Disinfection

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Disinfection

The process of destruction of vegetative forms of the Pathogenic bacteria
High level, intermediate, low level
High level – instruments that does not with- stand sterilization e.g endoscopes, cystoscopes – Gluteraldehyde, hydrogen peroxide, peracetic acid etc.
Intermediate-level disinfection- semicritical instruments (laryngoscope, vaginal speculum, anesthesia breathing circuits)- alcohols, iodophor, phenolic compounds
Low-level disinfection  -  Stethoscope, ECG electrodes, cuffs
Mechanism of action
Protein coagulation
Disrupt cell membrane
Removal of sulphydryl group
Substrate competition
Alcohols
Ethyl alcohol (ethanol) / isopropyl /Methyl
Skin antiseptics
Protein denaturing
No action on spore
Conc. 60-90%
Methyl- fungal spores
Aldehydes-Formaldehyde
Lethal to all bacteria + spores + virus
Aqueous / gas forms- acts on amino group.
Gas- wollen blankets, wool and hides, foot wear of person with fungal infection, wards and operation theatre, Anesth. Machine, incubators, safety biocabinets
Formalin (40% forlmaldehyde) +KMnO4- fumigation
Formalin
Commercial formalin-40% formaldehyde gas in water +methanol
10%  solution is used
Bacterial cultures and suspension, cleaning contaminated surface, preservation of tissues, sterilization of bacterial vaccines, preparation of toxoid
Aldehyde-cont.
Gluteraldehyde – Bacteria (TB), viruses, fungi, spores- slow action
Cystoscopes,bronchoscopes, endoscopes, corrugated rubber anesth. Tubes, plastic endotracheal tubes, face mask, metal instruments, polythene tubing
Precautions- irritant to eye, skin, resp.mucosa
Betapropriolactone(BPL)
It is a condensation product of ketane and formaldehyde having boiling point 163˚C
Fumigation
Carcinogenic
Oxidizing agents
Hydrogen peroxide:- 3-6%  kills most organisms, 10-25% sporicidal
Liberates free hydroxyl radical
Plastic implants, contact lenses, surgical prosthesis
Halogens
Chlorines and iodine
Bactericidal
Moderate action against spores
Chlorine -  Cl2, HOCl, OCl¯
Hypochlorite- (house hold bleach)- 1-2% lab disinfection,
Halogens-contd.
Aqueous iodine, tincture iodine (iodine 25%, pot. Iodide & ethanol)
Iodophore – are chemical complexes with iodine bound to polyvinylpyrolidone or ethoxylated non ionic detergents (poloxamer)
Antiseptic, conjunctivis
Phenolic compounds
Phenol 1% (carbolic acid)
Cresols (Lysol)
Chloroxylenol ( Dettol)
Chlorohexidine
Hexachlorophane
Cell membrane damage
Quaternary ammonium compound
Distrupt cell membrane
Bacteriostatic at low , cidal at high conc
Benzalkonium chloride, cetylpyridinium chloride
Cleaning agents
Surface active agents
Alter energy at interface producing reduction of surface tension
Anionic, cationic, nonionic and amphoteric
Acts on phosphate groups and disrupt cell membrane- lysis of cell
Cetrimide, savlon ( cetrimide + chlorhexidine)
Anionic - soap
Testing of Disinfection
Phenol coefficient
Salmonella typhi & Staph. aureus
Phenol coefficient 1, > 1,<1
Lysol 5
Dilution of Disinfectant,add 0.5ml of the organism
Filter paper method
Use Dilution Method

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