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Sterilization, disinfection and antisepsis

Sterilization, disinfection and antisepsis. Two very original methods for disinfection. or. For lecture only. BC Yang. In 1866 J Lister suggested antiseptic surgery. His rational was: Putrefaction is caused by microbes Wound sepsis is a form of putrefaction

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Sterilization, disinfection and antisepsis

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  1. Sterilization, disinfection and antisepsis Two very original methods for disinfection or For lecture only BC Yang

  2. In 1866 J Lister suggested antiseptic surgery. His rational was: • Putrefaction is caused by microbes • Wound sepsis is a form of putrefaction • Wound sepsis is caused by microbes Carbolic acid, phenol For lecture only BC Yang

  3. Carbolic acid, phenol: a toxic white soluble crystalline acidic derivative of benzene • various antiseptics • various disinfectants • various germicides • adhesive dyes • perfumes • textiles • lubricating oils • Acute poisoning by ingestion, inhalation or skin contact may lead to death. • Phenol is readily absorbed through the skin. Highly toxic by inhalation. • Causes burns.

  4. In the previous year Lister had heard that 'carbolic acid' was being used to treat sewage in Carlise, and that fields treated with the affluent were freed of a parasite causing disease in cattle. • Lister then began to clean wounds and dress them using a solution of carbolic acid. He was able to announce at a British Medical Association meeting, in 1867, that his wards at the Glasgow Royal Infirmary had remained clear of sepsis for nine months. • Opposition was great In England and the United States mainly against Lister's germ theory rather than against his "carbolic treatment."

  5. Phenols and phenolics • Carbolic acid • Low level disinfectant • O-phenylphenol (Lysol) • Hexachlorophene (Phisohex) • High level for Staphylococcus sp. and Streptococcus sp. • Surgical scrubs • Damage membrane, inactive enzymes, denature proteins For lecture only BC Yang

  6. The day after SARS 蚊子少了; 人離的遠了; 官員被糾正; 化學兵正當紅 • Ethylene oxide: denatures proteins • Highly penetrating • Most used in hospitals for plastic ware, textiles, etc….. For lecture only BC Yang

  7. Mechanism of antimicrobial action • Damage to DNA: radiation, UV, DNA-reactive agents • Protein denaturation: Heat, pH, metals • Disruption of cell membrane or cell wall: detergents, enzymes • Chemical antagonism: analogs • Removal of free sulfhydryl groups: oxidizing agents For lecture only BC Yang

  8. To die or not to die, that is a question • Sepsis: microbes contamination • Asepsis: absence of microbes contamination • Sterilization: 100% killing • Disinfection: loss the ability to cause disease • -cide or cidal: killing of microorganism • -static or stasis: inhibit growth or multiplication of microbes For lecture only BC Yang

  9. Types of antimicrobial agents • Physical • Heat • radiation • Chemical • Vapors • selectivity Scientific American284 (5):54-61 For lecture only BC Yang

  10. Killing is a probability • Die at a constant rate (logarithmically) • Depend on exposure time and microbial load • Rare will reach 100% (on purpose and money consuming) For lecture only BC Yang

  11. Parameters of sterilization/disinfection • Action process • The rate/kinetics: the death rate of a microbial population follows a logarithmic path. • Resistances: pure empirical, varied from culture condition, nature of the environment • Control/indicators: • Living: • heat : spores, themophilic bacteria • ethylene oxide and radiation: Bacillus subtilits var. nigar. • Chemical: succinic anhydride (120oC), sulphur (115oC); color change; etc.. For lecture only BC Yang

  12. Action index • A spoonful work already well? • Why not LD50? • Phenol coefficient (PC) • American official analytical chemist’s use-dilution method • Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella choleraesuis • Filter paper method For lecture only BC Yang

  13. The phenol coefficient (PC) • A water-soluble phenol-based disinfectant (amphyl, lysol) is tested for its bactericidal effectiveness as compared with phenol. • These disinfectants are serially diluted in a series of salmonella cultures and incubate for a while. • Chemicals with lower phenol coefficients have greater effectiveness • Restricted to phenolics Greatest dilution of the phenolic that kills Test bacteria in 10 min, but not in 5 min PC= Greatest dilution of phenol giving same result For lecture only BC Yang

  14. As a matter of temperature • Heat • Boiling water • Moist heat (steam under pressure, autoclave) • Hot-air sterilization (Oven) • Pasteurization • Tyndallization • Incineration • Low temperature • Refrigerator temp (4-7oC) • Deep-freeze (-20oC to -40oC); liquid nitrogen (-196oC) • Lyophilization (desiccation in low temperature) For lecture only BC Yang

  15. Pasteurization • Suggested by L. Pasteur • It is used to render mild safe (tuberculoses) and extend its storage quality • Keep the flavor of milk, wine • 62oC 30 min, 71oC for 15 sec For lecture only BC Yang

  16. Pasteurization 別呆了, 不要喝尚青尚新鮮的牛奶! • 1909 John Ross Robertson finances the installation of Toronto's first milk pasteurization plant in the College Street hospital, 30 years before it becomes mandatory. For lecture only BC Yang

  17. Tyndallization (Fractional sterilization) • John Tyndall was a man of science—draftsman, surveyor, physics professor, mathematician, geologist, atmospheric scientist, public lecturer, and mountaineer. • For killing both vegetative and spore forming bacteria at temperature of 100oC or below for 30 min on the consecutive days For lecture only BC Yang

  18. Filtration For lecture only BC Yang

  19. Filtration • Liquid • When subjects are heat-labile • 0.22/0.45 mm membrane filter • Air • Large space Alternative: electrostatic precipitation • Particles passed through a high voltage electric field become charged, and attracted to and held by the plate of opposite potential (remove ~97% of bacteria) For lecture only BC Yang

  20. Wash away: do you really clean your hands? Surfactants: breaks oily film on skin For lecture only BC Yang

  21. UV radiation • Ultraviolet is light with very high energy levels and a wavelength of 200-400 nm. • One of the most effective wavelengths for disinfection is that of 254 nm. For lecture only BC Yang

  22. Alcohols • High level disinfectant • Disrupt protein, disrupt membranes, dissolve lipids • 70% ethanol • Used in tinctures For lecture only BC Yang

  23. 碘酒 Halogens (Iodine) • Iodine combines with tyrosine & oxidized SH groups on other amino acids • Tincture: 1-2% I2 + 2% Na2I in 70% ethanol (for surgical site disinfection). • Povidone-iodines: Betadine • Skin disinfection • Surgical scrub For lecture only BC Yang

  24. The choices?It always depends! • The materials • The purpose • The nature of microbes For lecture only BC Yang

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