30 BASICS
PCR for Dermatophytes (Polymerase Chain Reaction Test)
Rapid test.
Requires very little DNA to be present in the sample.
Not reliable for diagnosing dermatophytosis: very small amount of contaminant DNA
can yield a false-positive result.
Dermatophyte DNA is ubiquitous; it can be found in the soil.
An animal with a positive PCR may have contaminant DNA on the hair coat and not
be a true transient carrier.
Dermatophyte PCR is sensitive but not specific.
BACTERIAL CULTURE
Submit samples to a reference laboratory experienced in the culture, identification,
and sensitivity testing of bacterial organisms of veterinary significance.
Inform the laboratory if you suspect an unusual or a zoonotic organism; obtain infor-
mation regarding laboratory preferences for submission of samples suspected of being
methicillin-resistantStaphylococcusspp.Obtain samples from superficial lesions using sterile swabs.
Excessive debris that may contaminate results should be gently removed with
alcohol-soaked gauze; do not scrub lesions with antiseptic solutions prior to sample
collection.Samples for bacterial culture, identification, and sensitivity testing from the external
and middle ear canals are discussed below and in the relevant chapter.
Samples from Superficial Lesions
Most often used for culture and sensitivity in superficial and deep folliculitis.
Apply sterile submission swab directly to a lesion (Figure 3.7).
Collect sample from within a lesion by needle aspiration and apply to a sterile swab
(Figure 3.8).
Samples may be collected from:
Superficial exudates
Beneath crusts and scabs
Periphery of epidermal collarettes
Pricked pustules.
Samples Obtained from Tissue
Most often used for culture and sensitivity in deep folliculitis and atypical bacterial
infections.
Use sterile biopsy technique.
Place tissue sample on a sterile gauze and remove the epidermis by scalpel (the epi-
dermis may be submitted with additional tissue for histopathologic examination).