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PubMed2005

Modulating effects of humic acids on genotoxicity induced by water disinfectants in Cyprinus carpio.

The use of chlorinated disinfectants during drinking-water production has been shown to generate halogenated compounds as a result of interactions of humic acids with chlorine. Such chlorinated by-products have been shown to induce genotoxic effects and consumption of chlorinated drinking-water has been correlated with increased risk for cancer induction in human populations. The aim of this work was to test the potential genotoxic effects on circulating erythrocytes of the fish Cyprinus carpio exposed in vivo to well-waters disinfected with sodium hypochlorite (NaClO), chlorine dioxide (ClO2) or peracetic acid (CH3COO2H, PAA), in the absence or presence of standard humic acids (HA). The effects were measured by use of the micronucleus (MN) and the single-cell gel electrophoresis (Comet) assays at different sampling times after a 3-day exposure period. The exposure to chlorine disinfectants without the addition of HA produced a clear toxic effect. Significant cytogenetic damage (i.e. MN induction) was detected in fish populations exposed to both NaClO and ClO2 with humic acids. In the Comet assay, a significant decrease of DNA migration was observed in erythrocytes of specimens after exposure to NaClO-disinfected water without HA. No effects were observed in any other experimental condition.

Animals↗
PubMed2006

Optimal bulking agent particle size and usage for heat retention and disinfection in domestic wastewater sludge composting.

Composting of two types of sludge produced in wastewater treatment plants, raw sludge (RS) and anaerobically digested sludge (ADS), has been systematically studied by means of the experimental design technique. The results have been analyzed using a full factorial experimental design in order to determine the optimal conditions for composting such sludges in terms of bulking agent particle size and bulking agent:sludge volumetric ratio, two of the key parameters to ensure an optimal performance of the composting process. The objective function selected was a simulated death kinetics of Salmonella, which was chosen as a model pathogen microorganism to represent the disinfection of the material. For both types of sludge, optimal values were found at 5mm bulking agent particle size and 1:1 bulking agent:sludge volumetric ratio when a Gaussian function was fitted to the experimental data. Pilot scale experiments using optimal values obtained were successfully undertaken and confirmed a full disinfection of the sludge by means of the composting process. A mathematical model to simulate the disinfection performance of a composting material is presented. The model can be applied to simulate the disinfection performance of a given pathogen.

Disinfection↗
PubMed2005

Disinfection of Burkholderia pseudomallei in potable water.

The effect of chlorine, monochloramine and UV disinfection on the water-borne pathogen Burkholderia pseudomallei was assessed. Persistence of B. pseudomallei was verified by MPN involving a one-step recovery procedure. Chlorine proved the most effective disinfectant with a 99.99% reduction of a 10(6) CFU/mL pure bacterial culture followed by 99.9% reduction by monochloramine and 99% reduction by UV. Co-culture of B. pseudomallei with Acanthamoeba astronyxis was found to greatly enhance survival of B. pseudomallei in the presence of all disinfecting agents tested. For example, when amoebae were present 100 times more monochloramine was required to maintain the disinfectant efficacy. Given the results obtained from these co-culture experiments, more research is needed to investigate the role of amoeba and biofilms in survival of B. pseudomallei in potable water.

Acanthamoeba↗
PubMed2005

Pipeline materials modify the effectiveness of disinfectants in drinking water distribution systems.

We studied how pipe material can modify the effectiveness of UV- and chlorine disinfection in drinking water and biofilms. This study was done with two pipe materials: copper and composite plastic (polyethylene, PE) in a pilot scale water distribution network. UV-disinfection decreased viable bacterial numbers in the pilot waterworks and outlet water of pipes on average by 79%, but in biofilms its disinfecting effect was minor. Chlorine decreased effectively the microbial numbers in water and biofilms of PE pipes. In outlet water from copper pipes, the effect of chlorination was weaker; microbial numbers increased back to the level before chlorination within a few days. In the biofilms present in the copper pipes, chlorine decreased microbial numbers only in front of the pipeline. One reason for weaker efficiency of chlorine in copper pipes was that its concentration declined more rapidly in the copper pipes than in the PE pipes. These results means that copper pipes may require a higher chlorine dosage than plastic pipes to achieve effective disinfection of the pipes.

Biofilms↗
PubMed2005

Feasibility of the silver-UV process for drinking water disinfection.

A synergistic effect between cationic silver and UV radiation (silver-UV disinfection) has been observed that can appreciably enhance inactivation of viruses. The purpose of this work was to assess the feasibility of this technique for drinking water disinfection and evaluate the effects of selected impurities, found in fresh water, and common parameters on inactivation of the coliphage MS-2 with the silver-UV process. Turbidity (kaolin), calcium hardness, carbonate alkalinity, and pH did not significantly degrade inactivation. Inactivation was reduced in the presence of chloride, at concentrations greater than 30 mg/L, and in water samples with UV-254 absorbance values greater than ca. 0.1 cm(-1). Inactivation of MS-2 with silver-UV disinfection was also reduced at high phosphate concentrations (above ca. 5 mM). Silver-UV inactivation of MS-2 increased with increases in temperature between 10 and 20 degrees C. Silver-UV inactivation of MS-2 was increased by greater than 1-log over UV alone, in two untreated fresh water sources, which indicates that silver-UV may be a viable treatment technology. An assessment of operation and management costs suggests that an increase in inactivation of MS-2 with silver-UV disinfection could be economically beneficial.

Chlorides↗
PubMed2006

Disinfection of swine wastewater using chlorine, ultraviolet light and ozone.

Veterinary antibiotics are widely used at concentrated animal feeding operations (CAFOs) to prevent disease and promote growth of livestock. However, the majority of antibiotics are excreted from animals in urine, feces, and manure. Consequently, the lagoons used to store these wastes can act as reservoirs of antibiotics and antibiotic-resistant bacteria. There is currently no regulation or control of these systems to prevent the spread of these bacteria and their genes for antibiotic resistance into other environments. This study was conducted to determine the disinfection potential of chlorine, ultraviolet light and ozone against swine lagoon bacteria. Results indicate that a chlorine dose of 30 mg/L could achieve a 2.2-3.4 log bacteria reduction in lagoon samples. However, increasing the dose of chlorine did not significantly enhance the disinfection activity due to the presence of chlorine-resistant bacteria. The chlorine resistant bacteria were identified to be closely related to Bacillus subtilis and Bacillus licheniformis. A significant percentage of lagoon bacteria were not susceptible to the four selected antibiotics: chlortetracycline, lincomycin, sulfamethazine and tetracycline (TET). However, the presence of both chlorine and TET could inactivate all bacteria in one lagoon sample. The disinfection potential of UV irradiation and ozone was also examined. Ultraviolet light was an effective bacterial disinfectant, but was unlikely to be economically viable due to its high energy requirements. At an ozone dose of 100 mg/L, the bacteria inactivation efficiency could reach 3.3-3.9 log.

Animal Husbandry↗
PubMed2001

The disinfection of contact lenses contaminated with adenovirus.

PURPOSE: We compared the efficacy of different contact lens disinfection systems to eliminate adenovirus. METHODS: Laboratory study evaluating the elimination of adenoviral ocular isolates by contact lens disinfection systems. Hard (gas permeable) and soft contact lenses were contaminated with adenovirus serotypes 8 and 19, and then they were disinfected with chemical, hydrogen peroxide, and heat sterilization systems. The survival of the adenovirus was determined by the shell vial technique. RESULTS: Adenovirus survived chemical and hydrogen peroxide disinfection but not heat sterilization. CONCLUSION: Because heat sterilization is not readily available to sterilize adenovirus contaminated contact lenses, it may be prudent for patients with adenoviral keratoconjunctivitis to dispose of unclean contact lenses.

Adenoviruses, Human↗
PubMed2002

Bacteria-free rinse water for endoscope disinfection.

BACKGROUND: Most breaches of endoscope disinfection result from inadequate manual cleaning or improper use of disinfectants. This is a description of how a quality assurance program identified rinse water as a source of bacterial contamination and how it facilitated the introduction of a novel means of delivering rinse water of high purity. METHODS: Between 1996 and 2001, weekly samples were obtained from accessory and suction channels of endoscopes as well as the internal chambers of automated washing machines. Samples were processed for routine bacterial and mycobacterial culture. RESULTS: Bacteria were isolated in 8.7% of samples collected between 1996 and 1998. Of 36 positive samples, 20 (54%) were Pseudomonas sp. Analysis of rinse water from pipework downstream from filters demonstrated high growth of Pseudomonas sp, suggesting biofilm within piping was contaminating rinse water. A system of hot water flushing of pipework was developed that maintains a temperature above 60 degrees C for 60 minutes on a daily basis. This resulted in a consistently low level of bacterial contamination. CONCLUSION: This report demonstrates the value of a quality assurance program for endoscope disinfection and shows how rinse water may contaminate disinfected endoscopes. A system of hot water purging of the rinse water delivery system markedly reduces this contamination.

Bacteria↗
PubMed2004

Bacteriologic testing of endoscopes after high-level disinfection.

BACKGROUND: There are no definitive data available concerning microbiologic safety of prolonged endoscope storage after reprocessing and disinfection. This study evaluated the durability of high-level disinfection of endoscopes stored in a dust-proof cabinet for 5 days. METHODS: Three different types of endoscopes (upper endoscopes, duodenoscopes, colonoscopes) were tested. After completion of the endoscopic procedure, endoscopes were subjected to an initial decontamination, followed by manual cleaning with the endoscope immersed in detergent. The endoscopes then were placed in an automatic reprocessor that provides high-level disinfection. They then were stored by hanging in a dust-proof cabinet. Bacteriologic samples were obtained from the surface of the endoscopes, the openings for the piston valves, and the accessory channel daily for 5 days, and by flush-through (combined with brushing) from the accessory channels after 5 days of storage. Samples were cultured for all types of aerobic and anaerobic bacteria, including bacterial spores, and for Candida species. RESULTS: For all assays, all endoscopes were bacteria-free immediately after high-level disinfection. Only 4 assays (of 135) were positive during the subsequent 5-day assessment (skin bacteria cultured from endoscope surfaces). All flush-through samples were sterile. CONCLUSIONS: When endoscope reprocessing guidelines are strictly observed and endoscopes are stored in appropriate cabinets for up to 5 days, reprocessing before use may not be necessary.

Disinfection↗
PubMed1998

Risk of contamination of sterile biopsy forceps in disinfected endoscopes.

BACKGROUND: Previous studies have shown that pathogens may persist within bacterial biofilms in endoscope accessory channels despite high-level disinfection. Breaching the gastrointestinal mucosa with biopsy forceps contaminated at time of passage has the potential to cause cross-infection between patients. METHODS: We studied contamination risk of sterilized biopsy forceps passed through endoscopes after high-level disinfection. For each trial, five video colonoscopes, duodenoscopes, and gastroscopes were used. All endoscopes had been previously processed and stored for 10 or more hours. Sterile biopsy forceps were inserted and retrieved followed by vortexing the tips in 15 mL of soy broth. Under a laminar flow hood, the broth was filtered through a 0.2 microm millipore membrane and plated. Because of minimal bacterial growth resulting from the above, soy broth (> 20 mL) was flushed through two video colonoscopes, duodenoscopes, and gastroscopes on two occasions and collected. The effluent was plated using a sample of 0.1 mL dilution. The remaining suspension was passed through a millipore filter, and the filter was cultured. All cultures were incubated more than 48 hours. RESULTS: Biopsy forceps underwent a total of 24 anaerobic and 75 aerobic cultures. Microbacterial growth occurred on 17 plates: 7 from gastroscopes, 5 from colonoscopes, and 5 from duodenoscopes. Fifteen plates grew staphylococcus for a total of 21 colonies, 1 plate grew 1 colony of propionibacter, 2 plates grew diphtheroids for a total of 4 colonies, and 1 plate grew a single colony of lactobacillus. Cultures from soy broth flushed through the various endoscopes grew on 5 plates: 3 from gastroscopes and 2 from duodenoscopes grew a total of 8 colonies of staphylococcus. CONCLUSIONS: With proper cleaning technique, a 20-minute soak in 2% glutaraldehyde is effective in disinfecting endoscopes. Although current procedures for endoscope disinfection remain imperfect, we found that in this clinical setting, infection of pathogenic gastrointestinal flora is unlikely when using sterile biopsy forceps.

Bacterial Infections↗
PubMed1999

Effect of disinfectant agents on dimensional stability of elastomeric impression materials.

STATEMENT OF PROBLEM: Difficulties in sterilizing impressions by traditional methods have led to chemical disinfection as an alternative, and some studies have shown that disinfectants may adversely affect impressions. PURPOSE: This study investigated the effect of disinfection methods on the dimensional stability of 6 elastomeric materials. MATERIAL AND METHODS: Impression materials were submitted to the following treatments: immersion in 5.25% sodium hypochlorite solution for 10 minutes, immersion in 2% glutaraldehyde solution for 30 minutes, and no immersion (control). After treatments, impressions were poured, and respective stone casts were measured with a Nikon Profile projector and compared with the master model. RESULTS: The elastomeric materials had different reproduction capacities, and the disinfecting treatments did not differ from the control.

Calcium Sulfate↗
PubMed2001

Determination of N-chloramines in As-samra chlorinated wastewater and their effect on the disinfection process.

Chlorine is the most widely used disinfectant of wastewater due to its capacity to inactivate most pathogenic microorganisms quickly. However, chlorine reacts with natural organic compounds present in wastewater to produce some undesirable organic byproducts. One such class of compounds is the nitrogenous compounds. The reaction between chlorine and compounds containing a nitrogen atom with one or more hydrogen atoms attached to it will form chloramines which have lower disinfection efficiency. Eighty percent of the wastewater generated in Jordan is treated at the Khirbet As-Samra wastewater treatment plant for eventual use in agriculture. In this study efficiency of chlorination was studied by collecting samples from the effluent of the treatment plant. The yield concentration of N-chloramines upon chlorination was determined. Efficiency of disinfection process as a function of contact time, concentration of chlorine dosage, concentration of nitrogenous compound and pH were studied. In this study, it has been found that at a chlorine dosage of 15 mg/L and contact time of 15 min, the percentage total coliform kill in As-samra wastewater sample was 100%. After addition of histidine, glycine and phenylalanine (15 mg/L in each case) to the wastewater sample, the percentage of total coliform kill dropped to 58, 78 and 79% respectively. When chlorine dosage was increased to 24 mg/L the percentage total coliform kill reached 96, 99 and 100% in wastewater samples treated with 5 mg/L histidine, glycine and phenylalanine, respectively. The percentage total coliform kill dropped to zero in wastewater samples treated with histidine, glycine and phenylalanine at a concentration of 30 mg/L each. This work supports the theory that amino acids and ammonia preferentially react with chlorine to form N-chloramine which significantly reduces the disinfection efficiency of the chlorination process.

Ammonium Chloride↗
PubMed2003

Impact of hydrogen peroxide on nitrite formation during UV disinfection.

One concern with UV disinfection of water is the production of nitrite when polychromatic UV sources are utilized. Based on previous work, it was hypothesized that a small addition of hydrogen peroxide (H(2)O(2)) may be useful in controlling nitrite during UV disinfection. However, it was found that H(2)O(2) addition (5 or 10mg/L) during polychromatic UV irradiation of drinking water at doses used for disinfection significantly increases the levels of nitrite produced relative to solutions without H(2)O(2). Enhancement rates ranged from approximately 15% to 40% depending upon pH and H(2)O(2) concentration; the relative increase in the NO(2)(-) yield was greater at pH 6.5 than at pH 8.3. The observed effects are tentatively ascribed to a combination of enhanced superoxide production and increased hydroxyl radical scavenging when H(2)O(2) is added. These results indicate that H(2)O(2) cannot be used to control nitrite production during UV disinfection and that enhanced nitrite formation will occur if H(2)O(2) is added during UV water treatment to achieve advanced oxidation of contaminants.

Disinfection↗
PubMed2000

The photocatalytic disinfection of urban waste waters.

In this paper we present the results of the photocatalytic disinfection of urban waste water. Two microbial groups, total coliforms and Streptococcus faecalis, have been used as indexes to test disinfection efficiencies. Different experimental parameters have been checked, such as the effect of TiO2, solar or UV-lamp light and pH. Disinfection of water samples has been achieved employing both UV-lamp and solar light in agreement with data shown by other authors. The higher disinfection rates obtained employing an UV-lamp may be explained by the stronger incident light intensity. Nevertheless no consistent differences have been found between TiO2-photocatalysis and direct solar or UV-lamp light irradiation at natural sample pH (7.8). At pH 5 the presence of TiO2 increases the relative inactivation rate compared with the absence of the catalyst. After the photocatalytic bacterial inactivation, the later bacterial reappearance was checked for total coliforms at natural pH and pH 5, with and without TiO2. Two h after the photocatalytic treatment, CFU increment was almost nill. But 24 and 48 h later an important bacterial CFU increment was observed. This CFU increment is slower after irradiation with TiO2 at pH 5 in non-air-purged samples.

Catalysis↗
PubMed1981

Disinfection in upper-digestive-tract endoscopy in Britain.

A contaminated endoscope may infect patients at upper-gastrointestinal-tract endoscopy (oesophago-gastro-duodenoscopy and endoscopic cholangio-pancreatography) either by the transmission of infection from one patient to another or by inoculation of potentially pathogenic bacteria which have multiplied in the instrument and ancillary equipment during storage. These dangers can be eliminated by careful disinfection with glutaraldehyde, other aldehyde disinfectants, or povidone-iodine. Few centres in Britain are using an effective disinfection procedure and of those who have used glutaraldehyde (the most widely employed) 37% have had serious problems with staff sensitivity. A quick, effective, and safe method for the disinfection of fibreoptic instruments is urgently needed.

Cross Infection↗
PubMed1986

Safe disinfection of contact lenses after contamination with HTLV-III.

The human T-lymphotropic retrovirus type III (HTLV-III), the etiological agent of AIDS, has recently been detected in tears, cornea, and conjunctiva, raising the possibility of transmission of HTLV-III via contact lens trial sets used in routine fitting. We evaluated the ability of several contact lens cleaning solutions, with or without conditioning or disinfecting solutions, to disinfect contact lenses experimentally contaminated with HTLV-III. Following attempted disinfection, the lenses were cultured for residual HTLV-III on Hg cells for 28 days. Cultures without characteristic cytopathic effects, reverse transcriptase activity, and HTLV-III-specific antigen expression were considered negative. We found that all commercially available cleaning solutions tested were able to disinfect contact lenses exposed to HTLV-III.

Contact Lenses↗
PubMed2000

Risk factors for Salmonella persistence after cleansing and disinfection in French broiler-chicken houses.

A prospective survey was carried out in 86 broiler houses in western France to identify risk factors for Salmonella persistence in French broiler houses. The Salmonella status of the house after cleansing and disinfection, was assessed from gauze-swab samples taken from the walls, feeders, ventilation system and bedding (analysed with classical bacteriological methods). Thirty three (38%) houses had at least one contaminated sample and were classified as Salmonella-contaminated houses in the logistic regression. The absence of a terminal disinfection and a disinfection procedure performed by the farm staff rather than a contractor were positively related to the Salmonella contamination of the house after cleansing and disinfection. The risk for Salmonella persistence after decontamination was increased if rodents were observed by the farmer, if a large part of the access area to the house was accessible to trucks, and if a disease leading to a treatment occurred in the previous flock.

Animals↗
PubMed2003

The microbial ecology of processing equipment in different fish industries-analysis of the microflora during processing and following cleaning and disinfection.

The microflora adhering to the processing equipment during production and after cleaning and disinfecting procedures was identified in four different processing plants. A total of 1009 microorganisms was isolated from various-agar plates and identified. A stepwise procedure using simple phenotypic tests was used to identify the isolates and proved a fast way to group a large collection of microorganisms. Pseudomonas, Neisseriaceae, Enterobactericeae, Coryneform, Acinetobacter and lactic acid bacteria dominated the microflora of cold-smoked salmon plants, whereas the microflora in a plant processing semi-preserved herring consisted of Pseudomonas, Alcaligenes and Enterobactericeae. Psychrobacter, Staphylococcus and yeasts were found in a caviar processing plant. Overall, many microorganisms that are often isolated from fish were also isolated from the fish processing plants. However, some selection depending on processing parameters occurred, since halo- and osmo-tolerant organisms dominated in the caviar processing. After cleaning and disinfection, yeasts, Pseudomonas, Neisseriaceae and Alcaligenes remained in smokehouses, yeasts and Pseudomonas in the herring plant and Pseudomonas, Staphylococcus and yeasts in the caviar plant. The dominant adhering organisms after cleaning and disinfection were pseudomonads and yeasts independently of the microflora during processing. Knowledge of the adhering microflora is essential in the Good Hygienic Practises programme of food processing plants, as the development and design of improved cleaning and disinfecting procedures should target the microorganisms persisting and potentially contaminating the product.

Animals↗