Sterilization & DisinfectionChemical Agents

Hugh B. Fackrell

chemster.ppt

04/18/23

2

Sterilization & Disinfection

Definitions Bacterial Cell Death General characteristics Types of Chemical Agents Comparisons

04/18/23

3

Definitions

Sterilization– Complete Destruction of ALL microbes

Disinfection– Killing of pathogens on inanimate objects– physical or chemical

Antiseptic– A chemical agent for disinfection of living tissue– External skin, mouth vagina

04/18/23

4

Definitions

Bacteriocide – kill microbes– also germicide, fungicide, virucide

Bacteriostatic– Prevents or stops microbial growth– also fungistatic, virustatic

Aseptic(Asepsis)– Prevent contamination of person or object by microbes

04/18/23

5Definitions

Sanitize– Removal of pathogens from inanimate objects– Mechanical or chemical cleaning– need not sterilize of disinfect

Contamination– Presence of living microbes on object

04/18/23

6

Definitions

Infection– Presence of living multiplying microbes in host

tissues– often pathogenic

Preservation– Prevention of spoilage– Control of Contamination– Bacteriostatic

04/18/23

7

Bacterial Cell Death

Time (min)

Survivors

(log)

0

1

2

3

4

5 1 log decrease = 90% kill

1 log Death rate (D) varies with bacteriocide

D Time(min) to kill 90%

04/18/23

8

Chemical agents

Wide variety in susceptibility Growing cells more susceptible than resting

cells or spores Gram +ve more susceptible than Gram -ve Mycobacterium (TB) more resistant Hepatitis virus very resistant

04/18/23

9

General Rule for Disinfection

Clean then disinfect– organic matter inactivates many chemicals

Use at recommended strength– Undiluted NOT always best– 70% alcohol better than 100% alcohol

Prevent contamination of disinfectant Prepare fresh

– deterioration after prolonged storage

04/18/23

10

Types of Chemical Agents

Phenols Halogens Metal ions Alcohols Detergents Alkylating agents Ethylene Oxide Hydrogen peroxide

04/18/23

11

When in doubt about efficiency of a disinfectant

Get a laboratory test

04/18/23

12

Phenols

Mechanism of action– Rupture the cell membrane– Denature enzymes (protein)

Effective in presence of organic matter– blood, pus, feces, vomitus

Good environmental disinfectants

04/18/23

13

Phenols (examples)

Phenol– corrosive to skin– smell– 1% effective disinfectant

04/18/23

14

Cresols

– Methyl phenol– Phenyl-phenol (“Lysol”)

04/18/23

15

Chlorinated phenols

Hexachlorophene– Effective against Gm +ve– absorbed through skin– Toxic to infants if used often

Pentachlorophenol– more toxic than above

04/18/23

16

Halogens

Cholorine Iodine

04/18/23

17

Iodine

Applications– Skin antiseptic– Environmental disinfectant

Mode of Action – Iodination of Tyrosine

04/18/23

18

Iodine (cont)

Prepare fresh– Dark brown - active– Straw Yellow - inactive

Clean area first– organic matter reduces activity

04/18/23

19

Iodine Formulations

Tincture iodine I2 in ethanol

Aqueous iodine I2 in NaI/KI

Iodophors (organic)– I2 in nonionic detergent

• Wesocdyne– Generally 75 ppm

– Mycobacterium 450 ppm

– Iodoform• I2 chemically combined

04/18/23

20

Chlorine

Bacteriocide, fungicidal, virucidal– 2-10 ppm

Applications– disinfection of water, sewage etc

Mode of Action– Oxidizes proteins

Features– corrosive– smells

04/18/23

21

Chlorine /formulations

Chlorine gas– Poisonous

– forms HOCl (hypochlorous acid) in water

Applications– water supplies

– swimming pools

– sewage effluent

Inorganic chlorine– Bleach NaOCl

– hypochlorite Ca(0Cl)2

– chloramine

effective against– Hepatitis

– HIV

04/18/23

22

Metal Ions

Silver– 1% AgNO3 eye drops

– gonnorrheal neaonatal opthalmitis

Mercury– Hg Cl2 Skin antiseptic

– Mercurochrome

Copper, zinc– fungicide, algacide– pressure treated wood

04/18/23

23

Alcohols

Ethanol– 70-75% in water best– absolute less effective

Isopropanol– kills Mycobacterium

“Tincture of … “ alcohol used as the solvent for other ingredient

04/18/23

24

Detergents

Sanitize– soaps– neutral detergents

Disinfect– Anionic detergents– Cationic detergents

More effective with phenol Surface active

DO NOT MIX

04/18/23

25

Anionic Detergents

-ve charge salts of long chain alkyl or aryl sulphonates

04/18/23

26

Cationic Detergents + ve charge non toxic inactivated by proteins

– eg cotton fibres

effective at low concentrations Quaternary ammonium compounds

– Benzalkonium chloride– eg “Zephiran”

Not effective for

Pseudomonas

04/18/23

27

Chlorohexidine “Hibitane”

– 4% gluconate

Emulsion used as a scrub Topical application for minor skin infections

– inefficient at high concentrations

Mode of action– cell membrane– denatures protein– not affected by organic matter

04/18/23

28

Alkylating Agents

Cross link proteins, nucleic acids– -NH2, -OH,-SH,-COOH

Formaldehyde Glutaraldehyde Beta-priopiolactone Ethylene oxide

04/18/23

29

Formaldehyde

HCHO Toxic Irritant Gas - fumigant Solutions- protein vaccines

– tetanus diptheria

04/18/23

30

Glutaraldehyde

2% glutaraldehyde pH 8 Exposure time

– 5 min bactericidal– 10 min kills Mycobacterium, Heptatitis virus– 10 hr sterilizes

Applications– Lensed instruments, tubing, scalpels, inhalators

04/18/23

31

Beta-propiolactone

Carcinogenic Unstable

– degrades but leaves no residue

Applications- sera, vaccines

04/18/23

32

Ethylene Oxide

Sterilizes heat sensitive or chemcial sensitive objects

Flammable, explosive carcinogenic Gas sterilizing autoclave

– 3-4 hr, 60 oC, high pressure– 24 hr room temperature to dissipate gas– use with CO2 or FREON to reduce explosions

H2C CH2

O

Pregnant women should not be exposed!!

04/18/23

33

Hydrogen Peroxide

Oxidizing agent Disinfectant -6%

– Bactericidal– Fungicidal– Virucidal

Prepare fresh

04/18/23

34

Kill curves of various antiseptics%

su

rviv

ors

Time (sec)

Soap & water

70% ethanol

Tincture of Merthiolate

Aqueous Zephiran

Tincture of Zephiran

Tincture of Iodine