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60 Cards in this Set
- Front
- Back
What is the bacitracin test used for?
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to differentiate beta hemolytic group A strep from other beta hemolytic strep
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In the bacitracin test, inhibition of bacterial growth will appear as what?
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a clearing on the agar plate
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What is the cell target of bacitracin?
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the cell wall
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In the bacitracin test, a zone of clearing 10 mm or greater indicates what?
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bacitracin susceptibility
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What is the novobiacin test most frequently used for?
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to differentiate coagulase negative staph and identify novobiocin resistant staph (UTI causer)
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In the novobiacin test, inhibition of bacterial growth will appear as what?
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a large clearing around the disk.
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In the novobiacin test, a zone of clearing 16 mm or greater indicates what?
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susceptibility
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Why is Staphylococcus saprophyticus significant?
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it causes UTIs in females and it is resistant to novobiocin
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What is the coagulase test used for in the lab?
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differentiate staph aureus from other Gram positive cocci
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What advantage does coagulase production provide to a bacterium?
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it works with normal serum to form fibrin barriers around the bacteria so that they will be shielded from phagocytosis and other types of attack.
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What are the two forms of coagulase?
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Tube test or slide test
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What type of coagulase test did we perform in lab?
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tube test
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What was the fluid used in the coagulase test?
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rabbit plasma
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what is an advantage of the tube test?
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it detects the presence of either bound or free coagulase while the slide only tests for bound
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What was a positive result for the coagulase test performed in the lab?
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thickening or formation of fibrin threads
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What is the definition of carbohydrate fermentation?
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a metabolic process by which an organic molecule acts as an electron donor and one or more of its organic products acts as the final electron acceptor.
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Carbohydrate fermentation tests are especially useful for differentiating what major group of bacteria?
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gram negative bacilli like enterobacteriaceae
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What role does the phenol red play in phenol red broth?
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turns yellow if the pH is below 6.8 and pink if it is above 7.4 and red if it is in between
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What is the purpose of the Durham tube in the phenol red broth?
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it traps gas so we can see a bubble indicative of fermentation
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Why is reading a phenol red broth test after 18 hours of incubation not recommended?
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because of the possibility of reversion :when the organism switches metabolic modes from fermentation to deamination after the exhaustion of carbohydrate
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What is reversion?
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a shift from acid to alkaline because the carbohydrate is exhausted and the organism goes from fermentation to deamination.
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A yellow color in phenol red broth indicates what medium component has been fermented?
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the carbohydrate
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A yellow color in phenol red broth indicates what medium pH?
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below 6.8
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A pink color in phenol red broth indicates what medium component has been catabolized?
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the peptone amino acids
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A pink color in phenol red broth indicates what medium pH?
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above 7.4
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SIM medium is defined broadly as what type of medium?
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a combination medium:a medium which allows multiple tests to be performed in one unit
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What are the 3 test performed by SIM medium?
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sulfur reduction test, indole production test and the motility test
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What does a black precipitate in the butt of a SIM tube indicate?
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is an indication of sulfur reduction and is a positive test
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What does growth only along the inoculum path of a SIM tube indicate?
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that it is positive for motility
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What does hazy growth throughout the SIM medium indicate?
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maybe the presence of ttc??
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What does a pink color in Kovac’s reagent added to a SIM tube indicate?
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a positive reaction and the presence of tryptophanase
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In terms of oxygen environments, what type of environment does H2S production indicate
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anaerobic activity
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What is the Snyder test used for?
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measure dental carries (tooth decay) susceptibilty caused by lactobacilli and oral strep
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What two groups of oral bacteria does the Snyder medium select for?
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lactobacilli and oral strep
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What does a positive Snyder test look like?
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a yellow color
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What is the selective property of the Snyder medium
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a low pH adjusted to 4.8
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What do bile salts do to Streptococcus pneumoniae cells?
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causes them to lyse
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What was the commercial name of the compound used in the disks used to identify S. pneumoniae?
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optochin
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What type of hemolysis does S. pneumoniae produce?
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alpha hemolysis
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What is the Gram reaction of S. pneumoniae
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gram positive
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What is the purpose of the semi-quantitative urine culture?
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determine the concentration of bacteria in a urine sample
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What type of loop is used for a urine culture?
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a volumetric loop
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What two sizes of loops are available for performing urine cultures?
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.001mL and .01mL
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Why do you streak at a 90o angle to the original streak line?
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to evenly disperse the bacteria over the entire plate
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Why would your order this test for one of your patients? (This answer is not in the book).
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to test for a UTI
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What is the β-lactamase test used for?
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to identify if patient isolates are resistant to penicillins and cephalosporins
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For what bacteria is the β-lactamase test especially useful?
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resistant strands of neisseria ghonorrhoeae, staph spp,. and members of genus enterococcus
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What is the molecular mode of action of β-lactam antimicrobials?
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they interfere with bacteria cell wall synthesis
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What is the molecular mode of action of β-lactamase?
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it hydrolyzes the beta lactam ring of the antibiotic
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β-lactamase disks are impregnated with what antimicrobial?
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nitrocefin (a cephalosporin)
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What does a positive β-lactamase test look like?
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a pink spot on the disk
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In the antimicrobial agar disk diffusion test, what are the two reasons for incubating the plate once the test has been set up?
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to allow growth of bacteria and time for the agent to diffuse into the agar
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Why are all the aspects of the antimicrobial agar disk diffusion test standardized?
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to ensure reliable results
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In the antimicrobial agar disk diffusion test, what will you observe if the tested organism is susceptible to an antimicrobial?
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a clear zone around the disk
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What does the acronym “MIC” stand for?
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minimum inhibitory concentration
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What component of the assay is attached to the latex beads?
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antigen or antibody
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What is the marker for detecting the antigen-antibody reaction?
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agglutination (clumps)
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What is a positive test in the latex agglutination test?
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clumping of latex
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What is a negative test in the latex agglutination test?
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no clumping
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What are latex agglutination tests used for in the clinical laboratory?
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to detect pathogen specific antigens and id some bacterial isolates like Staph aureus
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