Chapter 13 Microbiology UTA Tholen Verified Answers
Main Goals of Controlling Microbial Growth - Reduce microbial load to minimize infection and contamination.
Definitions of Key Terms - Sterilization: Complete removal and killing of ALL microbes from inanimate objects (fomites) or
organisms....
- Reduce microbial load to minimize infection and contamination.
Definitions of Key Terms
- Sterilization: Complete removal and killing of ALL microbes from inanimate objects (fomites) or
organisms.
- Disinfection: Inactivation or killing of microbes on fomites, not necessarily complete sterilization.
- Sanitization: Decrease of microbial load (the number of microbes) to safe levels.
Biological Safety Levels (BSL)
- Levels of cleanliness assigned to laboratories established by organizations like the CDC, NIH, and WHO.
# BSL-1
- Description: Microbes that pose minimal risk and are not known to cause disease in healthy hosts.
- Features: Sink for handwashing, laboratory doors for containment.
- Example: Non-pathogenic strains of Escherichia coli.
# BSL-2
- Description: Microbes associated with diseases that pose moderate risk.
- Features: BSL-1 features plus personal protective equipment (PPE), self-closing doors, eyewash station,
and autoclave.
- Example: Staphylococcus aureus.
# BSL-3
- Description: Microbes that cause lethal diseases transmitted through respiratory routes.
- Features: BSL-2 features plus respirators, biological safety cabinets, hands-free sinks, and double-door
entrances.
, - Example: Mycobacterium tuberculosis.
# BSL-4
- Description: Dangerous and exotic microbes with high risk of aerosol-transmitted infections, often fatal
without treatment.
- Features: BSL-3 features plus full biohazard suits, showers on exit, and dedicated air supply.
- Example: Ebola and Marburg viruses.
Levels of Cleanliness in Clinical Settings
1. Critical: Must be sterile; items contact sterile tissue (e.g., surgical instruments).
2. Semicritical: Do not require high-level sterilization; items might contact sterile tissue (e.g.,
gastrointestinal scopes).
3. Noncritical: Do not require sterilization; items do not penetrate tissue (e.g., stethoscopes).
Methods of Sterilization and Disinfection
- Sterilization Methods: Heat, pressure, filtration, or chemical agents (sterilants).
- Aseptic Technique: Methods used to prevent contamination of sterile environments.
- Antiseptic: Kills microbes but does not harm the host tissue.
- Disinfectants: Do not kill endospores; examples include hydrogen peroxide and rubbing alcohol.
- Sanitization: Mechanical methods (e.g., hand washing, wiping surfaces) often combined with
disinfectants for effective microbial reduction.
Microbial Control Terminology
- -cides: Agents that kill; examples include bactericidal, virucidal, fungicidal.
- -static: Agents that inhibit growth; examples include bacteriostatic, viristatic, fungistatic.
Concepts Related to Microbial Death
- Microbial Death Curve: A measure of the percentage of microbial kill.
- Decimal Reduction Time (DRT): The time required to kill 90% (1 log reduction) of a microbial
population.
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