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Journal of Microbiology & Biology Education Volume 8, 2007


Sixteen New Visual Resources


Two New Curriculum Resources

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American Society
    for Microbiology,
    Washington DC

Printable Version
Examination of Gram Stains of Urine
Resource Type: Visual: Image
Publication Date: 2/6/2007
Slide 1

Escherichia coli (Enlarged view)
Slide 2

Proteus mirabilis (Enlarged view)
Slide 3

Citrobacter diversus (Enlarged view)
Slide 4

Acinetobacter baumanii (Enlarged view)
Slide 5

Lactobacillus species (Enlarged view)
Slide 6

Staphylococcus saprophyticus (Enlarged view)
Rebecca Buxton (Corresponding Author)
Department of Pathology
University of Utah
Salt Lake City, Utah 84132

These images are from the original published atlas: Tenover, F. C., and J. V. Hirschmann. 1990. Interpretation of Gram stains and other common microbiologic slide preparations. The UpJohn Company, Kalamazoo, Mich. Permission granted to the ASM MicrobeLibrary by Pfizer Inc.
This atlas was written to help clinicians, microbiologists, and laboratory personnel identify organisms in infected materials stained by techniques commonly used in most clinical laboratories. Please refer to the atlas' main page for more information and a guide to all of the images.

Gram stains of urine specimens that have not been centrifuged can help determine the cause of a suspected urinary tract infection. If bacteria are present under an oil immersion lens (1,000x), the concentration is at least 104 or 105 bacteria per milliliter. Since the concentration of bacteria in most patients with symptomatic urinary tract infections is that high, the Gram stain will usually, but not always, be positive.
Slide 1. Escherichia coli
This Gram stain shows neutrophils and numerous plump, gram-negative bacilli that vary little in size or shape.

Slide 2. Proteus mirabilis
These short to medium-long gram-negative bacilli look like typical enteric gram-negative bacteria; isolation of Proteus mirabilis confirmed that impression.

Slide 3. Citrobacter diversus
These short, slender gram-negative bacilli look like enteric bacteria. The culture grew Citrobacter diversus.

Slide 4. Acinetobacter baumanii
Some of the short, fat, pleomorphic gram-negative bacilli resemble cocci, others diplococci. The variety of shapes is typical of this organism, which can be confused with Neisseria species.

Slide 5. Lactobacillus species
These long, slender gram-positive bacilli are part of the normal vaginal flora. Their presence in a urine specimen suggests that improper technique in its collection resulted in contamination with vaginal secretions.

Slide 6. Staphylococcus saprophyticus
These gram-positive cocci in clusters look like staphylococci. Various species of coagulase-negative staphylococci, especially Staphylococcus saprophyticus, can cause urinary tract infections, particularly in young women.