Ch 11 Control Of Microbes Flashcards
Define disinfection
Destroys or removes most microbial life but not endospores, reducing contamination on inanimate surfaces
Define sterilization
The complete destruction or removal of all microbial life including endospores
Define antisepsis
Using chemicals called antiseptics to destroy or inhibit most microbial life, reducing contamination on animate surfaces
Define decontamination
The mechanical removal of most microbes from animate or inanimate surfaces. Does not use chemicals. Ex: filters
Define sanitization
Any cleansing technique that mechanically removes microbes as well as other debris
What does Bacteriocidal or bactericide do
Chemical that destroys bacteria, does not kill endospores
What does sporicidal or sporicide do
Chemical that destroys endospores
Bacteriostatic agents _____
Agents that prevent growth of bacteria on tissues or on objects in the environment
What two things have the highest resistance rating
Endospores and prions
What things have a moderate resistance rating
Some viruses, naked ones, more resistant; hepatitis B and poliovirus
Three specific bacteria that have moderate resistance ratings
Mycobacterium tuberculosis, Staphylococcus aureus, Pseudomonas
What things have a low resistance rating
Most bacteria vegetative cells, fungus - yeast, enveloped viruses
Four factors that affect the rate of microbial death
Length of exposure of the agent, microbial load, relative resistance, action of agent (cidal vs static)
An example of antimicrobial effects on cell wall
Alcohol can dissolve the outer membrane of the cell wall of gram-negative bacteria
What are surfactants
Detergents that have hydrophilic and hydrophobic regions that can physically bind to the phospholipid bilayer. Causes membrane to have open spots and creates leaks.
Three examples of when the mode of antimicrobial action is to disrupt the genetic molecules
Interferes with protein synthesis, interferes with DNA replication, mutate DNA
What is the thermal death time (TDT)
Shortest length of time required to kill all microbes at a specified temperature
What is thermal death point (TDP)
The lowest temperature required to kill all microbes in a sample in 10 minutes
Two examples of dry heat and what they accomplish
Dry oven, incineration; sterilization
Moist heat can accomplish what
Sterilization and disinfection
Two examples of steam under pressure and what it accomplishes
Pressure cooker, autoclave; sterilization
Three examples of steam not under pressure
Pasteurization, boiling, Tyndallization
Describe pasteurization
Disinfection of beverages. Technique in which heat is applied to liquids to kill potential agents of infection and spoilage, while still preserving the flavor and food value
Tyndallization
Intermittent sterilization; ex: Day 1: kills vegetative cells but not spores; day 2: spores germinated over night now get killed; day 3: kills off anything remaining
Boiling is only for _____
Disinfection
What type of control does cold have
Only retards the metabolic activities; slows metabolism does not kill
Desiccation
Loss of water due to being in a hypertonic environment. Dries it out; effective against everything except large cocci
Osmotic pressure
Loss of water due to being in a hypertonic environment due to high content of salt and sugars; large cocci do better; ex: process of curing or pickling
What is radiation
Energy that travels in the form of waves. Type of cold sterilization; causes mutations so severe that bacteria can’t survive it
Irradiation
Bombardment of radiation
Describe nonionizing radiation and give example
Does not cause the ionization of water, causes pyrimidine dimers to form. Ex: UV germicidal lamps
What are pyrimidine dimers
Formed when a covalent bond is formed between 2 adjacent pyrimidines (thymine and cytosine) in a DNA strand
Ionizing radiation and examples
Causes the ionization of water; “free radicals “; Ex: x-rays, gamma rays
Filtration and examples
Mechanical removal. Ex: HEPA filters (high efficiency particulate air filters)
Name six methods of physical control of microbes
Heat, cold, desiccation, osmotic pressure, radiation, filtration
What is the most common method of physical control of microbes
Heat
Explain halogens and give examples
All tend to form acids with water; bacteriocidal, sporicidal at higher concentrations; Ex: Chlorine, iodine, bromine.
How is chlorine a chemical agent of microbial control
It will form an acid when combined with water: Denatures enzymes.
Cl + H2O = HCL
Example of iodine and how it works
Betadine, interferes with hydrogen bonds and disulfide cross bridges in proteins
How is alcohol an effective chemical agent of microbial control
Dissolves the outer membrane of Gram negative microbes
How does hydrogen peroxide work
Forms free radicals which are toxic especially to any anaerobe
How do detergents work
Surfactants - disrupt the bilayer
