Deck 8: Use of Colony Morphology for the Presumptive Identification of Microorganisms

Question 1

Which of the following descriptions will directly facilitate identification of bacteria?

A) Environmental growth temperature
B) Physical characteristics of colony morphology
C) Environmental growth atmosphere
D) Colony color

Answer 1

B

Question 2

Swarming is

A) many bacterial colonies crowded together at one place on the agar plate.
B) when colonies on a BAP have a "halo" around the bacterial colony.
C) when a bacterial colony on a BAP grows over the top of the erythrocytes it hemolyzed.
D) a hazy blanket of growth on the surface of the agar that extends way beyond the streak lines.

Answer 2

D

Question 3

A microbiologist is reading stool culture plates. She sees an organism that has a dry, pink colony with a surrounding "halo" of pink on MAC. What is a good presumptive identification of this organism?

A) Enteric pathogen
B) Escherichia/Citrobacter-like organism
C) Klebsiella/Enterobacter-like organism
D) Haemophilus influenzae

Answer 3

B

Question 4

Colonies of Bacillus anthracis are described as

A) Curschmann's spiral.
B) Mickey Mouse ears.
C) Medusa's heads.
D) flower like.

Question 5

Colony morphology is defined as

A) colony characteristics.
B) colony size and color.
C) colony smell and shape.
D) colony constitution and environmental conditions.

Question 6

The edge of the colonies is described as all the following, except

A) smooth.
B) glasslike.
C) filamentous.
D) irregular.

Question 7

Colonies growing on the SBA have discolored the media to a green color around and under the colonies. This is consistent with which type of hemolysis?

A) Alpha
B) Beta
C) Gamma (no hemolysis)
D) Delta

Question 8

Generally, microbiologists observe the colonial morphology of organisms on primary culture after how many hours of incubation?

A) 18 to 24 hours
B) 6 to 12 hours
C) 24 to 48 hours
D) 72 hours

Question 9

A microbiologist is reading stool culture plates. She sees an organism that has a large, mucoid pink colony on MAC. What is a good presumptive identification of this organism?

A) Enteric pathogen
B) Escherichia/Citrobacter-like organism
C) Klebsiella/Enterobacter-like organism
D) Haemophilus influenzae

Question 10

Gamma ( $\gamma$ )-hemolysis is

A) complete clearing of erythrocytes in a BAP around and under the colony.
B) partial lysing of erythrocytes in a BAP around and under the colony.
C) when organisms have no lytic effect on the erythrocytes in the BAP.
D) a pink "halo" around a colony.

Question 11

Beta ( $\beta$ )-hemolysis is

A) complete clearing of erythrocytes in a BAP around and under the colony.
B) partial lysing of erythrocytes in a BAP around and under the colony.
C) when organisms have no lytic effect on the erythrocytes in the BAP.
D) a pink "halo" around a colony.

Question 12

Alph ( $\beta$ )-hemolysis is

A) complete clearing of erythrocytes in a blood agar plate (BAP) around and under the colony.
B) partial lysing of erythrocytes in a BAP around and under the colony.
C) when organisms have no lytic effect on the erythrocytes in the BAP.
D) a pink "halo" around a colony.

Question 13

The colonies growing on the SBA have produced a wide, deep, clear zone around and under the colonies. This is consistent with which type of hemolysis?

A) Alpha
B) Beta
C) Gamma (no hemolysis)
D) Delta

Question 14

When differentiating colony size on the culture plates, what organisms generally have the larger colonies by comparison?

A) Gram-negative rods
B) Gram-positive cocci
C) Gram-negative diplococci
D) Gram-positive rods

Question 15

When microbiologists set up a biochemical identification using a commercial system on a suspected pathogen from a culture, they must

A) recognize the colony characteristics of the pathogen.
B) observe the culture after 18 to 24 hours of incubation.
C) confirm identification with biochemical tube testing.
D) correlate colony characteristics with the suspected identification of the organism.

Question 16

The relative concentration of bacteria on culture plates is directly proportional to

A) the amount of nutrients in the culture plates.
B) the environment in which the bacteria is grown.
C) the concentration in which they are present in the clinical specimen.
D) the amount of bacteria isolated from the initial inoculation on the plate.

Question 17

An upper respiratory specimen contains many indigenous organisms which may be time consuming, cost prohibitive, and insurmountable. What should the microbiologist do?

A) Work quickly with commercially available kits to identify all organisms present in a sputum specimen for the best quality patient care available.
B) Work up only the gram-negative rods present in the culture.
C) Differentiate the potential pathogens from the "usual" inhabitants of the upper respiratory tract and direct the diagnostic workup only to potential pathogens.
D) Be able to ascertain whether the results generated by a commercial or automated system correlate with the suspected organism.

Question 18

A microbiologist is reading stool culture plates. She is looking for enteric pathogens on the MAC plate. What do they look like?

A) Clear, colorless colonies
B) Large, bright pink colonies
C) Small, mucoid, green colonies
D) Small, orange colonies

Question 19

MacConkey (MAC) agar is used to

A) differentiate between hemolytic and nonhemolytic gram-negative rods.
B) show the clear, pinpoint colonies of Haemophilus influenzae.
C) demonstrate the large, pink colonies of Neisseria meningitidis.
D) differentiate between lactose fermenters and lactose nonfermenters.

Question 20

Plate reading is

A) examining the colonial morphology of bacteria.
B) a comparative examination of bacteria growing on a variety of culture media.
C) setting up biochemical tests to identify bacteria.
D) determining if the inoculum is mixed.

Question 21

All the following colors are commonly used to describe bacteria, except

A) buff.
B) white.
C) orange.
D) gray.

Question 22

What organism forms a small, fuzzy-edged colony with an umbonate center on blood or CHOC agar?

A) Eikenella corrodens
B) Staphylococcus aureus
C) Escherichia coli
D) Streptococcus pyogenes

Question 23

When looking at a tube of thioglycollate broth, streamers or vines and puffballs are visible. What organism grows like this in thioglycollate?

A) Gram-negative rods (Enterobacteriaceae)
B) Streptococcus spp.
C) yeast
D) Pseudomonas spp.

Question 24

The density of the bacterial colony can be described by all the following, except

A) transparent.
B) translucent.
C) opaque.
D) ground glass.

Question 25

The elevation of bacterial colonies is described by all the following, except

A) raised.
B) pointed.
C) convex.
D) umbilicate.

Question 26

A microbiologist is reading a vaginal culture. She sees the very white colonies that are non -hemolytic on a BAP but appear to have feet. What organism could this possibly be?

A) Yeast
B) Gram-positive cocci
C) Gram-negative rods
D) Haemophilus influenzae

Question 27

The term used to describe colonies that are solid in color and that do not allow any light to pass through is

A) opaque.
B) transparent.
C) translucent.
D) ground glass.

Question 28

All of the following terms are used to describe the consistency of a bacterial colony, except

A) brittle.
B) creamy.
C) dry.
D) smooth.

Question 29

A term used to describe colonies that resemble coins is

A) umbonate.
B) flat.
C) umbilicate.
D) raised.

Question 30

All of the following characteristics are used to describe bacterial colony characteristics, except

A) temperature.
B) hemolysis.
C) color.
D) elevation.