MIDTERMS: L1 - STREAKING TECHNIQUE Flashcards
The process of growing microorganisms in culture by taking bacteria from the infection site( in vivo environment) and Growing microorganisms in an artificial environment in the laboratory (in vitro)
Cultivation
Survival depends on the availability of essential nutrients and appropriate environmental conditions. T OR F
True
First and most important steps required for bacterial identification and characterization.
Ability to select pure (individual) colonies
If sufficient inocula for testing can be obtained from the primary media, then subculture is NOT necessary. T or F
True
Steps in pour plate method
- Inoculate an empty plate
- Add melted nutrient agar
- Swirl to mix
- Colonies grow in and on solidified medium
Steps in spread plate method
- Inoculate plate containing solid medium
- Spread inoculum over surface evenly
- Colonies grow only on surface of medium
For isolation and semiquantitative of bacterial
colonies
Dilution streak technique
Plates inoculated for quantitation are usually streaked with a 1:100 or 1:1000 loop. T or F
True
Specimens plated quantitatively
Urine culture and tissues from burned patients
A technique used to isolate pure strain from a
single species of microorganisms
Streaking
1st quadrant: Heavy confluent growth
2nd quadrant: discrete colonies
MOTF
1st true, 2nd false (4th quadrant = discrete colonies)
Lawn Streaking Technique is used for antimicrobial susceptibility testing
T or F
True
Stab and Streak Method is commonly used for biochemical testing of enteriobacterciae
True
Difference between TSI and LIA in terms in stabbing or streaking
TSI - stab streak
LIA - stab streak stab
Urase and Citrate medium - stabbing the center
Sulfide Indole Motility medium - zigzag needle
MOTF
Both False (Urease and Citrate - zigzag, SIM - stab the center)
Pathogenic bacteria (Mesophilic) - prefer 30 to 45 degree celcius Skin Pathogens - 30 degree celcius
MOTF
Both T
(Others:
Thermophlies - >40 degree celcius
Psychrophiles - 4 to 20 degree celcius)
Most of the incubators in the laboratory are set at what temperature
35 degrees celsius ± 2 degrees celsius - to meet the preferred temperature of most internal human pathogens
Plates SHOULD NOT be STACKED in piles of MORE THAN SIX
T or F
True
The media should be poured in the petri plates at a
specific temperature usually at ______
45 degree celcius
To prevent contamination from moisture during incubation: petri dishes should be placed at
Inverted position
Anaerobic cultures are incubated for a longer period, ranges from 3 to 6 days
T or F
True
Gram positive bacteria generally produce bigger colonies than gram
negative bacteria
T or F
False - GP produce smaller colonies
Relative terms of colony size:
Punctiform or pinpoint, small, medium, large
Colony pigmentation of Serratia marcescens and Pseudomonas aeruginosa
SM - RED
PA - GREEN
Pseudomonas aeruginosa illustrating the _________ in blood agar plate (BAP)
Metallic sheen and green pigmentation of colonies
Brick red pigment of Serratia marcescens which is evident on what agar
MacConkey
Additional info: dditional incubation at room temperature enhances the brick-red pigmentation.
Enumerate three colony shape
Form, Elevation, and Margin
The edge of the colonies should be observed in the form or margin
T or F
True (Form - smooth, filamentous, rough, or irregular)
Colonies of _______on visual examination are described as “medusa heads” because of the filamentous appearnce
Bacillus anthracis
The elevation of colonies should be determined by
__________
Tilting the culture plate and looking at the side of the colony
Umbonate is described as a depressed center, concave on the inside
Umbilicate is described as having a bulging center and convex on the outside
MOTF
Both False
- Umbilicate is described as a depressed center, concave on the inside
- Umbonate is described as having a bulging center and convex on the outside
Streptococcus pneumoniae produces umbilicate colonies
T or F
True
Colony margin (enumerate the types)
Entire or smooth, and irregular
To see the differences in the density of colonies, it is useful to look through the colonies while using _______
Transillumination - passing of bright light through the bottom of the plate
Translucent colonies allow some light to pass through the colonies and opaque colonies do not
T or F
True
Hemolysis is helpful in the presumptive identification of Streptococci and Enterococci
T or F
True
Alpha hemolysis- partial lysis of RBCs in a BAP around and under the colony that results in a green discoloration of the medium
Beta hemolysis- complete hemolysis of RBCs in a BAP around or under the colony
Gamma hemolysis- no hemolysis
MOTF
All True
Odor:
S. aureus
P. mirabilis
Nocardia spp.
S. aureus - old sock
P. mirabilis - putrid
Nocardia spp. Freshly plowed field
Odor:
P. aeruginosa-
Haemophilus spp. -
P. aeruginosa- fruity or grapelike
Haemophilus spp. - mousy
