The challenges of diagnosing fungal infections

According to Domenico Santoro, DVM, MS, DrSc, PhD, DACVD, DECVD, DACVM, associate professor at the University of Florida College of Veterinary Medicine, and service chief of dermatology in the Department of Small Animal Clinical Sciences, the main challenge when diagnosing fungal infections is actually making an accurate diagnosis. In this interview, Santoro emphasizes the importance of culturing to identify the causative agents of the infection. He also talks about the polymerase chain reaction (PCR) technique and when this technique may offer a more effective diagnostic approach than a culture.

Below is the interview transcript, which has been lightly edited for clarity

Domenico Santoro, DVM, MS, DrSc, PhD, DACVD, DECVD, DACVM: The most common challenge that we see in diagnosing fungal infections is actually making an accurate diagnosis. And the reason is because sometimes it's not easy to identify these organisms as a causative agent of the disease that we see. Sometimes even with Malassezia—so for yeast dermatitis—sometimes we have [a] hard time identify[ing] [it] due to... a secondary issue....

With dermatophytes, it’s even a bit more complicated just because...the diagnosis is based on multiple types of techniques and specifically done by the identification of the fungi after culture. And if we do not do a culture, at times it can be kind of tricky, ...again, to figure out if [it] is a causative agent or not.

Other techniques may involve a [polymerase chain reaction] (PCR) for example, but the PCR may not necessarily identify that the dermatophyte is a causative agent. At times it is not able to differentiate live organisms from dead organisms. So even monitoring the therapy, it can be complicated through PCR, so that's why the culture is the best way.

There are also other more uncommon fungal infections, or fungal-like infections, like pythiosis, for example, which a PCR of the tissue can be a more sensitive diagnostic. So it really matters what type of fungal infection we are targeting and...suspecting in our patients.