Deck 41: Laboratory Considerations

Question 1

Optimal recovery and identification of anaerobic bacteria in clinical specimens occurs when

A)the initial incubation period is at 35° to 37° C for 48 hours.
B)plates are incubated for at least 3 days before discarding as negative.
C)the initial incubation period is at 35° to 37° C for 24 hours.
D)thioglycollate broth can be inspected daily for 3 days.

Answer 1

A
Inoculated plates should be immediately incubated under anaerobic conditions at 35° to 37° C for 48 hours. In general, cultures should not be exposed to oxygen until after 48 hours' incubation, because anaerobes are most sensitive to oxygen during their log phase of growth. Also, colony morphology often changes dramatically between 24 and 48 hours.

Question 2

Characteristics that strongly indicate the presence of anaerobes in a clinical specimen include

A)a foul odor.
B)sulfur granules.
C)brick-red fluorescence under long-wavelength ultraviolet (UV) light.
D)All of the above are correct.

Answer 2

D
Characteristics of anaerobes may sometimes be evident in the specimens that contain the organisms. Characteristics that strongly indicate the presence of anaerobes include foul odor; sulfur granules associated with Actinomyces spp., Propionibacterium spp., or Eubacterium nodatum; and brick-red fluorescence under long-wavelength ultraviolet light associated with pigmented Prevotella or Porphyromonas.

Question 3

The ethanol shock or heat shock test will separate which two bacteria?

A)Clostridium perfringens and Clostridium ramosum
B)Clostridium and Bifidobacterium
C)Actinomyces and Bifidobacterium
D)Eubacterium and Eggerthella

Answer 3

B
Of the bacteria listed, the clostridia are the endospore-forming, anaerobic, gram-positive bacilli. If spores are not present on Gram stain, the ethanol shock or heat shock spore test will separate this group from the non-spore-forming anaerobic bacilli.

Question 4

Choose the statement that is most true regarding the identification of anaerobes.

A)Complete identification can be very costly.
B)Complete identification often requires several different testing methods.
C)Most clinical laboratories no longer perform complete identification of anaerobes.
D)Presumptive identification is often just as useful as complete identification.
E)All of the above are correct.

Question 5

In a clinical specimen, sulfur granules strongly indicate the presence of which anaerobe?

A)Actinomyces spp.
B)Propionibacterium spp.
C)Eubacterium nodatum
D)All of the above are correct.

Question 6

Complete identification of anaerobes is

A)relatively inexpensive for the average clinical laboratory.
B)complicated and often requires several different testing methods.
C)performed in most average clinical laboratories.
D)necessary in most cases to ensure adequate treatment.
E)All of the above are correct.

Question 7

The most likely identification of an anaerobic gram-negative coccus is

A)Porphyromonas spp.
B)Veillonella.
C)Leptotrichia.
D)Fusobacterium spp.
E)Bacteroides ureolyticus.

Question 8

The most likely identification of an anaerobic gram-positive bacillus that is a very large fusiform bacillus with one pointed end and one blunt end is

A)Eubacterium.
B)Veillonella.
C)Leptotrichia.
D)Propionibacterium.
E)Lactobacillus.

Question 9

Fecal cultures for isolation of Clostridium difficile are plated on

A)anaerobic blood agar.
B)laked kanamycin-vancomycin blood agar.
C)aerobic 5% sheep blood agar.
D)cycloserine cefoxitin fructose agar.
E)All of the above are correct.

Question 10

The most likely identification of an anaerobic Gram negative bacilli that reduces nitrate and requires formate and fumarate for growth in broth culture is

A)Porphyromonas spp.
B)Bacteroides fragilis group.
C)pigmented Prevotella.
D)Fusobacterium spp.
E)Bacteroides ureolyticus.

Question 11

The media used for culturing a blood specimen for anaerobes may include

A)anaerobic blood agar.
B)Schaedler's broth.
C)5% sheep blood agar.
D)laked kanamycin-vancomycin blood agar.
E)All of the above are correct.

Question 12

The absence of leukocytes in a Gram stain of a clinical specimen

A)rules out the presence of a serious anaerobic infection.
B)may indicate that the causative organism produces necrotizing toxins.
C)may indicate poor transport methods.
D)may indicate excessive exposure to air during specimen processing.

Question 13

The media used for isolating the anaerobic agent of bacteremia may include

A)thioglycollate.
B)Schaedler's broth.
C)thiol broth.
D)None of the above are correct.
E)All of the above are correct.

Question 14

Incubation conditions for anaerobic cultures include

A)30° to 35° C.
B)incubation for 48 hours before exposing to air.
C)incubated for at least 3 days before discarding.
D)incubation of broth medium aerobically with the cap loose.
E)All of the above are correct.

Question 15

The most likely identification of an anaerobic gram-negative bacilli that will fluoresce brick red or has brown to black pigment is

A)nonpigmented Prevotella.
B)Porphyromonas spp.
C)Bacteroides fragilis group.
D)Fusobacterium spp.
E)Bacteroides ureolyticus

Question 16

The most likely identification of kanamycin-sensitive, anaerobic, gram-negative bacilli that will fluoresce a chartreuse color is

A)Fusobacterium spp.
B)nonpigmented Prevotella.
C)Bacteroides ureolyticus.
D)Porphyromonas spp.
E)pigmented Prevotella.

Question 17

The most likely identification of a bile-sensitive, kanamycin-resistant, catalase-negative, and indole-negative anaerobic Gram negative bacilli is

A)nonpigmented Prevotella.
B)Porphyromonas spp.
C)Bacteroides fragilis group.
D)pigmented Prevotella.
E)Bacteroides ureolyticus.

Question 18

The primary plating medium for inoculating anaerobic specimens includes

A)anaerobic blood agar.
B)laked kanamycin-vancomycin blood agar.
C)aerobic 5% sheep blood agar.
D)thioglycollate.
E)All of the above are correct.

Question 19

The most likely identification of a bile resistant, kanamycin, colistin, and vancomycin-resistant anaerobic gram-negative bacilli is

A)nonpigmented Prevotella.
B)Porphyromonas spp.
C)Bacteroides fragilis group.
D)Fusobacterium spp.
E)Bacteroides ureolyticus.

Question 20

The primary plating media for inoculating a wound aspirate for anaerobic culture may include

A)anaerobic blood agar.
B)laked kanamycin-vancomycin blood agar.
C)aerobic 5% sheep blood agar.
D)thioglycollate.
E)All of the above are correct.

Question 21

The most likely identification of an anaerobic gram-positive coccus that is resistant to metronidazole is

A)Streptococcus.
B)Peptostreptococcus.
C)Leptotrichia.
D)Peptococcus.
E)Finegoldia.

Question 22

The most likely identification of an anaerobic, curved, gram-variable bacillus with tapered ends on Gram stain of vaginal secretions when vaginosis is suspected is

A)Porphyromonas spp.
B)Actinomyces.
C)Mobiluncus
D)Fusobacterium spp.
E)Bifidobacterium.

Question 23

Match the description to the most likely identification.
a.Kanamycin, colistin, and vancomycin-resistant and grow in 20% bile
b.bile-sensitive, kanamycin-resistant, catalase-negative and indole-negative
c.fluoresce brick red or brown to black pigment
d.reduces nitrate and requires formate and fumarate for growth in broth culture
e.sensitive to kanamycin and fluoresce a chartreuse color
Porphyromonas spp.

Question 24

Match the description to the most likely identification.
a.Kanamycin, colistin, and vancomycin-resistant and grow in 20% bile
b.bile-sensitive, kanamycin-resistant, catalase-negative and indole-negative
c.fluoresce brick red or brown to black pigment
d.reduces nitrate and requires formate and fumarate for growth in broth culture
e.sensitive to kanamycin and fluoresce a chartreuse color
Fusobacterium spp.

Question 25

Match the description to the most likely identification.
a.Kanamycin, colistin, and vancomycin-resistant and grow in 20% bile
b.bile-sensitive, kanamycin-resistant, catalase-negative and indole-negative
c.fluoresce brick red or brown to black pigment
d.reduces nitrate and requires formate and fumarate for growth in broth culture
e.sensitive to kanamycin and fluoresce a chartreuse color
Nonpigmented Prevotella

Question 26

Match the description to the most likely identification.
a.Kanamycin, colistin, and vancomycin-resistant and grow in 20% bile
b.bile-sensitive, kanamycin-resistant, catalase-negative and indole-negative
c.fluoresce brick red or brown to black pigment
d.reduces nitrate and requires formate and fumarate for growth in broth culture
e.sensitive to kanamycin and fluoresce a chartreuse color
Bacteroides ureolyticus

Question 27

The most likely identification of an anaerobic gram-positive bacillus that produces spores is

A)Bifidobacterium.
B)Eubacterium.
C)Eggerthella.
D)Clostridium.
E)Mobiluncus.

Question 28

Match the description to the most likely identification.
a.Kanamycin, colistin, and vancomycin-resistant and grow in 20% bile
b.bile-sensitive, kanamycin-resistant, catalase-negative and indole-negative
c.fluoresce brick red or brown to black pigment
d.reduces nitrate and requires formate and fumarate for growth in broth culture
e.sensitive to kanamycin and fluoresce a chartreuse color
Pigmented Prevotella

Question 29

Match the description to the most likely identification.
a.Kanamycin, colistin, and vancomycin-resistant and grow in 20% bile
b.bile-sensitive, kanamycin-resistant, catalase-negative and indole-negative
c.fluoresce brick red or brown to black pigment
d.reduces nitrate and requires formate and fumarate for growth in broth culture
e.sensitive to kanamycin and fluoresce a chartreuse color
Bacteroides fragilis group