Antibacterial methods
7 likes5,986 views
The document discusses antimicrobial methods for controlling microbial growth, highlighting the differences between sterilization, disinfection, antiseptics, and disinfectants. It describes various chemical agents and physical methods, including their mechanisms of action, effectiveness, and specific applications for controlling bacteria, fungi, and viruses. Additionally, it defines key terms related to antimicrobial agents and summarizes the factors influencing their efficacy.
Antibacterial methods
- 1. The control of microbial growth Antimicrobial methods and Chemotherapy For B.Sc Optometry Students
- 2. Heard of Spores? Bacterial spores are highly resistant, dormant structures (i.e. no metabolic activity) formed in response to adverse environmental conditions. They help in the survival of the organisms during adverse environmental conditions; they do not have a role in reproduction.
- 3. Two different meaning..! Sterilization is the killing or removal of all microorganisms in a material or on an object. Disinfection is the reduction of the number of pathogenic microorganisms to the point where they pose no danger of disease.
- 4. Two different meaning..! Disinfectants are typically applied to non living objects Eg: Dettol, Iodol antiseptics are applied to living tissue. Eg: ethanol, propanol, Boric acid, H2O2
- 5. An antimicrobial is an agent that kills microorganisms or stops their growth Can be chemical or physical agents What are different chemical agents
- 6. What makes them different 0.2% solution of phenol is an antiseptic and 1.0% solution of phenol is a disinfectant. A few agents are suitable as both disinfectants and antiseptics most disinfectants are too harsh for use on delicate skin tissue
- 7. Factors influencing chemical agents • Time: the length of time the organisms are exposed to the antimicrobialagent • Temperature: accelerated by increasing the temperature • pH: Incarease in pH • Concentration: increasing concentration increase the effects of most antimicrobial chemical agents
- 8. Soaps contain alkali and sodium and will kill many species of Streptococcus, Micrococcus, and Neisseria and will destroy influenza viruses. Soaps and Detergents
- 9. • Detergents are cationic and anionic • Cationic detergents are used to sanitize food utensils. Although not effective in killing spores, they do inactivate some viruses. • cationic detergents are quaternary ammonium compounds of acetate and chloride, that is they contain NH4+ • Cetyl tri methyl ammonium bromide Soaps and Detergents
- 10. • Anionic detergents are used for laundering clothes and as household cleaning agents. They are less effective than cationic detergents • Sodium alkyl sulphates:- Sodium lauryl sulphate • Sodium alkylbenzene sulphonates:- Sodium dodecyl benzene sulphonate Soaps and Detergents
- 11. Acids and Alkalis • Lactic and propionic acids retard mold growth in breads and other products. • Benzoic acid and several of its derivatives are used to prevent fungal growth in soft drinks, ketchup, and margarine. • Sorbic acid and sorbates are used to prevent fungal growth in cheeses • Boric acid, formerly used as an eyewash, is no longer recommended because of its toxicity • Soap has mid alkalinity
- 12. Heavy Metals • selenium, mercury, copper, and silver • Even tiny quantities of heavy metals can be very effective in inhibiting bacterial growth • Silver nitrate • Organic mercury compounds, such as merthiolate and mercurochrome, are used to disinfect surface skin wounds • Selenium sulfide kills fungi, including spores. Shampoos that contain selenium are effective in controlling dandruff • Copper sulfate is used to control algal growth
- 13. Heavy Metals
- 14. Halogens • Hypochlorous acid, formed by the addition of chlorine to water, effectively controls microorganisms in drinkingwater and swimming pools • Iodine is an effective antimicrobial agent. Betadine and Isodine are used for surgical scrubs and on skin before surgery • Chloramine, Bromine are other examples
- 15. Alcohols • When mixed with water, alcohols denature protein. They are also lipid solvents and dissolve membranes • Ethyl and isopropyl alcohols can be used as skin antiseptics • Alcohol disinfects but does not sterilize skin because it evaporates quickly and stays in contact with microbes for only a few seconds • 70% ethyl alcohol is usually used to disinfect a thermometer.
- 16. Phenols • Phenol and phenol derivatives called phenolics disrupt cell membranes, denature proteins, and inactivate enzymes. • Amphyl, which contains amylphenol, destroys vegetative forms of bacteria and fungi and inactivates viruses.
- 17. Phenols • orthophenylphenol in Lysol • Halogenated phenols, inhibit staphylococci and fungi • Trichlosan, made of two joined phenol rings
- 18. Oxidizing Agents • disrupt disulfide bonds in proteins and thus disrupt the structure of membranes and proteins. • Hydrogen peroxide (H2O2), which forms highly reactive superoxide O2- is used to clean puncture wounds • very effective at disinfecting contact lenses • Potassium permanganate, is used to disinfect instruments and, in low concentrations, to clean skin.
- 19. Alkylating Agents • disrupt the structure of both proteins and nucleic acids. • Eg: Formaldehyde, glutaraldehyde, and b- propiolactone are used in aqueous solutions. Ethylene oxide is used in gaseous form. It is exceedingly important that workers be protected from ethylene oxide vapors, which are toxic to skin, eyes, and mucous membranes and may also cause cancer.
- 20. Dyes • Acridine, can be used to clean wounds • Methylene blue inhibits growth of some bacteria • Crystal violet (gentian violet) blocks cell wall synthesis. Used to treat yeast and protozoan infections
- 21. Two different meaning..! Bacteriostatic agent An agent that inhibits the growth of bacteria. Bactericide An agent that kills bacteria. Most such agents do not kill spores
- 22. Mechanism of action In denaturation, hydrogen and disulfide bonds are disrupted, and the functional shape of the protein molecule is destroyed. There are two types of denaturation Protein Denaturation
- 23. Mechanism of action Protein Denaturation
- 24. Chemical agents Way of denaturation Acids (boric acid, and strong alkalis ) destroy protein by hydrolyzing Oxidizing agents (H2O2) oxidize disulfide linkages Halogens act as oxidizing agents Heavy metals (Hg and Ag) attach to sulfhydryl groups. Alkylating agents donate –CH3 groups to proteins Halogens substituted for hydrogen in carboxyl (-COOH), sulfhydryl, amino (—NH2), and alcohol (—OH) groups Mechanism of action Protein Denaturation
- 25. Mechanism of action Chemical agents can impart antimicrobial effect by either destroying membrane proteins or dissolving lipids • Surfactants are soluble compounds that reduce surface tension. They can dissolve lipids Eg: Quats, Soaps, Detergents • Phenols and alcohols can denature protein and dissolve lipids Reactions That Affect Membranes
- 26. Mechanism of action Virus inactivation can be effected by destroying either the viruses’ nucleic acid or their proteins. • Alkylating agents such as ethylene oxide, nitrous acid, and hydroxylamine, act as chemical mutagens—they alter DNA or RNA • Detergents, alcohols, and other agents that denature proteins Reactions That Affect Viruses
- 27. ? What are different Physical agents 1. Dry heat, moist heat, and pasteurization 2. Refrigeration, freezing, drying, and freeze-drying 3. Radiation 4. Filtration 5. Sonic and ultrasonic waves 6. Osmotic pressure
- 28. • It is usually used to sterilize metal objects and glassware and is the only suitable means of sterilizing oils and powders • Objects are sterilized by dry heat when subjected to 171°C for 1 hour, 160°C for 2 hours or longer, or 121°C for 16 hours Dry Heat
- 29. Dry Heat Hot air oven is used for dry heat sterilization
- 30. • because of its penetrating properties, is a widely used physical agent • At 15 lb/in the temperature reaches 121°C, which kill spores, as well as living microbes, and to disrupt the structure of nucleic acids in viruses. This is achieved using autoclave • heat-resistant endospores, such as those of Bacillus stearothermophilus, to check autoclave performance Moist Heat
- 31. Moist Heat
- 32. Moist Heat
- 33. • a process invented by Pasteur to destroy organisms that caused wine to sour • Pasteurization does not sterilize a beverage, but it does kill any pathogens present and drastically slows spoilage by reducing the level of microorganisms. • Heated upto 60°C then cool down immediately • Ultra high temperature (UHT) processing raises the temperature from 74 to 140°C andthen drops it back to 74°C in less than 5 sec. Pasteurization
- 34. • Cold temperature retards the growth of microorganisms by slowing the rate of enzyme- controlled reactions but does not kill many microbes • Many fresh foods can be prevented from spoiling by keeping them at 5°C • storage should be limited to a few days because some bacteria and molds continue to grow at this temperature Refrigeration
- 35. • Freezing at -20°C is used to preserve foods • slow the rate of chemical reactions so that microorganisms do not cause food to spoil • Microorganisms are usually suspended in glycerol or protein • cooled with solid carbon dioxide (dry ice) -78°C • they can be placed in liquid nitrogen and cooled to -180°C. F r e e z i n g
- 36. • the absence of water inhibits the action of enzymes • Yeast used in baking also can be preserved by drying • Treponema pallidum is sensitive to drying • Drying of laundry in dryers or in the sunshine also destroys pathogens Drying
- 37. • is the drying of a material from the frozen state • rapidly frozen in alcohol and dry ice or in liquid nitrogen, are then subjected to a high vacuum to remove all the water while in the frozen state, and finally are sealed under a vacuum. • Microbiologists use lyophilization for long-term preservation of microbes • Instant coffee, tea are made this way lyophilization
- 38. • Four general types of radiation—ultraviolet light, ionizing radiation, microwave radiation, and strong visible light • Ultraviolet (UV) light consists of light of wavelengths between 40 and 390 nm but 200nm is most lethal • UV is absorbed by the purine and pyrimidine bases of nucleic acids - permanently destroy these molecules. • Effective in inactivating viruses. • Kills fewer bacteria because of DNA repair mechanisms. Radiation
- 39. • X rays (0.1 to 40 nm) and gamma rays • Ionizing radiation damages DNA and produces peroxides which act as powerful oxidizing agents in cells • It is used to sterilize plastic laboratory & medical equipment and pharmaceutical products Ionizing Radiation
- 40. • the passage of a material through a filter, or straining device • Membrane filters: used to sterilize materials likely to be damaged by heat sterilization. • Like media, special nutrients that might be added to media, and pharmaceutical products such as drugs, sera, and vitamins • Cellulose acetate filters with extremely tiny pores are capable of removing viruses from liquids. 1Filtration
- 41. Some Defenitions • Sterilization: The killing or removal of all microorganisms in a material or on an object. • Disinfection: The reduction of the number of pathogenic microorganisms to the point where they pose no danger of disease. • Antiseptic: A chemical agent that can safely be used externally on living tissue to destroy microorganisms or to inhibit their growth. • Disinfectant: A chemical agent used on inanimate objects to destroy microorganisms. Most disinfectants do not kill spores. • Sanitizer: A chemical agent typically used on food-handling equipment and eating utensils to reduce bacterial numbers so as to meet public health standards. Sanitization may simply refer to thorough washing withonly soap or detergent.
- 42. Some Defenitions • Bacteriostatic agent: An agent that inhibits the growth of bacteria. • Germicide: An agent capable of killing microbes rapidly; some such agents effectively kill certain microorganisms but only inhibit the growth of others. • Bactericide: An agent that kills bacteria. Most such agents do not kill spores. • Viricide: An agent that inactivates viruses. • Fungicide: An agent that kills fungi. • Sporocide: An agent that kills bacterial endospores or fungal spores.