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133 Cards in this Set

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standard plate count
one method that is commonly used to determine the number of bacteria in milk, various foods and water.
the safety of a food product

the course of infection

the effectiveness of an antibiotic or disinfectant

deciding whether a beach should be closed or not due to fecal contamination
What are some ways that being able to enumerate (count) the number of bacteria in a sample can be crucial to help in determination?
Because the numbers in original bacteria sample are too high to count, so they must be diluted to put in the formula to get the orginal sample number.
Why are samples of bacteria diluted?
colony forming units (CFU)
btwn 30-300 growing in or on the plate.
The # of CFU (30-300) X the dilution factor (the reciprocal of the dilution) = # CFU/g of soil.
What is the formula used to estimate the number of bacteria in the original sample?
aerobic and facultative bacteria
What types of bacteria can grow under these diluted conditions?
1/5 or 1:5 means 1 part in 5 parts total. To make a 1:30 dilution add 1mL sample to 29 mL diluent.
the highest dilution showing a + reaction
sero + = A + rxn
sterile tubes or bottles containing measured amounts of sterile water.
Substances or conditions that kill bacteria without killing them
Substances or conditions that kill bacteria
lethal to fungi
kill inactive viruses
sporicidal agent
kill spores
activity against a wide range of microorganisms.
destruction of all life forms of life. There is no life present in it or on it.
The destruction of vegetative pathogens. Substance still contain living microbes.
Controlling microbial growth doesn't just involve killing or inhibiting them, it involves using microbes to produce an _________, growing genetically engineered microbes to produce a pharmaceutical product, or using them for food production, controlling microbial growth involves keeping them alive and even enhancing their growth.
presence of microbes in the blood.
binary fission
bacterial cells reproduce by an asexual process called _________ _________.
binary fission

daughter cell
the cell replicates its chromosomes (DNA) and them forms a septum that divides the cell into two _________ _____ each containing a complete chromosome.
generation time
doubling time
The amount of time it takes for a cell to replicate itself is termed the ___________ _____ or ___________ _____.
Direct flame
Hot air sterilization
What are the 3 dry heat methods of killing microorganisms?
Direct flame
100% sterilization
burning to ashes
Hot air sterilization
Drying oven (glass ware & instrument needles)
Moist heat method
kills by denaturing proteins.

Boiling in water (e.g.)
Boiling in water
kills most vegetative cells, but not endospores.
growth curve
When bacteria are introduced into a new environment they tend to follow a typical pattern called the ________ ________.
Lag phase
At this stage there is little or no replication. Bacteria at this stage are adjusting to their new environment and synthesizing enzymes to utilize nutrients in the environment.
Logarithmic or exponential growth phase (log for short)
At this stage the bacteria have adapted to the new environment and are metabolically active, reproducing exponentially.
Stationary phase
Due to the depletion of nutrient and the accumulation of waste products the death rate equals the reate of cell replication.
Decline or phase death phase
As nutrient becomes less available and the accumulation of waste products becomes more toxic the death rate exceeds the rate of replication.
logarithmic growth phase
What phase are bacteria more easily killed or inhibited?
log phase
Many antimicrobial substances act by disrupting metabolism and metabolism is maximal during the ______ ______.
log phase
In what phase are the cells dividing so rapidly they don't form thick cell walls, well developed capsules or endospores.
stationary phase
Bacterial cells are harder to destroy in the __________ _______ because they tend to have a lower metabolic rate, thick cell walls, and well developed capsules and endospores.
Tyndallization/Intermittent sterilization
110'C steam or boiling
30 mins for 3 successive days.
Steam heat under pressure.
15 PSI, 121'C, for 15 mins. Results in sterilization.
the movement of water across a semipermeable membrane. Water will move from an area of low solute concentration to an area of higher solute concentration.
Osmotic pressure
the force with which water moves across a membrane due to a concentration gradient. The amount of solute in the environment surrounding a cell can have a profound effect on the growth of a cell.
If the surrounding environment contains a high solute concentration, relative to the interior of the cell, the environment is termed ___________ and there will a net movement of water out of the cell.
The loss of water from the cell will cause the cytoplasm to shrink away from the cell wall and this is called ______________. The loss of water will inhibit the growth of the cells because so many of the cell's metabolic reactions require water.
Some bacteria called __________ (salt loving) can continue to grow in high salt concentrations.
If the surrounding environment has a low solute concentration, the environment is termed __________ and there will be a net movement of water into the cell.
If the solute concentration is the same inside and outside the cell, the environment is termed __________ and water will move in and out of the cell equally.
gradient plates
A double-layered agar plate with a concentration gradient in the upper layer of the agar.
Enzyme activity will increase as the ___________ increases up to a point at which heat will denature the 3-dimensional structure of the enzyme rendering it inactive.
Enzymes slows down and metabolic activity and growth slow down too.
What happens to enzymes when temperature is lowered?
temperature range
Different bacterial species have different optimal, maximum and minimum growth temps and most grow in a ____________ ______ varying from min to max growth temperature by approximately 20-30'C.
psychrophiles or psychrophilic
Bacteria that grow within a temperature range of 0' to 20' C are termed _____________ or ____________.
Bacteria the grow optimally in a range of 20-45'C are termed _________ or _________. Normal human body pathogens temperature is 37'C.
Some organisms that grow optimally in the mesophilic range can also grow, very slowly, at refrigeration temperature and are termed _____________, and some of them produce toxins capable causing food poisoning (food intoxication).
Bacteria which grow in a temperature range from approximately 40-70'C are termed ___________ or _____________.
Extreme thermophiles
These have an optimal growth temp of 80'C or higher and are capable of growing in hot springs and geysers.
dry heat
moist heat
Heat is the most common and economical means of controlling microbial growth. There are two basic types of heat used, ______ ______ and _______ ______.
Dry heat methods
kill microorganisms by denaturing proteins and oxidation (burning) of vital structural and metabolic chemicals.
Direct flaming
Every time you flame the lip of a test tube or flame your loop in lab your are using dry heat method of sterization.
Drying ovens
This circulates hot air, 171'C for 1 hour, or 160'C for 2 hours, are commonly used to sterilize glassware and metal instruments, oils and powders.
used to dispose of contaminated materials in health care facilities, and to stop the spread of infectious disease in cattle or poultry by the ___________ the carcasses of infected animals.
Moist heat methods
kill microbes primarily by denaturing proteins, but they can also damage cell membranes, and nucleic acids.

more penetration than dry heat and consequently can be effective at a lower temp or in less time.
Fractional Sterilization
can be used to sterilize materials using 100'C steam for 30 mins but requires heating the material to be sterilized on 3 successive days and incubation of the material @ 37'C btwn heat treatments.
uses steam heat under pressure and is one of the most reliable means of sterilization. 15 PSI at 121'C for 15 minutes.
Used in processing milk products, fruit juices, beer and wine.

Doesn't result in sterilization, but kills vegetative pathogens and some microorganisms involved in food spoilage.
low-temperature holding


63'C for 30 mins
high-temperature short time

AKA flash method

72'C for 15 secs


raises the temp from 74' to 140'C and rapidly, in less than 5 seconds, lowers the temp back to 74'C.
Ionizing radiation
X rays and gamma rays which are short wavelength, high energy, and very penetrating
Ionizing radiation
Because they are of sufficient energy to knock electrons free of atoms, particularly water molecules, forming ions (free radicals).
Free radicals
_____ _______ formed in this way can cause lethal damage to cells.
Ionizing radiation
also directly impact DNA causing lethal damage.
ionizing radiation
Because no is involved, __________ __________ is also used to sterilize heat-labile products such as plastic syringes and surgical gloves.
Nonionizing radiation
UV light is of longer wavelength than ionizing radiation.
Nonionizing radiation
Wavelengths below 200nm are absorbed by the air and are ineffective in controlling microbial growth except in a vacuum.
UV light

(nonionizing radiation)
___ _______ is most lethal at a wavelength of 260-265nm which corresponds to the wavelength that is absorbed optimally by DNA.
thymine dimers
As energy from UV light is absorbed, adjacent thymine molecules covalently bond to one another. The resulting _________ _______ disrupt both DNA replication and transcription.
damages human tissues causing burns

premature aging of the skin

skin cancer

cause damage to the cornea of the eyes.
Why is UV light in ionizing radiation of limited use?
Does UV light penetrate through most materials?
Do x-rays and gamma rays penetrate through most materials?
used to reduce the number of microbes on surfaces and is used to reduce the concentration of airborne microbes in operating rooms, isolation wards, and areas of food preparation
UV light
Sewage plants are now using this in the treatment of sewage. It significantly reduces the number of microbes in the water.
UV light
Some bacterial cells possess enzymes that allow them to repair the damage done to thier DNA by exposure to ___ _______.
dark repair
light repair (photorepair)
What are the names of the enzymes that are involved in repairing damaged DNA by exposure to UV light?
dark repair
involves an endonuclease that can function without visible light and is able to remove pyrimidine dimers
light repair (photorepair)
involves a pyrimidine dimerase called photoreactivating enzyme which is activated by visible light in the blue and green spectrum.
photoreactivating enzyme
Light repair or photorepair involves a pyrimidine dimerase called _______________ _______ which is activated by visible light in the blue and green spectrum.
substances used on inanimate/nonliving objects to kill or inhibit growth of microorganisms.
antimicrobial substances used on living tissue.
Soaps and Detergents
surfactants (surface active) and act as wetting agents. They decrease surface tension btwn molecules and emulisify (break up) fats and oils.
Soaps and Detergents
poor antimicrobial agents (unless they have an antimicrobial agent added) they work by suspending microorganisms and debris allowing them to be mechanically removed through scrubbing and rinsing.
Quaternary Ammonium Compounds
used as both disinfectant and antiseptics.

common ingredient in mouthwash, contact lens solutions and lab bench disinfection solutions.
tend to be neutralized by soaps and detergents

inactivated by organic matter

readily absorbed by cotton and gauze

support growth of pseudomonas.
What are some disadvantages of Quaternary Ammonium Compounds?
Organic Acids
weak acids are used in eyewash solutions, and used to prevent fungal growth in food and soft drinks.
Heavy metals
The antimicrobial effect of certain metals in very small amounts is termed oligodynamic action.
oligodynamic action
The antimicrobial effect of certain metals in very small amounts is termed _____________ ________.
Thimerosal, a mercury compound, is used to preserve ________.
copper sulfate
_______ _______ is used to control the growth of algae.
Chlorine and iodine
Chlorine bleach
_______ _______ is one of the best cost effective disinfectants available.
________ in the form of iodophores (iodine + detergent) are used as antiseptics and surgical scrubs.
A ________ (an antimicrobial substance combined with alcohol) of iodine is commonly used as a skin antiseptic.
Ethyl and Isoprophyl
denature proteins and act as lipid solvents dissolving cell membranes. This does NOT sterilize.
__________ alcohol acts as a surfactant and is used on the skin to mechanically remove microorganisms from the skin prior to injection or venipuncture.
Carbolic acid
Are not activated by organic matter and can be used effectively on vomits, urine, blood, and fecal matter.
Lysol and Amphyl
What are some phenolic compounds?
Chlorinated phenol
What phenol is used in surgical instruments?
Gaseous Chemosterilizers
Ethylene oxide is used to sterilize: rubber gloves, mattresses, plastics and other heat labile materials.
Oxidizing agents
Hydrogen peroxide disrupts protein structure and is converted to water and oxygen.
Carbolic acid
Are not activated by organic matter and can be used effectively on vomits, urine, blood, and fecal matter.
Lysol and Amphyl
What are some phenolic compounds?
Chlorinated phenol
What phenol is used in surgical instruments?
Gaseous Chemosterilizers
Ethylene oxide is used to sterilize: rubber gloves, mattresses, plastics and other heat labile materials.
Oxidizing agents
Hydrogen peroxide disrupts protein structure and is converted to water and oxygen.
antimicrobial chemotherapy
the use of chemicals to control infection
antimicrobial agents
Microorganisms are becoming increasingly resistant to our first line __________ ______ and some strains are even considered untreatable.
"magic bullet"
something that will specifically target and inhibit or destroy a microbe without harming the host.
True _________ are antimicrobial substances produced by microorganism.
___________ antimicrobial agents are naturally produced molecules that have been chemically modified to make them more effective.
_________ antimicrobial agents are purely manmade. The term _____ is often used of synthetic agents to distinguish them from true antibiotics.
antimicrobial agent
When attempting to treat a patient with an infectious disease a physician needs to make an informed decision concerning which _________ ______ to prescribe.
This susceptibility pattern shows the physician whether the isolate is ________, show __________ resistance, or is __________ (sensitive), to several antimicrobial agents.
patient allergies
toxicity (side effects)
possible interactions with other medications in making a final decision.
After determining which antimicrobial agents the isolate is suseptible to, what other factors will the physician consider?
Kirby-Bauer method
A commonly used, FDA approved, method of determining susceptibility is the _______ _______ _______.
disk diffusion test
Mueller Hinton
The Kirby-Bauer method is a standardized _____ _________ _____. A petri dish containing ________ ________ agar, poured to a uniform thickness of 4mm, is covered with a lawn of the organism to be tested.
antimicrobial agents
Paper disks impregnated with standardized concentrations of various __________ _____ are placed on the agar surface.
zone of inhibition
The plates are incubated and the _____ ___ __________ around each disk is measured and compared to a chart to determine if the organism is resistant, intermediate, or susceptible.
because different antimicrobial agents diffuse through the agar at different rates. One might have a larger zone of inhibition, but less effective. Different diffusion rates for different antimicrobial agents.
Why must we measure the zone of inhibition and compare the outcome to the charts?
Minimum inhibitory concentration
What does MIC stand for?
In the Kirby-bauer method, which organism was the most resistant overall?