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11157

PHIL Image 11157

ID#:11157
Description:Under a very high magnification of 20,000x, this scanning electron micrograph (SEM) shows a strain of Staphylococcus aureus bacteria taken from a vancomycin intermediate resistant culture (VISA).

Under SEM, one can not tell the difference between bacteria that are susceptible, or multidrug resistant, but with transmission electron microscopy (TEM), VISA isolates exhibit a thickening in the cell wall that may attribute to their reduced susceptibility to vancomycin . See PHIL 11156 for a black and white version of this image. VISA and VRSA are specific types of antimicrobial-resistant staph bacteria. While most staph bacteria are susceptible to the antimicrobial agent vancomycin some have developed resistance. VISA and VRSA cannot be successfully treated with vancomycin because these organisms are no longer susceptibile to vancomycin. However, to date, all VISA and VRSA isolates have been susceptible to other Food and Drug Administration (FDA) approved drugs.

How do VISA and VRSA get their names?

Staph bacteria are classified as VISA or VRSA based on laboratory tests. Laboratories perform tests to determine if staph bacteria are resistant to antimicrobial agents that might be used for treatment of infections. For vancomycin and other antimicrobial agents, laboratories determine how much of the agent it requires to inhibit the growth of the organism in a test tube. The result of the test is usually expressed as a minimum inhibitory concentration (MIC) or the minimum amount of antimicrobial agent that inhibits bacterial growth in the test tube. Therefore, staph bacteria are classified as VISA if the MIC for vancomycin is 4-8g/ml, and classified as VRSA if the vancomycin MIC is >16g/ml.

High Resolution:Right click here and select "Save Target As..." for hi-resolution image (4.69 MB)
Content Providers(s):CDC/ Matthew J. Arduino, DRPH
Creation Date:2001
Photo Credit:Janice Haney Carr
Links:
  • CDC - National Center for Preparedness, Detection, and Control of Infectious Diseases; Division of Healthcare Quality Promotion (DHQP); Frequently Asked Questions: About VISA/VRSA
    Categories:
    CDC Organization

    MeSH
    tree picture Analytical, Diagnostic and Therapeutic Techniques and Equipment
    tree picture tree picture Diagnosis
    tree picture tree picture Equipment and Supplies
    tree picturetree picture tree picture Diagnostic Equipment
    tree picture Diseases
    tree picture tree picture Bacterial Infections and Mycoses
    tree picturetree picture tree picture Bacterial Infections
    tree picturetree picturetree picture tree picture Gram-Positive Bacterial Infections
    tree picturetree picturetree picturetree picture tree picture Staphylococcal Infections
    tree picture Organisms
    tree picture tree picture Bacteria
    tree picturetree picture tree picture Gram-Positive Bacteria
    tree picturetree picturetree picture tree picture Gram-Positive Cocci
    tree picturetree picturetree picturetree picture tree picture Staphylococcaceae
    tree picturetree picturetree picturetree picturetree picture tree picture Staphylococcus
    tree picturetree picturetree picturetree picturetree picturetree picture tree picture Staphylococcus aureus
    Copyright Restrictions:None - This image is in the public domain and thus free of any copyright restrictions. As a matter of courtesy we request that the content provider be credited and notified in any public or private usage of this image.
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    This page last reviewed: Mar. 18 2005
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