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Sterilization, disinfection and antisepsis

Original methods for disinfection

楊倍昌

Note by Sir James Simpson: Hospitalism 1867

截肢手術的傷亡率 :

在英國超過 300 床的大醫院死亡率會超過 41%.開業醫小診所死亡率約 11%.

巴黎 : 死亡率約 60%.蘇黎世 : 死亡率約 46%.格拉斯柯 : 死亡率約 34%.柏林及其他城市 : 死亡率約 34%.

美國麻省 : 死亡率約 26%.美國賓州 : 死亡率約 24%.

蛇杖的傳人 p:439(?)

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In 1866 Joseph Lister (1827-1912) suggested antiseptic surgery. His rational was:

• Putrefaction is caused by microbes• Wound sepsis is a form of putrefaction

• Wound sepsis is caused by microbes ( 只是建議，而無方法證明 )

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信不信由你的年代• 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.

• 在截肢手術病人死亡率的證據上，運用李斯特的消毒法之前， 1864-1866 年 Glasgow 療養院病人的死亡率是

46% ，之後 1867-1869 年則降低為 15% 。

Henry Lamond, 1870 "Letter to the Editor: Professor Lister and the Glasgow Infirmary," Lancet 1: 175.

On the effects of the antiseptic system of treatment upon the salubrity of a surgical hospital, Lancet 1

(1870): 4-6; 1: 40-42.

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Carbolic acid, phenol

• a toxic white soluble crystalline acidic derivative of benzene

• 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.

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Joseph Lister was ridiculed, criticized, and harassed. The medical community didn’t like having its status quo questioned. The nurses regarded Lister’s procedures as eccentric, and they resented the extra work his obsessions with cleanliness were causing. The doctors were angered at the implication they were responsible for some of the deaths.

Louis Pasteur and Joseph Lister were personal friends and supported each other when the medical community viciously attacked them. Sometimes they felt they were alone in their struggles to bring the truth to light. People were needlessly dying, and it seemed nobody was listening.

Lister 高估了空氣中的雜物，其實病原菌來自於手術器械 , 醫師的手… ..

www.biblehelp.org/ misunder.htm

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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

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The day after SARS/Dengue Fever

蚊子少了官員被糾正 ; 化學兵正當紅新的問候語 : 你家噴藥了嗎 ?

• Ethylene oxide: denatures proteins• Highly penetrating• Most used in hospitals for plastic ware, textiles, etc…..

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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

• Chemical antagonism: analogs

• Removal of free sulfhydryl groups: oxidizing agents

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Types of antimicrobial agents

• Physical

– Heat

– Radiation

• Chemical

– Solution

– Vapors

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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

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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)

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Control/indicators:

• Living:

• heat : spores, themophilic bacteria

• ethylene oxide and radiation: Bacillus subtilits var.

nigar.

• Chemical: succinic anhydride (120oC), sulphur (115oC); color change; etc..

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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

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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)

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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

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• 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 , 什麼是尚青尚新鮮的牛奶 ?

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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

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Filtration

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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)

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Wash away: do you really clean your hands?

Surfactants: breaks oily film on skin

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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.

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Alcohols

• High level disinfectant

• Disrupt protein, disrupt membranes, dissolve

lipids

• 70% ethanol

• Used in tinctures

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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

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The choices?It always depends!

• The materials• The purpose• The nature of microbes

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