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

2. Carbolic acid, phenol 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 BC Yang For lecture only

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 BC Yang For lecture only

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….. BC Yang For lecture only

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 BC Yang For lecture only

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 BC Yang For lecture only

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

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) BC Yang For lecture only

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 (120 o C), sulphur (115 o C); color change; etc.. BC Yang For lecture only

12. Action index A spoonful work already well? Why not LD 50 ? Phenol coefficient (PC) American official analytical chemist’s use-dilution method Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella choleraesuis Filter paper method BC Yang For lecture only

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 PC= Greatest dilution of phenol giving same result Greatest dilution of the phenolic that kills Test bacteria in 10 min, but not in 5 min BC Yang For lecture only

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 62 o C 30 min, 71 o C for 15 sec BC Yang For lecture only

16. 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. Pasteurization 別呆了, 不要喝尚青尚新鮮的牛奶 ! BC Yang For lecture only

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 100 o C or below for 30 min on the consecutive days BC Yang For lecture only

18. Filtration BC Yang For lecture only

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) BC Yang For lecture only

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

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. BC Yang For lecture only

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

23. 碘酒 Halogens (Iodine) BC Yang 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

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