ML: Reading and Reporting Gram-stained Direct Smears Flashcards
Which of these would not be a reason for performing a direct Gram stain on a clinical specimen?
Please select the single best answer
a. Judge the quality of the specimen.
b. Provide the clinician with same-day information regarding possible pathogenic organisms, pending results of culture and sensitivity.
c. Provide internal quality control when direct smear results are compared to culture results.
d. To diagnose N. gonorrhoeae directly from a genital specimen obtained from a child.
d. To diagnose N. gonorrhoeae directly from a genital specimen obtained from a child.
This microscopic field is representative of other fields that were observed on a Gram-stained smear. Which of the following describes the quality of the smear?
Please select the single best answer
a. Under-decolorized
b. Over-decolorized
c. Sufficiently decolorized
d. Cannot be determined
a. Under-decolorized
Feedback: The intense purple color of the background and cellular material (normally pink upon Gram stain) indicates underdecolorization.
Two sputum specimens were submitted to the Microbiology Laboratory for culture. A Gram-stained smear was evaluated for each specimen prior to culturing. The fields that are shown in these images are representative of the 20 - 30 low-power fields that were examined. Which one of the two results represents a sputum specimen that is acceptable for culturing?
a. Gram Stain A
b. Gram Stain B
c. Both A & B
d. Neither A & B
a. Gram Stain A
Feedback: The correct answer is Gram stain A. Gram stain A confirms that the sample was obtained from the lower respiratory tract. There are few if any squamous epithelial cells (SQEs) present and there are many polymorphonuclear cells (PMNs), indicating possible bacterial infection.
Many SQEs are present in Gram stain B, indicating a specimen that is contaminated with oral microflora. If the specimen is determined to be a sub-optimal specimen, the clinician should be contacted and a request should be made for a new specimen. It is important to communicate that culturing the specimen that was provided will not yield useful information about the possible pathogens from the lower respiratory tract.
This Gram stain was prepared from a lower respiratory tract specimen. The field that is shown is representative of 20-30 low power fields that were examined. How should this Gram stain be reported?
a. Gram-negative cocci
b. Gram- positive cocci
c. Many gram- positive cocci in pairs
d. Many gram- positive cocci in pairs, many polymorphonuclear white blood cells (PMNs)
d. Many gram- positive cocci in pairs, many polymorphonuclear white blood cells (PMNs)
Feedback: The correct answer is: This smear is most accurately reported as “Many gram-positive cocci in pairs, many polymorphonuclear white blood cells (PMNs).” It is important to describe the microorganisms that are observed as thoroughly as possible and to report the presence and quantity of host cells that are observed on the smear.
a. Yes, all items are correct
b. No, the cells are not 1 cell thick
c. No, the stain has precipitated, as shown in the bottom left corner
d. No, from this stain alone =, it cannot be determined if it is appropriate for reading
a. Yes, all items are correct
Feedback: The correct answer is all items are correct - the chart is correct. This image represents a Gram-stained smear that is properly prepared and stained. The host cells and background material are stained pink, the cells are evenly distributed (not clumped together), and there is no evidence of precipitated stain.
Which of the following best describes size and staining characteristics of yeast cells on a Gram stain?
a. About the same size as red blood cells/will stain blue
b. About the same size as red blood cells/will stain pink
c. About the same size as white blood cells/will stain blue
d. About the same size as bacteria/will stain pink
a. About the same size as red blood cells/will stain blue
How should the organisms that are indicated by the arrows be reported?
a. gram-negative organisms seen
b. gram-negative cocci
c. Intracellular gram-negative cocci
d. Intracellular gram-negative diplococci
d. Intracellular gram-negative diplococci
Feedback: The correct answer and the most complete report is “Intracellular gram-negative diplococci.” It is important to state that the organisms are located intracellularly. The arrangement in pairs also offers more information than simply stating “cocci.”
The presence of gram-negative intracellular diplococci in a genital specimen from a female is diagnostic of…
a. Moraxella species
b. Neisseria gonorrhoeae
c. Acinetobacter species
d. Not specific enough for diagnosis
d. Not specific enough for diagnosis
Feedback: The correct answer is “not specific enough for diagnosis”. The presence of intracellular gram-negative diplococci on a smear made from a purulent urethral discharge from a male is diagnostic for gonorrhea. However, if the genital specimen is from a female, the presence of gram-negative diplococci is not specific enough to confirm the diagnosis and a culture or other confirmatory testing must be performed. Organisms such as Acinetobacter sp. and Moraxella sp. may mimic the appearance of N. gonorrhoeae and can lead to false-positive results.
Gram-negative cocci that occur in pairs with their adjacent sides flattened, giving them a “coffee bean” appearance (as seen in the image), are typical of which of the following bacteria?
a. Streptococcus pneumoniae
b. Neisseria species
c. Staphylococcus species
d. Micrococcus luteus
b. Neisseria species
Host cells (eg, white blood cells, epithelial cells) will appear as what color on a properly stained Gram stain?
a. Blue
b. Pink
c. Yellow
d. Colorless
b. Pink
