Microbiology Chapter 5
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removal/destruction of all microorganisms and virueses in/on a product
An item free of microbes, including endospores and viruses, does NOT consider prions
elimination of most or all pathogens on/in a material
antimicrobial chemicals used to disinfect inanimate objects
another way to describe disinfectants
to kill bactria
Antimicrobial chemicals non-toxic enough to be used on skin/body tissue
heat treatment used on foods and inanimate objects to destroy pathogens and reduce spoiling agents
- used to reduce the number of bacterial agents
- ex. washing
process that reduces microbial population to an acceptable health standard
delaying food spoilage or other perishables
chemicals preservatives used in preservation that inhibit bacterial growth
What are healthcare associated infections?
Infections caused within a hospital
Why are patients susceptible to infections?
- Usually in a weakened state
- undergone invasive surgery
- pathogens can occur in high concentrations in a hospital setting
Which bacteria create endospores?
Bacillus and Clostridium
How do you kill Protozoan cysts and Oocsts?
Why are Mycobacterium Species difficult to kill?
Their waxy cell walls make them resitant to most chemicals, therefore more toxic chemicals must be used
How do you kill Pseudomonas Species?
resistant to some disinfectants, can cause serious healthcare associated infections
What is a D Value?
The time required to kill 90% of bacterial population
What are Critical Instruments?
- Instruments that come into direct contact with body tissue
- ex. Scalpel
What are semicritical instruments?
- come into contact with mucous membrane, but do not penetrate
- ex. endoscopic tube
What are non-critical instruments?
- come into contact with unbroken skin
- ex. stethoscopes
What are examples of moist heat?
- Pressurized Steam
- Commercial Canning Process
What is required to kill microbes via boiling
100 C at sea level destroys most microbes except endospores.
What is required to kill microbes via Pasteurization?
- High-temperature-short-time (HTST)
- Ultra-high temperature (UHT)
What is needed for Pressurized Steam
- Used for surgical equiptment
How does dry heat kill microbes?
- not as efficient as Moist Heat
- needs to be hotter and longer
How does filtration work to remove organisms from Fluids
Membrane Filters/Microfilters have microscopic pores to allow for passage of luid but not particles
How does filtration work to remove organisms from the Air
- High-Efficiency- particulate Air Filters (HEPA)
- removes airboen particles >/3um
What are the three different types of radiation?
Ionizing, ultraviolet, microwaves
How does Ionizing Radiation destroy/remove microbes?
removes electrons from atoms therefore destroying the cell's DNA and damaging cytoplasmic membrane
How does Ultraviolet radiation destroy/remove microbes?
destroys actively multiplying bacteria, not endospores
How do Microwaves destroy/remove microbes?
Does not destroy microbes, the heat generated does
How does High Pressure destroy/remove microbes?
- Denatures proteins and altering cell permeability
- Doesn't affect food taste or color
How are Germicidal Chemicals grouped?
By their potency
What are the benefits and risks of germicidal chemicals?
- Less reliant than heat
- useful for treating heat resistant material
What are the four groupings of Germicidal Chemicals?
- High-level Disinfectants
- Intermediate-level disinfectants
- Low Level disinfectants
- Destroy all microorganisms
- treat heat-sensitive instruments
Describe High-level disinfectants
- Destroy all viruses and vegetative microorganisms
- do not reliably kill endospores
Describe eIntermediate-level disinfectants
- destroy all vegetative bacteria
- do not reliabily kill endospores
Describe low level disinfectants
Destroy fungi, vegetative bacteria except mycobacteria and enveloped viruses
What are points to consider when selecting appropriate germicidal chemicals?
- Activity in the presence of organic matter
- compatibility w. treated material
- Cost and Availability
- Storage and Stability
- Environmental Risk
Why should toxicity be considered?
Are the side effects worth the disinfecting qualities
Why should activity in the presence of organic matter be considered when selective a germicidal chemical?
Some germicides are inactivated by organic matter
Why should compatibility with treated material be considered when choosing a germicidal chemical?
ex. liquids cannot be used on electrical equiptment
Why should storage and Stability be considered when choosing a germicidal chemical
some germicides require dilution
Why should environmental risk be considered when selecting a germicidal chemical?
Some chemicals may need to be neutralized after use
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