Ch. 11: physical and chemical control of microbes Flashcards
Sterilization
-process that completely removes/destroys all viable microorganisms, including viruses from object/habitat
~kills all life, destroys all viral particles; no trace left
~mostly done thru heat, but also some chemicals can do
fungicide
a chemical that can kill fungal spores, hyphae, and yeast
bacteriostatic
any process or agent that inhibits bacterial growth
disinfection/disinfectants
destruction of vegetative/pathogenic nonsporulating microbes or their toxins, usually on inanimate surfaces,
disinfectant=chemical used for this purpose
killing many microbes; minimize/reduce# of microbes
Sepsis
*presence of pathogenic organisms or their toxins in blood
[when microbes are in the bloodstream]
Asepsis
killing many microbes; minimize/reduce# of microbes
Sanitizer
physically removes microbes; does not necessarily kill them
Mode of action
How does it work to kill microbes?
Surfactants
an agent that reduces surface tension and forms a water-soluble interface
-derives from -surface-active agent
ex) detergent, soap, wetting agents, dispersing agents
Autoclave
a sterilization chamber that allows use of steam under pressure to sterilize materials
most common autoclave temperature/pressure combination is 121 C and 15 PSI.
Pasteurize
heat treatment of perishable fluids like milk, juice, or wine to destroy heat-sensitive vegetative cells, followed by rapid chilling to inhibit growth of survivors and germination of spores
-prevents infection & spoilage
desiccation
to dry thoroughly/ preserve by drying
lyophilization
freeze-drying; separation of a dissolved liquid from solvent by freezing solution and evacuating solvent under vacuum
-means of preserving viability of cultures
ionizing radiation
electromagnetic waves (x-ray or gamma) or high-speed electrons that cause dislodgement of electrons on target molecules, which creates ions; can break covalent bonds;
MOA=lot of energy= can slice thru DNA = large scale DNA mutations [foods like raspberries can be treated with radiation]
~if DNA bonds broken, can kill / greatly impact cell
-can penetrate liquids
-used by food industry, requires labeling
non-ionizing radiation
A type of low-energy radiation that does not have enough energy to remove an electron (negative particle) from an atom or molecule.
– creating new, unusual covalent bonds between thymines and cytosines & produces deletion mutations on DNA
~visible, infrared, and ultraviolet light; microwaves; radio waves; and radiofrequency energy from cell phones.
halogens
[common examples, MOA]
a group of related chemicals with antimicrobial applications
-most common halogens used in disinfectants/antiseptics = chlorine & iodine
[chemical group] anything in group 7 [[or group 17 depending on the table]] of the periodic table; of these, mostly use chloride and iodine (others are rare/dangerous/harmful)
Found in ⅓ of all disinfectants today
MOA= they break disulfide bonds in proteins; proteins fold over on themselves and a covalent bond can form between 2 sulfur atoms in amino acid cysteine
cross-linking
formation of covalent bonds which hold portions of several polymer chains together
what would happen to microbial contaminants in the food you store in your freezer?
they remain dormant, or may grow at a slow rate
when you lay out in the sun, what happens to your cells?
they gain small point mutations because of the thymine dimers
The process that destroys or removes all microorganisms and microbial forms including bacterial endospores is
sterilization.
The use of a physical or chemical process to destroy most vegetative pathogens on inanimate objects is
disinfection.
true or false: A microorganism that loses its ability to be motile could be considered dead.
false
Microbiological contaminants are best described as
unwanted microbes present on or in a substance.
The process of using a cleansing technique to mechanically remove and reduce microorganisms and debris to safe levels is
sanitization.
Moist heat damages microorganisms by
denaturing and coagulating cellular proteins.
True or false: Most microbial contaminants of food are killed at freezing temperatures.
False
Disinfection of beverages, such as apple juice, milk, and wine, is optimally achieved by
pasteurization.
Electrons are ejected from atoms in cells when organisms are exposed to
gamma rays and X-rays.
Food irradiation can lead to-
a longer shelf life for the irradiated food.
Which of the following would be the most toxic to use on treating human skin?
Phenol
Hydrogen peroxide
Quats
Bleach
Phenol
Filtration is an effective method to:
remove microbes from air and liquids.
Alcohols are more effective at inactivating ___________ viruses than ________ viruses.
Alcohols are more effective at inactivating enveloped viruses than naked viruses.
The sterilizing gas used in a special chamber is
ethylene oxide.
The presence of organic matter such as saliva and pus can interfere with:
the actions of disinfectants.
Alcohol targets :
protein coagulation
Chlorine dioxide and ethylene oxide are:
gaseous sterilants.
Ethylene oxide is
sporicidal.
-highly toxic, explosive
-slow acting
-carcinogenic
-used on plastics, medical equipment
-requires 1-3 hours exposure inside a special chamber
Which of the following would be the best option to treat skin in order to minimize contamination during a blood draw?
iodine
triclosan
bleach
ethylene oxide
iodine
Which of the following is NOT a carcinogen?
gamma radiation
UV light
hydrogen peroxide
formaldehyde
hydrogen peroxide
Which of the following works by breaking disulfide bonds in proteins?
bleach
hydrogen peroxide
silver nitrate
UV light
bleach
Do chlorine compounds remain stable and effective in the presence of excess organic matter?
No
Which microbial forms have the highest resistance to physical and chemical controls?
bacterial endospores
Prions
Sterilizing conditions in a steam autoclave would be
121°C at 15 psi for 15 minutes.
Which control method would not be a suitable choice for killing Mycobacteria inside a capped culture tube?
ultraviolet (germicidal) light
What are the most highly resistant microbes on the planet?
bacterial endospores/ prions
What are the least and the moderately resistant microbes on the planet?
Least resistant- vegetative microbes/bacterial cells/fungi
Moderate resistance- some viruses like HIV can’t exist out very long/ protozoan cysts/ fungal spores
word that ends with -icide
to kill
ex) germocide
word that ends with -static
inhibits growth
What does cold do to microorganisms?
make microbes dormant; cold storage; keep them from growing out of control; # microbes not increasing.
-could be used in research labs for later use.
What does freeze-drying do to microorganisms?
[-80 C ] - dry it with a vacuum (remove all water) metabolism comes to a stand still; cells not killed since it is frozen [dormant state]
tincture
agent diluted in any amount of alcohol
aqueous
agent diluted in water
What do we want out of microbial agents?
~work quickly in low concentrations
~should be soluble in a solvent and stable
~should work against lots of fungi but not kill our cells
~it should penetrate porous surfaces like marbles;
~be nonstaining and non-corrosive
~should sensitize and deodorize [get rid of stinky molecules]
~should be cheap and readily available
~~~glutaraldehyde & hydrogen peroxide fit a lot of these and are good
Hypochlorite molecular structure
Ocl
Draw phenol
Draw ethanol
draw isopropanol
Draw hydrogen peroxide
what concentration of hydrogen peroxide do we purchase from the store?
3%
describe the structure & MOA of detergents
structure- amphipathic [hydrophobic and hydrophilic region]
MOA: disrupt the cell membrane
are all microbes bad for us?
No
only human pathogenic microbes are bad for us
Draw glutaraldehyde
Draw formaldehyde
problems with using heavy metals as a microbicide
-can be harmful to human health, such as mercury, lead
-allergic reactions are common to these
-biological fluids can impact activity [fecal, saliva…]
-microbes evolved resistance to heavy metals
-can be toxic, cause allergies, not widely used in health care
Glutaraldehyde VS Formaldehyde
They polymerize & cross-link; alters molecule, change cell function
*Glutaraldehyde: [binds to proteins preferentially]; less toxic; much less stable
*Formaldehyde: [binds to nucleic acids/DNA preferentially; in water called formalin; used as embalming fluid; it is a possible carcinogen bc changes DNA structure
in water, formaldehyde is called:
formalin
draw ethylene oxide [may not be on exam…]
draw chlorine dioxide [may not be on exam…]
which heavy metals work as microbicides that are not as harmful to humans?
gold, silver, copper
-in some iv lines, catheters, bandaids, clothing (lululemon), plates, etc…
microbes can evolve resistance to:
heavy metals
Phenol MOA:
*disrupts cell walls and membranes + precipitates proteins
-kills everything but spores usually; toxic to humans; can cause chemical burns; works well with interfering organic matter
How do antimicrobial agents target microbes (what are the 5 modes of action of antimicrobial agents)?
- Attacking cell wall; microbe could lyse= cell death
- Damage cell membrane- uncontrolled movement in and out of cell = loss of DNA molecules or waste entry [ surfactants are good at this ]
- Target transcription & translation
- Targeting DNA replication/nucleotide formation
- Affecting protein function [primarily destroying enzymes, some or all= proteins denature = no longer function]
define microbial death:
Microbe will not divide under its optimal conditions (medium, temperature, time duration…)
Alcohol works best at______concentration
70% = optimal %
(60% wont work, 80% will turn cells dormant and not kill them)
what factors influence the rate of microbial death?
*# of microbes
*nature of microorganisms [endospore/vegetative, etc…]
*environmental conditions [temp, pH]
*concentration of antimicrobial agent
*mode of action
How does moist heat differ from dry heat in temperature and mode of action? Give examples of each.
Moist heat- AKA steam [turns liquid water into gas/steam] 100-120 C, if pressure is higher, can be up to 120 C; will coagulate [will clump proteins together with help of water molecules] and denature proteins
~~~moist heat is more effective than dry!
-Pasteurization, Boiling water;-Autoclaves:
Dry heat- using a lot hotter temperatures 100-1000s C… sterilize material
—Incineration- flame (sticking loop in bunsen burner)… MOA - removes water, turns material to ash.; water is needed for metabolism; denatures proteins > everything becomes ash. Used in hospitals; treat heat-tolerant glass/metal.
—Dry ovens- some plastics… 160-200 C or so… leave them in for hours-overnight. Use this for pipettes (Autoclaves>dry oven) to dry and keep sterile.
spices can be treated with :
gamma rays
ultraviolet light
~less energy than gamma/x-ray
~thymine dimers- small point mutations if cells lay in sun
~UV light can treat food prep spaces/cafeterias, water treatment in some cities; does not go thru solid materials like plastic/glass. Goes thru liquid material minimally. Toothbrush chamber.
When is filtration used to sterilize a liquid?
-when you have liquids that cannot withstand heat
ex) vaccines, blood transfusions, IV fluids, enzymes, growth medium for microbes, milk, beer, wine to keep their flavor
-water purification (pool), air purifier
iodine
2 types
MOA?
- free iodine = iodine
- iodophor = iodine complexed with neutral polymers, allowing for slow release of iodine into solution = functions longer, more effective
-can kill all microbes with proper time
-used before surgery, burned skin, blood donations…, instruments, treats water
[MOA= breaking disulfide bonds]
chlorhexidine
[structure, MOA]
-chlorine and 2 phenolic rings
-MOA: Denatures proteins and disrupts cell membranes;
-milder, less toxic than phenol/not absorbed into skin
ethanol vs isopropanol
MOA
same MOA: alcohols of over 50% concentration dissolve membrane lipids and denature proteins by coagulation [protein denaturation with water]
===higher than 80% alcohol will not allow for this bc needs more water and lead to dehydration not death
—does not kill endospores, works with enveloped viral particles, not as well for naked viruses [destroys influenza, not all cold viruses]
ethanol- used in lab settings; germicidal; evaporates quickly; needs to be on object for long time; less germicidal, expensive, but less toxic to respiratory system
isopropanol- used at home/ hospital; kills microbes more readily, cheaper, more germicidal, more irritating to respiratory lining
MOA of hydrogen peroxide
forms hydroxyl free radicals
oxidizes other molecules in the cell, forming radicals; does this with any molecule (will attack components like DNA, RNA, proteins, cell membranes…)
toxic to endospores at high concentrations
Quats
[quaternary ammonium compounds]
MOA/define
-type of detergent, cationic positive charged
MOA: disrupts cell membrane, can kill microbes + physically remove them from skin
MOA of soaps
lifting and suspending oil, dirt, and debris from hands so they can be rinsed down the drain
Chlorine dioxide is used for-
-effective sterilizer, including endospores
-treats water, medical waste, and sterilized air after anthrax attacks
-useful/effective for large spaces or objects
what is the MOA of bleach?
breaking disulfide bonds (reacts with amino acids)
