MLAB 2434 – CLINICAL MICROBIOLOGY SUMMER, 2005 CECILE SANDERS & KERI BROPHY Chapter 2 – Control of Microorganisms

Chapter 2 – Control of Microorganisms (cont’d) Sterilization vs. Disinfectant Sterilization Removes all forms of life, including spores “All or nothing” process Chemical or physical

Chapter 2 – Control of Microorganisms (cont’d) Disinfection Removes all pathogenic organisms but not necessarily all spores “Disinfectants” are chemicals applied to inanimate objects “Antiseptics” are disinfectants applied to living tissue

Chapter 2 – Control of Microorganisms (cont’d) Factors Influencing Degree of Killing Types of organisms - Bacterial spores, mycobacteria, nonlipid viruses, fungi, bacteria, lipid viruses (most resistant to least resistant) Number of organism – microbial load Concentration of disinfecting agent

Chapter 2 – Control of Microorganisms (cont’d) Organic soil present Nature of surface to be disinfected Methods of Disinfection & Sterilization Physical Methods Heat – autoclave = 15 psi at 121° C for 15 minutes (Boiling and pasteurization disinfect but do not sterilize)

Chapter 2 – Control of Microorganisms (cont’d) Filtration Radiation Chemical Methods Alcohols – ethyl and isopropyl at % concentration Aldehydes (formaldehyde, glutaraldehyde) Halogens Iodine (Tincture and Iodophore) Chlorine and chlorine compounds

Chapter 2 – Control of Microorganisms (cont’d) Heavy metals – rarely used; example = silver nitrate in newborns’ eyes Detergents – surfactants; limited to non-critical areas like bench tops and floors Phenolics – disinfection of hospital environments Gases – ethylene oxide

Chapter 2 – Control of Microorganisms (cont’d) Microbiology Laboratory Safety Program Address biological hazards Describe safe handling, storage and disposal Procedures in event of fire, natural disasters, and bomb threats Correct techniques for lifting and moving heavy objects

Chapter 2 – Control of Microorganisms (cont’d) Handling Biological Hazards Two sources of hazards: Patient specimens Actively growing cultures of microorganisms

Chapter 2 – Control of Microorganisms (cont’d) “Levels of Protection” Level 0 = handling materials and performing tasks that do not involve contact with or exposure to blood, body fluids, body secretions, or tissues (e.g., reading routine culture plates at bench); requires buttoned lab coat Level 1 = specimen receiving; requires gloves and buttoned lab coat

Chapter 2 – Control of Microorganisms (cont’d) Level 2 = processing and planting specimens for culture and direct examination on slides or performing any activity that can generate aerosols; requires gloves, buttoned lab coat, and Class II safety cabinet (or mask and eye cover if cabinet is not available)

Chapter 2 – Control of Microorganisms (cont’d) Safety Cabinets (Hoods) – see page 39 in text) Class I – exhaust fan moves the air inward through the open front. Air uncirculated and passes through HEPA filter. Example = chemical fume hood Class II – air pulled inward and downward and then passes through HEPA filter before reaching work surface. Example = most common microbiology laboratory hood

Chapter 2 – Control of Microorganisms (cont’d) Class III Self-contained, ventilated system for highly infectious microorganisms Provides highest level of personal protection Closed front contains attached gloves for work on bench