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One- and two-step hydrogen peroxide contact lens disinfection solutions against Acanthamoeba: how effective are they?

PURPOSE: Effective contact lens disinfection solutions are important to keep the storage case free of acanthamoebae and thus prevent an infection of the eye. The aim of our study was to evaluate the effectivity of two new one-step hydrogen peroxide disinfecting solutions against Acanthamoeba spp. and compare it to the effectivity of other commercially available systems. METHODS: Nine one-step 3% hydrogen peroxide systems including the new systems Silver Sept (platinum and silver disk for intensifying disinfection) and Blue Vision (newly composed catalytic tablet) and 2 two-step systems (0.6 and 3.0% H(2)O(2)) were tested for their effectivity against cysts of two Acanthamoeba keratitis isolates at different concentrations. RESULTS: After a soaking time of 8 h (overnight soaking of contact lenses) the 2 two-step systems completely destroyed the cysts of both Acanthamoeba strains, even at the highest concentration of cysts tested. The nine tested one-step systems showed weaker effects. The new Blue Vision system was able to eradicate the cysts of one strain at the low concentration of cysts. CONCLUSIONS: One-step hydrogen peroxide systems do not have sufficient effects on Acanthamoeba cysts and therefore may not protect the contact lens user from a possible infection of the eye. Further development of tablets like the ones used in the Blue Vision system may result in better cysticidal effects for one-step systems.

Acanthamoeba↗

Exposure assessment in epidemiologic studies of adverse pregnancy outcomes and disinfection byproducts.

A major challenge in studies that examine the association between disinfection byproducts in drinking water and pregnancy outcomes is the accurate representation of a subject's exposure. We used household water samples and questionnaire information on water-use behavior to examine several aspects of exposure assessment: (i) the distribution and correlation of specific disinfection byproducts, (ii) spatial distribution system and temporal variation in byproduct levels, and (iii) the contribution of individual water-use behavior. The level of specific trihalomethanes (THMs) and haloacetic acids (HAAs) was determined for 360 household water samples in Eastern Ontario and Nova Scotia. Subjects were interviewed regarding tap water ingestion and showering and bathing practices. In both provinces, total THMs correlated highly with chloroform (correlation coefficient (r) >0.95) and less so with total HAAs (r = 0.74 in Nova Scotia and r = 0.52 in Ontario). The correlation between total THMs and bromodichloromethane was high in Nova Scotia (r = 0.63), but low in Ontario (r = 0.26). The correlation was between THM level in individual household samples, and the mean THM level during the same time period from several distribution system samples was 0.63, while a higher correlation in THM level was observed for samples taken at the same location 1 year apart (r = 0.87). A correlation of 0.73 was found between household THM level and a total exposure measure incorporating ingestion, showering, and bathing behaviors. These results point to the importance of: measurement of different classes of byproducts; household rather than distribution system sampling; and, incorporation of subject behaviors in exposure assessment in epidemiologic studies of disinfection byproducts and adverse pregnancy outcomes.

Acetates↗

Characterization and quantification of bacterial pathogens and indicator organisms in household kitchens with and without the use of a disinfectant cleaner.

This two year study evaluated the prevalence of indicator bacteria and specific pathogens in 10 'normal' kitchens in the United States. In Phase I, none of the kitchens was cleaned with an antimicrobial cleaner or disinfectant. Eight locations within the kitchens were monitored for: total heterotrophs, staphylococci, Pseudomonas, total coliforms and faecal coliforms. Almost all locations at all households exhibited contamination, with the sink and sponge samples exhibiting large bacterial concentrations. The faecal coliform concentrations in sink and sponge samples were very high, with 63 and 67% of all samples being positive, respectively. Escherichia coli was detected in 16.7% of all sink surfaces and 33.3% of all sponges. Salmonella was detected once and Campylobacter, on two occasions. In a second phase, households were provided with an antimicrobial disinfectant cleaner which families were encouraged to use but not forced to do so; in some cases, the product was used infrequently or not at all. This regimen did not demonstrate any consistent reduction in the incidence of bacterial contamination. By contrast, in the final phase of the study where disinfectant use was targeted for surfaces soon after contamination with foods or hands, the incidence of contamination decreased dramatically. These data show that normal kitchens can easily be contaminated with a variety of bacterial contaminants including faecal coliforms, E. coli, Salmonella and Campylobacter. Irregular use, or not using antimicrobial agents, is unlikely to reduce the risk of these infectious agents. By contrast, targeted use is likely to reduce the incidence of bacterial contaminants.

Bacteria↗

Microbial disinfection capacity of municipal solid waste (MSW) composting.

The disinfection capacity of a municipal solid waste (MSW) composting plant (Siloda) has been evaluated. In spring and summer, MSW was followed during the composting process from raw material to mature compost and long-term storage (1 year). Ascaris eggs, Salmonella, Shigella, total streptococci, faecal streptococci, total coliforms, faecal coliforms and Escherichia coli were studied. Disinfection was successful in terms of a decrease in faecal contamination indicators and disappearance of faecal pathogens. Faecal coliform concentration in raw waste reached 2.1 x 10(8) cfu g-1 dry weight in spring (CI 95%:5.2 x 10(7)-3.4 x 10(8)) and 7.2 x 10(8) cfu g-1 dry weight (1 x 10(8)-1.7 x 10(9)) in summer, and fell to less than 100 cfu g-1 dry weight within 20 d. Faecal streptococci concentrations reached 8.7 x 10(8) cfu g-1 dry weight (3.7 x 10(8)-1.3 x 10(9)) in spring and 2.0 x 10(9)cfu g-1 dry weight (5.6 x 10(8)-3.4 x 10(9)) in summer, and fell to 8.7 x 10(4) cfu g-1 dry weight (6.9 x 10(4)-1.0 x 10(5)). No seasonal pattern of contamination, mainly of animal origin, was observed. Microbiological quality of finished compost depends on the storage conditions. Therefore, the storage stage should be viewed as part of the composting process. Monitoring disinfection capacity of MSW composting needs to combine several microbial populations.

Disinfection↗

The use of multiple indices of physiological activity to access viability in chlorine disinfected Escherichia coli O157:H7.

A suite of fluorescent intracellular stains and probes was used, in conjunction with viable plate counts, to assess the effect of chlorine disinfection on membrane potential (rhodamine 123; Rh123 and bis-(1,3-dibutylbarbituric acid) trimethine oxonol; DiBAC4(3)), membrane integrity (LIVE/DEAD BacLight kit), respiratory activity (5-cyano-2,3-ditolyl tetrazolium chloride; CTC) and substrate responsiveness (direct viable counts; DVC) in the commensal pathogen Escherichia coli O157:H7. After a 5 min exposure to the disinfectant, physiological indices were affected in the following order: viable plate counts > substrate responsiveness > membrane potential > respiratory activity > membrane integrity. In situ assessment of physiological activity by examining multiple targets, as demonstrated in this study, permits a more comprehensive determination of the site and extent of injury in bacterial cells following sublethal disinfection with chlorine. This approach to assessing altered bacterial physiology has application in various fields where detection of stressed bacteria is of interest.

Chlorine↗

A comparison of the bactericidal efficacy of 18 disinfectants used in the food industry against Escherichia coli O157:H7 and Pseudomonas aeruginosa at 10 and 20 degrees C.

A number of proprietary disinfectant products (18) used in the food industry were tested for their bactericidal efficacy against Pseudomonas aeruginosa and Escherichia coli O157:H7 at 20 and 10 degrees C according to the BS EN 1276 (1997) quantitative suspension test for the evaluation of bactericidal activity of chemical disinfectants and antiseptics used in food, industrial, domestic and institutional areas. At 20 degrees C, 13 products passed at their in-use concentration (under clean and dirty conditions) against Ps. aeruginosa and 15 passed against E. coli O157:H7. The number of products passing the test at 10 degrees C was 11 and 14 for Ps. aeruginosa and E. coli O157:H7, respectively. The products exhibiting reduced efficacy at the lower temperature were amphoterics and quaternary ammonium compounds although some of these types of products were effective at both temperatures. Products that passed against Ps. aeruginosa generally also passed against E. coli O157:H7. Taking all the results together, only 11 of the total of 18 products achieved a pass result under all the parameters tested. This work demonstrates the need for final verification of disinfectant efficacy by undertaking field trials in the food-processing environment in which the product is intended for use.

Cold Temperature↗

A model of microbial survival curves in water treated with a volatile disinfectant.

AIM: To develop a method to calculate microbial survival parameters in water treated with a dissipating disinfectant and predict the inactivation patterns under different agent concentrations and decay rate regimes. METHODS AND RESULTS: It has been assumed that the survival curves of the organism, under (hypothetical) constant agent concentration conditions, follow the power law model log [N(t)/N0] = -btn with a concentration independent exponent, n. The concentration dependence of the 'rate parameter', b, has been assumed to obey a log logistic relationship. Under changing disinfectant concentration, the survival curve is constructed so that its local slope, i.e. momentary logarithmic inactivation rate of the organism, is the slope of the momentary 'constant concentration' curve at the momentary agent concentration, at the time which corresponds to the momentary survival ratio. The resulting differential equation was used to retrieve the survival parameters by numerical minimization procedures. Once these are calculated, the equation is solved numerically to produce the survival curve for almost any conceivable agent concentration history. The predictive ability of the method is demonstrated by using the survival parameters, calculated from published data obtained under one concentration profile, to predict survival curves under very different decay patterns. CONCLUSIONS: It is possible to calculate microbial survival parameters from data obtained in treatments where the unstable or volatile disinfectant progressively dissipates and use them to predict the outcome of different treatments. SIGNIFICANCE AND IMPACT OF THE STUDY: The proposed mathematical method will enable the prediction of microbial inactivation patterns in water treated with unstable and/or volatile chemical agents.

Bacteria↗

Effect of phenolic and chlorine disinfectants on hepatitis C virus binding and infectivity.

BACKGROUND: The purpose of this study was to evaluate the inhibitory activity of 2 polyphenolic disinfectants and a chlorine compound (NaDCC) on hepatitis C virus (HCV) binding and infectivity. METHODS: VERO cells (a continuous cell line derived from cynomolgus kidney cells) suitable for analyzing HCV binding and replication, and the competitive reverse transcription (cRT-PCR) technique for HCV RNA molecules quantitative evaluation have been chosen as a methodologic approach for the antiviral activity testing. RESULTS: At their recommended use dilutions, polyphenolic disinfectants inhibited HCV binding and replication. The chlorine compound was ineffective, probably a result of its low concentration in the presence of protein substances in VERO cell cultures. CONCLUSIONS: Inhibition of HCV binding and replication by the tested polyphenolic associations confirm their value in instrument decontamination and environmental disinfection against this clinically important lipid virus.

Animals↗

Can household dishwashers be used to disinfect medical equipment?

In hospitals, medical instruments are usually cleaned and disinfected in a washer/disinfector. However, it is not efficient for small hospitals or general practitioners to purchase such machines as they would not be working to capacity. We investigated the possibility of cleaning and disinfecting medical equipment in a conventional household dishwasher modified to achieve a temperature of 71 degrees C. For this purpose we contaminated screws with different test soils containing either bacterial (100 screws) or viral (106 screws) suspensions. Test organisms were re-isolated from 2% of the screws after bacterial contamination and 4.7% of those with viral contamination. In both cases we found dishwasher-processing to be a suitable means of disinfecting medical instruments.

Bacterial Infections↗

Inactivation of hepatitis B virus in plasma by hospital in-use chemical disinfectants assessed by a modified HepG2 cell culture.

Because of the difficulties of the chimpanzee model and the genetic differences using the duck model, we developed a cell culture method to measure human hepatitis B virus (HBV) inactivation in vitro. Pooled HBV-infected human plasma that had been exposed to a disinfectant was left in contact for three days with a cell culture of the human hepatoma cell line, HepG2, with 4% polyethyleneglycol and 3 mM sodium butyrate. The mean log10 of the viral titre of unexposed plasma was 4.87 infectious units per mL. Our results showed that 1% glutaraldehyde, sodium hypochlorite at 4700 ppm free chlorine and an iodophor-detergent disinfectant containing 3.6% povidone-iodine reduced viral titres by factors exceeding 10(3)-10(4). However, sodium hypochlorite at 1000 ppm free chlorine had minimal activity and povidone-iodine at 9, 5 and 3.6% had no measurable activity (less than 10-fold reduction). This is the first study using a cell culture model to assess disinfectant activity against HBV. It demonstrates more rapidly than the chimpanzee model that glutaraldehyde and sodium hypochlorite, using standard concentrations and exposure times compatible with clinical practice, were highly active against HBV. However, unexpectedly for an enveloped virus, we found no antiviral activity for iodine in the absence of detergent.

Blood↗

Sterilization and disinfection in general practice within university health services.

A postal questionnaire on 'sterilization and disinfection' was sent to all 144 nurse members of the British Association of Health Services in Higher Education (BAHSHE). Forty-nine (34%) completed valid questionnaires were returned. Despite the majority of practices performing minor surgical procedures such as cervical cytology (N= 40, 82%), ear syringing (N= 44, 90%) and wound dressing (N= 49, 100%), only 11 (22%) had access to a sterile supply department (SSD), and the definitions of sterilization and disinfection were only identified by 23 (52%) and 14 (32%) of the respondents, respectively. Forty-one (84%) respondents had a benchtop sterilizer (30 had a benchtop sterilizer, 11 a vacuum sterilizer and two had both), although there was considerable confusion on their appropriate use and maintenance. Just over half had written procedures for sterilizer use, no practice changed the sterilizer water on a daily basis as recommended by the Medical Devices Agency (MDA), few kept a sterilizer logbook and even fewer had read the MDA Device Bulletin on benchtop sterilizers. The majority of respondents voiced an interest in attending a workshop on sterilization and disinfection. We conclude that despite the location of the general practices within an academic environment, the concept of infection control is clearly not understood by university health service staff. As the implications of a failure to implement proper infection control procedures are potentially serious, the need for adequate education and training of staff is of critical importance.

Clinical Competence↗

Impact of teaching interventions on nurse compliance with hand disinfection.

The impact of teaching interventions and the availability of additional dispensers for alcoholic hand disinfection was measured during three study periods. A nursing care system of relevant nursing interventions was found to be a useful tool for the assessment of compliance with hand hygiene requirements if combined with an analysis of hand disinfectant use. This study shows that compliance with hand disinfection can be improved through targeted teaching and supportive structural improvements, and that this positive impact may persist even after targeted teaching activities have ended.

Guideline Adherence↗

Methods of disinfecting endoscopic material: results of an international survey.

A questionnaire on the methods of cleaning and disinfecting endoscopic equipment was mailed to 120 centers in Western Europe. Seventy-four questionnaires (61%) were returned. The centers were classified into three groups according to the number of endoscopic procedures performed per year. This survey has shown that precautions are more rigid in specialized centers than in units doing fewer than 1,500 endoscopic investigations a year. Complete disinfection is done by almost all the centers after ERCP in infected patients or in the case of HBsAg and HIV-positive patients, but only by 70% of centers after completion of endoscopies performed in patients with gastrointestinal hemorrhage and unknown immunological status. After endoscopic examination performed in presumably non-infected subjects, complete disinfection is not done in any center after gastroscopy, in 13% after colonoscopy and in 30% after ERCP. Continued education of endoscopic personnel and greater availability of adequate endoscopic equipment is mandatory for minimizing the risk of endoscopy-related infections.

Disinfection↗

[Cleaning and disinfection of endoscopes in general practice and ambulatory care].

The legal conditions in Germany for cleaning and disinfection of endoscopes depend on the terms of reference of the "Bundesgesundheitsamt (BGA)" and the "Deutsche Gesellschaft für Hygiene und Mikrobiologie (DGHM)" and the "Unfallverhütungsvorschrift (UVV) der Berufsgenossenschaft für Gesundheitsdienst und Wohlfahrtspflege". The different regulations and the resulting practical consequences for manual and mechanical cleaning and disinfection of rigid and flexible endoscopes are described. Particularly the HBV-HIV-problems as well as the respective inactivation times resulting there from, standby times and concentrations of different solutions for disinfection are discussed. Presentation of the practicability of the different steps in daily ENT-practice and ambulance.

Communicable Disease Control↗

[Reducing vaginal flora by preoperative disinfection].

In 70 gynaecological patients vaginal disinfection by povidone-iodine and chlorhexidine solution (LEC) was investigated. The preoperative bacterial spectrum corresponded to the specifications in literature. Only lactobacilli were found in fewer cases than expected, an effect, which was explained by the povidone-iodine sanitation of the vagina a day before the operation. In cases of disturbed lactobacilli flora, facultative pathogen species were found in high concentrations up to 10(6) CFU/ml. Germ reduction achieved more than 3.4 log CFU/ml in the three groups of antiseptics. Povidone-iodine left a residue of other bacteria species in one-fifth of the cases, one of the LEC-solutions only in one-tenth of the cases. B-Streptococcus, Streptococcus viridans (mitis) and Candida glabrata were found in concentrations up to 10(3) CFU/ml in the residues. In these cases, a disturbed ecology of the vagina had already existed previously. It is concluded, not to disturb normal vaginal flora needlessly before preoperative disinfection and to restore it as soon as possible after operation. The LEC solutions appeared to be a competent alternative to povidone-iodine solution in vaginal disinfection.

Administration, Intravaginal↗

Combined application of simulated reuse and quantitative carrier tests to assess high-level disinfection: experiments with an accelerated hydrogen peroxide-based formulation.

BACKGROUND: Heat-sensitive medical devices require chemical disinfection between patients, and certain formulations for this purpose can be reused for several days. Because dilution, evaporation, and breakdown or neutralization of active ingredients can occur during reuse, it is vital to ensure that the solution retains its broad-spectrum germicidal activity even at the end of the recommended reuse period. OBJECTIVE: The purpose of this study was to combine the US Environmental Protection Agency's and the Food and Drug Administration's recommended simulated reuse method with recently developed quantitative carrier tests (QCT) to assess the broad-spectrum germicidal activity of a 7% solution of accelerated hydrogen peroxide (pH 2.9) stressed for 14 days. MATERIALS AND METHODS: On alternate days baths with 3 lots of the test formulation were stressed by the addition of bacteria (Salmonella choleraesuis, Staphylococcus aureus, and Pseudomonas aeruginosa ) on glass beads and spores (Bacillus subtilis and Clostridium sporogenes ) on metallic penicylinders. In addition, one set of respiratory therapy equipment was subjected to 3 daily cycles of disinfection in each bath. The pH and H(2)O(2) levels in the test samples were measured, and they were also subjected to QCTs for their sporicidal, bactericidal, virucidal, fungicidal, and mycobactericidal activities. RESULTS: After 14 days of reuse, the pH of the test solutions remained essentially unchanged. Although the level of H(2)O(2) dropped from a high of 7.66% to as low as 6.40%, all lots showed the required level of broad-spectrum germicidal activity after 14 days of stress. CONCLUSIONS: The stress test and QCT were successfully combined in demonstrating the broad-spectrum germicidal activity of a high-level disinfectant subjected to 14 days of simulated reuse.

Chemistry, Pharmaceutical↗

Coagulation and disinfection efficiency of an electrochemically prepared dual-function reagent in municipal wastewater.

A novel dual-function chemical reagent was successfully prepared by electrolysis process. With high content of Al13 species and active chlorine, the electrochemically prepared polyaluminum chlorine (E-PACl) as the dual-function chemical reagent presented the integrated properties of coagulation and disinfection in water treatment. The results obtained from jar tests in municipal wastewater and hydrolyzed Al (III) speciation distribution characterization confirmed that the Al13 species was the most effective polymeric Al species in PACl responsible for coagulation. The solid-state 27Al NMR spectra for precipitates revealed that the precipitates structure formed from Al coagulants with various pre-hydrolysis degrees were significantly different, and proved that the preformed Al13 polymer is quite stable during the coagulation process. E-PACl performed well on both particulate and organic matter removals in municipal wastewater treatment. The higher the degree of pre-hydrolysis, the lower the efficiency of the coagulant removed phosphorus from water. The active chlorine in E-PACl was an effective disinfectant to inactivate fecal coliforms. When dosed 24 mg Al/L E-PACl, effective coagulation and disinfection in municipal wastewater could be achieved simultaneously. E-PACl may have a great potential to domestic use and small treatment plants for municipal wastewater reuse.

Aluminum Hydroxide↗

Component-based and whole-mixture techniques for addressing the toxicity of drinking-water disinfection by-product mixtures.

Chemical disinfection of water is of direct public health benefit as it results in decreased water-borne illness. The chemicals used to disinfect water react with naturally occurring organic matter, bromide, and iodide in the source water, resulting in the formation of disinfection by-products (DBPs). Despite the identification of several hundred DBPs, more than 50% of the mass of total organic halide formed during chlorination remains unidentified. The toxic contribution of the DBPs that are formed and present but not yet chemically identified, the unidentified fraction, has been largely unexplored. A better understanding of the potential for adverse human health consequences associated with exposure to the DBPs present in drinking water will be gained by integration of knowledge on the toxicity of individual DBPs; simple, defined DBP mixtures; complex, environmentally realistic DBP mixtures with partial chemical characterization; and the unidentified fraction.

Chlorine Compounds↗