Control of Microbial Growth (Sterilization and Disinfection)

Control of Microbial Growth www.petersoulsby.org www.thisoldhouse.com speedysysteminc.com askville.amazon.com www.sdada.org

Microbial Control Can inhibit growth of many microorganisms by washing and scrubbing with soaps and detergents. www.enviroblog.org

Sterilization Process of removing or killing all microorganisms and viruses on or in a product. Ensures complete destruction of all microorganisms, including cells, spores, and viruses. www.kendall-ltp.com www.medicalcareerinstitute.net

Examples of Sterilization Dry heat Autoclaving Gas Various chemicals Certain types of radiation Autoclave. www.lifelinemedical.net Dry Heat Sterilization. www.kabdental.com

Disinfection Process that reduces # of potential disease-causing bacteria and viruses on a material until they no longer present a hazard. Terms decontamination and sanitation mean the same thing generally. Disinfectant A chemical used to disinfect inanimate objects.

Example of Disinfection - Pasteurization Method of disinfecting liquids. Heat liquids to a certain temperature. Does not totally destroy pathogens. Pasteurization Equipment. www.foodprocessing-technology.com

Decontamination Inactivation or removal of both microbial toxins and the living microbial pathogens. www.foxnews.com

Antiseptic Solutions used to disinfect skin and other living tissues. www.firstaid-direct.co.uk

Sanitation Reduction of microbial populations to levels considered safe by public health standards. www.zerrenterprises.com

Microbicidal Agents The suffix –cide or –cidal refers to “killing.” Ex. Microbicidal agents (microbicides) Ex. Bactericidal agents Ex. Sporicidal agents Ex. Viricidal agents

Microbistatic Agents Microbistatic Agent Bacteriostatic Agent Drug or chemical that inhibits the growth and reproduction of microorganisms. Bacteriostatic Agent One that specifically inhibits the metabolism and reproduction of bacteria. Microbistatic technique examples Ex. Lyophilization (freeze-drying) Ex. Rapid freezing (using liquid nitrogen)

Some Useful Terms Sepsis Asepsis Antisepsis Antiseptic technique Presence of pathogens in blood or tissues. Asepsis Absence of pathogens. Ex. Hand washing; use of sterile gloves, masks, gowns; sterilization of surgical equipment; use of disinfectants. Antisepsis Prevention of infection. Antiseptic technique Developed by Joseph Lister (1867). Use of antiseptics. mateengreenway.com

Sterile Technique Practice of excluding all microorganisms from a particular area, so that the area will be sterile. bioweb.wku.edu

Controlling Microbial Growth Using Physical Methods Methods used to destroy or inhibit microbial growth may be physical or chemical. Examples: Heat Combination of heat and pressure Desiccation Radiation Sonic disruption Filtration

Heat Practical, efficient, and inexpensive method of sterilization. 2 factors that influence effectiveness of heat for sterilization: temperature and time Thermal Death Point (TDP) Lowest temperature that will kill all organisms in a standardized pure culture within a specified period. Thermal Death Time (TDT) Length of time necessary to sterilize a pure culture at a specified temperature.

Dry Heat Heating materials in absence of moisture. Must be baked at 160º to 165ºC for 2 hours or at 170º to 180ºC for 1 hour. Other methods include incineration and flaming surface of metal materials like forceps and loops. biology.clc.uc.edu

Moist Heat Boiling or steaming. Most pathogens destroyed after 30 minutes of boiling. Boiling not always effective against some endospores and viruses. Boiling not an option for thermophiles. Boiling. ttt.astro.su.se Steamer. www.appliancist.com

Autoclaving Large metal pressure cooker that uses steam under pressure to completely destroy all microorganisms. Increased pressure raises the temperature of boiling water (i.e. above 100ºC) producing steam. www.uwm.edu

Home Canning Use of a pressure cooker. If foods canned without pressure some bacterial endospores may survive. i.e. Clostridium botulinum www.thecookwarebarn.com Bulging lid – botulism. calorielab.com

Disinfecting Techniques For clothing, bedding, and dishes Use hot water with soap or detergent Agitate solution around items Combination of heat, mechanical action, and chemical inhibition kills most microbes. Washing Machine. www.genexe.com

Cold Metabolic activities slowed. Most microbes not killed, but growth inhibited. Slow freezing not a good way to preserve bacteriological or biologic specimen. Rapid freezing (liquid nitrogen) good for this. Why should you not refreeze foods? www.themodernapprentice.com Slow Freezing. Rapid Freezing – liquid nitrogen. encarta.msn.com

Desiccation Process of drying materials. Many microbes can remain viable despite absence of nutrients and moisture. Ex. Lyophilization (freeze-drying) Dried blood, fecal material, and dust may still contain viable microbes. www.mahalo.com

Radiation Ultraviolet (UV) light sometimes used to prevent or decrease microbial growth. X-rays and gamma and beta rays may be used to destroy or prevent microbial growth. www.moondragon.org www.fda.gov

Ultrasonic Waves Often used to sterilize and clean delicate equipment. Consists of tanks filled with liquid solvent (usually water). Short sound waves are passed through liquid. Sound waves dislodge organic debris. Materials must then be washed and sterilized by another method.

Filtration Filters of various pore sizes are used to filter or separate larger cells, larger viruses, bacteria, and other microbes from gases or liquids in which they are suspended. Paper masks used to prevent the outward and inward movement of microbes. wps.prenhall.com health.howstuffworks.com

Gaseous Atmosphere Altering atmosphere of microbes to inhibit growth. Gas gangrene – caused by Clostridium spp. www.humanillnesses.com Hyperbaric Chamber. www.perlhealth.com

Chemical Agents Used to Inhibit Microbial Growth Temporarily or permanently. Different disinfectants have different properties. Disinfectants should be chosen based on their efficiency and effectiveness for a particular situation.

What Are Some Things to Consider When Choosing a Chemical Disinfectant?

What makes an Ideal Chemical Antimicrobial Agent?

How Do Disinfectants Kill Microorganisms? Some target and destroy cell membranes. Ex. Surface-active soaps and detergents; alcohols Some destroy enzymes and structural proteins. Ex. Formaldehyde and ethylene oxide Some attack cell walls or nucleic acids.

Antiseptics Can be used safely on human skin. Reduces # of organisms on the surface. Does not penetrate pores or hair follicles. www.superstock.com

Preventing Growth of Pathogens in Our Kitchens www.homesteadwoodworks.ca

The Antibiotic Controversy www.smh.com.au www.ferret.com.au

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