CAP Pro Course - Microbiology - Organism Detection and Differentiation Using the Gram Stain (2026 & 2027)

Author: Hallee Waye, BS, MLS(ASCP)CM
Reviewer: Laurie Bjerklie, MA, MLS(ASCP)CM

Continuing Education Credits

Objectives

  • Describe and differentiate the procedures used to prepare and perform Gram stains both manually and using an automated stainer.
  • Discuss proper frequency and performance of quality control for Gram stain reagents.
  • Interpret and identify bacterial and non-bacterial elements on direct Gram-stained smears to evaluate specimen quality when appropriate, provide preliminary identification of organisms, and guide culture workup.
  • Differentiate artifacts/questionable elements and identify significant findings seen on Gram-stained smears.
  • Defend the need for stat preparations and timely, accurate reporting of Gram-stained smears, including the specimens and/or the organism types for which this is optimal.

Course Outline

  • Describe and differentiate the procedures used to prepare and perform Gram stains both manually and using an automated stainer.
      • Principle of the Gram Stain
      • Information Provided by a Gram Stain
      • Preparation of a Clinical Specimen or Culture Isolate for Gram Stain
      • Gram Stain Procedure
      • A right leg wound swab from the medical/surgical floor is received for a routine bacterial culture. Which of the following statements about preparing ...
      • Which of the following statements most accurately represents a principle of the Gram stain?
      • A patient is growing gram-positive cocci in their wound and blood cultures. Which of the following is the least likely to demonstrate whether the orga...
      • Which of the following scenarios demonstrates proper preparation of a wound specimen for a Gram stain smear?
      • In a Gram-stained smear, which of the described procedures represents an appropriate process for assessing the quality and determining the best area t...
  • Discuss proper frequency and performance of quality control for Gram stain reagents.
      • Producing Quality Gram Stains
      • Appropriate Quality Control Slides for Reagent Testing and Competency Testing of Personnel Performing Gram Stains
      • Troubleshooting Problem Gram Stains
      • A quality plan developed in the microbiology laboratory must include all quality components. The bench microbiologists provided the following recommen...
      • When developing a quality control procedure, organisms that will exhibit both gram-positive and gram-negative staining characteristics should be inclu...
      • While working on the evening shift, a request for a stat Gram stain is received. Realizing that the bottle of crystal violet is empty, a new batch/lot...
      • Weekly quality control (QC) of the Gram stain reagents currently in use is performed using a known gram-positive and gram-negative organism. When read...
  • Interpret and identify bacterial and non-bacterial elements on direct Gram-stained smears to evaluate specimen quality when appropriate, provide preliminary identification of organisms, and guide culture workup.
      • Evaluating the Quality of Respiratory Samples
      • Sputum Gram Stain Findings
      • Urine Screens
      • Non-Bacterial Elements Encountered on Gram-stained Smears
      • Pathogens Commonly Encountered on Gram Stains by Site/Specimen
      • Pathogens Commonly Encountered on Gram Stains by Site/Specimen, continued
      • Interpretation and Quantitation of Gram Stain Results
      • The aerobic vial of a blood culture set flags as positive. Upon review of the slide, organisms are observed as shown in the image. What is the most li...
      • After reviewing 25 fields of a sputum sample submitted for a routine aerobic culture, you observe an average of 5 squamous epithelial cells (SECs) per...
      • A Gram stain is prepared from an operating room specimen obtained from a brain abscess, as shown in the image. How should this Gram stain be reported ...
      • A Gram-stained smear from an unspun urine sample reveals 1+ polymorphonuclear (PMN) leukocytes and 2+ gram-positive cocci in pairs. Which culture resu...
      • While reviewing the sputum Gram stain from a patient who was admitted with a diagnosis of community-acquired pneumonia, the following is observed. Wha...
  • Differentiate artifacts/questionable elements and identify significant findings seen on Gram-stained smears.
      • Artifacts/Questionable Elements Observed on Gram Stains
      • Significant Gram Stain Findings: Intracellular Organisms
      • Possible Outcomes Suggested by Gram Stain Appearance or Recovery in Certain Specimens
      • While interpreting a Gram stain from a lower extremity skin lesion, the organism depicted in the image is observed. What pathogenicity is most consist...
      • This image was observed on a Gram stain smear from a male urethral specimen. What is the Gram stain reaction, and what is the most likely identificati...
      • What is shown in this Gram stain image (400×) of a bronchoalveolar lavage (BAL) specimen?
      • The Gram stain from the sputum of a 60-year-old male patient who presented to the clinician with a chronic cough that began over a month ago is repres...
  • Defend the need for stat preparations and timely, accurate reporting of Gram-stained smears, including the specimens and/or the organism types for which this is optimal.
      • Specimens for Which Stat Gram Stains are Necessary or Optimum
      • Gram Stain Reporting
      • Timely Reporting of Direct Gram Stains
      • Gram Stain Results From Culture Isolates: When Preliminary Reports are Warranted Before Identification is Complete
      • As seen in the image, this tiny gram-negative coccobacillus was observed in a lymph node Gram stain. What organism should be suspected, and what repor...
      • Certain situations require a preliminary report on a culture isolate before the identification is complete to facilitate patient treatment. In which o...
      • Which sputum Gram stain result requires a phone call to a provider?
      • A stat cerebrospinal fluid (CSF) sample from a 5-year-old male patient in the emergency room is received in the laboratory at midnight. Upon examinati...
  • References
      • References

Additional Information

Level of Instruction: Intermediate
Intended Audience: This program is designed as an educational and training tool for MLS and MLT personnel, medical laboratory science students and interns, pathology residents, and practicing pathologists.
Author Information: Hallee Waye, BS, MLS(ASCP)CM, has over 10 years of experience as a medical laboratory scientist. She has clinical experience in blood bank, microbiology, chemistry, hematology, urinalysis, and coagulation. She currently works as a clinical microbiologist and MLS Program Director for the Parkview School of Medical Laboratory Science in Pueblo, Colorado. She obtained her bachelor’s degree in microbiology from Colorado State University, attended the Colorado Center for Medical Laboratory Science to obtain her professional certificate in medical laboratory science, and completed her master’s degree in clinical laboratory science at the University of Texas Rio Grande Valley.
The author has no conflict of interest to disclose.
Reviewer Information: Laurie Bjerklie, MA, MLS(ASCP)CM, is a Lead Education Developer. She earned a B.S. in Medical Laboratory Science from the University of North Dakota and an M.A. in Curriculum and Instruction from Saint Xavier University. She has over 15 years of experience in higher education and has held program director and faculty positions in both MLT and MLS programs.

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