Control of Microorganisms Physical Chemical Agents Goal removing pathogens from surfaces Surgical and other hospital equipment Laboratory equipment Food and food prep surfaces Any surface with known contamination by a pathogen Skin and skin wounds Control of Microorganisms Physical Chemical Agents Caveat Getting rid of microbes just to be more clean or to have a perfectly disinfected environment is detrimental It can lead to A build up of resistance by the microbe to the agent being used limiting your immune system from building an immunity to specific microbes Obsessive cleaning behavior http www tufts edu med apua Pubs Articles EID6 01 pdf Sterilization removal killing of ALL forms of microorganism from an object Terminology Disinfection reduction in the number of microorganisms with the goal of killing or inhibiting pathogens Sanitation reduction in microbial numbers considered safe by public health agencies Usually applied to the food industry Antisepsis the killing or inhibiting of microorganisms on living tissue ex skin oral cavity General Resistance Picture Table 11 1 Bacterial Endospores Fungal spores protozoan cysts some viruses and some bacterial vegetative cells Most bacterial vegetative cells and fungi Most protozoa Factors Influencing Control Population Type composition What kind of microbe is present Population Size How many microbes present Concentration Intensity of Agent 70 alcohols have the best killing effect Duration of exposure Temperature environment How long are you exposing to chemical agents Local environment pH organic matter bleach hallogens Control Agents NEED TO KNOW FOR EXAM Physical Agents Heat Ionizing and non ionizing radiation Mechanical Removal Abrasion Scrubbing Filtration Chemical Agents many Quaternary Ammonium compounds Ethylene oxide Halogens Phenolics Alcohols Control Agents Picture Figure 11 1 Heat The application of heat high temperatures is a very efficient way to kill most microbes What temperature do you need denatures protein breakdowns membrane most microbes survive at temperatures BELOW 40 C 104 F Temperatures of 40 60 C inhibit the growth of many microbes and may even destroy some Temperatures 60 C 140 C are generally required to efficiently destroy types microorganisms Moist Heat Picture Autoclaving Picture uses moist heat to get temps above 100 C Pressurized steam Needed for efficient killing of bacterial endospores Autoclave Uses Sterilizing Surgical medical instruments Growth media reagents Biohazardous waste Pasteurization disinfection sanitation Heat treatment of food products to reduce microbial levels Problem food quality altered by heat ex heating milk Generally use 60 75 C for 30 minutes Ultra Pasteurization uses on food other products slightly higher temps and shorter times Measuring Effectiveness of Heat Thermal Death Time TDT Shortest time needed to kill ALL microorganisms at a specific temperature Decimal Reduction Time D Value Picture Time required to kill 90 of microorganisms at a specific temperature a tenfold reduction or one log value Hand Washing Pathogens not as tightly attached as normal commensal bacteria Mechanical removal Mechanical Processes Water and scrubbing only Yes it does remove microbes Water and soap better Water and antibacterial soaps products probably same as water and soap although may have some residual effect killing effect which continues to kill microbes after scrub Chemical Agents Quaternary Ammonium Compounds Quats One of the most common disinfectants used A cationic detergent Uses Food surfaces hospital surfaces general cleaning disinfection skin antisepsis Quaternary Ammonium Compounds Advantages Stable low toxicity and irritation Good action in presence of organics breakup damage material Good spectrum how well these chemicals work Disadvantages inactivated by hard water Limited action on Mycobacterium and Pseudomonas Evaluating Effectiveness Phenol Coefficient Compares activity of phenol to other agents Coefficient 1 0 not as effective as phenol 1 0 same 1 0 better than phenol End Go to Microbial Metabolism
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