Control of Microbial Growth Flashcards
What is BSL-1?
working with microbes that have the lowest risk for infection. They generally do not cause disease in healthy hosts.
- An example of a microbe that would be used in BSL-1 is E. coli.
- Few precautions are needed because they pose a low risk to both workers and the environment.
What is BSL-2?
microbes that pose a moderate risk to lab workers and the environment. An example of a microbe in this level would be Staphylococcus aureus
What is BSL-3?
microbes could potentially cause lethal infections and serious diseases. These microbes can infect an individual if inhaled.
- Examples of microbes in this category would be Mycobacterium tuberculosis and Bacillus anthracis.
What is BSL-4?
microbes that are very contagious and quite dangerous. They can cause infections that have no treatments or vaccinations.
- An example would be the Ebola virus.
What biosafety level do we work at in the BLC?
BSL-2
What is sterilization?
completely kills or eliminates all vegetative cells, viruses, and endospores from the targeted item
What is the aseptic technique?
method that maintains sterility as it prevents contamination of an item with microbes
What is disinfection?
antimicrobial chemicals or heat are used to inactivate most microbes on the surface of an inanimate item
- reduces the microbial load, but it does not completely eliminate all microbes on the surface
What is antisepsis?
an antimicrobial chemical is used to reduce the microbial load on tissue or skin.
What is degerming?
gentle scrubbing of living tissue or the use of mild chemicals are used to significantly reduce microbial load
- Ex: hand washing.
What is sanitizing?
antimicrobial chemicals or heat are used to reduce microbial load of a fomite
- reduces microbial load to levels that are safe for public health.
What is a fomite?
inanimate objects that you could touch that could be involved in the process of transmission
- Ex: doorknobs, silverware
What is cidal?
suffix that describes when a method can kill a target microbe
What is static?
suffux used to describe a method that does not kill a microbe but instead, stops or inhibits their growth
What is the prefix bacteri-?
describes bacteria
What is the prefix viri-?
describes viruses
What is the prefix fungi-?
describes fungi
What is a microbial death curve?
used to measure the effectiveness of microbial control methods
- describes how well a certain protocol works by looking at the percentage of microbes that are killed in a population
- the number of live bacterial cells is plotted against time
- the D value shows the time it takes for the number of cells to decrease by 90%.
What are methods that use heat?
incineration, oven, autoclave, boiling, and pasteurization
What are dry-heat methods?
incineration and oven
What are moist-heat methods?
autoclave, boiling, and pasteurization
What is incineration?
dry heat is applied at very high temperatures that destroy all microbes
- destroys all microbes, even prions, by burning
* used in a flaming loop or micro incinerator*
What is dry-heat oven?
dry heat is applied for long periods of time at higher temperatures (170°C for 2 hours)
- dehydrate, desiccate, alter membranes, and denature proteins
* sterilize glassware and some lab equipment*
What is autoclave?
high temperature and pressure are used to sterilize items
- alters membranes and denatures proteins
- can kill endospores, viruses, and vegetative cells
- considered the most effective method of sterilization
* sterilize lab equipment and microbiological media*
What is boiling?
alters membranes and denatures proteins at 100°C.
- effective at killing vegetative cells and some viruses
- less effective at killing endospores
* used in cooking and when preparing certain lab media*
What is pasteurization?
form of microbial control for food that is used in food preservation
- used to kill heat-sensitive pathogens in food products
- alters membranes and dentures proteins
- heat is used to reduce the number of microbes in a product or food
* used to prevent spoilage of foods like milk and honey*
What is UHT?
food product is exposed to a temperature of 138° C for more than two seconds
- causes slight changes in the taste and smell of food, but it can be stored for longer periods without spoilage.
What is refrigeration?
metabolism is inhibited or slowed
- does not kill cells
- temperatures of around 0°C to 7°C are used
helps to preserve food or lab materials
What is freezing?
can stop metabolism and even kill microbes
- temperatures below -2°C are used
helps in the long-term storage of lab cultures and food
What is pascalization (high-pressure processing)?
Being exposed to high pressure can kill many microbes
- can kill bacteria, molds, yeasts, viruses, and parasites in foods
used in food preservation as it helps extend shelf-life while also maintaining the food quality
- can kill vegetative cells by protein denaturation, and it can cause cells to lyse, but endospores can survive under these pressures
What is dessication
uses dehydration or drying to preserve foods
- desiccation can control microbial growth by inhibiting metabolism
- does not kill all microbes or endospores.
It is used to make dried fruits or jerky
What is ionizing radiation?
involves the exposure of microbes to X-rays or gamma rays
- alter the molecular structures of cells and damage their DNA
used to sterilize materials that cannot be autoclaved
What is non-ionizing radiation?
involves the exposure of microbes to ultraviolet light
used for disinfection of surfaces in labs and the disinfection of water and air
- introduces thymine dimers that can lead to cell mutations
What is HEPA filtration?
filters with a pore size that is small enough to capture and remove microbes such as endospores, many viruses, and bacterial cells as air flows through them
- effective at nearly sanitizing air
used in biosafety cabinets and operating rooms
What is membrane filtration?
effective pore size used to remove microbes from liquid solutions
- sizes depend on the volume of solution that is being filtered
used to remove bacteria from heat-sensitive solutions. For instance, antibiotics and vitamins
What are phenolics?
chemical disinfectant and antiseptic characterized by its phenol group
- the phenol group inhibits microbial growth as it denatures proteins and disrupts membranes.
What are heavy metals?
kill microbes by binding to proteins
- this binding inhibits enzymatic activity
They are used as disinfectants and antiseptics
What are halogens?
oxidize cellular components and destabilize macromolecules in cells
What are alcohols?
used as disinfectants and antiseptics
- rapidly denatures proteins causing the inhibition of cell metabolism
- also disrupt membranes leading to the lysis of cells.
What are surfactants?
these are used for degerming
- in soaps, detergents, and mouthwash
- lower the surface tension of water and create emulsions that help wash away microbes
- also disrupt cell membranes.
What are bisbiguianides?
contains antiseptic properties
- disrupts cell membranes at low concentrations
- also causes congealing of intracellular contents at high concentrations
What is chlorhexidine?
an important bisbiguanide
- disrupts cell membranes and is bacteriostatic at lower concentrations or bactericidal at higher concentrations.
What are alkylating agents?
group of strong disinfectant chemicals that inactivate enzymes and nucleic acid by replacing a hydrogen atom in a molecule with an alkyl group.
What is ethylene oxide? What is different about this chemical? What are advantages and disadvantages of this?
form of cold sterilization used for gaseous sterilization
- disadvantages: highly explosive and carcinogenic
- advantages: highly penetrating and can sterilize items within plastic bags
What are peroxygens?
strong oxidizing agents that can be used as antiseptics or as disinfectants
- cause destabilization of cellular macromolecules
- also causes free radical formation in cells
What are supercritical gases (supercritical CO2)?
penetrates cells and forms carbonic acid, lowering intracellular pH
- effective against vegetative cells and can kill endospores when it is combined with peracetic acid
What are food preservation methods?
chemical preservatives can minimize spoilage in some foods and inhibit microbial growth
- decrease pH and inhibit enzymatic function and the synthesis of the cell wall.
