15 INTRODUCTION TO MICROBIOLOGY

Question 1

Microbiology laboratory-acquired infections from an aerosol:
a. Occur in persons who are new to the job
b. Can occur from an accidental needle puncture wound
c. Can cause disease with an organism of low infectivity
d. Are associated with improper venting of air in the laboratory setting

Answer 1

d. Are associated with improper venting of air in the laboratory setting

Question 2

Prevention of aerosolization can best be accomplished by:
a. Disinfecting the work areas with a bleach solution
b. Using puncture-proof sharps discard containers
c. Using a biological safety cabinet when working with specimens
d. Discarding all specimen contaminated materials in a biohazard bag

Answer 2

c. Using a biological safety cabinet when working with specimens

Question 3

Media that contain dyes, antibiotics, or other chemical compounds that inhibit certain bacteria while allowing others to grow are called:
a. Enrichment media
b. Differential media
c. Supportive media
d. Selective media

Answer 3

d. Selective media

Question 4

Media that contain factors such as carbohydrates that give colonies of particular organisms distinctive characteristics are called:
a. Enrichment media
b. Differential media
c. Supportive media
d. Selective media

Answer 4

b. Differential media

Question 5

Media that are used to permit the normal rate of growth of most nonfastidious organisms are called:
a. Enrichment media
b. Differential media
c. Supportive media
d. Selective media

Answer 5

c. Supportive media

Question 6

Which of the following is not a selective medium?
a. CNA
b. Thayer-Martin agar
c. Sheep blood agar
d. EMB

Answer 6

c. Sheep blood agar

Question 7

Which of the following is used to promote the growth of gram-negative organisms while inhibiting the growth of gram-positive organisms?
a. MacConkey agar
b. Sheep blood agar
c. Thayer-Martin agar
d. Chocolate agar

Answer 7

a. MacConkey agar

Question 8

Which of the following is used to promote the growth of Neisseria gonorrhoeae and Neisseria meningitidis?
a. MacConkey agar
b. Sheep blood agar
c. Thayer-Martin agar
d. Phenylethyl alcohol agar

Answer 8

c. Thayer-Martin agar

Question 9

Automated microbiology systems have generally been designed to replace:
a. Manual antibiotic susceptibility procedures
b. Manual procedures that are repetitive and that are performed daily on a large number of specimens
c. Manual procedures that are done infrequently but are labor intensive
d. All manual procedures done in the microbiology laboratory

Answer 9

b. Manual procedures that are repetitive and that are performed daily on a large number of specimens

Question 10

The lowest concentration of antimicrobial agent that will visibly inhibit the growth of the organism being tested is known as the:
a. Minimum inhibitory concentration (MIC)
b. Minimum bactericidal concentration (MBC)
c. Agar disk diffusion test
d. Dilution test

Answer 10

a. Minimum inhibitory concentration (MIC)

Question 11

Use of triple sugar iron agar or Kligler iron agar can identify all the following characteristics of members of the Enterobacteriaceae family (common enteric intestinal pathogens) except:
a. Ability to ferment gas from sugars
b. Ability to produce hydrogen sulfide gas
c. Ability to produce ammonia
d. Ability to ferment lactose

Answer 11

c. Ability to produce ammonia

Question 12

Pathogenic Shigella spp. characteristically are:
a. Non–lactose fermenters
b. Lactose fermenters
c. Coagulase positive
d. Oxidase positive

Answer 12

a. Non–lactose fermenters

Question 13

MacConkey agar is quantitatively inoculated with a urine specimen and incubated appropriately. Results are 100,000CFU/mL urine of gram-negative lactose-fermenting organisms. Which of the following would be statistically the most likely organism to cause this urinary tract infection?
a. Escherichia coli
b. Proteus spp.
c. Staphylococcus aureus
d. Klebsiella spp.

Answer 13

a. Escherichia coli

Question 14

What color are gram-negative bacteria after the decolorizing step in the Gram stain method?
a. Purple
b. Red
c. Purple-red
d. Colorless

Answer 14

d. Colorless

Question 15

Which of the following organisms can be recognized by its spreading growth appearance on sheep blood agar?
a. Escherichia coli
b. Proteus spp.
c. Staphylococcus aureus
d. Klebsiella spp.

Answer 15

b. Proteus spp.

Question 16

Urogenital swabs to be cultured for gonococci should be plated onto culture media:
a. Immediately; at the bedside preferably
b. Within 2 hours of collection
c. Within 4 hours of collection
d. Within 24 hours of collection

Answer 16

a. Immediately; at the bedside preferably

Question 17

In culturing a throat specimen for group A β-hemolytic streptococci testing, which of the following media is preferred?
a. Sheep blood agar
b. HE agar
c. MacConkey agar
d. Chocolate agar

Answer 17

a. Sheep blood agar

Question 18

What is the purpose of making cuts in the sheep blood agar when a throat culture is plated?
a. To count the colonies growing after incubation
b. To observe the appearance of any hemolysis present
c. To determine whether the organism is lactose positive or negative
d. To note the morphologic appearance of the colony growth

Answer 18

b. To observe the appearance of any hemolysis present

Question 19

In some people, untreated pharyngitis infections with group A β-hemolytic streptococci can eventually result in:
a. Chronic pyelonephritis
b. Acute pyelonephritis
c. Chronic glomerulonephritis
d. Scarlet fever

Answer 19

d. Scarlet fever

Question 20

In observing a sheep blood agar plate inoculated with a sputum sample showing the presence of alpha or green hemolysis after incubation, what test can be done to determine whether the organism is viridians streptococci, part of the normal respiratory flora, or Streptococcus pneumoniae?

a. Bile solubility test, in which most S. pneumoniae colonies would be dissolved by the reagent used and inhibited by optochin disk
b. Bile solubility test, in which most viridians streptococci colonies would be dissolved by the reagent used and inhibited by optochin disk
c. Bacitracin susceptibility test, in which most S. pneumoniae colonies would be inhibited by the bacitracin disk
d. Bacitracin susceptibility test, in which most viridians streptococci colonies would be inhibited by the bacitracin disk

Answer 20

a. Bile solubility test, in which most S. pneumoniae colonies would be dissolved by the reagent used and inhibited by optochin disk

Question 21

In identifying the presence of most group A β-hemolytic streptococci, versus those that are non–group A, which of the following tests can be done?

a. Bile solubility test, in which most group A β-hemolytic streptococci colonies would be inhibited by an optochin disk
b. Bile solubility test, in which most non–group A β-hemolytic streptococci colonies would be inhibited by an optochin disk
c. PYR test, in which most group A β-hemolytic streptococci colonies would produce a bright-red color after addition of the PYR reagent to the filter paper
d. PYR test, in which most non–group A β-hemolytic streptococci colonies would produce a bright-red color after addition of the PYR reagent to the filter paper

Answer 21

c. PYR test, in which most group A β-hemolytic streptococci colonies would produce a bright-red color after addition of the PYR reagent to the filter paper

Question 22

Wound infections can be classified into three major areas including:
a. Superficial, artificial, and wounds
b. Superficial, subcutaneous, and deep wounds
c. Superficial, folliculitis, and abscess
d. Superficial, burns, and ulcer

Answer 22

b. Superficial, subcutaneous, and deep wounds

Question 23

Which of the following antimicrobial agents is used to inhibit nonpathogenic fungi from growing in media that have been designed to promote growth of pathogenic fungi science Mycosel?
a. Penicillin
b. Streptomycin
c. Chloramphenicol
d. Cycloheximide

Answer 23

d. Cycloheximide

Question 24

A Gram-stained sputum smear shows 40 to 50 squamous epithelial cells per low-power (10×) field, along with gram-positive cocci, many gram-negative rods, and many gram-positive cocci in pairs using the oil-immersion objective. How should the laboratorian report the result for this smear?
a. Call physician directly to report life threatening situation.
b. Report gram-positive cocci, many gram-negative rods, and many gram positive cocci in pairs, as well as many squamous epithelial cells.
c. Subculture must be done to confirm; report pending.
d. No report; request another specimen because this one is contaminated with mouth flora (probably saliva, not sputum), as evidenced by the large number of squamous epithelial cells.

Answer 24

d. No report; request another specimen because this one is contaminated with mouth flora (probably saliva, not sputum), as evidenced by the large number of squamous epithelial cells.

Question 25

“Clue cells” are best seen in which of the following specimens?
a. Wet preparation of vaginal discharge
b. Gram stain of vaginal discharge
c. KOH–wet preparation of vaginal discharge
d. KOH–Gram stain of vaginal discharge

Answer 25

a. Wet preparation of vaginal discharge

Question 26

When antibiotic therapy is needed, specimens for culture and organism identification should be collected:
a. At any time; administration of antibiotics does not affect the tests
b. While the antibiotics are being administered
c. Before the antibiotics have been administered
d. After the antibiotics have been administered

Answer 26

c. Before the antibiotics have been administered

Question 27

If the antibiotic does not inhibit the growth of an organism, the organisms is said to be:
a. Susceptible
b. Sensitive
c. Resistant
d. Intermediate

Answer 27

c. Resistant

Question 28

The best method for finding pinworm organisms in children is:
a. Ova and parasite (O&P) examination
b. Rectal swab
c. Cellophane tape collection
d. Blood

Answer 28

c. Cellophane tape collection

Question 29

What are the requirements for collection of an appropriate specimen for the detection of chlamydia?
a. Examine the collected specimen while it is still fresh, when the organisms are still motile.
b. First use a large swab to remove secretions present, and then use a second swab to collect the specimen.
c. Use the cellophane tape collection procedure on the skin area around the anal opening.
d. Culture at the bedside is preferred, using chocolate agar and sheep blood agar

Answer 29

b. First use a large swab to remove secretions present, and then use a second swab to collect the specimen.

Question 30

What are the requirements for collection of an appropriate specimen for the optimal detection of Trichomonas vaginalis?
a. Examine the collected specimen while it is still fresh, when the organisms are still motile.
b. First use a large swab to remove secretions present, and then use a second swab to collect the specimen.
c. Cleanse the site carefully before any collection is done.
d. Culture at the bedside is preferred, using chocolate agar and sheep blood agar.

Answer 30

a. Examine the collected specimen while it is still fresh, when the organisms are still motile.

Question 31

Collection of fecal samples for identification of intestinal parasites should be done:
a. After radiologic studies using barium sulfate have been completed
b. Before radiologic studies using barium sulfate have been done
c. In the morning, before the patient has bathed, defecated, or urinated
d. Before the onset of an acute phase of the intestinal disease

Answer 31

b. Before radiologic studies using barium sulfate have been done