Chemical Disinfectants

A detailed summary of all the possible chemical disinfectants used in hospital sterilization procedures. Innovative pictures and brief explanations of all important topics clearly illustrated.........

1. Chemical Disinfectants Dr. Jasmine Vinshia Assistant Professor Department Of Microbiology Rajas Medical Institutions

2. Classification Of Chemical Agents used for Disinfection Mode of action of chemicals Classification of Instruments Levels of Disinfection & Disinfectants Brief Summary of Chemicals used for Disinfections

3. CHEMICAL AGENTS LIQUIDS 3 GASES Alcohols Aldehydes Phenols Halogens Heavy Metals Surface Active Agents Dyes Formaldehyde Ethylene Oxide

4. Protein coagulation Disruption of the cell membrane Removal of the free sulphydryl groups Substrate competition 4

5. CLASSIFICATION OF INSTRUMENTS Critical instruments Semi - c r itical Instruments Non-critical Instru m ents Penetrate the soft tissue Contact the bone Enter into or contact the blood stream They must be sterilized by autoclaving(if heat stable) or with ethylene oxide or H 2 O 2 gas(if heat sensitive) Eg: Surgical instruments, Scalers, Scissors , D ental burs , Scalpel s blades , Forceps , implants, Bone grafts Contact the mucous membrane but will not penetrate the soft tissue Glutaraldehyde is most commonly used(For high level disinfection) or alcohols(for intermediate level disinfection) Eg : Mouth mirror, impression trays, handpieces, probe , tweezers , amalgam condensers Come into contact with intact skin but not mucous membrane No risk of transmitting infections so they can be treated with low level disinfectants . Eg : X-Ray tubes, Light handles, Counter tops

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7. High-level disinfectant : This is a chemical that kills all microbial pathogens except large numbers of spores. It may have some activity against a smaller number of spores if the contact time is increased. 7 For example, glutaraldehyde and hydrogen peroxide. Uses: They are ac t i v e again s t G r a m -positive and Gra m -neg a tive b a c ter i a, sp o res and M. tuberculosis Levels Of Disinfectants

8. Inte rme d iat e - level di s i n fe c tan t : A che m ical t h at k ills a ll m ic r o b ial pathog e ns inclu d i n g mycobacteria and non-enveloped viruses except spores. For example, alcohol, phenolic compounds and iodophores. Uses: Destroys M. tuberculosis , vegetative bacteria, most viruses and fungi.

9. Lo w -le v e l dis i nf e ct a n t : A che m ic a l that k i l l s only veget a t i v e ba c te r i a , fungi and lipi d - enveloped viruses. For example, quaternary ammonium compound. Uses: Kill most bacteria and most fungi, but not M. tuberculosis or spores 9

10. ALCOHOL 70% ethyl alcohol Ethyl alcohol is active against the fungal spores and used to treat cabinets and incubator Suitable for skin preparation before venepuncture Disadvantage : . Inflammable . Mucous membrane irritant. . Promotes rusting. 34 Mechanism of Action : Denaturation of Proteins Isopropyl alcohol Used as a skin disinf e c t ant

11. A)Formaldehyde (formalin) In aqueous solution it acts as a bactericidal and sporicidal Active against Gram -ve bacteria, spores, viruses (HB, HIV) & fungi Aqueous soultion : Formalin(37% solution) - 10% formalin + 0.5% Na tetraborate used to clean metal instrument e.g. Endoscope, dialysis equipment. Gaseous form : Fumigation of wards/corridors/ICU’s DISADVANTAGE : Have pungent odour & irritating effect on 35 skin & mucous membrane. A L D E HYD E S

12. High level disinfectant Especially active against tubercle bacilli,f ungi and viruses Less toxic than formaldehyde Can be safely used to treat corrugated rubber anaesthetic tubes, face masks, metal instruments. Exposure time: > 10hrs. B.GLUTARALDEHYDE / CIDEX ( 2% alkaline NaHCO3) 12

13. C. Or t hophthalaldehyde Has bactericidal activity. It is used to cleanse endoscopes between patients as it is quick, effective and safe. 13

14. PHENOLS: A c ts b y c e l l m embrane damage thus r e l e a s ing c e l l co n t e n ts and causing lysis Eg. Cresol ( L Y S OL) ,ch l or h e xid i ne ( S A VLO N ) , ch l oro x y l e n ol (DETTOL) P henol is co m m on l y found i n m outh w ashes, scrub s o aps a nd surface disinfectants Low efficiency disinfectant Used for decontamination of the hospital environment, including laboratory surfaces, and noncritical medical items. 14

15. HALOGENS : Chlorine compounds : Bleaching powder or hypochlorite solution mostly used disinfectant for HIV infected material. in concentration of 0.05 or 0.5% used for surface material and instruments disinfection Should be prepared daily because of instability of sodium hypochlorite solution Active against bacteria, spores, fungi and viruses (HB, HIV) 38

16. IODOPHORS & IODINE Active against bacteria, spores & some viruses & fungi Suitable for skin preparation, mouthwash & as a surgical scrub ( 7.5% Povidone+iodine= Betadine) 16

17. S A L TS 17 Salts of heavy metals have toxic effect on bacteria. The salts of copper , silver and mercury are used as disinfectant. SURFACE ACTIVE AGENTS substances which alter energy relationships at interfaces,producing a reduction of surface tension, are known as surface active agents. E.g. quaternary compounds

18. ETHYLENE OXIDE Effective against all types of micro-organism including viruses and spores . R eacts with DNA and RNA (rendering them virucidal ). Potentially toxic to human beings, causing mutagenicity and carcinogenicity . It diffuses through many types of porous materials and readily penetrates some plastics. It is especially used for sterilizing heat-sensitive equipment like heart-lung machines, respirators, suture materials, dental equipment, books and clothing . Highly inflammable and explosive in concentration more than 3% and hence not used for fumigation of rooms. Thus m ixed with carbon dioxide or nitrogen to eliminate its explosive tendency 41 Gases

19. Formaldehyde gas: This is employed for fumigation of operation theatres and other rooms. The sealed room is left unopened for 48 hours after fumigation;. The gas is neutralized with ammonia(300 ml for every liter of formaldehyde used) . Fu m igation o f oper ati on t h e a tres is n o longer preferred. 19

20. Betapropiolactone : This is a condensation product of ketane and formaldehyde. It is no longer used for fumigation as it is carcinogenic. Hydrogen peroxide fogging: Bactericidal action is by oxidizing the cell wall of the organism. This has replaced fumigation. It has the advantage of short cycle time and is non- toxic.

21. Hypochlorous acid It is generated from the reverse reaction of sodium hypochlorite and hydrogen peroxide. It has bactericidal activity against common pathogenic organisms . Highly active against biofilms producing microorganisms. 21 Peracetic Acid Highly active against common antibiotic resistant bacterias such as Methicillin -resistant S.aureus , Vancomycin resistant S.aureus and Clostridium sps . Acids

22. Dyes The aniline dyes include brilliant green, malachite green and crystal violet . The are non-irritant and non-toxic to the tissues . They are inhibited by organic material . Their acidic content makes them l ethal to bacteria . 22

23. Acridine dyes They are not as selective as the aniline dyes. They are minimally affected by the presence of organic matter . They impair the DNA complexes of the organisms and prevent replication. Examples: P roflavine, A criflavine , E uflavine and A minacrine . 23

24. Hal o g e ns Iodine ( aqueous and alcoholic solution ) is widely used as a skin disinfectant . B actericidal , with moderate action against spores . Highly active against the tubercle bacteria and viruses. Iodophores ( Compounds of iodine with non-ionic wetting or surface-active agents ) have better action than aqueous or alcoholic solutions of iodine. 24

25. Chlorine and its compound hypochlorite have been used as disinfectants over time. They are markedly bactericidal and virucidal. Town water supplies, swimming pools, food and dairy industries use chlorine for disinfection. The organic chloramines are used as antiseptics for dressing wounds. 25

26. Phenols These compounds are obtained by distillation of coal tar between temperatures of 170°C and 270°C. C ause s cell membrane damage by inactivat ing membrane-bound oxidases and dehydrogenases leading to lysis and death of the microorganism . Widely used as disinfectants in hospital( Lysol and cresol). They are not readily inactivated by the presence of organic matter; hence, they are good general disinfectants 26

27. Chlorhexidine (Hibitane) is a relatively non-toxic skin antiseptic and wound dressing. They are active against most Gram-positive organisms and fairly effective against Gram-negative bacteria. 27

28. They are substances that proves lethal by reduc ing the surface tension . W idely used as wetting agents, detergents and emulsifiers. 28 Surface-active agents

29. Mechanism: These act on the phosphate groups of the cell membrane and also enter the cell. The membrane loses its semi-permeability and the cell proteins are denatured. They act on bacteria, but have no action on spores, tubercle bacilli and most viruses. 29

30. Metallic salts They are protein coagulants and have the capacity to combine with free sulfhydryl groups of cell enzymes . Thimerosal , phenyl mercury nitrate and mercurochrome are less toxic and are used as mild antiseptics and have marked bacteriostatic but weak bactericidal and limited fungicidal action. 30 Though all salts have a certain degree of heavy metals, they have a greater germicidal activity Silver, Copper and mercury salts are used as disinfectants.

31. RECOMMENDED CONCENTRATIONS DISINFECTANT CON C ENT R A TI ON Chlorhexidine 1 - 4% Ethyl Alcohol 70% Gluteraldehyde 2% Lysol 2.5% Savlon 2% Dettol 4% Bleaching powder (Calcium hypochlorite) 14 gm in 1 L water Sodium hypocholorite 1%, 0.1% Betadine (Iodophore) 2% Poviodine iodine 10% 42