8.1 Specimen Collection, Media, and Methods

Question 1

The aseptic collection of blood cultures requires that the skin be cleansed with:
A. 2% iodine and then 70% alcohol solution
B. 70% alcohol and then 2% iodine or an iodophor
C. 70% alcohol and then 95% alcohol
D. 95% alcohol only

Answer 1

B. 70% alcohol and then 2% iodine or an iodophor

Question 2

When cleansing the skin with alcohol and then iodine for the collection of a blood culture, the iodine (or iodophor) should remain intact on the skin for at least:
A. 10 seconds
B. 30 seconds
C. 60 seconds
D. 5 minutes

Answer 2

C. 60 seconds

Question 3

What is the purpose of adding 0.025% to 0.050% sodium polyanethol sulfonate (SPS) to nutrient broth media for the collection of blood cultures?
A. It inhibits phagocytosis and complement
B. It promotes formation of a blood clot
C. It enhances growth of anaerobes
D. It functions as a preservative

Answer 3

A. It inhibits phagocytosis and complement

Question 4

A flexible calcium alginate nasopharyngeal swab is the collection device of choice for recovery of which organism from the nasopharynx?
A. Staphylococcus aureus
B. Streptococcus pneumoniae
C. Corynebacterium diphtheriae
D. Bacteroides fragilis

Answer 4

C. Corynebacterium diphtheriae

Question 5

Semisolid transport media, such as Amies, Stuart, or Cary-Blair, are suitable for the transport of swabs for culture of most pathogens except:
A. Neisseria gonorrhoeae
B. Enterobacteriaceae
C. Campylobacter fetus
D. Streptococcus pneumoniae

Answer 5

A. Neisseria gonorrhoeae

Question 6

Select the method of choice for recovery of anaerobic bacteria from a deep abscess.
A. Cotton fiber swab of the abscess area
B. Skin snip of the surface tissue
C. Needle aspirate after surface decontamination
D. Swab of the scalpel used for débridement

Answer 6

C. Needle aspirate after surface decontamination

Question 7

Select the primary and differential media of choice for recovery of most fecal pathogens.
A. MacConkey, blood, birdseed, and Campylobacter (Campy) agars
B. Hektoen, MacConkey, MacConkey-Sorbitol, Campy blood, colistin–nalidixic acid (CNA) agars; Selenite-F broth (SEL)
C. CNA and Christensen urea agars and thioglycollate media
D. Blood, Campy, Mueller-Hinton agars, and thioglycollate media

Answer 7

B. Hektoen, MacConkey, MacConkey-Sorbitol, Campy blood, colistin–nalidixic acid (CNA) agars; Selenite-F broth (SEL)

Question 8

Select the media of choice for recovery of Vibrio cholerae from a stool specimen.
A. MacConkey agar and thioglycollate media
B. Thiosulfate–citrate–bile–sucrose (TCBS) agar and alkaline peptone water (APW) broth
C. Blood agar and SEL broth
D. CNA agar

Answer 8

B. Thiosulfate–citrate–bile–sucrose (TCBS) agar and alkaline peptone water (APW) broth

Question 9

CNA agar is used primarily for the recovery of:
A. Neisseria species
B. Enterobacteriaceae
C. Pseudomonas aeruginosa
D. Staphylococcus aureus

Answer 9

D. Staphylococcus aureus

Question 10

In the United States, most blood agar plates are prepared with 5% or 10% red blood cells (RBCs) obtained from:
A. Sheep
B. Horses
C. Humans
D. Dogs

Answer 10

A. Sheep

Question 11

All of the following are appropriate when attempting to isolate N. gonorrhoeae from a genital specimen except:
A. Transport the genital swab in charcoal transport medium
B. Plate the specimen directly on modified Thayer-Martin (MTM) medium
C. Plate the specimen directly on New York City or Martin-Lewis agar
D. Culture specimens in ambient oxygen at 37°C

Answer 11

D. Culture specimens in ambient oxygen at 37°C

Question 12

Chocolate agar and MTM agar are used for the recovery of:
A. Haemophilus spp. and Neisseria spp., respectively
B. Haemophilus spp. and N. gonorrhoeae, respectively
C. Neisseria spp. and Streptococcus spp., respectively
D. Streptococcus spp. and Staphylococcus spp., respectively

Answer 12

B. Haemophilus spp. and N. gonorrhoeae, respectively

Question 13

Cycloserine–cefoxitin–fructose agar (CCFA) is used for the recovery of:
A. Yersinia enterocolitica
B. Yersinia intermedia
C. Clostridium perfringens
D. Clostridium difficile

Answer 13

D. Clostridium difficile

Question 14

Deoxycholate agar (DCA) is useful for the isolation of:
A. Enterobacteriaceae
B. Enterococcus spp.
C. Staphylococcus spp.
D. Neisseria spp.

Answer 14

A. Enterobacteriaceae

Question 15

Xylose lysine deoxycholate (XLD) agar is a highly selective medium used for the recovery of which bacteria?
A. Staphylococcus spp. from normal flora
B. Yersinia spp. that do not grow on Hektoen agar
C. Enterobacteriaceae from gastrointestinal specimens
D. Streptococcus spp. from stool cultures

Answer 15

C. Enterobacteriaceae from gastrointestinal specimens

Question 16

A sheep blood agar plate is used as a primary isolation medium when all of the following organisms are to be recovered from a wound specimen except:
A. β-Hemolytic streptococci and coagulase-positive staphylococci
B. Haemophilus influenzae and Haemophilus parainfluenzae
C. Proteus spp. and Escherichia coli
D. Pseudomonas spp. and Acinetobacter spp.

Answer 16

B. Haemophilus influenzae and Haemophilus parainfluenzae

Question 17

Prereduced and vitamin K1-supplemented blood agar plates are recommended isolation media for:
A. Mycobacterium marinum and Mycobacterium avium intracellulare
B. Bacteroides, Peptostreptococcus, and Clostridium spp.
C. Proteus spp.
D. Enterococcus spp.

Answer 17

B. Bacteroides, Peptostreptococcus, and Clostridium spp.

Question 18

Which procedure(s) is (are) appropriate for the diagnosis of Chlamydia spp. infections when using genital specimens?
A. Obtain urethral, cervical swabs and urine specimens placed in transport media for the direct detection of antigen or nucleic acid and/or culture
B. Plate onto blood and chocolate agar
C. Inoculate into thioglycollate (THIO) broth
D. Plate onto MTM agar within 24 hours

Answer 18

A. Obtain urethral, cervical swabs and urine specimens placed in transport media for the direct detection of antigen or nucleic acid and/or culture

Question 19

Specimens for virus culture should be transported in media containing:
A. Antibiotics and 5% sheep blood
B. Saline and 5% sheep blood
C. 22% bovine albumin
D. Antibiotics and protein nutrient

Answer 19

D. Antibiotics and protein nutrient

Question 20

Cerebrospinal fluid (CSF) should be cultured immediately, but if delayed, the specimen should be:
A. Refrigerated at 4°C to 6°C
B. Frozen at –20°C
C. Stored at room temperature for no longer than 24 hours
D. Incubated at 37°C and cultured as soon as possible

Answer 20

D. Incubated at 37°C and cultured as soon as possible

Question 21

The most sensitive method for the detection of β-lactamase in bacteria is by the use of:
A. Chromogenic cephalosporin
B. Penicillin
C. Oxidase
D. Chloramphenicol acetyltransferase

Answer 21

A. Chromogenic cephalosporin

Question 22

The breakpoint of an antimicrobial drug refers to:
A. The amount needed to cause bacteriostasis
B. A minimum inhibitory concentration (MIC) of 16 μg/mL or greater
C. An MIC of 64 μg/mL or greater
D. The optimal therapeutic level of drug that is achievable in serum

Answer 22

D. The optimal therapeutic level of drug that is achievable in serum

Question 23

Which of the following variables may change the results of an MIC?
A. Inoculum size
B. Incubation time
C. Growth rate of the bacteria
D. All of these options

Answer 23

D. All of these options

Question 24

According to the Kirby-Bauer standard antimicrobial susceptibility testing method, what should be done when interpreting the zone size of a motile, swarming organism, such as a Proteus species?
A. The swarming area should be ignored
B. The results of the disk diffusion method are invalid
C. The swarming area should be measured as the growth boundary
D. The isolate should be retested after diluting to a 0.05 McFarland standard

Answer 24

A. The swarming area should be ignored

Question 25

Which class of antibiotics is used for the treatment of serious gram-negative infections as well as infections with Mycobacterium tuberculosis?
A. Cephalosporins
B. Penicillins
C. Tetracyclines
D. Aminoglycosides

Answer 25

D. Aminoglycosides

Question 26

Select the medium best suited for the recovery of Y. enterocolitica from a patient with gastroenteritis.
A. Hektoen agar
B. Cefsulodin–irgasan–novobiocin (CIN) agar
C. Blood agar
D. Eosin methylene blue agar

Answer 26

B. Cefsulodin–irgasan–novobiocin (CIN) agar

Question 27

A suspected case of plague requires which of the following procedures to confirm Yersinia pestis?
A. Collection of multiple sets of blood culture specimens
B. Incubation of blood cultures at both 28°C and 35°C
C. Culture aspirates from bubos to MacConkey agar at room temperature
D. All of these options

Answer 27

D. All of these options

Question 28

SITUATION: Abdominal pain, fever, vomiting, and nausea prompted an older male to seek medical attention. A watery stool specimen producing no fecal leukocytes or erythrocytes was cultured, and it grew a predominance of gram-negative fermentative bacilli. The colonies were β-hemolytic on blood agar and cream colored on MacConkey agar. The colonies were both oxidase and catalase positive. What is the most likely identification?
A. Aeromonas hydrophilia
B. Escherichia coli
C. Salmonella spp.
D. Shigella spp.

Answer 28

A. Aeromonas hydrophilia

Question 29

SITUATION: Several attendees of a medical conference in the Gulf coast area became ill after frequenting a seafood restaurant. A presumptive identification of V. cholerae was made after stool specimens from several subjects grew clear colonies on MacConkey agar and yellow colonies on TCBS agar. Which key tests would help eliminate Aeromonas and Plesiomonas spp.?
A. Mannitol fermentation, Na+ requirement
B. Oxidase, motility
C. Oxidase, nitrate
D. Hemolysis on blood agar, catalase

Answer 29

A. Mannitol fermentation, Na+ requirement

Question 30

SITUATION: A group of elementary students became ill after eating undercooked ground beef prepared in the school cafeteria. The suspected pathogen, E. coli serotype 0157:H7, is usually recovered using which of the following media?
A. Xylose lysine deoxycholate agar
B. MacConkey agar
C. MacConkey agar with sorbitol
D. Hektoen agar

Answer 30

C. MacConkey agar with sorbitol