism to promote inactivation of one of the surrogates studied. These qualities make it an attractive option for improving viral control strategies in constructed wetlands. (C) 2012 Elsevier Ltd. All rights reserved

Chemical disinfectants

Safe water, sanitation, and hygiene provision and promotion are critical elements of emergency response to ensure human safety, health, and dignity. Disinfectants, such as chlorine, are widely used in emergency response to treat water for drinking. However, excreta is rarely treated in emergencies; the current focus of response activities is to provide safe, clean, and private sanitation facilities. In this chapter, we provide a summary of knowledge on disinfection of excreta in emergencies and recommendations for future research. In particular, we recommend the need to prioritize disinfection of waste in emergencies to prevent ongoing transmission of disease and to work with responders and beneficiaries to develop appropriate, low-cost, transportable, acceptable, and easy-to-use excreta disinfection solutions. Chemical disinfectants inactivate pathogens by chemically degrading their building blocks or disrupting their metabolism. The efficacy of chemical disinfectants thus depends strongly on their reactivity with biomolecules. In addition, both the disinfectant concentration throughout the treatment, as well as the duration of the disinfection treatment (exposure time) are important parameters determining the disinfection efficiency. To be applicable in the context of sanitation, chemical disinfections must have several basic characteristics: they must be active against a wide range of pathogens; be sufficiently cost-effective to be applied frequently and in large quantities; be reasonably safe to produce, store and apply; and create a final product that is safe to be handled by humans or to be discharged into the environment. This chapter focuses on two groups of chemicals that meet these requirements, namely oxidants (mainly free chlorine) and bases (ammonia and lime). Oxidants are well-studied in the context of drinking water disinfection, though less information is available for the disinfection of sanitation-relevant matrices. Ammonia and lime are treatments that are exclusively used in the context of sanitation. For these chemical disinfectants, we have conducted a literature survey and collected kinetic data on their inactivation efficiencies in sanitation-relevant matrices. We have considered all pathogenic organisms described in part 3 of the GWPP, though data were only available for a subset of these organisms. In addition, we have included indicator organisms typically used to mimic the fate of pathogens during disinfection. The collected data were analyzed and visualized to provide an overview over the disinfection efficiency of chlorine, ammonia and lime toward different pathogen groups or individual organisms. In addition, whenever possible, the data were scrutinized with respect to the effects of important matrix properties, namely temperature, solids content, ammonia and organic matter content. We furthermore aimed to identify the least susceptible, process-limiting pathogens for each treatment, and to suggest suitable indicator organisms. Finally, treatment recommendations are provided, and we highlight major knowledge gaps that need to be addressed in order to refine these recommendations

Ammonia as an in-situ sanitizer: influence of virus genome type on inactivation

Treatment of human excreta and animal manure (HEAM) is key in controlling the spread of persistent enteric pathogens such as viruses. The extent of virus inactivation during HEAM storage and treatment appeared to vary with virus genome type, though the reasons for this variability are not clear. Here, we investigated the inactivation of viruses of different genome types under conditions representative of HEAM storage or mesophilic digestion. The goals were to characterize the influence of HEAM solution conditions on inactivation and to determine the potential mechanisms involved. Specifically, eight viruses representing the four viral genome types (ssRNA, dsRNA, ssDNA, dsDNA) were exposed to synthetic solutions with well-controlled temperature (20-35°C), pH (8-9) and ammonia concentrations (NH3; 0-40 mmol L-1). DNA and dsRNA viruses were considerably more resistant than ssRNA viruses, resulting in up to 1000-fold longer treatment times to reach a 4 log inactivation. The apparently slower inactivation of DNA viruses was rationalized by the higher stability of DNA compared to ssRNA in HEAM. Pushing the system toward harsher pH (> 9) and temperature (> 35°C) conditions, such as those encountered in thermophilic digestion and alkaline treatments, led to more consistent inactivation kinetics among ssRNA and other viruses. This suggests that the dependence of inactivation on genome type disappeared in favor of protein-mediated inactivation mechanisms common to all viruses. Finally, we recommend the use of MS2 as conservative indicator to assess the inactivation of ssRNA viruses, and the stable ΦX174 or dsDNA phages as indicators for persistent viruses

Variability in Disinfection Resistance between Currently Circulating Enterovirus B Serotypes and Strains

The susceptibility of waterborne viruses to disinfection is known to vary between viruses and even between closely related strains, yet the extent of this variation is not known. Here, different enteroviruses (six strains of coxsackievirus B5, two strains of coxsackievirus B4 and one strain of coxackievirus B1) were isolated from wastewater and inactivated by UV254, sunlight, free chlorine (FC), chlorine dioxide (ClO2), and heat. Inactivation kinetics of these isolates were compared with those of laboratory enterovirus strains (CVB5 Faulkner and echovirus 11 Gregory) and MS2 bacteriophage. FC exhibited the greatest (10-fold) variability in inactivation kinetics between different strains, whereas inactivation by UV254 differed only subtly. The variability in inactivation kinetics was greater between serotypes than it was among the seven strains of the CVB5 serotype. MS2 was a conservative surrogate of enterovirus inactivation by UV254, sunlight or heat, but frequently underestimated the disinfection requirements for FC and ClO2. Similarly, laboratory strains did not always reflect the inactivation behavior of the environmental isolates. Overall, there was considerable variability in inactivation kinetics among and within enteroviruses serotypes, as well as between laboratory and environmental isolates. We therefore recommend that future disinfection studies include a variety of serotypes and environmental isolates