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The sensitivity, on basic disinfectants, of 30 strains of bacteria isolated from disinfecting fluid used in hospitals were estimated. The sensitivity of isolated strains were compared with that of laboratory test strains.
A full continuous disinfection programme, consisting of disinfection during cleanout of poultry houses prior to placement of chickens, disinfection of the drinking water and spray disinfection of the birds during production was evaluated in broilers under experimental condition as well as under field conditions. Under controlled conditions, the experimental design consisted of three groups, two of which were control groups. Each group comprised 300 chickens. In one of the control groups, no disinfection of the pens was undertaken prior to the placement of the chickens. In the other control group, disinfection of the pens prior to placement of the birds was carried out using a glutaraldehyde-based product. In the test group, disinfection prior to placement was done. The drinking water of these birds was treated continuously and the birds were sprayed with a non-toxic disinfectant during production. Production parameters, such as growth rate, feed conversion ratio and feed consumption, of the birds in the three groups were monitored. In addition, all mortalities in the different groups were recorded and classified into diseases of an infectious nature, non-infectious nature and unknown category. Bacterial counts were also done on a weekly basis from the different pens. In this experiment, it was shown that the full continuous disinfection programme resulted in a lower number of mortalities caused by infectious agents as well as a reduction in the bacterial counts in the pens treated with the full continual disinfection programme. The full continuous disinfection programme was also tested on a commercial poultry farm in the Northern Cape Province of South Africa. Two production houses of 3,500 birds were randomly selected as test houses for the full continuous disinfection programme. Another similar house, which received day-old chicks from the same batch as the other two houses, was selected as the control house; it received the routine disinfection procedure prior to placement of the chicks. During the course of this experiment, a severe outbreak of Newcastle disease was experienced on this farm. It was demonstrated that, in the face of this severe challenge, the full continuous disinfection programme controlled the spread of the disease in both the houses where it had been applied at a stage when in every other house (including the control house) on the farm birds were suffering very high mortalities.
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The antimicrobial activities of three non-peroxide soft contact lens chemical disinfection systems--ReNu Multi-Purpose Solution (0.00005% polyaminopropyl biguanide), Opti-Soft Disinfecting Solution (0.001% polyquaternium-1), and Opti-Free Rinsing, Disinfecting & Storage Solution (0.001% polyquaternium-1)--were compared to Soft Mate Disinfecting Solution (0.005% chlorhexidine digluconate). Each product was separately inoculated with each of five microorganisms at approximately 10(6) microorganisms per mL. All of the solutions demonstrated excellent disinfecting activity against Pseudomonas aeruginosa and Staphylococcus epidermidis, with complete disinfection occurring within 4 hours. Only Soft Mate disinfected Serratia marcescens within 4 hours. ReNu reduced the microorganisms to 10-100 cells/mL and Opti-Soft and Opti-Free reduced the number to 10(2)-10(3) cells/mL. For the fungal species, Soft Mate showed excellent activity against Candida albicans (disinfection in 4 hours) and reduced Aspergillus fumigatus to 10(3) spores/mL in 4 hours. After 4 hours ReNu, Opti-Soft, and Opti-Free had reduced C. albicans only slightly, to 10(5) cells/mL and displayed virtually no disinfecting activity against A. fumigatus. For these newer chemical disinfection systems, diligent cleaning and rinsing of the soft contact lenses are the most important steps in the patient care regimen.
UNLABELLED: Gastrointestinal endoscopy can lead to infectious complications, and endoscopes must be disinfected to prevent them. AIM: to evaluate three methods of disinfection: 1) usual cleaning technique and immersion in glutaraldehyde phenolate (GP); 2) meticulous cleaning and immersion in GP, and 3) meticulous cleaning and immersion in hydrogen peroxide. METHOD: thirty endoscopes (15 gastroscopes and 15 colonoscopes) were disinfected with each method. Samples were taken following endoscopic exploration, after cleaning and after disinfection, and were cultured. The number of positive culture (cfu/ml > 1) was counted. RESULTS: the rate of contamination of endoscopes did not decrease significantly after cleaning with method 1 (66 vs 60%), but did decrease with method 2 (38 vs 16%) and method 3 (53 vs 17%). The contamination rate after cleaning was significantly lower with methods 2 and 3 (p < 0.005). This rate was also lower after disinfection (p < 0.025). Method 3 achieved 0% contamination following disinfection. CONCLUSIONS: the greatest decrease in contamination rate was achieved with conscientious cleaning followed by disinfection. Both disinfectants yielded similar results, although hydrogen peroxide produced a higher level of disinfection.
Robert Kochs studies on disinfection are distinguished by well defined, clear experimental arrangement and commitment to practice. He investigated the effectiveness of disinfection by following recultivation tests in vitro and in animal experiments. He examined chemical substances of different origin, the action of hot air and superheated steam with a spectrum of microorganisms, including bacterial spores. Priorities of the recent development in disinfection are among other things the application of steam disinfectors and of chemical disinfectants in the gas-phase e.g. for disinfection of tubes, the use of combinations of tensides with disinfectants, of disinfectants effective against spores of clostridium and against hepatitis viruses, of disinfectants with low corrosiveness and low toxicity against men and domestic animals. Disinfection is a component of a system of measures in antimicrobial regimes and in protective systems.
The effect of steam on sandpit disinfection was investigated by supplying steam into sandpits covered with a sheet cover. To evaluate the effect, total number of viable bacteria, number of aerobic sporeforming bacteria, coliforms and fecal coliforms were measured four weeks before, just before, immediately after, two and four weeks after the disinfection. Disinfection of coliforms and fecal coliforms was accomplished when temperature of sand reached more than 60 degrees C. Total number of viable bacteria and number of aerobic sporeforming bacteria also reduced by disinfection with steam. However, after 2 and 4 weeks of disinfection, number of coliforms and fecal coliforms recovered to the same level before disinfection, and total viable count also restored its number. In addition, a significant increase in the number of aerobic sporeforming bacteria was noted both after 2 and 4 weeks of disinfection. These results indicate that the effect of steam disinfection in transient and can not be used for the routine method of disinfection in sandpit.
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Since 1965, besides the use of scrubbing disinfectants, a number of alcoholic handrub methods are employed in the surgical skin disinfection of the hands. These contain, in addition to the alcohols, substances such as phenols and among others, cation-active substances. The efficacy of the substances is examined by means of in vitro-tests and through investigations conducted under conditions approximating those in the practice in accordance with the guidelines set down by the German Society of Hygiene and Microbiology. The comparison between the alcohol-containing handrub disinfectants and the scrubbing methods indicates clearly that the latter achieve only a low germ-reduction effect. The investigation on 4 alcoholic handrub disinfectants showed an initial potent germ-reducing and a good long-term effect. When mechanical scrubbing of the hands is carried out in a timely relationship to the application of the handrub -method, it is found to be able to produce extensive dermal damages. The reduction in the transient microbial flora by means of the mechanical hand scrubbing is minimal. The study on the germ-reduction after surgical disinfection of the hands using alcoholic handrub disinfectants in combination with and without initial soap-scrubbing demonstrated no differences, neither in the number of sterile hands nor in the averages of germ-reduction. The investigations conducted confirmed the excellent efficacy of the alcoholic handrub disinfectants and pointed out that it is unnecessary to combine mechanical hand scrubbing and the employment of alcoholic disinfectants in the same process.
The disinfectant solutions Dettox (based on a quaternary ammonium compound) and Gigasept (based on succine dialdehyde) were evaluated during disinfection procedures with a new disinfecting apparatus for gastrointestinal fibrescopes. Thorough disinfection was achieved after 2 minutes using Dettox 8% or Gigasept 10%; persistent fibrescope contamination with Gram-negative organisms was found after disinfection with Dettox 4% or Gigasep 5%. No adverse effects in endoscopy staff or damage to fibrescopes were seen. Adequate disinfection of endoscopic equipment prevents endoscopy-related infection and can be readily achieved by trained endoscopy staff using rapidly bactericidal disinfectants.
The aims of this research were to study the influence of peracetic acid (PAA) on the formation of mutagens in surface waters used for human consumption and to assess its potential application for the disinfection of drinking water. The results obtained using PAA were compared to those found with sodium hypochlorite (NaClO) and chlorine dioxide (ClO2). The Ames test, root anaphase aberration assay, and root/micronuclei assay in Allium cepa and Tradescantia/micronuclei test were used to evaluate the mutagenicity of disinfected samples. Microbiological tests were also performed, and disinfection by-products (DBPs) were identified using gas chromatography/mass spectrometry (GC/MS). A slight bacterial mutagenicity was found in raw lake and river water, and similar activity was detected in disinfected samples. A plant test revealed genotoxicity in raw river water, and microbiological analysis showed that PAA has bactericidal activity but lower than that of the other disinfectants. The DBPs produced by PAA were mainly carboxylic acids, which are not recognized as mutagenic, whereas the waters treated with the other disinfectants showed the presence of mutagenic/carcinogenic halogenated DBPs. However, additional experiments should be performed with higher concentrations of PAA and using water with higher organic carbon content to better evaluate this disinfectant.
The intention of investigations was to clear central problems of disinfecting testing in carrier model. Ways of practical and standardized evaluation should be found out. Concrete investigations were made to guarantee a highly and regularly initial bacterial count, practical germ carriers and organic matter as also detecting damaged bacteria. Investigations for resistance level of test organisms were made in suspension test with formaldehyde as reference disinfectant. It was obviously that test organisms used in disinfecting testing were after 8 weeks more sensitive against disinfectants. Therefore results of disinfecting testing are often no representative because those test organisms are not qualified for representative declaration of disinfectant efficiency. Animal passage in distance of 8 weeks is a possibility for guaranteeing highly and regularly resistance of microorganisms We recommend to use soft wood from the same origin, addition of 10% horse serum and 1% carboxymethylcellulose as organic matter for a model relating to practice. Buffered peptone water and nutrient agar are guarantee for detecting damaged bacteria after disinfecting.
Following a former suggestion (4) always to evaluate, the efficacy of procedures for Hygienic disinfection of hands in comparison with the results of a certain standard disinfection method, Ethanol, iso- and n-Propanol were tested in various concentrations and for various times of action on their usability in such a standard method. The disinfecting power was dependent upon (i) the alcohol (Ethanol less than iso-Propanol less than n-Propanol), (ii) the concentration (Ethanol: 60 less than 70 less than 80% ml/ml, iso-Propanol: 50 less than 60 less than 70, n-Propanol: 40 less than 50 less than 60 = 70) and (iii) the time of action (0,5 less than 1 less than 2 min). n-Propanol proved to be the fastest acting disinfectant. However, as standard disinfection method iso-Propanol (60% ml/ml) being used for 1 min has been proposed. Furthermore, the following results that have been obtained also in former investigations (8) could be confirmed: (i) there is no systematic difference between the release of test-bacteria from the fingertips of right and left hands of test-persons (ii). The efficacy of procedures for Hygienic disinfection of hands is besides other factors influenced by the testpersons. This factor may be eliminated by using the same testpersons for both, the disinfection procedure under investigation and the standard method. The results of both may, then, be related to each other and the efficacy of the former may be evaluated in comparison to the latter.
Skin allografts, derived from cadaveric donors, are widely used for the treatment of burns and ulcers. Prior to use in clinical situations, these allografts are disinfected using a cocktail of antibiotics and then cryopreserved. Unfortunately, this antibiotic disinfection procedure fails to decontaminate a significant proportion and these contaminated grafts can not be used clinically. We have investigated whether it is possible to apply a second, more potent disinfection procedure to these contaminated grafts and effectively to re-process them for clinical use. Cadaveric skin grafts, treated with antibiotics and cryopreserved, were thawed and a peracetic acid (PAA) disinfection protocol applied. The grafts were then preserved in a high concentration of glycerol or propylene glycol, and properties thought to be essential for successful clinical performance assessed. The cytotoxicity of the grafts was assessed using both extract and contact assays; damage to the skin collagen was assessed using a collagenase susceptibility assay and the capacity of the grafts to elicit an inflammatory response in vitro was assessed by quantifying the production of the pro-inflammatory cytokine TNF-alpha by human peripheral blood mononuclear phagocytes. PAA disinfection, in conjunction with either glycerol or propylene glycol preservation, did not render the grafts cytotoxic, pro-inflammatory, or increase their susceptibility to collagenase digestion. The rates of penetration of glycerol and propylene glycol into the re-processed skin were comparable to those of fresh skin. This study has demonstrated that PAA disinfection combined with immersion in high concentrations of either glycerol or propylene glycol was an effective method for re-processing contaminated skin allografts, and may justify their clinical use.
In hospitals, one of the ways to control microbial contamination is by disinfecting the furniture used by patients. This study's main objective was to evaluate the microbiological condition of hospital mattresses before and after such disinfection, in order to identify bacteria that are epidemiologically important in nosocomial infection, such as Staphylococcus aureus and Pseudomonas aeruginosa. RODAC plates with two different culture media were used to collect specimens. Patient beds were selected according to previously established criteria, and surface areas on the mattresses were chosen at random. From the total of 1,040 plate cultures from 52 mattresses, positive results were obtained from 500 of them (48.1%), 263 before disinfection and 237 after disinfection. Considering the selectivity of the culture media, the positivity rate was high. There were high prevalences of S. aureus both before and after mattress disinfection. The study results suggest that the usual disinfection procedures, instead of diminishing the number of microbes, merely displace them from one part of the mattress to another, and the number of microorganisms remains the same.
The Montreal Urban Community Wastewater Treatment Plant (MUCWTP) located in Montreal. Quebec, Canada, uses physicochemical treatment processes prior to discharging wastewater into the St. Lawrence River via an outfall tunnel of 2 hours retention time. Although chlorination facilities exist, they are not being used, and the MUCWTP is seeking alternative methods for disinfection to achieve a 2- to 3-log fecal coliform reduction. Liquid chemical disinfectants were attractive options because of their low capital costs. This led to an investigation of the feasibility of using hydrogen peroxide or peracetic acid. A method for measuring peroxycompounds (hydrogen peroxide or peracetic acid plus hydrogen peroxide) was developed using the peroxidase-based oxidation of 2,2'-azino-bis(3-ethylbenz-thiazoline-6-sulfuric acid) diammonium salt (ABTS) with hydrogen peroxide. The validity of the method was confirmed using effluent from the MUCWTP. Recovery was higher than 90% for peracetic acid levels as low as 1.0 mg/L. Quenching of hydrogen peroxide was achieved with 50-mg/L catalase; quenching of peracetic acid was achieved with 100 mg/L of sodium thiosulfate, followed by 50 mg/L of catalase. Batch disinfection tests were conducted on MUCWTP effluent. Hydrogen peroxide and peracetic acid in wastewater over time could be modeled as a second-order decay, with the decay "constant" being a function of the initial concentration of peroxycompounds. This function was the same for both hydrogen peroxide and peracetic acid, possibly indicating similar decomposition pathways in wastewater matrices. Disinfection was modeled using a modified Hom equation. Required doses of hydrogen peroxide to reach the target fecal coliform levels ranged from 106 to 285 mg/L, with the higher doses occurring when ferric chloride instead of alum was used as the coagulant. Hence, hydrogen peroxide was infeasible as a disinfectant for this application. On the other hand, the peracetic acid dose needed to achieve the target fecal coliform level was only 0.6 to 1.6 mg/L. Therefore, peracetic acid seems to be a promising disinfectant for physicochemical or primary effluent, or combined sewer overflows.