Erysipelas laboratory findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Luke Rusowicz-Orazem, B.S.

Laboratory tests are not usually performed for Erysipelas; physical examination is usually sufficient for diagnosis. However, certain laboratory tests may be performed on Erysipelas patients, including those used to confirm streptococcal infection. Erysipelas patients may display markers for inflammation, such as leukocytosis.

Laboratory tests are not usually performed for Erysipelas; physical examination is usually sufficient for diagnosis. However, certain laboratory tests may be performed on Erysipelas patients, including those used to confirm streptococcal infection. An epidermal swab of affected region may provide samples of pathogenic streptococci, including Streptococcus pyogenes. Erysipelas laboratory findings include identification tests to determine the exact species of streptococcal infection.

• An epidermal swab of affected region may provide samples of pathogenic streptococci, including Streptococcus pyogenes^[1]
  • Streptococci will usually be grown on agar media to produce β-hemolysis for subsequent identification and specification.
  • Streptococcus pyogenes will display as smooth, white-grey domes surrounded by β-hemolysis.
    • They will be arranged in chain formation as Gram-positive cocci when examined microscopically.
  • Catalase testing will confirm that the isolates obtained through the culture swab represent streptococci infection.

• Erysipelas laboratory findings include identification tests to determine the exact species of streptococcal infection.
  • The Lancefield antigen test will determine the specific antibodies produced by the β-hemolytic streptococcal infection, allowing classification into group A, B, C, or G streptococcus.
  • The Pyrrolidonyl Arylamidase (PYR) test is used to determine if the infection is Streptococcus pyogenes by testing for confirmed presence of pyrrolidonyl aminopeptidase
  • Bacitracin susceptibility testing is used as a next subsequent measure of specifying the streptococcal strain when PYR test results are positive, separating Streptococcal pyogenes from other β-hemolytic strains.
    • Results of bacitracin sensitivity indicate positive Streptococcal pyogenes test results.^[2]

• • Erysipelas patients may display markers for inflammation, such as leukocytosis^[3], determined by the following tests:
    • Erythrocyte sedimentation rate
    • C-reactive protein

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