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PubMed2001

Evaluation of the efficiency of peracetic acid in the disinfection of sewage effluents.

AIMS: Evaluation of the efficiency of peracetic acid in the disinfection of wastewater in a large treatment plant. METHODS AND RESULTS: Over a period of 18 months 30 sample collections were made, each consisting of three samples taken from: raw incoming sewage, secondary effluent (after 10-12 h) and secondary effluent disinfected with 1.5-2 mg l(-1) of peracetic acid (contact time: 20 min). Total coliforms and Escherichia coli declined from 10(7) MPN 100 ml(-1) in the raw sewage to 10(2) in the disinfected effluent and the enterococci fell from 10(6) MPN 100 ml(-1) to 702 MPN 100 ml(-1). The reduction of bacteria increased with the rise in temperature and decreased with the rise in BOD5. CONCLUSIONS: Disinfection with peracetic acid reduced levels of faecal contamination by 97%, thus attaining the limit recommended by current Italian law (Escherichia coli <or= 5000 MPN 100 ml(-1)) for discharge into surface waters. SIGNIFICANCE AND IMPACT OF THE STUDY: The process of disinfection with peracetic acid is easier to manage than other more common methods and the tests performed confirm that from the bacteriological point of view good results can be obtained for urban effluents.

Bacteria↗
PubMed2001

Evaluation of donor arm disinfection techniques.

BACKGROUND AND OBJECTIVE: To validate a standardized optimal national procedure for donor arm disinfection. MATERIALS AND METHODS: A direct swabbing and plating technique was used to enumerate bacteria present on the arm pre- and postdisinfection. Twelve donor arm disinfection techniques were evaluated. RESULTS: The Medi-Flex Adapted method, consisting of a two-stage process with an initial application of isopropyl alcohol followed by tincture of iodine, produced the best arm disinfection. A percentage reduction in bacterial counts of 99.79% (logarithmic reduction of 2.67) was obtained. Postdisinfection, 70% of donors had bacterial counts of zero, and 98% had counts of 10 or less. CONCLUSION: The Medi-Flex disinfection method offers the English National Blood Service a validated, optimal 'best practice' disinfection technique and should contribute significantly to the reduction in risk of transmission of bacteria by transfusion.

2-Propanol↗
PubMed2001

Hand disinfection according to the European Standard EN 1500 (hygienic handrub): a study with gram-negative and gram-positive test organisms.

It was the aim of this study to compare the efficacy of alcohol-based hand disinfectants according to European Standard EN 1500 (hygienic handrub), using the routine test organism Escherichia coli and, additionally, Micrococcus luteus as a surrogate for Gram-positive pathogens. One ethanol-based hand disinfectant (product A) and one propanol-based hand disinfectant (product B) were used in all experiments. Product B (propanol-based) was significantly more effective against both test organisms than product A (ethanol-based) in quantitative suspension tests but not in tests simulating practical conditions. In the experiments according to EN 1500 germ reduction rates obtained with the ethanol-containing formulation A were identical for E. coli and M. luteus. Product B was slightly, but not significantly more effective against M. luteus. To conclude, using E. coli as the test organism for evaluating the antibacterial efficacy of alcoholic hand disinfectants under practical conditions even appears to be sufficient to permit the drawing of conclusions for Gram-positive pathogens. However, more alcohol-based hand disinfectants should be tested in further studies to verify the results obtained.

Anti-Infective Agents, Local↗
PubMed2004

Surface disinfection tests with Salmonella and a putative indicator bacterium, mimicking worst-case scenarios in poultry houses.

Surface disinfection studies mimicking worst-case scenarios in badly cleaned poultry houses were made with 3 bacterial isolates (Salmonella enteritidis, Salmonella senftenberg, and Enterococcus faecalis), and 3 1% disinfectant solutions, formaldehyde (F; 24.5% vol/vol), glutaraldehyde/benzalkonium chloride (G; Bio Komplet Plus), and a peroxygen compound (P; Virkon S), with World Health Organization (WHO) standard hard water as a control. Materials (concrete paving stones, steel feed chain links, wooden dowels, and jute egg belts) and organic matter found commonly in poultry houses (feed, fats, egg yolk) were used in the tests. Organic matter inoculated with high numbers of stationary phase cultures was added to materials and dried for 24 h at different temperatures (6, 11, 20, or 30 degrees C), immersed in solutions for set time periods (5, 15, or 30 min), and dried again for 25 h (6, 11, or 30 degrees C). Then, traditional recovery procedures (using 10-fold dilutions until 10(-4), i.e., a most probable number method) were applied. For the 2 Salmonella isolates, the efficacy of the solutions was (in decreasing order): formaldehyde > glutaraldehyde/benzalkonium chloride > peroxygen compound > WHO hard water, except when feed chain links with fats were disinfected using 30 degrees C before and after disinfection, for which the peroxygen compound seemed more effective. Enterococcus faecalis was equally or less susceptible than S. enteritidis and S. senftenberg, indicating its suitability as an indicator bacterium. For the peroxygen compound, S. senftenberg was more susceptible than S. enteritidis in spite of higher minimum inhibitory concentrations to this disinfectant for the former.

Animals↗
PubMedDate not supplied

Microbial bioburden in endoscope reprocessing and an in-use evaluation of the high-level disinfection capabilities of Cidex PA.

Most endoscopy clinics use 2% glutaraldehyde as a high-level disinfectant for reprocessing flexible endoscopes. However, even with contact times greater than 30 minutes, survival of organisms has been documented. We compared the high-level disinfection capabilities of glutaraldehyde (45-minute immersion) with a new peracetic acid germicide (20- to 25-minute immersion). Channels, valve housings, and outer sheaths were sampled to quantify bioburden levels after a patient procedure, after manual cleaning, and after disinfection. Total mean bioburden after clinical use was greater than 6 log10 colony-forming units (CFU). Manual cleaning reduced the bioburden by means of 4.7 log10 CFU (gastroscopes) and 6.2 log10 CFU (colonoscopes). High-level disinfection with the new product was achieved in five of six (product stressed by EPA Reuse Test) and 7 of 10 (product stressed by dilution and organic load) successfully disinfected endoscopes, whereas glutaraldehyde achieved it in 4 of 10 (product stressed by dilution and organic load). We conclude that the new peracetic acid product (20- and 25-minute contact time) is at least as effective as glutaraldehyde (45-minute contact time) for reducing the bioburden of vegetative aerobic organisms in endoscopes.

Colony Count, Microbial↗
PubMed1997

Disinfection of human enteric viruses on fomites.

The virucidal action of several commercially available disinfectant preparations was assayed against hepatitis A virus and human rotavirus dried on polystyrene. Overall, the level of virus disinfection achieved was very poor, usually inducing less than 3 log titre reduction. Suspension tests performed with the same disinfectants showed different virus inactivation rates, thus failing to provide a reliable indication of the actual virus disinfection on fomites. In our studies, bacteriophages of Bacteroides fragilis proved to be a simple, cheap and reliable screening tool for the evaluation of virus disinfection on non-porous surfaces. The same conclusion cannot be drawn for poliovirus.

Bacteroides fragilis↗
PubMed1994

Physiological responses of bacteria in biofilms to disinfection.

In situ enumeration methods using fluorescent probes and a radioisotope labelling technique were applied to evaluate physiological changes of Klebsiella pneumoniae within biofilms after disinfection treatment. Chlorine (0.25 mg of free chlorine per liter [pH 7.2]) and monochloramine (1 mg/liter [pH 9.0]) were employed as disinfectants in the study. Two fluorgenic compounds, 5-cyano-2,3-ditolyl tetrazolium chloride and rhodamine 123, and tritiated uridine incorporation were chosen for assessment of physiological activities. Results obtained by these methods were compared with those from the plate count and direct viable count methods. 5-Cyano-2,3-ditolyl tetrazolium chloride is an indicator of bacterial respiratory activity, rhodamine 123 is incorporated into bacteria in response to transmembrane potential, and the incorporation of uridine represents the global RNA turnover rate. The results acquired by these methods following disinfection exposure showed a range of responses and suggested different physiological reactions in biofilms exposed to chlorine and monochloramine. The direct viable count response and respiratory activity were affected more by disinfection than were the transmembrane potential and RNA turnover rate on the basis of comparable efficiency as evaluated by plate count enumeration. Information revealed by these approaches can provide different physiological insights that may be used in evaluating the efficacy of biofilm disinfection.

Chloramines↗
PubMed1974

Chemical disinfection of holding-tank sewage.

A number of chemical disinfectants were evaluated for their bactericidal and virucidal effectiveness in holding-tank sewage. It was found that the disinfection efficiencies of formaldehyde, benzalkonium chloride, cetylpyridinium chloride, and methylene blue were markedly improved if the pH of the sewage was raised from 8.0 to 10.5. When formaldehyde, benzalkonium chloride, and methylene blue were tested with either 2-week holding times with no sewage additions or 10-day holding times with daily sewage additions, disinfection effectiveness was maintained as long as the sewage pH was kept at 10.5 and the disinfectant concentration was kept at 100 mg/liter or more. Calcium hypochlorite, zinc sulfate, and phenol were found to be relatively ineffective disinfectants for holding-tank sewage.

Bacteria↗
PubMed2000

Availability of an alcohol solution can improve hand disinfection compliance in an intensive care unit.

We investigated whether rubbing with an alcohol solution increases compliance with hand disinfection in a medical intensive care unit (MICU). During a first period (P1), hand disinfection was achieved only through conventional washing, whereas during a second period (P2), hand disinfection could be achieved either through conventional washing or rubbing with an alcohol solution. There were 621 opportunities for hand disinfection during P1 and 905 opportunities during P2. General compliance during P1 was 42.4%, and reached 60.9% during P2 (p < 0.001). This improvement was observed among nurses (45.3% versus 66.9%, p < 0.001), senior physicians (37. 2% versus 55.5%, p < 0.001), and residents (46.9% versus 59.1%, p = 0.03). Acceptability and tolerance were evaluated through the answers to an anonymous questionnaire distributed to all 53 health care workers in the MICU. Rubbing with alcohol solution was an easy procedure (100% of responses) and induced mild side effects in less than 10% of respondents. In a complementary study conducted 3 mo after the first one, compliance remained better than during P1 (51. 3% versus 42.4%, p = 0.007). These findings suggest that rubbing with alcohol solution increases compliance with hand disinfection, and that it could be proposed as an alternative to conventional handwashing in the MICU.

Attitude of Health Personnel↗
PubMed1986

Dimensional stability of dental impressions after immersion disinfection.

Disinfection of dental impressions via short-term immersion in 0.5% or 1% sodium hypochlorite does not significantly affect the dimensional accuracy of the resultant casts. In addition, immersion in glutaraldehydes, povidone-iodine diluted in water, or halogenated phenol has no apparent effect on the dimensional stability of rubber impression materials. The results of this study support the use of immersion disinfectants for treatment of impressions for study models or removable dental appliances or prostheses. Coupled with the findings of other authors, the data suggest that such disinfection also would be suitable for rubber base and vinyl polysiloxane impressions for cast restorations. Given the need for infection control in the treatment of all dental patients, the results of this study support the recommendations of the American Dental Association for disinfection of dental impressions via immersion in an appropriate disinfectant solution.

Alginates↗
PubMed1997

Pneumocystis carinii cysts are susceptible to inactivation by chemical disinfectants.

The inactivation efficacy of eight disinfectants commonly used in laboratories and animal rooms to inactive Pneumocystis carinii cysts was estimated by experimental infection in C.B-17-scid mice. The disinfectants examined in this study were 70% ethyl alcohol, 10% iodoform, 0.5% hypochlorous acid, two 1% quanternary ammonium salts, 3% hydrogen peroxide, sodium chlorite and 1% cresol soap. The lung homogenates from P. carinii infected C.B-17-scid mice were treated with each disinfectant for 15 min at room temperature, washed with saline, and inoculated into C.B-17-scid mice. Eight weeks after inoculation, lungs from these mice were examined by staining with toluidine blue O to detect P. carinii cysts. PCR amplifying 346 bp of P. carinii specific mitochondrial ribosomal RNA large segments was also performed using DNA extracted from the lungs of the mice. As a result, seven disinfectants, excepting for 0.5% hypochlorous acid, were effective in the inactivation of P. carinii cysts. These results suggest that P. carinii cysts were sensitive to chemical disinfectants even though they have been commonly considered as insensitive.

Animals↗
PubMedDate not supplied

[Evaluation of surface disinfectants utilized in dentistry].

Surface disinfection is a procedure carried out on the external parts of the dental equipment as well as on other items of the dental office. The aim of this study was to analyze the efficacy of 4 surface disinfectants utilized in dentistry: 77 degrees GL alcohol, phenolic compound (Duplofen), iodophor (PVP-I) and 77 degrees GL alcohol with 5% of chlorhexidine. Four surfaces of the equipment were analyzed in the study (the carter, the washbasin for hand-washing, the headrest of the chair and the external surface of the reflector), and the spray-wipe-spray procedure was carried out. From each surface, samples were collected by means of surface plates containing Mitis Salivarius bacitracin sucrose agar, Sabouraud Dextrose agar with chloramphenicol, MacConkey agar and blood agar, for counting mutans streptococci, Candida yeasts, gram-negative bacteria and total microorganisms, respectively (ufc/plate). The results were statistically analyzed by means of the Student's t test in order to compare the mean ufc/plate values. The most effective disinfectant was 77 degrees GL alcohol with 5% of chlorhexidine, mainly against gram-positive bacteria. Iodophor and phenolic compound were also effective in microbial reduction. 77 degrees GL alcohol was the least effective product - however, although it is not considered as a surface disinfectant, it produced, in this study, statistically significant microbial reduction after the disinfecting procedure.

Candida↗
PubMed1995

Environmental considerations of disinfectants used in agriculture.

Using disinfectants in agriculture increasingly requires consideration of the indirect effects on the environment and human health. At present, only limited information is available on post-application effects of disinfectants, and such data therefore needs to be gathered in order to assess potential effects. In addition, a basis exists for establishing precautionary guidelines using current information. Optimum handling and application procedures require a knowledge of the specific features of each type of disinfectant. A need to establish product standards through efficacy tests has also emerged. The benefits of disinfectants for disease control must also be weighed against any environmental consequences. Emergency application of a disinfectant carries different implications from routine use on farms, and any large-scale application should undergo an environmental impact assessment.

Agriculture↗
PubMed1995

Writing guidelines to require disinfection.

Disinfection, when performed correctly, is an important step in the control and elimination of specific disease agents. Typical disinfection instructions merely state that 'the premises or materials contaminated by or exposed to disease shall be disinfected'. Directions are rarely given on how to perform the job. The first stage in a complete and proper disinfection operation for materials and property involves a thorough assessment of the problem and the development of a step-by-step action plan. Detailed guidelines should address the relevant questions--who should do what? where, when and how?--in relation to each step of the job. It should be ensured that all work is correctly executed and reported, and a follow-up evaluation of the premises should be made to verify that the disease agent(s) have been destroyed. Persons using disinfectants should always follow safety precautions to avoid the risk of occupational injuries.

Animals↗
PubMed2006

Mechanisms of actions of sodium hypochlorite in cleaning and disinfection processes.

Sodium hypochlorite (NaOCl) is the most widely used disinfectant in the food industry despite the increasing availability of other disinfectants. Sodium hypochlorite fulfills many requirements as the ideal disinfectant and furthermore it has an excellent cleaning action. The effectiveness of sodium hypochlorite in the cleaning and disinfection processes depends on the concentration of available chlorine and the pH of the solution. Hypochlorous acid (HOCl) is a weak acid and dissociates to the hypochlorite ion (-OCl) and proton (H+) depending on the solution pH. It is generally believed that HOCl is the active species in the germicidal action, whereas the concentration of -OCl is a key factor determining the cleaning efficiency. This implies that the optimal pH region of the germicidal activity of sodium hypochlorite differs from that of its cleaning activity. This paper describes the theory and practice of the cleaning and disinfecting operations based on the use of sodium hypochlorite solution.

Anti-Infective Agents↗
PubMed2001

[Survey of disinfectant usage in a polyclinic in Rome: preliminary results].

The authors describe the survey that was conducted in the largest hospital in Rome. The aim was to estimate the disinfectants and chemical sterilizers employed and asses possible hazards for patients and workers arising from the use of disinfectants, together with the problem of waste disposal. The study was conducted by means of a survey form that was distributed to 39 departments/institute in the whole hospital of which 24 (61%) responded. Overall 635 charts were collected listing 886 usage procedures and 110 formulations with 40 different active ingredients. The disinfection fields of use were: skin(52.4%) environment (28.8%) and hospital equipment (20.8%) This study shows that a modern hospital should select very few disinfectants and prepare a handbook that can explain disinfectant usage procedures and concentrations. In the guidelines the problem of waste disposal and employee safety should also be considered.

Containment of Biohazards↗
PubMed2002

[Decontamination of dental unit waterlines using disinfectants and filters].

Bacterial contamination of the dental unit water system can become a health problem for patients, particularly if they are immunodepressed. The present study has had the purpose of evaluating the effectiveness of methods of chemical decontamination using different disinfectants (peracetic acid, hydrogen peroxide, silver salts, chloramine T, glutaraldehyde T4) and methods of physical decontamination using synthetic membranes for the filtration of water. A preliminary removal procedure of the biofilm present in the waterline has been followed in a dental unit prepared on purpose for the research; subsequently different 2-week long maintenance procedures were applied using disinfectants injected by a pump and finally the bacterial contamination of the water flowing from the waterline was evaluated. The physical decontamination was performed using 0.22 mm membrane filters, which have been installed also in another dental unit, and the filtered water was analyzed to detect bacterial contamination. The preliminary procedure of biofilm removal succeeded obtaining germ-free water. Among the disinfectants used for the maintenance of the water quality only glutaraldehyde T4 was able to reduce the bacterial contamination under the limit suggested by the ADA. The membrane filter system was not able to purify the water, but when a disinfectant (peracetic acid) was used in the last part of the waterline good results were obtained. At present no decontamination system of dental waterline is available, and glutaraldehyde T4 seems to be the best disinfectant only if integrated with periodic biofilm removal for the maintenance of the water quality.

Biofilms↗
PubMedDate not supplied

Carrier tests to assess microbicidal activities of chemical disinfectants for use on medical devices and environmental surfaces.

For well over a decade, many deficiencies have been identified in current AOAC methods used to assess the microbicidal activities of chemical disinfectants on medical devices and environmental surfaces. This report discusses the development of quantitative carrier tests (QCT) designed to address these concerns. Decontamination of surfaces with dried inocula is invariably more difficult than when microorganisms are in suspension. For medical device as well as environmental decontamination, microbicides are used on contaminated surfaces, thus making it necessary to evaluate their microbicidal action on representative carrier materials contaminated with a dried challenge microorganism(s). Our approach is a 2-tiered QCT. The first tier (QCT-1) uses relatively ideal conditions to assess performance of the microbicide for screening purposes; the test uses smooth glass surfaces and quantities of disinfectant in excess of those likely to be experienced in the field. The second tier of testing (QCT-2) is more stringent because it uses (1) disks of brushed stainless steel as carriers, (2) only 50 microL of the test formulation on each carrier as compared to 1 mL in QCT-1, and (3) an added soil load to simulate the presence of residual body fluids or accumulated surface dirt. This review also discusses the factors that affect disinfection of medical devices and environmental surfaces in the context of the methodology used to evaluate the potency of microbicides. Specific recommendations for discussion are included, and performance criteria are suggested based on a risk-reduction approach for different classes of disinfectants. The focus is on improving the relevance of the test methodology to actual field use of disinfectants for devices and facilities in health care, and potentially in other settings. It is hoped that this review and its recommendations will initiate needed discussion and resolution of the many issues identified.

Chemistry Techniques, Analytical↗