Calicivirus inactivation by nonionizing (253.7-nanometer-wavelength [UV]) and ionizing (gamma) radiation

Noroviruses (previously Norwalk-like viruses) are the most common viral agents associated with food- and waterborne outbreaks of gastroenteritis. In the absence of culture methods for noroviruses, animal caliciviruses were used as model viruses to study inactivation by nonionizing (253.7-nm-wavelength [UV]) and ionizing (gamma) radiation. Here, we studied the respiratory feline calicivirus (FeCV) and the presumed enteric canine calicivirus (CaCV) and compared them with the well-studied bacteriophage MS2. When UV irradiation was used, a 3-log(10) reduction was observed at a fluence of 120 J/m(2) in the FeCV suspension and at a fluence of 200 J/m(2) for CaCV; for the more resistant phage MS2 there was a 3-log(10) reduction at a fluence of 650 J/m(2). Few or no differences were observed between levels of UV inactivation in high- and low-protein-content virus stocks. In contrast, ionizing radiation could readily inactivate MS2 in water, and there was a 3-log(10) reduction at a dose of 100 Gy, although this did not occur when the phage was diluted in high-protein-content stocks of CaCV or FeCV. The low-protein-content stocks showed 3-log(10) reductions at a dose of 500 Gy for FeCV and at a dose of 300 for CaCV. The inactivation rates for both caliciviruses with ionizing and nonionizing radiation were comparable but different from the inactivation rates for MS2. Although most FeCV and CaCV characteristics, such as overall particle and genome size and structure, are similar, the capsid sequences differ significantly, making it difficult to predict human norovirus inactivation. Adequate management of UV and gamma radiation processes for virus inactivation should limit public health risks.     

Inactivation of Feline Calicivirus and Adenovirus Type 40 by UV Radiation

Little information regarding the effectiveness of UV radiation on the inactivation of caliciviruses and enteric adenoviruses is available. Analysis of human calicivirus resistance to disinfectants is hampered by the lack of animal or cell culture methods that can determine the viruses' infectivity. The inactivation kinetics of enteric adenovirus type 40 (AD40), coliphage MS-2, and feline calicivirus (FCV), closely related to the human caliciviruses based on nucleic acid organization and capsid architecture, were determined after exposure to low-pressure UV radiation in buffered demand-free (BDF) water at room temperature. In addition, UV disinfection experiments were also carried out in treated groundwater with FCV and AD40. AD40 was more resistant than either FCV or coliphage MS-2 in both BDF water and groundwater. The doses of UV required to achieve 99% inactivation of AD40, coliphage MS-2, and FCV in BDF water were 109, 55, and 16 mJ/cm², respectively. The doses of UV required to achieve 99% inactivation of AD40, coliphage MS-2, and FCV in groundwater were slightly lower than those in BDF water. FCV was inactivated by 99% by 13 mJ/cm² in treated groundwater. A dose of 103 mJ/cm² was required for 99% inactivation of AD40 in treated groundwater. The results of this study indicate that if FCV is an adequate surrogate for human caliciviruses, then their inactivation by UV radiation is similar to those of other single-stranded RNA enteric viruses, such as poliovirus. In addition, AD40 appears to be more resistant to UV disinfection than previously reported.     

Inactivation of Thirty Viruses by Gamma Radiation

Decimal reduction values (D value) for 30 viruses were determined. The weighted D values of the viruses suspended in Eagle's minimum essential medium ranged from 0.39 to 0.53 Mrads. It was necessary to increase the radiation dose by a factor of >3 to inactivate virus suspended in Eagle's minimum essential medium as compared to the same virus suspended in distilled water. The destruction rate curves were of a first-order reaction.     

Inactivation of Single-Celled Ascaris suum Eggs by Low-Pressure UV Radiation

Intact and decorticated single-celled Ascaris suum eggs were exposed to UV radiation from low-pressure, germicidal lamps at fluences (doses) ranging from 0 to 8,000 J/m² for intact eggs and from 0 to 500 J/m² for decorticated eggs. With a UV fluence of 500 J/m², 0.44- ± 0.20-log inactivation (mean ± 95% confidence interval) (63.7%) of intact eggs was observed, while a fluence of 4,000 J/m² resulted in 2.23- ± 0.49-log inactivation (99.4%). (The maximum quantifiable inactivation was 2.5 log units.) Thus, according to the methods used here, Ascaris eggs are the most UV-resistant water-related pathogen identified to date. For the range of fluences recommended for disinfecting drinking water and wastewater (200 to 2,000 J/m²), from 0- to 1.5-log inactivation can be expected, although at typical fluences (less than 1,000 J/m²), the inactivation may be less than 1 log. When the eggs were decorticated (the outer egg shell layers were removed with sodium hypochlorite, leaving only the lipoprotein ascaroside layer) before exposure to UV, 1.80- ± 0.32-log reduction (98.4%) was achieved with a fluence of 500 J/m², suggesting that the outer eggshell layers protected A. suum eggs from inactivation by UV radiation. This protection may have been due to UV absorption by proteins in the outer layers of the 3- to 4-μm-thick eggshell. Stirring alone (without UV exposure) also inactivated some of the Ascaris eggs (~20% after 75 min), which complicated determination of the inactivation caused by UV radiation alone.     

Inactivation of Enteric Adenovirus and Feline Calicivirus by Chlorine Dioxide

Chlorine dioxide (ClO₂) inactivation experiments were conducted with adenovirus type 40 (AD40) and feline calicivirus (FCV). Experiments were carried out in buffered, disinfectant demand-free water under high- and low-pH and -temperature conditions. Ct values (the concentration of ClO₂ multiplied by contact time with the virus) were calculated directly from bench-scale experiments and from application of the efficiency factor Hom (EFH) model. AD40 Ct ranges for 4-log inactivation (Ct_99.99%) at 5°C were >0.77 to <1.53 mg/liter × min and >0.80 to <1.59 mg/liter × min for pH 6 and 8, respectively. For 15°C AD40 experiments, >0.49 to <0.74 mg/liter × min and <0.12 mg/liter × min Ct_99.99% ranges were observed for pH 6 and 8, respectively. FCV Ct_99.99% ranges for 5°C experiments were >20.20 to <30.30 mg/liter × min and >0.68 mg/liter × min for pH 6 and 8, respectively. For 15°C FCV experiments, Ct_99.99% ranges were >4.20 to <6.72 and <0.18 mg/liter × min for pH 6 and 8, respectively. Viral inactivation was higher at pH 8 than at pH 6 and at 15°C than at 5°C. Comparison of Ct values and inactivation curves demonstrated that the EFH model described bench-scale experiment data very well. Observed bench-scale Ct_99.99% ranges and EFH model Ct_99.99% values demonstrated that FCV is more resistant to ClO₂ than AD40 for the conditions studied. U.S. Environmental Protection Agency guidance manual Ct_99.99% values are higher than Ct_99.99% values calculated from bench-scale experiments and from EFH model application.     

Inactivation by Ionizing Radiation of Salmonella enteritidis Serotype montevideo Grown in Composed Sewage Sludge

S. enteritidis ser. montevideo were grown in composted sewage sludge to levels of approximately 10⁹/g. These bacteria were found to be inactivated by ionizing radiation at approximately the same rate (30 krads/log) as Salmonella species in liquid digested sludge.     

Some Characteristics of the Resistance Transfer Factor (RTF) Episome as Determined by Inactivation with Tritium, P32, and Gamma Radiation

The resistance transfer factor (RTF) episome was studied by measuring its inactivation by Co⁶⁰ gamma radiation, by incorporated P³², and by tritium incorporated as tritium-labeled thymine. The D₃₇ for Co⁶⁰ irradiation was 7 to 9 × 10⁴ rad. Growth of the bacteria harboring the RTF in BUdR (bromouracil deoxyriboside) increased the sensitivity of the RTF to the gamma radiation. The RTF was markedly inactivated by tritium after growth of the host (thymine requiring) bacteria in tritium-labeled thymine, thus further establishing the presence of thymine in the genome of the RTF. Assuming the efficiency of inactivation by P³² to be 10%, the phosphorus content of the RTF was estimated to be about 2 × 10⁵ P atoms/episome. The data suggest the RTF contains double stranded DNA with a molecular weight of the order of 3 to 8 × 10⁷.     

Inactivation of nuclear polyhedrosis virus (Baculovirus subgroup A) by monochromatic UV radiation

Monochromatic radiation at wavelengths of 290, 300, 310, and 320 nm inactivated occluded nuclear polyhedrosis virus of the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough). Data indicate that all of the wavelengths are capable of causing virus inactivation; much greater fluences are needed for virus inactivation as the wavelength increases.     

Inactivation of nuclear polyhedrosis virus (Baculovirus subgroup A) by monochromatic UV radiation.

Monochromatic radiation at wavelengths of 290, 300, 310, and 320 nm inactivated occluded nuclear polyhedrosis virus of the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough). Data indicate that all of the wavelengths are capable of causing virus inactivation; much greater fluences are needed for virus inactivation as the wavelength increases.     

Oligodeoxyribonucleoside methylphosphonates. NMR and UV spectroscopic studies of Rp-Rp and Sp-Sp methylphosphonate (Me) modified duplexes of (d[GGAATTCC])2.

1H NMR chemical shift assignments for the title compounds were made for most of the 1H signals using two-dimensional nuclear Overhauser effect (2D-NOE) data, which were also used to establish the absolute configuration at the modified phosphorus. The chemical shifts were similar to those reported [Broido, M.S., et al. (1985) Eur. J. Biochem. 150, 117-128] for the unmodified, parent, B-type duplex [d(GGAATTCC)]2. Differences in chemical shifts were mostly localized to the nucleotides on the 5'- and 3'-sides of the modified phosphorus. The Rp-Rp isomers exhibited UV-derived Tm values similar to that of the parent duplex. On the other hand, the Sp-Sp isomers generally exhibited lower Tm values which correlated with P-CH3--H3' (n-1 nucleotide) cross peak intensities and 31P spectral parameters. The combined data argue for increased steric interactions with the Sp-P-Me methyl group as the modification position is moved toward the center of the oligomer. All of the Tm results can be explained in terms of three factors which result from replacement of a phosphate by a methylphosphonate group: reduction of oligomer charge; electronic and other substituent effects; steric interactions.     

Suppression of Spoilage Rates of Bombay Duck (Harpodon nehereus) Homogenates by Gamma Radiation

The spoilage rates of unirradiated and irradiated (0.1 Mrad) Bombay duck (Harpodon nehereus) homogenates stored at 0°C, 10°C and 30°C in terms of organoleptic score (OS) total bacterial count (TBC), trimethylamine content (TMA), and total volatile basic nitrogen (TVBN) followed a linear response with increase in temperature. Unirradiated Bombay duck stored at 0°C were found to spoil faster than those irradiated at 0.1 Mrad; the spoilage rates derived for TBC, TMA, TVBN and OS were 0.42, 0.67, 1.93 and ?0.86 respectively for unirradiated samples as compared with corresponding values of 0.31, 0.55, 1.19 and ?0.19 for the irradiated samples. The spoilage rates of unirradiated Bombay duck stored at 10°C and 30°C measured as a function of OS, TMA and TVBN were consistently higher than their irradiated (0.1 Mrad) counterparts. In the case of irradiated samples, TBC was not a satisfactory index of spoilage.     

Lysozyme Modification by the Fenton Reaction and Gamma Radiation

A comparative study was performed on lysozyme modification after exposure to Fenton reagent (Fe(II)/H 2 O 2 ) or hydroxyl radicals produced by &#110 radiation. The conditions were adjusted to obtain, with both systems, a 50% loss of activity of the modified ensemble. &#110 radiation modified almost all types of amino acid residues in the enzyme, with little specificity. The modification order was Tyr > Met=Cys > Lys > Ile+Leu > Gly > Pro=Phe>Thr+Ala>Trp=Ser>Arg>Asp+Glu, with 42 mol of modified residues per initial mole of native enzyme. In contrast, when the enzyme was exposed to the Fenton reaction, only some types of amino acids were modified. Furthermore, a smaller number of residues (13.5) were damaged per initial mole of enzyme. The order of the modified residues was Tyr > Cys > Trp > Met >His > Ile+Leu > Val > Arg. These results demonstrate that the modifications elicited by these two free radical sources follow different mechanisms. An intramolecular free radical chain reaction is proposed to play a dominant role in the oxidative modification of the protein promoted by &#110 radiation.     

Comparative Inactivation of Enteroviruses and Adenovirus 2 by UV Light

The doses of UV irradiation necessary to inactivate selected enteric viruses on the U.S. Environmental Protection Agency Contaminant Candidate List were determined. Three-log reductions of echovirus 1, echovirus 11, coxsackievirus B3, coxsackievirus B5, poliovirus 1, and human adenovirus type 2 were effected by doses of 25, 20.5, 24.5, 27, 23, and 119 mW/cm², respectively. Human adenovirus type 2 is the most UV light-resistant enteric virus reported to date.     

External morphology of adult Libythea celtis (Laicharting [1782]) (Lepidoptera: Nymphalidae)

Libytheinae is a morphologically unusual group of butterflies whose external anatomy has never been described in detail. The subfamily is considered basal within the diverse family Nymphalidae, and libytheines retain many plesiomorphic features, such as a functional female foreleg and smooth larva. In this paper, we describe and illustrate the adult morphology of Libythea celtis Laicharting, make comparisons to other nymphalid subfamilies, and homologize terms whenever possible. We describe major sclerites, sulci, and the presence of cranial and lateral pits on the tibia, the latter which appear to be previously unreported from the lepidopteran literature. When present, sexual dimorphism and geographic variation are noted. It is hoped that the present paper will help stabilize inconsistencies in morphological terms in nymphalid butterflies.     

Investigation of DNA Damage Induced by Proton and Gamma Radiation

Biophysics - In this study, we compared the effects of gamma and high-energy proton radiation (1000 MeV) on DNA in aqueous saline solutions (5 and 150 mM NaCl) at doses of 30 and 50 Gy. We used...     

Inactivation of feline calicivirus and adenovirus type 40 by UV radiation

Little information regarding the effectiveness of UV radiation on the inactivation of caliciviruses and enteric adenoviruses is available. Analysis of human calicivirus resistance to disinfectants is hampered by the lack of animal or cell culture methods that can determine the viruses' infectivity. The inactivation kinetics of enteric adenovirus type 40 (AD40), coliphage MS-2, and feline calicivirus (FCV), closely related to the human caliciviruses based on nucleic acid organization and capsid architecture, were determined after exposure to low-pressure UV radiation in buffered demand-free (BDF) water at room temperature. In addition, UV disinfection experiments were also carried out in treated groundwater with FCV and AD40. AD40 was more resistant than either FCV or coliphage MS-2 in both BDF water and groundwater. The doses of UV required to achieve 99% inactivation of AD40, coliphage MS-2, and FCV in BDF water were 109, 55, and 16 mJ/cm(2), respectively. The doses of UV required to achieve 99% inactivation of AD40, coliphage MS-2, and FCV in groundwater were slightly lower than those in BDF water. FCV was inactivated by 99% by 13 mJ/cm(2) in treated groundwater. A dose of 103 mJ/cm(2) was required for 99% inactivation of AD40 in treated groundwater. The results of this study indicate that if FCV is an adequate surrogate for human caliciviruses, then their inactivation by UV radiation is similar to those of other single-stranded RNA enteric viruses, such as poliovirus. In addition, AD40 appears to be more resistant to UV disinfection than previously reported.     

Predictive Model for Inactivation of Feline Calicivirus, a Norovirus Surrogate, by Heat and High Hydrostatic Pressure

Noroviruses, which are members of the Caliciviridae family, represent the leading cause of nonbacterial gastroenteritis in developed countries; such norovirus infections result in high economic costs for health protection. Person-to-person contact, contaminated water, and foods, especially raw shellfish, vegetables, and fruits, can transmit noroviruses. We inactivated feline calicivirus, a surrogate for the nonculturable norovirus, in cell culture medium and mineral water by heat and high hydrostatic pressure. Incubation at ambient pressure and 75°C for 2 min as well as treatment at 450 MPa and 15°C for 1 min inactivated more than 7 log₁₀ PFU of calicivirus per ml in cell culture medium or mineral water. The heat and pressure time-inactivation curves obtained with the calicivirus showed tailing in the logarithmic scale. Modeling by nth-order kinetics of the virus inactivation was successful in predicting the inactivation of the infective virus particles. The developed model enables the prediction of the calicivirus reduction in response to pressures up to 500 MPa, temperatures ranging from 5 to 75°C, and various treatment times. We suggest high pressure for processing of foods to reduce the health threat posed by noroviruses.