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Bio 234 Amy Does
Lecture 7B
| Question | Answer |
|---|---|
| Sterilization | kills all living orgaimsms on object, including endospores |
| Disinfectants | do not kill all organisms and spores, used on inanimate objects |
| Antiseptic | used on living tissue. Does not kill all organisms. |
| Degerm | E.g. swabbing with alcohol. Mostly mechanical removal of microbes. Limited effectiveness. |
| Sanitization | Lowers numbers of microbes. E.g. high temperature dish washing. |
| Germicide | Kills microorganisms; may not be effective on all types. |
| Bacteriostat | Stops microorganisms from growing. |
| Disinfectants and Antiseptics | Inactivate enzymes (change the shape; like frying an egg) e.g. heat; ammonia |
| Disinfectants and Antiseptics - Injure plasma membranes | Damage proteins or lipids e.g. alcohol |
| Disinfectants and Antiseptics Damage DNA | ionizing radiation - gamma radiation ionizes water to form hydroxyl radicals. H2O ---> H+ and OH-. These radicals react with DNA and protein |
| Disinfectants and Antiseptics non ionizing radiation - | UV light causes thymine dimers to form . Replication of DNA can be disrupted. Sometimes the repair mechanisms of cell can get rid of the dimers. Sometimes not |
| Factors that Influence microbial death | Number of organisms (note that kill is expressed as log of # of cells) |
| Microbial characteristics mycobacteria | e.g. M. tuberculosis, cell wall has large amt of lipid, so resistant to environment stress like drying. also resistant to many disinfectants |
| Microbial characteristics endospores | e.g. Bacillus |
| Microbial characteristics gram -/+ | in general gram + easier to kill with H2O soluble disinfectants (gram+'s more resistant to drying and physical disruption because of thick peptidoglycan layer; Psudomonads (gr-) are very hard to kill and have been found in hospital disinfection solutions |
| Microbial characteristics Organic matter | pH (easier to kill with heat if environment more acid) |
| List 3 factors determining effectiveness of disinfection | Time, concentration of disinfectant, temperature |
| Physical Methods of Disinfection- Heat (moist) | Moist (autoclave (fig. 9.7 and 9.8 121°C 15 min. Kill is more effective in presence of water. Kills endospores too. Organic material does not interfere) Autoclaves are tested using an endospore former (Baciluus stearoathermophilus) |
| Physical Methods of Disinfection- Heat (Dry) | (flaming, 170°C 2 hrs.-- less efficient. Takes longer. Must be hotter.) |
| Physical Methods of Disinfection- Pasteurization | Does not kill everything. 63°C 30 min. takes care of almost all pathogens, incuding M. tuberculosis |
| Physical Methods of Disinfection- Cold | Remember the psychrophiles!, generally bacteriostatic |
| Physical Methods of Disinfection- Filtration | (blank) |
| Physical Methods of Disinfection- Drying | Not reliable, esp. if organic material around |
| Physical Methods of Disinfection- Radiation | Interrupts the ability of DNA to accurately replicate |
| Physical Methods of Disinfection- Chemical Methods phenols/biguanides | chlorhexidine surgical scrub injues plasma membranes ; phenols like listerine are most effective above 1% and denature enzymes. |
| Physical Methods of Disinfection- Chemical Methods halogens | chlorine, iodine. Iodine interacts with the amino acid tyrosine |
| Physical Methods of Disinfection- Chemical Methods alcohol | disrupts lipids denatures enzymes. 70-95% is most effective. Having a little water mixed in increases the effectiveness of the alcohol as a disinfectant. Alcohol-based agents for cleaning skin have been found as effective as good hand washing with soap. |
| Physical Methods of Disinfection- Chemical Methods surface active agents | soaps and detergents are by themselves not all that effective against killing bacteria. Mostly they work by mechanically removing dirt and bacteria, and emulsifying oils --helping to lift bacteria off surfaces. The alkaline nature of soaps help kill some. |
| Disinfection- Quats | quarternary ammonium compounds. e.g. benzelkonium chloride and Zepherin. These are more effective for gram negatives than gram positive and may not work for TB, or endospores. They are effective for fungi. |
| Disinfection - aldehydes | Wavicide, Cidex. 2% glutaraldehyde sols. which can be quite effective. Used for soaking surgical equip.(endoscopes, etc.) which can't be autoclaved. Soak time can be critical. Often used for 15-20 mins. Might need 3+ hrs for efficacy |
| Disinfection - peroxides | hydrogen peroxide. Although used on skin it is quickly broken down by enzymes in skin and other tissues. It is better used on surfaces. |
| Types of Water used in Hospitals - distilled | Water can be distilled (heated and recondensed to remove chemical contaminants |
| Types of Water used in Hospitals - deionized | run thru special filters to remove ions such as cholorine and sodium |
| Types of Water used in Hospitals - Pyrogen Free | Pyrogens are a lipopolysaccharide in the outer membrane of gram - cell walls. When gram - cells are killed or die these pyrogens are released into the bloodstream causing blood clots, shock, death. Must be tested and proven pyrogen free Used for inject |
Created by:
lkforney