INVESTIGATION ON VIRUCIDAL ACTIVITY OF CHLORINE DIOXIDE. EXPERIMENTAL DATA ON FELINE CALICIVIRUS, HAV AND COXSACKIE B5

Introduction. The aim of this study was to evaluate the efficacy of ClO2 with regard to viruses which show a particular resistance to oxidizing agent such as HAV and Norwalk and Norwalk-like viruses, and which play an important role in the epidemiology of viral foodborne diseases. In the food industry, disinfection of processing systems and equipment is a very important instrument to prevent secondary contamination and to guarantee food safety. Among disinfectants, chlorine dioxide (ClO2) presents a good efficacy at wide range of pH values, its action is rapid and generates few reaction byproducts if compared to hypoclorite. Experimental studies have highlighted that ClO2 shows a good bactericidal activity and it is also active towards viruses. Furthermore, the low concentrations and low contact times required to obtain microbial load reduction are favourable elements for the application of this compound in the industrial sanitizing practices. Methods. As it is impossible to cultivate the Norwalk virus in vitro, we tested the resistance of Feline calicivirus (F9 strain) vs. ClO2, in comparison with HAV (strain HM-175) and CoxsackieB5. Chlorine dioxide was used at concentrations ranging from 0.2 to 0.8 mg/l in water solution, at pH 7 and at +20 °C. Viral suspensions were added to disinfecting solution and, at pre-set times, were sampled to undergo to titration after blocking the disinfectant action with thiosulphate 0.05 M. On the basis of the data obtained, for each virus and in relation to different concentrations, mean reduction times were calculated for 99%, 99.9% and 99.99% using the regression analysis model. Results. As regards Feline calicivirus, at a concentration of 0.8 mg/l of ClO2, we obtained the complete elimination of the viral titre in 2 min while 30 min were required at concentrations of 0.2 mg/l. Coxackie B5 showed a similar behaviour, being completely inactivated in 4 min with 0.4 mg/l of ClO2 and after 30 min at a concentration of 0.2 mg/l. Inactivation was quicker for HAV, which was eliminated after only 30 sec at a concentration of 0.8 mg/l and after 5 min at 0.4 mg/l. Conclusion. Our data show that for complete inactivation of HAV and Feline calicivirus, concentrations ≥ 0.6 mg/l are required. This observation is true for Coxsackie B5 too, but this virus has shown a good sensitivity at all concentration tested according to regression analysis results. For Feline calicivirus and HAV, at low concentrations of disinfectant, prolonged contact times were needed to obtain a 99.99% reduction of viral titres (about 16 and 20 minutes respectively)

Study on the Application of a New Method for the Viral Detection of Caliciviruses in Foodstuffs

Abstract Noroviruses (NoVs

Recovery tests of cytopathogenic viruses from artificiallycontaminated food samples

Abstract The artificial contamination tests were carried out by using a Coxsackie B5 virus of known titration to contaminate vegetable food products (lettuce and berries). The experimental protocol was divided basically into two phases: elution with alkaline pH buffer solution and following concentration of viral particles recovered by using PEG8000 (polyethylene glycol). A third phase of purification with chloroform was introduced between these two steps in order to assess its effect on the yield of the final recovery, and tests were performed in parallel with both the protocols to compare them in terms of recovery efficiency. Elution phase proved to be the most critical, since the viral recovery from food samples during this phase resulted moderate (2.95% and 2.16% respectively in tests without and with chloroform purification phase), data already observed in previous studies. The final concentration phase with PEG8000 recorded average recoveries equalling 0.29% in tests without chloroform and equalling 3.97% in tests with purification phase, thus showing a significant improvement with a lesser interference by the organic material

PCR, Real-Time PCR analysis on Norwalk virus direct test on artificial-contaminated foodstuff

Introduction: The most commonly used methods to determine and identify Norwalk virus are based on molecular biology. Methods: A viral extraction protocol from food samples was studied in this work using artificial contamination test. It consists of a new protocol with a phase of viral elution from the food matrix performed using an eluting solution (glycine and beef extract at 3% pH 9) and a concentration phase with polyethylene glycol 8000. To detect Noroviruses, two techniques of molecular biology, polymerase chain reaction and real-time polymerase chain reaction, were compared. At the same time, tests of direct viral identification were conducted on soft fruits and salad obtained from the market. Results: From the results obtained it was possible to evaluate how the phase of viral recovery represents an important critical point of the protocol. Conclusion: It was possible to identify a greater sensitivity of the real-time polymerase chain reaction compared with the traditional polymerase chain reaction