chapter 9 Flashcards
use of heat to kill pathogens that cause spoilage of food products without causing damage to the product itself
pasteurization
the removal and destruction of all microbes in or on an object which include viruses and endospores
sterilization
procedure that is free of contamination by pathogens
aseptic
removal of microbes by mechanical means
degerming
agents that inhibit the growth of a microorganism
static
agents that kill a microorganism
cidal
kills bacteria
bactericide
prevents bacteria from reproducing
bacteriostatic
an antimicrobial used to kill microorganisms on non living surfaces or inanimate objects, more concentrated
disinfectant
an antimicrobial used to kill microorganisms on skin or body tissues
antiseptic
remove microbes from a public space to health standards set by the government, level can differ based on location
sanitization
a chemical that kills or suppresses growth of microbes
antimicrobial agent
four ways antimicrobial agents work
- alter cell wall
- alter cell membrane
- damage proteins
- damage to nucleic acids
how can antimicrobial agent alter cell wall
place in a hypotonic solution, water is higher outside the cell wall, it will cause water to flow into bacteria cell and it will burst
function of cell membrane
controls passage of chemicals entering and exiting the cell
what happens if we damage cell membrane
vital chemicals will leak out of the cell which results in immediate death within seconds
how do proteins function
the act as enzymes in metabolism and structural components of organelles and cells
what does protein function depend on
3D shape
DNA and mRNA are involved in
gene expression
what makes the ideal antimicrobial agent
- inexpensive
- fast acting
- long shelf life for storage
- selectively kills microbes while harmless to humans and environment
list microbes from most resistant (hardest to kill) to most susceptible
prions
bacterial endospores
mycobacteria
cysts of protozoa
active-stage protozoa
most gram - bacteria
fungi
nonenveloped viruses
most gram + bacteria
enveloped bacteria
have the ability to transfer their folding to other variants of that protein, they cause fatal neurodegenerative diseases that can be transmitted, indestructible
prion
surrounded by a lipid membrane but makes them easier to destroy through sterilization
enveloped viruses
what virus lacks a lipid membrane
noneveveloped viruses
If the temperature is too high what will happen
it will degrade or breakdown the chemical disinfectants or antiseptics
how do chemical disinfectants work best
they work poor in cold environments as chemicals move and react slower
the work well in warm environments as chemicals move and react faster at high temps
a chemical agent that kills pathogenic microorganisms
germicide
germicides used on invasive medical equipment needed on implants, catheters, lung machines
high-level
germicides that kill fungal spores, viruses, and pathogenic bacteria but not endospores, come in contact with the mucous membrane
intermediate-level
germicides that eliminate vegetative bacteria, fungi, protozoa, and some viruses, only equipment that comes in contact with the skin
low-level
why is heat an effective method in killing microbial life
it uses all four strategies to kill microbes
-denatures proteins
-disrupts integrity of the membrane and cell wall
-unwinds double strands of DNA
lowest temp that kills all cells in broth in 10 min
thermal death point
time to sterilize volume of liquid at a set temp
thermal death time
is moist or dry heat more effective in killing microorganism
moist heat
why is moist heat more effective
heated water has more heat/energy to destroy bacteria when it collides with it, it also absorbs the cell better because it has more water content
boiling time depends on what
elevation
higher elevation: boils quicker but has less energy so more time to kill microbes
pressure applied to boiling water prevents steam from escaping
autoclaving
standard autoclave conditions
121C 15psi 15 min
used to kill microbes in milk, ice cream, yogurt, wines, beers, and fruit juices
pasteurization
used for materials that cannot be sterilized with moist heat because they would breakdown or become damaged in the steam
dry heat
how does dry heat kill bacteria
denatures proteins and oxidizes structural biochemicals and enzymes
what is the ultimate means of sterilization
complete incineration
what is most effective way of freezing
slow freezing
what inhibits growth due to removal of water
dessication
what is used for long-term preservation of microbial cultures
lyophilization
method used to physically remove microorganisms from a liquid
filtration
adding high concentrations of sugar or salt to food will inhibit growth of microbe
osmotic pressure
the solute concentration is higher outside the cell than inside, water travels from high to low, cell shrinks
hypertonic solution
short wavelengths =
greater energy and more penetration
wavelengths that are less than 1 nm
ionizing radiation
which is non-ionizing radiation
ultraviolet rays
largest wavelength are very effective at surface killing but do not penetrate cells so it is the weakest
electron beams
can penetrate the cells very well but require too much time to be practical for killing microbes
x-rays
shortest wavelength penetrate cells but require several hours to kill microbes
gamma rays
wavelengths are greater than 1 nm
non-ionizing radiation
does not penetrate cells but is suitable for disinfecting air, fluids and surface of objects
uv light
most common chemical method of microbial control
phenols and phenolics
- denatures proteins and disrupts cell membranes
- remain active for a long time
- commonly used in health care, labs, and homes
phenols and phenolics
- denature proteins and disrupt cytoplasmic membranes
- more effective than soap in removing bacteria
- evaporates rapidly
- not effective against endospores
alcohols
why is alcohol advantageous and disadvantageous
long enough to kill microbes but not long enough to damage cells of skin
- damages enzymes through oxidation
- gain an electron when they react with another molecule
- one electron short of filling their last electron shell
halogens
examples of halogen
iodine tablets or topical use
kill microbes by oxidizing enzymes, damages their structure and disrupt their function
oxidizing agents
common oxidizing agents
peroxides, ozone, and peracetic acid
an effect sporocide used to sterilize medical equipment
peracetic acid
destroys endospores
sporocide
what is used to sterilize drinking water
ozone treatment
surface active chemicals that reduce surface tension of solvents to make them more effective at dissolving solutes
surfactants
specifically target bacteria cells, work by disrupting cell membrane, used commonly in disinfectant wipes
quatenary ammonium compounds
excellent for denaturing proteins, bacteriostatic and fungistatic
heavy metals
controls algal growth
copper
can remove prions on medical instruments
prionzyme
