Chapter 4: Microbial Growth Control Flashcards
sepsis
bacterial contamination
example of sepsis
severe infection
asepsis
absence of significant contamination (normal microbiota)
aseptic surgery techniques prevent
microbial contaminatoin of wounds
sterilization
removing and destroying all microbial life
why is sterilization not always effective
come bacteria can resist sterilization via endospore
commercial sterilization
killing C. botulinum endospores from canned goods
commercial sterilization focuses on
time, temperature, presure
disinfection
destroying harmful microorganisms
antisepsis
destroying harmful microorganisms from living tissue
degerming
mechanical removal of microbes from limited area
sanitization
lowering mocrobial counts on eating utensils to safe levels
biocide (germicide)
treatments that kill microbes
biocide used for
BSL3 or 4 to fight back against biowarfare
bacteriostasis
inhibiting microbes (not killing them)
methods of bacteriostasis
fridge, oven, microwave, freezing
most critical part of exponential death rate
first minute
plotting exponential death rate logarithmically results in
straight line
effectiveness of treatment depends on
number of microbes
environment (organic matter, temp, biofilms)
time of exposure
microbial characteristics
the higher the population, the
longer it will take to kill
actions of microbial control agents
alteration of membrane permeability
damage to proteins
damage to nucleic acids
what denatures enzymes
heat
thermal death point (TDP)
lowest temp at which all cells in liquid culture are killed in 10 minutes
thermal death time (TDT)
minimal time to kill all bacteria in liquid culture at a particular temperature
decimal reduction time (DRT)
minutes to kill 90% of population at a given temperature
what denature proteins
moist heat
3 exampless of moist heat
boiling, free flowing system, autoclave
autoclave
steam under pressure; 121 degrees C at 15psi for 15 min
in order for an autoclave to kill all organisms and endospores, steam must
contact all surface of the item - larger items require longer time
what iss used to indicate sterility
test strips
pasteurization reduces
spoilage organisms and pathogens
pasteurization treatments
63 degrees C for 30 min
HTST
UHT
high temp short time
72 degrees C for 15 seconds
ultra high temp
140 degrees C for 4 seconds
what type of organisms survive pasteurization
thermoduric organisms
dry heat sterilization kills by
oxidation
3 examples of dry heat
flaming, incineration, hot-air sterilization
filtration
passage of substance through screen-like material
filtration used for
heat-sensitive materials
HEPA filters
high-efficiency particulate air filters remove microbes > 0.3 micrometers (some viruses)
treating microbes with low temp has
bacteriostatic effect
3 examples of low temp treatment
fridge, deep freeze, lyophilization
what denatures proteins other than heat
high pressure
desiccation
absence of water prevents metabolism
osmotic pressure uses
salts/sugars to create hypertonic environment to cause plasmolysis
ionizing radiation
ionizes water to creat reactive hydroxyl radicals