[Microbiological aspects of pool water]. / L'acqua delle piscine: aspetti microbiologici.

It is well known that there is an elevated risk of diffusion of pathogenic micro-organisms in swimming pools. Preventive measures aimed at protecting the health of swimmers are complex because of the variety of micro-organisms involved, the different ways in which these can be transmitted and the involvement of both aquatic and environmental factors. In industrialised countries, the circulation of many pathogens which were common in the past has progressively decreased in recent years; in contrast, infections caused by emerging pathogens such as Pseudomonas, atypical mycobacteria, Aeromonas, Legionella, Cryptosporidium, Norwalk virus, adenovirus and rotavirus have increased in frequency. Such infections affect not only the gastrointestinal tract but also other body sites, in particular the skin, conjunctiva, respiratory tract and auditory apparatus. Opportunistic pathogens capable of causing potentially serious infections in debilitated and immunocompromised subjects may also be involved. It is clearly necessary, therefore, that preventive interventions and effective monitoring programs, regarding both pool water and environmental quality, be implemented in all swimming facilities.

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 Coxsackie B5. Chlorine dioxide was used at concentrations ranging from 0.2 to 0.8 mg/l in water solution, at pH 7 and at +20 degrees 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. Coxsackie 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 > or = 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 inactivation kinetics of hepatitis A virus and enteroviruses with peracetic acid and chlorine. New ICC/PCR method to assess disinfection effectiveness.

The virucidal activity of chlorine-compounds was studied using hepatitis A virus (HAV) and Poliovirus 2 and comparing the disinfectant efficiency of peracetic acid. HAV presented a higher resistance to HClO than Poliovirus did. With ClO2 the inactivation times of HAV were markedly shorter. A comparison between these data and those resulting from the kinetics with peracetic acid (PA) showed that PA is less effective than chlorine. As a preliminary to future research, the PCR-test integrated with cell-cultures was experimentally introduced for a quick evaluation of the HAV-infectiveness, with the aim of possible application in the field of disinfection and of viruses-isolation from environmental and food samples.

[Integrate cell culture--PCR (ICC/PCR) in viruses researches in environmental and food samples. Note I]. / L'integrazione colture cellulari--PCR (ICC/PCR) nella ricerca di virus in campioni ambientali e in alimenti. Nota I.

We carried out an experimental work integrating cell-culture and PCR to follow the HAV replication, to verify the PCR positiveness times and to confirm infectious viral particles presence. In tests HAV strain H59-175 was used. We proceeded to an initial valuation of the lowest viral concentration detectable by PCR. With viral titres between 10(5)-10(7) PFU/ml, the highest positive dilution resulted 10(-4)-10(-5). Then the 1 log lower dilution was inoculated in cell culture. At fixed times we proceeded to take surnatant and lisate samples for PCR test. After cell culture integration, positiveness was obtained in 72-120 hours against the 10-18 days necessary for CPE appearance.

[The concentration of viruses in water using the tangential flow ultrafiltration. Recovery effectiveness in experimental conditions]. / Impiego dell'ultrafiltrazione a flusso tangenziale per la concentrazione dei virus nelle acque. Valutazione dell'efficacia di recupero virale in condizioni sperimentali.

Poliovirus 1 concentration tests were carried out in artificially contaminated water by tangential flow ultrafiltration with Polisulfone filters 100000 MWCO. The tests were performed in 1 and in 20 liters of waters. The filters were conditioned and eluted respectively with Beef extract 3% and with glicina 1% at pH 7 and pH 9. The recovery mean using Beef extract resulted properly good, about the 83% and comparable to percentages we obtained in previous works with filters in cellulose nitrate and Virosorb filters. The viral recovery was low using the glicina for conditioning and eluting the filters.

[Comparative study on HAV and Poliovirus 2 inactivation cinetics with peracetic acid]. / Studio comparativo sulle cinetiche d'inattivazione dell'HAV e del Poliovirus 2 con acido peracetico. Nota I.

Hepatitis A virus and Poliovirus 2 inactivation tests were carried out using three peracetic acid concentrations (160, 320 and 640 mg/l) at different pH condition and at +20 degrees C temperature. HAV HM-175 strain was grown in FRhK4 cells and titrated in PFU (plaque technique) and the Poliovirus 2 strain was grown in monkey kidney cells RC-37 and titred in TCID50. The viral titration reduction was determined in the space of an hour with the disinfectant contact at 10-15 minutes intervals. The results obtained with the hepatitis A virus have shown a good linear trend between viral titration and contact time at the highest concentrations without any particular pH influence. The complete viral activity absence was achieved after 30-60 minutes of contact at 640 mg/l concentration. As regards Poliovirus 2 a good linear trend was highlighted between titrations and times at all the concentrations in shorter times at pH acid. The complete viral activity absence was obtained with 640 mg/l concentration after 30 minutes at pH acid. The HAV seems to own a higher resistance than Poliovirus 2 and Poliovirus 1 too.