CHAPTER 5: CONTROL OF MICROBIAL GROWTHAPPOACHES TO CONTROL- Physical methods: heat treatment, irradiation, filtration, and mechanical removal - Chemical methods: antimicrobial agents- Principles of Controlo Sterilization: the process of removing all microorganisms and virsuse in a product Filtration, heat, chemicals, irradiation A sterile item is free from microbes , including endospores and viruses- Does not consider prionso Disinfection: eliminates most/ all pathogens on/in a material Some viable microbes exist Disinfectants: chemicals that disinfect animate objects - Biocides: things that kill life- Germicides: disinfectants that target bacteria. fungi, endospores &viruses - Bactericidal: meaning they kill bacteria  Antiseptics: used to kill bacteria on the skino Pasteurization Uses brief heating to reduce the number of spoilage organisms and kill pathogens o Decontamination Treatment used to kill the number of pathogens considered safe to handle Washing, heat, disinfectantso Degerming Decrease number of microbes on skino Sanitized Implies a substantially reduced number of growth that meets health standardso Preservation Delaying spoilage of foods by adding growth inhibiting agents- Situational Considerationso Daily Life Routine washing and scrubbing with soaps and detergents aid in the mechanical removal of organismso Hospitals Nosocomial: hospital-acquired infection  High concentrations of disease, people with invasive procedures and weak immune systems o Microbiology Labs Aseptic technique: the use of specific methods to exclude contaminating microbes fro man environmento Food and Production Facilities Add chemicals to impede or stop microbial growth o Water Treatment  Disinfection by-products: by products of adding chemicals as distinfecting agents that react with naturally occurring items that can cause long term disease - Type of Mircoorganismo Critical for selecting a microbial agento Bacterial endospores Most resistant form Killed by heat or chemical methods Take a much larger time span to killo Protozoan cysts and oocysts Stages in the life cycle of certain intestinal protozoan pathogens  Disinfectant resistant, they are excreted in feces and a concern in water treatment Readily destroyed by boilingo Myobacterium species Eaxy cell walls make them resistant to typical microbial agents Stronger, more toxic disinfectants muct be used o Pseudomonas Common environmental organisms that are resistant to chemical disinfectants and in some case seven grow in them Particular concern in hospitalso Naked viruses Lake a lipid envelope and therefore are resistant  Enveloped viruses are more sensitive to heat and chemicals - Numbers of Microorganisms initially present o Time it takes to kill is indicated by the initial populationo Decimal reduction time (D valve): time required to kill 90% of a population of bacteria under specific conditions  The temp is indictated by the subscript - Environmental Conditions o pH, temperature, fats and other organic material and their prescenceo certain products, like dirt, grease, etc can impact the degree to which a antimicrobial works- Potential Risk of Infectiono Critical instruments These come into contact with the body tissues o Semicritical Instruments Do not penetrate body but come into contact with mucous membranes Mucous membranes pose as a great barrier to microbes like endosporeso Noncritical instruments Pose little infection risk Ex: countertops and stethoscopes- Composition of the Item o Many items can be heat sensitive (like plastics)- Moist Heato Moist heat destroys microorganisms by irreversibly coagulating their proteinso Boiling Not an effective mean of sterilization because endospores can stand temperatures higher than 100 Centigradeo Pasteurization Does not sterlize, but reduces the number of microbes in a substance, most often food products Kills pathogens without altering food and can increase shelf life High-temperature-short-time, utilized by pasteurization protocol, raises foods at various high temperatures (below boiling pt) for brief periods of time- Ex: milk is 72 degrees every 15 seconds Ultra-high-temperature method: renders the product free of any microbes that can grow at room temperature- Rapidly heated to high temperatures and then cooledo Sterilization using pressurized steam Autoclave: heats water, in an enclosed vessel that achieves temperatures higher than 100 degrees Centigrade As the heated water in the vessel forms steam, the steam causes the pressure in the vessel to increase above atm pressure The higher the pressure, the higher the temperature that the steam forms Used to terminated heat and moisture tolerant items Flash autoclaving: by increasing the temperature, things can be sterilized at a faster rate In order to be effective, most monitor pressure, and allow the steam to penetrate items and displace air Autoclaving tape: heat sensitive tape that turns color in the presence of high temperatures  In order to ensure autoclaving, endospores are also heated and the mixture is then put on a plate to detect growth o The commercial canning process Retort: an industrialized autoclave that utilizes steam  Designed to destroy Clostridium- These cells can germinate and grow in the anaerobic environment of the can Commercially sterile: endospores of thermopilic bacteria by be present, but can only grow at extremely high temperatures and therefore are no considered dangerous Higher the temp, the shorter time to sterilize Higher the population, the longer the time to sterilize o Dry Heat  Requires longer time and higher temperatures than wet heat in order to be effective Incineration oxidizes the cell components to ashes Flaming: heating until a red hot flame appears (inoculating loop) Hot air ovens: oxidize all cell components and irreversibly denature proteins - If have fans: can circulate heat more effectively and sterilize in a shorter timeUSING OTHER PHYSICAL METHODS TO REMOVE OR DESTROY MICROBES- For materials that are heat-sensitive, other methods must be utilized in order to create effective sterilization- Filtrationo Filtration of Fluids  Used to sterilize sensitive fluids (beer) Paper thin membrane filters have microscopic pores that allow fluid to flow through, but particles like bacteria cannot  Pressure or a vacuum in