Gram negative Information and Courses from MediaLab, Inc.

These are the MediaLab courses that cover Gram negative and links to relevant pages within the course.

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CLIA General Laboratory Review
What is the purpose of using methyl alcohol in the gram stain procedure:	View Page

CLIA Microbiology / Serology Review
Which of the following statements about Rickettsia is false:	View Page
Which one of the following statements about Coxiella burnetii is not true:	View Page
Which of the following organisms are gram negative:	View Page
Gram positive organisms	View Page
Which one of the following statement about Campylobactor jejunisp. jejuni is false:	View Page
What is the purpose of using alcohol in the gram stain procedure:	View Page
The red/pink color of the colonies (E. coli) seen on this MacConkey Agar Plate is an indication of:	View Page

Current Topics in Clinical Microbiology
Middle ear damage in cases of S. pneumoniae infections are caused primarily by:	View Page
A Brown and Brenn gram stain was performed on one of the tissue biopsy specimens. Organisms were seen as shown in the photograph. Based on the history and the appearance of the bacteria, the most likely identification is:	View Page
A bacterial isolate that produces pitting of the agar and has a bleach-like odor is probably E. corrodens. Closely related species that must be ruled out include:	View Page

Reading Gram Stained Direct Smears
Match the following:	View Page
Match the following:	View Page
The presence of gram negative intracellular diplococci in a female is diagnostic of gonorrhea.	View Page
Quality Control Smears Quality control smears are stained at the same time as the patient's slides.They must be examined before you examine the patient's slides.If properly stained, the Staphylococcus aureus on the positive control slide will stain blue, or gram positive.The Escherichia coli on the negative control slide will stain red, or gram negative.If these slides are not stained properly, the problem must be resolved and new slides made before the patient specimen is examined.	View Page
The smears used for quality control are: (Choose ALL of the correct answers)	View Page
White blood cells White blood cells also stain gram negative and usually have a segmented nucleus. Their average diameter is about 12 microns.	View Page
Red blood cells Red blood cells are 6-8 microns in diameter and are Gram negative.	View Page
Most background material is Gram negative.	View Page
White blood cells are gram negative.	View Page
Match the Gram stain reaction for each of the following nonbacterial elements.	View Page
Epithelial cells After finding an appropriate field, identify the nonbacterial cells first. Epithelial cells stain gram negative and are easily recognized by their large size and nonsegmented nucleus.	View Page
Identification of bacteria Identification of bacteria in direct smears may be of lifesaving importance. For example, a rapid diagnosis of bacterial meningitis, made after examining a gram stained smear of the patient's cerebrospinal fluid, allows the physician to begin treatment immediately.The appearance of bacteria on gram stained smears is suggestive of a certain species, but identification may not be made on the basis of the stain alone. An exception to this rule is the presence of gram negative intracellular diplococci from a male urogenital specimen, which is presumptive identification of Niesseria gonorrhoeae.In addition, culture results can be correlated with the direct smear report.	View Page
Intracellular bacteria. Sometimes bacteria are present within white cells. In this field, there are gram negative bacteria present within a neutrophil.	View Page
Evaluation of Controls If stains and technique are adequate, S. aureus should be gram positive (blue) and E. coli should be gram negative (pink). If control slides do react appropriately, reliable results cannot be assured for the specimen smears. Check stains and technique and prepare more control smears until proper results are achieved, then remake and stain the new direct smears. If it is impossible to prepare a new smear, the poorly stained smear may still be salvaged. Remove immersion oil from the smear using xylol. Use appropriate procedures and personal protective equipment when using xylol, since it is hazardous chemical. If the smear is underdecolorized, repeat the decolorization and counterstain steps. If the smear is overdecolorized, the slide should be stained again.	View Page
Size and Appearance of Cellular Elements Epithelial cells are larger than white blood cells and red blood cells, and contain a single nucleus. White blood cells (pus cells) usually show a segmented nucleus. Red blood cells are 1/2 to 2/3 as large as white blood cells, contain no nucleus, and are gram negative.Hyphae are gram positive tubular filamentous fungal elements which may show branching or intertwining. Yeast cells are round to oval, often budding, gram positive fungal elements, about the same size as RBCs. They are generally much larger than bacteria.	View Page
Reporting Genital Smears Direct smears read specifically for the presence of gonococci should include a direct reference to gram negative intracellular diplococci.	View Page
Special Considerations for Genital Smears Gram negative cocci which occur in pairs with their adjacent sides flattened, giving them a coffee bean appearance, are typical of the genus Neisseria. Neisseria gonorrhea is commonly found within white blood cells; these organisms must be carefully sought within genital tract specimens, and their presence or absence should be specifically noted in the report.The presence of intracellular gram negative bacilli in a purulent male urethral smear is presumptive evidence of gonococci, but this assumption cannot be made in a female. Beware of other organisms which resemble gonococci but are found extracellularly, such as Acinetobacter lwoffi, which must be distinguished biochemically.	View Page
In a male with a purulent urethral exudate, a presumptive diagnosis of gonorrhea is made by finding gram negative intracellular diplococci in a direct smear of the exudate.	View Page

Reading Gram Stained Smears From Cultures
The staining reaction for yeast is:	View Page
A mixture of Gram positive and Gram negative bacteria may be present within the same field of a slide.	View Page
Gram Positive and Negative Stain Colors Microorganisms that are Gram positive stain blue while those that are Gram negative stain pink.	View Page
Cocci and Rods Notice that Gram positive and Gram negative organisms can be either cocci (round) or bacilli (rod-shaped). A mixture Gram positive and Gram negative bacteria may be present in the same field.	View Page
Please select all the choices below than correctly describe this Gram stained smear.	View Page
Please select all the choices below than correctly describe this Gram stained smear.	View Page
Pair Cell Arrangement This field shows examples of Gram negative bacteria appearing in pairs.	View Page
Please select all the choices below than correctly describe this Gram stained smear.	View Page
Please select all the choices below than correctly describe this Gram stained smear.	View Page
Please select all the choices below than correctly describe this Gram stained smear.	View Page
Gram Negative Bacilli Examples of Gram negative bacilli or rod shaped bacteria are present in this field.	View Page
Please select all the choices below than correctly describe this Gram stained smear.	View Page
Gram Stain The Gram stain provides a fundamental differentiation between types of bacteria. Gram positive bacteria retain the primary stain and are deep violet in color. Gram negative organisms are those that decolorize during the staining process and, after counterstaining, are pink in color. Bacteria have two basic shapes:cocci (round)bacilli (rod-shape)	View Page
Single Cell Arrangement These Gram negative bacteria are in a single cell arrangement.	View Page
Please select all the choices below than correctly describe this Gram stained smear.	View Page

White Cell and Platelet Disorders: Peripheral Blood Clues to Nonneoplastic Conditions
The peripheral blood smear noted in the photograph was held for morophological and clinical review as the total platelet count was 10,000/cumm. Conditions fitting this picture include:	View Page

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