Deck 7: Cultivation of Microorganisms

Question 1

An obligate aerobe is best isolated on the surface of solid medium because

A) it may grow poorly when embedded in a pour plate.
B) solid medium allows for accurate colony counting.
C) it will not survive when added to liquid medium at 45 to 50°C.
D) pour plates are difficult to prepare.

Answer 1

it may grow poorly when embedded in a pour plate.

Question 2

Sheep blood agar is classified as

A) enriched general purpose.
B) differential
C) selective.
D) both a and b.

Answer 2

both a and b.

Question 3

Which of the following media is differential but not selective?

A) MacConkey agar
B) Chocolate agar
C) Thayer-Martin agar
D) None of the above
E) A and C

Answer 3

None of the above

Question 4

A physician orders a culture for Neisseria gonorrhoeae on a vaginal swab. Which of the following categories of media must be included to ensure this organism's recovery from the normal flora present?

A) Differential
B) Selective
C) General purpose
D) Both a and b

Question 5

LIM broth enhances the growth of group B Streptococcus from vaginal and rectal swabs of pregnant females. This is an example of a/an _____________ medium.

A) enriched
B) transport
C) enrichment
D) differential

Question 6

Reducible media used for the recovery of anaerobes is best stored at

A) 4°C.
B) 25°C.
C) 30°C.
D) 35 to 37°C.

Question 7

When preparing sheep blood agar, the red blood cells are added

A) before sterilization of the base agar suspension.
B) immediately after sterilization of the base agar suspension.
C) when the sterilized base agar suspension reaches 55 to 60°C.
D) once the sterilized agar base begins to gel.

Question 8

Campylobacter species can grow at 4°C and 42°C. This organism is categorized as a

A) psychrophile.
B) mesophile.
C) thermophile.
D) both a and b.

Question 9

A microaerophilic atmosphere is composed of

A) 5% oxygen, 10% carbon dioxide, and 85% nitrogen.
B) 21% oxygen, 0.03% carbon dioxide, and 78% nitrogen.
C) 5% carbon dioxide, 10% hydrogen, and 85% nitrogen.
D) 15% oxygen, 3% carbon dioxide, and 82% nitrogen.

Question 10

An organism that grows on media incubated in carbon dioxide but not in ambient air or anaerobically is considered

A) an obligate aerobe.
B) capnophilic.
C) a facultative anaerobe.
D) microaerophilic.

Question 11

The direct Gram stain of expectorated sputum reveals 30 squamous epithelial cells per low power field. You should

A) process the specimen.
B) call the respiratory therapist for an induced specimen.
C) reject the specimen and request another one.
D) process with the physician's approval.

Question 12

A cervical swab was transported to the microbiology department in an anaerobic transport tube. You should

A) process the specimen if there are no squamous epithelia cells on the Gram stain.
B) process because it is an unrecollectable specimen.
C) process the specimen for isolation of Neisseria gonorrhoeae.
D) reject the specimen and request another one.

Question 13

You are placing inoculated agar plates in the incubator for a co-worker. You are holding BAP, MAC, PEA, and HE agar plates. The original specimen is

A) genital.
B) stool.
C) anaerobic wound.
D) superficial wound.

Question 14

Which of the following specimen types/body sites warrants the addition of a thioglycolate broth in addition to routine plated media?

A) Cerebrospinal fluid collected via a shunt
B) Middle ear aspirate
C) Cervical swab for group B Streptococcus
D) Rectal screen for vancomycin-resistant Enterococcus species

Question 15

A throat swab is inoculated onto a sheep blood agar and then a rapid direct test for Streptococcus pyogenes is performed. The rapid strep test is negative. When streaking the agar plate, you should

A) flame the loop before beginning the final quadrant.
B) flame the loop after completion of all quadrants.
C) stab the agar in the area of the initial specimen placement after completion of the final quadrant.
D) both b and c.
E) all of the above.

Question 16

A bacterial culture of a urine specimen requires a _________ for inoculation of the agar plates.

A) swab
B) pipette
C) calibrated loop
D) platinum wire loop

Question 17

The blood agar plate of a urine specimen shows 100 colonies of a large gray wet beta-hemolytic organism. The MacConkey agar displays 20 colonies of a dark pink lactose fermenter. Both organisms are E. coli. How do you account for the difference in the number of colonies between the two agar plates?

A) E. coli grows much better on sheep blood agar than on MacConkey agar.
B) There is a dilution effect as the agar is struck so there will be fewer colonies from agar to agar.
C) The technologist did not redip the loop into the urine before inoculation of the MacConkey.
D) The technologist did not flame the calibrated loop after inoculation of the blood agar plate.

Question 18

Given the following specimen types/body sites, which one should you process first?

A) Cerebrospinal fluid
B) Blood culture
C) Cervical swab for Neisseria gonorrhoeae
D) Lung biopsy for anaerobic culture

Question 19

Given the following set of culture media and procedure, identify the organism you are most likely attempting to isolate: Chocolate agar, Thayer-Martin agar, and Gram stain.

A) Haemophilus ducreyi
B) Haemophilus influenzae
C) Neisseria gonorrhoeae
D) Moraxella catarrhalis

Question 20

The consistency of medium containing 0.3 to 0.4% agar will be

A) liquid.
B) semisolid.
C) solid.