Sterilization and disinfection Flashcards
Disinfectant
A chemical agent used on INANIMATE objects to destroy microorganisms. Most do not kill spores
Antiseptic
A chemical agent that can safely be used externally on living tissue to destroy microorgansims or to inhibit their growth
Bactericidal
refers to an agent that kills bacterial
bacteriostatic
refers to an agent that inhibits the growth of bacteria.
Sanitizer
a chemical agent that is typically used on food handling equipment and eating utensils to reduce bacterial numbers so as to meet public health standards. Sanitization may simply refer to thorough washing with only soap or detergent.
Germicide
an agent capable of killing microbes rapidly; some such agents effectively kill certain microorganism but only inhibit the growth of others
Viricide
an agent that inactivates viruses
fungicide
an agent that kills fungi
Sporocide
An agent that kills bacterial endospores or fungal spores
Filler based essay
also known as the filler paper method
It uses small filler paper disks, each soaked with a different chemical agent. The disks are placed on the surface of an agar plate that has been inoculated with a test organism. A different plate is used for each test organism. After incubation, a chemical agent that inhibits growth of a test organisms is identified by a clear area around the disk where the bacteria have been killed.
Use-Dilution Test
uses standard preparations of certain test bacteria. A broth culture of one of those bacteria is coated onto small stainless steel cylinderss and allowed to dry. Each cylinder is then dipped into one of several dilutions of the chemical agent for 10 minutes, removed, rinsed with water, and placed into a tube of broth. The tubes are incubated and then observed fro the presence or absence of growth. Agents that prevent growth at the greatest dilutions are considered the most effective. Believed to be more effective than phenol coefficient
Phenol coefficient
since lester introduced phenol (carbolic acid) as a disinfectant in 1867, it has been the standard disinfectant to which other disinfectants are compared under the same conditions. The result of this comparison is called the phenol coefficient. Two organisms, salmonella typhi, a pathogen of the digestive system, and staphylococcus aureus, acommon wild pathogen, are typically used to determine phenol coefficients. A disinfectant with a phenol coefficient of 1.0 has the same effectiveness as phenol. A coefficient less than 1.0 means that the disinfectant is less effective than phenol. A coefficient greater than 1.0 means that it is more effective. The test provides an acceptable means of evaluating the effectiveness of chemical agents derived from phenol, but it is less acceptable means of evaluating the effectiveness of chemical agents derived from phenol, but it is less acceptable means of evaluating the effectiveness of chemical agents derived from phenol, but it is less acceptable for other agents.
An ideal disinfectant should
- be fast acting even in the presence of organic substances, such as those in body fluids
- be effective against all types of infectious agents without destroying tissues or acting as a poison if ingested
- easily penetrate material to be disinfected without damaging or discoloring the material
- be easy to prepare and stable even when exposed to light, heat, or other environmental factors
- be inexpensive and easy to obtain and use
- not have an unpleasant odor
Bacterial cell components that chemical agents damage are
- proteins
- membranes
- nucleic acids
- energy producing systems
reactions that affect proteins
alteration of a protein is called denaturation. This is where hydrogen and disulfide bonds are disrupted, and the structural shape of the protein is destroyed. These reactions include: hydrolysis, oxidation, and the attachment of atoms or chemical groups
Reactions that affect membranes.
surfactants and wetting agents
Surfactants
soluble compounds that reduce surface tension, just as soaps and detergents break up grease particles in dishwater.
Dissolve lipids, disrupt membranes, and inactivate enzymes in high concentrations.
Wetting agents
often used with other chemical agents to help the agent penetrate fatty substances
Reactions that affect other cell compontents
other cell components include nucleic acids and energy producing systems. Alkylating agents can replace hydrogen on amino or alcohol groups in nucleic acids. Certain dyes such as crystal violet interfere with cell wall formation
Soaps and Detergents
lower surface tension, make microbes accessible to other agents.
washing hands
acids
lower pH and denature proteins
food preservation
Alkalis
Raise pH and denature proteins
found in soaps
Heavy Metals
dentature proteins
mercury compounds to disinfect skin an inanimate objects, silver nitrate is used to prevent gonococcal infections, copper to inhibit algal growth, and selenium to inhibit fungal growth
Halogens
oxidize cell components in absence of organic matter
chlorine used in water to kill pathogens
alcohols
denature proteins when mixed with water
isopropyl alcohol used to disinfect skin
phenols
disrupt membranes, denature proteins, inactivate enzymes
phenol used to disinfect surfaces and destroy discarded cultures
Oxidizing agents
Disrupt structure of proteins and nucleic acids
Hydrogen Peroxide used to clean puncture wounds
Alkylating Agents
disrupt structure of proteins and nucleic acids
formaldehyde used to inactivate viruses
Dyes
may interfere with replication or block cell wall synthesis
crystal violet used to treat some protozoan and fungal infections
Thermal Death Point
the temp that kills all the bacteria in a 24 hr old broth culture at neutral pH in 10 min
thermal death time
the time required to kill all the bacteria in a particular culture at a specified temp
Three ways to kill microbes
dry heat, moist heat, and pasteurization
Dry Heat
does most of its damage by oxidizing molecules and penetrates stuff more slowly than moist heat. It is usually used to sterilize metal objects and glassware and is the only suitable means of sterilizing oils and powder.
Moist Heat
destroys microorganisms mainly by denaturing proteins; the presence of water molecules helps disrupt the hydrogen bonds and other weak interactions that hold proteins in their 3d shapes. Destroys vegetative cells of most bacteria and fungi, also inactivates some viruses
sterilizing canned food and autoclaving sterilizes not metal hospital and laboratory equipment.
Pasteurization
doesn’t achieve sterility but does kill pathogens in milk, other dairy products, and beer
Other antimicrobial agents
UV light, drying, ionizing radiation, filtration, and osmotic pressure
Physical antimicrobial agents
dry heat, moist heat, pasteurization, refrigeration, freezing, drying, freeze drying, ultraviolet light, ionizing radiation, microwave radiation, strong visible light, sonic and ultra sonic waves, filtration membranes, osmotic pressure
refrigeration
slows the rate of enzyme controlled reactions
used to keep foods fresh for a few days, does not kill microorganisms
Freezing
greatly slows down the rate of most enzyme controlled reactions
used to keep foods fresh for a few months, does not kill microorganisms
Drying
inhibits enzymes
used to preserve some fruits and vegetables, preserves food because the absence of water inhibits the action of enzymes
Freeze Drying
inhibits enzymes
preserves microorganisms for years and can manufacture instant coffees
UV light
Denatures proteins and nucleic acids
used to reduce the # of microorganisms in air operating rooms, animal rooms, and where cultures are transferred
Ionizing Radiation
denatures proteins and nucleic acids
used to sterilize plastics and pharmaceutical products and to preserve foods. X-rays and gamma rays
Microwave Radiation
absorbs water molecules, then releases microwave energy as heat
cannot be used reliably to destroy microbes except in special media sterilizing equipment
Strong visible light
oxidation of light sensitive materials
can be used with dyes to destroy bacteria and viruses; may help sanitize clothing
Sonic and ultrasonic sound waves
cause cavitation
not practical means of killing microorganisms but useful in fractionating and studying cell components
Filtration Membranes
Mechanically removes microbes
used to sterilize media, pharmaceutical products, and vitamins, in manufacturing vaccines, and in sampling microbes in air and water. like using a strainer
Osmotic pressure
removes water from microbes
used to prevent spoilage of foods such as pickles and jellies.
