Evaluation of residual antibacterial effects on canine skin surface and hair following treatment with five commercial mousse products against Staphylococcus pseudintermedius.

Background: Antibacterial effect studies of commercial antiseptics typically have evaluated hair and not the skin.

Objectives: To evaluate the antibacterial effects of mousse products on both canine skin and hair.

Animals: Fifteen short-haired and eight long-haired dogs without skin disease.

Materials and methods: Five mousses were applied once: (1) 2% chlorhexidine and 2% miconazole; (2) 0.05% phytosphingosine; (3) 2% salicylic acid and 10% ethyl lactate; (4) 3% chlorhexidine and 0.5% climbazole; and (5) 2% chlorhexidine and 1% ketoconazole. Skin swabs and hair were collected from application sites before treatment, and at 1 h and at Day (D)2, D4, D8, D10 and D14 post-treatment. Skin swabs and hair were placed on Mueller-Hinton plates inoculated with Staphylococcus pseudintermedius inoculum suspension. Inhibition zones were measured after incubation.

Results: Inhibition was not noted with mousses 2 and 3. In mousse 5, inhibition zone sizes produced by swabs from long- and short-haired dogs were not significantly different (p = 0.105), and all swabs and hair produced inhibition until D14, regardless of hair length. By contrast, in mousse 1, inhibition zones produced by swabs from long-haired dogs were smaller than those from short-haired dogs (p < 0.001), and swabs from long-haired dogs produced a shorter duration of bacterial inhibition than hair.

Conclusions and clinical relevance: The antibacterial effects of mousse 5 were not affected by hair length. Hair may be acceptable for evaluating effects on the skin in short-haired dogs. However, long hair may interfere with product distribution and duration of bacterial inhibition. Therefore, the evaluation of hair alone may overestimate clinically relevant antibacterial effects.