Question 1

When microbiologists encounter a sputum specimen, they know that the upper respiratory tract contains many indigenous organisms and to identify every organism in the culture would be a time-consuming, cost-prohibitive, and insurmountable task.So microbiologists must:

Accepted Answer

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 2

Colonies of Bacillus anthracis are described as:

Accepted Answer

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

Question 3

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

Accepted Answer

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

Question 4

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

Accepted Answer

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

Question 5

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

Accepted Answer

A) recognize the colony characteristics of the pathogen. 
B) observe the culture after 18 to 24 hours of incubation. 
C) use quality control organisms to ensure the identification of the organism is correct. 
D) correlate colony characteristics with the suspected identification of the organism.

Question 6

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

Accepted Answer

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

Question 7

Colonies of Staphylococcus aureus are usually described as:

Accepted Answer

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

Question 8

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

Accepted Answer

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

Question 9

A microbiologist is reading plates from a cerebrospinal fluid (CSF) culture.She notices that there is growth on chocolate agar (CHOC), but no growth on sheep blood agar (SBA) or MacConkey (MAC) agar.The Gram stain showed a gram-negative bacillus.What organism should be suspected?

Accepted Answer

A) Streptococcus pneumoniae 
B) Staphylococcus aureus 
C) Haemophilus influenzae 
D) Escherichia coli

Question 10

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

Accepted Answer

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

Question 11

g-Hemolysis is:

Accepted Answer

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

Question 12

Which organism is described as shiny, like a half-pearl, on media supplemented with horse blood?

Accepted Answer

A) Staphylococcus aureus 
B) Bordetella pertussis 
C) Streptococcus agalactiae 
D) Streptococcus pyogenes

Question 13

A microbiologist is reading the plates from a sputum culture.There is growth only on the chocolate plate.When the microbiologist takes off the lid of the culture plate, he notices a distinct "mousy" smell.What organism can this be?

Accepted Answer

A) Proteus mirabilis 
B) Haemophilus sp. 
C) Staphylococcus aureus 
D) Pseudomonas aeruginosa

Question 14

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

Accepted Answer

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

Question 15

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

Accepted Answer

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

Question 16

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

Accepted Answer

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

Question 17

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

Accepted Answer

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

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