Increasing recognition of methicillin-resistant Staphylococcus pseudintermedius (MRSP) in veterinary medicine has resulted in more interest in antimicrobial properties of topical treatments (eg, mupirocin, fusidic acid). Topical products can deliver high drug concentrations to an affected area with little or no systemic absorption. Miconazole, an imidazole antifungal, has antibacterial properties against some bacteria.

In vitro susceptibility of 112 MRSP isolates, 53 methicillin-resistant S aureus (MRSA) isolates, and 37 methicillin-susceptible S pseudintermedius (MSSP) isolates to miconazole were assessed via agar dilution. The isolates, taken from 48 dogs with clinical infections and 154 dogs with nasal or rectal colonization, were not epidemiologically related. This study found low miconazole minimum inhibitory concentrations (MIC50) for MRSP (1–8 µg/mL), MSSP (1–4 µg/mL), and MRSA (1–8 µg/mL). There were no established breakpoints for miconazole and staphylococci; however, MIC50 levels were well below concentrations achievable with topical therapy (2% commercial products equate to 20,000 µg/mL), suggesting that miconazole may effectively treat superficial bacterial pyoderma in dogs.

Most intriguing is that miconazole, traditionally considered an antifungal agent, has antibacterial properties, making miconazole topical shampoo products an excellent first choice for dogs with skin infections exhibiting bacterial and yeast overgrowth and those with skin diseases predisposing them to Malassezia dermatitis. Topical treatments require frequent and thorough application to be effective, and coat hygiene is important in dogs with chronic skin disease. Professional grooming can be helpful before therapy, as medicated shampoos (often expensive) are not ideal grooming shampoos. Prewashing with grooming shampoo to remove gross debris and rinsing thoroughly before applying a medicated shampoo may be best. To avoid irritant reaction, clients can make a sudsy solution of the shampoo in a container and apply that to the hair coat; this makes it easier to rinse the pet and minimizes shampoo residue.—Karen A. Moriello, DVM, DACVD

In vitro miconazole susceptibility of meticillin-resistant Staphylococcus pseudintermedius and Staphylococcus aureus. Weese JS, Walker M, Lowe T. VET DERMATOL 23:400-e74, 2012.