chapter 13! Flashcards
sterilization
the removal or destruction of ALL living microbes and endospores.
most common method is heating.
sterilant
sterilizing agent
disinfectant
chemical used to treat inert/non-living surfaces.
disinfection
control directed at destroying harmful microbes, only vegetative (actively diving) cells, NO ENDOSPORES.
antisepsis
same treatment as a disinfectant, aimed directed at destroying harmful microbes, but for LIVING tissue.
antiseptic
chemical used to treat living tissue.
degerming
mechanical removal most microbes on a limited area.
handwashing and alcohol swab.
sanitization
lowers microbial counts, not to zero, but enough to be at safe public health levels and minimize the chances of disease transmission.
method: using high-temperature washing.
biocide
kills microbes
other types: fungicide, virucide.
bacteriostasis
inhibits the growth and replication of bacteria + keeps it STEADY.
once removed, growth may resume.
sepsis
bacterial contamination.
asepsis
the absence of significant contamination.
aseptic
indications an object or area is free of pathogens.
the rate of microbial death:
- bacterial populations die at a constant rate when heated or treated with antimicrobe chemicals, which is plotted logarithmically. time it takes to kill = the number of microbes.
- the number of microbes, environmental influence, time of exposure, and microbial characteristics influence the effectiveness of anti-microbes.
microbial growth agents can:
- cause damage to the plasma membrane (cellular contents leak)
- cause damage to proteins (enzyme function)
- cause damage to nucleic acids (replication and metabolic processes)
what are the 2 physical methods of microbial control?
- heat
- radiation
thermal death point
the lowest temperature at which all microbes in a fluid culture will be killed in 10 minutes.
thermal death time
the minimal time required to kill all the bacteria in a liquid culture at a given temperature.
decimal reduction time
the length in time at which 90% of a bacterial population will be killed at a given temperature.
moist heat sterilization includes:
- boiling or free-floating steam
- autoclave (kills endospores)
- pasteurization: reduced spoilage organisms and pathogens by using a high temp for a short amount of time.
- all 3: coagulates and denatures proteins ! mechanism to damage enzymes.
dry heat sterilization includes:
- direct flaming to sterlize tools like loops.
- inceneration.
- kills microbes by oxidation effects.
radiation includes:
- ionizing radiation: x-rays, gamma rays, electron beams. ionizes water to create reactive hydroxyl radicals to damage DNA and cause lethal mutations. shorter wavelength.
- non-ionizing radiation: damages DNA by creating thymine dimers. (ex. sun radiation leads to cancer). longer wavelength.
- microwaves.
chemical methods of microbial control:
- are used on living tissue (anti-septic) and on inanimate objects (disinfectants).
- most chemical agents only reduce microbe populations to safe levels + remove vegetative (active) cells, not achieve sterility.
principles of effective disinfection:
- concentration of effective disinfection
- organic matter
- pH
- time
the disk diffusion method:
- evaluates the effectiveness of a chemical agent
- filter paper discs are soaked in a chemical agent and placed on a culture.
- zone of inhibition
agents that disrupt the plasma membrane:
- phenol: carbolic acid.
- phenolics: cresol and o-phenylphenol. disinfectant.
- biphenols: hexachlorophene and triclosan. disinfectant.
- biguanides: chlorhexidine. antiseptic
- essential oils: peppermint, pine, and orange oil.
- surface active agents: soaps. degerming.
agents that impair protein synthesis AND alter the plasma membrane:
- halogens: iodine and chlorine. disinfectant.
- alcohol: ethanol and isopropanol. antiseptic and disinfectant.
agents that cause protein denaturation ONLY:
- heavy metals: silver nitrate and silver sulfadiazine.
- aldehydes: formaldehyde and glutaraldehyde. sterilizing agent. mycobacteria.
