Evaluation of disinfectant
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The document outlines various methods used to test the efficacy of disinfectants, including carrier tests, suspension tests, and practical tests. Carrier tests involve contaminating a thread with bacteria and exposing it to disinfectants. Suspension tests measure a disinfectant's ability to kill bacteria suspended in its solution. Practical tests evaluate disinfectants under real-world conditions. The document also describes the phenol coefficient test, which compares a disinfectant's effectiveness to that of phenol, and the filter paper test, which detects zones of bacterial inhibition around treated disks.
Evaluation of disinfectant
- 1. EVALUATION OF DISINFECTANTS PRESENTATION BY GROUP H1
- 2. OUTLINE OF PRESENTATION HISTORY INTRODUCTION CLASSES OF DISINFECTANTS METHOD FOR TESTING DISINFECTANTS CARRIER TEST CAPACITY TEST SUSPENSION TESTS PRACTICAL TEST IN USE TEST EVALUATION OF OTHER DISINFECTANTS EVALUATION OF PRESERVATIVES CONCLUSION 2
- 3. HISTORY Robert Koch described a disinfectant test in the article Uber Disinfektion, in 1881. Used a liquid culture of Bacillus anthracis for testing disinfectants. He used a silk thread contaminated in liquid culture and dried it. Immersed in several disinfectants and cultured in nutrient broth &incubated . 1.Growth occur – less effective disinfectants . 2. No Growth occur – more effective disinfectants . 3
- 4. INTRODUCTION Testing of disinfectant is a complex process. This is used to test the efficacy of disinfectant. Regulated by two different federal agencies U. S. environment protection assay-regulates disinfectants. Food &drug administration –regulates disinfectants used on human & animals . Disinfectants are used mainly in hospital & labs, so periodically effectiveness of disinfectant is checked. 4
- 5. INTRODUCTION CNT’D Some common terms: Disinfectant Disinfection Antiseptic Antisepsis Preservatives 5
- 6. CLASSES OF DISINFECTANT Halogens eg iodine Acids and alkalis Phenols Alcohols Aldehydes Hydroxy acids and their esters Dyes Metals and their salts 6
- 7. PROPERTIES OF AN IDEAL DISINFECTANT Must be fast acting Effective against most infectious agents Easy penetration without altering material Must be stable to light and heat etc Easy to prepare Inexpensive and easy to obtain Not have an unpleasant odour 7
- 8. It must be noted, however, that no disinfectant is likely to satisfy all these criteria. An agent that meets the greatest number of these properties is selected for use. 8
- 9. FACTORS AFFECTING ANTIMICROBIAL ACTIVITY OF DISINFECTANTS Innate resistance of microbes Microbial density Disinfectant concentration and exposure time Physical and chemical factors Presence of extraneous(foreign) organic matter 9
- 10. WHAT IS EVALUATION OF DISINFECTANT? The process of establishing documented evidence that a disinfectant will consistently remove or inactivate known or possible pathogens from samples. 10
- 11. WHY EVALUATE DISINFECTANTS??? May lose potency on standing May also lose potency on addition of organic matter Are required in critical ares like hospitals and labs Hence the efficacy must be tested. 11
- 12. METHOD FOR EVALUATION DISINFECTANTS There are several methods for testing disinfectants. Each method has its own advantages and limitations. Different methods grouped into: Carrier Test Suspension Test Capacity Test Practical Test Field Test (In-use test) 12
- 13. CARRIER TEST This is the oldest test. R. Koch’s Test for example was a carrier test. S. aureus bacteria culture is used. 1.Growth occur – less or ineffective disinfectants . 2. No Growth occur – more effective disinfectants This test can be used for liquid disinfectants. 13
- 14. LIMITATIONS OF CARRIER TEST Difficulty in standardizing number of bacteria dried on carrier. Survival of bacteria on carrier during drying is not constant. 14
- 15. CAPACITY TEST This test determines the capacity of the disinfectant to retain it’s activity in the presence of increasing contamination load Bacterial suspension added until disinfectant capacity to kill is exhausted. This test simulates practical situations of housekeeping and instrument disinfection. Best known capacity test is Kelsey-Sykes test 15
- 16. KELSEY-SYKES TEST It is a triple challenged test Three successive additions of bacterial suspensions are made The test takes over 30mins to perform The test can be done under clean or dirty conditions 16
- 17. 17
- 18. Advantage It gives a good guideline for the dilution of the preparation to be used Disadvantage It is a complicated test 18
- 19. TEST FOR STABILITY AND LONG TERM EFFECTIVENSS Kelsey-syke test apply only to freshly prepared disinfectant solution Solutions to be kept for more that 24 hours require supplementary stability test at their particular concentrations. P. aeruginosa is used as test organism 19
- 20. Two portions of disinfectant solution are prepared for two tests One portion is inoculated immediately and tested for growth after holding for 7 days at room temperature. Other portion is kept at room temperature for 7 days, then inoculated with freshly prepared suspension of test organism and also tested for growth after 7 days 20
- 21. If growth is detected, a higher concentration of disinfectant is tested in the same way 21
- 22. SUSPENSION TEST A sample of bacterial culture is suspended into the disinfectant solution. After exposure , it is verified by subculture of bacterial culture . After subculture :- 1.Growth occur – less effective disinfectants . 2. No Growth occur – more effective disinfectants . Suspension tests are preferred to carrier test. This is because the bacteria are uniformly exposed to the disinfectant 22
- 23. TYPES OF SUSPENSION TEST Qualitative suspension test Quantitative suspension test Phenol coefficient test 23
- 24. PHENOL COEFFICIENT TEST This method is used for evaluating the effectiveness of disinfectants . Best known disinfectant test. Staphylococcus aureus or Salmonella typhi are used for testing . Dilution of phenol &experimental disinfectant are inoculated with Staphylococcus aureus &incubated at 20-37˚C for 2-3 days. Calculated by dividing dilution of test disinfectant by the dilution of phenol that disinfect under specified conditions. 24
- 25. Two main methods under phenol coefficient test. Rideal Walker method Chick Martin test 25
- 26. RIDEAL WALKER Organism used is usually Salmonella typhi Phenol diluted from 1:95 to 1:115 Test disinfectant diluted from 1:400 to 1:800 Disinfectant Dilution Growth of test organism in subculture after exposure for: 2.5 mins 5 mins 7.5 mins 10 mins Test disinfectant 1:400 NG NG NG NG 1:500 G NG NG NG 1:600 G G NG NG 1:700 G G G NG 1:800 G G G G Phenol 1:95 G NG NG NG 1:100 G G NG NG 1:105 G G G NG 1:110 G G G NG 1:115 G G G G 26
- 27. For example, test organism killed at 7.5 mins by a test disinfectant at 1:600 dilution Organism killed at by phenol at 1:100 dilution within same period Phenol coefficient = 600 = 6 100 If the value of phenol coefficient is more then 1 then test disinfectant is more effective then phenol. Disadvantages of rideal walker test No organic matter is included Used to evaluate phenolic type disinfectants only Short disinfection time 27
- 28. Chick Martin test Also determines phenol coefficient of the test disinfectant. Presence of organic matter in this test i.e. yeast suspension (or 3% dried human faeces). Organisms used are Salmonella typhi and Staphylococcus aureus. Time for sub culture is fixed at 30mins Gives a lower phenol coefficient than Rideal Walker method 28
- 29. COMPARING RIDEAL WALKER AND CHICK MARTIN TEST Rideal Walker Chick Martin Volume medium 5.0ml 10.0ml Diluent for test disinfectant Distilled water Water with yeast suspension of faeces Reaction temperature 17.5±˚C 30˚C organism Salmonella typhi Salmonella typhi, Staphylococcus aureus Sampling times 2.5, 5, 7.5, 10 mins 30.0mins Calculation of coefficient Dilution test killing in 7.5mins divided by same for phenol Mean concentration of phenol showing no growth after 30 min. divided by same for test 29
- 30. DISINFECTANT KILL TIME TEST Design to show log reduction values over time for a disinfectant against selected microbes (Bacterial, fungi etc) Common organisms tested include; Bacillus subtillis Staphylococcus aureus Salmonella cholerasuis Pseudomonas aeruginosa 30
- 31. The test is done by bringing a tube of a disinfectant to a certain temperature. Tube then inoculated to achieve a concentration of approx. 106 CFU/ml Aliquots are removed at five selected time points including zero and diluted Dilutions plated onto agar Colonies are enumerated and log reductions are calculated 31
- 32. For graph 32
- 33. PRACTICAL TEST These tests are performed under real life conditions after measuring the time concentration relationship of the disinfectant under quantitative suspension test It is done to verify if the selected dilution is still adequate under the conditions under which it must be used. Best known practical tests are the surface disinfection tests. An example of such is the Surface Time Kill Test 33
- 34. Another simple example is the filter paper test Discs of filter paper are used . Filter papers are soaked with a chemical disinfectant They are placed on agar plate and incubated. If the chemical is effective then clear zone appears around the disc. 34
- 36. IN-USE TEST Can be used in hospitals and laboratories to detect contamination of disinfectants 1ml of sample disinfectant added to 9ml of diluent 10drops (0.02ml each) of diluted sample are placed on each of two nutrient agar plates. One is incubated at 37˚C for 3 days The other incubated at room temperature for 7 days Five or more colonies on each plate indicates contamination 36
- 37. TESTING SCHEMES The antimicrobial efficiency of a disinfectant is examined at three stages of testing. The first phase concerns laboratory tests in which it is verified whether a chemical compound or a preparation possesses antimicrobial activity: for these preliminary screening tests essentially quantitative suspension tests are considered. The second stage is still carried out in the laboratory but in conditions simulating real-life conditions. The third phase comprises the field tests or pilot studies, and the variant of in-use tests 37
- 38. EVALUATION OF OTHER DISINFECTANTS The evaluation methods described above basically apply to liquid disinfectants. Solid disinfectants Solid disinfectants include metals such as, 1. Gold 2. Copper 3. Aluminum 4. Silver 38
- 39. EVALUATION OF SOLID DISINFECTANTS INCLUDE Exposure of disinfectant onto particular organism Inoculated onto a Solid Agar. Disc may be cut out from agar and sub cultured for enumeration of survivors. The inhibition of solid disinfectant activity is also evaluated by dusting the powders onto the surface of seeded agar plates. The extent of growth is then observed following incubation 39
- 40. AIR DISINFECTANTS Disinfection of air is very important for infection and contamination control. Air is the commonest route of transmission of infection in hospitals and other places Disinfection of air can be done via filtration (HEPA filters). 40
- 41. Via chemical agents (H2O2, formaldehyde) Also by means of ultra violet light. The number of viable bacteria present in air can be assessed by exposing Petri dishes (of solid nutrient medium) to the air (settle plate). Filtration sampling, where the air is passed through a porous membrane which is then cultured can also be used. 41
- 42. EVALUATION OF PRESERVATIVES Preservatives are added to a formulations such as oral, topical, multi-dose, and parenteral to further reduce risk of spoilage and maybe kill any anticipated low levels of contaminants remaining in the non-sterile medicine during or after manufacture, storage or during repeated redraw of doses from a multi-dose container. An ideal preservative should: Be able to kill rapidly all microbial contaminants as they enter the medicine Not be irritant or toxic to the patient Be stable through the shelf-life of the formulation Be selective in reaction with the contaminant and not the ingredients of the medicine. 42
- 43. PRESERVATIVE EFFECTIVENESS TESTING (PET) It is normally advisable to have a preservative effectiveness test conducted on a preparation. Challenge testing is used for: I. Determining the ability of food to support growth of spoilage organisms or pathogens II.Validating the process intended to deliver some degree of lethality against a target organism 43
- 44. PROCEDURE OF THE CHALLENGE TEST The final formulation was inoculated with E. coli Samples of it is taken in time intervals and cultured The viable count is carried out 44
- 45. REFERNCES Prescott & harley ,Klein (2002) ,Microbiology second edition , wm.C.brown publishers. Tortora J.G., Funk R.b. ,Christine l. case, (1997),microbiology an introduction sixth edition ,Addison Wesley Longman ALCAMO I. EDWARD(2001), Fundamentals of microbiology fifth edition ,Jones and Bartlett publishers Wistreich A.G.,MAX. D.lechtman(1988) Microbiology fifth edition , Collier macmillan publishers LANDON http://WWW.ncbi.nlm.nih.gov/pmc/articles http://www.microrao.com/micronotes/pg/testing or disinfectants.pdf 45
- 46. THANK YOU 46