Disinfection and Disinfectants Chapter 4 Introduction Places like

Disinfection and Disinfectants Chapter 4

Introduction • Places like-– Farrowing houses, nursery units, and dairy calfrearing facilities-– Very Vulnerable for infection • Health problems can become severe • Problems can be transmitted to others.

Removing Organic Materials • 1 st requirement in disinfection-– start with clean surroundings and surfaces. – NO Substitute for this. • NO disinfectant applied to dirty surface-– will destroy all germs. • Organic matter found in dirt, manure-– protects the infective organism against germkilling activity of disinfectant.

Removing Organic Materials • Cleaning done with shovel or broom. • Can use high pressure pumps or detergents. – High velocity stream of water--remove dirt. – Steam effective cleaner. – When used alone, only effective (killing) when applied directly through nozzle not more than 6 -8 inches away.

Removing Organic Materials • Excessive manure-– sanitation more effective by using detergents. • Detergents hasten dirt removal by-– increasing the wetting speed & breaking down organic material into small particles. – Act similarly on proteins, fats, and carbs by emulsifying and suspending them. – Thus, they are removed, allowing disinfectant to penetrate and kill infective agents.

Removing Organic Materials • Selection is important (disinfectant). • Buildings, should work well in presence of– organic matter – be compatible with detergents and soaps – be harmless to building materials. – Be relatively non-toxic.

Phenol Coefficient • Killing strength of a disinfectant compared to Phenol (Carbolic Acid). • Indicated how many times more (or less) the disinfectant can be diluted than phenol and still retain an equal disinfecting value. • Coefficient determined by-– comparing disinfectant with Phenol on Typhoid fever germ (Salmonella typhi)

Phenol Coefficient • Low phenol coefficient indicates-– inferiority of a product – Can’t be said that high p. c. means superiority because are in laboratory condition. • May not be in the “real world”

Germicidal Action • Modes of action of disinfectants-– 1. By oxidation--gain oxygen from itself or another source and combine chemically with germ and oxidize or burns it. – 2. Removal of water--take water from germ. – 3. By coagulation--fluid of substance changed to soft jelly-like solid, inhibition of life. – 4. By chemical reactions--react to form new complex compounds free from harmful qualities.

Desirable Characteristics of Disinfectants • Ideal one not discovered. Ever? • Some desirable features of disinfectant-– 1. Reasonable low priced, large quantities. – 2. Free from strong/objectionable odors • products tainted – 3. Must not be excessively destructive to materials or tissues other than agent disinfecting. • Carbolic acid, destroy infections, and tissues

Desirable Characteristics of Disinfectants – 4. Must not remain poisonous after application – 5. To remain active, must not combine chemically with materials, utensils, blood. – 6. Must be neither irritating or poisonous when inhaled. Some are (chlorine, formaldehyde). – 7. Must be effective at ordinary temps but not lose effectiveness on a “mild day”

Desirable Characteristics of Disinfectants – 8. Must be effective after diluted with water • must not be effective only when concentrated. – 9. Must mix readily and uniformly with water. • Some remain on the surface. – 10. Must be in a form that is easily and economically transported.

Chemical Disinfectants • Lethal action due to capacity to-– react with protein and essential enzymes of MO – Anything that will coagulate, precipitate or denature proteins will act as disinfectant. – Swine scald – Denatures the protein, is disinfectant in pork slaughter to the skin.

Chemical Disinfectants • Four Primary Chemical Groups that possess the ability to denature, coagulate…. . – 1. Phenols – 2. Halogens – 3. Quaternary ammonium compounds – 4. Formols. – Others such as dyes, heavy metals, soaps and alcohols possess ability to do this.

Chemical Disinfectants • Common characteristic-– that at progressively weaker concentrations, their lethal activities become slower/less effective. • Ultimate effect, whether bactericidal or bacteriostatic, determined by-– 1. – 2. – 3. Concentration Contact time Temperature

Phenols • Includes: • Coal Tar Oils-– including carbolic aid, cresol and pine oil.

Carbolic Acid • Derived from coal tar oils. • Kept liquid in salable condition in stores. – By liquefying it through exposure to heat then by adding 10% either water or glycerin. • One of oldest known disinfectants. • Dr. Lister, pioneer surgeon-– used for keeping wounds from infection.

Carbolic Acid • Very stable compound. – Suffers no deterioration from air/light exposure. • Does not injure fabrics immersed in. • Effective against germs-– in presence of organic matter. – Only if enough exposure time (24 h) • Readily available in drug stores

Disadvantages of Carbolic Acid • 1. Extremely poisonous-– unsafe on premises • 2. Has penetrating odor-– readily absorbed by milk, meat, wool. • 3. Low efficiency when in cold solution – effective as hot • 4. Not effective against viruses that cause-– foot-and-mouth, fowlpox, etc.

Cresol • • Derived from coal tar. Effective against many bacteria & viruses. Advantages-1. Metals not corroded by it. – Surgical instruments • 2. Almost non-irritant to skin – when used at recommended strength. – Also soapy, aids in penetration.

Cresol • Continued (Advantages) • 3. Less poisonous and more germicidal than carbolic acid. • 4. As deodorant, destroys putrefactive germs and replaces bad odor. • 5. Cost is low. • Principle disadvantage--odor will taint all foods in same room.

Halogens • • • Include the following four substances-1. Iodine 2. Chlorine 3. Bromine 4. Fluorine

Iodine • Resublimed iodine has phenol coeff of-– 170 to 235. • One of few that is immediately destructive to bacterial spores-– highly resistant to anything. • Lowers the natural resistance of skin to germs. • Efficient in application to ringworm or lumpy jaw.

Chlorine • Chlorinated lime (AKA bleach)-– powerful disinfectant, due to amount of chlorine gas. – Also good deodorant. • Disadvantages-- (especially in stables) – Expense compared to quantity used, bleaching characteristics (white), corrosive to metals, irritation to mucous membranes of nose and throat, disagreeable odor (milk, meat), instability of chlorine content.

Chlorine • Phenol coefficient of 21. • Evidence that destroys viruses like– foot-and-mouth, and others. • May be used in powdered form or dissolved in water.

Quaternaries • Emerged into prominence. • Large group, cationic in nature with a high surface activity. – “Surface Active Cationic Germicides” • Bactericidal action attributed to-– inactivation of enzymes, denaturing of essential proteins and disruption of cell membrane. – Leakage.

Quaternaries • Antibacterial activities are suppressed in presence of organic materials. • Due to chemical make-up-– NEVER use with soaps. • More effective against Gram-positive organisms than Gram-negative.

Gram-positive vs Gram-negative • Gram’s method--staining germs for identification. • When stain washed off by alcohol-– Gram-negative – those not decolorized--Gram-positive • While Quats effective on bacteria and fungi, do not always kill spores, have trouble with viruses (Some evidence kill Newcastle Vir)

Formols • Formaldehyde is a gas that’s soluble in water. – Water solution of gas known as Formalin • Effective disinfectant • Advantage-– being lethal to viruses, bacteria, fungi, SPORES. – Highly reactive to AA’s and proteins. – Humidity important factor--increased, activity of formaldehyde gas increases.

Other Chemical Substances • Sodium Orthophenylphenate- • Combines with detergents to provide-– effective one-step sanitation program. • • • No objectionable odor Readily soluble in water High germicidal activity Active in presence of detergents Performs well in presence of organic matter IS irritating to eyes and mucous membranes

Sodium Orthophenlyphenate • Effective against-– brucellosis, tuberculosis, vesicular exanthema and vesicular stomatitis. • Approved for use in federal-state animal disease eradication programs. • Is official disinfectant for many or most livestock shows.

Lye • Highly used in form of household lye. • Highly rated against viruses. – F-a-m, fowlpox, dog distemper. • And germs -– like anthrax (and its spores) and brucellosis. • Most effective when solution is at room temperature than hot.

Vinegar • Of a good grade should be 5 -6% acetic acid – compares favorably with official diluted acetic acid, which is preferable due to-– colorless, greater purity, uniform strength (6%) • Diluted acetic acid not always available-– Vinegar? • Value against germs, preserving pickles. – Applied to wounds and kills pus-producing ones, used for foot-rot early.

Non-Chemical Disinfectants • Are two N-C methods that are aids to disinfection or actually disinfect. • 1. Mechanical agencies • 2. Natural Agencies.

Mechanical Agencies • These include the processes of-– sweeping, brushing, scraping, scrubbing and using water under pressure. • Best method is to-– dampen all materials to use mechanical method – than transport somewhere – dampening prevents germs being transported in dust. – Dampening better than water under total pressure, flush germs into clean areas.

Natural Agencies • Sunlight-– kill germs and spores if reaches them. – UV rays can’t pass through glass or haze. – Ineffective during early morning and evening. – Effective only against surface infections. – Do not penetrate- • mucus, manure, dirt, organic materials, etc. – Very slow

Heat • If in sufficient concentration-– HEAT, is deadly to all forms of life – including parasites and germs. • Highly effective as steam under pressure or scalding water. • Utilized in pasteurization, burning of carcasses, destruction of buildings.

Two Types of Pasteurization • 1. Holding method-– most general use – heating product for duration of 30 min to temperature of 140 -148 F, average temperature of 143. 8 F • 2. High-temperature-short-time-– AKA “Flash Method” – quickly heated to high temperature and held. – High-frequency alternating electrical current of 2500 to 6000 v through milk, reaching 161 F and holding temp for 15 sec.

Sedimentation • Nature’s way of purifying water not in motion. • Germs settle to the bottom where in time they die. • Must not be depended upon in small pool or ponds, can be repeatedly infected.

Time • All living things must die. • Of course, this is variable, may take several years. • Germ responsible for brucellosis-– will live in frozen pastures for several months though only brief period in warmer months. • Extreme dryness accounts for death of many more germs.

Electricity • Destructive to germ life by-– its heat-generating ability – power to to free elements from chemical combinations (Chlorine (salt)). – Direct action of the electrical current.

Bodily Juices • Those considered include: – blood serum, white blood cells (phagocytes), red blood cells, and gastric juice. • Blood serum kills germs. • White blood cells “eat” or ingest germs in blood stream-– gradually grow around germ and disposing. – White cell wins, animal resists infection, doesn’t win, disease sets in. • Gastric juices--being an acid, destructive.

Antibiotics • Are anti-bacterial substances of biological origin derived from: – 1. – 2. – 3. – 4. Bacteria (pyocyanese, tyrothricin, bactracin) Actinomyces (antinomycin, streptomycin) Molds and fungi (penicillin and flavicin) Laboratory synthesis (amipicillin, neomycin)

Antibiotics • Can be obtained from natural substances other than bacteria. • Allicin--common garlic • Canavalin--soybean flour • Chlorellin--fresh water seaweed • Lysozyme--saliva, tears, egg whites

Antibiotics • Best known antibiotic-– Penicillin (Penicillum notatum) – Used for infections due to staphylococci, streptococci, pneumococci, Gram-positives. • Animals, extensively used for mastitis. • Amoxicillin and Ampicillin-– members of penicillin family – derived semi-synthetically--active against large numbers of Gram Positive and Negative bact. • May be destroyed by penicillinases produced by bact

Antibiotics • Streptomycin-– derived from Actinomyes (streptomyces) riseus. – Effective against Gram-negative organisms; not as effective against G-Pos as penicillin. • Oxytetracycline-– very broad antibiotic – effective against large #’s of GP and GN organisms.

End of Chapter 4