Just Ask the Expert: How can I obtain optimal results from skin bacterial cultures?
Dr. Bloom welcomes dermatology questions from veterinarians and veterinary technicians.
Please review the recommended protocol for successful bacterial culture of skin and, in particular, skin biopsies. Should we perform a direct culture technique or place the biopsy sample in a sterile tube with saline solution or culture media?
For all of these methods, place the swab in a transport medium, and submit it to the laboratory.
Finally, submitting a crust is also reliable as a culture sample.2 Place the crust into a standard bacterial transport media.
For bacterial culture of a nodule, submit a tissue sample. Surgically prepare the site, and use sterile technique to collect the sample with a 6- or 8-mm punch biopsy. Place the sample in a plain red top tube (not a serum separator tube) along with a few drops of non-bacteriostatic sterile saline solution. Submit the sample, and request a culture from macerated tissue. In patients with nodules or deep pyoderma, be sure to request a culture for aerobic and anaerobic bacteria, atypical mycobacterium, and fungi (e.g. Sporothrix species). At the lab, the sample is removed sterilely and crushed, and the macerated sample is used to inoculate the culture media.
Paul Bloom, DVM, DACVD, DABVP
1. White SD, Brown AE, Chapman PL, et al. Evaluation of aerobic bacteriologic culture of epidermal collarette specimens in dogs with superficial pyoderma. J Am Vet Med Assoc 2005;226(6):904-908.
2. Vaughan DF, Lemarie SL. Comparison of culture and susceptibility results of superficial vs. biopsy specimens in dogs with superficial pyoderma. Vet Dermatol 2008:19(2):106-113.