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Microbio Unit 3
Terms in this set (78)
The killing or removal of all microorganisms in a material or on an object
The reduction of the number of pathogenic microorganisms to the point where they pose no danger of disease
A chemical agent that can safely be used externally on living tissue to destroy microorganisms or to inhibit their growth
A chemical agent used on inanimate objects to destroy microorganisms. Most disinfectants do not kill spores.
A chemical agent typically used on food-handling equipment and eating utensils to reduce bacterial numbers so as to meet public health standards. Sanitization may simply refer to thorough washing with only soap or detergent.
An agent that inhibits the growth of bacteria
An agent capable of killing microbes rapidly; some such agents effectively kill certain microorganisms but only inhibit the growth of others
An agent that kills bacteria. Most such agents do not kill spores.
An agent that inactivates viruses
An agent that kills fungi
An agent that kills bacterial endospores or fungal spores
The control of Microbial growth (3 steps)
A definite proportion of the organisms die in a given time interval
The fewer organisms present, the shorter the time needed to achieve sterility
Microorganisms differ in their susceptibility to antimicrobial agents
Numerical expression for the effectiveness of a disinfectant. A disinfectant with a phenol coefficient of 1 has the same effectiveness as phenol. If the coefficient is less than 1 that means the disinfectant is less effective than phenol; a coefficient greater than 1 means that it is more effective.
Filter paper method
Method of evaluating the antimicrobial properties of a chemical agent using filter paper disks placed on an inoculated agar plate.
The Use-Dilution Test
A method of evaluating the antimicrobial properties of a chemical agent using standard preparations of certain test bacteria
An ideal disinfectant should:
1. Be fast acting even in the presence of organic substances, such as those in body fluids.
2. Be effective against all types of infectious agents without destroying tissues or acting as a poison if ingested
3. Easily penetrate material to be disinfected without damaging or discoloring the material
4. Be easy to prepare and stable even when exposed to light, heat, or other environmental factors
5. Be inexpensive and easy to obtain and use
6. Not have an unpleasant odor
Alteration of protein structure. Hydrogen and disulfide bonds are disrupted and shale of protein molecule is destroyed. It is considered bacteriostatic if it temporarily alters protein.
Mild heat, some dilute solids temporarily alters protein.
Hydrolysis, oxidation excess heat permanently denature protein
Soaps and detergents
Lower surface tension, make microbes accessible to other agents;hand washing, laundering, sanitizing kitchen and diary equipment.
Dissolve lipids, disrupt membranes, denature proteins, and inactivate enzymes in high concentrations; act as wetting agents in low concentrations; Cationic detergents are used to sanitize utensils, anionic detergents to launder clothes and clean household objects, quaternary ammonium compounds are sometimes used as antiseptics on skin
Ionized into sodium ions and long hydrocarbon chains. Zigzagged covalently bonded tails able to enter an insoluble substance like grease. Other end of molecule has a carboxyl group with negatively charged oxygen which attract positively charged sides of water molecules thereby making the attached insoluble substance soluble in the wager so the substance can be washed away.
Lower pH and denature proteins;Food preservation
Raise pH and denature proteins;Found in soaps.
Denature proteins; silver nitrate is used to prevent gonococcal infections, mercury compounds disinfect skin and inanimate objects, violet to inhibit algal growth, and selenium to inhibit fungal growth.
Oxidize cell components in absence of organic matter; chlorine is used to kill pathogens in water and to disinfect utensils, iodine compounds are used as skin antiseptics.
Denature proteins when mixed with water; isopropyl alcohol used to disinfect utensils, iodine compounds are used as skin antiseptics.
Disrupt membranes, denature proteins, and inactivate enzymes; not impaired by organic matter; used to disinfect surfaces and destroy discarded cultures, amylphenol destroys vegetative organisms and inactivates viruses on skin and inanimate objects, chlorhexidine gluconate is especially effective as a surgical scrub.
Disrupt disulfide bonds. ;clean puncture wounds, disinfect instruments.
Disrupt structure of proteins and nucleic acids;Disinfect and sterilize inanimate objects that would be harmed by high temperatures. Formaldehyde.
May interfere with replication or block cell wall synthesis;acridine used to clean wounds, crystal violet to treat some protozoan and fungal infections.
Thermal death point
The temperature that kills all the bacteria in a 24-hour-old broth culture at neutral pH in 10 minutes
Thermal death time
The time required to kill all the bacteria in a particular culture at a specified temperature
Decimal Reduction Time (DRT or D value)
Length of time needed to kill 90% of the organisms in a given population at a specified temperature
Denatures proteins. Penetrates substances more slowly then moist (steam) heat. Used to sterilize metal objects and glassware and is the only suitable means of sterilizing oils and powders.
Oven heat used to sterilize glassware and metal objects, open flame used to incinerate microorganisms.
Denatures proteins-Boiling water destroys vegetative cells of most bacteria and fungi.
Autoclaving sterilized media, bandages, and many kinds of hospital and laboratory equipment not damaged by heat and moisture, pressure cooking sterilizes canned foods.
Denatures proteins; kills pathogens in milk, dairy and beer.
Slows the rate of enzyme-controlled reactions; used to keep fresh foods for a few days does not kill most microorganisms.
Greatly slows the rate of most enzyme-controlled reactions- used to keep fresh foods for several months does not kill microorganisms used with glycerol to preserve microorganisms.
Inhibits enzymes; used to preserve some fruits and vegetables sometimes used with smoke to preserve sausages and fish.
Dehydration inhibits enzymes; Used to manufacture some instant coffees; used to preserve microorganisms for years.
Denatures proteins and nucleic acids; used to reduce number of microorganisms in air in operating rooms, animal rooms, and where cultures are transferred
Denatures proteins and nucleic acids;used to sterilize plastics and pharmaceutical products and to preserve foods.
Absorbs water molecules, then releases microwave energy to surroundings as heat;cannot be used reliably to destroy microbes except in special media-sterilizing equipment.
Strong visible light
Oxidation of light sensitive materials;Can be used with dyes to destroy bacteria and viruses. May help sanitize clothing.
Sonic and ultrasonic waves
Cause cavitation;Not a practical means of killing microorganisms but useful in fractionating and studying cell components.
Mechanically removes microbes; used to sterilize media, pharmaceutical products, and vitamins, in manufacturing vaccines, and in sampling microbes in air and water
Removes water from microbes; used to prevent spoilage of food such as pickles and jellies.
The use of chemical substances to treat various aspects of disease
Term coined by Paul Ehrlich
(Also called drug) Any chemical substance used to treat disease
A special group of chemotherapeutic agents used to treat diseases caused by microbes.
The natural production of an antimicrobial agents by a bacterium or fungus.
Ex. streptomycin by Selman Waksman
Agents synthesized in the laboratory
Antimicrobial agents made partly by laboratory synthesis and partly by microorganisms
The ability of an antimicrobial agent to harm microbes without causing significant damage to the host
Toxic dosage level
Amount of a drug necessary to cause host damage
Therapeutic dosage level
Level of drug dosage that successfully eliminates a pathogenic organism if maintained over a period of time
maximum tolerable dose per kilogram of body weight, divided by the minimum dose per kilogram of body weight, that will cure the disease
Spectrum of activity
Refers to the range of different microbes against which an antimicrobial agent is effective
Referring to the range of activity of an antimicrobial agent that attacks a wide variety of microorganisms
The range of activity of an antimicrobial agent that attacks only a few kinds of microorganisms.
Substances that affect the utilization of metabolites and therefore prevent a cell from carrying out necessary metabolic reactions.
Mimic or imitate, the normal molecule, preventing a reaction from occurring or causing it to go awry.
A secondary infection from the removal of normal microbiota, allowing colonization by pathogenic, and often antibiotic-resistant, microbes
The ability of a microorganism to remain unharmed by an antimicrobial agent.
Due to a mutation in chromosomal DNA and will usually be effective only against a single type of antibiotic
Drug resistance of a microorganism due to the presence of resistance (R) plasmids
Resistance (R) plasmids or R factors
(also called R factor) A plasmid that carries genes that provide resistance to various antibiotics or toxic metals.
Mechanisms of Resistance
1. Alteration of targets
2. Alteration of membrane permeability
3. Development of enzymes
4. Alteration of an enzyme
5. Alteration of a metabolic pathway
Resistance against two or more similar antimicrobial agents through a common mechanism
Referring to an inhibitory effect produced by two antibiotics working together that is greater than either can achieve alone.
Disk diffusion method
(also called Kirby-Bauer method) A method used to determine microbial sensitivity to antimicrobial agents in which antibiotic disks are placed on an inoculated Petri dish, incubated, and observed for inhibition of growth.
Zone of inhibition
A clear area that appears on agar in the disk diffusion method, indicating where the agent has inhibited growth of the organism
A newer version of the diffusion test that uses a plastic strip containing a gradient of concentration of antibiotic to determine antibiotic sensitivity and estimate MIC (minimal inhibitory concentration)
A method of testing antibiotic sensitivity in which organisms are incubated in a series of tubes containing known quantities of a chemotherapeutic agent.
Minimum inhibitory concentration (MIC)
The lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation
Minimum bactericidal concentration (MBC)
The lowest concentration of an antibiotic that kills microorganisms, as indicated by absence of growth following subculturing in the dilution method. The lowest.
Serum killing power
Test used to determine effectiveness of an antimicrobial agent in which a bacterial suspension is added to the serum of a patient who is receiving an antibiotic and incubated
The liquid part of blood after cells and clotting factors have been removed.
Attributes of an ideal antimicrobial agent
1. It must be soluble in body fluids
2. It must have selective toxicity
3. Its toxicity must not easily be altered
4. It must be non allergenic
5. It must be stable so as to maintain serum levels for reasonable periods
6. Resistance to it is not easily acquired
7. It must have a long shelf life
8. It must be reasonable in cost
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