Deck 8: Presumptive Identification

Question 1

A microbiologist performs a Gram stain on a positive blood culture bottle. She does not observe any organisms. She then uses an acridine orange stain and observes the organisms pictured in the image. What type of microscope did she use to observe the rod-like organisms?

A) Brightfield
B) Darkfield
C) Phase contrast
D) Fluorescent

Answer 1

Fluorescent

Question 2

This image of the spirochete Treponema pallidum was photographed using a _____________ microscope.

A) brightfield
B) darkfield
C) phase contrast
D) fluorescent

Answer 2

darkfield

Question 3

Which of the following microscopes requires that the specimen be stained to observe microorganisms and cells?

A) Fluorescent
B) Phase contrast
C) Darkfield
D) Electron

Answer 3

Fluorescent

Question 4

The eyepiece of a brightfield microscope contains the ___________ lens.

A) objective
B) ocular
C) condenser
D) diaphragm

Question 5

All of the following play a role in setting Köhler illumination of a brightfield microscope except

A) stage.
B) substage condenser.
C) field diaphragm.
D) iris diaphragm.

Question 6

The purpose of Köhler illumination is to

A) ensure adequate resolution.
B) ensure uniform illumination.
C) neither a nor b.
D) both a and b.

Question 7

Setting a brightfield microscope up for Köhler illumination must be repeated for each

A) slide read.
B) day of use.
C) objective.
D) co-worker.

Question 8

At the end of the day, you are the last to use the brightfield microscope. Before leaving you will

A) wipe the microscope down.
B) remove oil from the 100X objective.
C) reset it for Köhler illumination.
D) leave it as is for the next shift.

Question 9

A brightfield microscope should be thoroughly maintained at least

A) weekly.
B) monthly.
C) biannually.
D) annually.

Question 10

You cannot find material on a Gram stained cerebrospinal fluid slide to focus on using the 10X objective. You should

A) turn the slide over. It is upside down.
B) reset the microscope for Köhler illumination and refocus.
C) raise the condenser to allow more light on the slide.
D) focus on the frosted end of the slide and then move to the specimen area.

Question 11

The light bulb on the brightfield microscope burns out. You replace it and it burns out again when you turn on the light. This can be due to

A) electrical surge from the outlet.
B) incorrect bulb wattage.
C) rheostat that is set too high.
D) broken electrical cord.

Question 12

Select the correct combination of stain and microscope to detect the capsule of the yeast Cryptococcus neoformans.
$\begin{array}{lr} \text {\quad \quad Stain } & \text {\quad\quad\quad Microscope } &\\\end{array}$

A) $\begin{array}{lr} \text {saline wet prep } & \text { phase contrast } &\\\end{array}$
B) $\begin{array}{lr} \text {auramine O } & \text {\quad\quad fluorescent } &\\\end{array}$
C) $\begin{array}{lr} \text {iodine wet prep } & \text { brightfield} &\\\end{array}$
D) $\begin{array}{lr} \text {India ink } & \text {\quad\quad\quad brightfield} &\\\end{array}$

Question 13

The acid fast stains Ziehl-Neelsen and Kinyoun can be differentiated by the

A) use of heat to facilitate stain penetration in the Ziehl-Neelsen method.
B) use of heat to facilitate stain penetration in the Kinyoun method.
C) the use of carbolfuchsin for the Ziehl-Neelsen method.
D) the use of carbolfuchsin for the Kinyoun method.

Question 14

Review the Gram stain image of a cerebrospinal fluid. Based on the results, you should

A) look at a drop of the specimen under a darkfield microscope.
B) prepare a new slide and perform a Kinyoun stain.
C) prepare a new slide and perform an acridine orange stain.
D) report the slide as "no organisms seen."

Question 15

Review the Gram stain image provided of a positive blood culture bottle. It should be

A) pleomorphic gram-positive coccobacilli.
B) gram-positive cocci in pairs and chains.
C) gram-positive cocci in clusters.
D) palisading gram-negative cocci.

Question 16

Review the image of a leg wound culture provided. The organisms appear as gram-variable rods. What Gram stain reaction should be reported for this organism?
Source: CDC and Dr. George Lombard

A) Gram negative
B) Gram positive
C) Gram variable
D) Gram positive and gram negative

Question 17

Based on the colonies observed in the image provided, you can deduce the organism

1) is a gram-negative rod.
2) is a gram-positive coccus.
3) produces a capsule.
4) produces a pigment.

A) 1, 3, and 4
B) 2, 3, and 4
C) 2 and 4
D) 1 and 3

Question 18

Partially lysed red blood cells under and around a colony on sheep blood agar appear as

A) no change in the agar.
B) a clear zone.
C) a green discoloration.
D) a blue discoloration.

Question 19

Review the Gram stained urine image provided. Which organism listed best correlates with this Gram stain reaction?

A) Beta-hemolytic, catalase negative, and PYR positive
B) Beta-hemolytic, catalase and coagulase positive
C) Gamma-hemolytic, swarmer, oxidase, and spot indole negative
D) Alpha-hemolytic, catalase negative, and bile soluble

Question 20

A positive blood culture vial reveals gram-negative rods. After subculture, the organism grew as
Sheep blood agar: large, gray colonies with beta-hemolysis
MacConkey agar: round, smooth, pink colonies
Phenylethyl alcohol agar: no growth
Rapid testing revealed
Oxidase: no color change
Pigment: none observed
Spot indole: red-pink
The organism is

A) Escherichia coli.
B) Pseudomonas aeruginosa.
C) Proteus mirabilis.
D) Proteus vulgaris.