Media Lab "Reading Gram Stained Smears From Cultures"

Can cause gram-negative organisms to stain blue to purple, leading to an erroneous gram-positive result

UNDER-decolorizing Decolorizing is the MOST crucial step affecting the outcome of the stained smear and leading to erroneous results. Under-decolorizing can cause gram-negative organisms to stain blue to purple, leading to an erroneous gram-positive result.

Information obtained from the Gram stained culture smears can allow for a more rapid treatment. true false

Based on the colony characteristics, the Gram stained smear can provide additional information to further confirm initial impressions and guide the microbiologist towards identification. This type of preliminary identification may help the physician to initiate the appropriate antibiotic treatment. As much preliminary information should be provided to the physician as possible.

Which of the following may appear as budding organisms? Please select the single best answer Bacilli Diplococci Rods Yeast

Budding is an asexual reproductive process in yeast. Yeast often demonstrate characteristic "budding" forms which can aid their identification on a direct stained smear. Bacilli, also known as rods, and diplococci do not appear as budding organisms.

When describing microorganisms seen on a Gram stained smear, what do terms such as diplococci, tetrads, chains, and clusters describe? Gram stain reaction Organism shape Cellular arrangement

Cellular arrangement Terms such as diplococci, tetrads, chains, and clusters are used to describe the cellular arrangement of microorganisms. The Gram stain reaction refers to either gram-negative or gram-positive staining. Some organisms may also stain in a gram-variable manner. Organism shapes, such as cocci or rods, are also important observations noted when reading a Gram stained smear.

Which of the following terms can be used to describe cocci? (Choose all that apply.) Rod-shaped Round Budding Oval

Cocci are true spheres that demonstrate a perfectly round shape. However, some cocci will appear slightly oval in shape. While some cocci may also be lancet shaped, they do not appear as rods. Budding is an asexual reproductive process in yeast.

Small, palisading gram-positive rods demonstrating a picket-fence arrangement

Corynebacterium species are small, palisading GPRs demonstrating a "picket-fence" arrangement.

Which of the following is NOT a bacterial arrangement that can be observed on a Gram stained smear? Clusters Singles Tetrads Flowering

Flowering is not an observed bacterial arrangement on Gram stained smears. The cellular arrangement of microorganisms observed on a Gram stained smear can include: Single cells Pairs Tetrads Chains Clusters Budding cells

Which of the following statements are TRUE for the gram-positive control smear? (Choose all that apply.) The positive control organism is typically Escherichia coli The positive control organism is typically Staphylococcus aureus The staining reaction is pink to red The staining reaction is blue to deep purple

For a gram-positive control smear, S. aureus can be used and should stain blue to deep purple. Quality control must be performed to ensure proper staining of patient samples. The organism E. coli is often used as the gram-negative control smear. The stain should appear pink to red in color.

Gram stains from a sterile body site, such as cerebrospinal fluid (CSF), would typically exhibit more than one morphotype (such as Gram negative rods, Gram positive cocci, and Gram positive rods) in a single smear. True False

Generally, only 1 morphotype is expected in sterile body sites, such as CSF, blood, or a joint fluid.

A new batch of Gram stain reagents have been placed into use, so a control slide is used to verify the intended reactivity. Along with the control slide, a Gram stain is also performed on a smear made from a patient culture. The control slide is read first and BOTH control organisms have stained gram-positive (blue to deep purple). What is the BEST course of action prior to reading and reporting the patient results? Prepare and stain ONLY another control slide Prepare and stain BOTH a new control slide AND patient slide Proceed to read and report the patient slide

Gram stained control slides using known gram-positive and gram-negative organisms must be used to verify intended reactivity before examining and reporting patient smears. The positive control should stain blue to dark purple and the negative control should stain pink to red. Control slides serve as a quality control (QC) mechanism for staining reagents and techniques. If the expected outcome is not obtained, prepare and stain both a new control slide and patient slides. If only a new control slide is made, the patient results reported may be erroneous. When the control slide does not stain properly (demonstrates both blue to dark purple AND pink to red organisms), this is an indication that either there is a problem with the staining reagents, the procedure wasn't performed properly, or a combination of the two. Therefore, if the control slide didn't stain as expected, the patient slide also cannot be expected to have stained properly. If the control slide does not stain properly, the problem must be resolved and new slides (both control and patient) made before patient specimens are examined and reported.

Which of the following is TRUE of the Gram stain procedure? Used to distinguish between aerobic and anaerobic organisms Organism morphology is MOST characteristic in smears prepared from 18- to 24-hour broth subculture Gram-positive organisms demonstrate a bright orange fluorescence Gram-negative organisms stain blue to dark purple

It is true that organism morphology is MOST characteristic in smears prepared from 18- to 24-hour broth subculture. Although Gram stain preparation from colonies growing on an agar surface can be less characteristic, it is an extremely important part of the identification process. The Gram stain is used to distinguish between gram-positive and gram-negative organisms, not aerobic and anaerobic organisms. Gram-positive bacteria retain the primary stain and are blue to deep purple in color. Gram-negative organisms are those that decolorize during the staining process and, after counterstaining, are pink to red in color.

When reading the Gram stain of a DIRECT smear, the presence of characteristic cellular arrangements is helpful in providing information as to the organisms that are present. Reporting these cellular arrangements is an important component of the report. However, the arrangement of bacterial cells in a Gram stained smear prepared from a CULTURE should be noted, but not usually reported. True False

It is true that organisms observed on a direct Gram-stained smear should be reported with as much description as possible. In addition to the staining reaction, the shape and cellular arrangement of microorganisms should be reported. This is usually reported from a smear that is made from a direct smear rather than from culture media. Depending on the culture medium (liquid or solid) used to isolate the organism, certain cellular arrangements may not be noted. The Gram stain morphology is often less characteristic when smears are prepared from colonies growing on the agar surface. The arrangement of bacterial cells may still prove helpful, especially for isolates recovered from broth.

Should stain pink to red, like gram-negative rods

Known organism used as NEGATIVE Gram stain control; For QC, the Gram stain manufacturer's product insert will state the organism name and American Type Culture Collection (ATCC) strain number that is recommended. The negative control should be a known organism that stains pink to red. Escherichia coli (gram-negative rod) is commonly used.

Should stain blue to dark purple, like gram-positive cocci

Known organism used as POSITIVE Gram stain control; The positive Gram stain control should be a known organism that stains blue to dark purple, such as Staphylococcus aureus (gram-positive cocci).

Reactivity verified with every new batch of stain and at least weekly against known gram-positive and gram-negative control organisms

Minimum quality control (QC) requirement for Gram stained smears; At a minimum, the intended reactivity of the Gram stain must be verified with every new batch of stain and at least weekly against known gram-positive and gram-negative control organisms. However, individual laboratories may have more stringent requirements. No matter what the required frequency for QC testing, if you prepare and read Gram stains infrequently it would be helpful to stain quality control slides at the same time as a patient Gram stain smear.

Gram-negative diplococci with adjacent sides flattened (coffee bean shaped)

Neisseria species are gram-negative diplococci with adjacent sides flattened (coffee bean shaped).

Branching, long, thin filamentous gram-positive rods; tend to stain with a beaded, gram-variable pattern

Nocardia species appear as long, thin, branching filamentous gram-positive rods (GPRs) that tend to stain with a beaded, gram-variable pattern.

Can cause gram-positive organisms to stain pink to red, leading to an erroneous gram-negative result

OVER-decolorizing Over-decolorizing can cause gram-positive organisms to stain pink to red, leading to an erroneous gram-negative result.

Gram-positive cocci in clusters and tetrads

Staphylococcus species are seen as gram-positive cocci (GPC) in clusters and tetrads.

All of the shapes below can be used to describe cocci EXCEPT for which of the following? Ovoid Lancet Round Tapered

Tapered is not a term used to describe cocci, but rather the ends of bacilli. There are various terms used to describe cocci found on direct stained smears. Some of the more common descriptions include oval or ovoid, lancet, and round.

When performing a Gram stain from culture media, which of the following must ALWAYS be reported for the organism? (Choose all that apply.) Shape Size Stain reaction Cellular arrangement

The Gram stain reaction and bacterial shape of the organism must always be included in the report. The cellular arrangement is usually not included in the report since it may vary depending on the culture medium (liquid or solid) used to isolate the organism. For certain organisms, the size of the organism may be "described" as tiny, large, and so on, but is an optional element. Always report based on the procedure of your laboratory.

Bacilli can have tapered or rounded ends. True False

The ends of rod-shaped organisms can be rounded, squared off, tapered, or sharply pointed.

This organism is recovered from the sputum of a patient with hospital acquired pneumonia (HAP). Which of the options below would be used to describe the Gram stained smear? (Choose all that apply.) Gram-positive Gram-negative CocciBacilli (rods)

The slides shows gram-negative rods (GNRs) which were subsequently identified as E. coli. HAP is often caused by GNRs.

The type of culture medium used to recover an organism does NOT have an effect on cellular arrangement. True False

The type of culture medium does indeed have an effect on cellular arrangement. When performing a Gram stained smear from culture, the cellular arrangement is usually NOT included in the report since it may vary depending on the culture medium (liquid or solid) used to isolate the organism.

The preferred preparation for a Gram stain`

Thin smear The thickness of the smear is what determines the degree of decolorization that is necessary and will ultimately affect the Gram stain result. It is preferable that slides for Gram stain be thinly prepared, without areas of clumping or inconsistency.

Which of the following are part of the microorganism identification process? Arrangement of bacterial cells Size of the organism Shape of the organism Staining reaction All of the above

When a culture shows signs of growth, the process of identification includes examining the following characteristics: Appearance of the colonies in the culture medium Staining reaction Appearance of stained organisms, including the: Size Shape Arrangement of bacterial cells

Which of the following describe how the ENDS of rod-shaped bacteria may appear? More than one answer is correct. Please select all correct answers Budding Tapered Filamentous Rounded

When describing rod-shaped bacteria, the terms "tapered ends" or "rounded ends" may help to identify the type of bacteria present. The term budding frequently describes yeast, but not rod-shaped bacteria. Filamentous may describe the fine, slender, or thread-like appearance of certain bacteria such as Nocardia, but is not used to describe the ENDS of rod-shaped bacteria.

What is the Gram stain reaction for yeast? Please select the single best answer Gram-negative Gram-positive

Yeast cells will stain gram-positive in Gram stained smears.

The bacteria on BOTH the positive and the negative control slides are observed to stain pink. This finding will NOT affect the rest of the slides in the batch. True False

false- Control slides serve as a quality control (QC) mechanism for staining reagents and techniques. For Gram stains, the positive control slide should stain blue to dark purple. If both slides stained pink, it is an indication of a problem with technique (over-decolorization) and/or the reagents. If control slides do not stain properly, the problem must be resolved and new slides made before patient specimens are examined and reported.

A physician can use the information provided from a Gram stained culture smear to help make a preliminary diagnosis and begin treatment. True False

true- The information provided by a Gram stained smear from culture may help the physician to initiate the appropriate antibiotic treatment. As much preliminary information should be provided to the physician as possible.