Control of Microbial Growth Flashcards
How do aldehydes work and what is an example?
alkylating groups in proteins and other important cellular molecules, formeldyhide.
What pore sizes would be best for filtering solutions known to contain bacteria but not viruses?
.22 um
define aseptic technique
techniques that reduce significant contamination
What macromolecules are affected by radiation?
DNA
Define disinfection
removal of non endopsore forming pathogens from a non living surface using physical or chemical methods
Define commercial sterilization
destruction of all pathogenic endospores but not necessarily all microbes
define sanitization
reduction of microbes to a safe level to meet public health standards
How do heavy metals work and what is an example?
Combine with amino acids that contain sulfhydryl groups, silver nitrate.
Give examples of ionizing and nonionizing radiation.
ionizing: gamma/xrays used in food
non ionizing- UV/visible light, used in hospitals on hard surfaces
How does ozone work and what is an example?
high voltage passed through water to kill microbes.
How do oxidizing agents work and what is an example?
oxidize proteins
hydrogen peroxide antiseptic, benzoyl peroxide good for wounds and acne, peracetic acid good against all bacteria and viruses
What is HTST?
high temperature short time pasteurization
How does ethylene oxide work and what are examples?
denatures proteins by alkylation of some amino acids, used for food and soft items
Why are microwaves not good at sterilizing solid foods?
their waves are not powerful enough to disrupt the DNA. Instead steam produced can kill cells.
How do phenols and phenolics work and what is an example?
work by injuring the plasma membrane, lysol.
How do surfactants work and what is an example?
reduce surface tension of water and create micelles around microbes. Tridocaraban in soaps.
- How does modern day pasteurization differ from classic pasteurization?
Classic: mild heat for longer
modern: higher heat for short amount of time
When would you not want to use heat to sterilize? What other methods could you use?
Anything that is temperature sensitive. Could use filtration or radiation
What is a HEPA filter?
high efficiency particulate air filter, used to remove bacteria and allergens from the air. .3um pore
List 4 criteria that would be important when choosing a disinfectant.
- concentration needed to be effective
- toxicity to humans
- which species can be killed
- time needed for it to work
- compatibility with material needing to be treated
How do alcohols work and what is an example?
Denature proteins, isopropyl.
Define antisepsis
removing microbes from a living surface
How do halogens work and what is an example?
disinfection through disruption of oxidative phosphorylation and betaiodine and chlorine.
In general, which type of bacteria are resistant to chemical methods.
endospore formers
Describe the use of osmotic pressure to control growth. What foods use this method?
Hypertonic solution breaks plasma membrane. Used in foods like pickles and jams.
Why is moist heat faster than dry heat in its effect on cells?
moist heat causes denaturation and coagulation of proteins by breaking H bonds in the 3d structure
define microbial death
When microbes can no longer reproduce/replicate
Why is desiccation not a good method of controlling microbial growth?
microbes can be reactivated if put in a liquid environment
Describe some important considerations when choosing an antimicrobial procedure.
site to be treated
relative susceptibility of microbes
environmental conditions
How do chemical food preservatives work and what are examples?
sorbic acid or sodium benzoate prevent mold
nitrates and sodium nitrite, inhibit endospore formers
Define sterilization
destruction of all microbes
Define bactericidal
kills bacteria
Why are quaternary ammonium compounds (quats) ineffective against most Pseudomonas spp.?
pseudomonas uses them as food
Define bacteriostatic
keeps bacteria from multiplying
How do Quats work and what is an example?
Breakdown of cell membrane, benzalkonium chloride
Describe how an autoclave works.
Steam and pressure in a chamber, air is replaced by steam.
