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Validation of AKACID plus as a room disinfectant in the hospital setting.

AKACID Plus, a novel polymeric guanidine with broad antimicrobial activity against multiantibiotic-resistant bacterial strains, was used in the present study as a room disinfectant. Disinfection of closed rooms experimentally contaminated with antibiotic-susceptible and multiresistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Escherichia coli was performed using AKACID Plus at concentrations of 0.1, 0.25, and 0.5% for 100 min. Bacterial suspensions were distributed on plastic and stainless steel plates and placed in a test room. Recovery of the test microorganisms was determined before nebulizing, 60 and 100 min after initiation, and 4 h after the end of room disinfection by a simple swab-rinse technique. The swab-rinse method demonstrated a dose- and time-dependent effectiveness of AKACID Plus in eradicating S. aureus, E. coli, and P. aeruginosa on plastic and stainless steel plates. Nebulized 0.5% AKACID Plus was successful in eliminating all hospital pathogens within 340 min. After the use of 0.25% AKACID Plus, MRSA was still detectable on microbial carrier plates. The test concentration of 0.1% AKACID Plus achieved a significant reduction of S. aureus and P. aeruginosa on plastic and stainless steel plates but was sufficient to eradicate only E. coli. These results suggest that nebulized AKACID Plus at a concentration of 0.5% is a potent substance for eradication of pathogenic organisms in the hospital setting.

Disinfectants↗

Disinfection of bacteria attached to granular activated carbon.

Heterotrophic plate count bacteria, coliform organisms, and pathogenic microorganisms attached to granular activated carbon particles were examined for their susceptibility to chlorine disinfection. When these bacteria were grown on carbon particles and then disinfected with 2.0 mg of chlorine per liter (1.4 to 1.6 mg of free chlorine residual per liter after 1 h) for 1 h, no significant decrease in viable counts was observed. Washed cells attached to the surface of granular activated carbon particles showed similar resistance to chlorine, but a progressive increase in sublethal injury was found. Observations made by scanning electron microscope indicated that granular activated carbon was colonized by bacteria which grow in cracks and crevices and are coated by an extracellular slime layer. These data suggest a possible mechanism by which treatment and disinfection barriers can be penetrated and pathogenic bacteria may enter drinking water supplies.

Adhesiveness↗

Bactericidal properties of a new water disinfectant.

The N-chloramine compound 3-chloro-4,4-dimethyl-2-oxazolidinone (agent I) has been compared with calcium hypochlorite as to its efficacy as a bactericide for the treatment of water. The study included concentration, contact time, pH, temperature, and water quality as controlled variables. The species of bacteria tested were Staphylococcus aureus, Pseudomonas aeruginosa, and Shigella boydii. In general, for highly pure, demand-free water, calcium hypochlorite was the more rapid disinfectant at a given total chlorine concentration, although for water containing a controlled amount of organic load, agent I was the better disinfectant. The differences in efficacy of each of the two disinfectants can be attributed primarily to their different stabilities in water at various controlled conditions.

Bacteria↗

Disinfection of drinking water by using a novel electrochemical reactor employing carbon-cloth electrodes.

A novel electrochemical reactor employing carbon-cloth electrodes was constructed for disinfection of drinking water. Escherichia coli K-12 (10(2) cells per cm3) was sterilized when a cell suspension was passed through the reactor at a dilution rate of 6.0 h-1, and a potential of 0.7 V versus a saturated calomel electrode was applied to an electrode. The survival ratio increased with increasing dilution rate but was less than 0.1% at dilution rates of less than 6.0 h-1. Although the survival ratio increased with increasing cell concentration above 10(3) cells per cm3, the disinfection rate also increased. The disinfection rate was 6.0 x 10(2) cells per cm3 per h at a cell concentration of 10(2) cells per cm3. Continuous sterilization of E. coli cells was carried out for 24 h. Sterilization is based on an electrochemical reaction between the electrode and the cell which is mediated by intracellular coenzyme A. Sterilization of drinking water by using this reactor was successfully performed, demonstrating the potential of such a reactor for clean and efficient water purification.

Disinfection↗

Adaptation and growth of Serratia marcescens in contact lens disinfectant solutions containing chlorhexidine gluconate.

Serratia marcescens (11 of 12 strains) demonstrated an ability to grow in certain chlorhexidine-based disinfecting solutions recommended for rigid gas-permeable contact lenses. For a representative strain, cells that were grown in nutrient-rich medium, washed, and inoculated into disinfecting solution went into a nonrecoverable phase within 24 h. However, after 4 days, cells that had the ability to grow in the disinfectant (doubling time, g = 5.7 h) emerged. Solutions supporting growth of S. marcescens were filter sterilized. These solutions, even after removal of the cells, showed bactericidal activity against Pseudomonas aeruginosa and a biphasic survival curve when rechallenged with S. marcescens. Adaptation to chlorhexidine by S. marcescens was not observed in solutions formulated with borate ions. For chlorhexidine-adapted cells, the MIC of chlorhexidine in saline was eightfold higher than that for unadapted cells. Cells adapted to chlorhexidine showed alterations in the proteins of the outer membrane and increased adherence to polyethylene. Cells adapted to chlorhexidine persisted or grew in several other contact lens solutions with different antimicrobial agents, including benzalkonium chloride.

Adaptation, Biological↗

Disinfection of water containing natural organic matter by using ozone-initiated radical reactions.

Ozone is widely used to disinfect drinking water and wastewater due to its strong biocidal oxidizing properties. Recently, it was reported that hydroxyl radicals ((.)OH), resulting from ozone decomposition, play a significant role in microbial inactivation when Bacillus subtilis endospores were used as the test microorganisms in pH controlled distilled water. However, it is not yet known how natural organic matter (NOM), which is ubiquitous in sources of drinking water, affects this process of disinfection by ozone-initiated radical reactions. Two types of water matrix were considered for this study. One is water containing humic acid, which is commercially available. The other is water from the Han River. This study reported that hydroxyl radicals, initiated by the ozone chain reaction, were significantly effective at B. subtilis endospore inactivation in water containing NOM, as well as in pH-controlled distilled water. The type of NOM and the pH have a considerable effect on the percentage of disinfection by hydroxyl radicals, which ranged from 20 to 50%. In addition, the theoretical T value of hydroxyl radicals for 2-log B. subtilis removal was estimated to be about 2.4 x 10(4) times smaller than that of ozone, assuming that there is no synergistic activity between ozone and hydroxyl radicals.

Bacillus subtilis↗

Specific growth rate determines the sensitivity of Escherichia coli to thermal, UVA, and solar disinfection.

Knowledge about the sensitivity of the test organism is essential for the evaluation of any disinfection method. In this work we show that sensitivity of Escherichia coli MG1655 to three physical stresses (mild heat, UVA light, and sunlight) that are relevant in the disinfection of drinking water with solar radiation is determined by the specific growth rate of the culture. Batch- and chemostat-cultivated cells from cultures with similar specific growth rates showed similar stress sensitivities. Generally, fast-growing cells were more sensitive to the stresses than slow-growing cells. For example, slow-growing chemostat-cultivated cells (D = 0.08 h(-1)) and stationary-phase bacteria from batch culture that were exposed to mild heat had very similar T(90) (time until 90% of the population is inactivated) values (T(90, chemostat) = 2.66 h; T(90, batch) = 2.62 h), whereas T(90) for cells growing at a mu of 0.9 h(-1) was 0.2 h. We present evidence that the stress sensitivity of E. coli is correlated with the intracellular level of the alternative sigma factor RpoS. This is also supported by the fact that E. coli rpoS mutant cells were more stress sensitive than the parent strain by factors of 4.9 (mild heat), 5.3 (UVA light), and 4.1 (sunlight). Furthermore, modeling of inactivation curves with GInaFiT revealed that the shape of inactivation curves changed depending on the specific growth rate. Inactivation curves of cells from fast-growing cultures (mu = 1.0 h(-1)) that were irradiated with UVA light showed a tailing effect, while for slow-growing cultures (mu = 0.3 h(-1)), inactivation curves with shoulders were obtained. Our findings emphasize the need for accurate reporting of specific growth rates and detailed culture conditions in disinfection studies to allow comparison of data from different studies and laboratories and sound interpretation of the data obtained.

Bacterial Proteins↗

Antiseptics and disinfectants: activity, action, and resistance.

Antiseptics and disinfectants are extensively used in hospitals and other health care settings for a variety of topical and hard-surface applications. A wide variety of active chemical agents (biocides) are found in these products, many of which have been used for hundreds of years, including alcohols, phenols, iodine, and chlorine. Most of these active agents demonstrate broad-spectrum antimicrobial activity; however, little is known about the mode of action of these agents in comparison to antibiotics. This review considers what is known about the mode of action and spectrum of activity of antiseptics and disinfectants. The widespread use of these products has prompted some speculation on the development of microbial resistance, in particular whether antibiotic resistance is induced by antiseptics or disinfectants. Known mechanisms of microbial resistance (both intrinsic and acquired) to biocides are reviewed, with emphasis on the clinical implications of these reports.

Anti-Infective Agents, Local↗

Prevention of surface-to-human transmission of rotaviruses by treatment with disinfectant spray.

A model was developed to examine the effects of disinfectants on the transmission of infectious rotavirus from a dried surface to humans. The initial experiments were designed to find a method of preserving rotavirus infectivity during drying. Culture-adapted human rotavirus (CJN strain) was dried at room temperature in different organic suspensions, including fecal matter, several laboratory media, and nonfat dry milk (NDM). Recoveries of infectious virus were then compared. Fecal matter provided little protection in this study relative to distilled water, but the other suspensions were quite protective, especially NDM, which consistently allowed recoveries of greater than 50%. When 10(3) focus-forming units of unpassaged CJN virus were dried in NDM and administered to subjects who licked the dried material, 100% (8 of 8) became infected. The effect of Lysol brand disinfectant spray (LDS) was next examined. Although NDM provided some protection against inactivation by LDS, spraying under conditions recommended by the manufacturer consistently caused the CJN virus titer to decrease greater than 5 log10. Consumption of CJN virus (10(3) focus-forming units) sprayed with LDS caused no infection in 14 subjects, whereas 13 of 14 subjects who consumed the unsprayed virus became infected (P less than 0.00001). The methods developed in this study could be used to test the effects of other disinfectants on the spread of infectious rotavirus from inanimate surfaces to humans.

Adolescent↗

Solar disinfection of water reduces diarrhoeal disease: an update.

349 Maasai children younger than 6 years old were randomised by alternate household to drink water either left in plastic bottles exposed to sunlight on the roof of the house or kept indoors (control). The trial was run in Maasai by Maasai community elders. Children drinking solar disinfected water had a significantly lower risk of severe diarrhoeal disease over 8705 two weekly follow up visits; two week period prevalence was 48.8% compared with 58.1% in controls, corresponding to an attributable fraction of 16.0%. While this reduction is modest, it was sustained over a year in free living children. It confirms solar disinfection as effective in vivo as a free, low technology, point of consumption method of improving water quality. The continuing use of solar disinfection by the community underlines the value of community participation in research.

Child, Preschool↗

Bacterial contamination of a phenolic disinfectant.

Twenty ward stock bottles of aqueous 1% Printol were examined and 17 were found to be contaminated with Alcaligenes faecalis. Organisms were present in dead space behind the plastic liners of the bottle caps, where they could have survived washing. A. faecalis was also isolated from 31 out of 34 1% Printol solutions in use in the hospital. Pseudomonas aeruginosa was grown from two samples of 1% Printol in one ward, but not from stock bottles.The minimal bactericidal concentration (M.B.C.) in aqueous solution of Hycolin, Sudol, and Stericol for A. faecalis and Ps. aeruginosa was 1 in 320. The M.B.C. of Printol for both organisms was 1 in 80. The activity of all four disinfectants was reduced in the presence of large amounts of organic matter. Sudol was the least affected. Polyethylene, of which stock bottles were made, did not reduce the activity of the disinfectants. It is suggested that, ideally, stock bottles of disinfectant diluted ready for use should be autoclaved before they are refilled.

Alcaligenes↗

Disinfection of upper gastrointestinal fibreoptic endoscopy equipment: an evaluation of a cetrimide chlorhexidine solution and glutaraldehyde.

There is little information available on the bacteriological contamination of upper gastrointestinal fibreoptic endoscopes during routine use and the effects of 'disinfecting solutions'. A bacteriological evaluation was therefore made of cleaning an endoscope and its ancillary equipment with (1) water, (2) an aqueous solution of 1% cetrimide with 0.1% chlorhexidine, and (3) activated aqueous 2% glutaraldehyde. All equipment, but particularly the endoscope itself, was found to be heavily contaminated after use with a wide variety of organisms of which 53% were Gram positive. Cleaning the endoscope and ancillary equipment with water and the cetrimide/chlorhexidine solution alone or in combination was inadequate to produce disinfection but immersion in glutaraldehyde for two minutes consistently produced sterile cultures with our sampling technique. A rapid and simple method for disinfection of endoscopic equipment is therefore recommended and we think this is especially suitable for busy endoscopy units.

Aldehydes↗

A new disinfectant.

Qualitative and quantitative tests have been carried out to assess the value of Cidex(1), a glutaraldehyde solution, as a disinfectant. Most of the tests were qualitative and were carried out in conditions as closely resembling those found in hospital practice as possible. Recently used anaesthetic equipment, catheters, and a cystoscope, which had been artificially contaminated with suspensions of Staph. aureus, Ps. pyocyanea, and Esch. coli, were used in the tests. The results show Cidex to be a useful disinfectant with a valuable potential in disinfecting hospital articles which, due to their perishable nature or the fragility of component parts, cannot be treated by physical means.

Aldehydes↗

Observations on a new disinfectant.

A disinfectant formula (Resiguard) containing picloxydine digluconate, benzalkonium chloride, and a detergent was examined for antibacterial activity. Studies in vitro with simulated organic contamination were followed by realistic in-use tests employing items of anaesthetic and urological equipment heavily infected with Pseudomonas aeruginosa and contaminated with blood. These showed that a dilution of 1/80 was reliably bactericidal to this resistant organism. It is concluded that Resiguard is a valuable disinfectant which may reliably be employed in the cleaning and disinfection of items of delicate, non-autoclavable, hospital equipment.

Anesthesia↗

Tests of disinfection by heat in a bedpan washing machine.

Tests of effectiveness of disinfection of metal and polypropylene bedpans were made in a washer fitted with a steam generator. Broth cultures of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, or Streptococcus faecalis (approximately 4 x 10(8) organisms) were sealed in lengths of capillary tubing and attached to the surface of the pans. In other tests, pans were contaminated with an artificial soil containing Str. faecalis (10(8) organisms/ml). In both series of tests, counts of surviving organisms were made at the end of the washing and disinfection cycle. The tests using capillary tubes showed that the Gram-negative bacilli were effectively killed, but not necessarily Gram-positive cocci. However, when incorporated in standard soil, Str. faecalis was killed or removed during the cycle. The results indicate that the disinfection process was effective for metal bedpans, but less so for polypropylene. Possible disadvantages and modification of the machine are suggested.

Disinfection↗

Respiratory symptoms and bronchial responsiveness among cleaning and disinfecting workers in the food industry.

OBJECTIVES: To measure the levels of exposure to nitrogen trichloride (NCl3) and aldehydes among cleaning and disinfecting workers in the atmosphere of food industry plants during cleaning and disinfecting operations, and to examine how they relate to irritant and chronic respiratory symptoms-which are indices of pulmonary function-and bronchial hyperresponsiveness (BHR) to methacholine. METHODS: 175 exposed workers (M = 149; F = 26) recruited from 17 enterprises of the food industry (8 cattle, pig, and ovine slaughterhouses, 8 fowl slaughterhouses, and 1 catering firm) and 70 non-exposed workers (M = 52; F = 18) were examined. Concentration levels of NCl3 and aldhehydes were measured by personal sampling. Symptoms were assessed by means of a questionnaire and the methacholine bronchial challenge (MBC) test using an abbreviated method. Subjects were labelled MBC+ if forced expiratory volume in one second (FEV1) fell by 20% or more. The linear dose-response slope (DRS) was calculated as the percentage fall in FEV1 at last dose divided by the total dose administered. RESULTS: 277 air samples were taken in the 17 food industry plants. For a given plant and in a given workshop, the actual concentrations of chloramines, aldehydes, and quaternary ammonium compounds were measured with personal samplers during the different steps of the procedures. For each cleaner, a total exposure index Sigma was calculated. A statistically significant concentration-response relationship was found between eye, nasal, and throat symptoms of irritation--but not chronic respiratory symptoms--and exposure levels or exposure duration. No relation was found between BHR and exposure. CONCLUSIONS: These data show that cleaning and disinfecting workers in the food industry are at risk of developing eye, nasal, and throat irritation symptoms. Although NCl3 exposure does not seem to carry a risk of developing permanent BHR, the possibility of transient BHR cannot be ruled out entirely.

Adult↗

Disinfectants in the control of small animal ringworm due to Microsporum canis.

Twelve disinfectant products or compounds were evaluated for their ability to kill Microsporum canis harvested from naturally infected material. The disinfectants were diluted to the concentration recommended for the disinfection of clean surfaces and the potency of each substance was determined by the degree to which it could be further diluted before losing its fungicidal action. Hypochlorite, benzalkonium chloride and glutaraldehyde based compounds were the most effective agents and phenolics, alcohol and anionic detergents were inadequate. Urea (10 mM) did not adversely affect the potency of any of the compounds.

Animals↗

Observations on Salmonella contamination of commercial laying farms before and after cleaning and disinfection.

Little is known about the effectiveness of the cleaning and disinfection methods in use on commercial laying farms in Great Britain. Samples were taken from poultry house structures and equipment of five cage layer flocks, five barn egg production flocks and two free-range flocks. In the free-range houses there was a decrease in Salmonella after cleaning and disinfection, although the soil in the paddocks remained contaminated. In the barn and especially the cage layer houses, significant residual contamination remained on the surfaces of buildings and equipment. Wildlife pests were also found to be carrying Salmonella in the disinfected houses and free-range paddocks.

Animals↗