Sterilization and Disinfection Flashcards
Antisepsis
controlling the number of microorganisms and viruses
Aseptic
No microbes in the environment
-cide
-cidal
sudden death of microbe
Degerming
removal of microbes by mechanical means through handwashing or alcohol swabbing of the site of infection
Disinfection
reducing the number of pathogens to the point of where they no longer pose a threat of causing disease
Sanitization
removal of pathogens from objects to meet public health standards
Sterilization
destruction or removal of all microbes and viruses in or on an object
Microbial death
permanent loss of reproductive ability under ideal environmental conditions
Microbial death rates
often constant for a microorganism under particular set of conditions
Alteration of cell walls and membranes - 1st mode of action of antimicrobial agents
cell wall must maintain integrity of the cell, however if damaged due to physical or chemical agents, then the cell bursts due to osmotic effects; therefore, the cytoplasmic membrane contents, cytoplasm and the control passages of chemical in or out of cell, leak out when damaged
Damage to proteins and nucleic acids - 2nd mode of action of antimicrobial agents
protein functions on its 3D shape, however, extreme heat or chemicals can cause denature of proteins and changes shape causing cellular death; nucleic acids also can be altered or destroyed by chemicals, radiation, and heat by bringing about fatal mutations to the molecules; in addition, the interference of nucleic acids can also stop protein synthesis because of ribozyme
Selection of Microbial Control Methods
ideally agents for the control of microbes should be inexpensive, fast-acting, stable during storage, and capable to controlling microbial growth while being harmless to humans, animals, and objects
Site to be treated - factors affecting the efficacy of antimicrobial methods
harsh chemicals and extreme heat cannot be used on humans, animals, and fragile objects; method of microbial control based on site of medical procedure because the site can carry the potential for infections
Susceptibilities of Microbes to Antimicrobial agents
Prions being the most resistant to enveloped viruses being the most susceptible
High-level germicides
kill all pathogens, including endospores
Intermediate level germicides
kill all fungal spores, protozoan cysts, viruses and pathogenic bacteria
Low level germicides
kill vegetative bacteria, fungi, protozoa, and some viruses
Environmental conditions - factors affecting the efficacy of antimicrobial methods
Temp and ph will affect microbial death rates and alter the efficacy of antimicrobial methods; organic materials such as fat, feces, blood, and vomit, can interfere with the penetration of heat, chemicals, and some forms of radiation, therefore may inactivate chemical disinfectants
Factors that influence the action of antimicrobial agents - recap
the number and nature of microbes in the population, the temp and pH of the environment, the concertation of the agent, the more concentrated the better; the mode of action and the presence of solvents, interfering organic matter, and inhibitors.
Biosafety Level 1
handling pathogens that do not cause disease in healthy
Biosafety Level 2
handling moderately hazardous agents
Biosafety Level 3
handling microbes in safety cabinets
Biosafety Level 4
handling microbes that cause severe or fatal disease
Moist Heat - Physical methods of microbial control
is used to disinfect, sanitize, sterilize, and pasteurize and kill cells by denaturing proteins and destroys cytoplasmic membranes; more effective than dry heat
Boiling - Moist Heat
kills vegetative cells by bacteria and fungi, protozoan trophozoites, and most viruses, however, endospores, protozoan cysts, and some other viruses can survive boiling; the boiling time is critical, although different elevations in the atmosphere require different boiling times
Autoclaving - Moist Heat
pressure applied to boiling water prevents steam from escaping; the boiling temp increases as pressure increses
Pasteurization - moist heat
used for different kinds of diary products; it is not sterilization because some pathogens are heat-loving and heat-tolerant; there are batch, flash, ultra-high temp pasteurization
Ultra-high temp sterilization
treated liquids can be stored at room temp, put on for 140 degrees celcius for 1 to 3 seconds and then rapid cooling
Dry Heat
used for materials that cannot be sterilized with moist heat; denatures proteins and oxidizes metabolic and structural chemicals; air doesn’t transfer heat like moist does; incineration is ultimate means of sterilization
Refrigeration and freezing
decreases microbial metabolism, growth, and reproduction by having the chemical reactions slower at low temps and liquid water not available; however some microbes can multiply in refrigerated foods such as Listeria; slow freezing is more effective than quick freezing
Desiccation
drying inhibits growth due to removal of water
Osmotic pressure
high concentrations of salt or sugar in foods inhibit growth of microbes; cells in hypertonic solution of salt or sugar lose water; fungi have greater ability than bacteria to survive hypertonic environments
Ionizing radiation
strike molecules, they have sufficient energy to eject electrons from atoms and creating ions; the ions disrupt hydrogen bonding, oxidize double covalent bonds, and create hydroxyl radicals; the ions also denature other molecules, particularly DNA, causing fatal mutations and cell death
Filtration
the passage of a fluid though a sieve designed to trap particles, cells or viruses used to separate from the fluid
Nonionizing radiation
does not have enough energy to force electrons out of orbit; includes UV light; suitable for disinfecting air, transparent fluids, and surfaces of objects
Action of a Surfactant
in insoluble substance, dirt or grease, is being attached by surfactant molecules, found in cleaning products, and while rinsing our hands or a dish, it washes away the bacteria along with the surfactant molecule, doesn’t necessarily kill it; decreases surface tension of water and disrupt cell membranes
Phenol and Phenolics - Chemical methods of microbial control
denature proteins and disrupt cell membranes; it acts as a surfactant
Alcohol - Chemical methods of microbial control
denature proteins and disrupt cytoplasmic membranes as long it has water with it; 70% alcohol will act better than 90%; acts as a surfactant
Halogens - Chemical methods of microbial control
damage enzymes by denaturation of proteins; iodine tablets, iodophors, chlorine treatment, bleach, chloramines, and bromine disinfection will become loose ions that will cause the hydrogen to hook up to ions and cause to denature proteins
Oxidizing Agents - Chemical methods of microbial control
kill by oxidation of microbial enzymes (denatures proteins); any oxidated solutions with oxygen will be able to denature proteins
Quaternary ammonium compounds
are surfactant in which the hydrogen atoms of an ammonium ion are replaced by other functional groups or hydrocarbon chains
Heavy metals - Chemical methods of microbial control
denature proteins by combining sulfur atoms with cysteine, an amino acid; some heavy metals are arsenic, zinc, mercury, silver, and copper
Aldehydes - Chemical methods of microbial control
cross link functional groups to denature proteins and inactivate nucleic acids; glutaraldehyde disinfects and sterilizes; formalin used in embalming and disinfection of rooms and instruments
Gaseous agents - Chemical methods of microbial control
denatures proteins and DNA by cross-linking functional groups by using ethylene oxide, propylene oxide, and beta-propiolactone
Antimicrobial drugs
antibiotics, semisynthetic, and synthetic chemicals
Use-dilution test - methods of evaluating disinfectants and antispetics
a researcher dips several metal cylinders into broth cultures of bacteria and briefly dries them at 37 degrees Celsius; Contaminated cylinder immersed into dilution of disinfectant; Cylinders removed, washed, and placed into tube of medium; Most effective agents entirely prevent growth at highest dilution
