Individual antimicrobial processes

1. Individual antimicrobial processes

2. Common sterilizers and disinfectants • Sterilizers • Physical • Dry heat (> 160 oC) • Most heat (>121 oC) • Ionizing radiation • Chemical • Gaseous chemicals • Disinfectants • Physical • Ultraviolet radiation • Hydrostatic pressure • Chemical • Surface-active agents • Phenolic compounds • Iodine and iodine compounds • Peoxygen compounds • Chlorine species (free chlorine, chloramines) • Chlorine dioxide • Ozone

3. Sterilizers

4. Dry heat (I) • Mechanism: protein denaturation, enzyme inhibition, and RNA and DNA breakdown • Protein coagulation (complete denaturation) (e.g. egg albumin) • 50 % water: 56 oC • 25 % water: 74-80 oC • 18 % water: 80-90 oC • 6 % water: 145 oC • 0 % water: 160-170 oC • Time-temperature in sterilization with dry air (to inactivate bacterial spores) • 170 oC for 60 min • 160 oC for 120 min • 150 oC for 150 min • 140 oC for 180 min • 121 oC for overnight

5. Dry heat (II) • Advantages • Deep penetration • Less corrosivity • Disadvantages • High temperature • Long sterilization period • Deterioration of materials • Used only for those materials that can not be sterilized by moist heat: petroleum, oil, powers, sharp instruments, and glassware

6. Moist heat (I) • Mechanism: protein denaturation, enzyme inhibition, RNA and DNA breakdown • Advantage • Low temperature and short sterilization period (121 oC for 15-30 min) • Disadvantage • Less penetration • Moisture damage

7. Moist heat (II) (A steam autoclave)

8. Ionizing radiation (I) • Electromagnetic radiations: γ radiation, x-ray, and electrons • Particle radiations: α radiation, β radiation, meson, positron, neutrino • Mechanism: single or double-strand breakage in DNA

9. Ionizing radiation (II)

10. Ionizing radiation (III)

11. Ionizing radiation (IV)

12. Ionizing radiation (V)

13. Ionizing radiation (VI)

14. Gaseous chemical sterilization (I) • Alkylating agents (Alkylation of DNA) • Ethylene oxide • Propylene oxide • Formaldehyde • Beta-propiolactone • Oxidizing agents (Oxidation of proteins and nucleic acids) • Hydrogen peroxide • Peracetic acid • Chlorine dioxide • Ozone

15. Gaseous chemical sterilization (II)

16. Gaseous chemical sterilization (III)

17. (Chemical) disinfectants

18. Surface-active agents • Amphiphilic compounds • Anionic, cationic, nonionic, and amphoterics • Cationic surfactants: Quaternary ammonium compounds • Basic structure: • One nitrogen atom • Four carbon atoms covalently linked to the nitrogen atom • An anion eletrostatically linked to the nitrogen atom • Mechanism: Protein denaturation, enzyme inhibition, and disruption of cytoplasmic membrane

19. Quaternary ammonium compounds (I)

20. Quaternary ammonium compounds (II)

21. Quaternary ammonium compounds (III)

22. Quaternary ammonium compounds (III) • Advantages • Low toxicity • Low corrosivity • Stable at high temperature and wide pH range • Relatively tolerable with organic load • Disadvantage • Not effective against viruses, protozoa, and spores • Less effective at low temperature • Inhibited by most anionics and hard water salts

23. Quaternary ammonium compounds (IV) (applications) • General surface disinfectant • Industrial application (hot water in large commercial laundry) • Swimming pool water??? Drinking water (emergency situation)???

24. Phenol compounds (I) • Structure • Mechanism • Bacteria: denaturation of proteins, inhibition of enzymes, damages on plasma membrane • Viruses and fungi: Unknown

25. Phenol compounds (II)

26. Phenol compounds (III)

27. Phenol compounds (IV) • Advantages • Effective against viruses, bacteria, and fungi • Stable in concentrate • Tolerable for organic load and hard water • Disadvantages • Not effective against spores • High toxicity • Not effective at low temperature • Incompatible with nonionic and cation surfactants

28. Phenol compounds (IV) • General surface disinfectant • Gemicidal soaps and lotions, antiseptics, preservatives in cosmetics, and mouthwash preparation (Listerine)

29. Iodine and iodine compounds (I) • Chemistry • Antimicrobial agents: I2 (free iodine), HOI (hypoiodous acid), H2OI+ (Iodine cation) • Mechanism: protien denaturation, damages in plasma membrane, and nucleic acid breakdown

30. Iodine and iodine compounds (II)

31. Iodine and iodine compounds (III) • Advantage • Effective against viruses, bacteria, fungi, protozoa and bacterial/fungal spores • Low toxicity • Very stable in concentrate • Disadvantages • Chemical hazard (staining) • Less effective at low temperature • Relatively corrosive at high temperature • Expensive

32. Iodine and iodine compounds (IV)

33. Peroxygen compounds (I) • Hydrogen peroxide, peracetic acids, perfomic acid, and perpropionic acids • Mechanism: hydroxyl radicals: proteins, lipids, and DNA • Very effective on most microbes including spores

34. Peroxygen compounds (II)

35. Peroxygen compounds (III)

36. Peroxygen compounds (IV)

37. Peroxygen compounds (V)

38. Peroxygen compounds (VI) • Advantages • Strong, fast-acting • Effective against most microbes including spores • No toxicity • No environmental concern • Effective over wide pH (up to 7.5) and temperature ranges (40 oF – 150 oF) • Stable in concentrate • Tolerable for organic load • Disadvantages • Limited stability at use solution • Corrosive on soft surfaces (brass, copper, and mild and galvanized steel)

39. Peroxygen compounds (VII) • Excellent surface disinfectants • Industrial water systems (Legionella control) • Wastewater disinfection • Antiseptics • Cold sterilization of phamatheuticals (emulsions, hydrogels, ointments, and powders)

40. To be continued