Comparative study of hyperpure chlorine dioxide with two other irrigants regarding the viability of periodontal ligament stem cells.

OBJECTIVES: Periodontal ligament stem cells (PDLSCs) have an underlined significance as their high proliferative capacity and multipotent differentiation provide an important therapeutic potential. The integrity of these cells is frequently disturbed by the routinely used irrigative compounds applied as periodontal or endodontic disinfectants (e.g., hydrogen peroxide (H2O2) and chlorhexidine (CHX)). Our objectives were (i) to monitor the cytotoxic effect of a novel dental irrigative compound, chlorine dioxide (ClO2), compared to two traditional agents (H2O2, CHX) on PDLSCs and (ii) to test whether the aging factor of PDLSC cultures determines cellular responsiveness to the chemicals tested. METHODS: Impedimetry (concentration-response study), WST-1 assays (WST = water soluble tetrazolium salt), and morphology analysis were performed to measure changes in cell viability induced by the 3 disinfectants; immunocytochemistry of stem cell markers (STRO-1, CD90, and CD105) measured the induced mesenchymal characteristics. RESULTS: Cell viability experiments demonstrated that the application of ClO2 does not lead to a significant decrease in viability of PLDSCs in concentrations used to kill microbes. On the contrary, traditional irrigants, H2O2, and CHX are highly toxic on PDLSCs. Aging of PLDSC cultures (passages 3 vs. 7) has characteristic effects on their responsiveness to these agents as the increased expression of mesenchymal stem cell markers turns to decreased. CONCLUSIONS AND CLINICAL RELEVANCE: While the active ingredients of mouthwash (H2O2, CHX) applied in endodontic or periodontitis management have a serious toxic effect on PDLSCs, the novel hyperpure ClO2 is less toxic providing an environment favoring dental structure regenerations during disinfectant interventions.

Kinetics and Mechanisms of Virus Inactivation by Chlorine Dioxide in Water Treatment: A Review.

Chlorine dioxide (ClO2), an alternative disinfectant to chlorine, has been widely applied in water and wastewater disinfection. This paper aims at presenting an overview of the inactivation kinetics and mechanisms of ClO2 with viruses. The inactivation efficiencies vary greatly among different virus species. The inactivation rates for different serotypes within a family of viruses can differ by over 284%. Generally, to achieve a 4-log removal, the exposure doses, also being referred to as Ct values (mutiplying the concentration of ClO2 and contact time) vary in the range of 0.06-10 mg L-1 min. Inactivation kinetics of viruses show two phases: an initial rapid inactivation phase followed by a tailing phase. Inactivation rates of viruses increase as pH or temperature increases, but show different trends with increasing concentrations of dissolved organic matter (DOM). Both damages in viral proteins and in the 5' noncoding region within the genome contribute to virus inactivation upon ClO2 disinfection.

Aqueous chlorine dioxide treatment of horticultural produce: Effects on microbial safety and produce quality-A review.

Microbial load on fresh fruit and vegetables causes decay and losses after harvest and may lead to foodborne illness in case of contamination with human pathogens on raw consumed produces. Washing with tap water only marginally reduces microorganisms attached to produce surfaces. Chlorine is widely used for decontamination on fresh horticultural produces. However, due to harmful by-products and the questionable efficacy it has become increasingly challenged. During the last 20 years, the interest to study ClO2 treatments as an alternative sanitation agent for industrially prepared fresh produce has largely increased. For a wide range of commodities, the application of gaseous ClO2 has meanwhile been investigated. In addition, since several years, the interest in aqueous ClO2 treatments has further risen because of the better manageability in postharvest processing lines compared to gaseous application. This article critically evaluated the effects of postharvest application of aqueous ClO2, either alone or in combination with other treatments, on microbial loads for various horticultural produces. In laboratory investigations, application of aqueous ClO2 at concentrations between 3 and 100 ppm effectively reduced counts of natural or inoculated microorganisms (bacteria, yeasts, and mold) in the range of 1 and 5 log. However, various effects of ClO2 treatments on produce quality have been described. These mainly comprise implication on sensory and visual attributes. In this context, there is increasing focus on the potential impacts of aqueous ClO2 on relevant nutritional components of produces such as organic acids or phenolic substances.

Irrigating Lettuce with Wastewater Effluent: Does Disinfection with Chlorine Dioxide Inactivate Viruses?

Reclaimed water obtained from urban wastewater is currently being used as irrigation water in water-scarce regions in Spain. However, wastewater can contain enteric viruses that water reclamation treatment cannot remove or inactivate completely. In the present study, greenhouse-grown baby lettuce ( L.) was irrigated with secondary treatment effluent from a wastewater treatment plant untreated and treated using chlorine dioxide (ClO). The effect of ClO treatment on the physicochemical characteristics and the presence of enteric viruses in irrigation water and lettuce was assessed. The presence of human noroviruses genogroups I and II (NoV GI and NoV GII), and human astroviruses (HAstV), was analyzed by real-time polymerase chain reaction (RT-qPCR). Additionally, to check for the loss of infectivity induced by the disinfection treatment, positive samples were re-analyzed after pretreatment with the intercalating dye PMAxx before RNA extraction and RT-qPCR. There were no significant differences in the proportion of positive samples and the concentration of enteric viruses between treated and untreated reclaimed water without PMAxx pretreatment ( > 0.05). A significantly lower concentration of NoV GI was detected in ClO-treated water when samples were pretreated with PMAxx ( < 0.05), indicating that inactivation was due to the disinfection treatment. Laboratory-scale validation tests indicated the suitability of PMAxx-RT-qPCR for discrimination between potentially infectious and ClO-damaged viruses. Although the applied ClO treatment was not able to significantly reduce the enteric virus load of the secondary effluent from the wastewater treatment plant, none of the lettuce samples analyzed ( = 36) was positive for the presence of NoV or HAstV.

Nasal epithelium injury by chlorination products and other stressors predicts persistent sensitization to aeroallergens in young schoolchildren.

BACKGROUND: Allergic sensitization during childhood is a dynamic process with a substantial rate of remission. Factors influencing this process are largely unknown. METHODS: We conducted a two-year prospective study among 121 schoolchildren (mean age, 5.8 years; 64 boys). We measured urea, club cell protein (CC16), ß2-microglobulin and albumin in nasal lavage fluid (NALF) and IgE to cat, pollen or house dust mite (HDM) in nasal mucosa fluid. RESULTS: Odds of persistent sensitization to any aeroallergen increased across baseline ascending tertiles of urea-adjusted ß2-microglobulin or albumin and descending tertiles of albumin- or ß2-microglobulin-adjusted CC16 (P-trend = 0.006, 0.02, 0.044 and 0.006, respectively). Persistent HDM sensitization also increased with baseline descending tertiles of raw or urea-adjusted CC16 (both P-trend = 0.007). Such strong associations were not observed with new-onset or remitted sensitization to any aeroallergen or with raw NALF concentrations of urea, albumin or ß2-microglobulin. At baseline, house cleaning with bleach and chlorinated pool attendance emerged among the strongest and most consistent determinants of NALF biomarkers, being both associated with higher urea and lower CC16 in NALF. CONCLUSION: In young children, a defective nasal epithelium attributable to immaturity or stressors such as chlorination products is predictive of more persistent aeroallergen sensitization.

Comparative toxicological effects of two antifouling biocides on the marine diatom Chaetoceros lorenzianus: Damage and post-exposure recovery.

Antifouling biocides are commonly used in coastal electric power stations to prevent biofouling in their condenser cooling systems. However, the environmental impact of the chemical biocides is less understood than the thermal stress effects caused by the condenser effluents. In this study, Chaetoceros lorenzianus, a representative marine diatom, was used to analyse the toxicity of two antifouling biocides, chlorine and chlorine dioxide. The diatom cells were subjected to a range of concentrations of the biocides (from 0.05 to 2mg/L, as total residual oxidants, TRO) for contact time of 30min. They were analysed for viability, genotoxicity, chlorophyll a and cell density endpoints. The cells were affected at all concentrations of the biocides (0.05-2mg/L), showing dose-dependent decrease in viability and increase in DNA damage. The treated cells were later incubated in filtered seawater devoid of biocide to check for recovery. The cells were able to recover in terms of overall viability and DNA damage, when they had been initially treated with low concentrations of the biocides (0.5mg/L of Cl2 or 0.2mg/L of ClO2). Chlorophyll a analysis showed irreparable damage at all concentrations, while cell density showed increasing trend of reduction, if treated above 0.5mg/L of Cl2 and 0.2mg/L of ClO2. The data indicated that in C. lorenzianus, cumulative toxic effects and recovery potential of ClO2 up to 0.2mg/L were comparable with those of Cl2, up to 0.5mg/L concentration in terms of the studied endpoints. The results indicate that at the biocide levels currently being used at power stations, recovery of the organism is feasible upon return to ambient environment. Similar studies should be carried out on other planktonic and benthic organisms, which will be helpful in the formulation of future guidelines for discharge of upcoming antifouling biocides such as chlorine dioxide.

Chlorine dioxide enhances lipid peroxidation through inhibiting calcium-independent cellular PLA2 in larvae of the Indianmeal moth, Plodia interpunctella.

Polyunsaturated fatty acids usually undergo lipid peroxidation induced by reactive oxygen species (ROS). Calcium-independent cellular phospholipase A2 (iPLA2) can maintain fatty acid compositions in phospholipids depending on physiological conditions. An insect iPLA2 (Pi-iPLA2) was predicted from the transciptome of the Indianmeal moth, Plodia interpunctella. It encodes 835 amino acids. It possesses five ankyrin repeats in the N terminal and patatin lipase domain in the C terminal. Pi-iPLA2 was expressed in all developmental stages of the Indianmeal moth. In the larval stage, it was expressed in all tissues tested. RNA interference (RNAi) specific to Pi-iPLA2 was performed using specific double-stranded RNA (dsRNA). It resulted in almost 70% of reduction in gene expression. Under such RNAi condition, P. interpunctella exhibited significant accumulation of lipid peroxidation based on the amount of malondialdehyde. RNAi of Pi-PLA2 expression also impaired cellular immune response of P. interpunctella. Chlorine dioxide (ClO2), an insecticidal agent by generating ROS, increased lipid peroxidation in a dose-dependent manner. However, the addition of vitamin E (an antioxidant) reduced the formation of lipid peroxidation. ClO2 treatment significantly reduced expression of Pi-iPLA2 but increased lipid peroxidation in larval fat body of P. interpunctella. Furthermore, larvae treated with dsRNA specific to Pi-iPLA2 were significantly susceptible to ClO2 treatment. These results suggest that Pi-iPLA2 plays a crucial role in repairing damaged fatty acids from phospholipids. Our results also suggest that ClO2 can elevate lipid peroxidation through inhibiting Pi-iPLA2 expression in addition to direct ROS production.

Oxidative stress induced by chlorine dioxide as an insecticidal factor to the Indian meal moth, Plodia interpunctella.

A novel fumigant, chlorine dioxide (ClO2) is a commercial bleaching and disinfection agent. Recent study indicates its insecticidal activity. However, its mode of action to kill insects is yet to be understood. This study set up a hypothesis that an oxidative stress induced by ClO2 is a main factor to kill insects. The Indian meal moth, Plodia interpunctella, is a lepidopteran insect pest infesting various stored grains. Larvae of P. interpunctella were highly susceptible to ClO2 gas, which exhibited an acute toxicity. Physiological damages by ClO2 were observed in hemocytes. At high doses, the larvae of P. interpunctella suffered significant reduction of total hemocytes. At low doses, ClO2 impaired hemocyte behaviors. The cytotoxicity of ClO2 was further analyzed using two insect cell lines, where Sf9 cells were more susceptible to ClO2 than High Five cells. The cells treated with ClO2 produced reactive oxygen species (ROS). The produced ROS amounts increased with an increase of the treated ClO2 amount. However, the addition of an antioxidant, vitamin E, significantly attenuated the cytotoxicity of ClO2 in a dose-dependent manner. To support the oxidative stress induced by ClO2, two antioxidant genes (superoxide dismutase (SOD) and thioredoxin-peroxidase (Tpx)) were identified from P. interpunctella EST library using ortholog sequences of Bombyx mori. Both SOD and Tpx were expressed in larvae of P. interpunctella especially under oxidative stress induced by bacterial challenge. Exposure to ClO2 gas significantly induced the gene expression of both SOD and Tpx. RNA interference of SOD or Tpx using specific double stranded RNAs significantly enhanced the lethality of P. interpunctella to ClO2 gas treatment as well as to the bacterial challenge. These results suggest that ClO2 induces the production of insecticidal ROS, which results in a fatal oxidative stress in P. interpunctella.

Disinfection of indoor air microorganisms in stack room of university library using gaseous chlorine dioxide.

As with all indoor public spaces in Taiwan, the stack rooms in public libraries should meet the air quality guidelines laid down by the Taiwan Environmental Protection Administration. Accordingly, utilizing a university library in Taiwan for experimental purposes, this study investigates the efficiency of gaseous chlorine dioxide (ClO2) as a disinfection agent when applied using three different treatment modes, namely a single-daily disinfection mode (SIM), a twice-daily disinfection mode (TWM), and a triple-daily disinfection mode (TRM). For each treatment mode, the ClO2 is applied using an ultrasonic aerosol device and is performed both under natural lighting conditions and under artificial lighting conditions. The indoor air quality is evaluated before and after each treatment session by measuring the bioaerosol levels of bacteria and fungi. The results show that for all three disinfection modes, the application of ClO2 reduces the indoor bacteria and fungi concentrations to levels lower than those specified by the Taiwan EPA (i.e., bacteria <1500 CFU/m(3), fungi <1000 CFU/m(3)), irrespective of the lighting conditions under which the disinfection process is performed. For each disinfection mode, a better disinfection efficiency is obtained under natural lighting conditions since ClO2 readily decomposes under strong luminance levels. Among the three treatment modes, the disinfection efficiencies of the TWM and TRM modes are very similar under natural lighting conditions and are significantly better than that of the SIM mode. Thus, overall, the results suggest that the TWM treatment protocol represents the most cost-effective and efficient method for meeting the indoor air quality requirements of the Taiwan EPA.

The hapten-atopy hypothesis III: the potential role of airborne chemicals.

One explanation for the large increase in the prevalence of atopic disease in developed countries during the last 50 years is the 'hygiene hypothesis'. This proposes that a reduced exposure to pathogenic microorganisms at a key period(s) during development results in the maintenance or acquisition of an atopic phenotype. Alternatively, or additionally, we have postulated that increased exposure to chemicals generally, and to irritant/haptenic chemicals in particular, during critical windows of maternal pregnancy/early life have also contributed to changes in the prevalence of atopic disease. Having previously reviewed the potential roles of oral and cutaneous exposure to chemicals on the subsequent diagnosis of atopic disease, we here consider possible evidence of a role for exposure to airborne chemicals as a contributory factor in acquired susceptibility to atopic allergy. After controlling for known confounders, five specific maternal occupations during pregnancy have been implicated as being associated with subsequent atopic disease in the offspring. Each of these occupations is characterized by high and persistent exposure to airborne chemicals. High-level exposure to volatile organic compounds in the domestic environment, either during pregnancy or in early life, is also associated with development of childhood atopic disease. Similarly, sustained exposure to airborne chlorinated chemicals from swimming pools during childhood has been associated with the development of atopic allergy. A possible immunological basis for these associations is that exposure to certain airborne chemicals, even at low levels, can result in the delivery of 'danger' signals that, in turn, bias the immune response towards the selective induction or maintenance of preferential T helper 2-type immune responses consistent with the acquisition of allergic sensitization.

The use of chlorine dioxide for the inactivation of copepod zooplankton in drinking water treatment.

The presence of zooplankton in drinking water treatment system may cause a negative effect on the aesthetic value of drinking water and may also increase the threat to human health due to they being the carriers of bacteria. Very little research has been done on the effects of copepod inactivation and the mechanisms involved in this process. In a series of bench-scale experiments we used a response surface method to assess the sensitivity of copepod to inactivation when chlorine dioxide (ClO2) was used as a disinfectant. We also assessed the effects of the ClO2dosage, exposure time, organic matter concentration and temperature. Results indicated that the inactivation rate improved with increasing dosage, exposure time and temperature, whereas it decreased with increasing organic matter concentration. Copepod inactivation was more sensitive to the ClO2dose than that to the exposure time, while being maintained at the same Ct-value conditions. The activation energy at different temperatures revealed that the inactivation of copepods with ClO2was temperature-dependent. The presence of organic matter resulted in a lower available dose as well as a shorter available exposure time, which resulted in a decrease in inactivation efficiency.

[Endoscopic diagnosis of local chemical burn of mucous membranes of the stomach, induced with the purpose of simulation of gastric ulcer].

With the purpose of improvement of diagnosis of induced gastric ulcer were examined 11 patients who took aggressive agents for simulation of gastric ulcer and 33 patients who took pseudo-aggressive agents. Observables, conduced diagnosis of local chemical burn of mucous coat of stomach during initial 6 days after taking aggressive agents. Stages of ulcerous process, resulting from local chemical burn of mucous coat of stomach, coressponds to real gactric ulcer. Gelatin capsule using as a container for delivery of aggressive agents, melts in stomach in 5-6 minutes after taking. Independent from body position, mucous coat of greater curvature of the stomach is damaged. It is impossible to simulate duodenal bulb ulcer using the gelatine capsule or ball made of breadcrumb. The last method of delivery of aggressive agent can damage the small intestine because of uncontrollability of the place of breaking the ball.

Bisphenol A degradation by chlorine dioxide (ClO2) and S(IV)/ClO2 process: Mechanism, degradation pathways and toxicity assessment.

Recently, it has been reported that chlorine dioxide (ClO2) and (bi)sulfite/ClO2 showed excellent performance in micropollutant removal from water; however, the degradation mechanisms and application boundaries of the two system have not been identified. In this study, bisphenol A (BPA) was chosen as the target contaminant to give multiple comparisons of ClO2 and S(IV)/ClO2 process regarding the degradation performance of contaminant, generation of reactive species, transformation of products and toxicity variation. Both ClO2 and S(IV)/ClO2 can degrade BPA within 3 min. The BPA degradation mechanism was mainly based on direct oxidation in ClO2 process while it was attributed to radicals (especially SO4·-) generation in S(IV)/ClO2 process. Meanwhile, the effect of pH and coexisting substances (Cl-, Br-, HCO3- and HA) were evaluated. It was found that ClO2 preferred the neutral and alkaline condition and S(IV)/ClO2 preferred the acidic condition for BPA degradation. An unexpected speed-up of BPA degradation was observed in ClO2 process in the presence of Br-, HCO3- and HA. In addition, the intermediate products in BPA degradation were identified. Three exclusive products were found in ClO2 process, in which p-benzoquinone was considered to be the reason of the acute toxicity increase in ClO2 process.

Modulation of cytochrome P450 and induction of DNA damage in Cyprinus carpio exposed in situ to surface water treated with chlorine or alternative disinfectants in different seasons.

Epidemiological studies have shown an association between consumption of disinfected drinking water and adverse health outcomes. The chemicals used to disinfect water react with occurring organic matter and anthropogenic contaminants in the source water, resulting in the formation of disinfection by-products (DBPs). The observations that some DBPs are carcinogenic in animal models have raised public concern over the possible adverse health effects for humans. Here, the modulation of liver cytochrome P450-linked monooxygenases (MFO) and the genotoxic effects in erythrocytes of Cyprinus carpio fish exposed in situ to surface drinking water in the presence of disinfectants, such as sodium hypochlorite (NaClO), chlorine dioxide (ClO(2)) and peracetic acid (PAA), were investigated in winter and summer. A complex induction/suppression pattern of CYP-associated MFOs in winter was observed for all disinfectants. For example, a 3.4- to 15-fold increase was recorded of the CYP2B1/2-linked dealkylation of penthoxyresorufin with NaClO (10 days) and PAA (20 days). In contrast, ClO(2) generated the most notable inactivation, the CYP2E1-supported hydroxylation of p-nitrophenol being decreased up to 71% after 10 days' treatment. In summer, the degree of modulation was modest, with the exception of CYP3A1/2 and CYP1A1 supported MFOs (62% loss after 20 days PAA). The micronucleus (MN) induction in fish circulating erythrocytes was also analysed as an endpoint of genotoxic potential in the same fish population. Significant increases of MN induction were detected at the latest sampling time on fish exposed to surface water treated with chlorinate-disinfectants, both in winter (NaClO) and summer (NaClO and ClO(2)), while no effect was observed in fish exposed to PAA-treated water. These results show that water disinfection may be responsible for harmful outcomes in terms of MFO perturbation and DNA damage; if extrapolated to humans, they ultimately offer a possible rationale for the increased urinary cancer risk recorded in regular drinking water consumers.

Health effects associated with long-term occupational exposure of employees of a chlor-alkali plant to mercury.

This study aimed to evaluate possible health effects associated with long-term occupational exposure to low levels of mercury vapors. Forty-six subjects exposed to mercury and 65 healthy unexposed employees were studied. The subjects were administered a questionnaire on experienced symptoms and underwent clinical examinations as well as routine biochemical tests. Atmospheric and urinary concentrations of mercury were measured, too. Environmental concentrations of mercury were estimated to be 3.97 ± 6.28 µg/m(3) and urinary concentrations of mercury in exposed and referent groups were 34.30 ± 26.77 and 10.15 ± 3.82 µg/dm(3), respectively. Additionally, symptoms such as somatic fatigue, anorexia, loss of memory, erethism, blurred vision and teeth problems were significantly more common among exposed individuals. These observations indicate that occupational exposure to mercury vapors, even at low levels, is likely to be associated with neurological and psychological symptoms.

Inactivation of Escherichia coli O157:H7 on radish seeds by sequential treatments with chlorine dioxide, drying, and dry heat without loss of seed viability.

We developed and validated a treatment to inactivate Escherichia coli O157:H7 on radish seeds without decreasing seed viability. Treatments with aqueous ClO(2) followed by drying and dry-heat treatments were evaluated for efficacy to inactivate the pathogen. Conditions to dry radish seeds after treatment with water (control) or ClO(2) were established. When treated seeds with high water activity (a(w)) (>0.99) were stored at 45°C and 23% relative humidity (RH), the a(w) decreased to <0.30 within 24 h. Drying high-a(w) seeds before exposing them to dry-heat treatment (≥60°C) was essential to preserve seed viability. The germination rate of radish seeds which had been immersed in water for 5 min, dried at 45°C and 23% RH for 24 h, and heated at 70°C for 48 h or at 80°C for 24 h was not significantly decreased (P ≤ 0.05) compared to that of untreated radish seeds. Sequential treatments with ClO(2) (500 µg/ml, 5 min), drying (45°C, 23% RH, 24 h), and dry heating (70°C, 23% RH, 48 h) eliminated E. coli O157:H7 (5.9 log CFU/g) on radish seeds and, consequently, sprouts produced from them without decreasing the germination rate. These sequential treatments are recommended for application to radish seeds intended for sprout production.

Reduction of Escherichia coli O157:H7 on radish seeds by sequential application of aqueous chlorine dioxide and dry-heat treatment.

AIMS: To assess the effectiveness of sequential treatments of radish seeds with aqueous chlorine dioxide (ClO(2) ) and dry heat in reducing the number of Escherichia coli O157:H7. METHODS AND RESULTS: Radish seeds containing E. coli O157:H7 at 5.5 log CFU g(-1) were treated with 500 µg ml(-1) ClO(2) for 5 min and subsequently heated at 60 °C and 23% relative humidity for up to 48 h. Escherichia coli O157:H7 decreased by more than 4.8 log CFU g(-1) after 12 h dry-heat treatment. The pathogen was inactivated after 48 h dry-heat treatment, but the germination rate of treated seeds was substantially reduced from 91.2 ± 5.0% to 68.7 ± 12.3%. CONCLUSIONS: Escherichia coli O157:H7 on radish seeds can be effectively reduced by sequential treatments with ClO(2) and dry heat. To eliminate E. coli O157:H7 on radish seeds without decreasing the germination rate, partial drying of seeds at ambient temperature before dry-heat treatment should be investigated, and conditions for drying and dry-heat treatment should be optimized. SIGNIFICANCE AND IMPACT OF THE STUDY: This study showed that sequential treatment with ClO(2) and dry-heat was effective in inactivating large numbers of E. coli O157:H7 on radish seeds. These findings will be useful when developing sanitizing strategies for seeds without compromising germination rates.

Chlorine dioxide inactivation of bacterial threat agents.

AIMS: To evaluate the efficacy of chlorine dioxide (ClO(2)) against seven species of bacterial threat (BT) agents in water. METHODS AND RESULTS: Two strains of Bacillus anthracis spores, Yersinia pestis, Francisella tularensis, Burkholderia pseudomallei, Burkholderia mallei and Brucella species were each inoculated into a ClO(2) solution with an initial concentration of 2.0 (spores only) and 0.25 mg l(-1) (all other bacteria) at pH 7 or 8, 5 or 25°C. At 0.25 mg l(-1) in potable water, six species were inactivated by at least three orders of magnitude within 10 min. Bacillus anthracis spores required up to 7 h at 5°C for the same inactivation with 2.0 mg l(-1) ClO(2). CONCLUSIONS: Typical ClO(2) doses used in water treatment facilities would be effective against all bacteria tested except B. anthracis spores that would require up to 7 h with the largest allowable dose of 2 mg l(-1) ClO(2). Other water treatment processes may be required in addition to ClO(2) disinfection for effective spore removal or inactivation. SIGNIFICANCE AND IMPACT OF STUDY: The data obtained from this study provide valuable information for water treatment facilities and public health officials in the event that a potable water supply is contaminated with these BT agents.

Effect of chlorine dioxide gas on Salmonella enterica inoculated on navel orange surfaces and its impact on the quality attributes of treated oranges.

Microorganisms, including pathogens of public health significance, have been shown to contaminate orange juice during the mechanical extraction of juice. The problem gets exacerbated when washed oranges have high initial microbial load, due to an insufficient postharvest treatment. The objective of this study was to investigate the reduction of Salmonella enterica on orange surfaces using ClO2 gas treatments to achieve a 5 log reduction, consistent with the recommendations of the U.S. Department of Agriculture-National Advisory Committee on Microbiological Criteria for Foods. A mixed culture of four Salmonella strains, isolated from previous orange juice outbreaks, was spot inoculated onto orange skin surface areas. The oranges were then treated with 0.1, 0.3, and 0.5 mg/L ClO2 gas for 2-14 minutes at 22°C and 90%-95% relative humidity. Surviving bacteria on treated areas were recovered and enumerated over treatment time on a nonselective medium, tryptic soy agar, followed by culturing onto a selective medium, xylose lysine deoxycholate agar. A >5 log reduction of Salmonella per sample of orange surface was observed with 0.1 and 0.3 mg/L ClO2 gas treatments at 14 minutes and a similar log reduction was observed at 0.5 mg/L ClO2 gas at 10 minutes. This result demonstrates that the treatment of oranges with ClO2 gas is a promising technology that could be successfully employed for the treatment of whole oranges to reduce the risk of Salmonella outbreaks in orange juice.

Intercalating, cytotoxic, antitumour activity of 8-chloro and 4-morpholinopyrimido [4',5':4,5]thieno(2,3-b)quinolines.

Circular dichroism, hydrodynamic methods, absorbance and fluorescence titration's were employed to study the interaction of 8-chloropyrimido[4',5':4,5]thieno(2,3-b)quinolin-4(3H)-one (chloro-PTQ) and 4-morpholinopyrimido[4',5':4,5]thieno(2,3-b)quinoline (morpholino-PTQ) with DNA. The association constant of chloro-PTQ and morpholino-PTQ were of the order of 10(5) and 10(6) M(-1). The fluorescence properties at ionic strength of 10mM are best fit by the neighbor exclusion model, with Ki of 0.3 x 10(4) M(-1) to 3.2 x 10(6) M(-1). CD spectra indicate that stacking of these compounds with DNA induces strong helicity in the usually disordered structure of the double strand. Viscosity experiments with sonicated rod like DNA fragments, produced a calculated length of 2.4A/bound of chloro/morpholino-PTQ molecule. The binding of chloro/morpholino-PTQ to DNA increased the melting temperature by about 1.5-7.0 degrees C. The cytotoxicity of these compounds on K-562, HL-60, Colo-205 and B16F10 melanoma are quite similar and IC(50) was in the range of 1.1-8muM. The anticancer efficacy against B16F10 melanoma has provided evidence of major anticancer activity for morpholino-PTQ. Single or multiple i.p. doses of compounds showed high level of activity against the subcutaneous (s.c.) grafted B16 melanoma with a significant increase in life span (161% and 272%). The aim of this study was to analyze the physicochemical properties of the chloro/morpholino-PTQ in an attempt to understand their superior biological activity. This research offers a new intercalation functional group to DNA targeted drug design.