Lecture 13 Flashcards
Sterilization
all microorganisms dead (even endospores)
Pasteurization
reduce the number of microbes
Disinfection
most pathogens dead
Decontamination
reduce pathogens to a “safe” level (disease causing)
Sanitization
reduce all organisms to a “safe” level (includes even non-disease causing)
Know three bacterial structures
Endospores
Protist Cyst
Enveloped Viruses
Know one bacterial or eukaryotic structure that are hard to kill
Endospore
Know why naked viruses are harder to kill than enveloped viruses
resistant to drying and disinfectants, protein shell is very tough
What is water activity?
moisture content = vapor pressure of material / vapor pressure above pure water
What organisms survive best at low water activity
fungi like xerophilic fungi
What is decimal reduction time?
amount of time required to decrease by 1 order of magnitude (1 tenfold reduction)
How does decimal reduction time depend on the organism that is being killed?
more organisms (or biofilms) = more disinfectant time
How does decimal reduction time depend on the surface being decontaminated?
heat-sensitive, moisture-sensitive shouldn’t be sprayed
bleach cannot be used on metal
How does decimal reduction time depend on the decontaminant used?
combined procedures = less time
Critical medical instrument
direct contact with body tissue
Semicritical medical instrument
contact with mucous membranes
Noncritical medical instrument
external contact only
Why is moist heat more effect as a decontaminant than dry heat?
it is much more penetrating than dry heat, because of the high heat capacity of water
How does an autoclave function?
uses steam and pressure to reach a temperature of 121, has steam supply and exhaust pipe
What are three methods that are used to pasteurize liquids?
- Batch Pasteurization (63C for 30 minutes)
- Flash Pasteurization (72C for 15 seconds)
- Ultra pasteurization (150C for 1 sec)
What is the difference between a membrane filter and a depth (HEPA) filter?
Membrane filter: 0.2um pore (virus pass through)
HEPA filter: uses filter matrix
What types of radiation can be used to kill bacteria? What cannot?
Ionizing radiation (X-rays, gamma rays) and UV rays can kill bacteria
microwaves cannot
What three bacterial structures that can serve as targets for chemical disinfectants.
- Cytoplasmic membrane
- Protein
- DNA
What is the mode of action for alcohol?
damage lipid membranes and denature proteins
What is the mode of action for aldehydes?
crosslink and rigidify proteins
What is the mode of action for chlorhexidine?
makes membranes leaky
What is the mode of action for ethylene oxide?
gaseous sterilant; oxidize DNA
What is the mode of action for halogens?
oxidize proteins
What is the mode of action for heavy metals?
derivatize cysteine to prevent protein disulfide bonds
What is the mode of action for peroxide?
oxidize proteins
What is the mode of action for phenols?
dissolve lipid membranes
What is the mode of action for quaternary amines?
dissolve membranes
What happened in Milwaukee in 1993?
water treatment plant had bad filters, crypto cysts caused people to get diarrhea
How was the overuse of triclosan led to increased bacterial resistance?
triclosan was acting like an antibiotic, so when they adapted they became resistant to triclosan and other antibiotics
