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CHAPTER – IV

CHAPTER – IV. DISINFECTION. CONTENT OF THE CHAPTER. GENERAL Introduction Terminologies Classification Properties of disinfectant Factors Affecting disinfectant action EVALUATION Bacteriostatic , Bacteriocidal evaluation Phenol Coefficient test. DIS - INFECTION.

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CHAPTER – IV

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  1. CHAPTER – IV DISINFECTION

  2. CONTENT OF THE CHAPTER • GENERAL • Introduction • Terminologies • Classification • Properties of disinfectant • Factors Affecting disinfectant action • EVALUATION • Bacteriostatic, Bacteriocidal evaluation • Phenol Coefficient test

  3. DIS - INFECTION • Destruction of microorganisms, but not usually spores: not necessarily killing all microorganisms but reducing them to a level of not harmful to human health. • Commercially for the treatment of inanimate objects and materilas.

  4. Commercially Available Disinfectants And Their Applications

  5. TERMINOLOGIES

  6. Classification of Disinfectants Examples Groups of DI

  7. Groups of DI Examples

  8. Mechanism of action of disinfectants

  9. DISINFECTANT MECHANISM OF ACTION

  10. DISINFECTANT MECHANISM OF ACTION

  11. Properties of Disinfectants DISINFECTANT PROPERTIES OF DISINFECTANT

  12. DISINFECTANT PROPERTIES OF DISINFECTANT

  13. Quaternary ammonium compounds • Quaternary ammonium compounds ("quats"), such as benzalkonium chloride, are a large group of related compounds. Some concentrated formulations have been shown to be effective low-level disinfectants. Typically, quats do not exhibit efficacy against difficult to kill non-enveloped viruses such as norovirus, rotavirus, or polio virus. Newer synergous, low-alcohol formulations are highly effective broad-spectrum disinfectants with quick contact times (3–5 minutes) against bacteria, enveloped viruses, pathogenic fungi, and mycobacteria. Quats are biocides that also kill algae and are used as an additive in large-scale industrial water systems to minimize undesired biological growth.

  14. Silver • Silver has antimicrobial properties, but compounds suitable for disinfection are usually unstable and have a limited shelf-life. Silver dihydrogen citrate (SDC) is a chelated form of silver that maintains its stability. • modes of action: • 1)deactivates structural and metabolic membrane proteins, leading to microbial death; • 2) the microbes view SDC as a food source, allowing the silver ion to enter the microbe. Once inside the organism, the silver ion denatures the DNA, which halts the microbe's ability to replicate, leading to its death. SDC is non-toxic, non-caustic, colorless, odorless, and tasteless, and does not produce toxic fumes.

  15. Copper • Continuously reduce bacterial contamination, achieving 99.9% reduction within two hours of exposure; • Kill greater than 99.9% of Gram-negative and Gram-positive bacteria within two hours of exposure; • Deliver continuous and ongoing antibacterial action, • Kill greater than 99.9% of bacteria within two hours, and continue to kill 99% of bacteria even after repeated contamination;

  16. Factors Affecting Disinfectant Action • Time of contact • Conc. of disinfectant • Temperature • Type of m/o. present, its number & condition • Hydrogen ion conc. • Surface tension • The formulation if the disinfectant • The chemical structure of the disinfectant • The nature of surface to be disinfected. • Potentiation, Synergism and Antagonism of disinfectant

  17. 1.Time of contact • Viable count Vs Time – Death curve LOG NO. OF SURVIVALS a b c C B A TIME

  18. DEATH CURVE • A- Curve often obtained with high conc. • B- Disinfection Process Obeying First Order Kinetics • C- Sigmoid curve • a- slow initial kill of more sensitive org. • b- faster “near linear” average resistant org. • c- slower death rate of more resistant org. • Rate k = 1/ t log N / n

  19. 2. Concentration Concentration 0100 LOG NUM. OF SURVIVALS A = 0.66% w/v B = 0.55% w/v C = 0.50% w/v D = 0.44% w/v 10 A B C D 1.0 0.1 0.001 TIME - MINUTES

  20. Concentration B 1 6 1 Log t 1 A Log C

  21. Phenol : n = 6 0.7% kills in 100 mins. Doubling :1.4% kills in 100/2n 100/26 = 1.6 min Halving : 0.35% kills in 100X2n 100X26 = 6400mins Formaldehyde : n = 1 0.7% kills in 100 mins Doubling: 1.4% kills in 100/2n 100/21 = 50mins Halving : 0.35% kills in 100 X 2n 100X21 = 200 mins Comparison of increased and decreased concentration on killing rates of Phenol and Formaldehyde

  22. Temperature Increase in the temp, increases the velosity, increases the bactericidal action Ө(T2-T1) = K2/K1 K1, = reaction velocity at temp T1, K2 = reaction velocity at temp T2 Reaction velocity K = 1 / extinction time (Extinction time = time at which no living cells can be detected from the sample taken) 2.5 2.0 Extinction time 1.5 1.0 0.5 temperature 10 20 30

  23. Type Of Organism Present, Its Number, Cndn, • Aldehyde + Halogen + β-Propiolactone - ANTIVIRAL • Presence Of Organic Matter, Any In activators • Extracellular protein – reduction in bactericidal action • Oils & Fats – Decreases Phenol activity • Hydrogene ion Concentration • Affects the rate of growth of microbes • Degree of ionization of disinfectant & potency • Adsorption of disinfectant at cell surface • Phenol, Benzoine, Salycilates are active in acidic pH • Acridine - active in ionized from • Surface tension

  24. The formulation of disinfectant • Increase in conc. of soap will increase the extinction time. • Alcoholic formulation increases the activity • The chemical structure of disinfectant • Alkyl chain up to 6 increases the activity • Alkyl chain more than 6 decreases the activity • Straight alkyl chain give greater activity than branched • Halogenation increases the activity • Nitration increases the activity • The nature of surface to be disinfected • Uneven, porous, cracked surface resist chemical disinfectant • Plain, clean impenetrable surface increases the activity • Potentiation, Synergism and Antagonism

  25. EVALUATION OF DISINFECTANT

  26. Evaluation of Disinfectant • Evaluation of Bacteriostatic disinfectant • Serial dilution in liquid media • Serial dilution in solid media • Fish Spine bead method • Cylinder plate method • Filter paper disc method • Cup and Plate method • Gradient Plate technique • Ditch Plate method

  27. Serial dilution in liquid media • Media + 0.2ml of Culture + Test DI Dilution control 5th Dil I st Dil 2nd Dil 3rd Dil 4th Dil

  28. Results after incubation

  29. Serial dilution in solid media • Solid media + culture + Test DI control Ist dilution I st Dil 2nd dilution IInd Dil control 3rd dilution 5th dilution 4th dilution 5th Dil 4th Dil 3rd Dil

  30. Fish spine bead, Cylinder plate, Cup and plate, Filter paper disc method Cup Shape Fish Spine Bead Beaker containing Test Disinfectant Beaker containing Test Disinfectant Paper disc

  31. Procedure Prepare and sterilize required quantity of medium Keep the sterile glass wares ready Pour media to plate & allow to solidify Swab / inoculate with organism • Make well shape • Place paper disc • Place fish spine bead • Place cylinder • Inculabate

  32. Gradient plate technique

  33. Ditch plate method

  34. Assessment of Bacteriostatic activity • Zone of Inhibition Growth of organism on Agar Media 1.0 1.5 Zone of Inhibition 0.5 control 2.0 2.5 Dilution of Test disinfectant

  35. Evaluation of Disinfectant • Evaluation of Bactericidal disinfectant • Phenol Coefficient test • End point technique • Extinction time method • Rideal –Walker Coefficient method • FDA • Chick Martin test • AOAC • Crown Agent technique

  36. Schematic Diagram of Phenol Coefficient test Broth tubes Reaction mixture 0 1 in 1000 0.5 1 in 1100 S.Typhi 24 hrs culture 1 in 1200 1.0 1 in 1300 1.5 2.0 Control Phenol 1 in 105 Incubate 2-3 days at 370C 2.5 5.0 7.5 10 Temp 17.5

  37. R.W.COEFFICIENT • There are two types of extinction time method • In which the extinction time is fixed and the conc. Of disinfectant needed to kill in the specified time is estimated. • In which the conc. of bactericide is fixed and the extinction time is estimated.

  38. R.W.COEFFICIENT • Standard: Rideal Walker Broth • Organism: Salmonella Typhi • Dilution of Phenol 1 in 105 • Dilution of test DI = 1in 1000, 1 in 1100, 1 in 1200, 1 in 1300. • Test DI + 0.2 ml of S.Typhi • Reaction mixture should be at 17.50C temp. • Subculture of each reaction mixture are taken and transformed to broth after 2.5, 5, 7.5 and 10 mins. • Broth tubes are incubated at 370C, for 48 to 72 hrs, examined. • Presence or absence of growth was noted

  39. Observed results in table Minutes culture exposed to disinfectant 10 2.5 7.5 5.0 Dilution + + + + - + + + - - + + - - - + 1 in 1000 1 in 1100 1 in 1200 1 in 1300 Test disinfectant - Phenol 1 in 105 + + - + = Growth - = No growth

  40. R.W. Coefficient • R.W. Coefficient = Dilution of test disinfectant killing in 7.5 mins, but not in 5 mins. / Dilution of Phenol killing in 7.5 mins, but not in 5 mins. 1100/105 = 10.47.

  41. Essential difference between phenol coefficient tests

  42. Bentley's text book of Pharmaceutics REFERENCE Kindly refer the text book referred by The TN Dr. MGR Medical University Thank u I ACKNOWLEDGE MY MISTAKES. SORRY

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