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microbio exam [pt.4]
lecture 8: control of microbial growth
| Question | Answer |
|---|---|
| Define Sterilization | Killing of all like forms including endospores in the object or on its surface |
| Define Disinfection | Destruction of vegetative pathogens but NOT endospores. Not safe to use on living tissues |
| Define Antisepsis | Sepsis: presence of pathogens or their toxins in tissue or blood. Antisepsis: destruction of vegetative pathogens ON living tissue |
| Define Degerming | Mechanical removal of microbes from the skin |
| Define Sanitization | Mechanical removal of pathogens from public eating utensils and objects |
| -cide | Agent which kills is given the suffix -cide. Works by denaturing proteins and is NOT reversible |
| Define Bactericide | Kills bacteria |
| Define Bacteriostasis | To inhibit microbial growth by means other than killing. Inhibition IS reversible. |
| What are some factors that affect death rate of microorganisms? | Number & type of microorganisms, temperature and pH of environment, concentration of agent, mode of action of agent, presence of organic matter and time |
| What are the mechanisms of action of antimicrobial agents? | Cell wall, Plasma membrane, Nucleic acid, Protein synthesis and Inactivation of proteins |
| How does HEAT control microbial growth? | Works by denaturing proteins |
| What is Thermal death point? | lowest temp. at which all the microbes will be killed in 10 mins |
| What is Thermal death time? | shortest length of time required to kill all microbes at a specific temp. |
| How does Moist Heat control microbial growth? | Kills by denaturing nucleic acids and proteins. More effective than dry heat. (Boiling, Autoclaving, Pasteurization) |
| What is the boiling temp. and time to kill microorganisms? | Form of moist heat of boiling at 100C for 30 mins kills all microorganisms except some endospores (sterilizaton). Boiling point at 100C for 10 mins kills most vegetative cells but NOT endospores (disinfection) |
| What is the effect of Autoclaving on microbial growth? | Form of moist heat that is applied ABOVE normal-atmosphere boiling point of water. Kills all forms of life including endospores |
| What is the effect of Pasteurization on microbial growth? | Form of moist heat that is LESS THAN boiling temp. of foods to prevent growth of food-spoiling organisms. Does NOT kill all microbes |
| How does Dry Heat control microbial growth? | Proteins don't denature as easily (Baking & Incineration). Requires higher temperatures than moist heat to result in sterilization. |
| What is the effect of Baking in microbial growth? | Form of dry heat which is commonly used as sterilization treatment. 160C for 2-4hrs or 170C for 1hr |
| What is the effect of Incineration in microbial growth? | Form of dry heat used to vaporize organic material on nonflammable surfaces. ~500C |
| How does Low Temperature control microbial growth? | Low Temperature slows down bacterial metabolism |
| What is the effect of Refrigeration on microbial growth? | Form of low temperature which slows the growth of organisms rather than preventing it. Short term solution |
| What is the effect of Freezing on microbial growth? | Form of low temperature used to more completely delay organisms' metabolism. Pathogens can survive in freezers |
| How does Filtration control microbial growth? | Physical removal of all cells in a liquid or gas. Used for sterilizing solutions that would denature with heat. Toxins can pass |
| How does Sonication control microbial growth? | Transmit through water filled chamber (sonicator) which causes cells to burst |
| How does Desiccation and Osmotic pressure control microbial growth? | Removal of water (drying) and prevents organism metabolism. Used to preserve food |
| How does Radiation control microbial growth? | Detroys nucliec acid |
| What is the effect of Ionizing Radiation on microbial growth? | Form of radiation used to produce free radicals that destabilizes molecules. Antimicrobial in food preservation. (Xrays and Gamma rays) |
| What is the effect of Ultraviolet (UV) Radiation on microbial growth? | Form of radiation used for disinfecting surfaces and air. Food can be irradiated to increase shelf life up to 500% |
| What are some chemical agents used to control microbial growth? | Halogens, Phenol, Chlorhexidine, Alcohols, Detergents and Soaps |
| How does Halogens control microbial growth? | Harmful or lethal to biological organisms in sufficient quantities. Non-metal and highly reactive |
| What is the effect of Chlorine on microbial growth? | Type of halogen used to denature proteins by disrupting disulfide bonds. Used to disinfect drinking water |
| What is the effect of Iodine on microbial growth? | Type of halogen used to denature proteins by disrupting disulfide bonds. Used in antiseptic and antimicrobial agent for emergency to purification of H2O |
| How does Phenol control microbial growth? | Used to disinfecting materials contaminated with organic material |
| Phenolic compound | Triclosan - antibacterial compound added as an antibacterial agent in soaps, cosmetics and medications |
| How does Chlorhexidine control microbial growth? | Chemical antiseptic used as a bactericidal to both Gram-positive and Gram-negative microbes but NOT endospores. (Added to mouthwash) |
| How does Alcohol control microbial growth? | Dissolves membrane lipids. Antiseptic used on skin (degerming) |
| How does Detergent control microbial growth? | Disrupt plasma membrane and permeability properties by inserting into membrane and creating abnormal channels. |
| Detergent compound | Quaternary ammonium compounds (quats) - Effective in destroying a broad spectrum of harmful microorganisms |
| How does Soaps control microbial growth? | Physically removes pathogens from surfaces by cleaning the surface (degerming). Inhibit bacteria sensitive to high pH's |
| How does Heavy metal control microbial growth? | Interfere with hydrogen bonds of proteins, resulting in protein denaturation and death of cell |
| Silver nitrate | Used to treat eyes of newborns |
| Copper sulfate | Used to treat ponds as an anti-algal |
| Selenium | Used as anti-fungals |
| Zinc | Used in mouthwash |
Created by:
jnguyen
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