ch 9 Flashcards
know all terminology
bacteriostatic: inhibition of microbes
sepsis: bacterial contamination
degermination/Antisepsis: destroying vegetative microbes from tissue
bacteriocidal: killing microbes
decontamination/sanitization: mechanical removal of microbes
asepsis: abscence of sig contamination
sterilization: destroying all microbial life
disinfection: destroying vegetative microbes from objects
sanitization: lowering micobes on spoons, forks, etc.
Describe the death rate of microbes when exposed to an antimicrobial.
How does moist heat kill? Used for?
Moist heat kills by denaturing proteins, sterilization, and disinfection.
Examples of moist heat is steam under pressure, boiling water, and pasteurization.
What is pasteurization? Used for?
Pasteurization is intended to reduce spoilage organisms and pathogens in food products.
This process is NOT a sterilization process. Milk, beer, other beverages, and liquid egg products are some examples of items that are pasteurized.
How does dry heat kill?
Dry heat denatures proteins, oxidizes, sterilization.
Compare/contrast moist heat/dry heat.
Moist and dry heat denature proteins.
Dry heat (baking) requires longer exposures than moist heat for sterilization.
Dry heat also oxidizes cell constituents.
What is filtration? Why is it used?
Filtration is used to remove microbes based on size-exclusion principle. It is used with liquids and air.
ex. HEPA filtration is used for furnace filters and vacuum filters
Know other physical methods of control such as: low temp, increased pressure, desiccation.
low temp: inhibits growth by slowing down reaction by making liquid water unavailable for cellular reactions
ex. refrigeration
desiccation (drying out): prevents metabolism
ex. no water available
Know the 2 forms of radiation and how each kills/causes damage.
ionizing radiation: sterilizing, makes a -OH which damages DNA
ex. x-ray
nonionizing radiation: disinfection, damages DNA using thymine-dimers
ex. UV light
Know the factors that may affect the effectiveness of antimicrobials.
- number of microbes present
denser populations may not all receive equal exposure to agent decreasing its effectiveness
- environmental factors
agents may bind to organic matter in environment instead of the organic matter of the cell to decrease agent effectiveness
Cool temperature may SLOW DOWN diffusion of agent from source to decrease agent effectiveness
Low or high pH may inactive the agent environment
- Concentration or intensity of treatment
Low concentration or intensity MAY NOT be able to reach all organisms equally
- Time of exposure:
It takes time for agents to diffuse equally to each organism, decreasing effectiveness of agent - Microbe characteristics:
Endospores, mycolic acids are very resistant to chemical exposure and promote microbe survival
Often agent CANNOT get into cells with these structures
Know the 4 main targets of antimicrobials.
Cell wall:
Chemical agents damage the cell wall by blocking its synthesis or by digesting the cell wall.
Cytoplasmic membrane: Chemical agents disrupt the lipid layer of the membrane and it causes the membrane to open up and allow damaging chemicals to enter the cell and important ions exit.
Cellular synthesis: Chemical agents interrupt the ribosomes and stop protein production needed for growth, metabolism, and reproduction. Other chemical agents can also change the genetic code (DNA synthesis) and cause mutation.
Proteins:
Chemical agents can cause the protein bonds to break which will result in the destruction of the protein structure. Other chemical agents may attach to the active site of the protein and prohibit the interaction with its chemical substrate.
Know general uses of phenols , halogens, alcohols, heavy metals, quats,
aldehydes, ethyl oxide.
phenols:
disrupts the plasma membrane
ex. triclosan
halogens:
oxidizes cytochromes in membrane to reduce ATP production
ex. iodine (Povidone/Betadine)
alcohols:
dissolves lipids (enveloped viruses) and denatures proteins *except endospores
ex. ethanol
heavy metals:
denatures proteins, sometimes precipitating them from solution
ex. Ag-silver
quats:
dissolves plasma membrane and denatures proteins
ex. Benzalkonium chloride (bactine)
aldehydes:
combines with nucleic acids to denature proteins
ex. formaldehyde
ethyl oxide:
combines with proteins to inactivate them
ex. ethyl oxide
Know the groups of organisms we have discussed in terms of most resistant to least resistant
MOST RESISTANT
prions
endospores of bacteria
mycobacteria
cysts of protozoa
vegetative protozoa
gram-neg bacteria
fungi
viruses without envelopes
gram-pos bacteria
viruses with lipid envelopes
LEAST RESISTANT
