Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
72 Cards in this Set
- Front
- Back
|
What is the definition of carbohydrate fermentation?
|
The metabolic process by which an organic molecule acts as an electron donor and one or more of its organic products act as the final electron acceptor
|
|
|
Carbohydrate fermentation tests are especially useful for differentiating what major group of bacteria?
|
Gram-Negative bacilli, especially Enterobacteriaceae
|
|
|
What role does the phenol red play in phenol red broth?
|
pH indicator
|
|
|
What is the purpose of the Durham tube in the phenol red broth?
|
Trap gas that may be produced during fermentation
|
|
|
Why is reading a phenol red broth test after 18 hours of incubation not recommended?
|
B/c of the possibility of a reversion ( A reversion is what happens to the medium when an organism switches metabolic modes from fermentation to deamination after the exhaustion of carbohydrate. It’s impossible to visually distinguish b/t a reversion and a true non-fermenter
|
|
|
What is reversion?
|
A reversion is what happens to the medium when an organism switches metabolic modes from fermentation to deamination of peptone amino acids, AFTER the exhaustion of carbohydrate.
|
|
|
A yellow color in phenol red broth indicates what medium component has been fermented?
|
Carbohydrate
|
|
|
A yellow color in phenol red broth indicates what medium pH?
|
<6.8
|
|
|
A pink color in phenol red broth indicates what medium component has been catabolized?
|
peptone amino acids are deaminated
|
|
|
A pink color in phenol red broth indicates what medium pH?
|
>7.4
|
|
|
SIM medium is defined broadly as what type of medium?
|
Combination Medium
|
|
|
What are the 3 test performed by SIM medium?
|
sulfur Reduction Test
Indole Production Test Motility Tes |
|
|
What does a black precipitate in the butt of a SIM tube indicate?
|
indication of Sulfur reduction and a positive test.
Hydrogen Sulfide + Ferric Sulfate Ferric Sulfide (black) H2S (reduced S) + FeSO4 FeS |
|
|
What does growth only along the inoculum path of a SIM tube indicate?
|
Negative motility test. Little to no motility
|
|
|
Negative motility test. Little to no motility
|
Positive Motility test. High Motility
|
|
|
What does a pink color in Kovac’s reagent added to a SIM tube indicate?
|
A positive indole reaction and the presence of Tryptophanase
|
|
|
In terms of oxygen environments, what type of environment does H2S production indicate?
|
Anaerobic
|
|
|
What is the Snyder test used for?
|
The Synder test is designed to measure dental caries(tooth decay) susceptibility
|
|
|
What two groups of oral bacteria does the Snyder medium select for?
|
Lactobacilli & oral Streptococci
|
|
|
What does a positive Snyder test look like?
|
yellow in 24hrs.-highly susceptibility
Yellow in 48hrs.-moderate susceptibility Yellow in 72 hrs-Slight susceptibility Green or Yellow in >72hrs. Negative |
|
|
What is the selective property of the Snyder medium?
|
Selective for bacteria that can survive low pH (~4,8); favors growth of oral bacteria and discourages growth of others
|
|
|
What is the bacitracin test used for?
|
differentiates beta-hemolytic strep pyrogenes from other beta hemolytic strep
|
|
|
In the bacitracin test, inhibition of bacterial growth will appear as what?
|
inhibition of growth will appear as a clearing of the agar plate
|
|
|
What is the cell target of bacitracin?
|
Cell wall inhibition
|
|
|
In the bacitracin test, a zone of clearing 10 mm or greater indicates what?
|
zone greater than 16mm means bacitracin susceptibility
|
|
|
What is the novobiacin test most frequently used for?
|
most frequently used in presumptively identify the novobiacin resistant stap. saprophyticus
|
|
|
In the bacitracin test, inhibition of bacterial growth will appear as what?
|
a clearing
|
|
|
In the bacitracin test, a zone of clearing 10 mm or greater indicates what?
|
Susceptibility
|
|
|
Why is Staphylococcus saprophyticus significant?
|
it is a common urinary tract pathogen seen in sexually active females
|
|
|
What is the coagulase test used for in the lab?
|
used to differentiate staph. aureus from other gram positive
|
|
|
What advantage does coagulase production provide to a bacterium?
|
coagulase shields the bacteria from phagocytosis by forming the fibrin barriers
|
|
|
What are the two forms of coagulase?
|
bound & free coagulase
|
|
|
What type of coagulase test did we perform in lab?
|
tube test
|
|
|
What was the fluid used in the coagulase test?
|
rabbit plasma treated with anticoagulant
|
|
|
for bound and free coagulase, what is an advantage of this test?
|
the tube test can determine bound or free coagulase whereas the slide can only determine bound
|
|
|
What was a positive result for the coagulase test performed in the lab?
|
positive result=clotting
|
|
|
What chemical reaction does catalase carry out?
|
catalase converts hydrogen peroxide into water and gaseous oxygen
|
|
|
What indicates a positive reaction in a catalase test?
|
positive=bubble formation
|
|
|
In terms of oxygen-defined groups, what groups of bacteria produce catalase?
|
Staphylococcus
|
|
|
Why must hydrogen peroxide be converted to water and oxygen in the cell?
|
hydrogen peroxide is toxic
|
|
|
What two medically significant genera does the catalase test help differentiate?
|
micrococcaceae & streptococcaceae
|
|
|
What is the selective agent in mannitol salts agar (MSA)?
|
sodium chloride
|
|
|
What genus does MSA select for?
|
staphylococci (staph. aureus)
|
|
|
What is the pH indicator in MSA?
|
phenol red
|
|
|
What does a yellow color change around a colony signify?
|
pathogenic staphylococcus
|
|
|
What is the β-lactamase test used for?
|
Rapid test for detecting the presence of B-lactamase(an enzyme that can destroy penicillin-class antibiotics)-- (indicating penicillin & cephalosporins resistant microbes)
|
|
|
For what bacteria is the β-lactamase test especially useful?
|
Especially useful in identifying resistant strains of
Neisseria gonorrhoeae, Staphylococccus spp., and members of genus Enterococcus |
|
|
What is the molecular mode of action of β-lactam antimicrobials?
|
The B-lactam ring in the chemical structure of the antimicrobial kills bacteria by interfering with cell wall synthesis
|
|
|
What is the molecular mode of action of β-lactamase?
|
Enzyme produced by bacteria which hydrolyze the B-lactam ring, thus destroying the structure of the antibiotic
|
|
|
β-lactamase disks are impregnated with what antimicrobial?
|
Nitrocefin (a cephalosporin)
|
|
|
What does a positive β-lactamase test look like?
|
it will hyrdolse the nitrocefin Produces pink spot on the disk
|
|
|
What component of the assay is attached to the latex beads?
|
Antigen or antibody
|
|
|
What is the marker for detecting the antigen-antibody reaction?
|
visable aggregate
|
|
|
What is a positive test in the latex agglutination test?
|
clumps of RBC
|
|
|
What is a negative test in the latex agglutination test?
|
nothing happens
|
|
|
What are latex agglutination tests used for in the clinical laboratory?
|
to differentiate the difference between staph and bacterial meningitis
|
|
|
1.What do bile salts do to Streptococcus pneumoniae cells?
|
strep cells are lysed by bile salts
|
|
|
2. What was the commercial name of the compound used in the disks used to identify S. pneumoniae?
|
a. optochin (aka P-disks)
|
|
|
3. What type of hemolysis does S. pneumoniae produce?
|
a. alpha hemolysis
|
|
|
4. What is the Gram reaction of S. pneumoniae?
|
a. gram positive
|
|
|
1. What is the purpose of the semi-quantitative urine culture?
|
a. determining the concentration of the bacteria in urine sample
|
|
|
2. What type of loop is used for a urine culture?
|
a. calibrated loop
|
|
|
3. What two sizes of loops are available for performing urine cultures?
|
a. 0.001mL & 0.01mL
|
|
|
4. Why do you streak at a 90o angle to the original streak line?
|
a. this evenly disperses bacteria over plate
|
|
|
5. Why would your order this test for one of your patients? (This answer is not in the book).
|
a. if patients have the risk for the show symptoms of a urinary tract infection
|
|
|
5. Why would your order this test for one of your patients? (This answer is not in the book).
|
a. if patients have the risk for the show symptoms of a urinary tract infection
|
|
|
In the antimicrobial agar disk diffusion test, what are the two reasons for incubating the plate once the test has been set up?
|
To allow growth of bacteria and time for the agent to diffuse into the agar
|
|
|
Why are all the aspects of the antimicrobial agar disk diffusion test standardized?
|
So that the values read from the chart provide an accurate interpretation of susceptibility or resistance
|
|
|
In the antimicrobial agar disk diffusion test, what will you observe if the tested organism is susceptible to an antimicrobial?
|
A clear zone of inhibition
|
|
|
What does the acronym “MIC” stand for?
|
Minimum Inhibitory Concentration
|
|
|
What type of dilutions was used to prepare the antimicrobial broth dilution test?
|
Broth Dilution Method or Two-fold dilutions
|
|
|
What is the purpose of the antimicrobial broth dilution test?
|
To determine MIC (minimum Inhibitory Concentration) of antimicrobial agent to inhibit bacterial growth
|
