Lecture 23 Flashcards
What is sepsis?
bacterial contamination
What is asepsis?
absence of significant contamination
Why do we use aseptic surgery techniques?
prevents microbial contamination of wounds
What is sterilization?
removing and destroying all microbial life
What is commercial sterilization?
killing Clostridium botulinum endospores from canned goods
What is disinfection?
destroying harmful microorganisms
What is antisepsis?
destroying harmful microorganisms from living tissue
What is degerming?
mechanical removal of microbes from a limited area
What is sanitization?
lowering microbial counts on eating utensils to safe levels
What is biocide?
germicide
- treatments that kill microbes
What is bacteriostasis?
inhibiting, not killing, microbes
What does the effectiveness of microbial treatment depend on?
- number of microbes
- environment
- time of exposure
- microbial characteristics
What are the actions of microbial control agents?
- alteration of membrane permeability
- damage to proteins (enzymes)
- damage to nucleic acids
How does heat affect enzymes?
heat denatures enzymes
What is thermal death point?
lowest temperature at which all cells in a liquid culture are killed in 10 minutes
What is thermal death time?
minimal time for all bacteria in a liquid culture to be killed at a particular temperature
What is decimal reduction time?
minutes to kill 90% of a specific population of bacteria at a given temperature
How does moist heat sterilization work?
-coagulates/denatures proteins
- steam from boiling or free-flowing steam
- large containers require longer sterilization times
- test strips indicate sterility
What is a common example of moist heat sterilization?
autoclave
- kills all organisms and endospores
- steam must contact item’s surface
What does pasteurization do?
reduces spoilage organisms and pathogens by heating materials for a short time
What are equivalent treatments for pasteurization?
- high-temperature short time
- ultra-high temperature
What is thermoduric?
relatively heat-resistant organisms survive
What is dry heat sterilization?
kills by oxidation
- flaming
- incineration
- hot-air sterilization
How does filtration work? Why is it used?
passage of substance through a screenlike material
- heat-sensitive materials
What are HEPA filters?
- high-efficiency particulate air filters
- removes microbes > 0.3 micrometers in diameter
What do membrane filters remove?
microbes > 0.22 micrometers
What are some physical methods of microbial control?
- low temperature (refrigeration, deep freezing, lyophilization)
- high pressure denatures proteins
- desiccation: absence of water
- osmotic pressure causes plasmolysis
What effect does low temperature have?
bacteriostatic effect
What is ionizing radiation?
x-rays, gamma rays, electron beams
- ionizes water to create reactive hydroxyl radicals
- damages DNA by causing lethal mutations
What is nonionizing radiation?
ultraviolet (260 nm)
- damages DNA by creating thymine dimers
How do microwaves work?
kill by heat
What are principles of effective disinfection?
- concentration of disinfectant
- organic matter
- pH
- time
What are dilution tests?
- metal cylinders are dipped in test bacteria and dried
- placed in disinfectant
- transferred to culture media to determine whether the bacteria survived or not
What is the disk-diffusion method?
- evaluates efficacy of chemical agents
- filter paper disks are soaked in a chemical and placed on a culture
- look for zone of inhibition around disks
What are biguanides for?
used in surgical hand scrubs
- disrupts plasma membranes
- chlorhexidine
What are essential oils?
- mixtures of hydrocarbons extracted from plants
- used in traditional medicine and for preserving food
- microbial action due to phenolics and terpenes
- stronger activity against gram-positive bacteria
What does iodine do?
impairs protein synthesis and alters membranes
What is tincture?
iodine solution in aqueous alcohol
What is iodophor?
iodine combined with organic molecules
What does chlorine do?
oxidizing agents
- shut down cellular enzyme systems
What is bleach?
hypochlorous acid
What is chloramine?
chlorine + ammonia
What do alcohols do?
denatures proteins and dissolves lipids
- no effect on endospores and nonenveloped viruses
How should ethanol and isopropanol be used?
mixed with water
What is oligodynamic action?
very small amounts exert antimicrobial activity
What do heavy metals do?
denature proteins
What is silver nitrate used for?
to prevents ophthalmia neonatorum
What does mercuric chloride do?
prevents mildew in paint
What is copper sulfate?
algicide
What is zinc chloride?
used in mouthwash
What does sulfur dioxide do?
prevents wine spoilage
What do organic acids do?
inhibits metabolism
What prevents molds in acidic foods?
- sorbic acid- benzoic acid
- calcium propionate
What do nitrites and nitrates do?
prevents endospore germination
What do aldehydes do?
inactivated proteins by cross-linking with functional groups
- used for preserving specimens and in medical equipment
What are examples of aldehydes?
- formaldehyde
- ortho-phthalaldehyde
- glutaraldehyde
What are peroxygens used for?
oxidizing agents
- contaminated surfaces and food packaging
What are examples of peroxygens?
O3
H2O2
peracetic acid
