Chapter 7 Flashcards
Sepsis
microbial contamination
Asepsis
absence of significant contamination
biocide/germicide
kills microbes
bacteriostasis
inhibits growth of microbes, but doesn’t kill them
After the removal of a bacteriostatic agent, microbial growth _______________.
can resume
What are three ways that control agents affect microbial cells?
- Alter membrane permeability 2. Damage proteins 3. Damage nucleic acids
4 Factors that Influence the Effectiveness of Control Treatment
- Number of microbes 2. Amount of time exposed to treatment 3. Environment 4. Microbial Characteristics
Why does the number of microbes affect the effective on control treatment?
takes longer to kill them all
Examples of Environmental Influences on the effectiveness of control treatments:
organic matter, temperature, biofilms
What microbial characteristics makes it harder to kill microbes?
Being mycobateria, or having endospores
Sterilization
complete elimination of all living organisms, including endospores
Disinfection
Killing or removal of pathogens from inanimate objects; typically does not kill spores
Antisepsis
Killing or removal of pathogens from living tissues; typically does not kill spores
Sanitation
reduction of microbes on eating and drinking utensils to safe levels
4 Types of Physical Control
high temperature, low temperature, filtration, radiation
_____ heat is more effective than ___ heat
Moist; dry
Killing spores and thermophiles usually requires _____ heat and _____ temperature.
high; high
How does an autoclave kill microbes?
Denatures proteins
Commercial Sterilization
enough heat to kill Clostridium botulinum endospores; not completely sterile
Botulism
Clostridium botulinum; rare but serious paralytic disease caused by a nerve toxin
Pasteurization
reduces spoilage organisms and pathogens
What is a common method of pasteurization in the US?
HTST (High Temperature Short Time) 72C for 15 sec
What is a common method of pasteurization in Europe?
UHT (Ultra High Temperature) 140C for
Are these all equivalent treatments?
63C for 30 min
72C for 15 sec
90C for 0.5 sec
Yes
Ultra-High Pasteurization
138 C for at least 2 sec; done before or after packaging; extended shelf life under refrigerated conditions
3 Types of Dry Heat Sterilization
Flaming, Incineration, Hot-air sterilization
Low temperatures ______ _______ and preserve strains -stasis
slow down growth
Your refrigerator is what temp?
4-8C
Lyophilization
freeze drying
membrane filtration
physical removal of microbes from solutions
2 common pore sizes for filtration:
0.22 micrometers and 0.45 micrometers
UV light has poor penetration. It is used for _______ sterilization
surface
Microwaves kill by heat, but _____ antimicrobial
aren’t
High pressure ___________ __________
denatures proteins
Dessication
prevents metabolism by removing water
Osmotic pressure causes _________
plasmolysis
Phenols and Phenolics cause ________. In other words, they disrupt the _______ _________.
leakage; plasma membrane
phenols are useful against _______________
mycobacteria
Iodine
alters protein synthesis and membranes
Iodine is used for:
skin disinfection
Chlorine
oxidizing agents that inhibit enzyme activity
Chlorine is used for:
disinfection of water
3 main parts to ethanol
- denatures proteins
- dissolves lipids
- requires water
Heavy metals have oligodynamic properties meaning:
They denature proteins
Aldehydes ________ proteins by ____-_________ with functional groups. They damage nucleic acids.
inactivate; cross-linking
2 Uses of Formaldehyde
- Disinfectant that kills bacteria and fungi
2. Tissue preservative
Oxidizing Agents like perozygens:
denature proteins and lipids
Hydrogen peroxide is good for ______________ of contaminated surfaces but not a good __________ for wounds.
disinfection; antiseptic
What’s used to preserve meats like hot dogs?
Sodium nitrite
What are organic acids used for?
the control of molds and bacteria in foods and cosmetics
What two antibiotics prevent the spoilage of cheese?
nisin and natamycin
What are the most resistant to chemical biocides?
prions
What are the least resistant to chemical biocides?
viruses with lipid envelopes