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Microbiology Tortora Chap Seven


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What are the two methods of control of Microbial growth?
Killing organisms or inhibiting their growth
Destruction or removal of all viable microorganisms equals?
What are the methods of physical controls?
heat, Radiation or filtration
What are the types of heat used?
Moist heat and dry heat
Which is more effective moist heat or dry?
Moist, it works faster and in a given time period will kill at lower tempertures
What are two types of moist heat?
Autoclave (a large pressure cooker) and Pasteurization
is Pasteurization a sterilization technique?
No does not lead to sterilization since not all organisms are killed.
What does dry heat do?
ignites microbes to ashes and gas
What are the two types of radiation?
Ionizing and nonionizing
Types of Ionizing radiation ?
Gamma rays, x-rays, and cathode rays
Ionizing radiation does two things.
Penetrates solids and liquids and damages DNA
Non Ionizing radiation is characterized by?
Ultra violet rays
What is filtration used for?
sterilizing air and heat sensitive fluids
Chemical agents that kill microorganisms have the suffix ?
Agents that only inhibit growth have the suffix
To be effective a static agent must be ?
continually present
An agent that is -cidal at high concentrations may be _____ at lower concentrations
Agents that disrupt target cell membrane or walls are called?
Germicides are?
agents that kill pathogens
3 types of germicides
Disinfectants antiseptics and chemotherapeutic agents
Germincides are catagorized by
What they can kill and toxicity
Name two disinfectants
lysol and bleach
do disinfedctants destroy endospores?
no only vegetative pathogens
Disinfectants should only be used on inanimate objects due to
high toxicity to tissues
Name two antiseptics
Listerine and hydrogen perioxide
antiseptics should be used
externally on skin and mucous membranes
Chemotherapeutic agents can be used
internally drugs
Major classes of anti microbial chemicals
Halogens, Phenol and derivatives, Alcohols, Hydrogen Peroxide, detergents, and ethylene oxide (gas)
These are nonmetallic elements that are microbicidal and sporocidal and are the active ingredients in 1/3 of all antimicrobials
Historically which is the most used halogen?
Chlorine compounds
This halogen causes denaturation of enzymes due to disruption of disulfide bonds
Chlorine Compounds
This halogen causes denaturation of proteins
Iodine compounds
This halogen is used for disinfection of drinking water, and disinfection of swimming pools
Chlorine compounds
Topical antispetics such as betadine is a
iodine compound
This class of chemicals disrupt cells walls and membranes at high concentrations and inactivate enzymes at low concentrations
Phenol and derivatives
items that disrupt cell walls and membranes is known as a
lytic agent
Examples of phenol are
lysol, triclosan and chlorhexidine
At concentrations of 50% and above this agent disrupts membranes
in the protoplasm at concentrations of 50-95% it denatures proteins
Alcohol is used for?
skin degerming and cold sterilization
This chemical releases oxygen which forms hydroxyl free radicals
hydrogen perioxide
This chemical is bactericidal, virucidal, fungicidal and sporocidal at high concentrations
Hydrogen perioxide
Uses of hydrogen perioxide include
skin cleansing, mouthwash and general disinfection
This chemical acts as a surfactants that disrupt cell membranes
Catatonic detergents ("quats") are most effective but
much more expensive to produce
Detergents are used for
disinfection/sanitization of hard surfaces, equipment, clothing, etc
Children raised in super clean houses tend to have compromised immune systems this is known as the
hyperclean hypothesis
This chemical reacts with functional groups of DNA and proteins and blocks DNA replication and enzyme action
Ethylene Oxide (gas)
Uses of Ethylene Oxide include
sterilization/diinfection of plastics and delicate instruments

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