Comparative mycobactericidal efficacy of chemical disinfectants in suspension and carrier tests

The efficacy of nine disinfectants on Mycobacterium smegmatis was tested in the presence of sputum, using quantitative suspension and carrier tests. Glutaraldehyde, povidone iodine, and chlorhexidine gluconate produced at least a 6-log10 reduction in CFU in all tests. Four disinfectants (sodium dichloroisocyanurate, phenol, ethanol, and sodium hypochlorite) were not as effective in the carrier tests as in the suspension tests; this difference ranged from a 1- to a 5-log10 reduction in CFU. The efficacy of ethanol and sodium hypochlorite was further reduced (3- and 1-log10 reductions in CFU, respectively) in the presence of sputum. The quaternary ammonium compound and iodophor were ineffective in all tests. The findings of this study demonstrate the need for a quantitative carrier test such as the one presented here.     

A suspension method to determine reuse life of chemical disinfectants during clinical use.

In-use testing of disinfectants is necessary to ensure efficacy over time. The current official procedure for testing disinfectants, the Association of Official Analytical Chemists (AOAC) use-dilution method, cannot be adapted to repeated sampling techniques of use-life testing. It is therefore necessary to use an alternative method when evaluating the activity of a disinfectant under actual use. The Clinical Research Associates (CRA) suspension method was developed to fill this need. It consists of adding 0.5 ml of a standard culture to 5.0 ml of test disinfectant and sampling the mixture after 10 min for surviving bacteria. When this test was compared with the AOAC use-dilution method under a simulated use situation, the two methods were generally equivalent in identifying disinfectant inactivation. In addition, the CRA method was less time consuming, easier to perform, and less variable than the AOAC method. Use of the CRA method in a clinical study demonstrated the need for reuse claims to be based on clinical use studies rather than on laboratory testing only.     

A suspension method to determine reuse life of chemical disinfectants during clinical use

In-use testing of disinfectants is necessary to ensure efficacy over time. The current official procedure for testing disinfectants, the Association of Official Analytical Chemists (AOAC) use-dilution method, cannot be adapted to repeated sampling techniques of use-life testing. It is therefore necessary to use an alternative method when evaluating the activity of a disinfectant under actual use. The Clinical Research Associates (CRA) suspension method was developed to fill this need. It consists of adding 0.5 ml of a standard culture to 5.0 ml of test disinfectant and sampling the mixture after 10 min for surviving bacteria. When this test was compared with the AOAC use-dilution method under a simulated use situation, the two methods were generally equivalent in identifying disinfectant inactivation. In addition, the CRA method was less time consuming, easier to perform, and less variable than the AOAC method. Use of the CRA method in a clinical study demonstrated the need for reuse claims to be based on clinical use studies rather than on laboratory testing only.     

Heterogeneity in the efficacy of dental chemical disinfectants on water-derived biofilms in vitro

Abstract

Conditions in dental unit waterlines are favourable for biofilm growth and contamination of dental unit water. The aim of this study was to assess the effect of several chemical disinfectants on bacteria in a biofilm model. Water-derived biofilms were grown in a static biofilm model (Amsterdam Active Attachment model), using two growth media. Biofilms were challenged with Alpron/Bilpron, Anoxyl, Citrisil, Dentosept, Green & Clean, ICX and Oxygenal in shock dose and maintenance doses. The concentration and the composition of the chemical disinfectants influenced the number of culturable bacteria in the biofilms. The application of a single shock dose followed by a low dose of the same chemical disinfectants resulted in the greatest suppression of viable bacteria in the biofilms. Exposure to Citrisil and ICX consistently resulted in failure to control the biofilms, while Alpron/Bilpron had a substantial and relevant effect on the number of bacteria in the biofilms.     

Comparative evaluation of biofilm disinfectant efficacy tests

Regulatory agencies are receiving registration applications for unprecedented, antibiofilm label claims for disinfectants. Reliable, practical, and relevant laboratory biofilm test methods are required to support such claims. This investigation describes the influence of fluid dynamics on the relevancy of a laboratory test. Several disinfectant formulations were tested using three different biofilm testing systems run side-by-side: the CDC biofilm reactor system that created turbulent flow (Reynolds number between 800 and 1850), the drip flow biofilm reactor system that created slow laminar flow (Reynolds number between 12 and 20), and the static biofilm system that involved no fluid flow. Each comparative experiment also included a dried surface carrier test and a dried biofilm test. All five disinfectant tests used glass coupons and followed the same steps for treatment, neutralization, viable cell counting, and calculating the log reduction (LR). Three different disinfectants, chlorine, a quaternary ammonium compound, and a phenolic, were each applied at two concentrations. Experiments were conducted separately with Pseudomonas aeruginosa and Staphylococcus aureus and every experiment was independently repeated. The results showed that biofilm grown in the CDC reactor produced the smallest LR, the static biofilm produced the largest LR, and biofilm grown in the drip flow reactor produced an intermediate LR. The differences were large enough to be of practical importance. The dried surface test often produced a significantly higher LR than the tests against hydrated or dried biofilm. The dried biofilm test produced LR values similar to those for the corresponding hydrated biofilm test. These results show that the efficacy of a disinfectant must be measured by using a laboratory method where biofilm is grown under fluid flow conditions similar to the environment where the disinfectant will be applied.     

The relationship between the chemical structure of fatty acids and their mycobactericidal activity.

The bactericidal activity of long-chain fatty acids on mycobacteria was examined by exposing the organisms to these acids at 0.04 mM in 0.05 M acetate buffer (pH 5.6). The lethal effect of saturated fatty acids was related to the chain-length of hydrocarbon, C14:0 being the strongest in the activity and longer and shorter fatty acids being less active. Unsaturation, isomerism and the presence of alpha-hydroxy group were found to be other factors governing the activity. The lethal effect was greater in the order of C18:3 greater than C18:2 greater than C18:1(cis) greater than C18:1(trans) greater than alpha-OH C18:0 greater than C18:0. C20:4 was placed between C18:3 and C18:2 in this respect. Esterification of C14:0, C18:1 and C20:4 to methyl esters and cholesteryl esters abolished completely the bactericidal activity of these acids, suggesting the requirement of carboxyl group for the activity. The relationship between the fatty acid structure and the lethal effect was discussed in reference to these observations.     

Comparative testing and evaluation of hard-surface disinfectants

Summary The activity of eleven disinfectants againstStaphylococcus aureus, Pseudomonas aeruginosa, andSaccharomyces cerevisiae was determined using a method based on the A.O.A.C. germicidal and detergent sanitizer assay. Based on the activity against the test organisms after 30-and 60-s exposures to each disinfectant, the disinfectant containing chlorine dioxide had the highest biocidal activity in this assay, on a mg/l basis. In addition, a disinfectant containing sodium hypochlorite and a disinfectant containing sodium chlorite performed well, at concentrations below label specifications. The results illustrate the importance of testing disinfectants in the context of their intended use.     

Comparative efficacy of antigen and antibody detection tests for human trichinellosis

Sera collected from patients with suspected or confirmed exposure to Trichinella spiralis were tested for circulating parasite antigens and antiparasite antibodies. Using an immunoradiometric assay, excretory--secretory antigens from muscle-stage larvae of T. spiralis were detected in the sera of 47% of 62 patients with clinical trichinellosis and 13% of 39 patients without clinical signs but suspected of exposure to infected meat. In comparison, antibodies were detected using an indirect immunofluorescent test in the circulation of 100% of the 62 patients with clinical trichinellosis and 46% of the 39 patients with suspected exposure. The presence of antibodies specific to excretory-secretory products of T. spiralis muscle larvae was confirmed in the majority of the samples tested by a monoclonal antibody-based competitive inhibition assay. These results indicate that antibody detection is a more sensitive diagnostic method for human trichinellosis, but that antigen detection might be a useful confirmatory test because it is a direct demonstration of parasite products in the circulation.     

Evaluation of the efficacy of chemical disinfectants for disinfection of heat‐polymerised acrylic resin

doi: 10.1111/j.1741‐2358.2010.00400.x
Evaluation of the efficacy of chemical disinfectants for disinfection of heat‐polymerised acrylic resin Objective: This study evaluated the efficacy of disinfectants on the internal aspect of heat‐polymerised acrylic resin contaminated with microbial strains. Background: Dentures absorb oral fluids and become contaminated by different microorganisms. Methods: Two hundred and fifty rectangular specimens were made of heat‐polymerised acrylic resin, and then divided into five groups corresponding to the microbial strains (Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, S. mutans and Enterococcus faecalis). After contamination, the specimens were immersed in 1 and 2% sodium hypochlorite and 2% glutaraldehyde for periods of 5, 10 and 15 min. The specimens were placed into tubes containing different broths and incubated at 35°C and then visually analysed. Turbidity in the medium indicated microbial growth. The Fisher’s exact test was used in the analysis of the results. Results: The strain E. faecalis was the most resistant to the disinfectant solutions, and among them, glutaraldehyde was more effective than 2 and 1% hypochlorite for disinfection for 5 min; in the 10‐min period there were no differences between the disinfectants. In 15 min of immersion, 1% hypochlorite and glutaraldehyde were more effective than 2% hypochlorite. Conclusions: Disinfection for 10 min with 1% hypochlorite and glutaraldehyde is effective in disinfecting the internal aspect of heat‐polymerised acrylic resin.     

Efficacy of chemical disinfectants against snakehead rhabdovirus

The susceptibility of snakehead rhabdovirus to treatment at 20°C with 5 commercially available disinfectants was examined. No reduction in virus infectivity occurred following exposure to 5 ppm malachite green for 6 hours. Treatment of infective cell culture fluids with 2% formalin resulted in > 99.9% reduction in virus titre within 5 minutes and complete inactivation within 30 minutes, but a negligible loss in infectivity after exposure to 0.025% formalin for 1 hour. Suspensions of virus in distilled water were completely inactivated within 5 minutes by 12.5 ppm chlorine, 50 ppm iodine, or a 1:2000 dilution of a peroxygen disinfectant. In the presence of serum in infective cell culture fluids, however, > 50 ppm chlorine was required to inactivate the agent and no measurable reduction in infectivity was observed following treatment with 500 ppm iodine for 30 minutes.     

Assessment of the efficacy of disinfectants on surfaces

The Literature on testing the efficacy of disinfectants covers a century. Most predominant and standardized are the so called suspension tests that allow for the quantitative estimation of the microbicidal activity (log reduction factors) of disinfectants on test organisms suspended in solutions of these products.Since the outcome of suspension tests might be a poor predictor for the efficacy of a disinfectant under practical circumstances, especially with regard to bacteria attached to surfaces, a variety of test procedures have been designed to mimic those conditions. Within the framework of CEN/TC 216 a quantitative surface test has been developed to assess the activity of disinfectants on bacteria or fungi attached to steenless steel surfaces. Preliminary data suggest that covering a dried inoculum with disinfectant without any further mechanical action to improve contact between organisms and disinfectant, will usually result in lower reduction factors than those obtained with suspension tests. Comparative testing further suggests that by applying mechanical action, with the effect of resuspending cells in the liquid on the surface,—similar to mopping, brushing etc.— will result in higher reduction rates. Although not unexpected these findings emphasize the importance of designing test methods based on practical applications of disinfectants.     

Rotavirus inactivation by chemical disinfectants and antiseptics used in hospitals

Nosocomial outbreaks of rotaviral gastroenteritis are a common occurrence. Although proper disinfection practices in the hospital environment are considered to be important in the prevention and control of such outbreaks, very little information has been available on the rotavirus-inactivating capacity of chemical disinfectants and antiseptics commonly used in hospitals. In view of this, 11 such products were selected and screened for their capacity to bring about at least a 3 log10 reduction in the plaque titre of rotavirus SA-11 after a contact time of 1-30 min. Consept "D" (1:100), D.R.X. (1:80), Dustbane Germicidal (1:80), Hibitane, and Wescodyne (1:200) were found to be ineffective under these test conditions even in the absence of an added organic load. The virucidal capacity of Savlon (1:200) and Zephiran was completely neutralized when single-strength tryptose phosphate broth was added to the virus-disinfectant mixture to simulate an organic load. Cidex (2% acid glutaraldehyde), Proviodine (10% solution of povidone-iodine), Septisol (0.75% hexachlorophene), and Sana Rinse (70% isopropylalcohol, 0.1% hexachlorophene) were able to produce at least a 3 log10 (99.9%) reduction in the virus plaque titre even in the presence of added organic matter. These findings should be of help in the prevention and control of outbreaks of rotaviral diarrhea in the hospital environment.     

Evaluation of the repeatability and reproducibility of European suspension test methods for antimicrobial activity of disinfectants and antiseptics.

A collaborative study to determine the precision of the 1987 Method of test for the antimicrobial activity of disinfectants in food hygiene is described. The repeatability and reproducibility of the test was found to vary according to the nature of the test organism, the type of disinfectant product and the skill of the operator. Results indicate that significant differences in microbicidal effect (ME values) occur within test laboratories between test periods as well as between laboratories, and that much of this variability derives from apparently random variations in the resistance of test strains from day to day and test period to test period. Indications are that although the test is sufficiently reliable to be used as a standard method, adequate test replication must be specified to distinguish borderline pass from borderline fail disinfectant concentrations. The implications of the results in relation to current work on the development of unified European test methods for disinfectants is discussed.     

Inactivation of Bacillus piliformis spores by heat and certain chemical disinfectants

The inactivation of Tyzzer's organism (Bacillus piliformis) spore isolated from rats by heat and various chemical disinfectants was studied. The spores were from B. piliformis-infected rat liver tissues. The spore suspension (10(4) 50% of rat liver lesion producing dose with prednisolone treatment/ml) was treated with heart or disinfectants. Inactivation of the spores was examined in experimentally infected rats. Rats were inoculated perorally with a treated spore suspension and injected subcutaneously with prednisolone. On the sixth day after inoculation, rats were examined grossly for liver lesions. Spores were inactivated at 80 degrees C for 15 min but not at 60 degrees C for 30 min. Spores were inactivated by 0.4% peracetic acid, 0.015% sodium hypochrolite, 1% iodophol, 5% phenol. Alcide and 0.37% formaldehyde solution, but not by 0.037% formaldehyde solution, 70% ethanol, 0.3% benzethonium chloride solution, 3% cresol and soap solution, or 4% chlorhexidine digluconate. These findings suggest that B. piliformis spores are relatively sensitive to heat and certain chemical disinfectants.     

The fungicidal efficacy of various commercial disinfectants used in the food industry

The antifungal effects of eight commercial disinfectants namely alcohol, peracetic acid, iodophors, aldehydes, quaternary amine compounds (QAC, a, b and c), and a chlorine-based agent were assessed at different concentrations. The time taken for these disinfectants to kill different microorganisms was used to assess their efficacy. The microorganisms tested were six yeasts,Saccharomyces cerevisiae, Saccharomyces uvarum, Kloeckera apiculata, Candida oleophila, Metschnikowia fructicola, Schizosaccharomyces pombe, and two moulds,Aspergillus niger (5 strains) andPenicillium roqueforti (5 strains). The disinfectants QAC (a) and QAC (c) were the most effective against all the microorganisms tested. The chlorine-based disinfectant worked most efficiently against the moulds at all concentrations used (0.5, 1.0, 1.5 and 2.0%). Peracetic acid and alcohol based disinfectants were most effective against the yeasts than mould. Tested yeasts were more resistant to the aldehyde and iodophors base disinfectants than the others.     

Diagnostic efficacy of screening tests for hereditary hemochromatosis.

Hereditary hemochromatosis is transmitted as an autosomal recessive trait. Analyses of pedigrees suggest that the frequency of disease (proportion of homozygous individuals) in the general population is approximately 0.3% and that approximately 11% of the population are heterozygous. The genotype of 194 persons in 38 pedigrees was determined by HLA-A and HLA-B haplotyping. Likelihood analysis was then used to appraise the transferrin saturation test when used alone and in combination with the serum ferritin test to detect homozygosity and heterozygosity in these pedigrees. A single cut-off point of 55% for transferrin saturation and a cut-off point at the 90th percentile for the serum ferritin level were adequate for the detection of hemochromatosis if homozygosity was considered to be present when the results of one or both tests were positive. To further assess the value of the transferrin saturation test the percentages were stratified into five intervals. A percentage transferrin saturation of 75 or greater and a serum ferritin level above the 90th percentile ruled in homozygosity, whereas a percentage transferrin saturation of less than 55 and a serum ferritin level at or below the 90th percentile ruled it out with confidence. The probability of heterozygosity rose to 90% when the percentage transferrin saturation was between 35 and 55 and the serum ferritin level was at or below the 90th percentile. The use of five cut-off points allowed the probability of homozygosity and heterozygosity in a pedigree to be estimated for all values of transferrin saturation. Although these screening tests are not recommended for use in the general population, they may be worth while in selected groups of patients.     

Evaluation of efficacy of disinfectants against Salmonella from the feed industry

Aims:  To evaluate disinfectants against Salmonella under conditions relevant for the feed industry.
Materials and Results:  A survey on the use of disinfectants in feed industry showed that a range of different types was used. Nine disinfectants, reflecting the most commonly used active ingredients, were tested for bactericidal activity on Salmonella isolated from the feed industry. All disinfectants were efficient against Salmonella in suspension. The bactericidal effect varied considerably between different types of active compounds on bacteria dried on surfaces or grown as biofilm. Tenside-based disinfectants and hypochlorite were found to have low bactericidal activity and the efficiency was significantly reduced when the ratio of amount disinfectant per cell decreased. It was shown that concentrations of 70–80% ethanol were effective against Salmonella. Among the disinfectants tested a product containing 70% ethanol was most efficient followed by Virkon S.
Conclusions:  Many disinfectants had low bactericidal activity against Salmonella at surfaces while Virkon S and a product containing 70% ethanol were most effective. Another advantage of ethanol-based disinfectants is evaporation of ethanol, resulting in low residual water after use.
Significance and Impact of the Study:  Use of the disinfectants found to be efficient against surface associated Salmonella , may assist the industry in combating Salmonella .