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135 Cards in this Set
- Front
- Back
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If anaerobes gain access to sterile body sites, they can become
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opportunistic pathogens
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They cause infections that are usually serious and may be fatal.
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opportunistic pathogens
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Anaerobic infections are usually
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polymicrobic
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occur with a mixture of various aerobic, facultative, and anaerobic organisms
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anaerobic infections
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Most anaerobes are ____ growers
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slow
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is often the key clue that an anaerobe is responsible.
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observation of an infection
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Observations that are possible indicators of an anaerobic infection include
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Foul odor
Gas in the specimen Black discoloration of blood containing exudates |
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In some cases, these methods may help us to make a presumptive ID
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Direct examination methods
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Direct examination methods
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gross appearance of the site, odor, gram stain, fluorescent under long wave UV light
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Purulence
Necrosis Sulfur granules |
Gross appearance of infection site
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Fetid
Putrid |
Odor
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366 nm
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Fluorescence under long wave UV light
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Unique morphologies
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gram stain
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Specimens for anaerobic culture should be exposed to _____ as little as possible during processing.
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oxygen
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At minimum, plating should be done on a _____ media containing Vitamin K and hemin, which supports the growth of anaerobes
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non-selective
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Types of non-selective media
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Brucella blood agar, CDC anerobic blood agar, enriched brain heart infusion blood agar
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Immediately after plating, cultures should be placed in an oxygen-free environment for incubation such as
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Anaerobic jars
Anaerobic bags/pouches Anaerobic chambers |
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Cultures should be incubated for ____ hours before initial observation
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48
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Bacteria are more sensitve to oxygen during the first ___ hours of incubation
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48
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Negative cultures should be held for
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7 days
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Gas-impermeable container
Gas generator Indicator |
contents of anerobic jars, bags, and pouches
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CO2 and hydrogen are produced
Hydrogen combines with oxygen to form H2O An oxygen-free CO2-rich environment is created |
Contents produced when generator is open
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____ indicator is blue when oxidized and white when reduced
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methylene blue
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colored indicator verifies that the proper atmosphere was achieved and maintained
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white
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Preliminary grouping of anerobes can be made using
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gram stain and colony morphology, growth and reactions of diff and selective media, susceptibiliy to antimicrobial disks.
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Obligate anaerobic Gram positive bacilli with the ability to form spores
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Clostridium
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may be located centrally, terminally, or subterminally
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Spores
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Very potent toxin production
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Clostridium
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May be associated with a food-borne gastroenteritis
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Clostridium perfringins
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Produces an alpha toxin which can result in myonecrosis (aka gas gangrene), a severe, life-threatening condition
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Clostridium perfringins
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Strains that produce beta toxin may cause enteritis necroticans, a severe disease of the small bowel that usually occurs in children
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Clostridium perfringins
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Boxcar-shaped Gram positive bacilli
Rare central or subterminal spores |
Gram stain Clostridium perfringins
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Double zone of beta hemolysis
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Growth of Clostridium perfringins
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Lecithinase positive
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Clostridium perfringins
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Causes antibiotic-associated diarrhea
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Clostridium difficile
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Causes pseudomembranous colitis
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Clostridium difficile
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Found in the normal flora of up to 15% of adults and may be present in hospital environments
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Clostridium difficile
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Straight bacilli with short chains
Rare subterminal spores |
gram stain of c. difficile
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Fluoresces yellow-green
Horse-stable odor |
growth of c. difficile
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Mannitol positive
Toxin A & Toxin B may be detected easily using EIA |
c. difficile
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Commonly causes bacteremia associated with neoplasms
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Clostridium septicum
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Most commonly associated with colon cancer or breast cancer
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C. septicum
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Straight or curved with subterminal spores
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gram stain of C. septicum
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Beta hemolytic
Swarms like Medusa heads |
growth of C. Septicum
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Produces the toxin tetanospasmin
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Clostridium tetani
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Tetanospasmin causes the clinical manifestations of tetanus.
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C. tetani
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Toxin blocks inhibitory impulses to the motor neurons, causing spastic paralysis
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C. tetani
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Terminal spores with a tennis racket appearance
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gram stain of C. tetani
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Narrow zone of beta hemolysis
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growth of C. Tetani
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Produces 7 different types of neurotoxin
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Clostridium botulinum
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types of neurotoxins that are principle causes of botulism in humans
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Types A, B, E, & F
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Botulism produces a
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flaccid paralysis
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4 categories of clinical botulism
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food borne, wound, infant, colonization
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Subterminal spores with tennis racket appearance
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Gram stain of Clostridium botulinum
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Beta hemolytic
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Growth of C. botulinum
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Anaerobic Gram positive cocci
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Peptococcus
Peptostreptococcus |
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Anaerobic Gram positive bacilli (no spores
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Actinomyces
Lactobacillus Propionibacterium |
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Anaerobic Gram negative bacilli
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Bacteroides
Prevotella |
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Anaerobic Gram negative cocci
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Veillonella
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Chemical produced by microorganisms that inhibits the growth of other microorganisms
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antibiotic
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Substance that kills or inhibits a microorganism
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antimicrobial agent
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an antimicrobial agent may be:
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synthetic, semisynthetic, natural
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natural antimicrobial agent
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antibiotic
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semisynthetic antimicrobial agent
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chemically modified antibiotic
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synthetic antimicrobial agent
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man made
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synthetic antimicrobial agent
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man made
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Antimicrobial agent that affects bacteria
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antibacterial agent
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Antimicrobial agent that affects bacteria
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antibacterial agent
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Kills the microbe
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bactericidal agent
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Kills the microbe
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bactericidal agent
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Inhibits the growth of the microbe; the host’s immune system kills the microbe
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Bacteriostatic Agent
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Inhibits the growth of the microbe; the host’s immune system kills the microbe
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Bacteriostatic Agent
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The way in which an antimicrobial agent harms a microorganism
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mechanism of action
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The way in which an antimicrobial agent harms a microorganism
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mechanism of action
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Extrachromosomal DNA, which can replicate
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Plasmid
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may carry a variety of antimicrobial resistance genes and can be transferred among organisms
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plasmids
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Antimicrobic is effective in inhibiting bacterial growth
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Susceptible
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Antimicrobic is not effective in inhibiting bacterial growth
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resistant
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Lowest concentration of antimicrobic that inhibits the growth of bacteria in vitro
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minimum inhibitory concentration (MIC)
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Extrachromosomal DNA, which can replicate
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Plasmid
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may carry a variety of antimicrobial resistance genes and can be transferred among organisms
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plasmids
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Antimicrobic is effective in inhibiting bacterial growth
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Susceptible
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Antimicrobic is not effective in inhibiting bacterial growth
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resistant
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Lowest concentration of antimicrobic that inhibits the growth of bacteria in vitro
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minimum inhibitory concentration (MIC)
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Antimicrobic that is effective against both Gram positive organisms AND Gram negative organisms
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broad spectrum
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Antimicrobic that has a limited spectrum of action; usually either Gram positive organisms OR Gram negative organisms
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narrow spectrum.
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Natural resistance of a bacteria to antimicrobics
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intrinsic resistance
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is naturally resistance to novobiocin.
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S. saprophyticus (intrinsic)
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Previous exposure to an antimicrobial agent causes the microbe to become resistant.
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acquired resistance
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Enzymes are produced that inhibit the antimicrobic
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enzyme inactivation
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Antimicrobial agents are unable to reach their target sites
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Permeability Barriers
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Some bacteria can use an energy-dependent system to pump the antimicrobic out of the bacterial cell
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drug efflux
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The drug binds poorly or not at all to its target site
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Low-Affinity Target Sites
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Some organisms can get around the metabolic block created by the antimicrobial agent.
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Bypass Mechanisms
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may occur when an individual is treated with more than one antimicrobial agent
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drug interactions
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the drugs work together, but the effects of neither are amplified
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Additive
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effects if drug interactions are amplified
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synergy
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the drugs are less effective together than one drug alone.
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antagonism
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the drugs neither help nor interfere with each other.
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indifference
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penicillin mechanism of action
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Inhibition of cell wall synthesis
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Penicillin G, penicillin V
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natural penicillin
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Penicillin with side chains
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oxacillin
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Penicillin with side chains and a beta-lactamase inhibitor (clavulanic acid):
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Augmentin, Timentin
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aminoglycoside mechanism of action
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interference with protein synthesis
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aminoglycosides spectrum
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GP and GN
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examples of aminoglycosides
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Gentamicin
Amikacin Streptomycin |
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tetracycline mechanism of action
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Interference with protein synthesis
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Broad spectrum against GP and GN
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tetracycline
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sulfonamides mechanism of action
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Inhibition of folic acid synthesis
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Because the sulfonamides concentrate in the urine, _____ drugs are excellent for treating UTIs
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sulfa
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example of sulfonamides
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Sulfamethoxazole
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glycopeptide mechanism of action
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Inhibition of cell wall formation through inhibition of peptidoglycan synthesis
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gram positive spectrum
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glycopeptides
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example of glycopeptides
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Vancomycin (which treats MRSA
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quinolones mechanism of action
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Inhibition of DNA activity
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example of quinolones
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Fluoroquinolone
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Mechanism of Action : Inhibition of DNA dependent RNA polymerase
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rifampin
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Treats tuberculosis
Given to contact exposure with N. meningitidis |
rifampin
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Superficial skin and mucous membrane infections
Yeast infections |
nystatin
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A standard suspension of bacteria is inoculated onto a Mueller-Hinton plate
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kirby-bauer DDT
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Diameter of zone is directly proportional to the susceptibility of the organism to the antimicrobic
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kirby-bauer DDT
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uses antimicrobial gradient strips
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etest
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etest strips are impregnanted with ___ different dilution of anitmicrobial
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15
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read ___ as the concentration where growth is completely inhibited (etest)
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MIC
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Testing is performed in microtiter trays
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microdilution testing
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a well with broth and no antimicrobic is inoculated. This shows that the organism is able to grow in the broth, under the conditions used
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growth control
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a well with broth and no antimicrobic is not inoculated. No growth should be present
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sterility check
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microdilution testing should include:
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growth control and sterility check
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The concentration of the last well in the row with no visible growth is the MIC
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result of microdilution test
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Testing is performed in microtiter trays
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microdilution testing
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a well with broth and no antimicrobic is inoculated. This shows that the organism is able to grow in the broth, under the conditions used
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growth control
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a well with broth and no antimicrobic is not inoculated. No growth should be present
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sterility check
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microdilution testing should include:
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growth control and sterility check
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The concentration of the last well in the row with no visible growth is the MIC
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result of microdilution test
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Anaerobic infections are usually
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polymicrobic
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