Disinfectants- Pharmaceutical Microbiology

DISINFECTANTS are chemical agents that inhibit or kill microorganisms (surgical apparatus, periphery of the patient, and the objects used by the patient).
Disinfection It is the application of chemicals to destroy most pathogenic organisms on inanimate surfaces
Can be accomplished by application of chemical agents, use of physical agents (ionizing radiation) dry or moist heat, superheated steam(autoclave, 120̊ C)

idela surfactant
effective at room temperature,
noncorrosive and nontoxic,
inexpensive,
capable of killing the vegetative form of all pathogenic organisms,
require limited time of exposure

1. DISINFECTANTS BY- SANCHIT DHANKHAR

2. Disinfection DISINFECTANTS are chemical agents that inhibit or kill microorganisms (surgical apparatus, periphery of the patient, and the objects used by the patient). Disinfection It is the application of chemicals to destroy most pathogenic organisms on inanimate surfaces Can be accomplished by application of chemical agents, use of physical agents (ionizing radiation) dry or moist heat, superheated steam(autoclave, 120̊ C) 2

3. IDEAL DISINFECTANT effective at room temperature, noncorrosive and nontoxic, inexpensive, capable of killing the vegetative form of all pathogenic organisms, require limited time of exposure 3

4. PROCESS OF DISINFECTION Prevents infection by reducing the number of potentially infective organisms either by killing, removing or diluting them. Application of chemical agent Use of ionizing irradiation, dry or moist heat or superheated steam (autoclave, 120 ◦ C) -PHYSICAL- 4

5. Disinfectants with their mechanism Chemical MOA ALCOHOLS (70%) e,g,Ethyl alcohol, isopropyl alcohol Alcohols dehydrate cells, disrupt membranes and cause coagulation of protein ALDEHYDES Examples: 40% Formaldehyde, Gluteraldehyde Acts through alkylation of amino-, carboxyl- or hydroxyl group, and probably damages nucleic acids. PHENOL: Examples: 5% phenol, 1-5% Cresol, 5% Lysol Act by disruption of membranes, precipitation of proteins and inactivation of enzymes HALOGENS They are oxidizing agents and cause damage by oxidation of essential sulfydryl groups of enzymes. HEAVY METALS Examples: Mercuric chloride, silver nitrate Act by precipitation of proteins and oxidation of sulfydryl groups. SURFACE ACTIVE AGENTS: They have the property of concentrating at interfaces between lipid containing membrane of bacterial cell and surrounding aqueous medium, disrupt membrane resulting in leakage of cell constituents. Examples: These are soaps or detergents. ETHYLENE OXIDE It is an alkylating agent. It acts by alkylating sulfydryl-, amino-, carboxyl- and hydroxyl- groups. BETA-PROPIOLACTONE (BPL) It is an alkylating agent and acts through alkylation of carboxyl- and hydroxyl- groups. HYDROGEN PEROXIDE: It acts on the microorganisms through its release of nascent oxygen. Hydrogen peroxide produces hydroxyl-free radical that damages proteins and DNA. 5

6. HALOGENS The halogens and halogen – releasing compounds include some of the most effective antimicrobial compounds used for disinfection and antisepsis. Iodine and chlorine are the most effective halogens with bromine and fluorine being less active. Because of the irritating nature of the products of sodium hypochlorite , it is currently used primarily as a disinfectant. 6

7. IODINE Tincture of iodine (2g I, 2.5 g NaI and 50% ethanol to 100 mL). Powerful antiseptic for intact skin, should avoid contact with mucosas. Can cause serious hypersensitivity reactions, staining of skin and dressing can happen and this limits its use. 7

8. Iodophores less irritating less hypersensitivity compared to tincture of iodine. Povidon iodine (A complex of I with polivinyl pyrrolidone-surface active agent-). Can be used as antiseptics or disinfectants. Kill vegetative bacteria, mycobacteria, fungi, lipid containing viruses. They kill spores as well on prolonged use Iodine and other free halogens oxidize the –SH groups of proteins and enzymes and produce -S-S- bonds and disrupts the structure and function of these 8

9. CHLORINE Chlorine is a strong oxidizing agent. Hypochloric acid and sodium hypochlorite (household bleach 5.25%) are bactericidal and effective disinfectants 1:10dilutions it provides 5000 ppm of chlorine. This is the concentration recommended for disinfection of blood spills . Dilutions are made with tap water and when the opaque bottle is tightly closed it preserves its activity. 9

10. < 5 ppm kills vegetative bacteria 5000 ppm is needed to kill spores 1000-10,000 ppm is tuberculocidal 100 ppm kills vegetative fungal cells in 1 h 500 ppm kills fungal spores 200-500 ppm inactivate viruses HOCl is the active form, pH↑ less active OCl- is formed →blood serum feces protein containing materials should be removed from surfaces 10

11. ALCOHOLS Ethyl alcohol (70% [60-90]) and isopropyl alcohol are effective antiseptic and disinfectant agents. They reduce the number of bacteria 90% when applied to the skin. They rapidly kill vegetative bacteria, M tuberculosis, many fungi and inactivate lipophilic viruses. They denature proteins and disturb the membrane permeability of bacteria. They are not effective as sterilizing agents because of their inefficient antibacterial spectrum CDC →alcohol based hand rubs 11

12. They are flammable and must be stored in cool and well ventilated places. They can damage corneal tissue if directly applied, therefore instruments that will be used in the eye must be free of alcohol before use. 12

13. ALDEHYDES 2-8% of formaldehyde can be used as a sterilizing agent for surgical instruments. Not corrosive for metal, plastic or rubber. Broad spectrum of activity against microorganisms and viruses. Alkylate chemical groups in proteins and nucleic acids. It is especially useful for instruments that can not be autoclaved. (hemodialyzers, dental handpieces, respiratory therapy equipment). 3% solution is useful topically on hands and feet in treatment of hyperhidrosis. Presence of organic material, low conc, and perfusion inefficiency can cause failure. Formaldehyde is marketed as the 34-38% solution and is called formol and contains methyl alcohol in order to prevent polymerization and precipitation of formaldehyde. 13

14. Formaldehyde has a pungent odor and is highly irritating to repiratory mucous membranes and eyes at conc 2-5 ppm is rarely used because of its toxicity and tendency to cause sensitization with repeated contact. The relative risk of formaldehyde as a human carcinogen when used as a disinfectant is significant (OSHA). 14

15. Glutaraldehyde 2% w/v pH7.4-8.5 is not significantly affected by the presence of organic material and is relatively nonirritating, nonallergenic and noncorrosive when proper safeguards are employed. Activated solutions are bactericidal, sporicidal, fungicidal and virucidal. Exposure of skin and mucus membranes can cause sensitization, irritation and damage. Protection of health care workers from exposure to glutaraldehyde conc>0.2 ppm is advised It is important to use it only in well – ventilated areas and never using it as a surface disinfectant. 15

16. OXIDIZING AGENTS Hydrogen peroxide is the most common of a number of oxidizing compounds that have been used as antiseptics. It is also effective in injured skin due to its bubbling effect. 3% solution is effective Concentrations potentially useful for antisepsis are effective against vegetative bacteria, higher concentrations are sporicidal Disinfection of respirators, acrylic resin implants, plastic eating utensils, soft contact lenses, cartons for milk or juice 10-25% conc is sporicidal 16

17. PHENOLS Phenol is the oldest surgical antiseptic but is no longer used even as a disinfectant because of its corrosive effect on tissues and its carcinogenic effects. Phenolic derivatives (o-phenylphenol-coal tar distillates- etc) can be used. Skin absorption and skin irritation still occurs with these derivatives. Detergents are added to formulations to clean and remove organic material that may decrease the activity of these compounds. 17

18. They are bactericidal , fungicidal and inactivate lipophilic viruses. Not sporicidal. Used on floors, beds, countertops and benchtops Disrupt cell walls and membranes, precipitate proteins and inactivate enzymes Hexachlorophen as skin disinfectant has no longer been used because of its neurotoxic effects 18

19. Chlorhexidine Chlorhexidine was approved for use in surgical scrubs It is highly effective against gram-positive organisms, vegetative bacteria, mycobacteria, moderately active against fungi and viruses, spore germination is also inhibited. Strongly adsorbs to bacterial membranes and causes leakage of small molecules and precipitation of cytoplasmic proteins. 19

20. Water soluble chlorhexidine digluconate is used as an antiseptic. Most effective against gram- positive cocci and less active against gram-positive and gram-negative rods, spore germination is also inhibited.It strongly adsorbs to bacterial membranes and causes leakage of small molecules and precipitation of cytoplasmic proteins. It is resistant to inhibition by blood or organic material. Anionic or nonanionic agents in moisturizers, soaps,surfactants neutralize its action. Used in oral rinses, should not be used during surgery of the middle ear, causes sensorineural deafness. 20

21. SURFACE ACTIVE AGENTS These are compounds that produce a detergent effect. They are quaternary ammonium compounds . Cationic agents were used as cold sterilization solutions. But they are ineffective against bacterial spores, tubercle bacilli, fungi, viruses and many gram-negative bacteria. The bactericidal action of these compounds is due to inactivation of energy-producing enzymes, denaturation of proteins and disruption of cell membrane. Cetylpyridinium chloride, benzethonium chloride and similar cationic agents are used in mouth rinses and sore throat remedies. 21

22. They bind to the surface of colloidal protein in blood, serum, milk and to fibers in cotton, mops, cloths and paper towels (inactivation). Anionic detergents also inactivate them. They are also used for sanitation of floors and bench tops. Since their toxicity is low they are used as sanitizers in food production facilities. Polyhexamethylene biguanide used in drop form for acanthamoeba keratitis. 22

23. HEAVY METALS Mercury and silver compounds were used as antimicrobial agents. Silver nitrate was commonly used in dentistry to treat oral ulcers but is no longer used because it delays healing and alters cellular morphology. In medicine, silver nitrate eyedrops remain useful in the prophylaxis of gonococcal infection in the newborn. 23

24. Mercury is an environmental hazard, however, thiomersal (0.001-0.004%) is still used as a preservative of vaccines, antitoxins and immune sera Benzoic acid and salts, parabens -alkyl esters of p-hydroxybenzoic acid Sorbic acid and salts, phenolic compounds Quaternary ammonium compounds, alcohols also used 24

25. Tests to evaluate disinfectants/ bactericidal/ virucidal /fungicidal agents Rideal walker test C hick martin test Kelsey sykes method Use dilution method 25

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27. Phenol is diluted from 1:400 to 1:800 and the test disinfectant is diluted from 1:95 to 1:115. Their bactericidal activity is determined against Salmonella typhi suspension. Subcultures are performed from both the test and phenol at intervals of 2.5, 5, 7.5 and 10 minutes. The plates are incubated for 48-72 hours at 37°C. That dilution of disinfectant which disinfects the suspension in a given time is divided by that dilution of phenol which disinfects the suspension in same time gives its phenol coefficient. 27

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29. Kelsey-Sykes test Kelsey-Sykes test is acapacity use dilution test , designed to determine concentrations of disinfectant that will be effective in clean and dirty conditions. The disinfectant is challenged by three successive additions of a bacterial suspension during the course of the test. The duration of test takes over 30 minutes to perform. The concentration of the disinfectant is reduced by half by the addition of organic matter (autoclaved yeast cells), which builds up to a final concentration of 0.5%. Depending on the type of disinfectant, a single test organism is selected from S. aureus , P. aeruginosa , P. vulgaris and E. coli . The method can be carried out under 'clean' or 'dirty' conditions. The dilutions of the disinfectant are made in hard water for clean conditions and in yeast suspension for dirty conditions. Test organism alone or with yeast is added at 0, 10 and 20 minutes interval. The contact time of disinfectant and test organism is 8 min. The three sets of five replicate cultures corresponding to each challenge are incubated at 32 o C for 48 hours and growth is assessed by turbidity. The disinfectant is evaluated on its ability to kill microorganisms or lack of it and the result is reported as a pass or a fail and not as a coefficient. Sets that contain two or more negative cultures are recorded as a negative result. The disinfectant passes at the dilution tested if negative results are obtained after the first and second challenges. The third challenge is not included in the pass/fail criterion but positive cultures serve as inbuilt controls. If there are no positive cultures after the third challenge, a lower concentration of the disinfectant may be tested. 29

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31. USE DILUTION TEST :- These test are the oldest test . AOAC used dilution test is a carrier based test. S.aureus , Pseudomonas aeruginosa , Salmonella choleraesuis bacteria culture is used. Metal ring dipped into microbial culture . Dried at 37°C Dipped in solution of disinfectant for 10min. Ring is washed & placed into tube of medium for 48 hours. 1.Growth occur – less effective disinfectants . 2. No Growth occur – more effective disinfectants 31

32. THANKYOU 32