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148 Cards in this Set
- Front
- Back
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septic |
the stuff that causes rotting ex: bacteria, fungi, etc... |
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what is aseptic technique |
use to exclude contaminats |
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what is media |
place where bacteria, etc...can live - is a type of nutrient suspension |
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what are 4 different forms of media |
1. broth (liquid) 2. plate (solid) 3. slant (solid) 4. agar deep (solid) |
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what are the advantages of a broth media |
- easy to transport and low contamination because it's in a tube - fast growth b/c is surrounded by nutrients |
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what are the disadvantages of broth media |
- no sustained growth - no isolaton |
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what are the advantages of a plate media |
- is a solid (contains agar) - high SA - ISOLATION - longer sustained growth - allow us to quantify |
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what are the disadvantages of a plate media |
- contamination
- can dry out overnight and make layer on plate decrease |
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how is slant media different than broth media |
- is in a tube like broth but contains agar, so it is solid - is solidified at an angle - bacteria grows on the surface of the slant |
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what are the advantages of a slant media |
- easy to transport - low contamination - can maintain cultures longer |
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what are the disadvantages of slant mediua |
no isolation |
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how is agar deep media different than a slant media |
- is in a tube and is solid, but is solidified straight up |
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what are the uses of agar deep media |
- used to grow bacteria that may require low oxygen - used to determine MOTILITY - if bacteria not moving, will only grow where needle stabbed into the tube |
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what bacteria contributes to dental carriers |
- Streptococcus mutans or S. sanguinis |
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how does Streptococcus mutans contribute to dental carriers? and how? |
- produces sticky polysaccharides from sucrose how? - S. mutans hydrolyzes (breaks down) sulcrose, a disaccharide - sucrose---> fructose + glucose - glucuse polymerizes to form long chains of dextran, which are sticky carbohydrate chains that surrounds the bacteria - b/c dextran is sticky, it helps bacteria stick to the teeth---> which causes plaque - plaque----> dextran, masses of bacteria, debris that adhere to teeth Fructose? - is fermented into lactic acid---> erodes tooth enamel---> dental carriers |
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features of sugarless candies and gum. can it cause dental carriers? |
- they usually contain sugar alcohols (sorbital, mannitol) - sugar alcohols cannot be converted into dextran so won't have sticky stuff to adhere to bacteria - can be fermented into acid, which can increase tooth erosion |
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snydar agar |
- contains sucrose and bromcresol green (pH indicator) = 7 NEUTRAL---> green < 7 ACIDIC----> yellow > 7 BASIC------> blue other ingredients: yeast extract, NaCl, etc... agar |
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Resident flora |
microbes stay on/in the body of the hose - they colonize on the body in a SYMBIONIC RELATIONSHIP 1. commensalism---> when one organism benefits and the other organism is unaffected 2. mutualism---> both organisms benefits |
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transient flora |
may be on the body for a short period of time, but DO NOT colonize |
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opportunisitc flora |
normally doesn;t harm or cause disease in healthy individuals. however, in certain conditions, it will lead to disease EX: Candida albicans |
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Candida albicans |
- is the number 1 opportunisitc pathogen - is a yeast that causes yeast infections - has the ability to take advantage of the situation. antibiotics can cause yeast infections b/c kills off bacteria and allows yeast to take over |
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what are two general types of media |
- chemically defined - complex media |
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chemically defined media |
exact chemical composition is known - can be expensive - takes a longer time |
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complex media |
- exact chemical composition is going to vary from batch to batch - usually includes nutrient extract ( yeast, beef, peptone, etcc.... extract) EX: Nutrient agar (NAP) Tryptic soy agar (TSA) |
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What is agar? |
- is marine algae extract (no nutrients) - functions as a solidifying agent |
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what are the unique properties of agar? |
- most microbes can;t degrade agar - liquifies at 100 deg. C and stays liquid until 40 deg.C |
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WHAT ARE THE FUNCTIONS OF SOAPS AND DETERGENTS |
- are SURFACTANTS (reduces tension of water) or "wetting agents" - decreases surface tension - surfactants are good for emulsifying fats and oily films - mechnically removes bacteria from skin |
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what is the main ingredient of antibacterial soaps |
triclosan |
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what are the properties of triclosan |
main ingredient in antibacterial soaps - is concentration dependent - |
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if there is a high conc of triclosan, what is the result |
biocide (targets membrane; cytoplasm |
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is there is low conc of triclosan, what is the result |
bacteriostatic (targets Fatty acids |
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how much triclosan does soap contain |
.15- .3% |
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how does triclosan targen FA synthesis |
triclosan binds to the ENR, which participates in FA synthesis - FA are necessary to membrane, which is why considered to be bacteriostatic |
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why does triclosan not effect humans |
humans lack ENR (only found in bacteria) |
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what is the main ingredient in hand sanitizers |
alcohol |
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how is alcohol an effective handwashing agent |
- isopropanol, and ethanol - effective against variety: bacteria, fungi, virus NOT EFFECTIVE AGAINST endospores |
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what is the optimal percent of ethanol in hand sanitizers |
62-70 |
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what does alcohol do to cells |
dentaures proteins and disrupts cytoplasmic membranes |
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why do hand sanitizers not have 100% of alcohol |
because mixed with water gives longer contact time so can be better effective - evaporates too quickly if not mixed with water - denaturing proteins requires water |
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what type of microscope do we use in lab |
compound bright field microscope |
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how many lenses does a compound microscope have and what are they called |
2 lenses 1. objective 2. ocular |
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function of objective lens |
closes to the object (4X, 10X, 40X, 100X) |
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function of ocular lens |
- is the lens that is closes to you eye - is always at 10X |
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What is total magnification |
ocular lens X objective lens |
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bright field |
light passes through the specimen - specimen appears shadowy against a bright background |
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resolution |
clarity of an image |
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limit of resolution |
measurement of how far 2 points must be before the microscope can view them as separate |
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refractive index |
speed of light in a substance |
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refractive index of air |
approx 1 |
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refractive index of oil |
approx 1.5 |
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refractive index of glass |
approx 1.5 |
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why is oil used when at 100X |
oil and glass have same refractive index. therefore, light will not bend because traveling same speed - in the microscope, light is exposed to air so will bend. so put oil on slide so it doesn't bend |
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pure culture |
has a single kind of microbe - required to study microbes |
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what are the 3 methods for dilution? and what are the purposes of it? |
purpose= for ISOLATION 1. streak plate 2. spread plate 3. pour plate |
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streak plate |
- a mixed sample is streaked over a solid media (plate) - bacteria falls off over different areas on the plate ex: quad streak plate |
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spread plate |
- mix sample is diluted - different dilutions are plated on plates; which spreads over the surface---> colonies on a plate PRO: can QUANTIFY |
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pour plate |
- mixed samle is duluted - samples (diluted) are mixed into molten aga and poured into empty petri dish ---> allows colonies/bacteria to be mixed in with media and therefore, bacteria grows on or in the media |
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what information does staining bacteria give us |
- morphology/shape - size - arrangement |
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simple stains |
only 1 reagent used |
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what stains are considered simple stains |
1. direct stain 2. negative stain |
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direct stain |
- stains the bacteria |
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negative stain |
stains the BACKGROUND |
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how do simple stains work? |
- stains are charged colored ions (chromophores) in solution - the dyes can be positive or negative charged |
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positive charged has what type of stain |
- is a BASIC stain - stains bacteria so is a DIrect stain EX: methylene blue, crystal violet |
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negative chared has what type of stain |
- is an ACIDIC stain - stains the background so is used for a NEG stain ex: india ink |
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what charge does the bacteria cell have |
slightly negative charge |
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since bacteria cell wall slightly negative, what kind of stain will stain it |
BASIC STAIN--because is positively charged therefore, ACIDIC stains stain the background, not the bacteria |
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for a direct stain, what steps are necessary |
1. prepare a smear---> thin film of bacteria on the slide 2. Fixed---> in this case, heat fixed 3. add basic stain ( methylene blue, or crystal violet) for about one min 4. rinse with water |
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what is the purpose of heat fixing |
1. kills bacteria 2. adheres bacteria to the slide |
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how is a negative stain prepared? |
1. a drop of a negatively charged stain (india ink) is put on the corner of a slide 2. the culture is mixed into the stain 3. then, it is smeared ("feathered") across the slide * stains the background |
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for what purposes is a negative stain better for in comparison to a direct stain |
- is better to determine morphology of the bacteria b/c there is no heat fixing required. - therefore, bacteria is still alive |
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obligate aerobe |
requires oxygen to grow |
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microaerophiles |
requires low O2, high CO2 |
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anaerobes |
does not use oxygen |
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obligate anaerobe |
cannot tolerate the presence of oxygen |
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what is an example of an obligate anaerobe? |
Clostridium |
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aerotolerant anaerobe |
does not use oxygen, but can tolerate the presence of oxygen |
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facultative anaerobe |
can grow with or without oxygen but prefers it - therefore, grows better with oxygen so uses oxygen |
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reducing media |
contains chemicals that combines with free oxygen---> reduces concentration of oxygen |
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what is a type of reducing media |
fluid thioglycollate medium (FTM) |
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what is FTM? and what does it include? |
stands for fluid thioglycollate medium - is a reducing media - includes: 1. sodium thioglycollate---> reducing agent that combines with oxygen 2. agar (small amount)---> slows down the diffusion of oxygen into the medium 3. resazurin---> oxygen indicator
O2 present= pink 02 absent = colorless |
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A- Jar A= anaerobe |
- anaerobic bags remove oxygen |
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what is the indicator for an A-jar? |
Methylene blue= oxygen indicator O2 present---> BLUE O2 absent----> WHITE (the actual strip) |
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candle jar |
- light a candle in a jar and when oxygen low, flame goes out - provides environment with low oxygen and high CO2 (for microaerophiles) |
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what is a differential stain |
uses more than 1 reagent/dye - allows us to differentiate between various bacteria, or bring out specific structures |
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the gram stain |
- useful for identifying and classifying bacteria - based on bacterial CELL WALL properties - allows us to differentiate between gram (+) and gram (-) |
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what is the bacteria cell wall composed of |
peptidoglycan |
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what is peptidoglycan |
are repeating disaccharides of NAG and NAM, which are linked with peptides |
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what are the differences of gram (+) and gram (-) bacteria? |
GRAM (+): - has SEVERAL layers of peptidoglycan, which are linked together by peptides - contains techoic acid, which keeps the layers together so they don't slip GRAM (-): - has a thin layer of peptidoglycan - contains an outer membrane, which contains LPS (lipopolysaccharide) - lipid A is the part that is actually embedded in the outer membrane |
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for the gram stain, what are some inaccurate results that can occur? |
- destain TOO LONG---> false negative - destain TOO SHORT---> false positive - old cultures----> false negatives because cell wall integrity not that great |
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direct microscopic counts |
- a drop of sample is placed on a special slide (special b/c has a grind on it) and the bacteria are physically counted - both DEAD and ALIVE bacteria are counted - advantage = fast |
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turbidometric methods |
- based on turbity of material in either saline or water solution, and then compared to standard curve - REQUIRES SPECTROPHOMETER - counting DEAD and ALIVE bacteria - the higher the turbity, the higher the absorbance |
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standard plate count |
- want a number of colonies between 30-300 - known volume of diluted samples are placed in a petri dish and then molten nutrient is added - CFU (colony forming units) per mL of sample is determined - requires incubation - only ALIVE bacteria are counted |
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what is the OCD formula |
Original cell density OCD= # of colonies / (amount plated)(dilution of the amount plated) |
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bacteriostatic |
temporarily inhibits growth |
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bacteriocidal |
kills bacteria |
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kirby-baur test |
- is a disk diffusion method |
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what media is used for the kirby baur test |
Mueller-Hinton agar Strict QC: standard pH and standard thickness |
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what are the steps of a kirby baur test (disk diffusion method) |
1. culture inoculately uniformly over a plate 2. disls with various chemical agents placed on surface 3. during incubation, the chemical agent diffiuses from the disk---> may inhibit growth and results in ZONE OF INHIBITION |
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zone of inhibition |
is the surrounding of a kirby baur test disk to determine if bacteria were killed - we do a subculture of this zone to determine if the bacteria is bacteriocidal- or static |
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minimum inhibitory concentration (MIC) |
- the minimum amount of drug required to inhibit growth concentration of drug at the edge of the zone of onhibition |
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features of fungi |
- 2 groups: yeasts and molds - are eukaryotic - can be heterotrophs, saprophytic, pathogenic |
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heterotroph |
must absorb nutrients from the environment |
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saprophytic |
live on dead organic material |
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pathogenic |
can cause fungal infections (mycoses) |
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what are fungi cell walls made out of |
chitin |
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what type of media does fungi prefer |
Sabouraud Dextrose Agar - is low in pH and high in sugar - prevents bacterial growth |
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features of yeast |
- unicellular - round or ovoid shaped - asexual reproduction via BUDDING |
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features of mold |
- multicellular - filamentous hyphae - asexual/sexual reproduction via spores |
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what does it mean to be dimorphic |
can be a yeast and mold - switch is due to environmental cues such as temperature EX: Candida albicans |
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what type of stain is an acid-fast stain? |
differential stain |
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why is acid-fast bacteria referred to as "acid fast" |
because will retain the primary stain even when treated with acid alcohol |
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what do acid-fast bacteria contain in their cell walls |
mycolic acid |
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what is mycolic acid and its function |
-found in the cell walls of acid-fast bacteria - is a waxy lipid that makes cells impermeable to most stains - helps keep mositure in the cell wall so doesn;t dry out - prevents digestion from phagocytes |
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what bacteria are considered acid- fast? |
Mycobacterium and Norcardia: - these include Mycobacterium tuberculosis (TB) - Mycobacterium leprae (leprosy) |
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what are acid fast bacteria first stained with |
carbolfuchsin (is red dye) |
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what counterstain is used for acid fast |
Methylene blue |
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what color results for nonacid fast bacteria |
blue |
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color that results for acid fast bacteria |
red, since mycolic acid is impermeable to methylene blue |
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vegetative bodies |
bacteria that are actively metabolizing |
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what bacteria can produce endospores |
Clostridium, Bacillus species (gram + rods) - C. tetani (tetanus) - C. botulinum (botulism) - B. anthracis (anthrax) - C. difficile (colitis) |
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features of endospores |
- smaller and more compact than vegetative body - thick outer layer of KERATIN - are resistant to drying, heat, detergents, harsh environments, UV - are NOT actively metabolizing |
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bacteria and cold |
cold can inhibit microbial growth
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heat and bacteria |
heat can kill microbes |
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psychrophile |
0-20 deg. C |
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mesophile |
20-40 deg. C |
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thermophile |
50-80 deg. C |
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hyperthermophile |
80 and up |
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what are the standards for dry heat |
171 deg. C for one hour OR 160 deg. C for two hours |
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how does dry heat kill bacteria |
- denatures enzymes - dehydrates microbes - oxidation effects |
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what are the forms of moist heat |
- tyndallization - autoclave - pasteurization - boiling |
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how does moist heat kill bacteria/microbes |
denaturing enzymes |
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standards for pasteurization |
63 deg. C for 30 min (standard) or 72 deg. C for 15 sec or 140 deg C. for 3 sec |
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standards for boiling |
100 deg. C for 15 min |
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what does boiling achieve: disinfecting or sterilization? |
disinfection because kills vegetative bodies but not endospores |
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tyndallization method |
- first form of sterilization (gets rid of all organisms including endospores) - boil at 100 deg.C for 30 min and then incubate overnight at 37 deg. C. REPEAT 3X |
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what does the incubation period in tyndallization method allow |
allows spores to germinate |
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standards for autoclaving |
- uses steam under pressre - MOST EFFECTIVE (STERILIZATION) 121 deg.C for 15 min at 15 psi (pounds sq. inch) |
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the relationship between wavelength and energy |
shorter the wavelength, the greater the energy |
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what are considered ionizing radiation |
X-rays, gamma rays |
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what are non-ionizing radiation |
ultra violet (UV) |
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UVC |
"crazy" 200-290nm - most lethal, biocidal |
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UVB |
" bad" 290-320nm - can also damage DNA |
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UVA |
320-400 nm "alright" - not as readily absorbed; less active on living things |
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limits of UV |
- doesn't penetrate well - affects humans |
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neutrophiles |
6.5-7.5 - most bacteria are this |
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acidophiles |
less than or equal to 6 ex: yeast |
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alkalinophiles |
ph of 8 or greter |
