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Microbiology Exam Study Guide

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1. Approaches to Control Microbes a. Physical Methods i. Dry 1. incineration or dry oven  sterilization ii. Moist heat 1. Boiling water, steam under pressure  sterilization 2. Kills micr ... obes by denaturing enzymes 3. Ex. Autoclaving iii. Radiation 1. Irradiation – bombardment with radiation 2. Ionizing – can penetrate a solid barrier, bombard a cell, enter it, and dislodge electrons form molecules a. x-ray, cathode, gamma  sterilization 3. Nonionizing – enters a cell, strike molecules, and excites them. Results? Mutation of DNA a. Note: non-ionizing radiation cannot penetrate a solid barrier b. UV  disinfection iv. Chemical Methods 1. Antimicrobial chemicals  disinfection or sterilization 2. Gases  disinfection of sterilization v. Mechanical Methods 1. Filtration of air and liquids  decontamination 2. Physical Controls a. Heat i. Moist heat – boiling water (100oC, 30 min) ii. Pasteurization – milk, fruit juices; flash method (~72oC, 15 sec) iii. Pressurized steam – autoclave (121oC, 15psi); used for surgical instruments, commercial canning (clostridium botulinum, problem in canning) b. Radiation i. Gamma radiation – DNA 1. Medical equipment, drugs, food-safe ii. Ultraviolet radiation – DNA iii. Microwave – heat 3. Factors in Treatment a. Situation – home, hospital, lab, factory i. Sepsis – the growth of microorganisms in the blood & other tissue b. Surface or medium c. Type and number of microorganisms i. Highest resistance = endospores ii. Moderate resistance = mycobacterium, S. aureus iii. Least resistance = non-endospore formers d. Environment e. Concentration of agent being used f. Mode of action 4. Mechanical Controls a. 2 kinds i. Fluid filtration ii. Air filtration – HEPA; hospitals b. Decontaminating Congress – letters containing Bacillus anthracis were opened in Hart Office of US Senate in 2001 i. B. anthracis is spore-forming – eradication is tough; building was heavily populated, needed to decontaminate heating/AC vents, carpet, furniture, office equipment, sensitive papers, artwork, personal belongings c. Decontamination Process i. Size/scope – samples taken from 25 buildings ii. Decontamination – vacuum with HEPA filter followed by tx with liquid chlorine dioxide (sterilant used for treatment of medical waste) or a decontamination foam; heavily contaminated areas used gaseous ClO2 5. Chemical Controls a. Factors for choosing appropriate germicide: storage/stability, residue, cost/availability, environmental risk b. Germicidal Chemical: i. Alcohols, hydrogen peroxide (H2O2), ethylene oxide (used on medical instruments, plastics; sugar, spices) 6. –static? or –cidal? a. Bactericide – a chemical that destroys bacteria except for those in the endospore stage b. Germicide/Microbicide – chemical agents that kill microorganisms c. Bacteristatic – prevent the growth of bacteria on tissues or on objects in the environment d. Fungistatic – inhibit fungal growth e. Microbistatic – antiseptics & drugs (used in the body) f. Degermination – reducing the number of microbes on the skin (ex. hand sanitizers) [Show More]

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