CONTROLLING MICROBIAL GROWTH It is often necessary to control the growth of certain microorganisms, particularly those that grow on fomites, which are inanimate objects that can harbor organisms. Some organisms will be resistant to antimicrobial treatments, such as Clostridium botulinum, which survives canning procedures. There are four biological safety levels as outlined by the CDC. They depend on the infectivity of the organism, the ease at which it is transmitted, the disease severity possible, and the type of work being performed by the organism. A BSL-1 organism does not cause disease in the healthy host and there is little risk in working with them. A BSL-2 organism can cause a moderate disease in workers but are indigenous to the area. Personal protective equipment is required. BSL-3 agents can be lethal and some are considered exotic to the area. These include things like the organism that causes HIV and tuberculosis. BSL-4 organisms are very dangerous and usually fatal with no available treatments, such as smallpox and Ebola. Sterilization will kill cells, viruses, and endospores. Heat, filtration, pressure, or chemicals can kill these microbes. Aseptic technique is required to prevent contamination of surfaces that are considered sterile. Maintaining a sterile field in surgery helps to prevent sepsis in the surgical patient. Foods can be sterilized in commercial sterilization, such as those that get rid of botulism. Disinfection gets rid of most organisms on a fomite surface using chemicals or heat. It does not create sterility but is usually fast and inexpensive to do. Chlorine bleach is an example of a disinfectant. Antiseptics are those antimicrobials that are safe for human tissues. Degerming involves handwashing in order to physically get most of the organisms off the hands. Sanitation will clean fomites in order to prevent disease transmission. It involves things like cleaning bathrooms and using a dishwasher. There are physical and chemical methods of getting rid of microorganisms. Some methods are bactericidal or viricidal because they will kill the organism. Fungicides will kill fungi. Things that are fungistatic or bacteriostatic do not kill the organism but stops the growth of the organism. Bacteriostatic agents in plastics, for example, will inhibit
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