Microbio 4-2 disinfection and sterilization Flashcards
What is sterilization?
killing of all microorganisms (bacteria, fungi, viruses)
What is germicide? Fungicide? Virocide?
agent used to kill bacteria, fungi, and viruses
What is disinfection?
use of a germicidal, fungicidial, and virocidial chemical agent to destroy the potential infectivity of an inanimate object (ie floor)
What is antisepsis?
use of chemical agents on the surface of the body to kill or inhibit pathogenic bacteria
What does septic mean? Aseptic?
Septic = presence of pathogenic bacteria. Aseptic = absence of pathogenic bacteria.
What does santiize mean?
lowering of bacterial content of food utensils or similar objects, without necessarily killing all bacteria (ie dishes washed in soap)
What are preservatives?
agent used in small, non-toxic, concentrations to inhibit the growth of organisms (ex: lactic acid, acetic acid, propionic acid, benzoic acid)
What is phenol coefficient?
measure of the killing capacity of an agent compared to phenol. Coefficient is the ratio of the minimum killing [ ] of phenol over the minimum killing [ ] of the agent
What does a phenol coefficient >1 indicate?
agent works at a [ ] that is lower than that of phenol.
What are the 3 main physical agents that are used to kill bacteria?
1) heat (wet/dry), 2) filtration, 3) radiation
What is wet heat?
steam under pressure (ie autoclave)
Is wet heat more effective than dry heat? Why?
Yes. Because the water molecules speed up the protein denaturation
What is wet heat not suitable for?
heat-sensitive materials (ie plastics)
What settings would you change if you were to use dry heat instead of wet heat?
increase the temperature and time needed for sterilization
When is dry heat more appropriate than wet heat?
used when materials would be damaged by water (ie powders, special surgical dressings)
What is pasteurization? How is this different than flash pasteurization?
Pasteurization is essentially mild heating (63˚C for 30 min). Flash pasteurization essentially high temperature, short time (71-72˚C for 15-17 sec). Used in the treatment of wine, milk, juices etc
T/F Pasteurization does not kill spores.
True.
When would you use filtration over heat?
when liquid material is sensitive to heat (ie it contains enzymes).
What are the advantages and disadvantages of using filtration?
Advantages: non-destructive. Disadvantage: inconvenient, esp if large volumes are involved.
What are the two types of radiation that is commonly used to sterilize objects?
non-ionizing radiation (ie UV light emitted by mercury vapor lamps), and ionizing radiation (x-rays, gamma rays).
How does radation work to sterilize objects? (2)
causes 1) thymidine dimers (interferes with DNA replication) 2) peroxide formation (toxic)
Pros and cons of using UV radiation to sterilize objects?
pros: easy to set up. Cons: poor capacity to penetrate anything but air and the thinnest layers of solids/liquids
What other physical forms other than heat, filtration, and radiation can be used to sterilize objects?
1) drying, 2) high osmotic pressure, 3) high sugar concentration
What are examples of some chemical methods used to sterilize objects? (9)
1) gas, 2) alcohol, 3) halogens, 4) detergents, 5) oxidizing agents, 6) phenols, 7) heavy metals, 8) dyes, 9) aldehydes, 9) preservatives
When is gaseous sterilization preferred over other methods of sterilization?
when sterilizing dry materials that are heat-sensitive (ie plasticware, surgical equipment, etc)
What is ethylene oxide?
gas that is used to sterilize heat-sensitive materials. Alkylating agent.
Ethylene oxide is an explosive agent and can only be used in the presence of this.
high concentrations of CO2
When is ethanol preferred over other methods of sterilization?
when using on skin before injections.
Does ethanol kill spores?
of course not.
What is tincture?
medicine made by dissolving a drug in alcohol
What is a tincture of iodine best used for?
(iodine in water-ethanol solution); used as a antiseptic for minor skin wounds or surgery.
What are the two halogens that are widely used for sterilization?
Iodine and Chlorine
What is chlorine best used for?
sanitizing agent for water supplies, surfaces
What are cationic detergents best used for?
anti-sepsis of skin, mucous membranes, and wounds (mostly superficial)
How does cationic detergents work?
disrupts bacterial cell membranes and/or protective films
What is Zephiran?
cationic detergent that disrupts bacterial cell membranes and/or films
Cationic detergents are essentially useless against these two strains of bacteria:
pseudomonas (in burn infections) and mycobacterium tuberculosis.
What are two examples of oxidizing agents?
H2O2 and KMNO4
What is H2O2 and what is it best used for?
used to treat deep wound infections, where anaerobes reside.
H2O2 is essentially useless against which types of bacteria? What is an example?
Any bacteria that is catalase (+), which degrades H2O2 to water and oxygen. Staphylococci is catalase (+)
What is KMNO4 used for?
oxidizng agent, mostly as a urethral antiseptic
What are phenols? What are limitation(s) in using phenol?
agent that denatures proteins and therefore kills a wide variety of bacteria. Requires high concentrations.
What are phenols best used for?
skin antiseptic (ie hexylresorcinol) or textile preservative (triclosan)
What are surfactants and what are they best used for?
surface-active agents (soap) or anionic detergents that are weakly bacteriocidal. Best used for removing bacteria and dirtf from skin surfaces.
What is triclosan?
phenol/general bacteriocide that is included in soaps and products (ie lotions); inhibits a step in lipid biosynthesis. Resitant mutants mutants have can be isolated.
What are two types of heavy metals that are commonly used as a disinfectant?
silver nitrate (eyes of newborns to kill gonococcal organisms). Mercurial compounds (used on minor skin wounds)
What is gentian violet and what is it best used for?
anti-fungal agent that is used for candida and tinea (athletes foot)
What is formaldehyde and glutaraldehyde?
aldehydes that are used in vaccines (formaldehyde) and areas where blood samples and used syringes are present (glutaraldehyde)
What is cidex?
glutaraldehyde
What is commmonly used to sterilize vaccines?
formaldehyde
What are preservatives?
short chain fatty acids and organic acids that preserve food (ex: lactic acid, acetic acid, propionic acid, benzoic acid, and natural phenolics - thymol and eugenol)
How are smoked foods “sterilized?
smoked foods are covered and partially penetrated by phenolic compounds from wood smoke.
