Disinfection by Chemicals basics

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Disinfection by Chemicals basics

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Disinfection by Chemicals basics

  1. 1. DISINFECTION by chemicals basics Dr.T.V.Rao MD Dr.T.V.Rao MD 1
  2. 2. Why we need Sterilization • Microorganisms capable of causing infection are constantly present in the external environment and on the human body. • Microorganisms are responsible for contamination and infection. • The aim of sterilisation is to remove or destroy them from materials or from surfaces. Dr.T.V.Rao MD 2
  3. 3. Uses of sterilisation 1. Sterilisation of materials, instruments used in surgical and diagnostic procedures. 2. Sterilisation of Media and reagents used in the microbiology laboratory. 3. Food and drug manufacturing to ensure safety from contaminating organisms. Dr.T.V.Rao MD 3
  4. 4. How can microorganisms be killed?  Denaturation of proteins (e.g. wet heat, ethylene oxide)  Oxidation (e.g. dry heat, hydrogen peroxide)  Filtration  Interruption of DNA synthesis/repair (e.g. radiation)  Interference with protein synthesis (e.g. bleach)  Disruption of cell membranes (e.g. phenols) Dr.T.V.Rao MD 4
  5. 5. Factors that influence efficacy of disinfection/sterilization   3 4 5 6 7 Contact time Physico-chemical environment (e.g. pH) Presence of organic material Temperature Type of microorganism Number of microorganisms Material composition Dr.T.V.Rao MD 5
  6. 6. Relative Resistance of Microbial Forms Highest resistance Moderate resistance Least resistance bacterial endospore (Bacillus & Clostridium) protozoan cyst some fungal spores some naked virus vegetative bacteria that have higher resistance ( M. tuberculosis, S.aureus, Pseudomonas) most bacterial vegetative cells ordinary fungal spores & hypae enveloped virus Yeasts Trophozoites Dr.T.V.Rao MD 6
  7. 7. Definitions: Sterilisation : – It is a process by which an article, surface or medium is made free of all microorganisms either in vegetative or spore form. Disinfection : – Destruction of all pathogens or organisms capable of producing infections but not necessarily spores. – All organisms may not be killed but the number is reduced to a level that is no longer harmful to health. Dr.T.V.Rao MD 7
  8. 8. Antiseptics : Antiseptics : – Chemical disinfectants which can safely applied to living tissues and are used to prevent infection by inhibiting the growth of microorganisms. Asepsis : – Technique by which the occurrence of infection into an uninfected tissue is prevented. Dr.T.V.Rao MD 8
  9. 9. Ideal sterilization/disinfection process • • • • • • • • Highly efficacious Fast Good penetrability Compatible with all materials Non-toxic Effective despite presence of organic material Difficult to make significant mistakes in process Easily monitored Dr.T.V.Rao MD 9
  10. 10. Number of living microbes Figure 9.1 A plot of microbial death rate Constant percentage of the extant population is killed each minute 90% die 1 min 90% die 1 min Time (min) Dr.T.V.Rao MD 10
  11. 11. Chemical Methods Many matters, substances and objects cannot be sterilized with Physical methods So Need for Disinfectants Dr.T.V.Rao MD 11
  12. 12. Chemical methods • • • • • • • • • Alcohols Aldehydes Phenols Halogens Oxidizing agents Salts Surface active agents Dyes Vapour phase disinfectants Dr.T.V.Rao MD 12
  13. 13. Chemical agents • A variety of chemical agents are used as antiseptics and disinfectants. • Factors influencing the potency of a disinfectant: • Concentration • Time of action • pH • Temperature • Nature of organism • Presence of organic matter Dr.T.V.Rao MD 13
  14. 14. Levels of Disinfection 1. High level disinfectants 2. Intermediate level disinfectants 3. low level disinfectants Dr.T.V.Rao MD 14
  15. 15. High level disinfectants: • • • Glutaraldehyde, Hydrogen peroxide, peracitic acid and chlorine compounds. Effectiveness may be equal to that of sterilisation. Used for: • Endoscopes • Cystoscopies • Surgical instruments with plastic components Dr.T.V.Rao MD 15
  16. 16. Intermediate level disinfectants • • • May not effective against spores Includes alcohols, iodophores and phenols Used for: – Laryngoscopes – Fiber optic endoscopes Dr.T.V.Rao MD 16
  17. 17. Low level disinfectants: – Many organisms can survive on exposure to these disinfectants. – Used for items which come in contact with the patients but they do not penetrate into tissues. – Stethoscopes, ECG electrodes etc. Dr.T.V.Rao MD 17
  18. 18. Alcohols : – Ethyl alcohol and Isopropyl alcohol are commonly used. – Act by denaturing of bacterial proteins. – No sporicidal and virucidal activity. – Used as skin antiseptics. – Isopropyl alcohol is preferred to Ethyl alcohol as it is better fat solvent, more bactericidal and less volatile. Dr.T.V.Rao MD 18
  19. 19. Aldehydes: 2. a) Formaldehyde b) Glutaraldehyde Dr.T.V.Rao MD 19
  20. 20. Formaldehyde:     Bactericidal, sporicidal and virucidal Used in both aqueous solution and gaseous forms A 10% aqueous solution is routinely used. Uses: 1) 2) 3) 4) 5) preservation of tissues for pathological examination To sterilize bacterial vaccines To prepare toxoid from toxin For killing of bacterial cultures and suspensions For destroying anthrax spores in hair and wool. Dr.T.V.Rao MD 20
  21. 21. Glutaraldehyde : • Effective against bacteria , fungi and viruses. • Less toxic and irritant to eyes and skin than formaldehyde • Used as 2% buffered solution • Available commercially as CIDEX • Uses: 1. For sterilisation of cystoscopes, endoscopes and bronchoscopes 2. For sterilisation of plastic endotracheal tubes, face masks, rubber anesthetic tubes Dr.T.V.Rao MD 21
  22. 22. Phenols: • • • • Lister,the father of antiseptic surgery, first introduced the use of phenol ( Carbolic acid) in surgery (1867). Produced by distillation of coal tar between temperatures of 170°C and 270°C. Bactericidal action due to cell membrane damage. Commonly used Phenol derivatives are 1. cresol 2. chlorhexidine 3. chloroxylenol 4. hexachlorophanes Dr.T.V.Rao MD 22
  23. 23. Cresols : • • • Lysol is a solution of cresols in soap. Active against a wide range of organisms. uses: 1. For sterilisation of infected glass ware 2. Cleaning of floors 3. Disinfection of excreta Dr.T.V.Rao MD 23
  24. 24. Chlorhexidine: –Eg.Savlon – (Chlorhexidine and Cetrimide) –More active against Gram positive than Gram negative –Good fungicidal activity. –No action on spores and little activity against viruses Dr.T.V.Rao MD 24
  25. 25. Chloroxylenol : –Eg.dettol –Less toxic and less irritant. –Readily inactivated by organic matter –Inactive against pseudomonas. Dr.T.V.Rao MD 25
  26. 26. Hexachlorophanes: : • More active against Gram positive than Gram negative bacteria. • Bacteriostatic at high dilutions. • Applied on skin as prophylaxis against staphylococcal infections. • Potentially toxic and should be used with care. Dr.T.V.Rao MD 26
  27. 27. Halogens: 4.Halogens: i. Chlorine ii. Iodine  Commonly used disinfectants  Bactericidal, sporicidal and virucidal Dr.T.V.Rao MD 27
  28. 28. Chlorine :  In the form of  Bleaching powder,  Sodium hypochlorite  Chloramine  Disinfection is due to release of free chlorine.  Reacts with water to form hypochlorus acid .  Bactericidal, viricidal, fungicidal and sporicidal.  Used in water supplies, swimming pools, food and dairy industries. Dr.T.V.Rao MD 28
  29. 29. Iodine : • Used as skin disinfectant. • Bactericidal and moderate action on spores. • Betadine is one example. Dr.T.V.Rao MD 29
  30. 30. 5.Oxidising agents: Hydrogen peroxide • Effective at concentration of 3-6% • Kills spores at 10- 25% • Used to disinfect »Contact lenses »Surgical prostheses »Plastic implants Dr.T.V.Rao MD 30
  31. 31. Salts: • Salts of heavy metals have toxic effect on bacteria. • Salts of copper, silver and mercury are used as disinfectants. • Act by coagulation of bacterial proteins. • Mercuric chloride, once used as disinfectant is highly toxic. • Thimersol and mercurochrome are less toxic • Copper salts are used as fungicides. Dr.T.V.Rao MD 31
  32. 32. Surface active agents: • Substances which alter energy relationships at interfaces , producing a reduction of surface tension, are known as surface active agents or surfactants. – Anionic – cationic – nonionic – amphoteric compounds. Dr.T.V.Rao MD 32
  33. 33. The anionic compounds: : • e.g.:- common soaps, • Have strong detergent but weak antimicrobial properties . • These agents are most active at acidic ph. • Effective against Gram positive organisms but are relatively ineffective against Gram negative species. Dr.T.V.Rao MD 33
  34. 34. : Cationic surfactants: • Quaternary ammonium compounds are the most important cationic surfactants. • These compounds are bactericidal for a wide range of organisms, gram positive species are more susceptible. • The common cationic compounds are acetyl trimethyl ammonium bromide (cetavalon or Cetrimide) and benzalkonium chloride. Dr.T.V.Rao MD 34
  35. 35. Amphoteric compounds: Known as ‘Tego’ compounds possess detergent properties of anionic and antimicrobial activity of cationic compounds. • They are active against a wide range of Gram positive and Gram negative organisms and some viruses. Dr.T.V.Rao MD 35
  36. 36. Dyes : : • Two groups of dyes have been used extensively as skin and wound antiseptics – aniline dyes – acridine dyes • Both are bacteriostatic in high dilution but have low bactericidal action. • Aniline dyes include crystal violet, brilliant green and malachite green. • They are more active against Gram positive bacteria than Gram negative bacteria. Dr.T.V.Rao MD 36
  37. 37. Dyes : • Acridine dyes include acriflavine , euflavine, proflavine and aminacrine. • They are more active against Gram positive bacteria than Gram negative bacteria. • Gentian violet and acriflavine are two widely used dyes for skin disinfection especially in Gram positive bacterial infections. Dr.T.V.Rao MD 37
  38. 38. Vapour phase disinfectants: • Formaldehyde gas • Ethylene oxide • Betapropiolactone Dr.T.V.Rao MD 38
  39. 39. Formaldehyde gas: • Used for fumigation of operation theatres, wards and laboratories etc. • It is generated by adding 150 gm of KMnO4 to 280 ml of formalin for 1000 cu. Feet of room volume. • The doors should be sealed and left unopened for 48 hours. • The gas is toxic and irritant when inhaled. • After completion of sterilisation the irritant vapors are nullified by exposure to ammonia vapor. Dr.T.V.Rao MD 39
  40. 40. Ethylene oxide: • It is a colorless liquid with a boiling point of 10.7°C. • Effective against all types of organisms including viruses and spores. • It has a potential toxicity to human beings, including mutagenicity and carcinogenicity . • It is highly inflammable. • Used for sterilizing plastic and rubber articles, respirators, heart lung machines, sutures, dental equipment's etc. Dr.T.V.Rao MD 40
  41. 41. Betapropiolactone : • Condensation product of ketane and formaldehyde. • It has a boiling point of 163°C. • Used in 0.2%. • Effective against all types of organisms including viruses. • More efficient for fumigation than formaldehyde. • Used for inactivation of vaccines. Dr.T.V.Rao MD 41
  42. 42. • Programme Created by Dr.T.V.Rao MD for Medical and Paramedical Students in the Developing World • Email.com • doctortvrao@gmail.com Dr.T.V.Rao MD 42

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