What is the role of cultures and gram staining in the diagnosis of lymphangitis?

Updated: Dec 17, 2018
  • Author: Raymond D Pitetti, MD, MPH; Chief Editor: Russell W Steele, MD  more...
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Answer

Blood cultures may reveal that infection has spread to the bloodstream; however, results are rarely positive.

Culture and Gram staining of aspirate from the primary site of infection may help in identifying the infectious organism and in choosing antimicrobials. Some authors recommend aspiration of the leading edge of the infection; others prefer sampling the area of maximum inflammation.

Aspiration is relatively insensitive for diagnosing causative organisms. The low density of pathogens present in the infected tissue results in the low sensitivity of aspiration. Published data from a small, comparative study appear to suggest that aspiration of the area of maximal inflammation may increase the yield of positive cultures.

The threshold sensitivity of Gram staining is approximately 100,000 microorganisms per milliliter, a concentration rarely found in cellulitis or lymphangitis.

Aspiration of the leading edge of maximal inflammation is not thought to be helpful in the acute management of cases of acute lymphangitis but may be helpful with treatment-resistant cases. Aspiration may identify antibiotic-resistant organisms or unsuspected organisms.


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