MCB2010 Exam 2 2025

Order the following from most to least resistant in the environment: Gram positive Gram negative Endospores - -endospores Gram negative Gram positive Sterilization - -destruction or removal of all viable organisms from an object or from a particular environment disinfection - -killing, inhibition, or removal of pathogenic microorganisms (usually on inanimate objects) antisepsis - -prevention of infection of living tissue by microorganisms sanitization - -reduction of the microbial population to a safe level as determined by public health standards What is the difference between a bactericidal and a bacteriostatic agent? - -cidal - kills static - inhibits Differentiate between physical and chemical modes of controlling microorganisms. - Physical Heat Low temperatures Filtration Radiation Chemical High-level germicides Intermediate-level disinfectants and antiseptics Low-level disinfectants Comparing dry and moist heat, which is faster and penetrates better? - -moist What is the chamber that uses steam under pressure? What are its main uses? - autoclave; kill bacteria, spores and germs resistant to boiling water and powerful detergents i.e. lab equipment, tattooing, hospitals What is the function of pasteurization? Give examples for use. - -doesn't denatures proteins kills bacteria Used for milk, ice cream, yogurt, and fruit juices MCB2010 MCB2010 What is the function of cooling? - -Decrease microbial metabolism, growth, and reproduction Chemical reactions are slower at low temperatures Refrigeration halts growth of most pathogens Are there organisms that can withstand very low temperatures? - -Some microbes can multiply in refrigerated foods What is meant by desiccation? Can some organisms withstand it? - -Desiccation (drying) inhibits growth due to removal of water yes What are some uses for ionizing radiation? - -Ejects electrons from atoms to create ions Ions disrupt hydrogen bonding, oxidize double covalent bonds, and create hydroxyl radicals Ions denature other molecules (DNA) What are some uses for UV light? - -Excites electrons, causing them to make new covalent bonds Affects 3-D structure of proteins and nucleic acids Suitable for disinfecting air, transparent fluids, and surfaces of objects Lyophilization - -(freeze-drying) used for long-term preservation of microbial cultures Prevents formation of damaging ice crystals Why are Bacillus endospores used as sterility indicators? - -The endospore is extremely heat resistant and it is reasonable to believe that if the dry heat kills them no other organism will survive. How is filtration used to control microorganisms? - -HEPA filters have effective pore sizes of 0.3 µm, small enough to capture bacterial cells, endospores, and many viruses, as air passes through these filters, nearly sterilizing the air on the other side of the filter Chemical Methods of Microbial Control - -• Affect microbes' cell walls, cytoplasmic membranes, proteins, or DNA • Effect varies with differing environmental conditions • Often more effective against enveloped viruses and vegetative cells of bacteria, fungi, and protozoa Many chemical disinfectants and antiseptics act by denaturing proteins. Why does denaturation kill cells? - - MCB2010 MCB2010 What is the nature of betadine and what is it used for? - -an antiseptic solution that contains a complex of iodine. It was introduced in the 1960s and it is the most commonly used iodophor in modern clinical use. What is the effect of hydrogen peroxide and what are some of its uses? - -Kill by oxidation of microbial enzymes is a mild antiseptic used on the skin to prevent infection of minor cuts, scrapes, and burns. It may also be used as a mouth rinse to help remove mucus or to relieve minor mouth irritation What are aldehydes used for? - -Compounds containing terminal —CHO groups Cross-link functional groups to denature proteins and inactivate nucleic acids Glutaraldehyde disinfects and sterilizes Formalin used in embalming and disinfection of rooms and instruments What is Ethylene oxide used for? - -a type of flammable and explosive gas that is used for the sterilization of medical equipment and devices. What are the various mechanisms that are considered first line of defense? - -skin mucous membranes What are the various mechanisms that are considered second line of defense? - Composed of cells, antimicrobial chemicals, and processes but no physical barriers Phagocytic white blood cells Inflammation Antimicrobial substances What are the various mechanisms that are considered third line of defense? - -The body's ability to recognize and defend itself against distinct invaders and their products Specific Memory Self tolerance Lymphocytes Antibodies How are the host normal flora considered a first line of defense? - -Normal flora prevent other microorganisms from establishing an infection - "competitive exclusion" two species competing for the same limiting resource cannot coexist at constant population values List the various structures and secretions in the skin that make it defensive - -Sweat glands create high salt conditions and antibacterial enzymes (lysozyme). MCB2010 MCB2010 Sebaceous glands produce an oil layer; fatty acids and acidic pH makes an inhospitable environment for microorganisms. What are the main effects of the inflammatory response on the body? - -Inflammation is a localized tissue response that occurs when your tissues are damaged and in response to other stimuli. Inflammation brings more white blood cells to the site where the microbes have invaded. The inflammatory response produces swelling, redness, heat, and pain. What are the stages of inflammation, and how do these coincide with the cardinal signs of that process? - - 1. damaged tissues release histamines increasing blood flow in the area 2. histamines cause capillaries to leak, releasing phagocytes and clotting factors into the wound 3. phagocytes engulf bacteria, dead cells, and cellul