Chapter 9

• Antisepsis: the use of antibacterial agents to prevent or kill microorganisms
• Aseptic: free from microorganisms, sterile, or free from contamination
• Degerming: Removal of microbes by mechanical means
• Disinfection: the killing of microorganisms on a surface or in a liquid
• Pasteurization: heating food to kill bacteria and pathogens
• Sanitation: Removal of pathogens from objects to meet public health standards
• Sterilization: Destruction of all microorganisms and viruses in or on an object
• -cide, -cidal: Destruction of a type of microbe
• -stasis, -static: Indication inhibition but not complete destruction of a type of microbe
• Microbial death: Lost of ability to reproduce
• Thermal death point: Lowest temp to kill all cells in 10 mins
• Thermal death time: Time to sterilize volume of liquid at set temp
• Decimal reduction time: the time it takes to reduce a microbial population by 1 logarithm, or 90% of its initial value, under specified conditions
• Physical antimicrobial agents that can kill microbes are: Damage cytoplasmic membrane, denature proteins, and disrupt structure and function of nucleic acids
• Ideally agents should be: Inexpensive, fast-acting, stable during storage and harmful to microbes and not to us
• Factors Affecting Efficacy of Antimicrobial methods: Site be treated, Relative susceptibility of organisms and environmental conditions
• Biosafety level 1: no special precautions required, no special equipment needed
• Biosafety Level 2: some pathogens may cause serious disease, standard lab practices with some additional precautions
• Biosafety Level 3: high potential risk of infection, specialized containment facilities and procedures
• Biosafety Level 4: extreme hazards, maximum physical containment
• moist heat works better than dry heat for killing bacteria because it is more effective at penetrating the cell wall
• Boiling: Kills vegetative cells, but not spores.
• Autoclaving: A method of sterilization in which the object to be sterilized is placed in a pressure vessel and subjected to a high pressure
• Pasteurization: Used for dairy and fruit juices. Heat tolerant microbes survive
• Hot air: Denatures proteins, destroys membranes, oxidizes compounds
• Incineration: Oxidizes everything completely
• Freezing: Inhibits metabolism, usually used for long-term preservation of things
• Desiccation: inhibits by drying out
• Lyophilization: Freeze and drying process that removes water from a sample. Long-term storage of bacterial cultures
• Filtration: Physically separates microbes from air and liquids.
• Osmotic Pressure: High concentrations of salt/sugar to inhibit growth
• Ionizing Radiation: Destroys DNA. Ex. Electron beams, gamma rays, & X rays
• Nonionizing radiation: Formation of thymine dimmers in it is DNA transcription and replication.
• Chemical methods of Microbial Control: Same has physical methods but tends to be more effective against enveloped viruses
• Phenols: Denatures proteins, used to be original surgical antiseptic
• Alcohols: Denatures proteins, used as disinfectants
• Halogens: Denatures proteins, used in disinfectants and water purification
• Oxidizing agents: Denatures proteins by oxidation, used as peroxides
• Surfactants: Decrease surface tension of water and disrupt cell membranes. Ex. soaps
• Heavy metals: Denature proteins