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 MicroorganismsPhysical Chemical Agents Caveat Terminology Terminology 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 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 General Resistance 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 Duration of exposure Temperature Local environment pH organic matter Control Agents 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 The application of heat high temperatures is a very efficient way to kill most microbes What temperature do you need 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 types Temperatures 60 C 140 F are generally required to efficiently destroy microorganisms Heat Moist Heat Autoclaving Moist heat above 100 C Pressurized steam Needed for efficient killing of bacterial endospores Autoclave Uses Sterilizing Surgical medical instruments Growth media reagents Biohazardous waste Pasteurization Heat treatment of food products to reduce microbial levels Problem food quality altered by heat Generally use 60 75 C for 30 minutes Measuring Effectiveness of Heat Thermal Death Time TDT Shortest time needed to kill all microorganisms at a specific temperature Mechanical Processes Hand Washing Pathogens not as tightly attached as normal commensal bacteria Mechanical removal 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 keeps microbes off hands after scrub Food surfaces hospital surfaces general cleaning disinfection skin antisepsis Chemical Agents Quaternary Ammonium Compounds One of the most common disinfectants used A cationic detergent Uses Quaternary Ammonium Compounds Advantages Stable low toxicity and irritation Good action in presence of organics Good spectrum 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
View Full Document
Unlocking...