MIDTERMS: L1 - STREAKING TECHNIQUE

Question 1

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)

Answer 1

Cultivation

Question 2

Survival depends on the availability of essential nutrients and appropriate environmental conditions. T OR F

Answer 2

True

Question 3

First and most important steps required for bacterial identification and characterization.

Answer 3

Ability to select pure (individual) colonies

Question 4

If sufficient inocula for testing can be obtained from the primary media, then subculture is NOT necessary. T or F

Answer 4

True

Question 5

Steps in pour plate method

Answer 5

1. Inoculate an empty plate
2. Add melted nutrient agar
3. Swirl to mix
4. Colonies grow in and on solidified medium

Question 6

Steps in spread plate method

Answer 6

1. Inoculate plate containing solid medium
2. Spread inoculum over surface evenly
3. Colonies grow only on surface of medium

Question 7

For isolation and semiquantitative of bacterial

colonies

Answer 7

Dilution streak technique

Question 8

Plates inoculated for quantitation are usually streaked with a 1:100 or 1:1000 loop. T or F

Answer 8

True

Question 9

Specimens plated quantitatively

Answer 9

Urine culture and tissues from burned patients

Question 10

A technique used to isolate pure strain from a

single species of microorganisms

Answer 10

Streaking

Question 11

1st quadrant: Heavy confluent growth
2nd quadrant: discrete colonies
MOTF

Answer 11

1st true, 2nd false (4th quadrant = discrete colonies)

Question 12

Lawn Streaking Technique is used for antimicrobial susceptibility testing
T or F

Answer 12

True

Question 13

Stab and Streak Method is commonly used for biochemical testing of enteriobacterciae

Answer 13

True

Question 14

Difference between TSI and LIA in terms in stabbing or streaking

Answer 14

TSI - stab streak

LIA - stab streak stab

Question 15

Urase and Citrate medium - stabbing the center

Sulfide Indole Motility medium - zigzag needle

MOTF

Answer 15

Both False (Urease and Citrate - zigzag, SIM - stab the center)

Question 16

Pathogenic bacteria (Mesophilic) - prefer 30 to 45 degree celcius
Skin Pathogens - 30 degree celcius

MOTF

Answer 16

Both T
(Others:
Thermophlies - >40 degree celcius
Psychrophiles - 4 to 20 degree celcius)

Question 17

Most of the incubators in the laboratory are set at what temperature

Answer 17

35 degrees celsius ± 2 degrees celsius - to meet the preferred temperature of most internal human pathogens

Question 18

Plates SHOULD NOT be STACKED in piles of MORE THAN SIX

T or F

Answer 18

True

Question 19

The media should be poured in the petri plates at a

specific temperature usually at ______

Answer 19

45 degree celcius

Question 20

To prevent contamination from moisture during incubation: petri dishes should be placed at

Answer 20

Inverted position

Question 21

Anaerobic cultures are incubated for a longer period, ranges from 3 to 6 days
T or F

Answer 21

True

Question 22

Gram positive bacteria generally produce bigger colonies than gram
negative bacteria
T or F

Answer 22

False - GP produce smaller colonies

Question 23

Relative terms of colony size:

Answer 23

Punctiform or pinpoint, small, medium, large

Question 24

Colony pigmentation of Serratia marcescens and Pseudomonas aeruginosa

Answer 24

SM - RED

PA - GREEN

Question 25

Pseudomonas aeruginosa illustrating the _________ in blood agar plate (BAP)

Answer 25

Metallic sheen and green pigmentation of colonies

Question 26

Brick red pigment of Serratia marcescens which is evident on what agar

Answer 26

MacConkey

Additional info: dditional incubation at room temperature enhances the brick-red pigmentation.

Question 27

Enumerate three colony shape

Answer 27

Form, Elevation, and Margin

Question 28

The edge of the colonies should be observed in the form or margin
T or F

Answer 28

True (Form - smooth, filamentous, rough, or irregular)

Question 29

Colonies of _______on visual examination are described as “medusa heads” because of the filamentous appearnce

Answer 29

Bacillus anthracis

Question 30

The elevation of colonies should be determined by

__________

Answer 30

Tilting the culture plate and looking at the side of the colony

Question 31

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

Answer 31

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

Question 32

Streptococcus pneumoniae produces umbilicate colonies

T or F

Answer 32

True

Question 33

Colony margin (enumerate the types)

Answer 33

Entire or smooth, and irregular

Question 34

To see the differences in the density of colonies, it is useful to look through the colonies while using _______

Answer 34

Transillumination - passing of bright light through the bottom of the plate

Question 35

Translucent colonies allow some light to pass through the colonies and opaque colonies do not
T or F

Answer 35

True

Question 36

Hemolysis is helpful in the presumptive identification of Streptococci and Enterococci
T or F

Answer 36

True

Question 37

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

Answer 37

All True

Question 38

Odor:
S. aureus
P. mirabilis
Nocardia spp.

Answer 38

S. aureus - old sock
P. mirabilis - putrid
Nocardia spp. Freshly plowed field

Question 39

Odor:
P. aeruginosa-
Haemophilus spp. -

Answer 39

P. aeruginosa- fruity or grapelike

Haemophilus spp. - mousy