Quantifying the reduction in potential health risks by determining the sensitivity of poliovirus type 1 chat strain and rotavirus SA-11 to electron beam irradiation of iceberg lettuce and spinach.

Fresh produce, such as lettuce and spinach, serves as a route of food-borne illnesses. The U.S. FDA has approved the use of ionizing irradiation up to 4 kGy as a pathogen kill step for fresh-cut lettuce and spinach. The focus of this study was to determine the inactivation of poliovirus and rotavirus on lettuce and spinach when exposed to various doses of high-energy electron beam (E-beam) irradiation and to calculate the theoretical reduction in infection risks that can be achieved under different contamination scenarios and E-beam dose applications. The D(10) value (dose required to reduce virus titers by 90%) (standard error) of rotavirus on spinach and lettuce was 1.29 (± 0.64) kGy and 1.03 (± 0.05) kGy, respectively. The D(10) value (standard error) of poliovirus on spinach and lettuce was 2.35 (± 0.20) kGy and 2.32 (± 0.08) kGy, respectively. Risk assessment of data showed that if a serving (∼14 g) of lettuce was contaminated with 10 PFU/g of poliovirus, E-beam irradiation at 3 kGy will reduce the risk of infection from >2 in 10 persons to approximately 6 in 100 persons. Similarly, if a serving size (∼0.8 g) of spinach is contaminated with 10 PFU/g of rotavirus, E-beam irradiation at 3 kGy will reduce infection risks from >3 in 10 persons to approximately 5 in 100 persons. The results highlight the value of employing E-beam irradiation to reduce public health risks but also the critical importance of adhering to good agricultural practices that limit enteric virus contamination at the farm and in packing houses.

Infectivity and genome persistence of rotavirus and astrovirus in groundwater and surface water.

In this work, we have characterized the survival of Rhesus rotavirus (RRV) and human astrovirus Yuc8 in clean groundwater and contaminated surface water, as well as in phosphate-buffered solutions maintained in the same conditions as the environmental waters, and have compared the dynamics of virus inactivation with the persistence of the viral genomes, as determined by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). In addition, we also studied the tolerance of these viruses to chlorine disinfection. The reduction of infectivity of astrovirus was higher than for rotavirus, and also higher for both viruses in surface water as compared to groundwater. The enterobacterial content of the water as well as extrinsic factors, such as temperature and light, correlated with the stability of virus infectivity, and with the persistence of the virus genetic material, suggesting that molecular techniques to detect and quantify viral genomes would be suitable for the detection of viruses in water. The virus infectivity persisted in both types of water as well as in chlorine for times longer than previously reported. No decrease of infectivity was observed after 15 days of incubation in either type of water and the viruses remained infectious for months in groundwater. After 120 min in groundwater containing 2 mg/L of free chlorine, the infectivity of rotavirus and astrovirus was reduced by 0.78 and 1.3 logs, respectively. The longer persistence of viruses in this study could result from a combination of factors, including aggregation of the virus.

Microbial distribution and turnover in Antarctic microbial mats highlight the relevance of heterotrophic bacteria in low-nutrient environments.

Maritime Antarctica has shown the highest increase in temperature in the Southern Hemisphere. Under this scenario, biogeochemical cycles may be altered, resulting in rapid environmental change for Antarctic biota. Microbes that drive biogeochemical cycles often form biofilms or microbial mats in continental meltwater environments. Limnetic microbial mats from the Fildes Peninsula were studied using high-throughput 16S rRNA gene sequencing. Mat samples were collected from 15 meltwater stream sites, comprising a natural gradient from ultraoligotrophic glacier flows to meltwater streams exposed to anthropogenic activities. Our analyses show that microbial community structure differences between mats are explained by environmental NH4+, NO3-, DIN, soluble reactive silicon and conductivity. Microbial mats living under ultraoligotrophic meltwater conditions did not exhibit a dominance of cyanobacterial photoautotrophs, as has been documented for other Antarctic limnetic microbial mats. Instead, ultraoligotrophic mat communities were characterized by the presence of microbes recognized as heterotrophs and photoheterotrophs. This suggests that microbial capabilities for recycling organic matter may be a key factor to dwell in ultra-low nutrient conditions. Our analyses show that phylotype level assemblages exhibit coupled distribution patterns in environmental oligotrophic inland waters. The evaluation of these microbes suggests the relevance of reproductive and structural strategies to pioneer these psychrophilic ultraoligotrophic environments.