Biol 251 chapter 7

• Condition of body, refers to bacteria contamination as septic tanks for sewage treatment
• The term also used to describe a disease condition

• Absence of significant contamination
• Aseptic surgery technique prevent the microbial contamination of wounds
• Process of trying to prevent significant contamination
• Asepsis means object or area free of pathogen

• Removal or destruction of all living microorganisms
• Heating is the most common method used for killing microbes including the most resistant forms such as endospores
• A sterilizing agent is called a sterilant,
• Liquid or gas can be sterlized by filteration

• Killing Clostridium botulium endospres from canned food
• Only killing harmful to human or case food spoilage
• Heat up just enough to kill endospores 
• Not complete sterilization - still some bacteria presenc

• Destroying harmful microorganisms from non living surfaces
• Chemical disinfectant is used to non living surfaces such a tale
• Chemical, ultraviolet radiation, boiling water, steam

• Destroying harmful microorganisms on living tissue
• It will kill vegetative bacteria
• Alcohol can be used both living or non living microorganisms

• mechanical removal of microorganisms from a limited area
• Not killing, removing - Alcohol swap scrubbing (washing) hands

• Lowering microbial counts to safe public health determent level that's safe
• Hot dishwasher, chemical rinse

• Treatment that kills microbes
• Do not kill endospores, only vegetative cells

• Inhibit the growth of microbes - not killing
• Hole the growth
• Prevent the growth at that time, once process is stopped, it will continue to grow - resume normal activity

Heat,  Low temperature, Filtration, High pressure, Desiccation, Osmotic pressure, Radiation

Heat appears to kill microbes by denaturing their enzymes; the resultant changes to the three dimensional shape of those proteins

Moist heat sterilization, pasteurization, sterilization, dry heat serilization

• Boiling - kill enveloped virus
• Autoclave (steam) - kill all including endosproes but not prions

• Mild heat, enough to kill pathogens
• High temperature short time (HTST), 72 degree Celsius for 15 seconds
• Kill pathogens and food spoilage agents without destroying the food
• Can not kill thermoduric - heat resistant bacteria

• Ultra high temperature (UHT) - 140 degree Celsius for 4 seconds
• Milk and store many months without refrigeration
• Kills vegetative cells, viruses, endospores

• Dry heat kills by oxidation effects - direct flaming
• Incineration - effective way to sterilize and dispose of contaminated paper cubs, bags,and dressings; complete destruction of everything - reduce to ash
• Hot-air sterilization (oven) - 170 degree Celsius for over 2 hours ; sterilized by this procedure are placed in an oven

• Low temperature has bacteriostatic effect
• Metabolic rate of most microbes reduced that they cannot reproduce or synthesize toxin
• Pathogenic bacteria generally will not grow at refrigerator temperatures, but Listeria is one important exception
• Refrigeration, deep freezing, Lyophilization (freezing dry)

• Removal of microbes
• Passage of a liquid or gas through a screen-like material with pores small enough to retain microorganisms
• Filtration is used to sterilize heat-sensitive materials, such as culture media, enzymes, vaccines and antibiotic solutions
• HEPA (high efficiency particle air) used in burn patient's room; filter air to lower the number of airborne microbes, remove almost all microorganisms larger than 0.3 micrometer in diameter
• Membrane filter - composed of substances as cellulose esters or plastic polymers industrial & laboratory use

• Rapid inactivation of vegetative bacterial cells
• Endospores are relatively resistant to high pressure
• Fruit juices preserved by high pressure treatment

• Remove water - inhibit chemical reaction and stop microbiol growth
• Absence of water prevent bacteria metabolism
• Dry them out - prevent water go tot bacteria
• Wen water is available, they resume growth and division - Lyophilizaiton or freezing dry

• Hypertonic environment - remove water
• High concentration of salt or sugar to preserve food is based on the effects of osmotic pressure
• High concentration of these substances create a hypertonic environment; cause plasmolysis (shrink) - water leaves microbial cell
• Molds and yeast are much more capable than bacteria growing in materials with low moisture or high osmotic pressure - resistant

• High energy waves causes DNA damages
• Two types of radiation - Ionizing radiation and Non ionizing radiation

• Gamma ray, x-ray, high-energy electron beams
• Ionization of water to create high reactive hyroxyl radicals, these radicals kill organisms by reacting with organic cellular components especially DNA and damage them
• Damage DNA by causing lethal mutation
• More "hits" are likely to cause sufficient mutations to kill the microbes
• High energy electron beans used to sterilize pharmaceutical and disposal dental and medical supplies such as plastic, syringes, surgical gloves

UV light damages the DAN of exposed cell by causing bonds to form between adjacent pyrimidine bases, usually thymine in DNA chains Thymine dimers inhibit correct replication of the DNA during cell replicationUV wavelength most effective for killing microorganisms at 260 manometerMicrowave - do not have much effect on microorganisms