Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Infection control L. Dalia Kamal Eldien MSc in Microbiology Lecture NO: 13 Introduction Infectious diseases can be the result of the colonization of the body by various microbes. There are many similar disease states that can arise from different causes, i.e. pneumonia can be caused by viruses, or bacteria, or protozoa, and even fungi. Scientists' reasoned that if microorganisms cause disease, then it was possible to control disease by controlling the microorganisms. Infection control To control the growth of microorganisms and their transmission of infectious disease involve: Stopping the growth of the microorganism for a period of time Reducing the number of microorganisms to a safe level Destroying the microorganisms Methods controlling the microorganisms For instruments, equipment, and fluids use method known as Sterilization and Disinfection Sterilization Sterilization is defined as a freeing an object from all kinds of living microorganisms including spores. Methods of sterilization, can broadly be grouped in two 1- Physical method 2- Chemical method (Disinfection) Physical method Physical method of sterilization include: A. Heat B. Filtration C. Radiation Heat The most common method used for the elimination of microorganisms, sterilization by heat Sterilization by heat are two types:o Dry heat o Moist heat Dry heat Dry heat kills by microbes by oxidation, applied mainly in two ways:1- Direct incineration / red heat / flaming 2- Hot air oven: All the glassware (except those with rubber linings) are sterilized in oven at 180°C for 20 minutes or I60 for 90 minutes Flaming sterilization Red heat sterilization Moist heat Are more effective than dry heat. kills the organisms by denaturing enzymes and structural proteins of microorganisms Moist heat is applied in following ways: 1- Heating below 100ºC: Pasteurization, have two types: Hold method 62.5ºC for 30 minutes Flash method 72ºC for 15 seconds Moist heat 2- Boiling at 100◦C does not ensure sterility. o Boiling at 100◦C for 10 minutes is usually enough to achieve sterility for organisms are not present in high concentrations; in fact most bacteria are killed at about 70◦C. 3- Temperature above l00◦C, using instrument name as Autoclave, using heat under pressure, it is the most reliable method Pasteurization Boiling Autoclave B. Filtration Filtration is the passage of a liquid or gas through a filter with pores small enough to remain microbes. Microbes can be removed from air by high -efficiency particulate air filters. High efficiency particulate air (HEPA) filters create clean atmospheres in areas such as operating theatres and laboratory laminar-flow hoods. For fluids filtration use for products that are damaged by heat e.g. serum, toxins, antibiotics& vitamins Filtration Membrane filters composed of nitrocellulose or cellulose acetate are commonly used to filter out bacteria, viruses, and even large proteins. Size range from 0.22 μm – 0.45 μm for bacteria . Sizes can go as low as 0.01 μm to filter viruses and proteins. Sterilization by filtration C. Radiation The effects of radiation depend on its wavelength, intensity and duration, to destroys DNA Radiation may be used in two forms—ionizing and nonionizing. 1- Ionizing radiation (gamma rays, electron beams) o Is of short wavelength and high energy. o Has a high degree of penetration o Is used by the medical field for the sterilization of disposable supplies such as syringes, catheters, and gloves Radiation 2- Nonionizing o Radiation in the form of ultraviolet rays o Is of long wavelength and low energy. o Because of its poor penetrability, the usefulness of nonionizing radiation is limited; it can be used to disinfect surfaces. Radiation Chemical method (Disinfection) Terms as disinfectants and antiseptics Different chemical substances used inanimate and animate objects Only few of them have effect on spores. It is less effective than sterilization for disinfecting Antiseptic vs. disinfectant Antiseptic – An agent used to inhibit or eliminate microbes on skin or other living tissue (alcohol, iodine, chlorhexidine) Disinfectant – An agent used to destroy microbes on inanimate objects (phenols, formaldehyde, chlorine bleach) Factors That Influence the Degree of Killing The following factors play a significant role in the selection and implementation of the appropriate method of disinfection: Types of organisms Number of organisms Concentration of disinfecting agent Presence of organic material (e.g., serum, blood) Nature of surface to be disinfected Contact time Temperature pH Types A. Alcohol groups :o o o o o The two most effective alcohols used in hospitals for disinfection purposes are ethyl alcohol and isopropyl alcohol. Ethanol or Isopropanol, are sometimes used as a disinfectant, but more often as an antiseptic These alcohols are non-corrosive but can be a fire hazard. They also have limited residual activity due to evaporation, which results in brief contact times unless the surface is submerged. They also have a limited activity in the presence of organic material. Types B. 2-5 % Phenolic groups:o Are Oxidizing agents act by oxidizing the cell membrane of microorganisms, which results in a loss of structure and leads to cell lysis and death. C. Chlorine and Chlorine Compounds o Chlorine and chlorine compounds are some of the oldest and most commonly used disinfectants. o They are usually used in the form of hypochlorite, such as the liquid sodium hypochlorite (household bleach) and solid calcium hypochlorite. o Their killing activity is based on the oxidative effects Types D. Aldehydes groups:- e.g. Formaldehyde disinfecting rooms, stores, furniture, clothing& biosafety cabinet E. Glutaraldehyde:- rapid killing action and remains active in the presence of organic matter. is extremely susceptible to pH changes because it is active only in an alkaline environment F. Ethylene oxide:- a gaseous disinfectant is of particular value in sterilizing heat sensitive materials such as plastics, rubber articles G. Quaternary ammonium compounds (quats) H. Halogens Common example of home disinfectant Sources Textbook of Diagnostic Microbiology-Fifth editionConnie R. Mahon, MS- Donald C. Lehman, EdD, MT(ASCP), SM(NRM) - George Manuselis, MA, MT(ASCP)- Elsevier (2015) (Part I –chapter 4) This is the last lecture in basic microbiology, I wish all of you luck and success