Chemical disinfection PHD

Chemical Disinfection is a topic under Public Health Dentistry which focuses on various methods and agents that can be used for disinfection of instruments, equipments and other substances used in Dental clinics and other fields of Dentistry.

1. By- SYED MAJDI MOHAMMADI 3 rd BDS

2. CONTENTS DEFINITIONS DIFFERENCES FROM STERILIZATION CHEMICAL DISINFECTANTS - MODE OF ACTION -IDEAL REQUIREMENTS -POTENCY -AGENTS REFERENCES

3. DEFINITIONS DISINFECTION : It is the process of destruction or removal of all pathogenic organism or organism capable of giving rise to infection. DISINFECTANT : Disinfectants are chemical agents designed to inactivate or destroy microorganisms on inert surfaces.

4. DIFFERENCES STERILIZATION DISINFECTION A) Total destruction of all microorganisms (whether or not pathogenic) and their spores, usually through the use of drastic methods. A) Minimizes the number of microorganisms but doesn’t eliminate them completely. B) Uses more robust methods such as high heat and radiation. B) Uses moderately effective methods. C) It gives extreme cleanliness. C) It gives an adequate cleanliness.

5. STERILIZATION DISINFECTION D) Destroys both living organisms and their resistant structures. D) Destroys only the living organisms. E) Use: decontamination of food, medicine and surgical instruments. E) Use: mostly used to decontaminate surfaces and air. CONTD…

6. CHEMICAL DISINFECTANTS These are the chemical substances which are used to kill or deactivate pathogenic microorganisms. The efficiency of chemical disinfection depends on- Reactivity with biomolecules Disinfection concentration throughout the treatment Duration of the disinfection treatment(exposure time)

7. The chemicals used as disinfectants generally behave as ‘ protoplasmic poisons ’ in three different ways- Damaging the bacterial cell membrane - agents: chlorhexidine, quaternary ammonium compounds, alcohols and phenols. Fixation of the cell membrane and blockage of egress of cellular components - agents: formaldehyde and glutaraldehyde. Oxidizing cellular constituents - agents: halide disinfectants such as hypochlorite and bromides. MODE OF ACTION

8. IDEAL REQUIREMENTS To be applicable in the context of sanitation, chemical disinfections must have several basic characteristics- Must be active against a wide range of pathogens Be sufficiently cost-effective Be reasonably safe to produce, store and apply Act in the presence of organic matter Have high penetration power and quick action

9. POTENCY OF CHEMICAL DISINFECTANTS D epending on their ability to kill various groups of organisms, disinfectants can be classified as- ■ High-level disinfectants: they are active against Gram-positive and Gram-negative bacteria, spores and M. tuberculosis ■ Intermediate-level disinfectants: destroy M. tuberculosis , vegetative bacteria, most viruses and fungi, but few, if any, spores. ■ Low-level disinfectants: kill most bacteria and most fungi, but not M. tuberculosis or spores.

10. AGENTS OF CHEMICAL DISINFECTION Alcohols Aldehydes Phenols Halogens Hydrogen peroxide Peracetic acid Dyes Ethylene oxide(ETO)

11. i . ALCOHOLS TYPES: Ethyl alcohol Isopropyl alcohol Methyl alcohol (rarely used in healthcare) MODE OF ACTION: They act by denaturation of proteins. (used in 60-70% water to be effective)

12. SPECTRUM OF ACTION: They are Bactericidal, tuberculicidal and fungicidal. USE: They are used mainly as skin antiseptics. To disinfect clinical thermometer, scissors, stethoscopes, ultrasound instruments and hoods

13. LIMITATIONS: Alcohols lacks sporicidal action They cannot penetrate protein rich material They tend to swell and harden rubber and certain plastic tubing after prolonged and repeated use

14. ii. ALDEHYDES TYPES: Formaldehyde Glutaraldehyde Ortho Phthalaldehyde (OPA) MODE OF ACTION: Inactivates bacterial proteins by forming covalent cross links with several functional groups.

15. 1. FORMALDEHYDE It is markedly Bactericidal, sporicidal and virucidal. It is used both as an aqueous solution and in gaseous form. A 10% aqueous solution of Formalin is routinely used. USES: Preservation of tissue for histological examination. To inactivate viruses and bacteria in vaccine Dilution containing 5% formaldehyde is used as a disinfectant directly to a contaminated surface.

16. LIMITATIONS: It has pungent strong smell, irritant to eyes and mucous membrane. 2. GLUTARALDEHYDE: It is effective against bacteria(including M. tuberculosis) , fungi and viruses(including HIV, Hepatitis B and enteroviruses). It is less toxic and irritant than formaldehyde. It is used as 2% buffered solution. It is available commercially as ‘ Cidex ’.

17. USES: Disinfection of Hospital Equipments : Endoscope, Cytoscope , anaesthetic equipment, Plastic material and Thermometer. LIMITATIONS: Respiratory irritation from glutaraldehyde vapour. Pungent and irritating odour. Allergic contact dermatitis.

18. 3. ORTHO-PHTHALALDEHYDE(OPA): OPA is a high level disinfectant. It is more stable during storage and more rapidly mycobactericidal than glutaraldehyde. 0.5% OPA is sporicidal. USES: It is used for endoscopes, cystoscope, thermometers, etc. Useful for glutaraldehyde resistant Mycobacteria.

19. LIMITATIONS: Irritant to respiratory tract and eyes. Has to be dealt with extreme precaution.

20. iii. PHENOLS They are produced by distillation of coal tar between temperatures of 170°C and 270°C. They are active against gram positive, gram negative bacteria and mycobacteria. MODE OF ACTION: Cell membrane damage
Releases cell contents and causes lysis.

21. USES: • Decontamination of infective discharges, bathrooms, and hospital floors. • In diluted form it is used as an antiseptic. LIMITATIONS: • Not active against endospores and viruses. • Activity reduced in alkaline pH and hard water.

22. DISINFECTANTS OF PHENOLIC GROUP: Phenol Cresols
Chlorhexidine Chloroxylenol Hexachlorophane 1. PHENOL It has a powerful bactericidal action at a concentration of 1%. It’s activity is reduced drastically upon dilution.

23. Commercial preparations of Phenol : A) SUDOL : Contains Xylenols and Phenols. B) JEYES FLUID : Used to treat faeces and sputum before disposal. 2. CRESOLS : “Lysol” is a solution of Cresols in soap. Uses: To sterilize infected glass wares, cleaning floors and disinfection of excreta.

24. Advantages: They are not readily inactivated by the presence of organic matter. They are active against a wide range of organisms. 3. CHLORHEXIDINE: It is bactericidal at a high dilution. It is more active against Gram positive than Gram negative bacteria with no action against Tubercle bacilli or spores. Has very little activity against viruses. Has a good fungicidal activity.

25. “Savlon” is a solution of chlorhexidine and cetrimide. It is widely used in wounds, preoperative disinfection of skin, as a bladder irrigant, etc.

26. 4. CHLOROXYLENOL: It is an active ingredient of “Dettol” (used in 4.8% concentration) It is less toxic and less irritant. 5. HEXACHLOROPHANE: Active against Gram positive bacteria. Applied on skin as prophylaxis against Staphylococcal infections. It is bacteriostatic at very high dilutions. It is potentially toxic and hence should be used with care.

27. iv. HALOGENS Chlorine and Iodine are two commonly used disinfectants. 1. CHLORINE It is bactericidal and has a wide spectrum of activity against viruses. It is used in water supplies, swimming pools, food and dairy industries.

28. 3 main chlorine compounds used as disinfectants are: A) BLEACHING POWDER or CHLORINATED LIME - used as a disinfectant for HIV infected material. B) SODIUM HYPOCHLORITE -has a bactericidal, fungicidal, virucidal and a rapid sporicidal activity. C) CHLORAMINE -it retains chlorine longer and has a prolonged bactericidal effect. CONTD…

29. 2. IODINE: It is active against bacteria, viruses and fungi. MODE OF ACTION: By disruption of protein and nucleic acid structure and synthesis, USES: Bactericidal antiseptic for intact skin For disinfection of wound. For disinfecting blood culture bottles and medical equipments .

30. Preparations of Iodine: Tincture of iodine : It is a weak solution of iodine containing 2.5% iodine, 2.5% potassium iodide in 90% alcohol. Iodine : 2% in 70% Isopropyl Alcohol. - Tincture iodine and iodine are rapid disinfectants and are used as antiseptics before surgery. C) Iodophores : they are iodine complexes with anionic detergent. -“Betadine” is a commonly used iodophore .

31. v. HYDROGEN PEROXIDE Hydrogen peroxide(H 2 O 2 ) is effective against most organisms at concentration of 3-6%. It kills all organisms including spores at higher concentrations of 10-25%. MODE OF ACTION: It works by producing free hydroxyl radicals that can attack membrane lipids, DNA and other cell components.

32. USES: • For fumigation of hospitals, operation theaters, ICUs, dental clinics, OPD, blood banks, laboratories. (in conc. of 20% ) • For disinfection of surfaces, benches etc. (in conc. o f 10%) LIMITATIONS: • The concentrated product may cause skin irritation.

33. vi. PERACETIC ACID Peracetic acid is an oxidising agent. It is one of the high level disinfectants. It is also effective in the presence of organic matter. It is a more potent germicidal agent than H 2 O 2. MODE OF ACTION: It denatures the proteins, disrupts the cell wall permeability, oxidizes sulphur bonds in proteins.

34. USES: • Used to prevent biofilm formation. • Water purification • Used to sterilize automated machine e.g. hemodialyzers. LIMITATIONS: Can corrode metallic surfaces. Considered unstable, particularly when diluted.

35. vii. DYES Dyes can be divided into 2 groups- A) ANILINE DYES: i . Crystal Violet ii. Brilliant green iii. Malachite green B) ACRIDINE DYES: i . Proflavin ii. Acriflavin iii. Euflavin iv. Aminacrine

36. MODE OF ACTION: They impair the DNA complexes of the organism. USE: Dyes are used as skin and wound antiseptic. LIMITATION: Not active in presence of organic matter as pus. Not active against Mycobacteria.

37. viii. ETHYLENE OXIDE(ETO) It is a colourless liquid with a boiling point of 10.7°C. It is effective against all types of microorganisms including viruses and spores. It is highly penetrating and readily penetrates some plastics. MODE OF ACTION: Acts by alkylating the amino, carboxyl, hydroxyl and sulphydryl groups in protein molecule. It also reacts with DNA and RNA of microbes.

38. USES: Sterilization of heat labile delicate instruments. In hospitals to sterilize heart valves, respirators, lung machines, syringes, sutures, dental equipment and clothing. LIMITATIONS: ETO is toxic, inflammable, mutagenic and carcinogenic. Requires aeration time to remove ETO residue.

39. REFERENCES pediaa.com cdc.gov lentech.com waterpathogens.org/book/chemical-disinfectants CP Baveja Textbook of Microbiology Essential Microbiology Textbook by Lakshman Samaranayake

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