Inactivation of bacteriophages in water by means of non-ionizing (uv-253.7nm) and ionizing (gamma) radiation: a comparative approach

110

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-proteincontent 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-proteincontent 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.Human caliciviruses are the most important enteric agents of gastroenteritis in industrialized countries (13,17). Many waterborne outbreaks associated with noroviruses have been reported (1,3,5,10,15). Usually, epidemiological data prove that water was the common source for the outbreak, and in some molecular tracing studies norovirus strains were successfully identified in the source water and identical sequences were found in stools from patients (4,8,11,12,16). Virus concentrations in source water may peak with sewage overflow due to heavy rainfall or leaking septic tanks or pipes (2, 20). Breakdown or malfunctioning of water treatment plants may lead to insufficient reductions in virus concentrations in drinking water (20). Moreover, European legislation is mainly based on bacteriological quality parameters that determine fecal contamination of food and water. Viruses, however, are more resistant to treatment (9), are generally harder to detect, and exhibit lower dose-response relationships than bacteria. Therefore, water may meet microbiological safety guidelines but still pose a considerable health hazard.Irradiation treatment is being used more frequently for disinfection of food and water. Bacteriophages have been used as indicators for inactivation of viruses by ionizing and nonionizing radiation since bacteria are generally less resista...

Section: Discussionmentioning

confidence: 57%

Section: Discussionmentioning

confidence: 99%

Calicivirus Inactivation by Nonionizing (253.7-Nanometer-Wavelength [UV]) and Ionizing (Gamma) Radiation

Husman¹,

Bijkerk

Lodder³

et al. 2004

110

“…The stock suspension of oocysts was diluted with 10 mM NaCl, buffered to a pH of 8.0, to a concentration of 1 ϫ 10 6 oocysts/ml. Portions of 25 ml of the working suspension were exposed in sterile petri dishes under permanent stirring in a standard laboratory irradiation apparatus (with lowpressure lamps) as described in detail elsewhere (31). The UV fluence applied was 800 J/m 2 254-nm UV.…”

Section: Methodsmentioning

confidence: 99%

Biotin- and Glycoprotein-Coated Microspheres as Surrogates for Studying Filtration Removal of Cryptosporidium parvum in a Granular Limestone Aquifer Medium

Stevenson

Blaschke

Toze

et al. 2015

Members of the genus Cryptosporidium are waterborne protozoa of great health concern. Many studies have attempted to find appropriate surrogates for assessing Cryptosporidium filtration removal in porous media. In this study, we evaluated the filtration of Cryptosporidium parvum in granular limestone medium by the use of biotin-and glycoprotein-coated carboxylated polystyrene microspheres (CPMs) as surrogates. Column experiments were carried out with core material taken from a managed aquifer recharge site in Adelaide, Australia. For the experiments with injection of a single type of particle, we observed the total removal of the oocysts and glycoprotein-coated CPMs, a 4.6-to 6.3-log 10 reduction of biotin-coated CPMs, and a 2.6-log 10 reduction of unmodified CPMs. When two different types of particles were simultaneously injected, glycoprotein-coated CPMs showed a 5.3-log 10 reduction, while the uncoated CPMs displayed a 3.7-log 10 reduction, probably due to particle-particle interactions. Our results confirm that glycoprotein-coated CPMs are the most accurate surrogates for C. parvum; biotin-coated CPMs are slightly more conservative, while unmodified CPMs are markedly overly conservative for predicting C. parvum removal in granular limestone medium. The total removal of C. parvum observed in our study suggests that granular limestone medium is very effective for the filtration removal of C. parvum and could potentially be used for the pretreatment of drinking water and aquifer storage recovery of recycled water. W aterborne cryptosporidiosis is mainly caused by Cryptosporidium parvum and Cryptosporidium hominis in humans (1). Cryptosporidium can be found in water contaminated with infected human or animal feces and has a low infectious dose, and ingestion of less than 10 oocysts can lead to infection (2). Cryptosporidium oocysts are sometimes detected in drinking water supplies (3) and in potable groundwater (4), causing disease outbreaks. For example, in the 1993 cryptosporidiosis outbreak in Milwaukee, WI, USA, about 400,000 people were infected and more than 100 people died after contamination of drinking water by C. parvum (5). More recently, a waterborne outbreak of cryptosporidiosis in Ö stersund, Sweden, which infected 27,000 people in 2010, was caused by C. hominis (6).C. parvum can survive in surface water and groundwater for a long period of time (7) and is resistant to chemical disinfection, like chlorination (8) and ozonation (9), due to its thick oocyst wall. UV irradiation with low-and medium-pressure lamps has been found to be effective at inactivating C. parvum (10). However, the efficacy of UV irradiation as well as that of chemical disinfection is hampered by turbidity in the water. Thus, filtration is often used as an essential primary step for drinking water treatment in the course of a multibarrier treatment system because it is effective and cost-efficient.Because it is extremely infectious and highly resistant to chlorination, testing for C. parvum is often used in risk analysis of drin...

“…Bacteria are more readily inactivated by chlorination than are protozoa (49). Viruses are effectively removed or inactivated by slow sand filtration and soil passage, but they are more resistant to UV and coagulation combined with sedimentation (9,43,50). However, a very low concentration of virus may suffice to cause infection, e.g., from 10 to Ͻ10 4 norovirus PCR-detectable units (PDU), leading to gastrointestinal disease in two-thirds of the individuals infected (30).…”

mentioning

confidence: 99%

Presence of Noroviruses and Other Enteric Viruses in Sewage and Surface Waters in The Netherlands

Lodder

Husman

2005

341

201

Since virus concentrations in drinking waters are generally below the detection limit, the infectious risk from drinking water consumption requires assessment from the virus concentrations in source waters and removal efficiency of treatment processes. In this study, we estimated from reverse transcription-PCR on 10-fold serially diluted RNA that noroviruses, the most prevalent waterborne gastroenteritis agents, were present at 4 (0.2 to 38) to 4,900 (303 to 4.6 ؋ 10 4 ) PCR-detectable units (PDU) per liter of river water (ranges are given in parentheses). These virus concentrations are still high compared with 896 to 7,499 PDU/liter of treated sewage and 5,111 to 850,000 PDU/liter in raw sewage. Sequencing analyses designated human norovirus GGII.4 Lordsdale as the most prevalent strain in the sampling period 1998 to 1999 in both sewage and surface waters. Other GGII strains were also very abundant, indicating that the majority of the virus contamination was derived from urban sewage, although very divergent strains and one animal strain were also detected in the surface and sewage waters. Rotaviruses were also detected in two large rivers (the Maas and the Waal) at 57 to 5,386 PDU/liter. The high virus concentrations determined by PCR may in part be explained by the detection of virus RNA instead of infectious particles. Indeed, reoviruses and enteroviruses that can be cultured were present at much lower levels, of 0.3 to 1 and 2 to 10 PFU/liter, respectively. Assuming 1% of the noroviruses and rotaviruses to be infectious, a much higher disease burden than for other viruses can be expected, not only because of the higher levels but also because of these viruses' higher infectivity and attack rates.