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Control of Microbial
Disinfectants
| Question | Answer |
|---|---|
| Sepsis | microbial contaminatin |
| asepsis | absence of significant microbial contamination |
| aseptic surgery techniques | prevent microbial contamination of wounds |
| sterilization | removal of all forms of microbial life |
| commercial sterilization | killing c. botulinum endopores in canned food |
| disinfection | removal of pathogens (vegetative cells, non-endospore formers), not the same as sterilization, inert surface/substance |
| antisepsis | removal of pathogens from living tissue |
| degerming | removal of microbes from a limited area (mechanical removal, skin swabbed w/alcholo) |
| sanitization | lower microbial counts on eatingutensils (decrease transmission of disease, safe public health) restaurant/bar |
| biocide/germicide | kills microbes, fungicide, virucide |
| bacteriostasis | inhibititing, not killing, microbes if substance is removed, microbes may grow |
| actions of microbial agents | 1.alteration of membrane permeability-damages the lipids/proteins of the cell membrane. 2. damage to proteins 3. damage to nucleic acids -can't replicate/carry out protein synthesis |
| physical methods of microbial control | 1.Heat - Moist heat, pasteurization, dry heat 2. Filtration - Refrigeration, deep freezing, lyophilization 3. Low temps 4. dessication 5. osmotic pressure 6. radiation |
| physical methods : heat | one of 1st means of controlling microbial growth, still one of the most useful and reliable methods, inexpensive fast and effective, doesn't introduce potentially harmful substances, kills most organisms by denaturing enzymes and other proteins |
| physical methods>heat>moist heat>boiling/flowing steam | 100C, kills vegetative forms of:bacterial pathogens, almost all viruses, fungi, and their spores in 10 minutes, spores and some viruses not affected by 10mins of boiling, denatures proteins (coagulate, egg white cooking), not a reliable sterilizing method |
| physical methods>heat>moist heat>autoclaving | more reliable form of sterilizing, reaches temps above boiling, steam under pressure : 15 psi, 15 minutes, 121C, flash autoclave surgical instruments:3 minutes, 135C, used for materials that cannot be damaged by heat or steam |
| physical methods>heat>pasteurization | reduces spoilage organisms and pathogens, not endospores - developed by Louis Pasteur to avoid spoilage of wine/beer w/o destroying taste, not a method of sterilization - equivalent treatments (increased heat = less time) classic pasteurization (63c/30min |
| pasteurization | today use high temp short time (72c/15sec), ultra-high tem (140c, <1 sec) no need to refrigerate, thermoduric organisms survive pasteurization but don't spoil refrigerated milk |
| physical methods>heat>dry heat sterilization | kills by oxidation - heat in absence of moisture, burns cells: flaming - direct heating, loop in lab: incineration- sterilizes contaminated paper cups, bags, and dressings : hot air sterilization - ovens used to sterilize glass petri dishes |
| physical>heat>dry heat sterilization advantages/disadvantages | advantage - can use for powders/metal : disadvantage - takes longer : equivalent treatments Hot air (170c/2hr) Autoclave (121C/15min) |
| physical methods>filtration | removes microbes by passing liquid/gas through a screen-like material or filter : pore size is important : can sterilize vaccines, culture media, drugs that may be heat sensitive : HEPA filters are used to filter the air in rooms |
| physical methods > low temperatures | inhibits/slows microbial growth (bacteriostatic) : useful in preservation: Refrigeration (0-7C) preserve food and cultures : deep-freezing (-50--95C) preserve food, cultures, drugs, ice crystals can damage cells |
| physical>low temps>lyophilization | freeze drying, freeze first, then dry in a vacuum, water reconstitutes |
| physical methods > dessication | removes H2O from microbial cells : prevents metabolism : bacteriostatic : used to preserve dried fruit, beef jerky |
| physical methods > osmotic pressure | use salt/sugar to increase osmotic pressure : causes plasmolysis : bacteria can't grow, molds and yeasts can |
| physical methods > radiation | varius effects on cells depends on : shorter wavelength = more destruction, intensity, duration, damages cellular DNA as hits are taken by the cell : ionizing (x-rays, gamma rays, electron beams) : non ionizing (UV) : microwave |
| physical > radiation > ionizing radiation | xrays, gamma rays, electron beams : shorter wavelength : carries much more energy : ionizes H2O : food industry use low level of radiation : spices, some meats/veggies : sterilize pharmaceuticals and disposable dental and medical supplies, plastic syringe |
| physical methods > nonionizing radiation | UV rays : wavelength larger than ionizing : destroys DNA chains (thymine, incorrect replication) in exposed cells : UV lights (germicidal) are seen in hospital rooms, operating rooms, and cafeterias : disadvantage - the rays don't penetrate, direct hit ki |
| physical > radiation > microwave | not especially antimicrobial : no direct effect on microbes : kill by moisture from heating food |
| chemical methods > principles of effective disinfection | concentratoin of disinfectant - dilute specifically as directed by manufacturer : organice matter - prohibit direct contact w/microbes, presence of this may decrease effectiveness of disinfectant : pH of medium : time - a gradual process |
| chemical methods > evaluating a disinfectant | use dilution test - metal rings dipped in test bacteria are dried, then placed in disinfectant for 10 min @ 20C, rings transferred to culture media to determine whether bacteria survived treatment : disk - diffusion method |
| types > phenol | carbolic acid : lister first to use in OR to control surgical infections : causes irritation to the skin/disagreeable odor |
| types > phenolics | chemically altered phenol : reduces irritation : lysol - good surface disinfectant |
| types > bisphenols | Hexachlorophen (in pHisoHex) - G+ staph and strep are very sensitive to, overuse can lead to neurological damage in infants : triclosan - found in toothpaste, soaps, doesn't kill all viruses, disrupt plasma membranes |
| types > biguanides | chlorhexidine : broad spectrum of activity : used for degerming skin and mucous membranes : combined w/alcohol or a detergent (surgical scrub, preoperative skin prep of pt) : low toxicity of skin/m membranes : biocidal - not eff w/spores |
| types > halogens > iodine | eff antimicrobial agents : betadine (povidone-iodine) : one of oldest/most eff antiseptics : tincture form also (w/alcohol) : eff against all bact, spores, fungi, some viruses : thought to combine with a.a.'s of enzymes : used for skindisinfect/wounds/H2O |
| types > halogens > chlorine | bleach is a hypochlorous acid (HOCL/germicidal) : used to disinfect water /dairy equip/ hemodialysis systems / household items : use in small amounts - toxic and corrosive |
| types > alcohols | ethanol/isopropanol : used as antiseptic/disinfectant : bactericidal/fungicidal : us 70% alcohol which contains some water : not eff in presence of organic matter : used for degerming before inj & waterless soap : denature proteins, dissolve lipids |
| types > alcohols disadvantages | evaporates rapidly, most effective w/increased exposure, unsatisfactory antiseptic for wounds |
Created by:
jbvaughan
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