Chapter 9 Videos Flashcards
What does the suffix -cide or -cidal mean?
Suffixes indicate the destruction of a type of microbe. Or to Kill.
Germicides include ethylene oxide, propylene oxide, and aldehydes.
ex. Bactericide; fungicide; germicide;
virucide
What does the suffix -stasis or -static?
Suffixes indicating inhibition but not destruction of a type of microbe.
Germistatic agents include some chemicals, refrigeration, and freezing.
ex. Bacteriostatic; fungistatic; virustatic
What is Antisepsis?
Reduction in the number of microorganisms and viruses, particularly potential pathogens, on living tissue
Antiseptics are frequently disinfectants whose strength has been reduced to make them safe for living tissues.
ex. lodine; alcohol
What is Aseptic?
Refers to an environment or procedure free of pathogenic contaminants
Scientists, laboratory technicians, and healthcare workers follow standardized aseptic techniques.
ex. Preparation of surgical field; hand washing; flame sterilization of laboratory equipment
What is Degerming?
Removal of microbes by mechanical means
Chemicals play a secondary role to the mechanical removal of microbes.
Ex. Hand washing; alcohol swabbing at the site of injection
What is Disinfection?
Destruction of most microorganisms and viruses on nonliving tissue
The term is used primarily in relation to pathogens.
Ex: Phenolics; alcohols; aldehydes; soaps
What is Pasteurization?
Use of heat to destroy pathogens and reduce the number of spoilage microorganisms in foods and beverages
Heat treatment is brief to minimize alteration of taste and nutrients; microbes still remain and eventually cause spoilage.
Ex: Pasteurized milk and fruit juices
What is Sanitization?
Removal of pathogens from objects to meet public health standards
Standards of sanitization vary among governmental jurisdictions.
Ex: Washing tableware in scalding water in restaurants
What is Sterilization?
Destruction of all microorganisms and viruses in or on an object
Typically achieved by steam under pressure, incineration, or ethylene oxide gas.
Ex: Preparation of microbiological culture media and canned food
Sterilization vs disinfection
Sterilization: Kills all microbial, even endospores
Disinfection: Kills most
What is Microbial death?
The permanent loss of reproductive ability under ideal environmental conditions.
What is the Microbial death rate?
- used to evaluate the efficacy of an antimicrobial agent
- produces a straight line
- During each minute of exposure, the number of living cells will decrease by 10-fold.
What are the two main categories of Action of antimicrobial agents?
- Alteration of cell walls and cell membranes
- Damage to proteins and nucleic acids
Alteration of cell walls
- Function: maintains integrity of cell
- When damaged by physical or chemical methods…
- Effect: osmosis cause cells to burst (cell death)
Alteration of cytoplasmic membranes
- Function: contains cytoplasm and controls passage of chemicals into and out of the cell.
- When damaged by physical or chemical methods,
- Effect: cellular contents leak out (cell death)
Damage to proteins
Function: some function as enzymes, and their function depends on their 3-D shape
- When damaged by extreme heat or certain chemicals
- Effect: denature proteins, cease function (cell death)
Damage to nucleic acids
- Function: storage and expression of genetic information
- When damaged by chemicals, radiation, and heat
- Effect: can alter or destroy nucleic acids, produce fatal mutants, halt protein synthesis through action on RNA (cell death)
How are we going to pick a microbial control method?
Ideally, agents should be
* Inexpensive
* Fast-acting
* Stable during storage
* Capable of controlling microbial growth while being harmless to humans, animals, and objects
The site to be treated is one-factor affecting antimicrobial efficacy. Describe the character of the Site to be treated.
- Harsh chemicals and extreme heat cannot be used on humans, animals, and fragile objects
- Heat-resistant or heat sensitive
- Chemical resistant or chemical sensitive.
- Water-resistant or water sensitive
- Sterilization or disinfection (site dependent)
Relative susceptibilities of microbes to antimicrobial agents.
select a method to kill the hardiest microorganisms present
Why?
Endospores are the hardest to kill. If it kills endospores, it will kill all less resistant microbes as well.
What are three germicide classifications?
- High-level germicides
* Kill all pathogens, including endospores ( sterilization) - Intermediate-level germicides
* Kill fungal spores, protozoan cysts, viruses, and pathogenic bacteria
3 Low-level germicides
* Kill vegetative bacteria, fungi, protozoa, and some viruses
How does temperature affect the efficacy of anti-microbial methods?
Chemicals react faster at higher temperatures (warm disinfectants generally work better)
How does Ph or organic matter affect the efficiency of the antimicrobial method?
PH
* Low pH increases the effectiveness of some chemicals
* High Ph increases effectiveness in some chemical
* Example: household bleach works better at low pH
Organic matter
* The presence of organic matter can inactivate disinfectants
* organic material: fat, feces, vomit blood, biofilm, can interfere with the penetration of heat, chemicals, radiation, or it can inactive disinfectants.
Effects of High heat temperature.
- Denature proteins
- Interfere with the integrity of the cytoplasmic membrane and cell wall
- Disrupt structure and function of nucleic acids
- It can achieve sterilization and disinfection
What are heat-related methods?
- Moist Heat
- Dry Heat
What are the physical methods of microbial control?
- Heat
- Low Temp
- Radiation
- Filtration
Moist heat Characteristics and functions.
- Used to disinfect, sanitize, sterilize, and pasteurize
- Denatures proteins and destroys cytoplasmic membranes
- More effective than dry heat (water is a better conductor)
Methods of microbial control using moist heat
* Boiling
* Autoclaving (sterlize)
* Pasteurization
* Ultrahigh-temperature sterilization (sterilize)
Boiling water function, uses, and characteristics.
- Kills vegetative cells of bacteria and fungi, protozoan trophozoites, and most viruses
- Boiling time is critical
- Different elevations require different boiling times
- Endospores, protozoan cysts, and some viruses can survive boiling
- Does not achieve sterilization.
Autoclaving function, uses, and characteristics.
- Pressure applied to boiling water prevents steam from escaping
- Boiling temperature increases as pressure increases
- Autoclave conditions: 121°C, 15 psi, 15 minutes
- Achieves sterilization
- Moist heat
Pasteurization function uses, and characteristics.
- Moist heat
- Pasteurization
- Used for milk, ice cream, yogurt, and fruit juices
- Not sterilization
- Heat-tolerant microbes survive
- Pasteurization of milk
- Batch method
- Flash pasteurization
- Ultrahigh-temperature pasteurization
Ultrahigh-temperature sterilization function uses and characteristics.
Moist heat
* 140°C for 1 to 3 seconds, then rapid cooling
* Treated liquids can be stored at room temperature
Dry heat Characteristics and functions.
- Used for materials that cannot be sterilized with moist
heat (examples: Powders and oils) - Denatures proteins and oxidizes metabolic and structural chemicals
- Examples:
- Hot Air (oven): Requires higher temperatures for a longer time than moist heat
- Incineration
Refrigeration and Freezing Characteristics and functions.
- Decrease microbial metabolism, growth, and reproduction (does not achieve sterilization)
- Chemical reactions occur more slowly at low temperatures
- Refrigeration halts the growth of most pathogens
- Some microbes can multiply in refrigerated foods
- Slow freezing is more effective than quick freezing
- Organisms vary in susceptibility to freezing
Desiccation and Lyophilization Characteristics and Functions.
- Desiccation (drying) inhibits growth as a result of the removal of water
- Lyophilization (freeze-drying) is used for long-term preservation of microbial cultures
- Prevents the formation of damaging ice crystals
- Does not achieve sterilization
Filtration function uses and characteristics.
- the passage of air or a liquid through a material that traps and removes microbes.
- Liquids sensitive to heat
- a useful technique for sterilizing heat-sensitive materials.
- To prevent airborne contamination
by microbes
Osmotic Pressure function uses and characteristics.
- High concentrations of salt or sugar in foods to inhibit growth
- Cells in a hypertonic solution of salt or sugar lose water
- Honey, jams, salted fish, and pickles are foods preserved by osmotic pressure.
- Fungi have greater ability than bacteria to survive hypertonic environments
Ionizing radiation function uses and characteristics.
- Wavelengths shorter than 1 nm
- Electron beams, gamma rays, some X-rays
- Ejects electrons from atoms to create ions
- lons disrupt hydrogen bonding, oxidize double covalent bonds, and create hydroxyl radicals
- lons denature other molecules (DNA), causing mutations and death (achieve sterilization)
- Gamma rays penetrate well but require hours to kill microbes
- X-rays require a long time to kill microbes
- Not practical for microbial control
Nonionizing radiation function uses and characteristics.
- Wavelengths greater than 1 nm
- Excites electrons, causing them to make new covalent bonds
- Affects 3-D structure of proteins and nucleic acids
- UV light causes pyrimidine dimers in DNA
- UV light does not penetrate well
- Suitable for disinfecting air, transparent fluids, and surfaces of objects
Liquid chemical agents use methods.
Animate objects: Asepsis
Inanimate: Disinfection and Sterilization
Gas chemical agents use methods.
- Disinfection
- Sterilization
Phenol and phenolic function use and characteristics.
- Denature proteins and disrupt cell membranes
- Effective in presence of organic matter
- Remain active for prolonged time
- Commonly used in health care settings, labs, and homes
- Have disagreeable odor and possible side effects
- They are disinfectants
Alcohol’s function uses, and characteristics.
- Denature proteins and disrupt cytoplasmic membranes
- More effective than soap in removing bacteria from hands (but not diarrhea-causing viruses)
- Swabbing skin with alcohol prior to injection removes most microbes
- Is an disinfectant and antiseptic
- Does not achieve sterilization
Halogens function, uses, and characteristics.
- Include iodine, chlorine, bromine, and fluorine
- Damage proteins by denaturation
- Widely used in numerous applications
- lodine tablets, iodophores, chlorine treatment, bleach, chloramines, bromine disinfection, and the addition of fluoride to water and toothpastes
- Some can achieve sterilization and some are
disinfectants
Oxidizing Agents function, uses, and characteristics.
- Peroxides, ozone, and peracetic acid
- Kill by oxidation of microbial enzymes, specially anaerobes
- Some are sterilizing, disinfectants and antiseptics
- Hydrogen peroxide can disinfect and sterilize surfaces
- Not useful for treating open wounds because of catalase
Surfactants function, uses, and characteristics.
- “Surface active” chemicals
- Reduce surface tension and increase the ability of solvent to dissolve materials
- Breaks oil during degerming
Soaps - Good degerming agents but not antimicrobial
Detergents - Quaternary ammonium compounds (quats)
- Disrupt cellular membranes,
- Ideal for many medical and industrial applications
Heavy Metals function, uses, and characteristics.
- Arsenic, zinc, mercury, copper
- Heavy-metal ions denature proteins
- bacteriostatic and fungistatic agents
- Zinc:
- 1% silver nitrate, once commonly used to prevent blindness caused by N. gonorrhea
- Mouthwash and paint
- Thimerosal (mercury) used to preserve vaccines
- Copper controls algal growth
What are the disadvantages of heavy metals
- Can be very toxic to humans
- Often cause allergic reactions
- Large quantities of biological fluids and wastes
- neutralize their actions
- Microbes can develop resistance to them
Aldehydes function, uses, and characteristics.
- Cross-link functional groups to denature proteins and inactivate nucleic acids
- Glutaraldehyde disinfects and sterilizes
Gaseous Agent’s function uses and characteristics.
- Microbicidal and sporicidal gases used in closed chambers to sterilize items (heat, water, radiation sensitive)
- Denature proteins and DNA by cross-linking functional groups
- Used in hospitals and dental offices
- Examples:
- Ethylene oxide,
- Propylene oxide,
- Beta-propiolactone
Disadvantages of Gaseous Agents
- Can be hazardous to people
- Often highly explosive
- Extremely poisonous
- Potentially carcinogenic
Enzymes function uses and characteristics.
- Antimicrobial enzymes act against microorganisms
- Human tears contain lysozyme
- Digests peptidoglycan cell wall of bacteria
- Uses of enzymes to control microbes in the environment
- Lysozyme is used to reduce the number of bacteria in cheese
- Prionzyme can remove prions on medical instruments
Antimicrobials function uses and characteristics.
- Antibiotics and semisynthetic and synthetic chemicals
- Typically are used to treat disease
- Some are used for antimicrobial control outside the body
