Lab Exam 1 Flashcards
why do we label plate media on the agar (bottom) side of the plate
- allows us to see the specimen information while looking at the plate in its proper storage orientation
- lids can be switched between plates
why do we incubate and store plate media with the agar side up (lid side down)
- Condensation dripping disrupts the streaking pattern and cause isolated colonies to merge together
What is the genetic relationship between the cells in a single bacterial colony?
- clones
- Each individual bacterial colony is assumed to have arisen from a single bacterial cell deposited on the agar at that spot.
How is this genetic relationship important for downstream clinical identification procedures?
all bacteria in one colony will have identical morphological and physiological characteristics in our downstream identification procedures
Which part of slide preparation takes the longest?
making the smears on the slides because of the air-drying step.
Staphylococcus aureus colony size
small to med
Staphylococcus aureus colony elevation
raised/slightly convex
Staphylococcus aureus colony consistency/ surface
smooth, dull, opaque
Staphylococcus aureus colony form/shape/margin
round/entire margin
Staphylococcus aureus colony color
grayish cream color, yellow tinge
Staphylococcus aureus colony hemolysis
beta-hemolysis
Staphylococcus saprophyticus colony size
small
Staphylococcus saprophyticus colony elevation
raised/ slightly convex
Staphylococcus saprophyticus colony consistency/surface
slightly mucoid, shiny, opaque
Staphylococcus saprophyticus colony form/shape/ margin
round, entire margin
Staphylococcus saprophyticus colony color
white (often bright)
Staphylococcus saprophyticus colony hemolysis
non-hemolytic
selective component(s) of the MSA plate
7.5% NaCl
what species of Staphylococcus was able to grow on the MSA plate
all staphylococci species are able to grow on MSA plates
differential component(s) of the MSA plate
the mannitol sugar and the phenol red indicator dye
Which species of Staphylococcus was able to ferment the sugar and what species of Staphylococcus was not able to ferment the sugar?
S. aureus can ferment mannitol while S. saprophyticus cannot ferment mannitol.
Which tests that you performed in the lab gave the same results for both Staphylococcus species?
the Gram stain (gram-positive cocci in clusters)
the catalase test (positive)
the oxidase test (negative)
the ability to grow on MSA (evident bacterial growth on the plate)
What are the expected Gram stain results for staphylococci? arrangement?
gram-positive cocci that show a clustering arrangement
Corynebacterium diphtheriae colony size
small
Corynebacterium diphtheriae colony consistency/surface
slightly dry
Corynebacterium diphtheriae colony form/shape/margin
round/slightly convex/entire margin
Corynebacterium diphtheriae colony color
cream/off-white
Corynebacterium diphtheriae colony hemolysis
weak beta hemolysis
Pseudomonas aeruginosa colony size
medium to large
Pseudomonas aeruginosa colony consistency/ surface
silver metallic sheen that is very distinctive
Pseudomonas aeruginosa colony form/shape/margin
irregular, flat, slightly spreading, may be unbonate
Pseudomonas aeruginosa colony color
sliver/metallic
dense grown may be greenish
Pseudomonas aeruginosa colony hemolysis
weak beta hemolysis
selective component(s) of the MAC plate
are bile salts and Crystal violet dye
What component(s) of the MAC medium inhibits gram-positive organisms?
bile salts and Crystal violet dye
differential component(s) of the MAC plate
sugar lactose and the indicator dye neutral red
Based on the KIA results, which sugar(s) can P. aeruginosa ferment?
neither glucose nor lactose
Based on the KIA results, which sugar(s) can C. diphtheriae ferment?
glucose but not lactose
Gram stain results for C. diphtheriae? shape? arrangement?
gram-positive
rods with a characteristic “club” shape
a “palisade” arrangement
Gram stain results for P. aeruginosa? arrangement?
gram-negative rods
“kissing” arrangement
what equipment is used for a sterile workspace
laminar flow hoods
what equipment provides a sterile bench top
Bunsen burner
what can be used instead of a Bunsen burner to sterilize loops/needles
incinerator
true or false: antibiotics can turn a non-selective medium into a selective medium
true
what do selective media contain that inhibits some bacteria from growing
antibiotics
dye
chemical agents
what is differential media based on
bacteria growth characteristics
what are the differential characteristics of a blood agar plate
colony characteristics
hemolysis pattern
what is the cell wall composed of
peptidoglycan
what kind of bacteria has a thick cell wall
gram +
what kind of bacteria have a thin cell wall
gram -
where is the cell wall in gram + organisms
outside the cytoplasmic mmb
where is the cell wall in gram neg organisms
between the inner cytoplasmic mmb and an outer mmb
what kind of bacteria stain purple
gram +
what kind of bacteria stain red
gram -
true or false: gram stain is dependable on starved or weakened bacteria
false
what is the most important step of the gram stain process
decolorization
catalase function
decomposes hydrogen peroxide into O2 and water
purpose of the catalase test
to tell if a bacteria have the enzyme catalase
purpose of the oxidase test
determines if bacteria contain the enzyme cytochrome c oxidase
function of cytochrome c oxidase
aerobic respiration
