1)What are the four general considerations for effective microbial control? List and describe (8 pts)

Transcription

1 ä.2 Name: Sanitation work sheet Answer Key Not to be turned in... 1)What are the four general considerations for effective microbial control? List and describe (8 pts) 1) Sterilization: complete removal or destruction of all viable microbes. Used on inanimate objects 2) Disinfection: use of physical process or chemical agent to destroy vegetative microbes - not endospores 3) Antisepsis - chemical applied to the body surfaces to destroy or inhibit vegetative microbes 4) Sanitation/degermation - chemical and physical methods that reduce the microbial load on a surface. 2) Does de-germing of skin involve sterilization or sanitation processes and why? (4 pts) De-germing the skin involves a sanitation process and not sterilization. Sterilize the skin would involve destroying the skin to kill all bacteria hiding in the hair follicles of the skin. 3) Describe the five factors that affect microbial death rates? (10 pts) 1) The number of organisms: the higher the load of contaminants requires more time to destroy the microbes. 2) The nature of the microorganism in the population 3) The temperature and ph of the environment 4) the concentration of the agent used to kill the microbe 5) the mode of action (MOA) of the agent. How does it kill or inhibit the microbe?

2 4) Describe the four modes of action for a good antimicrobial agents. (8 pts) 1) Cell wall, 2) cell membrane; 3) cellular synthesis processes (DNA RNA); 4) Denaturation of Protein 1) Cell Wall: a)blocking cell wall synthesis; b) digesting the cell wall; c) breaking down the cell wall i.e. penicillin, detergents and alcohols 2) Cell membrane a) surfactants: lower surface tension of cell membranes disrupting phospholipid bi-layer resulting in leaky membranes 3) cellular biosynthesis of DNA RNA a) agents irreversibly binds to DNA preventing it transcription b) agents can cause mutations in coding genes 4) Altered Protein function a) Denaturation of 3D structure b) Metallic ions bind to active sites of proteins preventing interactions with substrates 5) Compare and contrast the relative effectiveness of moist heat to that of dry heat? (Please make a Table for this descriptive purpose (12 pts)) Moist heat: Dry heat : Steam under pressure Autoclave 121 C for 15 min vs. 134 C for 3 min Non-pressurized steam Tyndallization intermittent sterilization repeated heating cycles over 60 min time several times repeated. Boiling water Boiling water (100 C for 30 minutes) does not kill resistant spore be will kill most non-spore forming microbes Pasteurization (See table provided during lecture) Oven heat at 121 C for 120 minutes vs. 170 for 60 minutes Dehydrates cells Denature cells Oxidizes cells 6) What is considered an effective temperature and time for the Pasteurization of milk products without destroying milk favor? (4 pts) Flash method: 71.6 C for 15 seconds. This method is preferable beacuse it is less likely to change flavor or nutrient content and effective against Coxiella and Mycobacterium.

3 7) Draw, annotate and discuss the following graphs for a good bacteriostatic, bacteriocidal, and bacteriolytic agents upon microbial population. (Label the graph) (12 pts) See attached appendix material 8) Ultra violet (U.V.) radiation can be used for sterilization. At what frequency does U.V. radiation work at; What is it s mode of action; B) limitations and C) where would UV light be used to control microbes? (5 pts) A frequency of 185 and 260~5 nm. Mode of Action (MOA) surface sterilant causing pyrimidine dimers, also causing photochemical products called free radicals. UV radiation passes through air slightly through liquids, and poorly through solids. Used in hospital rooms, operating tables, food preparation areas, and dental offices. Also used to curtail the growth of microbes in food processing plants and slaughterhouse. 9) How is food lyophilizing? Is a food product sterilized by this method? Why or why not? (6 pts) Food is freeze dried at low temperatures low pressure. Microbes require water to live and are not necessarily killed by this method of food preservation. Upon rehydration microbial decay once again begin its activity. 10) How does cooling cooked food products down to 3.3 C reduce spoilage? Explain! Does freezing temperature kill microbes such as Clostriduim? Why (6 pts) Most food destroying microbes live best at 37 C. Cooling food to 3.3 C reduces a favorable environment for microbial growth but does not necessarily stop its growth. On the other hand, while freezing stops microbial growth it does not kill microbes such as Clostriduim.

4 11) Provide 3 examples that antiseptic methods can be employed to prevent bacterial entry into the human blood system in the medical profession (6 pts) 1) Preparing the skin before surgical incisions with iodine compounds 2) Swabbing an open root canal with hydrogen peroxide 3) Ordinary hand washing with a germicidal soap 12) What is the mode of action of chorine, soaps, and heavy metals? (9 pts) Chlorine organic oxidant of sulfhydryl groups and interferes with disulfide bridges. Highly affect disinfectants and antiseptics Toxic to living tissues soups sufactants emulsifies microbes and disrupts their membrane integrity Heavy metals (Zinc, silver, mercury) Binds to Metals are very toxic to humans if functional protein groups ingested, inhaled, or absorbed in-activating them. through the skin. Causes allergic reactions G:\Tests\Microbiology Test\Work sheet\sanitation\micro 231 Lec Test 3 F06 take home_answers B.wpd Appendix

5 Log of Cells Total Count Viable Count Bacteriostatic Time

6 Log of Cells Bacteriocidal Time

7 Log of Cells Bacteriolytic Time