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The page below is a sample from the LabCE course Sexually Transmitted Bacterial Infections (by ASCLS). Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Laboratory Diagnosis of Chancroid

Chancroid lesion stained with gentian violet
  • Gram stain of clinical specimens may show characteristic chains of gram negative rods--"schools of red fish"
  • Culture ulcer lesion material and/or bubo aspirates
    • Culture only about 80% sensitive
    • Inoculate at the bedside onto 2 media:
    • Gonococcal agar supplemented with 2% bovine hemoglobin and 5% fetal calf serum, 1% IsovitaleX supplement
    • Mueller-Hinton agar supplemented with 5% chocolatized horse blood, 1% Isovitalex supplement and 3 µ/mL of vancomycin
    • Culture Incubation: 5% CO2 in a humid environment at 33°C to 35°C (critical that the temperature does not exceed 35°C)
  • Culture very difficult
    • Labs seldom have media on hand
    • Organism dies rapidly outside the body
    • No commercially available FDA-approved tests for antigen detection, serology or NAAT
  • Gram stain of colonies shows gram negative coccobacilli
  • Produces characteristic yellowish tan colonies: very adherent and can be pushed intact over the agar surface
  • Oxidase positive
  • Requires X factor