Week 7 Microbial Control PDF

Our Lady of Fatima University College of Pharmacy Pharmaceutical Microbiology and Parasitology PHMP211 MICROBIAL CONTROL Microbial Control MICROBIOLOGY INTRODUCTION METABOLISM ANTIBIOTICS AND HISTORY GROWTH INFECTIONS DIVE...

Our Lady of Fatima University College of Pharmacy Pharmaceutical Microbiology and Parasitology PHMP211 MICROBIAL CONTROL Microbial Control MICROBIOLOGY INTRODUCTION METABOLISM ANTIBIOTICS AND HISTORY GROWTH INFECTIONS DIVERSITY OF MICROBIAL MICROORGANISMSCONTROL GUT INFECTIONS CONTROL IMMUNOLOGY RESPIRATORY INFECTIONS SKIN & EYES INFECTIONS CARDIOVASCULAR AND LYMPHATIC GIT CNS INFECTIONS INFECTIONS INFECTIONS Microbial Control MICROBIOLOGY UNIT OUTCOME At the end of this lecture, the students should be able to: Define the key terms related to microbial control Compare the effectiveness of moist heat (boiling, autoclaving, pasteurization) and dry heat Describe how filtration, low temperatures, high pressure, desiccation, and osmotic pressure suppress microbial growth Explain how radiation kills cells Microbial Control MICROBIOLOGY UNIT OUTCOME Identify the mechanisms of action and preferred uses of chemical disinfectants. Microbial Control MICROBIOLOGY UNIT OUTLINE 1. Terms Related to Microbial Control 2. Physical Methods of Microbial Control 3. Chemical Methods of Microbial Control HISTORY Microbial Control Microbial Control GERM THEORY OF DISEASE - diseases may result from microbial infection Girolamo Fracastoro - proposed, in 1546, that seed-like “spores” may be transferred between individuals through direct contact, exposure to contaminated clothing, or through the air - early notion of germ theory of disease Microbial Control GERM THEORY OF DISEASE Ignaz Semmelweis - promoted washing of hands before medical procedures (childbirth) to prevent puerperal fever to mothers Microbial Control GERM THEORY OF DISEASE John Snow - conducted studies to track the source of cholera outbreaks in London Microbial Control GERM THEORY OF DISEASE Joseph Lister - introduced aseptic surgery (he insisted on handwashing and extreme cleanliness during surgery) - began using carbolic acid as antiseptic during surgery Louis Pasteur Robert Koch Microbial Control GOLDEN AGE OF MICROBIOLOGY Pasteur Developed vaccines for rabies in animals and humans Pasteurization - a process used to kill microorganisms responsible for spoilage Microbial Control Robert Koch - was the first to demonstrate the connection between a single, isolated microbe and a known human disease - discovered the bacteria that cause: Anthrax Cholera Tuberculosis Microbial Control AGE OF VACCINE Pasteur – also developed vaccine for fowl cholera, rabies, and anthrax Edward Jenner – first to commercialized vaccine (cowpox scabs) against smallpox Emil von Behring – diphtheria used to be the major caused of child death until a diphtheria antitoxin was developed by von Behring Microbial Control AGE OF CHEMOTHERAPEUTICS Paul Ehrlich – salvarsan Alexander Fleming – penicillin Howard Florey and Ernst Boris Chain – helped in isolating penicillin subsequently won the Nobel Peace Prize with Fleming Gerhard Domagk – sulfanilamide (Prontosil®) Selman Waksman – streptomycin MICROBIAL CONTROL Related Terms Microbial Control MICROBIAL CONTROL Sterilization the removal or destruction of ALL living microorganisms Commercial Sterilization Sufficient heat treatment to kill endospores of Clostridium botulinum in canned food Sanitization Treatment is intended to lower microbial counts on eating and drinking utensils to safe public health levels Microbial Control MICROBIAL CONTROL Disinfection Destruction of vegetative pathogens on inanimate objects Antisepsis Destruction of vegetative pathogens on living tissue Microbial Control OTHER RELATED TERMS “-cide” – meaning to kill; treatment that causes death of microorganisms Biocide or germicide – kills microorganisms in general Fungicide – kills fungi “-stat or -stasis” – meaning to stop or to steady; treatment that inhibits growth and multiplication of microorganisms Fungistatic – inhibits mold Bacteriostat – Inhibits multiplication of bacteria Microbial Control OTHER RELATED TERMS Degerming – removal of microbes from a limited area, such as the skin around an injection site Sepsis – indicates bacterial contamination Asepsis – absences of significant contamination Microbial Control RATE OF MICROBIAL DEATH When bacterial populations are heated or treated with antimicrobial chemicals, they usually die at a constant rate. Example: Microbial Control FACTORS AFFECTING EFFECTIVENESS Several factors influence the effectiveness of antimicrobial treatments: 1. Microbial load 2. Environmental influences (i.e., temperature) 3. Presence of organic matter 4. Suspending medium 5. Time of exposure 6. Microbial characteristics Microbial Control ACTIONS OF MICROBIAL CONTROL AGENTS 1. ALTERATION OF MEMBRANE PERMEABILITY The susceptibility of the plasma membrane is due to its lipid and protein components. Certain chemical control agents damage the plasma membrane by altering its permeability. Microbial Control ACTIONS OF MICROBIAL CONTROL AGENTS 2. DAMAGE TO PROTEINS AND NUCLEIC ACIDS Some microbial control agents damage cellular proteins by breaking hydrogen bonds and covalent bonds. Other agents interfere with DNA and RNA and protein synthesis. PHYSICAL METHODS Microbial Control Microbial Control PHYSICAL METHOD OF MICROBIAL CONTROL When selecting methods of microbial control, one must consider what else, besides the microbes, a particular method will affect. Low Heat Filtration High Pressure Temperatures Osmotic Desiccation Radiation Pressure Microbial Control HEAT DRY HEAT STERILIZATION This is applicable for substances unaffected at a temperature of 148–260°C in the oven, at an exposure time of at least 45 minutes. This method kills spores, as well as vegetative forms of microorganisms. This method is ideal for sterilizing glassware, metalware, and anhydrous oils. Microbial Control HEAT DRY HEAT STERILIZATION The principle of sterilization involved is the oxidation of microorganisms by heat. Hot air sterilization Direct flaming – used to sterilize inoculating instruments using alcohol lamp or burner Incineration – burning materials to ashes Microbial Control HEAT MOIST HEAT STERILIZATION This is more effective than dry heat method. The principle of sterilization is the coagulation of the cell protein of the microorganism. Microbial Control HEAT MOIST HEAT STERILIZATION 1. BOILING Boiling point of water is 100°C. At this temperature, vegetative pathogens, viruses, some fungi and its spores are killed within 10 minutes. EXCEPTIONS: ✘ bacterial endospores ✘ parvovirus Microbial Control HEAT MOIST HEAT STERILIZATION 2. AUTOCLAVE (steam under pressure) Boiling point of water at a pressure of 15 psi is 121°C. At this temperature, even endospores are killed. Exposure time are 15–30 minutes. It is the most effective method of moist heat sterilization. Microbial Control HEAT MOIST HEAT STERILIZATION 3. PASTEURIZATION It uses a high temperature for a short time to neutralize the pathogens without altering the flavor of the food. HTST pasteurization – at least 72°C for 15 seconds UHT sterilization – at least 135°C for 2-5 seconds Microbial Control HEAT MOIST HEAT STERILIZATION 4. FRACTIONAL STERILIZATION METHOD Effective for vegetative forms of microorganisms and endospores without heating above 100°C a. Tyndallization It makes use of moist heat at 100°C, using free flowing steam. It is normally performed by 2 to 3 exposures, alternated with intervals at room temperature or incubator temperature. Takes a few days to finish (time-consuming and outdated). Microbial Control HEAT MOIST HEAT STERILIZATION b. Inspissation It is a fractional method of sterilization at 60°C in an oven, alternated with intervals at room temperature or incubation for 2 to 3 days. Takes a few days to finish (time-consuming and outdated). Microbial Control FILTRATION FILTRATION The passage of liquid or gas through a filter with pores enough to retain microbes. 1. HEPA FILTER Microbes can be removed from air by high-efficiency particulate air filters. 2. MEMBRANE FILTER Membrane filters composed of nitrocellulose or cellulose acetate are commonly used to filter out bacteria, viruses and even large proteins. Microbial Control LOW TEMP LOW TEMPERATURE Cold or Freezing Temperature The effectiveness of low temperatures depends on the microorganisms and the intensity of the application. Microorganisms do not reproduce at ordinary refrigerator temperatures (0–7°C) Many microbes survive (but do not grow) at the subzero temperatures used to store food. Microbial Control HIGH PRESSURE HIGH PRESSURE HIGH PRESSURE PROCESSING (HPP) It is a non-thermal food preservation technique that kills microorganisms that can cause diseases or spoil food. It uses intense pressure for a certain time and has minimal effects on taste, texture, appearance, or nutritional values. Microbial Control DESICCATION DESICCATION Complete Drying-out / Loss of Water In the absence of water, microorganisms cannot grow but can remain viable. Viruses, protozoal cysts and bacterial endospores can resist desiccation. Microbial Control OSMOTIC PRES OSMOTIC PRESSURE High Salt Concentrations Microorganisms in high concentrations of salts and sugars undergo plasmolysis. Molds and yeasts are more capable of growing in materials with low moisture or high osmotic pressure than bacteria are. Microbial Control RADIATION RADIATION Radiation has various effects on cells, depending on its wavelength, intensity, and duration. Radiation that kills microorganisms (sterilizing radiation) is of two types: Non-ionizing Ionizing Microbial Control RADIATION RADIATION 1. ULTRAVIOLET (UV) RADIATION This is used to aid reduction of air borne contamination produced by mercury vapor lamps. This method has poor penetration capability. Its effectiveness depends on: a. length of time of exposure b. intensity of radiation c. susceptibility of the microorganism Microbial Control RADIATION RADIATION 2. IONIZATION RADIATION Ionization radiation is a form of energy that acts by removing electrons from atoms and molecules of materials that include air, water, and living tissue. This radiation method makes use of high energy emitted from radioactive isotopes such as cobalt 60 (gamma rays) or by cathode or (beta rays). Microbial Control RADIATION RADIATION The principal effect of ionizing radiation is the ionization of water, which forms highly reactive free radicals. These radicals kill organisms by reacting with organic cellular components, especially DNA, and damaging them. Microbial Control RADIATION RADIATION Gamma rays are more reliable because there is no mechanical breakdown, but it has a disadvantage of rare source and cannot be shut off immediately. Beta particles are mechanical acceleration of electrons to high velocity and energy. Accelerated electrons provide higher and more uniform dose output and can destroy organisms by stopping its reproduction. Microbial Control RADIATION RADIATION It is a safe and cost-effective method for sterilizing single-use medical devices such as syringes and surgical gloves. One of its key advantages is that it allows already- packaged products to be sterilized. CHEMICAL METHODS Microbial Control Microbial Control CHEMICAL METHODS OF MICROBIAL CONTROL Chemical agents are used on living tissue (as antiseptics) and on inanimate objects (as disinfectants). Few chemical agents achieve sterility. Microbial Control PRINCIPLES OF EFFECTIVE DISINFECTION The presence of organic matter, degree of contact with microorganisms, and temperature should be considered. Microbial Control EVALUATING A DISINFECTANT There is a need to evaluate the effectiveness of disinfectants and antiseptics. The current standard is the American Official Analytical Chemist’s use-dilution test. Microbial Control EVALUATING A DISINFECTANT In the use-dilution test, bacterial (S. choleraesuis, S. aureus, and P. aeruginosa) survival in the manufacturer’s recommended dilution of a disinfectant is determined. In the filter paper method, a disk of filter paper is soaked with a chemical and placed on an inoculated agar plate; a clear zone of inhibition indicates effectiveness. Microbial Control TYPES OF DISINFECTANTS 1. PHENOL AND PHENOLICS Phenolics exert their action by injuring plasma membranes, inactivating enzymes, and denaturing proteins. Common phenolics are cresols and hexachlorophene. Microbial Control TYPES OF DISINFECTANTS 2. CHLORHEXIDINE Chlorhexidine damages plasma membranes of vegetative cells. Microbial Control TYPES OF DISINFECTANTS 3. HALOGENS Some halogens (iodine and chlorine) are used alone or as components of inorganic or organic solutions. Iodine is available as a tincture (in solution with alcohol) or as an iodophor (combined with an organic molecule). Microbial Control TYPES OF DISINFECTANTS The germicidal action of chlorine is based on the formation of hypochlorous acid when chlorine is added to water. Chlorine is used as a disinfectant in gaseous form (CI2) or in the form of a compound, such as calcium hypochlorite, sodium hypochlorite, and chloramines. Microbial Control TYPES OF DISINFECTANTS 4. ALCOHOLS Alcohols exert their action by denaturing proteins and dissolving lipids. In tinctures, they enhance the effectiveness of other antimicrobial chemicals. Aqueous ethanol (60% to 90%) and isopropanol are used as disinfectants. Microbial Control TYPES OF DISINFECTANTS 5. HEAVY METALS AND THEIR COMPOUNDS Silver, mercury, copper, and zinc are used as germicidals. They exert their antimicrobial action through oligodynamic action. Microbial Control TYPES OF DISINFECTANTS 6. SURFACE-ACTIVE AGENTS Surface-active agents decrease the tension between molecules that lie on the surface of a liquid; soaps and detergents are examples. Soaps have limited germicidal action but assist in the removal of microorganisms through scrubbing. Acid-anionic detergents are used to clean dairy equipment. Microbial Control TYPES OF DISINFECTANTS 7. QUATERNARY AMMONIUM COMPOUNDS Quats are cationic detergents attached to NH4+. By disrupting plasma membranes, they allow cytoplasmic constituents to leak out of the cell. They are most effective against gram-positive bacteria. benzalkonium chloride cetylpyridinium chloride Microbial Control TYPES OF DISINFECTANTS 8. ORGANIC ACIDS AND DERIVATIVES Sorbic acid, benzoic acid, and propionic acid inhibit fungal metabolism. They are used as food preservatives. Microbial Control TYPES OF DISINFECTANTS 9. ALDEHYDES Aldehydes such as formaldehyde and glutaraldehyde exert their antimicrobial effect by inactivating proteins. They are among the most effective chemical disinfectants. Microbial Control TYPES OF DISINFECTANTS 10. GASEOUS CHEMOSTERILIZERS Ethylene oxide is the gas most frequently used for sterilization. It penetrates most materials and kills all microorganisms by protein denaturation. Microbial Control TYPES OF DISINFECTANTS 11. OXIDIZING AGENTS Ozone and peroxide are used as antimicrobial agents. They exert their effect by oxidizing molecules inside cells. THANK YOU FOR LISTENING! PHMP211 Lecture