Controlling Microbes Flashcards
detergents act as
wetting agents and emulsifiers
is the single most important step to achieving control
hand washing
hospital acquired infections
nosocomial infections
what is most common and most reliable mechanism in regards to food/ production
heat treatment
agent which kill microbes
-cide
kill microorganisms and viruses, but not
necessarily endospores
germicide
agent which prevents microbial growth
-static
the complete removal or destruction of all microbes
Even spores and viruses are removed
sterilization
Killing C. botulinum endospores
commercial sterilization
the killing, inhibition or removal of most disease causing
microbes
Also reduces the total microbial population
disinfection
agents, generally chemical, used on inanimate
objects
disinfectants
form of disinfection designed to prevent infection
by microorganisms in/on living tissue
Antisepsis
chemical agents that kill or inhibit
growth of microorganisms when applied to tissue
Antiseptics
substantial reduction of microbial population
to levels that meet accepted public health standards
sanitation
treatment to reduce microbes to a level considered safe
decontamination
removal of microbes from a surface by
mechanical means
Degerming
what are the conditions affecting the effectiveness of antimicrobial activity
What microorganisms are present Amount of contamination Concentration or intensity of an antimicrobial agent Duration of exposure Temperature Local environment Composition of the item
how do microbes die
Microbes are not killed instantly Microbes are considered to be dead when they are unable to reproduce in conditions that normally support their reproduction
usually enhance the effectiveness of an agent
higher temperatures
what do physical methods of control include
Mechanical removal Filtration Drying (reducing water availability) Heat Irradiation
Reduces microbial population or sterilizes
solutions of heat-sensitive materials by
removing microorganisms
Also used to reduce microbial populations in air
Often used in conjunction with other methods
filtration
what are the two main types of filtration
depth and membrane filters
Thick fibrous or granular filters that remove microorganisms by physical screening, entrapment, and/or adsorption
depth filters
Porous membranes with defined pore sizes that remove
microorganisms primarily by physical screening
membrane filters
(freeze drying)
Widely used to preserve foods
Lyophilization
Typically the most cost effective method
Relatively fast, reliable, safe and inexpensive
heat
two types of heat control
dry and moist
Effective against all types of microorganisms
Degrades nucleic acids, denatures proteins, and disrupts membranes
moist heat
Destroys most microorganisms and viruses
Does not destroy endospores
Not effective means of sterilization
boiling
developed to avoid spoilage of wine
Controlled heating at temperatures well below boiling
Does not sterilize but significantly reduces organisms
Used to increase shelf life of food
Pasteurization
Preferred method of sterilization
Pressurized steam
why is dry heat not as effective as moist heat
Sterilization with dry heat requires longer times and higher temperatures
method of dry heat sterilization
Oxidizes cell to ashes
Used to destroy medical waste and animal carcasses
incineration
stops microbial reproduction due to lack of liquid water
some microorganisms killed by ice crystal disruption of cell membranes
Kills up to 50% of microbes
freezing
Low temperatures slow down or
stop enzymatic reactions – slowing
microbial growth and reproduction
refrigeration
what does a shorter wavelength mean
higher frequency and more energy
this can be ionizing or non-ionizing
radiation
Non-ionizing radiation
Damages DNA causing thymine dimers
Generates free radicals
ultraviolet radiation
Includes Gamma radiation, X-rays
Radiation able to strip electrons from atoms (forms ions)
Penetrates deep into objects
Causes damage to DNA and proteins
ionizing radiation
what are Chemical Agents of Control
Disinfectants
Antiseptics
Antibiotics
conditions influencing antimicrobial effectivness
highly effective, Activity in presence of organic material, Compatibility with material being treated, toxicity, residue, storage, cost/availability, environmental risk
Phenolics
cresols
Bisphenols
triclosan
alcohols
– isopropyl, ethanol
peroxides
hydrogen peroxide
halogens
iodine, chlorine
heavy metals
silver, copper
detergents
anionic, cationic
sterilizing gases
ethylene oxide, ozone
who were phenolics first used by
Lister in 1870
what do phenolics do
Act by denaturing proteins and disrupting cell membranes
effective in presence of organic material and long lasting
Commonly used as laboratory and hospital disinfectants
what percent isopropyl or ethyl alcohol
kill vegetative bacteria and fungi
60-80%
Coagulates proteins and essential enzymes and
damages lipid membranes
Commonly used as antiseptic and disinfectant
alcohols
what are the limitations to alcohol
Evaporates quickly, limiting contact time
May damage material such as rubber and
some plastics
Powerful oxidizing agent
Effectiveness depends on surface being treated
Readily biodegradable
hydrogen peroxide
is hydrogen peroxide more effective on living tissue or inanimate objects
inanimate objects
Used as a skin antiseptic in tincture or iodophore
Kills vegetative cells but not reliable with
endospores
iodine
alcoholic solution
tincture
carrier molecule
iodophore
Oxidizing proteins and other cell components
common disinfectant
halogens-iodine
Important disinfectant
Caustic to skin and mucous membranes
Destroys vegetative bacteria and fungi, but not
spores
halogens-chlorine
combine with enzymes and
proteins interfering with function
High concentrations are toxic to human tissue
heavy metal compounds
Organic molecules with hydrophilic and hydrophobic ends
Act as wetting agents and emulsifiers facilitating mechanical removal of organisms
Not disinfectant
detergents
Quaternary ammonium compounds
Are effective disinfectants
Positive charge attracted to negatively charged cells,
reacting with the membrane
cationic detergents
